Jessica Rosenberg Harvard-Smithsonian Center for Astrophysics NSF Astronomy and Astrophysics Postdoctoral Fellow Collaborators: Stephen Schneider, Jennifer Posson-Brown, David Bowen, Mary Putman, John Stocke, Todd Tripp, Emma Ryan-Weber

21cm Observations: Properties and Environments of Lyman-  Absorbers What does the HI look like in and around absorbers? HI 21cm good tracer of the gas Can identify gas-rich LSB galaxies Selection function comparable to damped absorption line selection

Rosenberg & Schneider, ApJ 2003, 585, 256 Blind HI selection analogous to DLA selection HI cross-section strongly correlated with HI mass HI-rich Galaxies are DLA Analogs at z=0

Use local gas-rich galaxies to determine properties of DLAs at z=0 Rosenberg, Schneider, Posson-Brown 2005 Low luminosity galaxies are significant contributors to the DLA population!!!

Gas-rich galaxies exhibit a wide range of properties even in the local universe

HI disk 20 cm -2 R-band traced to d~12 kpc (Bowen et al. 2001) M HI =1.2x10 9 M  (Chengalur & Kanekar 2002; Bowen et al. 2001) Properties of SBS

183 kpc from DLA 3.7x10 8 M  d~15 20 cm -2 No previous redshift Optically LSB Neighbor MCG

123 kpc from DLA M HI = 6.1x10 8 M  d~7 20 cm -2 Previously unknown Optically LSB Unknown Dwarf Galaxy #1

Unknown Dwarf Galaxy #2 161 kpc from DLA M HI = 2.2x10 8 M  d~7 20 cm -2 Previously unknown Optically faint

A Large LSB Disk Galaxy Living in a Rich Environment Large HI disk survives despite near neighbors 20% LSBs live in populous environments (Bothun et al. 1993) LSB, but still traces the large scale mass distribution Slices are 6º deep

The HI Environment of a Nearby DLA HI allows detection of faint/LSB companions SBS is large LSB disk with at least 3 companions An LSB and still traces the large scale structure Small scale environment only detectable nearby This environment might be more common at high-z HI-rich groups possible scenario for low metallicities in sightlines with multiple DLAs (Lopez & Ellison 2003)

Bill Keel/Ned Wright web sites Bryan & Norman The HI Environment of the Lyman-  Forest How does filamentary picture relate to galaxies? Where is the dense HI gas with respect to the absorbers? What is the connection between absorbers and galaxies?

The HI Environment of the Lyman-  Forest (the quick taste) HI survey at Arecibo around 16 low redshift absorbers Full project: 48 low-z absorbers at Arecibo, Parkes, ATCA 31.2’ x 31.2’ fields down to Jy/beam 8 new galaxies detected (Arecibo observations) All but one detection >100 kpc from sightline No evidence for gas-rich dwarfs directly responsible for absorption

v=8224 km/s M HI = 3.2x10 8 M  v=1889 km/s M HI = 1.4x10 8 M  v=9655 km/sv=9695 km/s v=8126 km/s M HI = 2.2x10 9 M  v=6609 km/s M HI = 1.9x10 9 M  v=8525 km/s M HI = 2.9x10 9 M  v=9335 km/s M HI = 4.6x10 9 M  Sep. = 95 kpcSep. = 342 kpcSep. = 353 kpc Sep. = 616 kpcSep. = 339 kpc Sep. = 461 kpc

Galaxy distributions along the absorber sightlines PG 1116PG 1211 Ton 1542Mrk 335

Lyman-  Forest -- Galaxy Association Several new gas-rich galaxies identified No gas-rich galaxies identified at the absorber position Many of the absorbers follow galaxy distribution – Nearest to sightline 95 kpc – 8 of 16 absorbers within 500 kpc of a galaxy Some absorbers at large separations from galaxies – Separation up to 3.5 Mpc Varying degrees of sensitivity, deeper optical also needed (in some cases it exists)

The HI Environments of Lyman-  Absorbers HI allows detection of faint/LSB companions Small scale HI environment only detectable nearby SBS is large LSB disk with at least 3 companions HI-rich groups possible scenario for low metallicities in sightlines with multiple DLAs (Lopez & Ellison 2003) SBS is LSB in overdense region (consistent w/ mass) Ly-  forest absorbers mostly, but not exclusively trace galaxy distribution