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

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 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

• 183 kpc from DLA

• 3.7x108 M

• d~15 kpc @2x1020 cm-2

• No previous redshift

• Optically LSB

Neighbor MCG+10-22-038

• 123 kpc from DLA

• MHI = 6.1x108 M

• d~7 kpc @2x1020 cm-2

• Previously unknown

• Optically LSB

Unknown Dwarf Galaxy #1

Unknown Dwarf Galaxy #2

• 161 kpc from DLA

• MHI = 2.2x108 M

• d~7 kpc @2x1020 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 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)

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 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

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

Galaxy distributions along the absorber sightlines

PG 1116 PG 1211

Ton 1542 Mrk 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 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