From Exoplanets to Quasars: Detection of Potential Damped Lyman Alpha Absorbing Galaxies Using Angular Differential Imaging

TL;DR

This study demonstrates the first use of angular differential imaging to directly detect and analyze the host galaxy of a damped Lyman alpha system, revealing candidate galaxies and discussing their likelihood as the DLA host.

Contribution

First application of ADI technique to image DLA host galaxies, providing sensitivity analysis and candidate identification in a quasar field.

Findings

Identified three candidate galaxies within 5" of the quasar.

The most massive candidate is unlikely the host based on impact parameter and redshift.

The DLA host is probably not a luminous, high-mass galaxy.

Abstract

The advantages of angular differential imaging (ADI) has been previously untested in imaging the host galaxies of damped Lyman alpha (DLA) systems. In this pilot study, we present the first application of ADI to directly imaging the host galaxy of the DLA seen towards the quasar J1431+3952. K-band imaging of the field surrounding J1431+3952 was obtained on the Gemini North telescope with the adaptive optics system and a laser guide star. We computed a sensitivity curve that demonstrates the sensitivity of our observations as a function of K-band magnitude, impact parameter and DLA angular size. For an impact parameter of 0.5" (3.4 kpc at the redshift of the absorber) our mass sensitivity is log (M_star/M_sun) ~ 9.2 and drops to ~ 9.0 at separations beyond ~ 6 kpc for the smallest size model galaxy. Three candidate galaxies are identified within 5". Stellar masses were computed from the K-band photometry yielding values of log (M_star/M_sun) ~ 9.9, 9.7 and 11.1 respectively. The likely identification of the absorbing galaxy is discussed, and we conclude that the galaxy with the largest impact parameter and highest stellar mass is unlikely to be the host, based on its inconsistency with the N(HI) impact parameter relation and inconsistent photometric redshift. Whilst we cannot distinguish between the remaining two candidates as the DLA host, we note that despite the low spin temperature and relatively high metallicity of the DLA, the host does not appear to be a particularly luminous (high mass) galaxy.