## From European Space Agency [Agence spatiale européenne] [Europäische Weltraumorganisation](EU) via Science Alert (US) : “Hubble Captures a Stunning ‘Einstein Ring’ Magnifying The Depths of The Universe”

From European Space Agency [Agence spatiale européenne] [Europäische Weltraumorganisation](EU)

via

20 AUGUST 2021
MICHELLE STARR

Credit: T. Treu NASA/ESA Hubble; Acknowledgment: J. Schmidt.

Gravity is the weird, mysterious glue that binds the Universe together, but that’s not the limit of its charms. We can also leverage the way it warps space-time to see distant objects that would be otherwise much more difficult to make out.

This is called gravitational lensing, an effect predicted by Einstein, and it’s beautifully illustrated in a new release from the Hubble Space Telescope.

In the center in the image (below) is a shiny, near-perfect ring with what appear to be four bright spots threaded along it, looping around two more points with a golden glow.

Credit: T. Treu NASA/ESA Hubble; Acknowledgment: J. Schmidt.

This is called an Einstein ring, and those bright dots are not six galaxies, but three: the two in the middle of the ring, and one quasar behind it, its light distorted and magnified as it passes through the gravitational field of the two foreground galaxies.

Because the mass of the two foreground galaxies is so high, this causes a gravitational curvature of space-time around the pair. Any light that then travels through this space-time follows this curvature and enters our telescopes smeared and distorted – but also magnified.

Illustration of gravitational lensing. (NASA/ESA & L. Calçada)

This, as it turns out, is a really useful tool for probing both the far and near reaches of the Universe. Anything with enough mass can act as a gravitational lens. That can mean one or two galaxies, as we see here, or even huge galaxy clusters, which produce a wonderful mess of smears of light from the many objects behind them.

Astronomers peering into deep space can reconstruct these smears and replicated images to see in much finer detail the distant galaxies thus lensed. But that’s not all gravitational lensing can do. The strength of a lens depends on the curvature of the gravitational field, which is directly related to the mass it’s curving around.

So gravitational lenses can allow us to weigh galaxies and galaxy clusters, which in turn can then help us find and map dark matter – the mysterious, invisible source of mass that generates additional gravity that can’t be explained by the stuff in the Universe we can actually detect.

Detecting Black Holes with Gravitational Microlensing.
This animation illustrates the concept of gravitational microlensing with a black hole. When the black hole appears to pass nearly in front of a background star, the light rays of the source star become bent due to the warped space-time around the foreground black hole. It becomes a virtual magnifying glass, amplifying the brightness of the distant background star. Unlike when a star or planet is the lensing object, black holes warp space-time so much that it noticeably alters the distant star’s apparent location in the sky.

The larger animation shows the brightening and splitting of the image during microlensing. The inset shows the shift of the image caused by a black hole lens. The two images caused by lensing are too close to be spatially resolved, but changing brightness of the two images produce a shift in the position of the source. To illustrate the shift, the inset only shows how the position of the source changes without showing the brightening.

Video credit: NASA’s Goddard Space Flight Center/Conceptual Image Lab
Ashley Balzer (GSFC Interns): Lead Science Writer

This video, along with other supporting visualizations, can be downloaded from NASA Goddard’s Scientific Visualization Studio at: https://svs.gsfc.nasa.gov/20315

A bit closer to home, gravitational lensing – or microlensing, to be more precise – can help us find objects within the Milky Way that would be too dark for us to see otherwise, such as stellar-mass black holes.

And it gets smaller. Astronomers have managed to detect rogue exoplanets – those unattached from a host star, wandering the galaxy, cold and alone – from the magnification that occurs when such exoplanets pass between us and distant stars. And they’ve even used gravitational microlensing to detect exoplanets in other galaxies.

It’s pretty wild what the Universe has up its gravitational sleeves.

You can download a wallpaper-sized version of the above image on ESA’s website.

Stem Education Coalition

European Space Agency [Agence spatiale européenne][Europäische Weltraumorganisation](EU), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC (NL) in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

ESA’s space flight programme includes human spaceflight (mainly through participation in the International Space Station program); the launch and operation of uncrewed exploration missions to other planets and the Moon; Earth observation, science and telecommunication; designing launch vehicles; and maintaining a major spaceport, the The Guiana Space Centre [Centre Spatial Guyanais; CSG also called Europe’s Spaceport) at Kourou, French Guiana. The main European launch vehicle Ariane 5 is operated through Arianespace with ESA sharing in the costs of launching and further developing this launch vehicle. The agency is also working with NASA to manufacture the Orion Spacecraft service module that will fly on the Space Launch System.

The agency’s facilities are distributed among the following centres:

ESA European Space Research and Technology Centre (ESTEC) (NL)in Noordwijk, Netherlands;
ESA Centre for Earth Observation [ESRIN] (IT) in Frascati, Italy;
ESA Mission Control ESA European Space Operations Center [ESOC](DE) is in Darmstadt, Germany;
ESA -European Astronaut Centre [EAC] trains astronauts for future missions is situated in Cologne, Germany;
European Centre for Space Applications and Telecommunications (ECSAT) (UK), a research institute created in 2009, is located in Harwell, England;
ESA – European Space Astronomy Centre [ESAC] (ES) is located in Villanueva de la Cañada, Madrid, Spain.
European Space Agency Science Programme is a long-term programme of space science and space exploration missions.

Foundation

After World War II, many European scientists left Western Europe in order to work with the United States. Although the 1950s boom made it possible for Western European countries to invest in research and specifically in space-related activities, Western European scientists realized solely national projects would not be able to compete with the two main superpowers. In 1958, only months after the Sputnik shock, Edoardo Amaldi (Italy) and Pierre Auger (France), two prominent members of the Western European scientific community, met to discuss the foundation of a common Western European space agency. The meeting was attended by scientific representatives from eight countries, including Harrie Massey (United Kingdom).

The Western European nations decided to have two agencies: one concerned with developing a launch system, ELDO (European Launch Development Organization), and the other the precursor of the European Space Agency, ESRO (European Space Research Organisation). The latter was established on 20 March 1964 by an agreement signed on 14 June 1962. From 1968 to 1972, ESRO launched seven research satellites.

ESA in its current form was founded with the ESA Convention in 1975, when ESRO was merged with ELDO. ESA had ten founding member states: Belgium, Denmark, France, West Germany, Italy, the Netherlands, Spain, Sweden, Switzerland, and the United Kingdom. These signed the ESA Convention in 1975 and deposited the instruments of ratification by 1980, when the convention came into force. During this interval the agency functioned in a de facto fashion. ESA launched its first major scientific mission in 1975, Cos-B, a space probe monitoring gamma-ray emissions in the universe, which was first worked on by ESRO.

Later activities

ESA collaborated with National Aeronautics Space Agency on the International Ultraviolet Explorer (IUE), the world’s first high-orbit telescope, which was launched in 1978 and operated successfully for 18 years.

A number of successful Earth-orbit projects followed, and in 1986 ESA began Giotto, its first deep-space mission, to study the comets Halley and Grigg–Skjellerup. Hipparcos, a star-mapping mission, was launched in 1989 and in the 1990s SOHO, Ulysses and the Hubble Space Telescope were all jointly carried out with NASA. Later scientific missions in cooperation with NASA include the Cassini–Huygens space probe, to which ESA contributed by building the Titan landing module Huygens.

As the successor of ELDO, ESA has also constructed rockets for scientific and commercial payloads. Ariane 1, launched in 1979, carried mostly commercial payloads into orbit from 1984 onward. The next two versions of the Ariane rocket were intermediate stages in the development of a more advanced launch system, the Ariane 4, which operated between 1988 and 2003 and established ESA as the world leader in commercial space launches in the 1990s. Although the succeeding Ariane 5 experienced a failure on its first flight, it has since firmly established itself within the heavily competitive commercial space launch market with 82 successful launches until 2018. The successor launch vehicle of Ariane 5, the Ariane 6, is under development and is envisioned to enter service in the 2020s.

The beginning of the new millennium saw ESA become, along with agencies like National Aeronautics Space Agency(US), Japan Aerospace Exploration Agency, Indian Space Research Organisation, the Canadian Space Agency(CA) and Roscosmos(RU), one of the major participants in scientific space research. Although ESA had relied on co-operation with NASA in previous decades, especially the 1990s, changed circumstances (such as tough legal restrictions on information sharing by the United States military) led to decisions to rely more on itself and on co-operation with Russia. A 2011 press issue thus stated:

“Russia is ESA’s first partner in its efforts to ensure long-term access to space. There is a framework agreement between ESA and the government of the Russian Federation on cooperation and partnership in the exploration and use of outer space for peaceful purposes, and cooperation is already underway in two different areas of launcher activity that will bring benefits to both partners.”

Notable ESA programmes include SMART-1, a probe testing cutting-edge space propulsion technology, the Mars Express and Venus Express missions, as well as the development of the Ariane 5 rocket and its role in the ISS partnership. ESA maintains its scientific and research projects mainly for astronomy-space missions such as Corot, launched on 27 December 2006, a milestone in the search for exoplanets.

On 21 January 2019, ArianeGroup and Arianespace announced a one-year contract with ESA to study and prepare for a mission to mine the Moon for lunar regolith.

Mission

The treaty establishing the European Space Agency reads:

The purpose of the Agency shall be to provide for and to promote, for exclusively peaceful purposes, cooperation among European States in space research and technology and their space applications, with a view to their being used for scientific purposes and for operational space applications systems…

ESA is responsible for setting a unified space and related industrial policy, recommending space objectives to the member states, and integrating national programs like satellite development, into the European program as much as possible.

