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  • richardmitnick 1:53 pm on April 9, 2018 Permalink | Reply
    Tags: , , , , ESO Vipers, , Mapping the Universe in 3D   

    From ESOblog: “Mapping the Universe in 3D” 

    ESO 50 Large

    ESOblog

    ESO’s telescopes are used to study everything from the tiny dust particles spinning around distant suns to the large-scale structure of galaxies. The Very Large Telescope has recently undertaken a massive project called the VIMOS Public Extragalactic Redshift Survey (VIPERS), which catalogued 90 000 galaxies and measured their distribution as it was between five and eight billion years ago. To find out more, we interviewed Luigi Guzzo, Professor of Cosmology at the University of Milano, who led the VIPERS team.

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    The large-scale distribution of galaxies as it was between 5 and 8 billion years ago, unveiled by the nearly 90,000 new galaxy distances mapped by the VIPERS project.
    Some of the first spectra of distant galaxies obtained with VIMOS, where more than 220 galaxies were observed simultaneously. The light from each galaxy passes through the dedicated slit in the mask and produces a spectrum on the detector; each vertical rectangle contains the spectrum of one galaxy that is located several billion light-years away. These spectra allow astronomers to obtain the redshift, a measure of distance, as well as to assess the physical status of the gas and stars in each of these galaxies.
    Credit: ESO

    VIPERS FACTS
    The “VIMOS Public Extragalactic Redshift Survey” (VIPERS) is a completed ESO Large Program that has mapped in detail the spatial distribution of normal galaxies over an unprecedented volume of the z~1 Universe. It used the VIMOS spectrograph at the 8~m Very Large Telescope to measured spectra for more than 90,000 galaxies with red magnitude I(AB) brighter than 22.5 over an overall area of nearly 24 square degrees. At this redshift, VIPERS fills a unique niche in galaxy surveys, optimizing the combination of multi-band accurate photometry (5 bands from the CFHT-LS, plus Galex-NUV and NIR from WIRCAM and other facilities over most of the area) with the multiplexing capability of VIMOS. A robust color-color pre-selection allowed the survey to focus on the 0.5 < z < 1.2 redshift range, yielding an optimal combination of large volume (5 x 107 h-3 Mpc3) and high effective spectroscopic sampling (46% on average). VIPERS has produced a data set that in many respects represents for the first time the equivalent at z~1 of the large surveys of the "local" (z<0.2) Universe built at the beginning of this century (SDSS and 2dFGRS).

    VIPERS scientific investigations are focusing on measurements of large-scale structure and cosmological parameters at an epoch when the Universe was about half its current age. At the same time, the survey is exploring the ensemble properties of galaxies with unprecedented statistical accuracy at these redshifts, providing the natural extension back in time to classical results from the SDSS.

    Q: Why is cosmology so exciting to you?

    A: Ever since I was a kid, nature and the way things work have always fascinated me. This desire to understand how things work, at the deepest level, meant I would eventually become interested in either the very small or the very big. I ended up fascinated by the incredibly big: astronomy, in general, but mainly cosmology, which is related to the origins of everything, to the earliest questions in the Universe. It is connected to where the Universe comes from and how things originated from its homogenous initial state.

    Q: Tell us about the VIPERS project. What was the initial aim?

    A: VIPERS is a redshift survey, meaning we do a very simple thing: measure the distances of many, many galaxies to reconstruct their 3D distribution in a given volume of space. We have a way to reconstruct these distances because the Universe is quite kind to us: it’s expanding, and the apparent speed of expansion (which we see in the spectrum of each galaxy) is directly connected to the galaxy’s distance from us. The more distant galaxies are, the more rapidly they fly away from us, so the light we see from these galaxies is shifted towards the red. Thanks to this property of the Universe, we can get an approximation of their distance.

    VIPERS is the last in a series of deep surveys that began when VIMOS, the spectrograph at ESO’s VLT, was built at the end of the 1990s. VIMOS is very efficient, capable of collecting different spectra for 400–500 objects at the same time.

    Q: How do you measure the redshift of these galaxies?

    A: Essentially you take the light from galaxies or stars and send it through a spectrograph. A spectrograph is just a prism that splits light into colours like a rainbow. It shows you that in the spectra of stars and galaxies there are hydrogen lines, oxygen lines, iron lines, and so on — the same chemical elements that we know on Earth. These emission or absorption lines have a specific position and a specific wavelength, but decades ago astronomer Edwin Hubble and collaborators noticed that when looking at the spectra of other galaxies, the positions of these lines were moved, shifted towards the red. They also noticed that this shift was higher for more distant galaxies — and this is actually how the expansion of the Universe was discovered.

