The Expected Detection of Dust Emission from High-Redshift Lyman Alpha Galaxies

TL;DR

This paper predicts the detectability of dust emission from high-redshift Lyman alpha galaxies using ALMA and SMA, providing insights into their dust content and evolution compared to Lyman break galaxies.

Contribution

It offers the first direct emission-based predictions of dust detection in high-redshift Lyman alpha galaxies, comparing their dust properties with Lyman break galaxies.

Findings

Approximately 39% of Lyman alpha galaxies can be detected in dust emission with current instruments.

Lyman break galaxies are about 60% more likely to be detected, indicating they are dustier.

Direct dust emission detection can improve understanding of galaxy evolution and dust content.

Abstract

Recent results have shown that a substantial fraction of high-redshift Lyman alpha galaxies contain considerable amounts of dust. This implies that Lyman alpha galaxies are not primordial, as has been thought in the past. However, this dust has not been directly detected in emission; rather it has been inferred based on extinction estimates from rest-frame ultraviolet (UV) and optical observations. This can be tricky, as both dust and old stars redden galactic spectra at the wavelengths used to infer dust. Measuring dust emission directly from these galaxies is thus a more accurate way to estimate the total dust mass, giving us real physical information on the stellar populations and interstellar medium (ISM) enrichment. New generation instruments such as the Atacama Large Millimeter Array (ALMA) and Sub-Millimeter Array (SMA), should be able to detect dust emission from some of these galaxies in the sub-mm. Using measurements of the UV spectral slopes, we derive far-infrared flux predictions for of a sample of 23 z > 4 Lyman alpha galaxies. We find that in only a few hours, we can detect dust emission from 39 +/- 22% of our Lyman alpha galaxies. Comparing these results to those found from a sample of 21 Lyman break galaxies (LBGs), we find that LBGs are on average 60% more likely to be detected than Lyman alpha galaxies, implying that they are more dusty, and thus indicating an evolutionary difference between these objects. These observations will provide better constraints on dust in these galaxies than those derived from their UV and optical fluxes alone. Undeniable proof of dust in these galaxies could explain the larger than expected Lyman alpha equivalent widths seen in many Lyman alpha galaxies today.