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X-Ray Binary Luminosity Function Scaling Relations in Elliptical Galaxies: Evidence for Globular Cluster Seeding of Low-mass X-Ray Binaries in Galactic Fields

Lehmer, Bret D.; Ferrell, Andrew P.; Doore, Keith; Eufrasio, Rafael T.; Monson, Erik B.; Alexander, David M.; Basu-Zych, Antara; Brandt, William N.; Sivakoff, Gregory R.; Tzanavaris, Panayiotis; Yukita, Mihoko; Fragos, Tassos; Ptak, Andrew

X-Ray Binary Luminosity Function Scaling Relations in Elliptical Galaxies: Evidence for Globular Cluster Seeding of Low-mass X-Ray Binaries in Galactic Fields Thumbnail


Authors

Bret D. Lehmer

Andrew P. Ferrell

Keith Doore

Rafael T. Eufrasio

Erik B. Monson

Antara Basu-Zych

William N. Brandt

Gregory R. Sivakoff

Panayiotis Tzanavaris

Mihoko Yukita

Tassos Fragos

Andrew Ptak



Abstract

We investigate X-ray binary (XRB) luminosity function (XLF) scaling relations for Chandra-detected populations of low-mass XRBs (LMXBs) within the footprints of 24 early-type galaxies. Our sample includes Chandra and Hubble Space Telescope observed galaxies at $D\lesssim 25$ Mpc that have estimates of the globular cluster (GC) specific frequency (S N ) reported in the literature. As such, we are able to directly classify X-ray-detected sources as being coincident with unrelated background/foreground objects, GCs, or sources that are within the fields of the galaxy targets. We model the GC and field LMXB population XLFs for all galaxies separately and then construct global models characterizing how the LMXB XLFs vary with galaxy stellar mass and S N . We find that our field LMXB XLF models require a component that scales with S N and has a shape consistent with that found for the GC LMXB XLF. We take this to indicate that GCs are "seeding" the galactic field LMXB population, through the ejection of GC LMXBs and/or the diffusion of the GCs in the galactic fields themselves. However, we also find that an important LMXB XLF component is required for all galaxies that scales with stellar mass, implying that a substantial population of LMXBs are formed "in situ," which dominates the LMXB population emission for galaxies with S N lesssim 2. For the first time, we provide a framework quantifying how directly associated GC LMXBs, GC-seeded LMXBs, and in situ LMXBs contribute to LMXB XLFs in the broader early-type galaxy population.

Journal Article Type Article
Acceptance Date Apr 20, 2020
Online Publication Date Jun 10, 2020
Publication Date 2020-06
Deposit Date Jul 8, 2020
Publicly Available Date Jul 8, 2020
Journal Astrophysical Journal Supplement
Print ISSN 0067-0049
Electronic ISSN 1538-4365
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 248
Issue 2
Article Number 31
DOI https://doi.org/10.3847/1538-4365/ab9175
Public URL https://durham-repository.worktribe.com/output/1266885

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Copyright Statement
© 2020. The American Astronomical Society. All rights reserved.






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