FIR measurements of Ly-$\alpha$ emitters at z$\lesssim$1.0: dust attenuation from PACS-\emph{Herschel}

TL;DR

This study uses Herschel PACS and Spitzer MIPS data to measure the dust content of Ly-alpha emitters at z~0.3 and 1.0, providing direct FIR observations that suggest low-redshift LAEs are dustier than their high-redshift counterparts.

Contribution

First direct FIR measurements of dust content in Ly-alpha emitters at low redshift, revealing potential evolutionary trends in dust attenuation.

Findings

Dust attenuation ranges from 0.75 to 2.5 in A_1200Å for detected LAEs.

Detected LAEs at z~0.3 are dustier than those at z~1.0.

One LAE shows very low dust attenuation, undetected in FIR and MIPS.

Abstract

One remaining open question regarding the physical properties of Ly$\alpha$ emitters (LAEs) is their dust content and its evolution with redshift. The variety of results is large and with those reported by now is difficult to establish clear relations between dust, other fundamental parameters of galaxies (star-formation rate, metallicity or age) and redshift. In this Letter, we report \emph{Herschel} PACS-100$\mu$m, PACS-160$\mu$m and \emph{Spitzer} MIPS-24$\mu$m detections of a sample of spectroscopically GALEX-selected LAEs at z$\sim$0.3 and $\sim$1.0. Five out of ten and one out of two LAEs are detected in, at least, one PACS band at z$\sim$0.3 and $\sim$1.0, respectively. These measurements have a great importance given that they allow us to quantify, for the first time, the dust content of LAEs from direct FIR observations. MIPS-24$\mu$m detections allow us to determine IR properties of the PACS-undetected LAEs. We obtain that mid-IR/FIR detected star-forming (SF) LAEs at z$\sim$0.3 have dust content within 0.75$\lesssim$ $A_{1200\AA}$ $\lesssim$2.0, with a median value of A$_{1200\textrm{\AA}}$$\sim$1.1. This range broadens out to 0.75$\lesssim$ $A_{1200\AA}$ $\lesssim$2.5 when considering those LAEs at z$\sim$1.0. Only one SF LAE is undetected both in MIPS-24$\mu$m and PACS, with $A_{1200\AA}$ $\lesssim$0.75. These results seem to be larger than those reported for high-redshift LAEs and, therefore, although an evolutionary trend is not clearly seen, it could point out that low-redshift LAEs are dustier than high-redshift ones. However, the diverse methods used could introduce a systematic offset in the results.