Ly$\alpha$ Halo Properties and Dust in the Circumgalactic Medium of $z \sim 2$ Star-forming Galaxies

TL;DR

This study uses IFU observations to analyze Lyα halos around star-forming galaxies at z~2-3, revealing how their properties relate to galaxy characteristics and dust content in the circumgalactic medium.

Contribution

It provides new insights into how Lyα halo scale lengths and attenuation depend on galaxy properties, highlighting the role of dust and neutral gas in the CGM.

Findings

Halo scale lengths correlate with stellar mass, age, reddening.

Halo scale lengths anti-correlate with SFR and SFR surface densities.

Resonant Lyα emission experiences greater attenuation than stellar continuum.

Abstract

We present Keck Cosmic Web Imager IFU observations around extended Ly$\alpha$ halos of 27 typical star-forming galaxies with redshifts $2.0 < z < 3.2$ drawn from the MOSFIRE Deep Evolution Field survey. We examine the average Ly$\alpha$ surface-brightness profiles in bins of star-formation rate (SFR), stellar mass ($M_*$), age, stellar continuum reddening, SFR surface density ($\rm \Sigma_{SFR}$), and $\rm \Sigma_{SFR}$ normalized by stellar mass ($\rm \Sigma_{sSFR}$). The scale lengths of the halos correlate with stellar mass, age, and stellar continuum reddening; and anti-correlate with star-formation rate, $\rm \Sigma_{SFR}$, and $\rm \Sigma_{sSFR}$. These results are consistent with a scenario in which the down-the-barrel fraction of Ly$\alpha$ emission is modulated by the low-column-density channels in the ISM, and that the neutral gas covering fraction is related to the physical properties of the galaxies. Specifically, we find that this covering fraction increases with stellar mass, age, and $E(B-V)$; and decreases with SFR, $\rm \Sigma_{SFR}$ and $\rm \Sigma_{sSFR}$. We also find that the resonantly scattered Ly$\alpha$ emission suffers greater attenuation than the (non-resonant) stellar continuum emission, and that the difference in attenuation increases with stellar mass, age, and stellar continuum reddening, and decreases with $\rm \Sigma_{sSFR}$. These results imply that more reddened galaxies have more dust in their CGM.