Accretion-driven Sources in Spatially Resolved Lyα Emitters

Abstract

Ly α emission is a standard tracer of starburst galaxies at high redshift. However, a number of local Ly α emitters (LAEs) are X-ray sources, suggesting a possible origin of Ly α photons other than young, hot stars, and which may be active at much later ages relative to the parent starburst. Resolved, nearby LAEs offer the opportunity to discriminate between diffuse X-ray emission arising from supernova-heated gas, high-mass X-ray binaries (HMXBs), or low-luminosity active galactic nuclei (LLAGN). We examine archival X-ray imaging from Chandra and XMM-Newton for 11 galaxies with spatially resolved Ly α imaging to determine the luminosity, morphology, and spectral hardness of the X-ray sources. The data are consistent with 9 of the 12, bright Ly α sources being driven by luminous, > X-ray sources. Half of the eight Chandra sources are unresolved. The data suggest that nuclear activity, whether from LLAGN or nuclear starbursts, may play an important role in Ly α emission. Our results also suggest a significant link between Ly α emission and HMXBs, ultraluminous X-ray sources, and/or LLAGN, which would imply that Ly α may be generated over timescales 1–2 orders of magnitude longer than produced by photoionization from OB stars. This highlights a critical need to quantify the relative contributions of different sources across cosmic time, to interpret Ly α observations and the resulting properties of distant galaxies.