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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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slide1

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

slide2

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
slide3

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

slide4

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!!!

slide6

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)
slide7

Neighbor MCG+10-22-038

  • 183 kpc from DLA
  • 3.7x108 M
  • d~15 kpc @2x1020 cm-2
  • No previous redshift
  • Optically LSB
slide8

Unknown Dwarf Galaxy #1

  • 123 kpc from DLA
  • MHI = 6.1x108 M
  • d~7 kpc @2x1020 cm-2
  • Previously unknown
  • Optically LSB
slide9

Unknown Dwarf Galaxy #2

  • 161 kpc from DLA
  • MHI = 2.2x108 M
  • d~7 kpc @2x1020 cm-2
  • Previously unknown
  • Optically faint
slide10

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

slide11

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)
slide12

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

slide13

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
slide14

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

slide15

PG 1116

PG 1211

Galaxy distributions along the absorber sightlines

Ton 1542

Mrk 335

slide16

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)
slide17

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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