- ID:
- ivo://nasa.heasarc/sacshpscat
- Title:
- SwiftAGN&ClusterSurvey(SACS)Hard-Band(2-10keV)PointSourceCatalog
- Short Name:
- SACSHPSCAT
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The Swift Active galactic nucleus (AGN) and Cluster Survey (SACS) uses 125 deg<sup>2</sup> of Swift X-ray Telescope (XRT) serendipitous fields with variable depths surrounding gamma-ray bursts to provide a medium depth (4 x 10<sup>-15</sup> erg cm<sup>-2</sup> s<sup>-1</sup>) and medium area survey filling the gap between deep, narrow Chandra/XMM-Newton surveys and wide, shallow ROSAT surveys. In the reference paper, a catalog of 22,563 point sources and 442 extended sources, and the number counts of the AGN and galaxy cluster populations are presented. SACS provides excellent constraints on the AGN number counts at the bright end with negligible uncertainties due to cosmic variance, and these constraints are consistent with previous measurements. The authors use Wide-field Infrared Survey Explorer (WISE) mid-infrared(MIR) colors to classify the sources. For AGNs, they can roughly separate the point sources into MIR-red and MIR-blue AGNs, finding roughly equal numbers of each type in the soft X-ray band (0.5-2.0 keV), but fewer MIR-blue sources in the hard X-ray band (2-8 keV). The cluster number counts, with 5% uncertainties from cosmic variance, are also consistent with previous surveys but span a much larger continuous flux range. Deep optical or IR followup observations of this cluster sample will significantly increase the number of higher redshift (z > 0.5) X-ray-selected clusters. This HEASARC table contains the list of 10,060 Swift XRT point sources which were detected in the hard X-ray band image (2-10 keV) using wavdetect with a false positive threshold of 10<sup>-6</sup> (contained in Table 3 of the reference paper). The authors consider these sources to be AGN candidates. This table was created by the HEASARC in June 2015 based on an electronic version of Table 3 of the reference paper, the list of Swift XRT point sources detected in the hard X-ray (2-10 keV) band, which was obtained from the ApJS web site. This is a service provided by NASA HEASARC .
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- ID:
- ivo://nasa.heasarc/sacssescat
- Title:
- SwiftAGN&ClusterSurvey(SACS)Soft-Band(0.5-2keV)ExtendedSourceCatalog
- Short Name:
- SACSSESCAT
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The Swift Active galactic nucleus (AGN) and Cluster Survey (SACS) uses 125 deg<sup>2</sup> of Swift X-ray Telescope (XRT) serendipitous fields with variable depths surrounding gamma-ray bursts to provide a medium depth (4 x 10<sup>-15</sup> erg cm<sup>-2</sup> s<sup>-1</sup>) and medium area survey filling the gap between deep, narrow Chandra/XMM-Newton surveys and wide, shallow ROSAT surveys. In the reference paper, a catalog of 22,563 point sources and 442 extended sources, and the number counts of the AGN and galaxy cluster populations are presented. SACS provides excellent constraints on the AGN number counts at the bright end with negligible uncertainties due to cosmic variance, and these constraints are consistent with previous measurements. The authors use Wide-field Infrared Survey Explorer (WISE) mid-infrared(MIR) colors to classify the sources. For AGNs, they can roughly separate the point sources into MIR-red and MIR-blue AGNs, finding roughly equal numbers of each type in the soft X-ray band (0.5-2.0 keV), but fewer MIR-blue sources in the hard X-ray band (2-8 keV). The cluster number counts, with 5% uncertainties from cosmic variance, are also consistent with previous surveys but span a much larger continuous flux range. Deep optical or IR followup observations of this cluster sample will significantly increase the number of higher redshift (z > 0.5) X-ray-selected clusters. This HEASARC table contains the list of 442 Swift XRT extended sources which were detected in the soft X-ray band image (0.5-2 keV) and contained in Table 4 of the reference paper. The authors defined the extended source catalog as those sources with S/N >= 4 and a minimum net photon count of 20 that are more than 3 sigma from the mean size of point sources for both their off-axis angle and S/N. The authors consider these extended sources to be candidate clusters of galaxies. This table was created by the HEASARC in July 2015 based on an electronic version of Table 4 of the reference paper, the list of Swift XRT extended sources detected in the soft X-ray (0.5-2 keV) band, which was obtained from the ApJS web site. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/sacsspscat
- Title:
- SwiftAGN&ClusterSurvey(SACS)Soft-Band(0.5-2keV)PointSourceCatalog
- Short Name:
- SACSSPSCAT
