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XMMOMCAT - XMM-Newton OM Object Catalog

HEASARC
Archive

Overview

The Optical Monitor Catalog of serendipitous sources (OMCat) contains entries for every source detected in the publicly available XMM-Newton Optical Monitor (OM) images taken in the imaging mode. Since the OM records data simultaneously with the X-ray telescopes on XMM-Newton, it typically produces images in one or more near-UV/optical bands for every pointing of the observatory. As of the beginning of 2014, the data in the public archive covered roughly 0.5% of the sky in 3425 fields. The OMCat is not dominated by sources previously undetected at other wavelengths; the bulk of objects have optical counterparts. However, the OMCat can be used to extend optical or X-ray spectral energy distributions for known objects into the ultraviolet, to study at higher angular resolution objects detected with GALEX, or to find high-Galactic-latitude objects of interest for UV spectroscopy.

Differences between the current OMCat and the previous version of the OMCat (which was designated as XMMOMOBJ) are improved coordinates, improved quality flags, and a reduced number of spurious sources. The OM reduction was done with the standard ESAS software, with post-processing to apply the coordinate corrections in a more consistent manner. There is a major change in the way the data are represented in the table. In the previous XMMOMOBJ table a separate row was generated for each filter. In the current XMMOMCAT table each observation of each object generates only a single row regardless of how many filters were used. Unused filters have nulls while filters where the object is not detected have nulls for the detection parameters but a non-zero value for exposure.

The table includes information for each filter and averaged information for the object as a whole. Only filters in which the object was detected are used in the averages. The parameters in this table comprise two sets: parameters describing the detection overall including id's and mean values, and values specific to the individual bands. There are three possible situations for the band data:

(1) If there was no exposure in that band, then all fields for that band will be null.

(2) If there was some exposure in the band but the object was not detected in that band, then the exposure field will give the actual exposure, but all of the other fields for that band will be null.

(3) If the object was detected, then all of the fields for the band should be filled in.

The filters included are V, B, U, UVW1, UVM2, UVW2 and white (i.e., unfiltered).


Catalog Bibcode

2008PASP..120..740K

References

OMCat: Catalogue of Serendipitous Sources Detected with the XMM-Newton
Optical Monitor
    Kuntz, K.D., Harrus, I.M., McGlynn, T.A., Mushotzky, R.F., Snowden S.L.
   <Publ. Astron. Soc. Pac., 120, 740-758 (2008)>
   =2008PASP..120..740K

Provenance

The original table XMMOMOBJ was created by the HEASARC in March 2008, based on a table supplied by the authors. The new XMMOMCAT version was generated in February 2014 using a program which concatenated the objects detected in processing each observation.

Data Products

A single dynamically generated quicklook data product is associated with this catalog. At each object's location a small cutout from the full OM image is made for each OM filters used during the obsid. The cutouts are arranged in a horizontal strip in a fixed order. Each filter is shown at a specific location in the strip and if no data was taken in that filter that area is left blank. Cutouts will be given for filters were there was any observing time even if this object was not detected in that filter. A label is given for each filter for which there is a cutout.

The image cutouts are only 19x19 pixels. To enhance visibility each pixel is replicated as a 5x5 block. So in the generated PNG each cutout is 95x95 pixels.


Parameters

Source_ID
A unique identifier for each object in this catalog. It is a concatenation of the observation identifier and the source index (obj_num).

ObsID
A unique XMM-Newton observation identifier made up of the proposal number, target number of the proposal, and exposure number of the target.

Obj_Num
A unique target counter for the OM source within the observation specified by the obsid. Thus, the combination of obsid and obj_num uniquely identifies an entry in this table. In this table it is simply the index of the source within the FITS table.

Time
The start time of the observation. This is stored internally as a Modified Julian Date (MJD), but the HEASARC's archive interfaces usually convert it into an ISO 8601 format date.

RA
The Right Ascension of the OM source in the selected equinox. In most cases, the Right Ascension is the mean of all measurements of the source corrected to the USNO-B frame.

Dec
The Declination of the OM source in the selected equinox. In most cases, the Declination is the mean of all measurements of the source corrected to the USNO-B frame.

LII
The Galactic Longitude of the OM source.

BII
The Galactic Latitude of the OM source.

Error_Radius
The position error of the OM source, in arcseconds.

RMS_Res
The RMS residuals in the fit of the OM source with the USNO Catalog, in arcseconds.