    Q: Why did you choose to catalogue 90 000 galaxies?

    A: Usually astronomers have to make compromises between their grand scientific aims and what the instrument they’re using actually allows them to do. VIMOS is very special in this respect because there is no other spectrograph in the world that allows you to have the same combination of area of the spectrograph and density of objects that you can observe simultaneously. This makes VIMOS ideal to do these surveys in the distant Universe.

    We chose to survey 90 000 galaxies in order to cover a volume comparable to the volumes we observed at the smaller redshifts (that is, nearby), because we wanted to compare the statistics. We wanted to look over as large a volume of space as possible, but we still wanted the galaxies to be close enough together to allow us to see the details of galactic structures. So we compromised at 90 000.

    Q: So what did this survey tell us about the Universe?

    A: We actually learned a lot about Einstein’s theory of general relativity, which is something we thought about when we proposed the VIPERS project. Galaxies tend to move towards regions of higher density, so, in some way, these galactic motions reflect the growth of the structure of the Universe. As time passes this structure keeps condensing, so when you measure the redshift, you are including this little velocity component that actually contains information about the dynamics of the Universe — and you can use it to determine how quickly these structures grow. In other words, it is a way to test the theory of relativity.

    So, if you have modifications of general relativity on a very large scale, these could be “visible” in the way galaxies assemble. One way to explain such modifications is to include them in the equations of general relativity: as what Einstein called the cosmological constant. We don’t yet understand the origin of this constant, and since it is so difficult to understand in terms of theoretical physics, people started thinking that perhaps it’s not the right solution, perhaps you have to modify general relativity at large scales. This was one of the driving ideas for VIPERS. We presented four measurements of the growth of structure, using four different techniques from the same data, which we published over the past year.

    Q: So what were the main conclusions of the survey?

    A: Essentially all of our measurements are consistent with general relativity. With VIPERS we could see how different types of galaxies trace the structure. For example, we discovered that if we used the luminous blue galaxies, then the measurements of this growth rate are more accurate and less biased.

    Unexpectedly, this survey also allowed us to measure cosmic voids — the spaces between large-scale galactic structures. By looking at cosmic voids with VIPERS, we could see the way galaxies flow away from these voids, because voids are underdense regions, so the galactic structures around them tend to squeeze.

    Equally important, I think, were our results on galaxy evolution. These are really outstanding — by combining VIPERS and the existing Sloan Digital Sky Survey data of the local Universe, we could cover 9 billion years of evolution to see how galaxies transform from the early Universe to today.

    We saw how galaxies change their colour over time. Back in the earlier Universe, we saw a fraction of massive blue galaxies (meaning they are young, active, and still forming stars) which are no longer around today. They’ve become red as they grow older, so the number of red massive galaxies grows while the number of blue massive galaxies declines. That’s a very important result.

    What’s really amazing is that even though we observed 90 000 galaxies, VIPERS was only conducted in 440 hours of observing time. The amount of information it produced is incredible.


    The positions in space of the galaxies identified by the VIPERS survey. This “slice” through the Universe shows where the galaxies lie as we look to ever greater distances in space — corresponding to looking further back in time. Data like these allow astronomers to study the evolution of galaxies as a constituent of the Universe, and tell us about how space itself evolves over time.
    Credit: S. Arnouts, N. Malavasi & the VIPERS Collaboration

    Q: Did you learn any new techniques that might be useful for other projects or fields?

    A: Definitely. What we learned about the instrumentation and the data reduction is now going to be used for a big project of the European Space Agency called Euclid, a space telescope with a spectrograph and an imager on board that will be launched in 2021. My team is involved in the spectroscopic part of the project — which is very different and much more complicated to use than VIMOS, but our work on VIPERS with VIMOS will help us when looking at data from Euclid.

    Q: Is there anything left to do on the VIPERS project?

    A: There are a few more papers in preparation, where we look at more specific details, in particular on the galactic evolution side. In terms of cosmology, I think it is basically done — but our dataset is still a great playground for people who want to test new methods, and we hope the sample will be used a lot by other people with smart ideas, who may find something unexpected. That’s the beauty of these large redshift surveys: the discovery space that you open.

    As a final note, I just want to add that the support from the ESO staff to this project has been really great. One of the reasons why the project went well was because they supported us and always responded promptly to our request and questions.

