XMMSSCGPS - XMM-Newton Survey Science Center Survey of the Galactic Plane

Overview

Many different classes of X-ray sources contribute to the Galactic landscape at high energies. Although the nature of the most luminous X-ray emitters is now fairly well understood, the population of low-to-medium X-ray luminosity (L_X = 10²⁷ - 10³⁴ erg/s) sources remains much less studied, our knowledge being mostly based on the observation of local members. The advent of wide-field and high-sensitivity X-ray telescopes such as XMM-Newton now offers the opportunity to observe this low-to-medium L_X population at large distances. This study reports the results of a Galactic plane survey conducted by the XMM-Newton Survey Science Centre (SSC). Beyond its astrophysical goals, this survey aims at gathering a representative sample of identified X-ray sources at low latitude that can be used later on to statistically identify the rest of the serendipitous sources discovered in the Milky Way.

The survey is based on 26 XMM-Newton observations, obtained at |b| < 20 degrees, distributed over a large range in Galactic longitudes and covering a summed area of 4 deg². The flux limit of this survey is 2 x 10^-15 erg/cm²/s in the soft (0.5 - 2 keV) band and 1 x 10^-14 erg/cm²/s in the hard (2 - 1 2keV) band. A total of 1319 individual X-ray sources have been detected. Using optical follow-up observations supplemented by cross-correlation with a large range of multi-wavelength archival catalogs, the authors identify 316 X-ray sources. This constitutes the largest group of spectroscopically identified low-latitude X-ray sources at this flux level. The majority of the identified X-ray sources are active coronae with spectral types in the range A to M at maximum distances of ~1 kpc. The number of identified active stars increases towards late spectral types, reaching a maximum at K. Using infrared colors, the authors classify 18% of the stars as giants. The observed distributions of F_X/F_V, X-ray and infrared colors indicates that their sample is dominated by a young (100 Myr) to intermediate (600 Myr) age population with a small contribution of close main-sequence or evolved binaries. The authors find other interesting objects such as cataclysmic variables (d ~ 0.6 - 2 kpc), low-luminosity high-mass stars (likely belonging to the class of Gamma-Cas-like systems, d ~ 1.5 - 7 kpc), T Tauri and Herbig-Ae stars. A handful of extragalactic sources located in the highest Galactic latitude fields could be optically identified. For the 20 fields observed with the EPIC pn camera, the authors have constructed log N(>S) - log S curves in the soft and hard bands. In the soft band, the majority of the sources are positively identified with active coronae and the fraction of stars increases by about one order of magnitude from b = 60 degrees to b = 0 degrees at an X-ray flux of 2 x 10^-14 erg/cm²/s. The hard band is dominated by extragalactic sources, but there is a small contribution from a hard Galactic population formed by CVs, HMXB candidates or Gamma-Cas-like systems and by some active coronal stars that are also detected in the soft band. At b = 0 degrees, the surface density of hard sources brighter than 1 x 10^-13 erg/cm²/s steeply increases by one order of magnitude from l = 20 degrees to the Galactic center region (l = 0.9 degrees).

This HEASARC table contains 739 X-ray sources detected in the 26 different fields observed in this study and listed in Tables 8 - 33, inclusive, of the reference paper. These 739 sources have the best XMM quality, i.e. the summary flag sum_flag which contains information about flags set automatically and manually for a given source is zero, meaning that there are no negative flags for the source detection, have either a 2MASS, USNO, GSC, or SDSS counterpart, whatever the probability of identification is, or have some information via SIMBAD or the authors own imaging or spectroscopic observations. For each X-ray source, its X-ray parameters are summarized, listing the pn count rates, and information on optical and infrared counterparts is provided. The properties of the 26 target fields are given in Table 1 of the reference paper, along with the breakdown of source classes in each field.

Catalog Bibcode

2013A&A...553A..12N

References

The XMM-Newton SSC survey of the Galactic Plane.
    Nebot Gomez-Moran A., Motch C., Barcons X., Carrera F.J., Ceballos M.T.,
    Cropper M., Grosso N., Guillout P., Herent O., Mateos S., Michel L.,
    Osborne J.P., Pakull M., Pineau F.-X., Pye J.P., Roberts T.P., Rosen S.R.,
    Schwope A.D., Watson M.G., Webb N.
    <Astron. Astrophys. 553, A12 (2013)>
    =2013A&A...553A..12N        (SIMBAD/NED BibCode)

Provenance

This table was created by the HEASARC in May 2013 based on CDS Catalog J/A+A/553/A12, the 26 files table8.dat to table33.dat, inclusive.

HEASARC Implementation

As noted above, this table contains the merged contents of 26 separate tables from the reference paper, each of which contains the source list for an XMM-Newton observation. The HEASARC has created a parameter xmm_field_name which contains the name of the target field so as to allow the user to select sources on a per-field basis. The original tables did not contain the X-ray source positions, so the HEASARC has added the source positions as given in the 2XMMi-DR3 Catalog.

