Chandra ACIS Survey of M33 (ChASeM33): The First Look Source Catalog

Paul Plucinsky (SAO) , Benjamin Williams (UW), Knox S. Long (STScI), Terrance J. Gaetz (SAO), Manami Sasaki (SAO), Wolfgang Pietsch (MPE), Ralph Tuellmann (SAO), Randall K. Smith (JHU/GSFC), and the ChASeM33 team

We present a source catalog from the Chandra ACIS Survey of M33 (ChASeM33): A Deep Survey of the Nearest Face-on Spiral Galaxy. The 1.4 Ms survey covers the galaxy out to R 18 arcmin ( 4 kpc). These data provide the most intensive, high spatial resolution assessment of the X-ray source populations available for the confused inner regions of M33. Mosaic images of the ChASeM33 observations show several hundred individual X-ray sources as well as soft diffuse emission from the hot interstellar medium. Bright, extended emission surrounds the nucleus and is also seen from the giant HII regions NGC604 and IC131. Fainter extended emission and numerous individual sources appear to trace the inner spiral structure. The initial source catalog, arising from 2/3 of the expected survey data, includes 394 sources significant at the 3 sigma confidence level or greater, down to a limiting luminosity (absorbed) of 1.6e35 ergs (0.35 - 8.0 keV). The hardness ratios of the sources separate those with soft, thermal spectra such as supernova remnants from those with hard, non-thermal spectra such as X-ray binaries and background active galactic nuclei. Emission extended beyond the Chandra point spread function is evident in 23 of the 394 sources. Cross-correlation of the ChASeM33 sources against previous catalogs of X-ray sources in M33 results in matches for the vast majority of the brighter sources and shows 28 ChASeM33 sources within 10 arcsec of supernova remnants identified by prior optical and radio searches. Support for this work was provided by NASA through Chandra Award Number G06-7073A and contract NAS8-03060