The Chandra local volume survey: The x-ray point-source catalog of NGC300

Abstract

We present the source catalog of a new Chandra ACIS-I observation of NGC300 obtained as part of the Chandra Local Volume Survey. Our 63 ks exposure covers 88% of the D 25 isophote (R 6.3kpc) and yields a catalog of 95 X-ray point sources detected at high significance to a limiting unabsorbed 0.35-8keV luminosity of 1036ergs-1. Sources were cross-correlated with a previous XMM-Newton catalog, and we find 75 "X-ray transient candidate" sources that were detected by one observatory, but not the other. We derive an X-ray scale length of 1.7 ± 0.2kpc and a recent star formation rate of 0.12 M yr-1 in excellent agreement with optical observations. Deep, multi-color imaging from the Hubble Space Telescope, covering 32% of our Chandra field, was used to search for optical counterparts to the X-ray sources, and we have developed a new source classification scheme to determine which sources are likely X-ray binaries, supernova remnants, and background active galactic nucleus candidates. Finally, we present the X-ray luminosity functions (XLFs) at different X-ray energies, and we find the total NGC300 X-ray point-source population to be consistent with other late-type galaxies hosting young stellar populations (≲ 50 Myr). We find that XLF of sources associated with older stellar populations has a steeper slope than the XLF of X-ray sources coinciding with young stellar populations, consistent with theoretical predictions. © 2012. The American Astronomical Society. All rights reserved.