Galaxy main sequence and properties of low-mass Lyman-alpha Emitters towards reionisation viewed by VLT/MUSE and JWST/NIRCam

Abstract

Faint, star-forming galaxies likely play a dominant role in cosmic reionisation. Strides have been made in recent years to characterise these populations at high redshifts ($z>3$). Now for the first time, with JWST photometry beyond 1$\mu m$ in the rest frame, we can derive accurate stellar masses and position these galaxies on the galaxy main sequence. We seek to assess the place of 96 individual Lyman-alpha emitters (LAEs) selected behind the A2744 lensing cluster with MUSE spectroscopy on the galaxy main sequence. We also compare derived stellar masses to Lyman-alpha luminosities and equivalent widths to better quantify the relationship between the Lyman-alpha emission and the host galaxy. These 96 LAEs lie in the redshift range $2.9<z<6.7$, and their range of masses extends down to $10^6{\mathrm{M}}_{\odot }$ (over half with ${\mathrm{M}}_{\star }<10^8{\mathrm{M}}_{\odot }$). We use the JWST/NIRCam and HST photometric catalogs from the UNCOVER project, giving us excellent wavelength coverage from $450\mathrm{nm}$ to $4.5\mu m$. We find a main sequence relation for these low mass LAEs of the form: $\log \mathrm{SFR}=(0.88\pm 0.07-0.030\pm 0.027\times t)\log {\mathrm{M}}_{\star }-(6.31\pm 0.41-0.08\pm 0.37\times t)$. This is in approximate agreement with best-fits of previous collated studies, however, with a steeper slope and a higher normalisation. This indicates that low-mass LAEs towards the epoch of reionisation lie above typical literature main sequence relations derived at lower redshift and higher masses. Additionally, comparing our results to UV-selected samples, we see that while low-mass LAEs lie above these typical main sequence relations, they are likely not singular in this respect at these masses and redshifts. While low-mass galaxies have been shown to play a significant role in cosmic reionisation, our results point to no special position for LAEs in this regard.

10 pages, 5 figures, accepted for publication in Astronomy and Astrophysics