Jean-Jacques Dordain – ESA’s Director General (2003–2015) – outlined the European Space Agency’s mission in a 2003 interview:

“Today space activities have pursued the benefit of citizens, and citizens are asking for a better quality of life on Earth. They want greater security and economic wealth, but they also want to pursue their dreams, to increase their knowledge, and they want younger people to be attracted to the pursuit of science and technology. I think that space can do all of this: it can produce a higher quality of life, better security, more economic wealth, and also fulfill our citizens’ dreams and thirst for knowledge, and attract the young generation. This is the reason space exploration is an integral part of overall space activities. It has always been so, and it will be even more important in the future.”

Activities

According to the ESA website, the activities are:

Observing the Earth
Human Spaceflight
Launchers
Space Science
Space Engineering & Technology
Operations
Telecommunications & Integrated Applications
Preparing for the Future
Space for Climate

Programmes

Mandatory

Every member country must contribute to these programmes:

Technology Development Element Programme
Science Core Technology Programme
General Study Programme
European Component Initiative

Optional

Depending on their individual choices the countries can contribute to the following programmes, listed according to:

Launchers
Earth Observation
Human Spaceflight and Exploration
Telecommunications
Space Situational Awareness
Technology

ESA_LAB@

ESA has formed partnerships with universities. ESA_LAB@ refers to research laboratories at universities. Currently there are ESA_LAB@

Membership and contribution to ESA

By 2015, ESA was an intergovernmental organisation of 22 member states. Member states participate to varying degrees in the mandatory (25% of total expenditures in 2008) and optional space programmes (75% of total expenditures in 2008). The 2008 budget amounted to €3.0 billion whilst the 2009 budget amounted to €3.6 billion. The total budget amounted to about €3.7 billion in 2010, €3.99 billion in 2011, €4.02 billion in 2012, €4.28 billion in 2013, €4.10 billion in 2014 and €4.33 billion in 2015. English is the main language within ESA. Additionally, official documents are also provided in German and documents regarding the Spacelab are also provided in Italian. If found appropriate, the agency may conduct its correspondence in any language of a member state.

Non-full member states
Slovenia
Since 2016, Slovenia has been an associated member of the ESA.

Latvia
Latvia became the second current associated member on 30 June 2020, when the Association Agreement was signed by ESA Director Jan Wörner and the Minister of Education and Science of Latvia, Ilga Šuplinska in Riga. The Saeima ratified it on July 27. Previously associated members were Austria, Norway and Finland, all of which later joined ESA as full members.

Since 1 January 1979, Canada has had the special status of a Cooperating State within ESA. By virtue of this accord, the Canadian Space Agency takes part in ESA’s deliberative bodies and decision-making and also in ESA’s programmes and activities. Canadian firms can bid for and receive contracts to work on programmes. The accord has a provision ensuring a fair industrial return to Canada. The most recent Cooperation Agreement was signed on 15 December 2010 with a term extending to 2020. For 2014, Canada’s annual assessed contribution to the ESA general budget was €6,059,449 (CAD$8,559,050). For 2017, Canada has increased its annual contribution to €21,600,000 (CAD$30,000,000).

Enlargement

After the decision of the ESA Council of 21/22 March 2001, the procedure for accession of the European states was detailed as described the document titled The Plan for European Co-operating States (PECS). Nations that want to become a full member of ESA do so in 3 stages. First a Cooperation Agreement is signed between the country and ESA. In this stage, the country has very limited financial responsibilities. If a country wants to co-operate more fully with ESA, it signs a European Cooperating State (ECS) Agreement. The ECS Agreement makes companies based in the country eligible for participation in ESA procurements. The country can also participate in all ESA programmes, except for the Basic Technology Research Programme. While the financial contribution of the country concerned increases, it is still much lower than that of a full member state. The agreement is normally followed by a Plan For European Cooperating State (or PECS Charter). This is a 5-year programme of basic research and development activities aimed at improving the nation’s space industry capacity. At the end of the 5-year period, the country can either begin negotiations to become a full member state or an associated state or sign a new PECS Charter.

During the Ministerial Meeting in December 2014, ESA ministers approved a resolution calling for discussions to begin with Israel, Australia and South Africa on future association agreements. The ministers noted that “concrete cooperation is at an advanced stage” with these nations and that “prospects for mutual benefits are existing”.

A separate space exploration strategy resolution calls for further co-operation with the United States, Russia and China on “LEO exploration, including a continuation of ISS cooperation and the development of a robust plan for the coordinated use of space transportation vehicles and systems for exploration purposes, participation in robotic missions for the exploration of the Moon, the robotic exploration of Mars, leading to a broad Mars Sample Return mission in which Europe should be involved as a full partner, and human missions beyond LEO in the longer term.”

Relationship with the European Union

The political perspective of the European Union (EU) was to make ESA an agency of the EU by 2014, although this date was not met. The EU member states provide most of ESA’s funding, and they are all either full ESA members or observers.

History

At the time ESA was formed, its main goals did not encompass human space flight; rather it considered itself to be primarily a scientific research organisation for uncrewed space exploration in contrast to its American and Soviet counterparts. It is therefore not surprising that the first non-Soviet European in space was not an ESA astronaut on a European space craft; it was Czechoslovak Vladimír Remek who in 1978 became the first non-Soviet or American in space (the first man in space being Yuri Gagarin of the Soviet Union) – on a Soviet Soyuz spacecraft, followed by the Pole Mirosław Hermaszewski and East German Sigmund Jähn in the same year. This Soviet co-operation programme, known as Intercosmos, primarily involved the participation of Eastern bloc countries. In 1982, however, Jean-Loup Chrétien became the first non-Communist Bloc astronaut on a flight to the Soviet Salyut 7 space station.

Because Chrétien did not officially fly into space as an ESA astronaut, but rather as a member of the French CNES astronaut corps, the German Ulf Merbold is considered the first ESA astronaut to fly into space. He participated in the STS-9 Space Shuttle mission that included the first use of the European-built Spacelab in 1983. STS-9 marked the beginning of an extensive ESA/NASA joint partnership that included dozens of space flights of ESA astronauts in the following years. Some of these missions with Spacelab were fully funded and organizationally and scientifically controlled by ESA (such as two missions by Germany and one by Japan) with European astronauts as full crew members rather than guests on board. Beside paying for Spacelab flights and seats on the shuttles, ESA continued its human space flight co-operation with the Soviet Union and later Russia, including numerous visits to Mir.

During the latter half of the 1980s, European human space flights changed from being the exception to routine and therefore, in 1990, the European Astronaut Centre in Cologne, Germany was established. It selects and trains prospective astronauts and is responsible for the co-ordination with international partners, especially with regard to the International Space Station. As of 2006, the ESA astronaut corps officially included twelve members, including nationals from most large European countries except the United Kingdom.

In the summer of 2008, ESA started to recruit new astronauts so that final selection would be due in spring 2009. Almost 10,000 people registered as astronaut candidates before registration ended in June 2008. 8,413 fulfilled the initial application criteria. Of the applicants, 918 were chosen to take part in the first stage of psychological testing, which narrowed down the field to 192. After two-stage psychological tests and medical evaluation in early 2009, as well as formal interviews, six new members of the European Astronaut Corps were selected – five men and one woman.

Cooperation with other countries and organisations

ESA has signed co-operation agreements with the following states that currently neither plan to integrate as tightly with ESA institutions as Canada, nor envision future membership of ESA: Argentina, Brazil, China, India (for the Chandrayan mission), Russia and Turkey.

Additionally, ESA has joint projects with the European Union, NASA of the United States and is participating in the International Space Station together with the United States (NASA), Russia and Japan (JAXA).

European Union
ESA and EU member states
ESA-only members
EU-only members

ESA is not an agency or body of the European Union (EU), and has non-EU countries (Norway, Switzerland, and the United Kingdom) as members. There are however ties between the two, with various agreements in place and being worked on, to define the legal status of ESA with regard to the EU.

There are common goals between ESA and the EU. ESA has an EU liaison office in Brussels. On certain projects, the EU and ESA co-operate, such as the upcoming Galileo satellite navigation system. Space policy has since December 2009 been an area for voting in the European Council. Under the European Space Policy of 2007, the EU, ESA and its Member States committed themselves to increasing co-ordination of their activities and programmes and to organising their respective roles relating to space.

The Lisbon Treaty of 2009 reinforces the case for space in Europe and strengthens the role of ESA as an R&D space agency. Article 189 of the Treaty gives the EU a mandate to elaborate a European space policy and take related measures, and provides that the EU should establish appropriate relations with ESA.

Former Italian astronaut Umberto Guidoni, during his tenure as a Member of the European Parliament from 2004 to 2009, stressed the importance of the European Union as a driving force for space exploration, “…since other players are coming up such as India and China it is becoming ever more important that Europeans can have an independent access to space. We have to invest more into space research and technology in order to have an industry capable of competing with other international players.”

The first EU-ESA International Conference on Human Space Exploration took place in Prague on 22 and 23 October 2009. A road map which would lead to a common vision and strategic planning in the area of space exploration was discussed. Ministers from all 29 EU and ESA members as well as members of parliament were in attendance.

