|
Description
This table contains results from an XMM-Newton and Spitzer survey of the part of the Orion A cloud south of the Orion Nebula, the 'Survey of Orion A with XMM-Newton and Spitzer (SOXS)'. The goal of SOXS is to detect the relatively bright X-ray sources in the Orion A cloud and complete the census of more evolved YSOs in this region. These stars represent a sample of cloud members chosen with minimal a priori bias toward their IR properties. This XMM-Newton survey includes the Lynds 1641 (L1641) dark cloud, a region of the Orion A cloud with very few massive stars and hence a relatively low ambient UV flux, and the region around the O9 III star iota Orionis. In addition to proprietary data, the authors used archival XMM data of the Orion Nebula Cluster (ONC) to extend their analysis to a major fraction of the Orion A cloud. They have detected 1060 X-ray sources with more than 4.5-sigma significance in L1641 and the iota Ori region. About 94% of the sources have Two Micron All Sky Survey (2MASS) and Spitzer counterparts, 204 and 23 being Class II and Class I or protostar objects, respectively. In addition, the authors have identified 489 X-ray sources as counterparts to Class III candidates, given they are bright in X-rays and appear as normal photospheres at mid-IR wavelengths. The remaining 205 X-ray sources are likely distant active galactic nuclei (AGN) or other galactic sources not related to Orion A. The authors find that Class III candidates appear more concentrated in two main clusters in L1641. The first cluster of Class III stars is found toward the northern part of L1641, concentrated around iota Ori. The stars in this cluster are more evolved than those in the Orion Nebula. The authors estimate a distance of 300-320 pc for this cluster showing that it is in the foreground of the Orion A cloud. Another cluster rich in Class III stars is located in L1641 South and appears to be a slightly older cluster embedded in the Orion A cloud. Furthermore, other evolved Class III stars are found north of the ONC toward NGC 1977. The SOXS survey is composed of seven specifically proposed ~ 50 ks XMM-Newton fields, south of the ONC, to which the authors added four archival fields in the same region. The archival fields are centered on iota Orionis, V380 Ori, and V883 Ori, respectively (see Fig. 1 and Table 1 of the reference paper for more details of the X-ray observations). This HEASARC table contains the contents of Table 2 (1060 X-ray detected sources in the fields S1 - S10 listed in Table 1 of the reference paper), Table 3 (best-fit spectral parameters for the 232 brightest of these X-ray sources) and Table 4 (list of 1041 IR counterparts to the X-ray sources) from the reference paper. Some X-ray sources have no identified counterparts (16 of them in fact lie outside of the FOV of the Spitzer observations), most have a single counterpart, and a small number have 2 or even 3 IR counterparts within the 5 arcseconds matching radius used. For X-ray sources with more than 1 IR counterpart, we have added entries for the additional counterparts (71 in total), repeating the X-ray information in such cases. Thus, this HEASARC table contains 1131 (1060 + 71) entries corresponding to the 1060 X-ray source detections. To make its contents easier to visualize, the HEASARC has added a a parameter ir_match which lists the counterpart number for the entry: If there is no identified IR counterpart, ir_match is set to 0, for the first listed IR counterpart to 1, for the second and third, to 2 and 3, respectively. Thus, if the user wants to reduce the table back to a pure list of X-ray sources and their primary IR counterparts, they should search the table selecting ir_match < 2. This table was created by the HEASARC in August 2013 based on the electronic versions of Tables 2 and 3 from the original reference paper (2013ApJ...768...99P) and Table 4 from the erratum (2013ApJ...773...80P), which were all obtained from the ApJ web site. This is a service provided by NASA HEASARC .
|
