HI Properties and Environment of Lyman-alpha Absorbers
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Transcript of HI Properties and Environment of Lyman-alpha Absorbers
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Jessica RosenbergHarvard-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
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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
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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
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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!!!
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Gas-rich galaxies exhibit a wide range of properties
even in the local universe
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•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)
Properties of SBS 1543+593
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• 183 kpc from DLA
• 3.7x108 M
• d~15 kpc @2x1020 cm-2
• No previous redshift
• Optically LSB
Neighbor MCG+10-22-038
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• 123 kpc from DLA
• MHI = 6.1x108 M
• d~7 kpc @2x1020 cm-2
• Previously unknown
• Optically LSB
Unknown Dwarf Galaxy #1
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Unknown Dwarf Galaxy #2
• 161 kpc from DLA
• MHI = 2.2x108 M
• d~7 kpc @2x1020 cm-2
• Previously unknown
• Optically faint
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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
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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)
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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?
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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
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v=8224 km/sMHI = 3.2x108 M
v=1889 km/sMHI = 1.4x108 M
v=9655 km/s v=9695 km/s
v=8126 km/sMHI = 2.2x109 M
v=6609 km/sMHI = 1.9x109 M
v=8525 km/sMHI = 2.9x109 M
v=9335 km/sMHI = 4.6x109 M
Sep. = 95 kpc Sep. = 342 kpc Sep. = 353 kpc
Sep. = 616 kpc Sep. = 339 kpc Sep. = 461 kpc
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Galaxy distributions along the absorber sightlines
PG 1116 PG 1211
Ton 1542 Mrk 335
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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)
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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