National space organisations of member states:

The Centre National d’Études Spatiales(FR) (CNES) (National Centre for Space Study) is the French government space agency (administratively, a “public establishment of industrial and commercial character”). Its headquarters are in central Paris. CNES is the main participant on the Ariane project. Indeed, CNES designed and tested all Ariane family rockets (mainly from its centre in Évry near Paris)
The UK Space Agency is a partnership of the UK government departments which are active in space. Through the UK Space Agency, the partners provide delegates to represent the UK on the various ESA governing bodies. Each partner funds its own programme.
The Italian Space Agency A.S.I. – Agenzia Spaziale Italiana was founded in 1988 to promote, co-ordinate and conduct space activities in Italy. Operating under the Ministry of the Universities and of Scientific and Technological Research, the agency cooperates with numerous entities active in space technology and with the president of the Council of Ministers. Internationally, the ASI provides Italy’s delegation to the Council of the European Space Agency and to its subordinate bodies.
The German Aerospace Center (DLR)[Deutsches Zentrum für Luft- und Raumfahrt e. V.] is the national research centre for aviation and space flight of the Federal Republic of Germany and of other member states in the Helmholtz Association. Its extensive research and development projects are included in national and international cooperative programmes. In addition to its research projects, the centre is the assigned space agency of Germany bestowing headquarters of German space flight activities and its associates.
The Instituto Nacional de Técnica Aeroespacial (INTA)(ES) (National Institute for Aerospace Technique) is a Public Research Organization specialised in aerospace research and technology development in Spain. Among other functions, it serves as a platform for space research and acts as a significant testing facility for the aeronautic and space sector in the country.

National Aeronautics Space Agency(US)

ESA has a long history of collaboration with NASA. Since ESA’s astronaut corps was formed, the Space Shuttle has been the primary launch vehicle used by ESA’s astronauts to get into space through partnership programmes with NASA. In the 1980s and 1990s, the Spacelab programme was an ESA-NASA joint research programme that had ESA develop and manufacture orbital labs for the Space Shuttle for several flights on which ESA participate with astronauts in experiments.

In robotic science mission and exploration missions, NASA has been ESA’s main partner. Cassini–Huygens was a joint NASA-ESA mission, along with the Infrared Space Observatory, INTEGRAL, SOHO, and others.

Also, the Hubble Space Telescope is a joint project of NASA and ESA.

Future ESA-NASA joint projects include the James Webb Space Telescope and the proposed Laser Interferometer Space Antenna.

NASA has committed to provide support to ESA’s proposed MarcoPolo-R mission to return an asteroid sample to Earth for further analysis. NASA and ESA will also likely join together for a Mars Sample Return Mission. In October 2020 the ESA entered into a memorandum of understanding (MOU) with NASA to work together on the Artemis program, which will provide an orbiting lunar gateway and also accomplish the first manned lunar landing in 50 years, whose team will include the first woman on the Moon.

Cooperation with other space agencies

Since China has started to invest more money into space activities, the Chinese Space Agency(CN) has sought international partnerships. ESA is, beside the Russian Space Agency, one of its most important partners. Two space agencies cooperated in the development of the Double Star Mission. In 2017, ESA sent two astronauts to China for two weeks sea survival training with Chinese astronauts in Yantai, Shandong.

ESA entered into a major joint venture with Russia in the form of the CSTS, the preparation of French Guiana spaceport for launches of Soyuz-2 rockets and other projects. With India, ESA agreed to send instruments into space aboard the ISRO’s Chandrayaan-1 in 2008. ESA is also co-operating with Japan, the most notable current project in collaboration with JAXA is the BepiColombo mission to Mercury.

Speaking to reporters at an air show near Moscow in August 2011, ESA head Jean-Jacques Dordain said ESA and Russia’s Roskosmos space agency would “carry out the first flight to Mars together.”

## From University of Chicago: “UChicago undergrads discover bright lensed galaxy in the early universe”

From University of Chicago

Jan 13, 2021
Katrina Miller

A class of undergraduate astrophysics students at the University of Chicago helped discover a galaxy that dates back to a time when the universe was only 1.2 billion years old, about one-tenth of its current age.

Class turned research collaboration uses ‘nature’s telescope’ to reach across cosmic time.

The night sky is a natural time machine, used by cosmologists to explore the origins and evolution of the universe. Reaching into the depths of the past, a class of undergraduate students at the University of Chicago sought to do the same—and uncovered an extraordinarily distant galaxy in the early cosmos.

Light emitted from faraway celestial objects takes a long time to reach Earth-side observers. That means the stars and galaxies we see in the sky appear to us as they would have existed millions, or even billions, of years ago.

The discovered galaxy’s light comes from a time when the universe was only 1.2 billion years old, about one-tenth of its current age. By this point, the young galaxy had already accumulated a mass impressively comparable to the present-day version of our home galaxy, the Milky Way.

“This galaxy that we’ve observed, by looking out and back into the past, is already grown up. It’s already formed almost a Milky Way’s worth of stars,” said Michael Gladders, a professor in UChicago’s astronomy and astrophysics department. “It’s quite mature, but at a much earlier stage in the Universe.”

The discovery was a climactic milestone in the first iteration of a field course developed for the new astrophysics major offered by UChicago. Students in the two-quarter class formed a new research collaboration, COOL-LAMPS, and surveyed public imaging databases in search of lensed galaxies. The remarkable find was confirmed by observations from ground-based instruments: the Magellan Telescopes in Chile and the Gemini North telescope in Hawaii.

Carnegie 6.5 meter Magellan Baade and Clay Telescopes located at Carnegie’s Las Campanas Observatory, Chile. over 2,500 m (8,200 ft) high.

NSF’s NOIRLab Frederick C Gillett Gemini North Telescope Maunakea, Hawaii, USA, Altitude 4,213 m (13,822 ft).

‘Nature’s telescope’

A lensed galaxy is one whose emitted light has been bent by the gravity of a massive object lying between the galaxy and the point of observation. This effect, known as gravitational lensing, creates a distorted, arc-like image of the galaxy with an intensely magnified brightness.

Gravitational Lensing NASA/ESA.

COOL-LAMPS I. An Extraordinarily Bright Lensed Galaxy at Redshift 5.04∗
An effect called gravitational lensing creates a distorted, arc-like image of a galaxy behind it that may not have been visible otherwise-such as this extremely ancient galaxy. Credit: Khullar et al.

Gladders, who taught the field course in the first half of 2020, calls gravitational lensing ‘nature’s telescope.’ “It’s a rare, peculiar form of focusing and magnification that allows us to study galaxies with much greater detail than we ever normally could,” he said.

Light from the discovered galaxy was so strongly magnified by a cluster of other galaxies in its foreground that it rivaled images of the sky taken from space.

“This was a ground-based telescope taking data of this absolutely beautiful arc,” said Gourav Khullar, a UChicago PhD candidate who served as teaching assistant for the field course and is first author of the paper describing the findings. “It’s approximately a hundred times brighter than classical images of similarly distant galaxies from the Hubble Space Telescope!”

A comprehensive study of the stellar populations of this galaxy, undertaken by the student collaborators, concluded in the realization that this was the brightest lensed galaxy ever observed in this time period of the early universe.

Without gravitational lensing, though, the distant galaxy would appear much dimmer, if visible at all.

“The arc has been magnified by the intermediate lens in such a way that it’s extremely bright,” said Khullar. “But an un-lensed version of the galaxy wouldn’t look like this; it would be much fainter and not at all detectable by current ground-based facilities.”

Pushing through the pandemic

The field course was designed to provide astrophysics majors with a real-life, cutting-edge research opportunity. Originally modest in ambition, Gladders convinced the department and the College to invest in a complete field experience, including a visit to the Magellan Telescopes to participate in astronomical observing time over spring break.

But the coronavirus pandemic thwarted those plans, ripping away what was intended to be the core experience of the class.

“Everything was booked,” said Gladders. “I’d already arranged trips to other observatory sites, construction sites to see telescopes that were currently being built, and to see Chile itself.”

In the midst of dark times, the COOL-LAMPS students pushed on with the scan of public sky data, eventually reaching their illuminating galactic discovery.

“For me, it was a shock that we had found something so important,” said Emily Sisco, a fourth-year astrophysics major who participated in the field course during the last academic year. “All of the work we had been doing was leading up to that moment, but I was still shocked!”

Intriguing first results have encouraged the COOL-LAMPS collaboration to pursue observation time for a second wave of study. Plans are set to observe the galaxy using ground-based telescopes in New Mexico and Europe, as well as two of NASA’s orbiting space telescopes, Hubble and the Chandra X-ray Observatory.

NASA/ESA Hubble Telescope.

NASA Chandra X-ray Space Telescope

“With higher resolution imaging from space, astronomers will be able to resolve the structure of this galaxy,” said Ezra Sukay, who joined the COOL-LAMPS collaboration as a third-year student in the College. “This will reveal details about star formation in very massive galaxies early in the Universe.”

Gladders expected the class to be successful in some way, but did not anticipate a galaxy so exceptionally bright, far back in time, or mature as what was discovered. “It’s just absolutely fantastic,” he said. “I’m so proud of them—they’ve done really great work.”

In January, Gladders will begin teaching a second version of the field course, adding new students to COOL-LAMPS who will continue to probe the formation and evolution of galaxies across cosmic time.

“One of the great goals in studying the cosmos is answering the fundamental question of where we come from,” said Gladders. “Us as a species, but also the planet we live on, the solar system that planet is in, and the galaxy that our solar system is in.

“We’re addressing this deep yearning to understand where it all comes from and ultimately, how do we fit in?”

COOL-LAMPS is short for ChicagO Optically-selected strong Lenses – Located At the Margins of Public Surveys. The UChicago undergraduate authors of the paper are Katya Gozman, Jason J. Lin, Michael N. Martinez, Owen S. Matthews Acuña, Elisabeth Medina, Kaiya Merz, Jorge A. Sanchez, Emily E. Sisco, Daniel J. Kavin Stein, Ezra O. Sukay and Kiyan Tavangar.

