Discovery of a Low-redshift Damped Lyα System in a Foreground Extended Disk Using a Starburst Galaxy Background Illuminator

Christopher M. Dupuis, Sanchayeeta Borthakur, Mansi Padave, Rolf A. Jansen, Rachael M. Alexandroff, Timothy M. Heckman

Research output: Contribution to journalArticlepeer-review

Abstract

We present the discovery of a low-redshift damped Lyα (DLA) system in the spectrum of background starburst galaxy SDSS J111323.88+293039.3 (z = 0.17514). The DLA is at an impact parameter of ρ = 36 kpc from the star-forming galaxy, SDSS J111324.08+293051.2 (z = 0.17077). We measure an H i column density of N(H i) = 3.47 1020 cm-2 along with multiple low-ionization species such as N i, N ii, Si ii, C ii, and Si iii. We also make an estimate of the covering fraction to be 0.883, giving us a limiting size of the DLA to be A DLA ≥ 3.3 kpc2. Assuming a uniform column density over the entire DLA system, we estimate its mass to be M DLA ≥ 5.3 106 M o˙. The extended illuminator and the low redshift of this DLA give us the unique opportunity to characterize its nature and the connection to its host galaxy. We measure a velocity offset of +131 km s-1 from the systemic velocity of the host for the DLA. This velocity is -84 km s-1 from the projected rotation velocity of the host galaxy as measured using a newly constructed rotation curve. Based on the size of the host galaxy, the H i column density, and the gas kinematics, we believe this DLA is tracing the warm neutral gas in the H i disk of the foreground galaxy. Our detection adds to a small set of low-redshift DLAs that have confirmed host galaxies, and is the first to be found using an extended background source.

Original languageEnglish (US)
Article number103
JournalAstrophysical Journal
Volume907
Issue number2
DOIs
StatePublished - Feb 1 2021

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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