The Stellar Mass, Star Formation Rate and Dark Matter Halo Properties of LAEs at $z\sim2$

TL;DR

This study characterizes the stellar, star formation, and dark matter properties of $z\, ext{~2}$ LAEs, revealing their low halo masses, high star formation efficiency, and potential evolution into LMC-like halos by $z=0$.

Contribution

It provides the first comprehensive analysis combining SED fitting and clustering to determine properties of a large LAE sample at $z\sim2$, highlighting their low halo masses and star formation efficiency.

Findings

LAEs have an average stellar mass of $10.2\times 10^8 M_\odot$.

Dark matter halo mass is estimated at $4.0\times 10^{10} M_\odot$, lower than previous estimates.

LAEs exhibit high star formation efficiency and are likely progenitors of LMC-like halos.

Abstract

We present average stellar population properties and dark matter halo masses of $z \sim 2$ \lya emitters (LAEs) from SED fitting and clustering analysis, respectively, using $\simeq$ $1250$ objects ($NB387\le25.5$) in four separate fields of $\simeq 1$ deg$^2$ in total. With an average stellar mass of $10.2\, \pm\, 1.8\times 10^8\ {\mathrm M_\odot}$ and star formation rate of $3.4\, \pm\, 0.4\ {\mathrm M_\odot}\ {\rm yr^{-1}}$, the LAEs lie on an extrapolation of the star-formation main sequence (MS) to low stellar mass. Their effective dark matter halo mass is estimated to be $4.0_{-2.9}^{+5.1} \times 10^{10}\ {\mathrm M_\odot}$ with an effective bias of $1.22^{+0.16}_{-0.18}$ which is lower than that of $z \sim 2$ LAEs ($1.8\, \pm\, 0.3$), obtained by a previous study based on a three times smaller survey area, with a probability of $96\%$. However, the difference in the bias values can be explained if cosmic variance is taken into account. If such a low halo mass implies a low HI gas mass, this result appears to be consistent with the observations of a high \lya escape fraction. With the low halo masses and ongoing star formation, our LAEs have a relatively high stellar-to-halo mass ratio (SHMR) and a high efficiency of converting baryons into stars. The extended Press-Schechter formalism predicts that at $z=0$ our LAEs are typically embedded in halos with masses similar to that of the Large Magellanic Cloud (LMC); they will also have similar SHMRs to the LMC, if their SFRs are largely suppressed after $z \sim 2$ as some previous studies have reported for the LMC itself.