The study also includes co-authors from the University of Michigan, the University of Cincinnati, Argonne National Laboratory, Harvard University, the University of Oslo, the NASA Goddard Space Flight Center and the Harvard & Smithsonian Center for Astrophysics.

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One of the world’s premier academic and research institutions, the University of Chicago has driven new ways of thinking since our 1890 founding. Today, UChicago is an intellectual destination that draws inspired scholars to our Hyde Park and international campuses, keeping UChicago at the nexus of ideas that challenge and change the world.

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In all we do, we are driven to dig deeper, push further, and ask bigger questions—and to leverage our knowledge to enrich all human life. Our diverse and creative students and alumni drive innovation, lead international conversations, and make masterpieces. Alumni and faculty, lecturers and postdocs go on to become Nobel laureates, CEOs, university presidents, attorneys general, literary giants, and astronauts.

## From NASA/ESA Hubble Telescope: “Rings of Relativity”

NASA/ESA Hubble Telescope

From NASA/ESA Hubble Telescope

The narrow galaxy elegantly curving around its spherical companion in this image is a fantastic example of a truly strange and very rare phenomenon. This image, taken with the NASA/ESA Hubble Space Telescope, depicts GAL-CLUS-022058s, located in the southern hemisphere constellation of Fornax (The Furnace). GAL-CLUS-022058s is the largest and one of the most complete Einstein rings ever discovered in our Universe. The object has been nicknamed by the Principal Investigator and his team who are studying this Einstein ring as the “Molten Ring”, which alludes to its appearance and host constellation. Credit: NASA/ESA Hubble, S. Jha. Acknowledgement: L. Shatz.

First theorised to exist by Einstein in his general theory of relativity, this object’s unusual shape can be explained by a process called gravitational lensing, which causes light shining from far away to be bent and pulled by the gravity of an object between its source and the observer. In this case, the light from the background galaxy has been distorted into the curve we see by the gravity of the galaxy cluster sitting in front of it. The near exact alignment of the background galaxy with the central elliptical galaxy of the cluster, seen in the middle of this image, has warped and magnified the image of the background galaxy around itself into an almost perfect ring. The gravity from other galaxies in the cluster is soon to cause additional distortions.

The “Cosmic Horseshoe” is another example of an Einstein Ring. Credit:NASA/ESA Hubble.

Objects like these are the ideal laboratory in which to research galaxies too faint and distant to otherwise see.

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Major Instrumentation

Wide Field Camera 3 [WFC3]

NASA/ESA Hubble WFC3

NASA Hubble Advanced Camera for Surveys.

Cosmic Origins Spectrograph [COS]

NASA Hubble Cosmic Origins Spectrograph.

The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

## From AAS NOVA: “Nugget Galaxies Cross in the Sky”

From AAS NOVA

9 December 2020
Susanna Kohler

The iconic Einstein Cross, the quadruply lensed quasar Q2237+030, is seen in this Hubble image. A new study has found two additional Einstein Crosses created by the lensing of compact galaxies. [NASA, ESA, and STScI]

Gravitational Lensing NASA/ESA.

Seeing quadruple? In a rare phenomenon, some distant objects can appear as four copies arranged in an “Einstein cross”. A new study has found two more of these unusual sights — with an unexpected twist.

Searching for Rare Crosses

Gravitational lensing [above]— the bending of light by the gravity of massive astronomical objects — can do some pretty strange things. One of lensing’s more striking creations is the Einstein cross, a configuration of four images of a distant, compact source created by the gravitational pull of a foreground object (which is usually visible in the center of the four images).

Diagram illustrating how light from a distant source can be bent by a foreground object to produce four identical images of the source. Credit: NASA/ESA/D. Player (STScI).

The iconic example of this phenomenon is the Einstein Cross, a gravitationally lensed object called QSO 2237+0305, seen in the cover image above. In this case, as with the majority of known Einstein crosses, the background source is a distant quasar — the small and incredibly bright nucleus of an active galaxy. But other sources can be lensed into Einstein crosses as well, under the right circumstances.

In a new study led by Nicola Napolitano (Sun Yat-sen University Zhuhai Campus, China), a team of scientists presents confirmation of two new Einstein crosses discovered within the 1,000 square degrees imaged in the Kilo-Degree Survey using the Very Large Telescope (VLT) in Chile.

ESO VLT at Cerro Paranal in the Atacama Desert, •ANTU (UT1; The Sun ), •KUEYEN (UT2; The Moon ), ;•MELIPAL (UT3; The Southern Cross ), and •YEPUN (UT4; Venus – as evening star). elevation 2,635 m (8,645 ft) from above Credit J.L. Dauvergne & G. Hüdepohl atacama photo.

Einstein crosses are unusual enough to begin with, but these two discoveries are especially rare: the lensed sources are not quasars. Instead, they’re entire galaxies.

Galaxies, but Bite-Size

When a distant galaxy is lensed by a foreground object, it’s commonly smeared out into an an arc or a ring; this is because galaxies are large, extended objects. But if a galaxy is compact enough, the entire galaxy can be lensed into quadruple images instead of a smeared-out ring. Such is the case with Napolitano and collaborators’ new discoveries, KIDS J232940-340922 and KIDS J122456+005048: they’re both quadruply lensed compact galaxies known as post-blue nuggets.

Detection and confirmation of the Einstein crosses, KIDS J232940-34092 (top two rows) and KIDS J122456+005048 (bottom two rows), via the KiDS survey and the MUSE integral field spectrograph on the VLT. Credit: Napolitano et al. 2020.

What’s a blue nugget? This adorable categorization applies to a type of galaxy found only in the early universe. Blue nuggets are extremely small, quite massive, and undergoing a violent burst of star formation that produces lots of large, bright, blue stars.

Blue nuggets are thought to be suddenly quenched — their star formation is cut off — early in their evolution. As their star population then evolves, these post-blue nuggets then transition into red nuggets, compact collections of red stars that are theorized to become the cores of today’s large elliptical galaxies.

A Bright Future

By spectroscopically following up their Einstein cross discoveries, Napolitano and collaborators show that the two sources are both very compact, massive galaxies with low specific star formation rates. Their properties are consistent with post-blue nuggets currently undergoing quenching — which means that these Einstein crosses are excellent sources to study to learn about galaxy evolution.

The authors predict that, with future observatories like the Vera Rubin Observatory, Euclid, or the China Space Station Telescope, we may be able to find many thousands of Einstein crosses like these. There’s a lot to learn ahead!

NOIRLab Vera C. Rubin Observatory Telescope currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes, altitude 2,715 m (8,907 ft).

ESA/Euclid spacecraft depiction

Chinese Space Station Telescope depiction.

Citation

“Discovery of Two Einstein Crosses from Massive Post-blue Nugget Galaxies at z > 1 in KiDS,” N. R. Napolitano et al 2020 ApJL 904 L31.

https://iopscience.iop.org/article/10.3847/2041-8213/abc95b

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AAS Mission and Vision Statement

The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

## From The University of Texas at Dallas: “Astrophysics Team Lights the Way for More Accurate Model of the Universe”

Oct. 14, 2020
Amanda Siegfried

Abell 370 is a galaxy cluster about 4 billion light-years away from Earth in which astronomers observe the phenomenon of gravitational lensing, the warping of space-time by the cluster’s gravitational field that distorts the light from galaxies lying far behind it. This manifests as arcs and streaks in the picture, which are the stretched images of background galaxies. Credit: NASA/STScI.

Light from distant galaxies reveals important information about the nature of the universe and allows scientists to develop high-precision models of the history, evolution and structure of the cosmos.

The gravity associated with massive pockets of dark matter that lie between Earth and these galaxies, however, plays havoc with those galactic light signals. Gravity distorts galaxies’ light — a process called gravitational lensing — and also slightly aligns the galaxies physically, resulting in additional gravitational lensing light signals that contaminate the true data.

In a study first published Aug. 5 in The Astrophysical Journal Letters, University of Texas at Dallas scientists demonstrated the first use of a method called self-calibration to remove contamination from gravitational lensing signals. The results should lead to more accurate cosmological models of the universe, said Dr. Mustapha Ishak-Boushaki, professor of physics in the School of Natural Sciences and Mathematics and the corresponding author of the study.

“The self-calibration method is something others proposed about 10 years ago; many thought it was just a theoretical method and moved away from it,” Ishak-Boushaki said. “But I intuitively felt the promise. After eight years of persistent investigation maturing the method itself, and then the last two years applying it to the data, it bore fruit with important consequences for cosmological studies.”

A Lens on the Universe

Gravitational lensing is one of the most promising methods in cosmology to provide information on the parameters that underlie the current model of the universe.

“It can help us map the distribution of dark matter and discover information about the structure of the universe. But the measurement of such cosmological parameters can be off by as much as 30% if we do not extract the contamination in the gravitational lensing signal,” Ishak-Boushaki said.

Due to the way distant galaxies form and the environment they form in, they are slightly physically aligned with the dark matter close to them. This intrinsic alignment generates additional spurious lensing signals, or a bias, which contaminate the data from the galaxies and thus skew the measurement of key cosmological parameters, including those that describe the amount of dark matter and dark energy in the universe and how fast galaxies move away from each other.

To complicate matters further, there are two types of intrinsic alignment that require different methods of mitigation. In their study, the research team used the self-calibration method to extract the nuisance signals from a type of alignment called intrinsic shape-gravitational shear, which is the most critical component.

“Our work significantly increases the chances of success to measure the properties of dark energy in an accurate way, which will allow us to understand what is causing cosmic acceleration,” Ishak-Boushaki said. “Another impact will be to determine accurately whether Einstein’s general theory of relativity holds at very large scales in the universe. These are very important questions.”

