Author ORCID Identifier:

https://orcid.org/0000-0003-1002-9723

Date of Graduation

9-2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Space & Planetary Sciences (PhD)

Degree Level

Graduate

Department

Space & Planetary Sciences

Advisor/Mentor

Lehmer, Bret

Committee Member

Daniel Kennefick

Second Committee Member

Mark Arnold

Third Committee Member

Pradeep Kumar

Keywords

Astronomy; Astrophysics

Abstract

In this dissertation, we explore how low-mass X-ray binaries (LMXBs) form and evolve in nearby early-type galaxies. We investigate X-ray binary (XRB) luminosity function (XLF) scaling relations for Chandra-detected populations of LMXBs within the footprints of 24 early-type galaxies. Our sample includes Chandra and Hubble Space Telescope observed galaxies at D ≲ 25Mpc that have estimates of the globular cluster (GC) specific frequency (SN) 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 popu- lation XLFs for all galaxies separately and then construct global models characterizing how the LMXB XLFs vary with galaxy stellar mass and SN . We find that our field LMXB XLF models require a component that scales with SN 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 com- ponent 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 SN ≲ 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. We further analyze the host GC properties of LMXBs and find statistically significant trends in host cluster mass and color, consistent with theoretical expectations that metal-rich and massive clusters are more efficient at retaining and forming LMXBs. Finally, in a new case study, we present a broadband X-ray spec- tral energy distribution (SED) for Maffei 1, a nearby elliptical galaxy. Using Chandra and NuSTAR data, we construct a 0.5–20 keV spectral model and fit an absorbed broken power law plus hot gas component. Our results suggest the hard X-ray emission is background- dominated, and that the XRB population is consistent with a mixture of neutron star and black hole binaries. Scaling relations suggest the adopted distance to Maffei 1 may be un- derestimated. Together, these results offer new insights into the formation pathways and emission properties of LMXBs across ETGs, both in population-level scaling and detailed spectral behavior.

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