Chandra Survey of Nearby Highly-Inclined Disk Galaxies I: X-ray Measurements of Galactic Coronae

TL;DR

This study systematically analyzes Chandra X-ray observations of 53 nearby highly-inclined disk galaxies to characterize their hot gaseous coronae, providing a large uniform database for understanding galactic halo properties.

Contribution

First comprehensive uniform analysis of diffuse X-ray emission in a diverse sample of highly-inclined disk galaxies, including new measurements and a large database for coronal studies.

Findings

Characterized coronal scale heights and luminosities across the sample.

Presented diffuse X-ray emission data for 20 galaxies for the first time.

Discussed potential biases and corrections affecting coronal property measurements.

Abstract

We present a systematical analysis of the Chandra observations of 53 nearby highly-inclined (i>60 degree) disk galaxies to study the coronae around them. This sample covers a broad range of galaxy properties: e.g., about three orders of magnitude in the SFR and more than two orders of magnitude in the stellar mass. The Chandra observations of the diffuse soft X-ray emission from 20 of these galaxies are presented for the first time. The data are reduced in a uniform manner, including the excision/subtraction of both resolved and unresolved stellar contributions. Various coronal properties, such as the scale height and luminosity, are characterized for all the sample galaxies. For galaxies with high enough counting statistics, we also examine the thermal and chemical states of the coronal gas. We note on galaxies with distinct multi-wavelength characteristics which may affect the coronal properties. The uniformly processed images, spectra, and brightness profiles, as well as the inferred hot gas parameters, form a large X-ray database for studying the coronae around nearby disk galaxies. We also discuss various complications which may cause biases to this database and their possible corrections or effects, such as the uncertainty in the thermal and chemical states of hot gas, the different galactic disk inclination angles, the presence of AGN, and the contribution of the emission from charge exchange at interfaces between hot and cool gases. Results from a detailed correlation analysis are presented in a companion paper, to gain a more comprehensive statistical understanding of the origin of galactic coronae.