Impact on Cosmology

Several large scientific surveys aimed at better understanding the universe are in the works, and they will gather gravitational lensing data. These include the Vera C. Rubin Observatory, the European Space Agency’s Euclid mission and NASA’s Nancy Grace Roman Space Telescope.

NOIRLab Vera C. Rubin Observatory Telescope currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes, altitude 2,715 m (8,907 ft).

ESA/Euclid spacecraft depiction

NASA Nancy Grace Roman Space Telescope.

______________________________________________

“Our work significantly increases the chances of success to measure the properties of dark energy in an accurate way, which will allow us to understand what is causing cosmic acceleration. Another impact will be to determine accurately whether Einstein’s general theory of relativity holds at very large scales in the universe. These are very important questions.”

Dr. Mustapha Ishak-Boushaki, professor of physics in the School of Natural Sciences and Mathematics.
______________________________________________

“The big winner here will be these upcoming surveys of gravitational lensing. We will really be able to get the full potential from them to understand our universe,” said Ishak-Boushaki, who is a member and a convener of the LSST’s Dark Energy Science Collaboration.

The self-calibration method to remove contaminated signals was first proposed by Dr. Pengjie Zhang, a professor of astronomy at Shanghai Jiao Tong University (CN) and a co-author of the current study.

Ishak-Boushaki further developed the method and introduced it to the realm of cosmological observations, along with one of his former students, Michael Troxel MS’11, PhD’14, now an assistant professor of physics at Duke University. Since 2012 the research has been supported by two grants to Ishak-Boushaki from the National Science Foundation (NSF).

“Not everyone was sure that self-calibration would lead to such an important result. Some colleagues were encouraging; some were skeptical,” Ishak-Boushaki said. “I’ve learned that it pays not to give up. My intuition was that if it was done right, it would work, and I’m grateful to the NSF for seeing the promise of this work.”

Other study authors are UT Dallas physics doctoral student Eske Pedersen, lead author; and Ji Yao PhD’18, a fellow at Shanghai Jiao Tong University (CN).

The research was supported in part by the U.S. Department of Energy. The scientists also used the high-performance computing resources at the Texas Advanced Computing Center, an NSF-funded supercomputer center hosted by UT Austin.

TACC Maverick HP NVIDIA supercomputer

TACC Lonestar Cray XC40 supercomputer

Dell Poweredge U Texas Austin Stampede Supercomputer. Texas Advanced Computer Center 9.6 PF

TACC HPE Apollo 8000 Hikari supercomputer

TACC Ranch long-term mass data storage system

TACC DELL EMC Stampede2 supercomputer

TACC Frontera Dell EMC supercomputer fastest at any university

five-ways-keep-your-child-safe-school-shootings

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The University of Texas at Dallas is a Carnegie R1 classification (Doctoral Universities – Highest research activity) institution, located in a suburban setting 20 miles north of downtown Dallas. The University enrolls more than 27,600 students — 18,380 undergraduate and 9,250 graduate —and offers a broad array of bachelor’s, master’s, and doctoral degree programs.

Established by Eugene McDermott, J. Erik Jonsson and Cecil Green, the founders of Texas Instruments, UT Dallas is a young institution driven by the entrepreneurial spirit of its founders and their commitment to academic excellence. In 1969, the public research institution joined The University of Texas System and became The University of Texas at Dallas.

A high-energy, nimble, innovative institution, UT Dallas offers top-ranked science, engineering and business programs and has gained prominence for a breadth of educational paths from audiology to arts and technology. UT Dallas’ faculty includes a Nobel laureate, six members of the National Academies and more than 560 tenured and tenure-track professors.

## From astrobites: “Through the Lens: Milky Matter Magnifies Magellanic Motion”

From astrobites

Feb 22, 2020
Luna Zagorac

Title: First Results on Dark Matter Substructure from Astrometric Weak Lensing
Authors: Cristina Mondino, Anna-Maria Taki, Ken Van Tilburg, and Neal Weiner
First Author’s Institution: Center for Cosmology and Particle Physics, Department of Physics, New York University, New York, NY 10003, USA

Status: pre-published on arXiv

There is about five times more invisible Dark Matter than its luminous counterpart in the universe—but how do we go about detecting something that can’t be directly imaged?

Fritz Zwicky discovered Dark Matter when observing the movement of the Coma Cluster., Vera Rubin a Woman in STEM denied the Nobel, did most of the work on Dark Matter.

Fritz Zwicky from http:// palomarskies.blogspot.com

Coma cluster via NASA/ESA Hubble

Astronomer Vera Rubin at the Lowell Observatory in 1965, worked on Dark Matter (The Carnegie Institution for Science)

Vera Rubin measuring spectra, worked on Dark Matter (Emilio Segre Visual Archives AIP SPL)

Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970. https://home.dtm.ciw.edu

The LSST, or Large Synoptic Survey Telescope is to be named the Vera C. Rubin Observatory by an act of the U.S. Congress.

LSST telescope, The Vera C. Rubin Observatory currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

LSST Data Journey, Illustration by Sandbox Studio, Chicago with Ana Kova

Dark Matter Research

Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

Scientists studying the cosmic microwave background [CMB]hope to learn about more than just how the universe grew—it could also offer insight into dark matter, dark energy and the mass of the neutrino.

[caption id="attachment_73741" align="alignnone" width="632"] CMB per ESA/Planck

Dark matter cosmic web and the large-scale structure it forms The Millenium Simulation, V. Springel et al

Dark Matter Particle Explorer China

DEAP Dark Matter detector, The DEAP-3600, suspended in the SNOLAB deep in Sudbury’s Creighton Mine

LBNL LZ Dark Matter project at SURF, Lead, SD, USA

Inside the ADMX experiment hall at the University of Washington Credit Mark Stone U. of Washington. Axion Dark Matter Experiment

One way is to look for the gravitational effects of dark matter clumps on images of normal matter along the same line of sight. This type of effect is called gravitational lensing.

Gravitational Lensing NASA/ESA

In today’s paper, the authors specifically look for the effects of weak lensing from low-mass structures consisting entirely of dark matter.

Weak gravitational lensing NASA/ESA Hubble

The foreground dark matter structure creates a lens that bends the light coming towards an observer from some background luminous source. Unlike strong lensing, weak lensing doesn’t impact a single background source, but instead serves to preferentially align several background sources along some field. For more information on different types of lensing and how they work, check out this bite.

Why Use Weak Lensing?

Alignments of foreground and background sources that lead to weak lensing are much more common than those leading to strong lensing. Because low-mass dark matter structures are predicted to exist in the Milky Way, they should be both common in observational data sets and detectable through microlensing signatures. Furthermore, because such structures are completely devoid of normal matter, they pose a “pristine testing ground” for probing the microphysics of dark matter without the interference of normal, luminous matter.

How to Look For Weak Lensing?

Figure 1: Diagram of gravitational lensing of sources i by lens l. Note the blue monopole pattern of the angular displacement \Delta \theta_{il}. This is not constant in time, leading to the red dipole pattern lensing corrections \Delta \mu_{il} to the sources’ proper motions \mu_i. This dipole pattern is universal, and is what the authors look for. Figure 1 in the paper.

The authors use a template approach, which is similar to the one used when detecting astrophysical signals with LIGO. Figure 1 shows the dipole pattern of velocity corrections of background stars which stems from weak lensing. The exact shape and size of the template depend on the angular position \mathbf{\theta}_t, angular scale \beta_t, and effective lens velocity direction \hat{\mathbf{v}}_{t} of the dark matter lens. The details of the matched filter to the lens-induced velocity vector profile also include information about the density profile of the dark matter lens. This means that finding the correct shape of velocity corrections in the data and comparing its magnitude with the theoretical template model can inform the size, position, and density profile (and subsequently, mass) of the dark matter lens.

Where to Look For Weak Lensing?

The researchers looked to the Milky Way to provide the dark matter lenses, and extra-galactically to the Large and Small Magellanic Clouds (LMC, SMC) to provide the luminous matter to be lensed.

Milky Way NASA/JPL-Caltech /ESO R. Hurt. The bar is visible in this image

Large Magellanic Cloud. Adrian Pingstone December 2003

Small Magellanic Cloud. NASA/ESA Hubble and ESO/Digitized Sky Survey 2

They used the second data release from Gaia and chose the LMC and SMC data for their large stellar number densities and low proper motion dispersions, both intrinsic and instrumental.

ESA/GAIA satellite

This left the authors with a high signal-to-noise ratio, thus best equipping them to look for signatures of weak lensing.

In order to look for the tell-tale dipole template motion, the authors cleaned the data up a bit. First, they subtracted overdense stellar clusters, as they generally move coherently and independently from the bulk stars in the Magellanic Clouds. Additionally, they subtracted the large-scale proper motion of the clouds themselves. Finally, they removed stars which are in the line of sight, but not bound to the clouds.

Figure 2: Average stellar proper motion per 0.03° pixels in the RA (left) and DEC (right) across the Large Magellanic Cloud. The top panel shows the proper motion in the original Gaia data sample after the removal of dense clusters; the bottom shows it after further background motion subtraction and removal of outlier stars. Figure 7 in the paper.

What did the authors find?

In performing their analysis, the authors produced exclusions on the fraction of dark matter present in lensing sources as a function of lens mass (see Figure 3). They also noted that the current analysis is statistics-limited, with their figure of merit being largest for relatively faint stars, such as the majority of those present in the Magellanic Clouds. Thus, the statistics in their analysis will improve with additional integration time, which is currently at 22 months for Gaia DR2. Furthermore, having a larger sample of stars, better resolution of binaries, and accurate modeling of telescope systematics will all lead to improvements over time, yielding promising prospects for the use of their method on future data releases from Gaia and other astrometric surveys.

