IRASPSC - IRAS Point Source Catalog, Version 2.0

Overview

The IRAS Point Source Catalog, Version 2.0, is a catalog of some 250,000 well-confirmed infrared point sources observed by the Infrared Astronomical Satellite (IRAS), i.e., sources with angular extents less than approximately 0.5, 0.5, 1.0, and 2.0 arcminutes in the in-scan direction at 12, 25, 60, and 100 microns (µm), respectively. Positions, flux densities, uncertainties, associations with known astronomical objects and various cautionary flags are given for each objectin the catalog. Away from confused regions of the sky, the survey is complete to about 0.4, 0.5, 0.6, and 1.0 Janskies (Jy) at 12, 25, 60, and 100 microns, respectively. Typical position uncertainties are about 2 to 6 arcseconds in the in-scan direction and about 8 to 16 arcseconds in the cross-scan direction.

Catalog Bibcode

1988IRASP.C......0J

References

IRAS Catalog of Point Sources, Version 2.0
     Joint IRAS Science W.G.
     <IPAC (1986)>

Provenance

This online version of the IRASPSC was created by the HEASARC in April 2002 based on ADC/CDS Catalog II/125 (the main file).

Parameters

Name
The IRAS Source Designation, derived from its position by combining the hours, minutes and tenths of minutes of (equinox 1950) right ascension and the sign, degrees and minutes of (equinox 1950) declination. In obtaining the minutes of right ascension and declination for the name, the positions were truncated. The letters 'A','B','C', etc., were appended to names of sources which were so close together that they would otherwise have had identical names.

RA
The Right Ascension of the IRAS source in the selected equinox. The RA was given in 1950.0 coordinates and epoch 1983.5 to a precision of 0.1 seconds of time in the original table.

Dec
The Declination of the IRAS source in the selected equinox. The Declination was given in 1950.0 coordinates and epoch 1983.5 to a precision of 1 arcseconds in the original table.

LII
The Galactic Longitude of the IRAS source.

BII
The Galactic Latitude of the IRAS source.

Error_Semi_Maj_Axis
The semi-major axis of the uncertainty ellipse, in arcseconds. The uncertainty in the position for a source depends on its brightness in the various wavelength bands, its path across the focal plane, and the number of sightings. The final uncertainty after position refinement is expressed as a 95% confidence uncertainty ellipse whose semi-major and semi-minor axes are given in arcseconds.

Error_Semi_Min_Axis
The semi-minor axis of the uncertainty ellipse, in arcseconds. The uncertainty in the position for a source depends on its brightness in the various wavelength bands, its path across the focal plane, and the number of sightings. The final uncertainty after position refinement is expressed as a 95% confidence uncertainty ellipse whose semi-major and semi-minor axes are given in arcseconds.

PA_Error_Ellipse
The orientation of the uncertainty ellipse on the sky, expressed in terms of the position angle between the major axis of the ellipse and the local equatorial meridian. It is expressed in units of degrees east of north.

Times_Observed
The number of times observed, i.e., the number of hour-confirmed sightings.

Flux_12um
The non-color-corrected flux density at 12 microns (µm), in units of Janskys, (1 Jy = 1.0E-26 W/m**2/Hz). The quoted value is an average of all the hours-confirmed sightings. The quality of the flux density is designated by the associated quality_flag parameter for this wavelength. The flux densities have been calculated assuming an intrinsic source energy distribution such that the flux density f(Nu) at the frequency Nu is proportional to 1/Nu. The flux densities for sources which are so bright that they saturated the analog-to-digital converter on every sighting are lower limits based on the brightest value recorded. The uncertainties are given as ten times the quoted flux density in such cases.

Flux_25um
The non-color-corrected flux density at 25 microns (µm), in units of Janskys, (1 Jy = 1.0E-26 W/m**2/Hz). The quoted value is an average of all the hours-confirmed sightings. The quality of the flux density is designated by the associated quality_flag parameter for this wavelength. The flux densities have been calculated assuming an intrinsic source energy distribution such that the flux density f(Nu) at the frequency Nu is proportional to 1/Nu. The flux densities for sources which are so bright that they saturated the analog-to-digital converter on every sighting are lower limits based on the brightest value recorded. The uncertainties are given as ten times the quoted flux density in such cases.

Flux_60um
The non-color-corrected flux density at 60 microns (µm), in units of Janskys, (1 Jy = 1.0E-26 W/m**2/Hz). The quoted value is an average of all the hours-confirmed sightings. The quality of the flux density is designated by the associated quality_flag parameter for this wavelength. The flux densities have been calculated assuming an intrinsic source energy distribution such that the flux density f(Nu) at the frequency Nu is proportional to 1/Nu. The flux densities for sources which are so bright that they saturated the analog-to-digital converter on every sighting are lower limits based on the brightest value recorded. The uncertainties are given as ten times the quoted flux density in such cases.

Flux_100um
The non-color-corrected flux density at 100 microns (µm), in units of Janskys, (1 Jy = 1.0E-26 W/m**2/Hz). The quoted value is an average of all the hours-confirmed sightings. The quality of the flux density is designated by the associated quality_flag parameter for this wavelength. The flux densities have been calculated assuming an intrinsic source energy distribution such that the flux density f(Nu) at the frequency Nu is proportional to 1/Nu. The flux densities for sources which are so bright that they saturated the analog-to-digital converter on every sighting are lower limits based on the brightest value recorded. The uncertainties are given as ten times the quoted flux density in such cases.

Quality_Flag_12um
The quality flag for the 12 micron flux density, where 3 means high quality, 2 moderate quality, and 1 an upper limit.

Quality_Flag_25um
The quality flag for the 25 micron flux density, where 3 means high quality, 2 moderate quality, and 1 an upper limit.

Quality_Flag_60um
The quality flag for the 60 micron flux density, where 3 means high quality, 2 moderate quality, and 1 an upper limit.

Quality_Flag_100um
The quality flag for the 100 micron flux density, where 3 means high quality, 2 moderate quality, and 1 an upper limit.

Number_LRS
The IRAS Low-Resolution Spectrometer (LRS) obtained 8-22 micron spectra of bright 12 and 25 micron sources. This parameter gives the number of statistically meaningful spectra that are available for the particular source.

Rel_Error_Flux_12um
The relative flux density uncertainty at 12 um, expressed as a percentage. Each flux density measurement other than an upper limit has an associated uncertainty which is expressed as a 1-Sigma value in units of 100 x [Delta f(Nu)/f(Nu)].

Rel_Error_Flux_25um
The relative flux density uncertainty at 25 um, expressed as a percentage. Each flux density measurement other than an upper limit has an associated uncertainty which is expressed as a 1-Sigma value in units of 100 x [Delta f(Nu)/f(Nu)].

Rel_Error_Flux_60um
The relative flux density uncertainty at 60 um, expressed as a percentage. Each flux density measurement other than an upper limit has an associated uncertainty which is expressed as a 1-Sigma value in units of 100 x [Delta f(Nu)/f(Nu)].

Rel_Error_Flux_100um
The relative flux density uncertainty at 100 um, expressed as a percentage. Each flux density measurement other than an upper limit has an associated uncertainty which is expressed as a 1-Sigma value in units of 100 x [Delta f(Nu)/f(Nu)].

Min_SNR_12um
The signal-to-noise ratio at 12 um, given for an individual hours-confirmed sighting is the highest value of the detections comprising that sighting. The values quoted are the minima of the signal-to-noise ratios for the various sightings (HCONs) of the source. A value is given for each wavelength band with a high or moderate quality measurement and for those upper limits coming from a non-seconds-confirmed detection. Values of this parameter that were greater than 3,000 are given as 3,000. Notice that in the original ADC/CDS version of this catalog, the equivalent parameter given there was 10 times the minimum signal-to-noise ratio.

Min_SNR_25um
The signal-to-noise ratio at 25 um, given for an individual hours-confirmed sighting is the highest value of the detections comprising that sighting. The values quoted are the minima of the signal-to-noise ratios for the various sightings (HCONs) of the source. A value is given for each wavelength band with a high or moderate quality measurement and for those upper limits coming from a non-seconds-confirmed detection. Values of this parameter that were greater than 3,000 are given as 3,000. Notice that in the original ADC/CDS version of this catalog, the equivalent parameter given there was 10 times the minimum signal-to-noise ratio.

Min_SNR_60um
The signal-to-noise ratio at 60 um, given for an individual hours-confirmed sighting is the highest value of the detections comprising that sighting. The values quoted are the minima of the signal-to-noise ratios for the various sightings (HCONs) of the source. A value is given for each wavelength band with a high or moderate quality measurement and for those upper limits coming from a non-seconds-confirmed detection. Values of this parameter that were greater than 3,000 are given as 3,000. Notice that in the original ADC/CDS version of this catalog, the equivalent parameter given there was 10 times the minimum signal-to-noise ratio.

Min_SNR_100um
The signal-to-noise ratio at 100 um, given for an individual hours-confirmed sighting is the highest value of the detections comprising that sighting. The values quoted are the minima of the signal-to-noise ratios for the various sightings (HCONs) of the source. A value is given for each wavelength band with a high or moderate quality measurement and for those upper limits coming from a non-seconds-confirmed detection. Values of this parameter that were greater than 3,000 are given as 3,000. Notice that in the original ADC/CDS version of this catalog, the equivalent parameter given there was 10 times the minimum signal-to-noise ratio.

Corr_Coeff
Codes for the point source correlation coefficient at 12, 25, 60 and 100 um, respectively. The correlation coefficients can have values between 87-100%, or can have been given no value (represented in this HEASARC table by the '_' symbol). The values are encoded as alphabetic characters with A = 100, B = 99 ... up to N = 87, with one value per band. The value quoted is for the highest correlation coefficient seen for that source on any sighting.

Var_Likelihood
The percent probability (0-99) that a source is variable, based on an analysis of the 12 and 25 micron flux densities and their uncertainties. The value of "-1 " indicates that the source was not examined for variability.

Num_Near_Hours
The number of hours-confirmed point sources located within a 4.5' cross-scan and 6' in-scan (half-widths) window centered on the source. Values larger than 9 are given as 9. A great deal of care went into trying to untangle instances of confusion between neighboring sources. In parts of the sky where the source density was low, confusion processing was sometimes able to separate sources that were quite close together.

Num_Near_Weeks
The number of weeks-confirmed point sources located within a 4.5' cross-scan and 6' in-scan (half-widths) window centered on the source. Values larger than 9 are given as 9. A great deal of care went into trying to untangle instances of confusion between neighboring sources. In parts of the sky where the source density was low, confusion processing was sometimes able to separate sources that were quite close together.

Num_Ext_Src_Secs
The number of seconds-confirmed, small extended source detections at 12, 25, 60, and 100 um, respectively, found within a window centered on the source. The size of the window is 6' in the in-scan direction by 4.5' in the cross-scan direction (half-widths). Values of any of these characters that are greater than 1 should be used as a caution that significant extended structure may exist in the region and that the source in question may be a point-source-like piece of a complex field.

Num_Ext_Src_Weeks
The number of weeks-confirmed, small extended sources at 12, 25, 60, and 100 um, respectively, located within a 6' in-scan by 4.5' cross-scan window (half-width) centered on the source. Values of any of these characters that are greater than 0 means that the point source flux measurement should be treated with caution as the source in question may, in fact, be extended. The flux quoted in the IRAS Catalog of Small Extended Sources (also known as the IRAS Smal-Scale Structure Catalog, ADC/CDS Catalog VII/73) may provide a better value for the source in such cases.

Num_100um_Src
The number of 100 micron-only WSDB sources located within a 1/2 degree x 1/2 degree box in ecliptic coordinates centered on the source (CIRR1 in the original IRAS terminology). The sources included in this count are the weeks-confirmed sources prior to high source density region-processing (if applicable) plus those sources hours-confirmed but not weeks-confirmed. Values of this parameter which are greater than 3 may indicate contamination by cirrus with structure on the point source size-scale.

Ratio_100um
This parameter (CIRR2 in the original IRAS terminology) gives a cirrus indication on a larger scale than the num_100um_src parameter, and compares a "cirrus flux" with the source flux at 100 microns. Values larger than 4-5 indicate the presence of considerable structure in the 100 micron emission on a 1/2 degree scale. A value of 0 indicates that no 1/2 degree data were available for the source in question.

Sky_Brightness_100um
This parameter (CIRR3 in the original IRAS terminology) is the total surface brightness of the sky (in units of MJy/sr) surrounding the source in a 1/2 degree beam at 100 microns, clipped to exclude values greater than 254 MJy/sr. Values of this parameter greater than 30 MJy/sr indicate emission from dust with an appreciable column density. A value of 255 means that no data were available.

Number_ID
Much of the utility of the IRASPSC catalog comes from the association of infrared objects with sources known to exist from other astronomical catalogs. A large number of catalogs were searched for positional matches, and the total number of matches found is given by this parameter. For more information on the identifications, please refer to the Assocations file https://cdsarc.cds.unistra.fr/ftp/cats/II/125/assoc.dat.gz

ID_Type
This parameter has values which range from 1 to 4, and gives information on whether an association was found in an extragalactic catalog (value of 1), a stellar catalog (2), other catalogs (3), or matches in multiple types of catalogs (4).

Corr_Factor_12um
The correction factor applied to the 12 um flux density.

Corr_Factor_25um
The correction factor applied to the 25 um flux density.

Corr_Factor_60um
The correction factor applied to the 60 um flux density.

Corr_Factor_100um
The correction factor applied to the 100 um flux density.

Contact Person

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

Page Author: Browse Software Development Team
Last Modified: Friday, 08-Nov-2024 14:52:14 EST