Revisiting with Chandra the Scaling Relations of the X-ray Emission Components (Binaries, Nuclei and Hot Gas) of Early Type Galaxies

TL;DR

This study analyzes X-ray emission components in 30 early type galaxies using Chandra data, revising scaling relations for LMXBs and hot gas, and exploring their correlations with galaxy properties.

Contribution

It provides new, more precise scaling relations for X-ray binaries and hot gas in early type galaxies, incorporating a broader, gas-poor sample and refined analysis methods.

Findings

Revised LMXB luminosity scaling relation with host galaxy luminosity.

Tighter correlation between hot gas luminosity and temperature.

Steeper LX(gas)-LK relation with increased scatter.

Abstract

We have selected a sample of 30 normal (non-cD) early type galaxies, for all of which optical spectroscopy is available, and which have been observed with Chandra to a depth such to insure the detection of bright low-mass X-ray binaries (LMXBs) with Lx>1e38 erg/s. This sample includes a larger fraction of gas-poor galaxies than previously studied samples, and covers a wide range of stellar luminosity, velocity dispersion, GC specific frequency, and stellar age. We derive X-ray luminosities (or upper limits) from the different significant X-ray components of these galaxies: nuclei, detected and undetected LMXBs, coronally active binaries (ABs), cataclysmic variables (CVs), and hot gas. The ABs and CVs contribution is estimated from the Lx-LK scaling relation of M31 and M32. The contribution of undetected LMXBs is estimated both by fitting the spectra of the unresolved X-ray emission and by extrapolating the LMXB X-ray luminosity function. The results for the nuclei are consistent with those discussed by Pellegrini (2010). We derive a revised scaling relation between the integrated X-ray luminosity of LMXBs in a galaxy and the LK luminosity of the host galaxy: Lx(LMXB)/LK ~ 1e29 erg s-1 LK-1 with 50% 1sigma rms; moreover, we also obtain a tighter LX(LMXB)/LK - SN relation than previously published. We revisit the relations between hot gas content and other galaxy parameters. finding a steeper LX(gas)-LK relation with larger scatter than reported in the literature. We find a positive correlation between the luminosity and temperature of the hot ISM, significantly tighter than reported by earlier studies.[abridged]