Hi-GAL Catalog Definitions

Overview

The Herschel infrared Galactic Plane Survey (Hi-GAL) covers the Galactic plane at five wavelengths from 70 to 500 microns. Hi-GAL DR1 is limited to the inner Milky Way in the longitude range +68d > l > -70d and latitude range 1d > b > -1d. The generation of the Hi-GAL photometric catalogs is discussed in detail in Molinari et al. (2016).

Name Intype Units Description
row_id int Row ID
DESIGNATION char Source designation: Designation of the source based on its Galactic position in the form LLL.llll±b.bbbb. The naming convention for the Hi-GAL catalogue has the form HIGALPXLLL.llll±b.bbbb, where HIGALP stands for the preliminary catalogue, X stands for the band where the source has been identified among the possible choices: B - blue band; R - red band; S - PSW band; M - PMW band; L - PLW band.
GLON double deg Galactic longitude
GLAT double deg Galactic latitude
DGLON float arcsec Uncertainty in GLON. 0 indicates that the fitting process hit the boundary limits imposed on the fit.
DGLAT float arcsec Uncertainty in GLAT. 0 indicates that the fitting process hit the boundary limits imposed on the fit.
ra double deg Right Ascension (J2000)
dec double deg Declination (J2000)
ATLAS_IMAGE char Atlas image file identifier
X_pix double X pixel coordinate of the source in the original image
Y_pix double Y pixel coordinate of the source in the original image
DX d Uncertainty in X_pix
DY d Uncertainty in Y_pix
SOURCE_ID char Source identification: Unique source identification in the form lLLL NNNN, where lLLL is a unique identifier of the original image over which source extraction was carried out, and NNNN is a progressive four-digit, zero-filled number indicating the sequential order of extraction.
FINT_UNCORR double Jy Source-integrated flux
FINT double Jy Source-integrated flux after applying photometric corrections
ERR_FINT double Jy Uncertainty in FINT
FPEAK double MJy/sr Source peak flux
ERR_FPEAK double MJy/sr Uncertainty in FPEAK
FWHMA d arcsec FWHM of source along the major axis
FWHMB d arcsec FWHM of source along the minor axis
ERR_FWHMA double arcsec Uncertainty in FWHMA
ERR_FWHMB double arcsec Uncertainty in FWHMB
PA float deg Position angle
ERR_PA float deg Uncertainty in PA
BACKGROUND double MJy/sr Background value determined at the source peak position
BACK_ACOEFF double MJy/sr Coefficient a of the zero-order term of the background fit
BACK_BCOEFF double MJy/sr/pix Coefficient b of the first-order term x of the background fit
BACK_CCOEFF double MJy/sr/pix Coefficient c of the first-order term y of the background fit
BACK_DCOEFF double MJy/sr/pix^2 Coefficient d of the second-order term x^2 of the background fit
BACK_ECOEFF double MJy/sr/pix^2 Coefficient e of the second-order term y^2 of the background fit
BACK_FCOEFF double MJy/sr/pix^2 Coefficient f of the second-order term xy of the background fit
RMS_TOTAL double MJy/sr Standard deviation of the residuals within the source area
RMS_SURROUND double MJy/sr Standard deviation of the residuals within the fitting window, excluding sources
SNR double Signal to noise ratio
DET_X double Detection relevance along x axis: Relevance of the source in the second-derivative map along the x-axis defined as the ratio between the measured second derivative at source peak position and the adopted local threshold value.
DET_Y double Detection relevance along y axis: Relevance of the source in the second-derivative map along the y-axis defined as the ratio between the measured second derivative at source peak position and the adopted local threshold value.
DET_X45 double Detection relevance along bisector of the xy axis: Relevance of the source in the second-derivative map along the bisector of the xy-axis defined as the ratio between the measured second derivative at source peak position and the adopted local threshold value.
DET_Y45 double Detection relevance along bisector of the yx axis: Relevance of the source in the second-derivative map along the bisector of the yx-axis defined as the ratio between the measured second derivative at source peak position and the adopted local threshold value.
DETLIM_X double MJy/sr/pix^2 Absolute value for the detection limit threshold along x axis
DETLIM_Y double MJy/sr/pix^2 Absolute value for the detection limit threshold along y axis
DETLIM_X45 double MJy/sr/pix^2 Absolute value for the detection limit threshold along bisector of the xy axis
DETLIM_Y45 double MJy/sr/pix^2 Absolute value for the detection limit threshold along bisector of the yx axis
