Characterising the Circum-Galactic Medium of Damped Lyman-$\alpha$ Absorbing Galaxies

TL;DR

This study combines multi-wavelength observations of five galaxies associated with Damped Lyman-alpha absorbers at redshifts 1-2 to characterize their stellar, gas, and metallic properties, revealing diverse baryon fractions and complex morphologies.

Contribution

It provides new detailed measurements of the stellar, gas, and metallic content of DLA host galaxies using combined HST, IFU, and ALMA data, highlighting their structural complexity and baryon distribution.

Findings

Wide range of baryon fractions (7-100%) in host galaxies.

Gas fractions vary between 3-56%, consistent with galaxy main sequence.

Most galaxies exhibit clumpy structures and signs of tidal interactions.

Abstract

Gas flows in and out of galaxies through their circumgalactic medium (CGM) are poorly constrained and direct observations of this faint, diffuse medium remain challenging. We use a sample of five $z$ $\sim$ 1-2 galaxy counterparts to Damped Lyman-$\alpha$ Absorbers (DLAs) to combine data on cold gas, metals and stellar content of the same galaxies. We present new HST/WFC3 imaging of these fields in 3-5 broadband filters and characterise the stellar properties of the host galaxies. By fitting the spectral energy distribution, we measure their stellar masses to be in the range of log($M_*$/$\text{M}_{\odot}$) $\sim$ 9.1$-$10.7. Combining these with IFU observations, we find a large spread of baryon fractions inside the host galaxies, between 7 and 100 percent. Similarly, we find gas fractions between 3 and 56 percent. Given their star formation rates, these objects lie on the expected main sequence of galaxies. Emission line metallicities indicate they are consistent with the mass-metallicity relation for DLAs. We also report an apparent anti-correlation between the stellar masses and $N$(HI), which could be due to a dust bias effect or lower column density systems tracing more massive galaxies. We present new ALMA observations of one of the targets leading to a molecular gas mass of log($M_{\rm mol}$/$\text{M}_{\odot}$) < 9.89. We also investigate the morphology of the DLA counterparts and find that most of the galaxies show a clumpy structure and suggest ongoing tidal interaction. Thanks to our high spatial resolution HST data, we gain new insights in the structural complexity of the CGM.