Figure 3: Constraints from the Magellanic Cloud velocity template analysis on the fractional dark matter abundance f_l of compact objects with mass M_l with a given density profile. The three linewidths represent compact object radii r_{l}=10^{-3}, 0.5, \text { and } 1 \mathrm{pc}. The constraint for the smallest radius is equivalent to the one for point-like objects. Above the diagonal line at the bottom right, at least one subhalo eclipses the data sample with 90% confidence level (CL). Figure 5 in the paper.

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What do we do?

Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.

Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

## From astrobites: “Investigating Early Populations of Galaxies with the Best Telescopes in the Universe”

From astrobites

Feb 5, 2020
Lukas Zalesky

Title: Early Low-Mass Galaxies and Star-Cluster Candidates at z ~ 6-9 Identified by the Gravitational Lensing Technique and Deep Optical/Near-Infrared Imaging
Authors: Shotaro Kikuchihara, Masami Ouchi, Yoshiaki Ono, Ken Mawatari et al.
First Author’s Institution: Institute for Cosmic Ray Research, The University of Tokyo

Status: Submitted to ApJ

In the coming years, we will see the launch of one of the most powerful space-based telescopes ever built, the James Webb Space Telescope (JWST), and we will see a new class of colossal ground-based observatories built with primary mirrors exceeding 30 meters in diameter.

NASA/ESA/CSA Webb Telescope annotated

ESO/E-ELT, 39 meter telescopeto be on top of Cerro Armazones in the Atacama Desert of northern Chile. located at the summit of the mountain at an altitude of 3,060 metres (10,040 ft).

TMT-Thirty Meter Telescope, proposed and now approved for Mauna Kea, Hawaii, USA4,207 m (13,802 ft) above sea level, the only giant 30 meter class telescope for the Northern hemisphere

Giant Magellan Telescope, 21 meters, to be at the Carnegie Institution for Science’s Las Campanas Observatory, to be built some 115 km (71 mi) north-northeast of La Serena, Chile, over 2,500 m (8,200 ft) high

However, despite all of our technical ingenuity, the most powerful telescopes in the universe are in fact galaxy clusters. As the most massive gravitationally bound structures, galaxy clusters severely distort their local spacetimes and can magnify substantial areas of the sky through the phenomenon of gravitational lensing.

Gravitational Lensing NASA/ESA

Cluster lenses allow astronomers to observe many distant sources in unprecedented detail that would otherwise be too faint to study (e.g., Fig. 1). Indeed, the possibility of discovering and characterizing some of the earliest and most distant galaxies observable was a primary motivation for conducting a deep survey of six galaxy clusters known to be powerful lenses. This project, dubbed The Hubble Frontier Fields, involved hundreds of hours of observations with the Hubble Space Telescope and the Spitzer Space Telescope.

NASA/ESA Hubble Telescope

NASA/Spitzer Infrared Telescope. No longer in service.

By combining our best telescopes with those that nature provides, astronomers uncovered hundreds of distant galaxies from times as early as one billion years after the Big Bang. In this astrobite, we cover a work that uses this rich sample of galaxies to trace the growth of stellar mass across the first few billion years of the universe.

Figure 1 – Galaxy cluster Abell 370, pictured above, is one of the six Hubble Frontier Fields. Among the population of orange cluster member galaxies are bluer background galaxies, magnified and distorted into giant arcs by gravitational lensing. Credit: NASA, ESA, the Hubble SM4 ERO Team, and ST-ECF.

Hundreds of Magnified Galaxies

In this paper, the authors exploit the power of gravitational lensing to magnify and reveal intrinsically faint sources at great distances, sources that would otherwise be impossible to study. The team begins by identifying high-redshift galaxies through the Lyman break method, (a.k.a., the “dropout” technique). UV radiation from distant galaxies is absorbed by neutral intervening gas, causing high redshift sources to appear faint in blue filters – thus, high redshift galaxies can be identified quickly by their colors. Combining all available imaging of the Hubble Frontier Fields, the team uses the Lyman break method to find a total of 357 magnified galaxies at 6 < z < 9, when the universe was less than a billion years old.

In order to study the full sample of galaxies in detail, the authors required carefully manicured images of their targets; at these distances, all galaxies appear extraordinarily faint, and low-mass galaxies typically go undetected. To alleviate this, the authors first correct for the magnification introduced by the cluster lenses using magnification maps provided by the Hubble Frontier Fields science team. Afterwards, the team creates image stacks of sources binned according to their apparent magnitudes, rewarding the team with high signal-to-noise (S/N) images which provide accurate photometry of the even the faintest galaxies at their sample.

Galaxy Evolution Metrics

Nearly all physical parameters of galaxies affect the way they emit light. This means that it is possible to recover the properties of galaxies by modeling their SEDs, or spectral energy distributions. To characterize each source, the team builds SED models that account for redshift, age, ionization state, stellar mass, stellar metallicity, dust content, and contribution from nebular emission. The constraints provided by high S/N photometric measurements across ten filters exceeds the number of free parameters, ensuring well-constrained models.

Figure 2 – In both plots, the red data points are from this work. Left: GSMF measured here, along with the best-fit Schechter function shown as a black line. Open circles and downward arrows are poorly constrained data points. Right: GSMD obtained by integrating the GSMF. The black and blue lines illustrate competing models of stellar mass build-up derived in previous works.

The authors use the inferred properties from their models to trace fundamental aspects of galaxy evolution, in particular the growth of stellar mass in galaxies during the first few billion years of the universe. A key observable in this regard is the galaxy stellar-mass function (GSMF; Fig. 2 left), which describes the average number-density of galaxies in the universe as a function of stellar mass. Integrating the GSMF gives the galaxy stellar mass density (GSMD; Fig. 2 right), which is the average density of stellar mass throughout the universe. Measuring these quantities across redshifts quantifies the growth of galaxies’ mass in stars throughout cosmic time, providing a simple benchmark for all theories of galaxy evolution.

While the GSMF has been well studied at low redshift, much is unknown about the GSMF in the early universe, especially at low masses. Fortunately, the high magnification due to lensing reveals some galaxies studied here with masses as low as Mstellar ~ 10^6 M☉, an extraordinary measurement at these distances. Consequently, this work provides some of the first constraints on the physical characteristics of such low mass galaxies during this epoch. At higher masses, the GSMF they measure is mostly consistent with previous works. However, at the highest redshifts, the authors find a greater abundance of massive galaxies than previous works. Furthermore, the authors measure higher stellar mass to (intrinsic) UV luminosity ratios. These pieces of information reveal that these massive star-forming galaxies favor a duration of star formation lasting ~ 100Myr, rather than a shorter, dramatic buildup of stars on shorter timescales suggested by other astronomers. In other words, the evolution of star formation rates is mostly smooth during these time periods. Regardless, further work is needed to ultimately constrain these evolutionary trends, given the current uncertainties on the massive galaxies in their sample.

Globular Cluster-type Sources Beyond z ~ 6…?

The mass-size relation in galaxies encodes fundamental differences in galaxy types. The last piece of this work involves assessing the masses and physical sizes of these distant galaxies and comparing these characteristics to those of more local sources. The authors combine the physical sizes obtained in a previous work with their inferred stellar masses and make an exciting discovery. Two sources, magnified by factors of ~ 20 and 80, have stellar masses (Mstellar < 10^7 M☉) and physical sizes (R < 40kpc) that make them comparable to globular clusters observed in the Milky Way (Fig. 3). The authors conclude that these sources could be members of a dominant class of low-mass galaxies expected to exist at these redshifts and could even be related to modern day globular clusters, which are known to have populations of old stars. These sources are particularly interesting, as it is thought that low-mass galaxies such as these likely evolve into Milky Way-sized galaxies we see today. Future telescopes, like the James Webb Space Telescope, may be able to obtain spectroscopic observations of these compact sources and reveal even more insight into their physical qualities.

Figure 3 – Galaxy size plotted against mass, with various types of galaxies color-coded accordingly (see this helpful astrobites page for a glossary of galaxy types). Galaxies at 6 < z < 7 are shown as the orange-to-red data points, and their colors indicate their magnification (μ). Other data points are from previous works. The blue highlighted square, where two galaxies identified in this work reside (along the top-right edge), indicates the region in parameter space occupied by globular clusters (GCs) and ultra-compact dwarf galaxies.

Gravitational lensing by galaxy clusters provides a unique window to the high-redshift universe. Thanks to these cosmic lenses, the authors were able to study the growth of stellar mass in galaxies during early times in the universe and probe some of the lowest mass systems ever detected beyond z = 6. This work highlights some of the great science that is possible when we combine the power of the best telescopes humans have made with these otherworldly lenses. Indeed, this combination ensures a truly remarkable view of the cosmos.

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Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.

Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

## From Ethan Siegel: “These Are The Most Distant Astronomical Objects In The Known Universe”

From Ethan Siegel
Dec 30, 2019

Astronomy’s enduring quest is to go farther, fainter, and more detailed than ever before. Here’s the edge of the cosmic frontier.

The distant galaxy MACS1149-JD1 is gravitationally lensed by a foreground cluster, allowing it to be imaged at high resolution and in multiple instruments, even without next-generation technology.

