CLUES to the past: Local Group progenitors amongst high-redshift Lyman Break Galaxies

TL;DR

This study uses advanced simulations to predict the properties and observability of the early progenitors of the Local Group galaxies at high redshifts, linking them to current deep survey detections.

Contribution

It provides detailed predictions of the physical properties and brightness of Milky Way and Andromeda progenitors at z=6-8, connecting high-redshift galaxies to local group origins.

Findings

Most massive progenitors have UV magnitudes -17 to -18, near current survey detection limits.

Progenitors at z=7 have stellar masses around 10^7.5-8 solar masses.

Predicted UV slopes are between -2.4 and -2.5.

Abstract

We use state-of-the-art numerical simulations to explore the observability and the expected physical properties of the progenitors of the local group galaxies at z=6-8, within 1 billion years of the big bang. We find that the most massive progenitors of the Milky Way (MW) and Andromeda (M31) at z=6 and 7 are predicted to have absolute UV continuum magnitudes between -17 and -18, suggesting that their analogues lie close to the detection limits of the deepest near-infrared surveys conducted to date (i.e. HST WFC3/IR UDF12). This in turn confirms that the majority of currently known z=6-8 galaxies are expected to be the seeds of present-day galaxies which are more massive than L* spirals. We also discuss the properties of the local-group progenitors at these early epochs, extending down to absolute magnitudes M_UV = -13. The most massive MW/M31 progenitors at z=7 have stellar masses of about 10^7.5-8 solar masses, stellar metallicities between 3 and 6% of the solar value, and predicted observed UV continuum slopes between -2.4 and -2.5.