HI Properties and Environment
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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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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

Collaborators: Stephen Schneider, Jennifer Posson-Brown, David Bowen, Mary Putman, John Stocke, Todd Tripp, Emma Ryan-Weber


Hi properties and environment of lyman alpha absorbers

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


Hi properties and environment of lyman alpha absorbers

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


Hi properties and environment of lyman alpha absorbers

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!!!


Hi properties and environment of lyman alpha absorbers

Gas-rich galaxies exhibit a wide range of properties

even in the local universe


Hi properties and environment of lyman alpha absorbers

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)


Hi properties and environment of lyman alpha absorbers

Neighbor MCG+10-22-038

  • 183 kpc from DLA

  • 3.7x108 M

  • d~15 kpc @2x1020 cm-2

  • No previous redshift

  • Optically LSB


Hi properties and environment of lyman alpha absorbers

Unknown Dwarf Galaxy #1

  • 123 kpc from DLA

  • MHI = 6.1x108 M

  • d~7 kpc @2x1020 cm-2

  • Previously unknown

  • Optically LSB


Hi properties and environment of lyman alpha absorbers

Unknown Dwarf Galaxy #2

  • 161 kpc from DLA

  • MHI = 2.2x108 M

  • d~7 kpc @2x1020 cm-2

  • Previously unknown

  • Optically faint


Hi properties and environment of lyman alpha absorbers

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


Hi properties and environment of lyman alpha absorbers

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)


Hi properties and environment of lyman alpha absorbers

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


Hi properties and environment of lyman alpha absorbers

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


Hi properties and environment of lyman alpha absorbers

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


Hi properties and environment of lyman alpha absorbers

PG 1116

PG 1211

Galaxy distributions along the absorber sightlines

Ton 1542

Mrk 335


Hi properties and environment of lyman alpha absorbers

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)


Hi properties and environment of lyman alpha absorbers

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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