Gravitational Lensing NASA/ESA

This galaxy’s light comes to us from 530 million years after the Big Bang, but the stars within it are at least 280 million years old. It is the second-most distant galaxy with a spectroscopically confirmed distance, placing it 30.7 billion light-years away from us. (ALMA (ESO/NAOJ/NRAO), NASA/ESA HUBBLE SPACE TELESCOPE, W. ZHENG (JHU), M. POSTMAN (STSCI), THE CLASH TEAM, HASHIMOTO ET AL.)

ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres

NASA/ESA Hubble Telescope

Astronomers have always sought to push back the viewable distance frontiers.

Although there are magnified, ultra-distant, very red and even infrared galaxies in the eXtreme Deep Field, there are galaxies that are even more distant out there than what we’ve discovered in our deepest-to-date views. These galaxies will always remain visible to us, but we will never see them as they are today: 13.8 billion years after the Big Bang. (NASA, ESA, R. BOUWENS AND G. ILLINGWORTH (UC, SANTA CRUZ))

More distant galaxies appear fainter, smaller, bluer, and less evolved overall.

Galaxies comparable to the present-day Milky Way are numerous, but younger galaxies that are Milky Way-like are inherently smaller, bluer, more chaotic, and richer in gas in general than the galaxies we see today. For the first galaxies of all, this ought to be taken to the extreme, and remains valid as far back as we’ve ever seen. The exceptions, when we encounter them, are both puzzling and rare. (NASA AND ESA)

Milky Way NASA/JPL-Caltech /ESO R. Hurt. The bar is visible in this image

Laniakea supercluster. From Nature The Laniakea supercluster of galaxies R. Brent Tully, Hélène Courtois, Yehuda Hoffman & Daniel Pomarède at http://www.nature.com/nature/journal/v513/n7516/full/nature13674.html. Milky Way is the red dot.

Individual planets and stars are only known relatively nearby, as our tools cannot take us farther.

Local Group. Andrew Z. Colvin 3 March 2011

A massive cluster (left) magnified a distant star known as Icarus more than 2,000 times, making it visible from Earth (lower right) even though it is 9 billion light years away, far too distant to be seen individually with current telescopes. It was not visible in 2011 (upper right). The brightening leads us to believe that this was a blue supergiant star, formally named MACS J1149 Lensed Star 1. (NASA, ESA, AND P. KELLY (UNIVERSITY OF MINNESOTA))

As the 2010s end, here are our presently known most distant astronomical objects.

The ultra-distant supernova SN UDS10Wil, shown here, is the farthest type Ia supernova ever discovered, whose light arrives today from a position 17 billion light-years away.

A white dwarf fed by a normal star reaches the critical mass and explodes as a type Ia supernova. Credit: NASA/CXC/M Weiss

Type Ia supernovae are used as distance indicators because of their standard intrinsic brightnesses, and are some of our strongest evidence for the accelerated expansion best explained by dark energy.

Standard Candles to measure age and distance of the universe from supernovae NASA

(NASA, ESA, A. RIESS (STSCI AND JHU), AND D. JONES AND S. RODNEY (JHU))

The farthest type Ia supernova, our most distant “standard candle” for probing the Universe, is SN UDS10Wil, located 17 billion light-years (Gly) away.

This illustration of superluminous supernova SN 1000+0216, the most distant supernova ever observed at a redshift of z=3.90, from when the Universe was just 1.6 billion years old, is the current record-holder for individual supernovae. Unlike SN UDS10Wil, this supernova is a Type II (core collapse) supernova, and may have formed via the pair instability mechanism, which would explain its extraordinarily large intrinsic brightness. (ADRIAN MALEC AND MARIE MARTIG (SWINBURNE UNIVERSITY))

The most distant supernova of all, 2012’s superluminous SN 1000+0216, occurred 23 Gly away.

The most distant X-ray jet in the Universe, from quasar GB 1428, sends us light from when the Universe was a mere 1.25 billion years old: less than 10% its current age. This jet comes from electrons heating CMB photons, and is over 230,000 light-years in extent: approximately double the size of the Milky Way. (X-RAY: NASA/CXC/NRC/C.CHEUNG ET AL; OPTICAL: NASA/STSCI; RADIO: NSF/NRAO/VLA)

NASA/Chandra X-ray Telescope

NRAO/Karl V Jansky Expanded Very Large Array, on the Plains of San Agustin fifty miles west of Socorro, NM, USA, at an elevation of 6970 ft (2124 m)

The most distant quasar jet, revealed by GB 1428+4217’s X-rays, is 25.4 Gly distant.

This image of ULAS J1120+0641, a very distant quasar powered by a black hole with a mass two billion times that of the Sun, was created from images taken from surveys made by both the Sloan Digital Sky Survey and the UKIRT Infrared Deep Sky Survey.

SDSS Telescope at Apache Point Observatory, near Sunspot NM, USA, Altitude2,788 meters (9,147 ft)

UKIRT, located on Mauna Kea, Hawai’i, USA as part of Mauna Kea Observatory,4,207 m (13,802 ft) above sea level

The quasar appears as a faint red dot close to the centre. This quasar was the most distant one known from 2011 until 2017, and is seen as it was just 745 million years after the Big Bang. It is the most distant quasar with a visual image available to be viewed by the public. (ESO/UKIDSS/SDSS)

The first discovered object whose light exceeds 13 billion years in age, quasar ULAS J1120+0641, is 28.8 Gly away.

This artist’s concept shows the most distant quasar and the most distant supermassive black hole powering it. At a redshift of 7.54, ULAS J1342+0928 corresponds to a distance of some 29.32 billion light-years; it is the most distant quasar/supermassive black hole ever discovered. Its light arrives at our eyes today, in the radio part of the spectrum, because it was emitted just 686 million years after the Big Bang. (ROBIN DIENEL/CARNEGIE INSTITUTION FOR SCIENCE)

However, quasar ULAS J1342+0928 is even farther at 29.32 Gly: our most distant black hole.

This illustration of the most distant gamma-ray burst ever detected, GRB 090423, is thought to be typical of most fast gamma-ray bursts. When one or two objects violently form a black hole, such as from a neutron star merger, a brief burst of gamma rays followed by an infrared afterglow (when we’re lucky) allows us to learn more about these events. The gamma rays from this event lasted just 10 seconds, but Nial Tanvir and his team found an infrared afterglow using the UKIRT telescope just 20 minutes after the burst, allowing them to determine a redshift (z=8.2) and distance (29.96 billion light-years) to great precision. (ESO/A. ROQUETTE)

Gamma-ray bursts exceed even that; GRB 090423’s verified light comes from 29.96 Gly away in the distant Universe, while GRB 090429B might’ve been even farther.

Here, candidate galaxy UDFj-39546284 appears very faint and red, and from the colors it displays, it has an inferred redshift of 10, giving it an age below 500 million years and a distance greater than 31 billion light-years. Without spectroscopic confirmation, however, this and similar galaxies cannot reliably be said to have a known distance; more data is needed, as photometric redshifts are notoriously unreliable. (NASA, ESA, G. ILLINGWORTH (UNIVERSITY OF CALIFORNIA, SANTA CRUZ), R. BOUWENS (UNIVERSITY OF CALIFORNIA, SANTA CRUZ, AND LEIDEN UNIVERSITY) AND THE HUDF09 TEAM)

Ultra-distant galaxy candidates abound, including SPT0615-JD, MACS0647-JD, and UDFj-39546284, all lacking spectroscopic confirmation.

The most distant galaxy ever discovered in the known Universe, GN-z11, has its light come to us from 13.4 billion years ago: when the Universe was only 3% its current age: 407 million years old. The distance from this galaxy to us, taking the expanding Universe into account, is an incredible 32.1 billion light-years. (NASA, ESA, AND G. BACON (STSCI))

The most distant galaxy of all is GN-z11, located 32.1 Gly away.

The James Webb Space Telescope vs. Hubble in size (main) and vs. an array of other telescopes (inset) in terms of wavelength and sensitivity. It should be able to see the truly first galaxies, even the ones that no other observatory can see. Its power is truly unprecedented. (NASA / JWST SCIENCE TEAM)

NASA/ESA/CSA Webb Telescope annotated

With the 2020s promising revolutionary new observatories, these records may all soon fall.

Our deepest galaxy surveys can reveal objects tens of billions of light years away, but there are more galaxies within the observable Universe we still have yet to reveal between the most distant galaxies and the cosmic microwave background [CMB], including the very first stars and galaxies of all.

CMB per ESA/Planck

It is possible that the coming generation of telescopes will break all of our current distance records. (SLOAN DIGITAL SKY SURVEY (SDSS))

five-ways-keep-your-child-safe-school-shootings

Stem Education Coalition

“Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

## From NASA/ESA Hubble Telescope: “NASA’s Hubble Captures a Dozen Galaxy Doppelgangers”

NASA/ESA Hubble Telescope

From NASA/ESA Hubble Telescope

November 07, 2019

Ray Villard
Space Telescope Science Institute, Baltimore, Md.
410-338-4514
villard@stsci.edu

Emil Rivera-Thorsen
Institute of Theoretical Astrophysics, Oslo, Norway
+46 737 703 603
emil.rivera-thorsen@astro.uio.no

Håkon Dahle
Institute of Theoretical Astrophysics, Oslo, Norway
+47 93266331
hakon.dahle@astro.uio.no

Warped Space Creates Cool Kaleidoscope View of Faraway Galaxy

The “funhouse mirror” has delighted carnival-goers for more than a century by twisting peoples’ images into wildly distorted shapes. Its prolific inventor, Charles Frances Ritchel, called it the “Ritchel’s Laugh-O-Graphs.” However, there was nothing funny – but instead practical – about warped images as far as Albert Einstein was concerned. In developing his general theory of relativity, Einstein imagined the universe as a grand funhouse mirror caused by wrinkles in the very fabric of space.