USNO_RA
The Right Ascension of the matching USNO object in the selected equinox.

USNO_Dec
The Declination of the matching USNO object in the selected equinox.

Major_Axis
If the source is extended, the semi-major axis of the OM source averaged over all bands in which the source was detected, in arcseconds.

Minor_Axis
If the source is extended, the mean semi-minor axis of the OM source in the bands in which the source was detected.

Position_Angle
If the source is extended, the position angle of the major axis of the OM source averaged over all bands in which the source was detected, in degrees.

Q_Flag
The quality flag parameter (called Q_FLAG in the reference paper) is set to 0 for OM sources with good data quality. The quality flag is combined over all bands in which the source is detected. The following positive values are used to flag compromised source quality (notice that they can be used additively):

      1 = bad pixel
      2 = source on possible read-out streak
      4 = source on possible smoke ring
      8 = source on possible star diffraction spike
     16 = source likely affect by mod-8 pattern
     32 = source near bright source
     64 = source within central enhanced region
  

C_Flag
This flag parameter (called C_FLAG in the reference paper) is set to 0 for OM sources which are unconfused. The confusion flag is combined over all bands in which the source is detected. The following positive values are used to flag different types of confusion (notice that they can be used additively):

      1 = one or more sources lie within a radius of 6 to 1 unbinned pixels
      2 = one or more sources lie within a radius of 6 unbinned pixels
      4 = source near an image edge
      8 = point source lies partly or entirely within an extended source region
  

E_Flag
This flag parameter (called E_FLAG in the reference paper) is set to 0 for OM sources which are non-extended, and to 1 for extended sources. The flag parameter is the maximum value for the bands in which the source was detected. (I.e., the source is marked as extended if it is extended in any detected wavelength.)

V_Rate
The V-band count rate, in ct/s.

V_Rate_Error
The uncertainty in the V-band count rate, in ct/s.

V_SNR
The statistical significance of the V-band detection.

V_Mag
The V-band instrumental magnitude.

V_Mag_Error
The uncertainty in the V-band magnitude.

V_Major_Axis
If extended, the length of the major axis in the V-band detection.

V_Minor_Axis
If extended, the length of the minor axis in the V-band detection.

V_Position_Angle
If extended, the position angle of the major axis in the V-band detection.

V_Q_Flag
The V-band quality flag. Flag values are defined in the q_flag parameter above.

V_C_Flag
The V-band confusion flag. Flag values are defined in the c_flag parameter above.

V_E_Flag
The V-band extension flag. Set to 1 if the object is extended is this band.

V_Exposure
The V-band exposure time. The exposure time is set if any exposure was made in this wavelength, even if the object was not detected.

B_Rate
The B-band count rate, in ct/s.

B_Rate_Error
The uncertainty in the B-band count rate, in ct/s.

B_SNR
The statistical significance of the B-band detection.

B_Mag
The B-band instrumental magnitude.

B_Mag_Error
The uncertainty in the B-band magnitude.

B_Major_Axis
If extended, the length of the major axis in the B-band detection.

B_Minor_Axis
If extended, the length of the minor axis in the B-band detection.

B_Position_Angle
If extended, the position angle of the major axis in the B-band detection.

B_Q_Flag
The B-band quality flag. Flag values are defined in the q_flag parameter above.

B_C_Flag
The B-band confusion flag. Flag values are defined in the c_flag parameter above.

B_E_Flag
The B-band extension flag. Set to 1 if the object is extended is this band.

B_Exposure
The B-band exposure time. The exposure time is set if any exposure was made in this wavelength, even if the object was not detected.

U_Rate
U-band count rate, in ct/s.

U_Rate_Error
The uncertainty in the U-band count rate, in ct/s.

U_SNR
The statistical significance of the U-band detection.

U_Mag
U-band instrumental magnitude.

U_Mag_Error
The uncertainty in the U-band magnitude.

U_Major_Axis
If extended, the length of the major axis in the U-band detection.

U_Minor_Axis
If extended, the length of the minor axis in the U-band detection.

U_Position_Angle
If extended, the position angle of the major axis in the U-band detection.

U_Q_Flag
The U-band quality flag. Flag values are defined in the q_flag parameter above.

U_C_Flag
The U-band confusion flag. Flag values are defined in the c_flag parameter above.

U_E_Flag
The U-band extension flag. Set to 1 if the object is extended is this band.