CLUMP_FLAG int Flag for confusion at detection level: A value equal to 0 means that the source was identified from an isolated group of pixels above the threshold in all the four derivative directions. Sources belonging to the extraction of the same atlas image having the same value of this flag belong to the same group of pixels above the threshold.
NCOMP int Number of Gaussian components used in the fitting process
XCENT d X coordinate of the center of the source fitting window in the original image
YCENT d Y coordinate of the center of the source fitting window in the original image
XWINDOW int Half-width size of the source fitting window along x coordinate
YWINDOW int Half-width size of the source fitting window along y coordinate
NCONTAM int Number of other sources falling inside the fitting window
CENT_TOL float Maximum variation in pixels for adjustment of the fit center
DOF int Degrees of freedom of the source Gaussian fit
CHI2 double Chi^2 determined by the fitting engine
CHI2OPP double Estimator of the fidelity between the fit and the data
FIT_STATUS int Fit status flag: Possible values of the flag are: 0 - fit convergence failed; 1 - convergence reached; 2 - convergence reached despite the initial accuracy requested to fitting engine was set too low; 3 - maximum number of iterations in the fitting process reached; 4 - problems in fitting due to the initial guess.
GUESS_FLAG char Flag on quality of guessed source parameters: The form of the flag is GN, where G is a letter defined as A - optimal number of positions to estimate the size; B - sufficient number of positions to estimate the size; C - low number of positions to estimate the size; and N is a number defining the quality of inital guess size: 0 - initial estimate failed; 1 - good initial estimate for sizes; 2 - one of the two guessed sizes was initially estimate as smaller than the PSF; 3 - initial estimates of source sizes were higher than three times the PSF.
GROUP_FLAG int Flag indicating simultaneous multi-component fit: Values different than 0 indicate that the source flux has been determined by simultaneous multi-component fit with all the sources with the same value of the flag extracted on the same Atlas Image.
CONSTRAINS int Flag indicating the number of parameters that reached the tolerance limits. Values of 4 indicate that the source flux has higher unreliability since either the centre and its sizes have reached the maximum (or the minimum) allowed for the fit engine.
RDETP2DX double Reliability ratio along x axis: Ratio between the second-derivative value along x direction expected by the fitted model of the source and the second derivative derivative measured at the detection stage. Values closer to one indicate a higher reliability of the source.
RDETP2DY double Reliability ratio along y axis: Ratio between the second-derivative value along y direction expected by the fitted model of the source and the second derivative derivative measured at the detection stage. Values closer to one indicate a higher reliability of the source.
RDETP2DX45 double Reliability ratio along xy axis: Ratio between the second-derivative value along xy direction expected by the fitted model of the source and the second derivative derivative measured at the detection stage. Values closer to one indicate a higher reliability of the source.
RDETP2DY45 double Reliability ratio along yx axis: Ratio between the second-derivative value along yx direction expected by the fitted model of the source and the second derivative derivative measured at the detection stage. Values closer to one indicate a higher reliability of the source.
OVERLAP_FLAG char Overlap flag: H indicates that the source has been detected in the tile named in column ATLAS_IMAGE; E,W indicate that the source is detected only in the eastern or western adjacent tile, respectively (east is higher Galactic longitude); if the source has been detected in both H and E or W, then the name of the adjacent tile is also listed (e.g. H_l060). In these cases, the entry in the catalogue is the one with the highest S/N.
OVFLUX_FLAG int Overlap flux flag: 0 indicates that the source has been detected only once and therefore all fluxes refer to this detection. -1 indicates that the two fluxes differ by more than 15%; the one listed is that with the highest S/N. 1 indicates that both integrated fluxes lie within 15%, the one in the catalogue is that with the highest S/N. 2 indicates that the integrated fluxes differ by more than 15% but FPEAK are within 15%; the one listed is that with the highest S/N.