Tagged: SpARCS-Spitzer Adaptation of the Red-sequence Cluster Survey Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 12:00 pm on October 26, 2018 Permalink | Reply
    Tags: , , , , SpARCS-Spitzer Adaptation of the Red-sequence Cluster Survey, , UCR astronomers get best measure yet of how fast star formation stopped in galaxy clusters in the early universe   

    From UC Riverside: “UCR astronomers get best measure yet of how fast star formation stopped in galaxy clusters in the early universe” 

    UC Riverside bloc

    From UC Riverside

    1
    UC Riverside-led study provides new insight into why galaxies stop forming stars.

    2
    This image, taken by NASA’s Hubble Space Telescope, shows galaxy cluster SDSS J0333+0651. (Credit: NASA/ESA Hubble)

    Clusters of galaxies are rare regions of the universe consisting of hundreds of galaxies containing trillions of stars, as well as hot gas and dark matter. It has long been known that when a galaxy falls into a cluster, star formation is fairly rapidly shut off in a process known as “quenching.” What actually causes the stars to quench, however, is a mystery, despite several plausible explanations having been proposed by astronomers.

    A new international study led by astronomer Ryan Foltz, a former graduate student at the University of California, Riverside, has made the best measurement yet of the quenching timescale, measuring how it varies across 70 percent of the history of the universe. The study has also revealed the process which is likely responsible for shutting down star formation in clusters.

    Each galaxy infalling into a cluster is known to bring some cold gas with it which has not yet formed stars.

    3
    The Tadpole Galaxy is a disrupted spiral galaxy showing streams of gas stripped by gravitational interaction with another galaxy. Molecular gas is the required ingredient to form stars in galaxies in the early universe. Credit: Hubble Legacy Archive, ESA, NASA and Bill Snyder.

    One possibility that has been suggested is that, before it could turn into stars, this cold gas fuel was “stripped” away from the galaxy by the hot, dense gas already in the cluster, causing star formation to cease.

    Another possibility is that galaxies were instead “strangled,” that is, they stopped forming stars because their reservoirs ceased getting replenished with additional cold gas once they fell inside the cluster. This is predicted to be a slower process than stripping.

    A third possibility is that energy from the star formation itself drove much of the cold gas fuel away from the galaxy and prevented it from forming new stars. This “outflow” scenario is predicted to occur on a faster timescale than stripping, because the gas is lost forever to the galaxy and is unavailable to form new stars.

    Because these three different physical processes predict galaxies to quench on different relative timescales over the history of the universe, astronomers have long known that if they could compare the number of quenched galaxies observed over a long time-baseline, the dominant process causing stars to quench would more readily become apparent. The problem: until recently, it was very difficult to find distant clusters, never mind measure the properties of their galaxies. The international Spitzer Adaptation of the Red-sequence Cluster Survey, or SpARCS, survey has now made a measurement of more than 70 percent of the history of the universe, accomplished by pioneering new cluster detection techniques which enabled the discovery of hundreds of new clusters in the distant universe.

    4
    Color images of the central regions of z > 1.35 SpARCS clusters. Cluster members are marked with white squares. Credit: SpARCS collaboration.

    Using some of their own newly-discovered SpARCS clusters, the new UCR-led study discovered that it takes a galaxy longer to stop forming stars as the universe gets older: only 1.1 billion years when the universe is young (4 billion years old), 1.3 billion years when the universe is middle-aged (6 billion years old), and 5 billion years in the present-day universe.

    “Comparing observations of the quenching timescale in galaxies in clusters in the distant universe to those in the nearby universe, revealed that a dynamical process such as gas stripping is a better fit to the predictions than strangulation or outflows,” said Foltz.

    To make this state-of-the art measurement, the SpARCS team required 10 nights of observations with the W. M. Keck Observatory telescopes (10 meters in diameter) in Hawaii, and 25 nights of observations with the twin Gemini telescopes (8 meters in diameter) in Hawaii and Chile.


