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Unmasking Damped Ly a Absorbing Galaxies:

Unmasking Damped Ly a Absorbing Galaxies:. Hsiao-Wen Chen (MIT Center for Space Research) Ken Lanzetta (Stony Brook University) Rob Kennicutt (Steward Observatory) Michael Rauch (Carnegie Observatories). Damped Ly  Absorbers (DLAs) N(HI) ≥ 2 x 10 20 cm -2.

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Unmasking Damped Ly a Absorbing Galaxies:

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  1. Unmasking Damped Lya Absorbing Galaxies: Hsiao-Wen Chen (MIT Center for Space Research) Ken Lanzetta (Stony Brook University) Rob Kennicutt (Steward Observatory) Michael Rauch (Carnegie Observatories)

  2. Damped Ly Absorbers (DLAs)N(HI) ≥ 2 x 1020 cm-2 High-redshift analog of local HI galaxies Abell 2218 at z = 0.18 (Zwaan et al. 2002)

  3. Proximity to a glaring, background QSO --

  4. Proximity to a glaring, background QSO -- challenging to find the DLA galaxy 5”

  5. z ≤ 1 Sample • 23 known DLAs in available UV spectra of QSOs • 14 confirmed DLA galaxies • 4 candidate DLA galaxies; 3 unidentified

  6. Morphology of z < 1 DLA galaxies z = 0.101 z = 0.473 z = 0.613 5” z = 0.525 z = 0.524 z = 0.221 10” 5” 18”

  7. Spectral properties of z < 1 DLA galaxies Chen, Kennicutt, & Rauch (2005)

  8. Utility of the DLA galaxy sample • To study the neutral gaseous extent of intermediate-redshift galaxies • To understand the nature of DLA galaxies by examining their luminosity distribution function: dwarf dominated vs. a typical field sample • To investigate the metal content of DLA galaxies: missing metal?

  9. HI extent of intermediate-z galaxies Chen & Lanzetta (2003)

  10. HI cross section of distant galaxies Chen & Lanzetta (2003)

  11. Luminosity distribution of z < 1 DLA galaxies N(z)  ∫  (L)  (L) dL < 40% of DLAs at z < 1 arise in galaxies Of luminosity LB < 0.1 LB* Chen & Lanzetta (2003)

  12. Chemical enrichment history in HI • low metal • large scatter Prochaska et al. (2003)

  13. Abundance profiles of the z < 1 DLA galaxies Z (r) = ( 0.02 +/- 0.20) - ( 0.041 +/- 0.012 )r / kpc Chen, Kennicutt, & Rauch (2005)

  14. Abundance profiles of the z < 1 DLA galaxies Z (r) = ( 0.02 +/- 0.20) - ( 0.041 +/- 0.012 )r / kpc sZ = 0.7 dex Chen, Kennicutt, & Rauch (2005)

  15. Summary: • Intermediate redshift galaxies possess extended neutral gas tor = 24 - 30 h-1 kpc. • The luminosity distribution function of the DLA galaxies is consistent with expectations, if they are drawn from the knownfield galaxy population. • Abundance profiles of DLA galaxies can be characterized by a metallicity gradient ofDZ/Dr = -0.041 +/- 0.012 dex/kpc. • The predicted N(HI)-weighted mean metallicity in the DLA population is<Z> = -0.50 +/- 0.07over 100 random lines of sight.

  16. Conclusions: • DLA galaxies at z < 1 have a range of luminosity, morphology, and spectral properties, representative of the field galaxy population. An especially large contribution from dwarf galaxies is not necessary. • The low metal content and large scatter observed in the DLAs can arise naturally as a combination of gas cross-section selection and metallicity gradients commonly seen in local disk galaxies.

  17. Gamma-ray burst afterglows as probes w/ J. X. Prochaska & J. S. Bloom HST/NICMOS (+4 d) 36”

  18. Gamma-ray burst afterglows as probes w/ J. X. Prochaska & J. S. Bloom • GRB host-DLA NICMOS/F160W HST/NICMOS (+1 yr) 10” ACS/F814W 36” 10” • Classic DLA

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