This recent picture from Hubble shows a galaxy nicknamed the “Sunburst Arc” that has been split into a kaleidoscope illusion of no fewer than 12 images formed by a massive foreground cluster of galaxies 4.6 billion light-years away.

This beautifully demonstrates Einstein’s prediction that gravity from massive objects in space should bend light in a manner analogous to a funhouse mirror. His idea of space warping was at last proven in 1919 by observations of a solar eclipse where the sun’s bending of space could be measured. A further prediction was that the warping would create a so-called “gravitational lens” that, besides distortion, would increase the apparent size and brightness of distant background objects.

It wasn’t until 1979 that the first such gravitational lens was confirmed.

An otherwise obscure galaxy split and amplified the light of a distant quasar located far behind it into a pair of images. Far more than a space-carnival novelty, gravitational lensing observations today are commonly used to find planets around other stars, zoom in on very distant galaxies, and map the distribution of otherwise invisible “dark matter” in the universe.

This NASA Hubble Space Telescope photo reveals a cosmic kaleidoscope of a remote galaxy, which has been split into multiple images by an effect called gravitational lensing.

Gravitational Lensing NASA/ESA

Gravitational lensing means that the foreground galaxy cluster is so massive that its gravity distorts the fabric of space-time, bending and magnifying the light from the more distant galaxy behind it. This “funhouse mirror” effect not only stretches the background galaxy image, but also creates multiple images of the same galaxy.

The lensing phenomenon produces at least 12 images of the background galaxy, distributed over four major arcs. Three of these arcs are visible in the top right of the image, while one counter arc is visible in the lower left — partially obscured by a bright foreground star within the Milky Way.

The galaxy, nicknamed the Sunburst Arc, is almost 11 billion light-years from Earth and has been lensed into multiple images by a massive foreground cluster of galaxies 4.6 billion light-years away.

Hubble uses these cosmic magnifying glasses to study objects that would otherwise be too faint and too small for even its extraordinarily sensitive instruments. The Sunburst Arc is no exception, despite being one of the brightest gravitationally lensed galaxies known.

The lens makes images of the Sunburst Arc that are between 10 and 30 times brighter than the background galaxy would normally look. The magnification allows Hubble to view structures as small as 520 light-years across that would be too small to see without the turboboost from the lensing effect. The structures resemble star forming regions in nearby galaxies in the local universe, allowing astronomers to make a detailed study of the remote galaxy and its environment.

Hubble’s observations show that the Sunburst Arc is similar to galaxies which existed at a much earlier time in the history of the universe, perhaps only 150 million years after the Big Bang.

Science paper
Gravitational lensing reveals ionizing ultraviolet photons escaping from a distant galaxy
Science

Stem Education Coalition

The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

## From MIT News: “Astronomers use giant galaxy cluster as X-ray magnifying lens”

October 14, 2019
Jennifer Chu

Researchers have for the first time used a massive cluster of galaxies as a huge magnifying lens to detect a small, star-forming dwarf galaxy.
Image courtesy of the researchers.

New lens technique spots tiny dwarf galaxy in the first, super-energetic stages of star formation.

Astronomers at MIT and elsewhere have used a massive cluster of galaxies as an X-ray magnifying glass to peer back in time, to nearly 9.4 billion years ago. In the process, they spotted a tiny dwarf galaxy in its very first, high-energy stages of star formation.

While galaxy clusters have been used to magnify objects at optical wavelengths, this is the first time scientists have leveraged these massive gravitational giants to zoom in on extreme, distant, X-ray-emitting phenomena.

What they detected appears to be a blue speck of an infant galaxy, about 1/10,000 the size of our Milky Way, in the midst of churning out its first stars — supermassive, cosmically short-lived objects that emit high-energy X-rays, which the researchers detected in the form of a bright blue arc.

“It’s this little blue smudge, meaning it’s a very small galaxy that contains a lot of super-hot, very massive young stars that formed recently,” says Matthew Bayliss, a research scientist in MIT’s Kavli Institute for Astrophysics and Space Research. “This galaxy is similar to the very first galaxies that formed in the universe … the kind of which no one has ever seen in X-ray in the distant universe before.”

Bayliss says the detection of this single, distant galaxy is proof that scientists can use galaxy clusters as natural X-ray magnifiers, to pick out extreme, highly energetic phenomena in the universe’s early history.

“With this technique, we could, in the future, zoom in on a distant galaxy and age-date different parts of it — to say, this part has stars that formed 200 million years ago, versus another part that formed 50 million years ago, and pick them apart in a way you cannot otherwise do,” says Bayliss, who will be moving on to the University of Cincinnati as an assistant professor of physics.

He and his co-authors, including Michael McDonald, assistant professor of physics at MIT, have published their results today in the journal Nature Astronomy.

A candle in the light

Galaxy clusters are the most massive objects in the universe, composed of thousands of galaxies, all bound together by gravity as one enormous, powerful force. Galaxy clusters are so massive, and their gravitational pull is so strong, that they can distort the fabric of space-time, bending the universe and any surrounding light, much like an elephant would stretch and warp a trapeze net.

Scientists have used galaxy clusters as cosmic magnifying glasses, with a technique known as gravitational lensing.

Gravitational Lensing NASA/ESA

Radio galaxies gravitationally lensed by a very large foreground galaxy cluster Hubble

The idea is that if scientists can approximate the mass of a galaxy cluster, they can estimate its gravitational effects on any surrounding light, as well as the angle at which a cluster may deflect that light.

For instance, imagine if an observer, facing a galaxy cluster, were trying to detect an object, such as a single galaxy, behind that cluster. The light emitted by that object would travel straight toward the cluster, then bend around the cluster. It would continue traveling toward the observer, though at slightly different angles, appearing to the observer as mirrored images of the same object, which in the end can be combined as a single, “magnified” image.

Scientists have used galaxy clusters to magnify objects at optical wavelengths, but never in the X-ray band of the electromagnetic spectrum, mainly because galaxy clusters themselves emit an enormous amount of X-rays. Scientists have thought that any X-rays coming from a background source would be impossible to discern from the cluster’s own glare.

“If you’re trying to see an X-ray source behind a cluster, it’s like trying to see a candle next to a really bright light,” Bayliss says. “So we knew this was a challenging measurement to make.”

X-ray subtraction

The researchers wondered: Could they subtract that bright light and see the candle behind it? In other words, could they remove the X-ray emissions coming from the galaxy cluster, to view the much fainter X-rays coming from an object, behind and magnified by the cluster?

The team tested this idea with observations taken by NASA’s Chandra X-ray Observatory, one of the world’s most powerful X-ray space telescopes.

NASA/Chandra X-ray Telescope

They looked in particular at Chandra’s measurements of the Phoenix cluster, a distant galaxy cluster located 5.7 billion light-years from Earth, which has been estimated to be about a quadrillion times as massive as the sun, with gravitational effects that should make it a powerful, natural magnifying lens.

New observations of the galaxy cluster SPT-CLJ2344-4243 at X-ray, ultraviolet, and optical wavelengths are helping astronomers better understand this extraordinary system. Chandra data (blue) reveal large cavities in the X-rays, which have been combined in this composite image with optical data from Hubble (red, green, and blue). Astronomers think these X-ray cavities were carved out of the surrounding gas by powerful jets of high-energy particles emanating from near a supermassive black hole in the central galaxy of the cluster. Massive filaments of gas and dust, which extend for 160,000 to 330,000 lights years, surround the X-ray cavities.

“The idea is to take whatever your best X-ray telescope is — in this case, Chandra — and use a natural lens to magnify and effectively make Chandra bigger, so you can see more distant things,” Bayliss says.

He and his colleagues analyzed observations of the Phoenix cluster, taken continuously by Chandra for over a month. They also looked at images of the cluster taken by two optical and infrared telescopes — the Hubble Space Telescope and the Magellan telescope in Chile.

NASA/ESA Hubble Telescope

Carnegie 6.5 meter Magellan Baade and Clay Telescopes located at Carnegie’s Las Campanas Observatory, Chile. over 2,500 m (8,200 ft) high

With all these various views, the team developed a model to characterize the cluster’s optical effects, which allowed the researchers to precisely measure the X-ray emissions from the cluster itself, and subtract it from the data.

They were left with two similar patterns of X-ray emissions around the cluster, which they determined were “lensed,” or gravitationally bent, by the cluster. When they traced the emissions backward in time, they found that they all originated from a single, distant source: a tiny dwarf galaxy from 9.4 billion years ago, when the universe itself was roughly 4.4 billion years old — about a third of its current age.

“Previously, Chandra had seen only a handful of things at this distance,” Bayliss says. “In less than 10 percent of the time, we discovered this object, similarly far away. And gravitational lensing is what let us do it.”

The combination of Chandra and the Phoenix cluster’s natural lensing power enabled the team to see the tiny galaxy hiding behind the cluster, magnified about 60 times. At this resolution, they were able to zoom in to discern two distinct clumps within the galaxy, one producing many more X-rays than the other.

As X-rays are typically produced during extreme, short-lived phenomena, the researchers believe that the first X-ray-rich clump signals a part of the dwarf galaxy that has very recently formed supermassive stars, while the quieter region is an older region that contains more mature stars.

“We’re catching this galaxy at a very useful stage, where it’s got these really young stars,” Bayliss says. “Every galaxy had to start out in this phase, but we don’t see a lot of these kinds of galaxies in our own neighborhood. Now we can go back in time, look in the distant universe, find galaxies in this early phase of their life, and start to study how star formation is different there.”

This research was funded, in part, by NASA, and by the Space Telescope Science Institute.

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