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| COS-Halos | |
|---|---|
| Name | COS-Halos |
| Instrument | Cosmic Origins Spectrograph |
| Telescope | Hubble Space Telescope |
| Principal investigator | John Tumlinson |
| Collaborators | Jason Tumlinson, Todd Tripp, Christopher Thom, Mark Giroux, Jessica Werk, J. Xavier Prochaska |
| Year | 2012 |
| Wavelength | Ultraviolet |
| Target | Low-redshift galaxies |
| Goals | Circumgalactic medium characterization |
COS-Halos
COS-Halos was a landmark ultraviolet spectroscopic survey using the Cosmic Origins Spectrograph on the Hubble Space Telescope to probe the circumgalactic medium around low-redshift galaxies. The program combined sightlines to background quasars with multiwavelength galaxy data from surveys and observatories including Sloan Digital Sky Survey, Keck Observatory, Magellan Telescopes, Gemini Observatory, and facilities operated by the National Optical Astronomy Observatory. The collaboration involved investigators affiliated with institutions such as Space Telescope Science Institute, Yale University, University of California, Santa Cruz, and Carnegie Observatories.
COS-Halos targeted the diffuse, ionized gas surrounding galaxies, linking absorption-line signatures seen in quasar spectra to galaxy properties measured by surveys like Sloan Digital Sky Survey and follow-up programs using Keck Observatory and Magellan Telescopes. The survey built on prior work using instruments such as the Far Ultraviolet Spectroscopic Explorer and aimed to address questions previously explored by teams connected to COS Science Team, Hubble Deep Field, and projects at Space Telescope Science Institute. The principal investigators and team members included researchers with ties to Yale University, Carnegie Observatories, University of California, Santa Cruz, Princeton University, and University of Arizona.
COS-Halos observed approximately 44 low-redshift galaxies by acquiring ultraviolet spectra of background quasars with the Cosmic Origins Spectrograph on the Hubble Space Telescope, selected to probe impact parameters out to ~150 kpc around galaxies drawn from the Sloan Digital Sky Survey catalog. The sample selection strategy linked galaxy stellar masses and colors measured via instruments at Kitt Peak National Observatory, Palomar Observatory, and data reduction pipelines used by teams at Space Telescope Science Institute and National Optical Astronomy Observatory. Ancillary spectroscopy and imaging employed telescopes like Keck Observatory, Magellan Telescopes, Gemini Observatory, and WIYN Observatory to secure redshifts, metallicities, and star-formation indicators used by collaborating groups at Yale University and University of California, Santa Cruz.
Data reduction used standard pipelines developed by the Space Telescope Science Institute for the Cosmic Origins Spectrograph, supplemented by custom routines employed by analysts at Yale University and Carnegie Observatories to coadd spectra, normalize continua, and identify absorption features from ions such as O VI, C IV, Si II, and H I. Line-profile fitting and column-density measurements applied techniques established in studies from groups at Princeton University, University of California, Santa Cruz, and JHU investigators who had developed Voigt-profile fitting tools and error-analysis frameworks. Cross-correlation with galaxy catalogs from Sloan Digital Sky Survey and follow-up spectroscopy at Keck Observatory enabled association of absorbers with galaxy systemic velocities, while ionization modeling used codes and approaches pioneered by researchers at Harvard University, University of Cambridge, and the Max Planck Institute for Astronomy.
COS-Halos demonstrated that massive, L* galaxies possess substantial reservoirs of ionized gas traced by strong H I and O VI absorption within roughly the virial radius, a result that resonated with theoretical expectations from teams at Princeton University, University of California, Berkeley, and Lawrence Berkeley National Laboratory. The survey found correlations between galaxy stellar mass, color, and circumgalactic absorption strengths, echoing observational themes from projects at Yale University, Carnegie Observatories, and University of Washington. Metallicity estimates and ionization states implied enriched gas consistent with outflows and recycling processes discussed in models by groups at Caltech, Institute for Advanced Study, and Max Planck Institute for Astrophysics. COS-Halos also quantified baryon budgets in halos, addressing the "missing baryons" problem debated by researchers at NASA Goddard Space Flight Center, Columbia University, and Rutgers University and connecting to absorption-line surveys by teams at University of Colorado and Penn State University.
Results from COS-Halos informed theoretical frameworks developed at Princeton University, Harvard University, Massachusetts Institute of Technology, and the Kavli Institute for Theoretical Physics concerning gas accretion, feedback, and galaxy quenching. The presence of metal-enriched, multiphase circumgalactic gas supported scenarios advanced by groups at University of California, Santa Cruz, University of Cambridge, and Max Planck Institute for Astronomy where galactic winds and recycled accretion govern star-formation regulation. COS-Halos outcomes influenced semi-analytic and hydrodynamical models produced by teams at Durham University, University of Oxford, Columbia University, University of California, Berkeley, and numerical simulation efforts like those from Illustris, EAGLE, and collaborations linked to Max Planck Institute for Astrophysics.
Follow-up observations expanded with programs such as COS-Dwarfs, COS-GASS, and surveys leveraging the Hubble Space Telescope and ground-based facilities including Keck Observatory, Magellan Telescopes, Gemini Observatory, and Very Large Telescope. Related large surveys and collaborations engaged institutions like Yale University, Carnegie Observatories, University of California, Santa Cruz, Princeton University, Harvard University, University of Cambridge, Max Planck Institute for Astronomy, Durham University, and consortiums involved in projects such as Sloan Digital Sky Survey and numerical efforts exemplified by Illustris and EAGLE. Subsequent analyses consolidated insights from COS-Halos with observations from Chandra X-ray Observatory and instruments associated with European Southern Observatory programs to refine understanding of baryon cycles and circumgalactic thermodynamics.
Category:Astronomical surveys