2025/04/22 by Luan Luan, Q. Daniel Wang, Luan, Luan +1 · 1 citation
Medicine · Physics and Astronomy · #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #High Energy Astrophysical Phenomena (astro-ph.HE) #Medical Imaging Techniques and Applications #Nuclear Physics and Applications #X-ray Spectroscopy and Fluorescence Analysis
paper · pdf · doi:10.48550/arxiv.2504.15641
openalex publication_date 2025/04/22 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
X-ray observations can be used to effectively probe the galactic ecosystem, particularly its hot and energetic components. However, existing X-ray studies of nearby star-forming galaxies are limited by insufficient data statistics and a lack of suitable spectral modeling to account for X-ray emission and absorption geometry. We present results from an X-ray spectral study of M51 using 1.3-Ms Chandra data, the most extensive for such a galaxy. This allows the extraction of diffuse X-ray emission spectra from spiral arm phase-dependent regions using a logarithmic spiral coordinate system. A hierarchical Bayesian approach analyzes these spectra, testing models from simple 1-T hot plasma to those including distributed hot plasma and X-ray-absorbing cool gas. We recommend a model fitting the spectra well, featuring a galactic corona with a lognormal temperature distribution and a disk with mixed X-ray emissions and absorption. In this model, only half of the coronal emission is subject to internal absorption. The best-fit absorbing gas column density is roughly twice that inferred from optical extinction of stellar light. The temperature distribution shows a mean temperature of ∼ 0.1 keV and an average one-dex dispersion that is enhanced on the spiral arms. The corona's radiative cooling might balance the mechanical energy input from stellar feedback. These results highlight the effectiveness of X-ray mapping of the corona and cool gas in spiral galaxies.