Master Thesis defense by Meghana Killi

Title: Compact LAEs at High-z: Feature or Anomaly

Abstract:

Young star-forming galaxies in the early Universe can be identified by their intense Hydrogen Lyman-α (Lyα) emission that is bright enough to be projected like a beacon nearly all the way across the Universe. This radiation provides valuable insight into the formation of the first galaxies and their evolution over cosmic time. The goal of this project was to take advantage of this illuminating emission line to understand the lives of the smallest of these star-forming galaxies. In this talk, I will present a summary of our work.

We identify a sample of 17 bright, yet extremely compact (∼ 1 kpc size) Lyα emitters (LAEs) at z ∼ 4−7 selected from a parent sample of 1060 Lyman-break galaxies (LBGs) observed in (Hubble Space Telescope) HST data in 4 of the 5 CANDELS fields, and investigate various reasons for their compactness.

We make relative size measurements by fitting Sérsic profiles to the Lyα line and UV continuum morphology, and find that the sub-sample of LAEs is generally more compact than the parent sample of LBGs. Within the sub-sample, Lyα morphology is more compact than UV continuum, contrary to the expectation of extended halos.

We also fit templates to the spectral energy distributions (SEDs) of the objects based on photometric flux measurements from the Skelton catalog (Skelton et al. 2014). Here, we find that the sub-sample star-formation rates and stellar masses are generally higher than the parent sample.

Based on our results and findings from literature, we tentatively conclude that the compact nature is partly a true physical feature of high-z LAEs and partly due to observational limitations. In other words, it is both a feature and an anomaly.

Supervisor
Darach Watson, Niels Bohr Insitute, DAWN

Thesis Advisor
Gabriel Brammer, Niels Bohr Insitute, DAWN

Censor:
Thomas Greve, DTU SPACE/Niels Bohr Institute, DAWN