Globular Cluster Ultraluminous X-ray Sources in the Furthest Early-Type Galaxies

TL;DR

This study identifies and analyzes ultraluminous X-ray sources in globular clusters within the most massive early-type galaxies up to 70 Mpc, revealing their luminosity and spatial distribution characteristics.

Contribution

It presents the first volume-limited survey of GC ULXs in massive early-type galaxies, expanding the known population and comparing their properties with previously identified sources.

Findings

34 ULX candidates found within galaxy effective radii

Approximately 29.4% of ULXs potentially hosted by GCs

GC ULXs peak at luminosities around a few times 10^{39} erg/s

Abstract

Ultraluminous X-ray Sources (ULXs) in globular clusters are low mass X-ray binaries that achieve high X-ray luminosities through a currently uncertain accretion mechanism. Using archival Chandra and Hubble Space Telescope observations, we perform a volume-limited search ($\lesssim$ 70 Mpc) of 21 of the most massive ($>10^{11.5} M_\odot$) early-type galaxies to identify ULXs hosted by globular cluster (GC) candidates. We find a total of 34 ULX candidates above the expected background within 5 times the effective radius of each galaxy, with 10 of these ($\sim29.4\%$) potentially hosted by a GC. A comparison of the spatial and luminosity distributions of these new candidate GC ULXs with previously identified GC ULXs shows that they are similar: both samples peak at $L_X \sim$ a few $\times 10^{39}$ erg/s and are typically located within a few effective radii of their host galaxies.