Parameters

Name
The name of the source as given in the 2XMMi-DR3 Catalog, viz. '2XMM JHHMMSS.s+DDMMSS'.

XMM_Field_Name
The name of the target field in which the source was detected. The properties of the target fields are listed in Table 1 of the reference paper.

RA
The Right Ascension of the XMM-Newton source in the selected equinox. The original tables did not contain the X-ray source positions, so the HEASARC has added the source positions as given in the 2XMMi-DR3 Catalog.

Dec
The Declination of the XMM-Newton source in the selected equinox. The original tables did not contain the X-ray source positions, so the HEASARC has added the source positions as given in the 2XMMi-DR3 Catalog.

LII
The Galactic Longitude of the XMM-Newton source.

BII
The Galactic Latitude of the XMM-Newton source.

Error_Radius
The 90% confidence error radius of the XMM-Newton source position, in arcseconds.

SB_Count_Rate
The XMM-Newton EPIC pn count rate in the soft energy band (0.5 - 2.0 keV), in ct/s. Notice that the original tables in the reference paper used units of ct/ks for the count rates. For 6 of the 26 fields, there are only MOS detections and thus no pn count rates are available for sources in these fields.

SB_Count_Rate_Error
The uncertainty in the XMM-Newton EPIC pn count rate in the soft energy band (0.5 - 2.0 keV), in ct/s.

HB_Count_Rate
The XMM-Newton EPIC pn count rate in the hard energy band (2.0 - 12.0 keV), in ct/s. Notice that the original tables in the reference paper used units of ct/ks for the count rates. For 6 of the 26 fields, there are only MOS detections and thus no pn count rates are available for sources in these fields.

HB_Count_Rate_Error
The uncertainty in the XMM-Newton EPIC pn count rate in the hard energy band (2.0 - 12.0 keV), in ct/s.

TwoMASS_Name
The name of the 2MASS association with the XMM-Newton source, using the cross-correlation method described in Section 4.1 of the reference paper, e.g., matching within a radius corresponding to a 99.7% (3-sigma) completeness, which for a 2-dimensional Gaussian distribution corresponds to 3.44 times the 1-sigma combined positional error.

XMM_2MASS_Offset
The angular distance Between the X-Ray and 2MASS source positions, in arcseconds

Probability_2MASS_ID
The probability P_id of the 2MASS source being the true counterpart of the XMM-Newton source, based on the total number of observed counterparts compared to the number of estimated spurious associations.

Ks_Mag
The 2MASS K_s magnitude of the counterpart to the X-ray source.

GSC_Name
The name of the GSC2.3 association with the XMM-Newton source, using the cross-correlation method described in Section 4.1 of the reference paper, e.g., matching within a radius corresponding to a 99.7% (3-sigma) completeness, which for a 2-dimensional Gaussian distribution corresponds to 3.44 times the 1-sigma combined positional error.

XMM_GSC_Offset
The angular distance Between the X-Ray and GSC2.3 source positions, in arcseconds

Probability_GSC_ID
The probability P_id of the GSC2.3 source being the true counterpart of the XMM-Newton source, based on the total number of observed counterparts compared to the number of estimated spurious associations.

Vmag
The GSC2.3 V magnitude of the counterpart to the X-ray source.

USNO_Name
The name of the USNO-B1.0 association with the XMM-Newton source, using the cross-correlation method described in Section 4.1 of the reference paper, e.g., matching within a radius corresponding to a 99.7% (3-sigma) completeness, which for a 2-dimensional Gaussian distribution corresponds to 3.44 times the 1-sigma combined positional error.

XMM_USNO_Offset
The angular distance Between the X-Ray and USNO-B1.0 source positions, in arcseconds

Probability_USNO_ID
The probability P_id of the USNO-B1.0 source being the true counterpart of the XMM-Newton source, based on the total number of observed counterparts compared to the number of estimated spurious associations.

R2_Mag
The USNO-B1.0 R₂ magnitude of the counterpart to the X-ray source.

Broad_Type
The broad classification of the source, as follows:

              Star = active coronal sources
                EG = extragalactic sources
                CV = cataclysmic variables
               TTS = T Tauri stars
              HMXB = high mass X-ray binaries.

Spect_Type
The spectral type of the source, if stellar. The luminosity class corresponds to that derived in Section 6.1 of the reference paper.

Class_Note
Note Concerning the Source Classification, coded as follows:

             sp = spectroscopic identified sources
              s = objects with SIMBAD identification
          image = sources found to be extended in the optical images

Class
The HEASARC Browse/Xamin object classification, based on the values of the spect_type and/or broad_type parameters.

Contact Person

Questions regarding the XMMSSCGPS database table can be addressed to the HEASARC Help Desk.

Page Author: Browse Software Development Team
Last Modified: Monday, 16-Sep-2024 17:37:25 EDT