    Keck Observatory, Maunakea, Hawaii, USA.4,207 m (13,802 ft), above sea level, showing also NASA’s IRTF and NAOJ Subaru


    Gemini South telescope, Cerro Tololo Inter-American Observatory (CTIO) campus near La Serena, Chile, at an altitude of 7200 feet


    Gemini/North telescope at Maunakea, Hawaii, USA,4,207 m (13,802 ft) above sea level

    “Thanks to the phenomenal investment in our work by these observatories, we now believe we have a good idea of how star formation stops in the most massive galaxies in clusters,” said Gillian Wilson, professor of physics and astronomy at UCR and leader of the SpARCS survey, in whose lab Foltz worked when the study was done. “There are good reasons, however, to believe that lower-mass galaxies may quench by a different process. That is one of the questions our team is working on answering next.”

    The team has been awarded 50 additional nights of Gemini time and a $1.2 million grant from the National Science Foundation to study how star formation stops in more regular-mass galaxies. Wilson was also awarded Hubble Space Telescope observations and a NASA grant to analyze high-resolution images of the quenching galaxies.

    NASA/ESA Hubble Telescope

    The research paper will be published in The Astrophysical Journal.

    The W. M. Keck Observatory findings were obtained as the result of a collaboration amongst UC faculty members Gillian Wilson (UCR), Michael Cooper (UCI) and Saul Perlmutter (UCB). Other authors involved in the study were Adam Muzzin (University of York, Canada), Julie Nantais (Andres Bello University, Chile), Remco van der Burg (European Southern Observatory, Germany), Pierluigi Cerulo (Universidad de Concepción, Chile), Jeffrey Chan (UCR), Sean Fillingham (UCI), Jason Surace (California Institute of Technology), Tracy Webb (McGill University, Canada), Allison Noble (MIT), Mark Lacy (National Radio Astronomy Observatory), Michael McDonald (MIT), Gregory Rudnick (University of Kansas), Ricardo Demarco (Universidad de Concepción, Chile), Christopher Lidman (Australian Astronomical Observatory), Julie Hlavacek-Larrondo (University of Montreal), Howard Yee (University of Toronto, Canada), and Brian Hayden (UCB).

    The study was supported by grants from NSF and NASA.

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    UC Riverside Campus

    The University of California, Riverside is one of 10 universities within the prestigious University of California system, and the only UC located in Inland Southern California.

    Widely recognized as one of the most ethnically diverse research universities in the nation, UCR’s current enrollment is more than 21,000 students, with a goal of 25,000 students by 2020. The campus is in the midst of a tremendous growth spurt with new and remodeled facilities coming on-line on a regular basis.

    We are located approximately 50 miles east of downtown Los Angeles. UCR is also within easy driving distance of dozens of major cultural and recreational sites, as well as desert, mountain and coastal destinations.

     
  • richardmitnick 1:31 pm on July 20, 2017 Permalink | Reply
    Tags: , , , Cluster galaxies, , field galaxies, , SpARCS-Spitzer Adaptation of the Red-sequence Cluster Survey,   

    From UC Riverside: “Scientists Get Best Measure of Star-forming Material in Galaxy Clusters in Early Universe” 

    UC Riverside bloc

    UC Riverside

    July 20, 2017
    Iqbal Pittalwala

    1
    The Tadpole Galaxy is a disrupted spiral galaxy showing streams of gas stripped by gravitational interaction with another galaxy. Molecular gas is the required ingredient to form stars in galaxies in the early universe. Credit: Hubble Legacy Archive, ESA, NASA and Bill Snyder.

    The international Spitzer Adaptation of the Red-sequence Cluster Survey (SpARCS) collaboration based at the University of California, Riverside has combined observations from several of the world’s most powerful telescopes to carry out one of the largest studies yet of molecular gas – the raw material which fuels star formation throughout the universe – in three of the most distant clusters of galaxies ever found, detected as they appeared when the universe was only four billion years old.