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The Swift Active galactic nucleus (AGN) and Cluster Survey (SACS) uses 125 deg<sup>2</sup> of Swift X-ray Telescope (XRT) serendipitous fields with variable depths surrounding gamma-ray bursts to provide a medium depth (4 x 10<sup>-15</sup> erg cm<sup>-2</sup> s<sup>-1</sup>) and medium area survey filling the gap between deep, narrow Chandra/XMM-Newton surveys and wide, shallow ROSAT surveys. In the reference paper, a catalog of 22,563 point sources and 442 extended sources, and the number counts of the AGN and galaxy cluster populations are presented. SACS provides excellent constraints on the AGN number counts at the bright end with negligible uncertainties due to cosmic variance, and these constraints are consistent with previous measurements. The authors use Wide-field Infrared Survey Explorer (WISE) mid-infrared(MIR) colors to classify the sources. For AGNs, they can roughly separate the point sources into MIR-red and MIR-blue AGNs, finding roughly equal numbers of each type in the soft X-ray band (0.5-2.0 keV), but fewer MIR-blue sources in the hard X-ray band (2-8 keV). The cluster number counts, with 5% uncertainties from cosmic variance, are also consistent with previous surveys but span a much larger continuous flux range. Deep optical or IR followup observations of this cluster sample will significantly increase the number of higher redshift (z > 0.5) X-ray-selected clusters. This HEASARC table contains the list of 17,748 Swift XRT point sources which were detected in the soft X-ray band image (0.5-2.0 keV) using wavdetect with a false positive threshold of 10<sup>-6</sup> (contained in Table 2 of the reference paper). The authors consider these sources to be AGN candidates. This table was created by the HEASARC in June 2015 based on an electronic version of Table 2 of the reference paper, the list of Swift XRT point sources detected in the soft X-ray (0.5-2 keV) band, which was obtained from the ApJS web site. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/sacstpscat
- Title:
- SwiftAGN&ClusterSurvey(SACS)Total-Band(0.2-10keV)PointSourceCatalog
- Short Name:
- SACSTPSCAT
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The Swift Active galactic nucleus (AGN) and Cluster Survey (SACS) uses 125 deg<sup>2</sup> of Swift X-Ray Telescope (XRT) serendipitous fields with variable depths surrounding gamma-ray bursts to provide a medium depth (4 x 10<sup>-15</sup> erg cm<sup>-2</sup> s<sup>-1</sup>) and medium area survey filling the gap between deep, narrow Chandra/XMM-Newton surveys and wide, shallow ROSAT surveys. In the reference paper, a catalog of 22,563 point sources and 442 extended sources, and the number counts of the AGN and galaxy cluster populations are presented. SACS provides excellent constraints on the AGN number counts at the bright end with negligible uncertainties due to cosmic variance, and these constraints are consistent with previous measurements. The authors use Wide-field Infrared Survey Explorer (WISE) mid-infrared(MIR) colors to classify the sources. For AGNs, they can roughly separate the point sources into MIR-red and MIR-blue AGNs, finding roughly equal numbers of each type in the soft X-ray band (0.5-2.0 keV), but fewer MIR-blue sources in the hard X-ray band (2-8 keV). The cluster number counts, with 5% uncertainties from cosmic variance, are also consistent with previous surveys but span a much larger continuous flux range. Deep optical or IR followup observations of this cluster sample will significantly increase the number of higher redshift (z > 0.5) X-ray-selected clusters. This HEASARC table contains the list of 22,563 Swift XRT point sources which were detected in the total X-ray band image (0.2-10 keV) using wavdetect with a false positive threshold of 10<sup>-6</sup> (contained in Table 1 of the reference paper). The authors consider these sources to be AGN candidates. This table was created by the HEASARC in June 2015 based on an electronic version of Table 1 of the reference paper, the list of Swift XRT point sources detected in the total X-ray (0.2-10 keV) band, which was obtained from the ApJS web site. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/swbat105m
- Title:
- Swift-BAT 105-Month All-Sky Hard X-Ray Survey
- Short Name:
- SWBAT105M
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The catalog includes hard X-ray sources detected in the first 105-months of observations with the Burst Alert Telescope (BAT) coded-mask imager on board the Swift observatory. The 105-month Swift-BAT survey is a uniform hard X-ray all-sky survey with a sensitivity of 8.40x10<sup>-12</sup>erg/s/cm<sup>2</sup> over 90% of the sky and 7.24x10<sup>-12</sup>erg/s/cm<sup>2</sup> over 50% of the sky in the 14-195 keV band. The Swift-BAT 105-month catalog provides 1632 (422 new detections) hard X-ray sources in the 14-195 keV band above the 4.8 sigma significance level. Adding to the previously known hard X-ray sources, 34% (144/422) of the new detections are identified as Seyfert active galactic nuclei (AGNs) in nearby galaxies (z<0.2). The majority of the remaining identified sources are X-ray binaries (7%, 31) and blazars/BL Lac objects (10%, 43). As part of this new edition of the Swift-BAT catalog, the authors release eight-channel spectra and monthly sampled light curves for