U_Exposure
The U-band exposure time. The exposure time is set if any exposure was made in this wavelength, even if the object was not detected.

UVW1_Rate
The UVW1-band count rate, in ct/s.

UVW1_Rate_Error
The uncertainty in the UVW1-band count rate, in ct/s.

UVW1_SNR
The statistical significance of the UVW1-band detection.

UVW1_Mag
UVW1-band instrumental magnitude.

UVW1_Mag_Error
The uncertainty in the UVW1-band magnitude.

UVW1_Major_Axis
If extended, the length of the major axis in the UVW1-band detection.

UVW1_Minor_Axis
If extended, the length of the minor axis in the UVW1-band detection.

UVW1_Position_Angle
If extended, the position angle of the major axis in the UVW1-band detection.

UVW1_Q_Flag
The UVW1-band quality flag. Flag values are defined in the q_flag parameter above.

UVW1_C_Flag
The UVW1-band confusion flag. Flag values are defined in the c_flag parameter above.

UVW1_E_Flag
The UVW1-band extension flag. Set to 1 if the object is extended is this band.

UVW1_Exposure
The UVW1-band exposure time. The exposure time is set if any exposure was made in this wavelength, even if the object was not detected.

UVM2_Rate
The UVM2-band count rate, in ct/s.

UVM2_Rate_Error
The uncertainty in the UVM2-band count rate, in ct/s.

UVM2_SNR
The statistical significance of the UVM2-band detection.

UVM2_Mag
UVM2-band instrumental magnitude.

UVM2_Mag_Error
The uncertainty in the UVM2-band magnitude.

UVM2_Major_Axis
If extended, the length of the major axis in the UVM2-band detection.

UVM2_Minor_Axis
If extended, the length of the minor axis in the UVM2-band detection.

UVM2_Position_Angle
If extended, the position angle of the major axis in the UVM2-band detection.

UVM2_Q_Flag
The UVM2-band quality flag. Flag values are defined in the q_flag parameter above.

UVM2_C_Flag
The UVM2-band confusion flag. Flag values are defined in the c_flag parameter above.

UVM2_E_Flag
The UVM2-band extension flag. Set to 1 if the object is extended is this band.

UVM2_Exposure
The UVM2-band exposure time. The exposure time is set if any exposure was made in this wavelength, even if the object was not detected.

UVW2_Rate
The UVW2-band count rate, in ct/s.

UVW2_Rate_Error
The uncertainty in the UVW2-band count rate, in ct/s.

UVW2_SNR
The statistical significance of the UVW2-band detection.

UVW2_Mag
The UVW2-band instrumental magnitude.

UVW2_Mag_Error
The uncertainty in the UVW2-band magnitude.

UVW2_Major_Axis
If extended, the length of the major axis in the UVW2-band detection.

UVW2_Minor_Axis
If extended, the length of the minor axis in the UVW2-band detection.

UVW2_Position_Angle
If extended, the position angle of the major axis in the UVW2-band detection.

UVW2_Q_Flag
The UVW2-band quality flag. Flag values are defined in the q_flag parameter above.

UVW2_C_Flag
The UVW2-band confusion flag. Flag values are defined in the c_flag parameter above.

UVW2_E_Flag
The UVW2-band extension flag. Set to 1 if the object is extended is this band.

UVW2_Exposure
The UVW2-band exposure time. The exposure time is set if any exposure was made in this wavelength, even if the object was not detected.

White_Rate
The white-band count rate, in ct/s.

White_Rate_Error
The uncertainty in the white-band count rate, in ct/s.

White_SNR
The statistical significance of the white-band detection.

White_Mag
The white-Band instrumental magnitude.

White_Mag_Error
The uncertainty in the white-band magnitude.

White_Major_Axis
If extended, the length of the major axis in the white-band detection.

White_Minor_Axis
If extended, the length of the minor axis in the white-band detection.

White_Position_Angle
If extended, the position angle of the major axis in the white-band detection.

White_Q_Flag
The white-band quality flag. Flag values are defined in the q_flag parameter above.

White_C_Flag
The white-band confusion flag. Flag values are defined in the c_flag parameter above.

White_E_Flag
The white-band extension flag. Set to 1 if the object is extended is this band.

White_Exposure
The white-band exposure time. The exposure time is set if any exposure was made in this wavelength, even if the object was not detected.


Contact Person

Questions regarding the XMMOMCAT database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 5-Mar-2014