    Results were recently published in The Astrophysical Journal Letters. Allison Noble, a postdoctoral researcher at the Massachusetts Institute of Technology, led this newest research from the SpARCS collaboration.

    Clusters are rare regions of the universe consisting of tight groups of hundreds of galaxies containing trillions of stars, as well as hot gas and mysterious dark matter. First, the research team used spectroscopic observations from the W. M. Keck Observatory on Maunakea, Hawai’i, and the Very Large Telescope in Chile that confirmed 11 galaxies were star-forming members of the three massive clusters.


    Keck Observatory, Maunakea, Hawaii, USA

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

    Next, the researchers took images through multiple filters from NASA’s Hubble Space Telescope, which revealed a surprising diversity in the galaxies’ appearance, with some galaxies having already formed large disks with spiral arms.

    NASA/ESA Hubble Telescope

    One of the telescopes the SpARCS scientists used is the extremely sensitive Atacama Large Millimeter Array (ALMA) telescope capable of directly detecting radio waves emitted from the molecular gas found in galaxies in the early universe.

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

    ALMA observations allowed the scientists to determine the amount of molecular gas in each galaxy, and provided the best measurement yet of how much fuel was available to form stars.

    The researchers compared the properties of galaxies in these clusters with the properties of “field galaxies” (galaxies found in more typical environments with fewer close neighbors). To their surprise, they discovered that cluster galaxies had higher amounts of molecular gas relative to the amount of stars in the galaxy, compared to field galaxies. The finding puzzled the team because it has long been known that when a galaxy falls into a cluster, interactions with other cluster galaxies and hot gas accelerate the shut off of its star formation relative to that of a similar field galaxy (the process is known as environmental quenching).

    “This is definitely an intriguing result,” said Gillian Wilson, a professor of physics and astronomy at UC Riverside and the leader of the SpARCS collaboration. “If cluster galaxies have more fuel available to them, you might expect them to be forming more stars than field galaxies, and yet they are not.”

    Noble, a SpARCS collaborator and the study’s leader, suggests several possible explanations: It is possible that something about being in the hot, harsh cluster environment surrounded by many neighboring galaxies perturbs the molecular gas in cluster galaxies such that a smaller fraction of that gas actively forms stars. Alternatively, it is possible that an environmental process, such as increased merging activity in cluster galaxies, results in the observed differences between the cluster and field galaxy populations.

    “While the current study does not answer the question of which physical process is primarily responsible for causing the higher amounts of molecular gas, it provides the most accurate measurement yet of how much molecular gas exists in galaxies in clusters in the early universe,” Wilson said.

    The SpARCS team has developed new techniques using infrared observations from NASA’s Spitzer Space Telescope to identify hundreds of previously undiscovered clusters of galaxies in the early universe.

    NASA/Spitzer Telescope

    In the future, they plan to study a larger sample of clusters. The team has recently been awarded additional time on ALMA, the W. M. Keck Observatory, and the Hubble Space Telescope to continue investigating how the neighborhood in which a galaxy lives determines for how long it can form stars.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    UC Riverside Campus

    The University of California, Riverside is one of 10 universities within the prestigious University of California system, and the only UC located in Inland Southern California.

    Widely recognized as one of the most ethnically diverse research universities in the nation, UCR’s current enrollment is more than 21,000 students, with a goal of 25,000 students by 2020. The campus is in the midst of a tremendous growth spurt with new and remodeled facilities coming on-line on a regular basis.

    We are located approximately 50 miles east of downtown Los Angeles. UCR is also within easy driving distance of dozens of major cultural and recreational sites, as well as desert, mountain and coastal destinations.

     
c
Compose new post
j
Next post/Next comment
k
Previous post/Previous comment
r
Reply
e
Edit
o
Show/Hide comments
t
Go to top
l
Go to login
h
Show/Hide help
shift + esc
Cancel
%d bloggers like this: