Appendix 7. Combined Calibration Scan Images and Source Lists

3. Extracted Source Lists

d. Extracted Source Table Format

The following table contains brief descriptions of the entries in the 2MASS combined calibration scan extracted source lists. The lists contain the positions, aperture photometry, uncertainties, quality flags and cross-references to entries in the All-Sky Point and Extended Source Catalogs. A separate table is provided for each of the 35 2MASS calibration fields.

A source was required to be detected on both the combined north-going and south-going images to be included in the extracted source database for a field. The positions and photometry provided are the average values measured on the north- and south-going combined images.

Construction of the combined calibration scan images is described in A7.2, and the source extraction procedure is described in A7.3. The calibration field combined images and source databases can be retrieved using the on-line ftp interface at A7.4.

The columns in the following table are:

Column Name: The parameter name in the extracted source table. Click on this to go to the section of the Explanatory Supplement where the derivation and/or usage of that parameter is described in more detail.

Format: The ascii-equivalent format of the field in the source list, expressed in "C" readable notation. Note that some fields contain null values that will require special handling when parsing tables.

Units: The units of the parameter. A value of "---" in this column means that the parameter is dimensionless.

nulls: A "yes" in this column means that this parameter can be null in the extracted source table. A "no" means that there will always be a value in this column in the table.

Description: A brief description of the parameter and its values.

Column Name Format Units nulls Description

id %6d --- no Numerical identifier for the source within this calibration field. The identifier is assigned sequentially for each extraction in order of increasing (i.e. south-to-north) declination.
Note: This identifier is unique only within the extracted source table for a given calibration field.

ra %10.6f deg no Average right ascension of the extracted source in the north- and south-going combined images.
Note: Positions of sources extracted from the combined calibration scan images can be systematically offset from the 2MASS All-Sky PSC because position reconstruction for the calibration scan data was done with respect to the USNOA-2.0 catalog rather than Tycho 2 (A4.4b and A7.5).

dec %10.6f deg no Average declination of the extracted source in the north- and south-going combined images.
Note: Positions of sources extracted from the combined calibration scan images can be systematically offset from the 2MASS All-Sky PSC because position reconstruction for the calibration scan data was done with respect to the USNOA-2.0 catalog rather than Tycho 2 (A4.4b and A7.5).

dra %5.3f arcsec no Standard deviation of the average right ascension of source measured on combined north- and south-going scan images.

ddec %5.3f arcsec no Standard deviation of the average declination of source measured on combined north- and south-going scan images.

j_m %6.3f mag yes Inverse variance-weighted mean J magnitude of the source measured on the north- and south-going scan combined images. The individual magnitudes are measured in a 4" radius aperture. The background sky reference is measured in an annular region with inner radius of 24" and outer radius of 30".
If this source was detected in the J-band on only one of the images, then this is the J magnitude from the one detection. A null value in this column means that the source was not detected on either of the J-band combined images.

j_msig %5.3f mag yes Gaussian-reduced J-band uncertainty of the the source formed from the uncertainties measured on the north- and south-going combined images. If this source was detected in the J-band on only one of the images, then this is the J-band uncertainty from the one detection. A null value in this column means that the source was not detected on either of the J-band combined images.

h_m %6.3f mag yes Inverse variance-weighted mean H magnitude of the source measured on the north- and south-going scan combined images. The individual magnitudes are measured in a 4" radius aperture. The background sky reference is measured in an annular region with inner radius of 24" and outer radius of 30".
If this source was detected in the H-band on only one of the images, then this is the H magnitude from the one detection. A null value in this column means that the source was not detected on either of the H-band combined images.

h_msig %5.3f mag yes Gaussian-reduced H-band uncertainty of the the source formed from the uncertainties measured on the north- and south-going combined images. If this source was detected in the H-band on only one of the images, then this is the H-band uncertainty from the one detection. A null value in this column means that the source was not detected on either of the H-band combined images.

k_m %6.3f mag yes Inverse variance-weighted mean K_s magnitude of the source measured on the north- and south-going scan combined images. The individual magnitudes are measured in a 4" radius aperture. The background sky reference is measured in an annular region with inner radius of 24" and outer radius of 30".
If this source was detected in the K_s-band on only one of the images, then this is the K_s magnitude from the one detection. A null value in this column means that the source was not detected on either of the K_s-band combined images.

k_msig %5.3f mag yes Gaussian-reduced K_s-band uncertainty of the the source formed from the uncertainties measured on the north- and south-going combined images. If this source was detected in the K_s-band on only one of the images, then this is the K_s-band uncertainty from the one detection. A null value in this column means that the source was not detected on either of the K_s-band combined images.

cntr_psc %10d --- yes The pts_key/cntr identifier of a 2MASS All-Sky PSC source that lies within 2" of the combined calibration scan source. A null value in this column means that there is no corresponding source found in the PSC.

cntr_xsc %10d --- yes The ext_key/cntr identifier of a 2MASS All-Sky XSC source that lies within 5" of the combined calibration scan source. A null value in this column means that there is no corresponding source found in the XSC.

cc_flg %1s --- no Contamination and confusion flag. Single character flag that indicates if the extraction is associated with the predicted position of an image artifact, or that it has been identified as an artifact through visual inspections. The cc_flg values are as follows:

"G" = Dichroic glint artifact. Extraction is likely a spurious detection of a dichroic glint produced by a nearby bright star.

"P" = Persistence artifact. Extraction is likely a spurious detection of a latent image left by a nearby bright star.

"D" = Diffraction spike artifact. Extraction is likely a spurious detection on a diffraction spike from a nearby star.