    The VIMOS Public Extragalactic Redshift Survey (VIPERS)⋆An unprecedented view of galaxies and large-scale structure at 0.5 < z < 1.2. Astronomy and Astrophysics

    The VIMOS Public Extragalactic Redshift Survey (VIPERS)Full spectroscopic data and auxiliary information release (PDR-2)⋆ Astronomy and Astrophysics

    Biography Luigi Guzzo

    Luigi Guzzo is Professor of Cosmology at the University of Milano. He is a cosmologist, interested in observing and modelling the large-scale structure of the Universe. Over the past decade he has led the VIMOS Public Extragalactic Redshift Survey (VIPERS) with the ESO VLT and he is now one of the core science coordinators of the ESA mission Euclid, a space telescope to map the dark and luminous Universe, due to launch in 2021. In 2012 he has received an Advanced Grant from the European Research Council (ERC), a five-year financial contribution that sustained the development of new analysis methods and their application to VIPERS and other surveys.

    See the full article here .

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    ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

    ESO LaSilla
    ESO/Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT
    VLT at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

    ESO Vista Telescope
    ESO/Vista Telescope at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

    ESO NTT
    ESO/NTT at Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT Survey telescope
    VLT Survey Telescope at Cerro Paranal with an elevation of 2,635 metres (8,645 ft) above sea level.

    ALMA Array
    ALMA on the Chajnantor plateau at 5,000 metres.

    ESO E-ELT
    ESO/E-ELT to be built at Cerro Armazones at 3,060 m.

    ESO APEX
    APEX Atacama Pathfinder 5,100 meters above sea level, at the Llano de Chajnantor Observatory in the Atacama desert.

    Leiden MASCARA instrument, La Silla, located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    Leiden MASCARA cabinet at ESO Cerro la Silla located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    ESO Next Generation Transit Survey at Cerro Paranel, 2,635 metres (8,645 ft) above sea level

    SPECULOOS four 1m-diameter robotic telescopes 2016 in the ESO Paranal Observatory, 2,635 metres (8,645 ft) above sea level

    ESO TAROT telescope at Paranal, 2,635 metres (8,645 ft) above sea level

    ESO ExTrA telescopes at Cerro LaSilla at an altitude of 2400 metres

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  • richardmitnick 11:22 am on December 16, 2016 Permalink | Reply
    Tags: , , , ESO Vipers   

    From ESO: “3D Map of Distant Galaxies Completed” 

    ESO 50 Large

    European Southern Observatory

    15 December 2016
    Luigi Guzzo
    Dipartimento di Fisica, Università Statale di Milano
    & INAF – Osservatorio Astronomico di Brera
    Milano, Italy
    Mobile: +39 366 773 9704
    Email: luigi.guzzo@unimi.it

    Peter Grimley
    ESO Assistant Public Information Officer
    Garching bei München, Germany
    Tel: +49 89 3200 6383
    Email: pgrimley@partner.eso.org

    VLT survey shows distribution in space of 90 000 galaxies

    1

    For nearly eight years, the VIsible MultiObject Spectrograph (VIMOS) on ESO’s Very Large Telescope (VLT) in Chile has been piecing together a three-dimensional map of galaxies in two patches of the southern sky. A total of 440 hours of observing time has gone into measuring the spectra of more than 90 000 distant galaxies, producing a map of a 24-square-degree region on the sky, out to a distance corresponding to when the Universe was around half its current age [1].

    ESO VIMOS
    ESO VIMOS

    In 2013, ESO reported that the international team of astronomers behind the VIMOS Public Extragalactic Survey (VIPERS) had collected data for around 60% of their target galaxies. With the full set of observations now completed, this is the largest redshift survey ever undertaken with ESO telescopes [2] and it provides a view of structures in the younger Universe with an unprecedented combination of detail and spatial extent. By surveying how galaxies were distributed in space several billion years ago, astronomers are able to learn more about the distribution of matter on the largest scales in the cosmos, as well as to further probe the effect that the mysterious dark energy had on the young Universe, when it acquired some of the properties we see today.

    Using these unique data, astronomers are already obtaining exciting new results concerning how galaxies have evolved since the Universe was much younger, and how this connects to the details of large-scale structures, such as filaments, clusters and voids. The full set of data from the survey was released to the public in November 2016 and is now available in standard form on the ESO archive.

    Notes

    [1] Light has a finite speed limit, so the more distant an object, the more time it has taken for the light from it to reach us. This means that we see distant objects as they were long in the past.

    [2] The light from each galaxy is spread out into its component colours within the VIMOS instrument. Careful analysis allows astronomers to work out how fast the galaxy is moving away from us — usually expressed as its redshift. This in turn reveals its distance from us and, when combined with its position on the sky, its location in the Universe.
    More information

    The team is composed of astronomers in Italy, France, Poland and the UK. Full details are available on the VIPERS website.

    See the full article here .

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    ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

    ESO LaSilla
    LaSilla

    ESO VLT
    VLT

    ESO Vista Telescope
    VISTA

    ESO NTT
    NTT

    ESO VLT Survey telescope
    VLT Survey Telescope

    ALMA Array
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  • richardmitnick 9:37 pm on August 19, 2014 Permalink | Reply
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    From ESO- VIPERS 2013: “Huge Map of the Distant Universe Reaches Halfway Point” 


    European Southern Observatory

    12 March 2013
    VLT survey charts positions of 55 000 galaxies

    map

    Luigi Guzzo
    INAF – Osservatorio Astronomico di Brera
    Merate, Italy
    Tel.: +39 039 5971 025
    Mobile: +39 366 773 9704
    Email: luigi.guzzo@brera.inaf.it

    Richard Hook
    ESO, Public Information Officer
    Garching bei München, Germany
    Tel: +49 89 3200 6655
    Cell: +49 151 1537 3591
    Email: rhook@eso.org

    The largest project ever undertaken to map out the Universe in three dimensions using ESO telescopes has reached the halfway stage. An international team of astronomers has used the VIMOS instrument on the ESO Very Large Telescope to measure the distances to 55 000 galaxies [1] as part of the VIPERS survey [2]. This has already allowed them to create a remarkable three-dimensional view of how galaxies were distributed in space in the younger Universe. This reveals the complex web of the large-scale structure of the Universe in great detail.

    ESO VLT Interferometer
    ESO/VLT

    ESO VIMOS
    VIMOS

    By studying the cosmic web astronomers can test theories of how the Universe formed and evolved and help to track down the properties of the mysterious dark energy that is making the expansion of the Universe speed up. By mapping how large-scale structure grows with time they can also check whether [Albert] Einstein’s theory of general relativity holds precisely, or whether it may need to be revised.

    VIPERS is the most detailed survey so far of galaxies that are seen from the time when astronomers think that the Universe became dominated by dark energy, as it is today. This happened when the Universe was between about five and nine billion years old — about half its current age of 13.7 billion years. Although it is not yet complete, VIPERS is already delivering exciting science results, including both a first estimate of the growth rate of large-scale structure at this time and the best census ever of the average number of massive galaxies during this period of the Universe’s history.

    This week, to mark this milestone, the team is submitting several papers that describe the survey and the initial results for publication in scientific journals. The results from VIPERS are made public for use by astronomers around the world. The current catalogue of galaxy distances will be released in September this year.
    Notes

    [1] The light of each galaxy is spread out into its component colours within VIMOS. Subsequent careful analysis then allows astronomers to work out how fast the galaxy appears to move away from us — its redshift. This in turn reveals its distance and, when combined with its position on the sky, its location in the Universe.

    [2] VIPERS stands for the VIMOS Public Extragalactic Redshift Survey. Further information is available here.

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  • richardmitnick 9:34 am on March 12, 2013 Permalink | Reply
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    From ESO: “Huge Map of the Distant Universe Reaches Halfway Point” 

    12 March 2013

    VLT survey charts positions of 55,000 galaxies

    The largest project ever undertaken to map out the Universe in three dimensions using ESO telescopes has reached the halfway stage. An international team of astronomers has used the VIMOS instrument on the ESO Very Large Telescope to measure the distances to 55000 galaxies as part of the VIPERS survey . This has already allowed them to create a remarkable three-dimensional view of how galaxies were distributed in space in the younger Universe. This reveals the complex web of the large-scale structure of the Universe in great detail.

    vimos
    Vimos

    vipers

    By studying the cosmic web astronomers can test theories of how the Universe formed and evolved and help to track down the properties of the mysterious dark energy that is making the expansion of the Universe speed up. By mapping how large-scale structure grows with time they can also check whether Einstein’s theory of general relativity holds precisely, or whether it may need to be revised.

    vimos

    The light of each galaxy is spread out into its component colours within VIMOS. Subsequent careful analysis then allows astronomers to work out how fast the galaxy appears to move away from us — its redshift. This in turn reveals its distance and, when combined with its position on the sky, its location in the Universe.”

    See the full article here.

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    Facebook

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    THE BASIC TOOLS OF E.S.O.
    i1
    Paranal Platform The VLT
    ESO NTT

    NTT – New Technology Telescope


    La Silla

    alma
    ALMA Atacama Large Millimeter/submillimeter Array

    i2
    The European Extremely Large Telescope
    VISTAVISTA (the Visible and Infrared Survey Telescope for Astronomy)


    Atacama Pathfinder Experiment telescope (APEX)

    ESO, European Southern Observatory, builds and operates a suite of the world’s most advanced ground-based astronomical telescopes.


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