The Faint Source Survey (FSS) is the definitive Infrared Astronomical Satellite (IRAS) data set for faint point sources. The FSS was produced by point-source filtering the individual detector data streams and then coadding those data streams using a trimmed-average algorithm. The resulting images, or plates, give the best estimate from the IRAS survey data of the point source flux density at every surveyed point of the sky. The Faint Source Catalog (FSC) is a compilation of the sources extracted from the FSS plates that have met reasonable reliability requirements. Averaged over the whole catalog, the FSC is at least 98.5% reliable at 12 and 25 microns, and ~94% at 60 microns. For comparison, the IRAS Point Source Catalog (PSC) is >99.997% reliable, but the sensitivity of the FSC exceeds that of the PSC by about a factor of 2.5. This increase in sensitivity results from the co-adding of the three separate hours-confirming (HCON) passes over the sky which were used for confirmation and not added together for the Point Source Catalog. The FSC also contains 99,973 infrared sources which are not in the PSC. The FSC contains data for 173,044 point sources in unconfused regions with flux densities typically above 0.2 Jy at 12, 25, and 60 microns, and above 1.0 Jy at 100 microns. The FSS plates are somewhat more sensitive but less reliable than the FSC; typically, only sources with SNR > 5 - 6 in the plates are contained in the FSC. The data products, the processing methods used to produce them, results of an analysis of these products, and cautionary notes are given in the Explanatory Supplement to the IRAS Faint Source Survey. This database table contains the IRAS Faint Source Catalog (FSC) (Version 2.0, released in September 1990) non-associations data. The associations data for the IRAS FSC is contained in the file https://cdsarc.cds.unistra.fr/ftp/cats/II/156A/assoc.dat.gz The FSC is limited in galactic latitude to the unconfused regions of sky in which the absolute value of BII is greater than or equal to 10 degrees at 12 and 25 microns and greater than or equal to 20 degrees at 60 microns. Because of the presence of the infrared "cirrus" at 100 microns, the FSC does not contain sources detected ONLY at 100 microns. Sources with a 100 micron detection were included in the catalog if they were bandmerged with high reliability detections at other spectral bands. For the faintest sources, the reliability exceeds 90% at 12 and 25 microns, and 80% at 60 microns. The HEASARC recreated this database table in August 2005, based on the CDS table, in an effort to modernize its parameter names and documentation, as well as to add Galactic coordinates. This is a service provided by NASA HEASARC .

The Infrared Astronomical Satellite (IRAS) Serendipitous Survey Catalog (SSC) is a catalog of 12, 25, 60 and 100 micron photometric observations of 43,866 point-like sources detected fortuitiously in the IRAS Pointed Observation program. The main objective was to take advantage of the longer-than-nominal integration time per source to extend the detection threshold relative to that of the IRAS Point Source Catalog (PSC); about three-fourths of the SSC sources do not appear in the PSC. From 1813 Pointed Observation fields, the effective sky coverage is 1108 square degrees. Relative to the PSC, the SSC is characterized by: enhanced sensitivity (by a factor of about 4) in all four wavelength bands; excellent reliability in uncrowded fields; uneven sky coverage and completeness; reduced positional accuracy; improved photometric accuracy; much greater depth in crowded fields at the expense of reliability and accuracy. More information about the SSC data processing, the catalog format, and an analysis are given in the Explanatory Supplement to the IRAS Serendipitous Survey Catalog. This Browse table was created by the HEASARC in December 2006 based on CDS table II/126, the file sources.dat. More information, e.g., on counterparts in other catalogs to the SSC sources, is available in other files in the directory https://cdsarc.cds.unistra.fr/ftp/cats/II/126/ This is a service provided by NASA HEASARC .

The ROSAT All-Sky Survey Faint Source Catalog (RASS-FSC) was first released by the Max-Planck-Institut fuer extraterrestrische Physik, Garching group (voges et al. 2000) in May 2000. It is derived from the All-Sky Survey performed during the ROSAT mission using the Position-Sensitive Proportional Counter (PSPC) in the energy range 0.1 to 2.4 keV. Over one hundred thousand (105,924 to be exact) sources are catalogued herein, representing the faint extension of the RASS Bright Source Catalog (RASS-BSC, cf. IAU Circular 6420 and Voges et al. 1999, A&A, 349, 389: this is also available at the HEASARC as the RASSBSC database). The sources in this catalog have a detection likelihood of at least seven, and contain at least six source photons. The likelihood L of source detection is defined as L = -ln (1 - P), where P = the probability of source detection. For each source, the ROSAT name, position and positional error, the source count rate and error, the background count rate, the exposure time, the date of observation, two hardness ratios and their associated errors, the source extent and the extent likelihood, and the likelihood of source detection are given, inter alia. This HEASARC database was created in July 2000 based on the May 26 2000 release of the ROSAT All-Sky Survey Faint Source Catalog obtained from the Max-Planck-Institut fuer extraterrestrische Physik, Garching Website: http://www.xray.mpe.mpg.de/rosat/survey/rass-fsc/ This is a service provided by NASA HEASARC .

The Low Frequency Array (LOFAR) Two-metre Sky Survey (LoTSS) is a deep 120-168 MHz imaging survey that will eventually cover the entire Northern sky. Each of the 3,170 pointings will be observed for 8 hours, which, at most declinations, is sufficient to produce ~5-arcsec resolution images with a sensitivity of ~0.1 mJy/beam and accomplish the main scientific aims of the survey which are to explore the formation and evolution of massive black holes, galaxies, clusters of galaxies and large-scale structure. Due to the compact core and long baselines of LOFAR, the images provide excellent sensitivity to both highly extended and compact emission. For legacy value, the data are archived at high spectral and time resolution to facilitate sub-arcsecond imaging and spectral line studies. In this paper, The authors provide an overview of the LoTSS. They outline the survey strategy, the observational status, the current calibration techniques, a preliminary data release, and the anticipated scientific impact. The preliminary images that they have released were created using a fully-automated but direction-independent calibration strategy and are significantly more sensitive than those produced by any existing large-area low-frequency survey. In excess of 44,000 sources are detected in the images that have a resolution of 25-arcseconds, typical noise levels of less than 0.5 mJy/beam, and cover an area of 381 square degrees in the region of the HETDEX Spring Field (Right Ascension 10^h 45^m 00^s to 15^h 30^m ^00^s and Declination +45^o 00' 00" to +57^o 00' 00"). Source detection on the mosaics that are centered on each pointing was performed with PyBDSM (See http://www.astron.nl/citt/pybdsm/ for more details). In an effort to minimize contamination from artifacts, the catalog was created using a conservative 7-sigma detection threshold. Furthermore, as the artifacts are predominantly in regions surrounding bright sources, the authors utilized the PyBDSM functionality to decrease the size of the box used to calculate the local noise when close to bright sources, which has the effect of increasing the estimated noise level in these regions. Their catalogs from each mosaic are merged to create a final catalogue of the entire HETDEX Spring Field region. During this process, the authors remove multiple entries for sources by only keeping sources that are detected in the mosaic centered on the pointing to which the source is closest to the center. In the catalog, they provide the type of source, for which they used PyBDSM to distinguish isolated compact sources, large complex sources, and sources that are within an island of emission that contains multiple sources. In addition, they attempted to distinguish between sources that are resolved and unresolved in their images. The authors have provided a preliminary data release from the LOFAR Two-metre Sky Survey (LoTSS). This release contains 44,500 sources which were detected with a signal in excess of seven times the local noise in their 25" resolution images. The noise varies across the surveyed region but is typically below 0.5 mJy/beam and the authors estimate the catalog to be 90% complete for sources with flux densities in excess of 3.9 mJy/beam. This table was created by the HEASARC in February 2017 based on CDS Catalog J/A+A/598/A104 file lotss.dat. This is a service provided by NASA HEASARC .