|
Description
This table contains some of the results from a Chandra ACIS observation of the stellar populations in and around the M17 H II region. The field reveals 886 sources (listed in the present table) with observed X-ray luminosities (uncorrected for absorption) between ~ 29.3 erg s<sup>-1</sup> < log L<sub>X</sub> < 32.8 erg s<sup>-1</sup>, 771 of which have stellar counterparts in infrared images. Spectral analysis results for the 598 brightest X-ray sources which have photometric significance of 2.0 or greater) are also given herein. For 546 of the X-ray sources, the fits used the "wabs(apec)" thermal plasma model in XSPEC assuming scaled 0.3 times solar photospheric abundances, while for the other 52 X-ray sources for which either the thermal model poorly described the data or required nonphysical parameters and the X-ray source was not identified with a known stellar counterpart, the fits used the "wabs(powerlaw)" model in XSPEC. In addition to the comprehensive tabulation of X-ray source properties, several other results were presented in the reference paper: 1. The X-ray luminosity function is calibrated to that of the Orion Nebula Cluster population to infer a total population of roughly 8000-10,000 stars in M17, one-third lying in the central NGC 6618 cluster. 2. About 40% of the ACIS sources are heavily obscured with A<sub>V</sub> > 10 mag. Some are concentrated around well-studied star-forming regions -- IRS 5/UC1, the Kleinmann-Wright Object, and M17-North -- but most are distributed across the field. As previously shown, star formation appears to be widely distributed in the molecular clouds. X-ray emission is detected from 64 of the hundreds of Class I protostar candidates that can be identified by near- and mid-infrared colors. These constitute the most likely protostar candidates known in M17. 3. The spatial distribution of X-ray stars is complex: in addition to the central NGC 6618 cluster and well-known embedded groups, we find a new embedded cluster (designated M17-X), a 2 pc long arc of young stars along the southwest edge of the M17 H II region, and 0.1 pc substructure within various populations. These structures may indicate that the populations are dynamically young. 4. All (14/14) of the known O stars but only about half (19/34) of the known B0-B3 stars in the M17 field are detected. These stars exhibit the long-reported correlation between X-ray and bolometric luminosities of L<sub>X</sub> ~ 10<sup>-7</sup> L<sub>bol</sub>. While many O and early-B stars show the soft X-ray emission expected from microshocks in their winds or moderately hard emission that could be caused by magnetically channeled wind shocks, six of these stars exhibit very hard thermal plasma components (kT > 4 keV) that may be due to colliding wind binaries. More than 100 candidate new OB stars are found, including 28 X-ray detected intermediate- and high-mass protostar candidates with infrared excesses. 5. Only a small fraction (perhaps 10%) of X-ray selected high- and intermediate-mass stars exhibit K-band-emitting protoplanetary disks, providing further evidence that inner disks evolve very rapidly around more massive stars. This table was created by the HEASARC in December 2007 based on electronic versions of Tables 1, 2, 3, 4 and 5 of the reference paper which were obtained from the electronic ApJ web site. This is a service provided by NASA HEASARC .
|
