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HI Properties and Environment of Lyman-alpha Absorbers

HI Properties and Environment of Lyman-alpha Absorbers. Jessica Rosenberg. Harvard-Smithsonian Center for Astrophysics NSF Astronomy and Astrophysics Postdoctoral Fellow.

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HI Properties and Environment of Lyman-alpha Absorbers

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  1. HI Properties and Environment of Lyman-alpha Absorbers 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

  2. 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

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

  4. 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!!!

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

  6. Properties of SBS 1543+593 • HI disk d~27kpc @2x1020 cm-2 • R-band traced to d~12 kpc (Bowen et al. 2001) • MHI=1.2x109 M(Chengalur & Kanekar 2002; Bowen et al. 2001)

  7. Neighbor MCG+10-22-038 • 183 kpc from DLA • 3.7x108 M • d~15 kpc @2x1020 cm-2 • No previous redshift • Optically LSB

  8. Unknown Dwarf Galaxy #1 • 123 kpc from DLA • MHI = 6.1x108 M • d~7 kpc @2x1020 cm-2 • Previously unknown • Optically LSB

  9. Unknown Dwarf Galaxy #2 • 161 kpc from DLA • MHI = 2.2x108 M • d~7 kpc @2x1020 cm-2 • Previously unknown • Optically faint

  10. 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

  11. The HI Environment of a Nearby DLA • HI allows detection of faint/LSB companions • SBS 1543+593 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)

  12. 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? Bryan & Norman Bill Keel/Ned Wright web sites

  13. 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 0.0015-0.002 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

  14. Sep. = 95 kpc Sep. = 342 kpc Sep. = 353 kpc v=8224 km/s MHI = 3.2x108 M v=1889 km/s MHI = 1.4x108 M v=9655 km/s v=9695 km/s Sep. = 616 kpc Sep. = 339 kpc Sep. = 461 kpc v=8126 km/s MHI = 2.2x109 M v=6609 km/s MHI = 1.9x109 M v=8525 km/s MHI = 2.9x109 M v=9335 km/s MHI = 4.6x109 M

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

  16. 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)

  17. The HI Environments of Lyman- Absorbers • HI allows detection of faint/LSB companions • Small scale HI environment only detectable nearby • SBS 1543+593 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 1543+593 is LSB in overdense region (consistent w/ mass) • Ly- forest absorbers mostly, but not exclusively trace galaxy distribution

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