The AstroSat UV Deep Field South II: A diverse set of Lyman-continuum leakers at $z\sim1$

TL;DR

This study reports the discovery of five new Lyman-continuum leaker candidates at redshifts around 1, revealing diverse properties and spatial offsets, which challenge existing understanding of LyC photon escape mechanisms.

Contribution

It presents the identification and characterization of a new, diverse set of LyC leakers at z~1, expanding the known sample and providing insights into their physical properties and spatial structures.

Findings

Detected 5 new LyC leaker candidates at z~1.

Escape fractions range from 14% to 85%.

Some galaxies show spatial offsets between LyC emission and UV continuum.

Abstract

We report the detection of 5 newly identifed Lyman-continuum (LyC) leaker candidates at redshifts 0.99-1.42 in the AstroSat UV Deep Field South F154W image. We derive physical properties of these galaxies using a combination of spectral-energy distribution fitting and information from publicly available spectra. The estimated escape fraction of these objects vary from 14-85\% after accounting for the IGM attenuation. With only about a dozen known leakers at these redshifts, these detections significantly raise the fraction of LyC leakers in this redshift range. High-resolution HST UV imaging reveals that a subset of the galaxies in our sample have blue star-forming structures that are likely associated with harder ionizing sources. We find tentative evidence that the LyC emission is spatially offset from the non-ionizing UV continuum centers of these galaxies. The integrated properties of these galaxies, such as the UV continuum slope, dust attenuation, stellar mass, and $[\text{O III}] \lambda 5007/ [\text{O II}] \lambda 3727$ ratios, make them atypical compared to known LyC leakers. The leakage of LyC photons from these systems presents a compelling challenge.