A new 21-cm absorber identified with an $L\sim L^{\star }$ galaxy

Abstract

We present Giant Metrewave Radio Telescope (GMRT) observations of redshifted 21-cm absorption from the $z=0.437$ metal line absorption system towards PKS 1243-072. HI absorption is clearly detected; the absorption profile has a velocity spread of $\sim 20$ km/s. Detection of 21-cm absorption indicates that the absorber has an HI column density large enough to be classified as a damped Lyman-$\alpha$ system. Follow up ground based optical imaging and spectroscopy allow us to identify the absorber with an $L\sim L^{\star }$ galaxy at an impact parameter of $\sim 9.8$ kpc from the line of sight to the QSO. The absorbing galaxy is unusual in that it has bright emission lines. On the basis of the optical spectrum we are unable to uniquely classify the galaxy since its emission line ratios lie in the transition region between starburst and Seyfert II type spectra.

5 pages, 3 figures. Accepted for publication in Astronomy & Astrophysics

References in corpus (4)

• Implications of 21cm observations for damped Ly-$\alpha$ systems
• HI 21cm absorption in low z damped lyman-alpha systems
• Two New Low Redshift 21cm Absorbers
• Lost and Found: The Damped Lyman Alpha Absorbers in the QSO OI 363

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• Imaging and spectroscopy of galaxies associated with two z~0.7 damped Lyman-alpha absorption systems
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• High spin temperatures at large impact parameters: Ionisation in the outskirts of galaxies
• From Exoplanets to Quasars: Detection of Potential Damped Lyman Alpha Absorbing Galaxies Using Angular Differential Imaging