NOAO >   Observing Info >   Approved Programs >   2009A-0291

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Proposal Information for 2009A-0291


PI: Jean-Rene Gauthier, University of Chicago, gauthier@oddjob.uchicago.edu
Address: KICP, Astronomy & Astrophysics, 5640 S. Ellis Ave, Chicago, IL 60637, USA

CoI: Hsiao-Wen Chen, KICP, University of Chicago
CoI: Jeremy L. Tinker, University of California, Berkeley

Title: Probing the Gaseous Halos of SDSS Galaxies at z<0.4

Abstract: The Mg II (lambda)(lambda) 2796, 2803 doublets are among the absorption features commonly seen in the spectra of distant quasars. These absorbers arise primarily in photo-ionized halo gas around foreground galaxies. We propose to use MagE on the Magellan Clay telescope to observe 20 QSOs that are within ~ 100 h^-1 kpc projected distances of a foreground galaxy identified in SDSS. MagE is an echellette spectrograph that offers exceptional throughput over (Delta) (lambda)=3,050-10,000Awith a spectral resolution of (delta) v~ 40 km/s. It allows observations of Mg II absorbers associated with galaxies at z ~ 0.1. The objectives of the proposed observations are (1) to constrain the covering fraction of cool gas around low-redshift galaxies at z=0.14-0.35 for which there is no covering fraction data currently available; and (2) to examine the correlation between Mg II absorption properties and known galaxy properties such as luminosity, impact distance and stellar population. The results will be combined with available Mg II measurements near galaxies at z~ 0.4-1 for establishing an empirical characterization of the evolution of cool baryons in dark matter halos. We were awarded 2 nights in 2008B (Sept.23-24) for this project. A preliminary analysis of the data shows a positive Mg II detection at a redshift consistent with the foreground galaxy in 17 of the 19 QSOs observed. The first phase of this study (2008B) focused on sub-L_* galaxies (0.2-1L_*) with projected separations \rho=11-35 h^- 1 \rmkpc and at z=0.15-0.35. We propose to continue this programme and probe the gas content of super-L_* galaxies.


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