Physics Master of Science Thesis Defense by Sara Gholamhoseinian
LIB 314
: Zoom
Dr. Sarah Caudill
scaudill@umassd.edu
https://umassd.zoom.us/j/97464617175?pwd=1sGVbiZIj8rZZtEWLohylHQtoZQlt1.1
Topic: Modeling Spin-Dependent Detectability in Gravitational-Wave Astronomy with a Calibrated Normalizing Flow
Abstract:
Population inference from gravitational-wave catalogs requires an accurate selection function, the probability that a source with given parameters is detected, because errors in this correction propagate directly into the inferred astrophysical distributions. The standard semianalytic approach of Finn and Chernoff estimates detectability from the leading-order post-Newtonian amplitude, which depends on chirp mass, luminosity distance, and orientation but carries no dependence on component spin. Real waveforms are not spin-blind: aligned spin modifies the inspiral through spin-orbit coupling, delays merger via the orbital hang-up, and raises the accumulated signal-to-noise ratio. A spin-blind selection function therefore misrepresents the detectability of spinning binaries and the sensitive volume available to spinning populations. This thesis quantifies that bias with a calibrated conditional normalizing flow trained on a large synthetic population of binary black hole signals, generated with a full precessing, higher-harmonic waveform model for the Advanced LIGO-Virgo network at design sensitivity. Rather than classifying detection at a fixed threshold, the flow models the full conditional signal-to-noise distribution and remains evaluable at any threshold. Benchmarked against the Finn-Chernoff baseline, the flow recovers a strong dependence of sensitive volume on effective spin, spanning a factor of roughly 2.6 between strongly anti-aligned and strongly aligned systems, whereas the baseline stays spin-independent by construction. This discrepancy is a spin-selection bias that must be accounted for in spin-population inference as catalogs continue to grow.
Advisor(s): Dr. Sarah Caudill, Department of Physics, (scaudill@umassd.edu)
Committee members: Dr. Robert Fisher, Department of Physics and Dr. Scott Field, Department of Mathematics
Note: All PHY Graduate Students are encouraged to attend.