2MAPPS Software Interface Specification GAL08 1.4 971010 Interface Name: GALWORKS/DBMAN Interface Type of Interface: ASCII text Source Data File Specification Written By: GALWORKS _______________________________ T. Jarrett Read By: DBMAN _______________________________ T. Evans Read By: CALMON _______________________________ S. Wheelock Read By: CONMAN _______________________________ L. Fullmer Description: This output text file from GALWORKS contains the band-merged band-filled position-reconstructed point source data for one scan. This is written by the GALWORKS module BFILL for use by the DBMAN subsystem. The name of the output file will be of the form: s###.bfpts, where ### represents a 3-digit scan number, e.g., s027.bfpts. All information will be in ASCII table-file format. The sources will be written in ascending Y-coordinate order, where Y is the in-scan coordinate of the U-Scan system. File header: The header of the file will consist of comment lines and four column header lines, consistent with the IPAC table format. One comment line will indicate the BFILL version number and the date it was run. Another will contain a "keyword value" (similar to a parameter definition) indicating the number of sources contained in the file. Example: \ BFILL Vsn 1.23 960416 run on 10/12/97 at 12:34:56 \INT NSrc = 208 The first column header line contains the variable names, as listed in the description below. The second line defines the data type of the number in each column. The third line is not used. The fourth line describes the units of the variable. The information on each data line is divided into two sections. The first section is concerned with all non-survey-photometric information; this is primarily position information but also includes source identification fields and optical catalog association fields. The header information for this section is shown below with the four column-header lines broken as a group into two pieces for legibility purposes. Column header lines (columns 1 through 62): | IDNum| RA | Dec |EMaj|EMin|Ang| X_u | Y_u | | int | real | real |real|real|int| real | real | | | | | | | | | | | | deg | deg |asec|asec|deg| asec | asec | Column header lines (columns 62 through 108): | AssnCatID | R | Th| Mag1| Mag2|O|I|CnfFlg| | char |real|int| real| real|i|i| char | | | | | | | | | | | |asec|deg| mag | mag | | | | The second section contains the survey photometric information and consists of the same format for each band. All information in this section is identical in format to that defined in SIS BMG01 and SIS POS05, so those parts of the header lines are not reproduced here; the meanings of some parameters are changed by the band-filling process, however, and those are discussed in the next section. Specification of Output Variables --------------------------------- The output variable formats are identical to those specified in the SIS POS05 and are therefore not duplicated here. The only difference in content is that the photometric magnitudes, uncertainties, and status words are modified for bands in which no detection occurred; in these cases, the purge flag "PrgFlg" is set to "fil", and some of the photometric parameters must be interpreted differently. The set of photometric parameters for J band is defined below; the other bands are identical except for the column numbers. Parameters that have different meanings for band-filled entries are marked with an asterisk preceding their names; all unmarked parameters are zeroed or blanked by BandMerge. Photometric Variables (J): Cols Name Description Units Type Format ------- ------ ------------------------------------- ------- ---- -------- 108-114 IDNumJ Unique ID number in J source file - I*4 I7 115-121 *BFMag Band-fill aperture-photometry mag mag R*4 F7.3 122-127 *BFSig One-sigma uncertainty of BFMag mag R*4 F6.3 128-134 PSFChi Reduced chi squared value of fit - R*4 F7.2 135-140 PSFID ID number of PSF used for fitting - I*4 I6 141-149 *Noise Noise within the aperture cnts R*4 F9.2 150-155 Scale Object-to-PSF compar. width parameter - R*4 F6.3 156-161 Sharp Object-to-PSF compar. height parameter - R*4 F6.3 162-163 B(lend) Number of objects grouped with source - I*4 I2 164-172 PeakPx Peak pixel level above background cnts R*4 F9.2 173-179 StdApM Standard Aperture magnitude (corrected) mag R*4 F7.3 180-185 StMSg Std. dev of std. ap. mag. mag R*4 F6.3 186-192 *Lim95 95%-confidence upper limit mag R*4 F7.3 193-198 LgMSg Std. dev of large ap. mag. mag R*4 F6.3 199-204 R1ID Former ID number of merged R1 source - I*4 I6 205-211 R1Mag R1 aperture magnitude mag R*4 F7.3 212-217 R1Sig R1 mag error estimate mag R*4 F6.3 218-223 PPers Persistence probability - R*4 F6.3 224-230 PrntID Parent ID - I*4 I7 231-234 *BF1Flg Band-filled flag (='fil') - C*3 1X,C3 235-241 *BF2Flg Band-filling status flags - C*6 1X,C6 242-246 *NBPAp No. of bad pixels in band-fill aperture - C*4 1X,A4 Photometric variables for bands H and Ks are in the same format as those for band J above. Each group of band-dependent parameters occupies 139 columns. H variables occupy columns 247-385, and Ks variables occupy columns 386-524. Note that BFMag may have to represent a negative flux; in such a case, the quoted magnitude is BFMag = 99.0 - [ZERO_CAL - 2.5 log10(|flux|)] where ZERO_CAL is the zero calibration magnitude. For example, suppose the integrated flux is -15.5 DN; then for a ZERO_CAL = 19.93 (typical value for K band), we get BFMag = 82.05. When BF1Flg = 'fil' and BFMag > 50, this encoding has been used, and proper decoding should be used, i.e., subtract BFMag from 99.0, compute the flux, and then set it negative. This encoding requires fluxes close to zero to be clipped. The clipping distance is set to 0.01 DN above zero for positive fluxes and below zero for negative fluxes. For example, the positive flux 0.0005 DN would be clipped at 0.01 DN and encoded as BFMag = ZERO_CAL - 2.5 log10(0.01) = 24.93 (for ZERO_CAL = 19.93) For a negative flux of -0.0005 DN, the clipping would yield -0.01 DN, and the encoding would be BFMag = 99.0 - [ZERO_CAL - 2.5 log10(0.01)] = 74.07 (for ZERO_CAL = 19.93) BFMag near 50 cannot occur, so 50 marks the boundary between positive and negative flux encoding when BF1Flg = 'fil'. Encoding the most negative flux imaginable should never threaten to approach a value of 99.0 (a flux of -65536 DN would yield BFMag = 91.11). If this encoding is ignored, the result for fluxes intended to be interpreted as negative is that they become effectively zero. The 95% confidence upper limit is computed as follows: Lim95 = integrated flux + (2 * noise) where the noise in this case means the "local noise", computed as follows (using the DAOPHOT algorithm): noise = sqrt(error1 + error2 + error3) where error1 = variance in the local sky = npix * skyvar npix = number of pixels in the aperture skyvar = the variance (square of the standard deviation) of the sky brightness error2 = photon noise = int. flux * Gain error3 = (skyvar/nsky) * (npix ** 2) nsky = number pixels in sky annulus (skyvar/nsky) = square of the standard error of the mean sky brightness For the case in which the integrated flux is negative, the upper limit is Lim95 = 2 * noise where noise = sqrt(error1 + error3) Different upper limits may be computed using the output from the bandfill module.