"A" = Miscellaneous artifact. Extraction is likely a spurious detection of one of several varieties of image artifacts, including confusion artifacts in bright star halos and "stripes" and ghost images due to electronic crosstalk.

"0" = Source is not affected by an artifact.

CAUTION: The combined calibration scan extracted source tables have not been as thoroughly vetted as the 2MASS Survey, 6x or Calibration Scan Point Source Working Databases. It is very likely that you will find unflagged artifacts in these tables. We strongly recommend that you review the images to verify the nature of sources in these tables.

tile %5d --- no Calibration field identification number.

Column Name	Format	Units	nulls	Description
id	%6d	---	no	Numerical identifier for the source within this calibration field. The identifier is assigned sequentially for each extraction in order of increasing (i.e. south-to-north) declination. Note: This identifier is unique only within the extracted source table for a given calibration field.
ra	%10.6f	deg	no	Average right ascension of the extracted source in the north- and south-going combined images. Note: Positions of sources extracted from the combined calibration scan images can be systematically offset from the 2MASS All-Sky PSC because position reconstruction for the calibration scan data was done with respect to the USNOA-2.0 catalog rather than Tycho 2 (A4.4b and A7.5).
dec	%10.6f	deg	no	Average declination of the extracted source in the north- and south-going combined images. Note: Positions of sources extracted from the combined calibration scan images can be systematically offset from the 2MASS All-Sky PSC because position reconstruction for the calibration scan data was done with respect to the USNOA-2.0 catalog rather than Tycho 2 (A4.4b and A7.5).
dra	%5.3f	arcsec	no	Standard deviation of the average right ascension of source measured on combined north- and south-going scan images.
ddec	%5.3f	arcsec	no	Standard deviation of the average declination of source measured on combined north- and south-going scan images.
j_m	%6.3f	mag	yes	Inverse variance-weighted mean J magnitude of the source measured on the north- and south-going scan combined images. The individual magnitudes are measured in a 4" radius aperture. The background sky reference is measured in an annular region with inner radius of 24" and outer radius of 30". If this source was detected in the J-band on only one of the images, then this is the J magnitude from the one detection. A null value in this column means that the source was not detected on either of the J-band combined images.
j_msig	%5.3f	mag	yes	Gaussian-reduced J-band uncertainty of the the source formed from the uncertainties measured on the north- and south-going combined images. If this source was detected in the J-band on only one of the images, then this is the J-band uncertainty from the one detection. A null value in this column means that the source was not detected on either of the J-band combined images.
h_m	%6.3f	mag	yes	Inverse variance-weighted mean H magnitude of the source measured on the north- and south-going scan combined images. The individual magnitudes are measured in a 4" radius aperture. The background sky reference is measured in an annular region with inner radius of 24" and outer radius of 30". If this source was detected in the H-band on only one of the images, then this is the H magnitude from the one detection. A null value in this column means that the source was not detected on either of the H-band combined images.
h_msig	%5.3f	mag	yes	Gaussian-reduced H-band uncertainty of the the source formed from the uncertainties measured on the north- and south-going combined images. If this source was detected in the H-band on only one of the images, then this is the H-band uncertainty from the one detection. A null value in this column means that the source was not detected on either of the H-band combined images.
k_m	%6.3f	mag	yes	Inverse variance-weighted mean K_s magnitude of the source measured on the north- and south-going scan combined images. The individual magnitudes are measured in a 4" radius aperture. The background sky reference is measured in an annular region with inner radius of 24" and outer radius of 30". If this source was detected in the K_s-band on only one of the images, then this is the K_s magnitude from the one detection. A null value in this column means that the source was not detected on either of the K_s-band combined images.
k_msig	%5.3f	mag	yes	Gaussian-reduced K_s-band uncertainty of the the source formed from the uncertainties measured on the north- and south-going combined images. If this source was detected in the K_s-band on only one of the images, then this is the K_s-band uncertainty from the one detection. A null value in this column means that the source was not detected on either of the K_s-band combined images.
cntr_psc	%10d	---	yes	The pts_key/cntr identifier of a 2MASS All-Sky PSC source that lies within 2" of the combined calibration scan source. A null value in this column means that there is no corresponding source found in the PSC.
cntr_xsc	%10d	---	yes	The ext_key/cntr identifier of a 2MASS All-Sky XSC source that lies within 5" of the combined calibration scan source. A null value in this column means that there is no corresponding source found in the XSC.
cc_flg	%1s	---	no	Contamination and confusion flag. Single character flag that indicates if the extraction is associated with the predicted position of an image artifact, or that it has been identified as an artifact through visual inspections. The cc_flg values are as follows: "G" = Dichroic glint artifact. Extraction is likely a spurious detection of a dichroic glint produced by a nearby bright star. "P" = Persistence artifact. Extraction is likely a spurious detection of a latent image left by a nearby bright star. "D" = Diffraction spike artifact. Extraction is likely a spurious detection on a diffraction spike from a nearby star. "A" = Miscellaneous artifact. Extraction is likely a spurious detection of one of several varieties of image artifacts, including confusion artifacts in bright star halos and "stripes" and ghost images due to electronic crosstalk. "0" = Source is not affected by an artifact. CAUTION: The combined calibration scan extracted source tables have not been as thoroughly vetted as the 2MASS Survey, 6x or Calibration Scan Point Source Working Databases. It is very likely that you will find unflagged artifacts in these tables. We strongly recommend that you review the images to verify the nature of sources in these tables.
tile	%5d	---	no	Calibration field identification number.

[Last Updated: 2006 December 13; by R. Cutri & S. Van Dyk]

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