The radial distribution of X-ray Binaries and Globular Clusters in NGC 4649 and their relation with the local stellar mass density

TL;DR

This study examines how low-mass X-ray binaries and globular clusters are distributed in NGC 4649, revealing their correlation with stellar mass density and highlighting an excess of field LMXBs in the galaxy outskirts.

Contribution

It provides the first detailed analysis of the radial distribution of LMXBs and GCs in NGC 4649, linking their spatial profiles to stellar mass density and galaxy interactions.

Findings

GCs with LMXBs share the same radial distribution as their parent GCs.

Field LMXBs follow the galaxy's V-band light profile within D25.

An excess of field LMXBs is observed in the galaxy's outskirts.

Abstract

We investigate the radial distribution of the low-mass X-ray binary (LMXB) population in the elliptical galaxy NGC 4649, using Chandra and Hubble data to separate the field and globular cluster (GC) populations. GCs with LMXBs have the same radial distribution as the parent red and blue GCs. The radial profile of field LMXBs follows the V-band profile within the D25 of NGC 4649. Using the spatial information provided by our data, we find that the global galaxy-wide relations between cumulative number and luminosity of LMXBs and the integrated stellar mass hold on local scales within D25. An excess of field LMXBs with respect to the V-light is observed in the galaxy's outskirt, which may be partially due to unidentified GC sources or to a rejuvenated field LMXB population caused by past merging interactions.