each object in the online journal and at the <a href="https://swift.gsfc.nasa.gov/results/bs105mon/">Swift-BAT 105-month website</a>. The data reduction, analysis, and catalog generation of the Swift-BAT 105-month survey (between 2004 December and 2013 August) are conducted following the same procedures as in the Swift-BAT 70-month survey (Baumgartner+ 2013, J/ApJS/207/19). The catalog includes 1632 hard X-ray sources detected across the entire sky. Of these 1632 sources, 422 are new detections with respect to the 70-month catalog, and 320 are reported as hard X-ray sources for the first time. The Swift-BAT 105-month survey catalog contains 947 non-beamed AGNs detected in the hard X-ray band. The authors inspected soft X-ray images provided by Swift-XRT (3-10keV), Chandra (2-10keV), ASCA (2-10keV), and XMM-Newton (4-10keV) for the newly detected sources when available using 15 arcmin of matching radius. See section 2.1 of the paper for further explanations. This table was created by the HEASARC in March 2020 based upon the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJS/235/4">CDS Catalog J/ApJS/235/4</a> file table3.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/swbat157m
- Title:
- Swift-BAT 157-Month All-Sky Hard X-Ray Survey
- Short Name:
- SWBAT157M
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This catalog includes the hard X-ray sources detected in the first 157 months of observations with the Burst Alert Telescope (BAT) coded-mask imager on board the Swift observatory. The results of the 157 months survey catalog has been obtained using data from February 2007 to December 2017 and provide a uniform hard X-ray all-sky survey with a sensitivity of 8.40 x 10<sup>-12</sup> erg/s/cm<sup>2</sup> over 90% of the sky and 7.24 x 10<sup>-12</sup> erg/s/cm<sup>2</sup> over 50% of the sky in the 14-195 keV band. The exposure time in all sky ranges from ~ 15 Ms to ~ 35 Ms, where ~ 50% of the sky achieves an exposure time of ~ 22.8 Ms. The 157 months survey provides 1891 hard X-ray sources in the 14-195 keV band above the 4.8 sigma significance level, where 259 are new detections from the 105-month catalog of which 54 are previously known source in X-ray. The sources identification is mostly from NED and SIMBAD and the 157-month catalog reports for positive identification the counterpart R.A. and Dec and the alternative name. The sources are classified in 17 different classes as follows: <pre> Class Source Type Number of Sources 0 Unknown 221 1 Galactic 4 2 Galaxy 16 3 Galaxy Cluster 26 4 Seyfert I 446 5 Seyfert II 464 6 Other AGN 130 7 Beamed AGN (Blazar/FSRQ) 192 8 LINER 7 9 Cataclysmic Variable Star (CV) 81 10 Pulsar 27 11 Supernova Remnant (SNR) 7 12 Star 26 13 High Mass X-ray Binary (HMXB) 108 14 Low Mass X-ray Binary (LMXB) 118 15 Other X-ray Binary (XRB) 17 16 Tidal Disruption Event 1 Total 1891 </pre> The data reduction, analysis, and catalog generation of the Swift-BAT are conducted following the same procedures of the previous catalog survey (Tueller+ 2010, J/ApJS/1167/186, Baumgartner+ 2013, J/ApJS/207/19). The BAT survey data are collected into arrays (Detector Plane Histograms, DPHs) where the data are binned in ~ 300 s time interval and in 8 energy band channels (14-20, 20-24, 24-35, 35-50, 50-75, 75-100, 100- 197 150, and 150-195 keV) and 1 energy total band (14-195 keV). Three different mosaic images are created from the DPH dividing the sky in 6 regions. The first set has images created in 8 energy bands to span a contiguous time interval (snapshot). The second set has images co-adding data on a time period of a month. The third set is created in 8 energy bands by Crab-weighting the monthly images in each of the energy band with the following weights (Baumgartner+ 2013, J/ApJS/207/19): 27.000, 35.260, 22.700, 29.444, 21.272, 16.062, 8.449, 2.630. The benchmark Crab spectrum adopted is F(E) = 10.17E−2.15 photon cm2 s keV. The source detection algorithm uses the Crab-weighted mosaic images. For each source detected lightcurves and spectra are derived. The lightcurves are obtained from the snapshot images, the mosaic monthly images and the Crab-weighted mosaic images. The spectra are obtained from an additional set of mosaic images by adding all the snapshots for the 157 months period in 8-bands. All the analyses use HEASoft tools version 6.23, and the most recent BAT calibration database (updated on Oct. 3, 2017). Data products are generated for each source detected and these are: three different lightcurves in FITS format obtained from the snapshot, monthly and Crab-weighted monthly mosaic images and the equivalent plots as GIF images; an 8-channel average spectrum in FITS obtained using all 157 months; and a GIF file showing the spectrum with the fit to the best parameter of the power-law model. The snapshot lightcurves report rates for the 8-energy band, the monthly and Crab-weighted monthly mosaic lightcurves reports rated for the 8-energy band and the total band 14-195 keV. This table was ingested by the HEASARC in February 2025 based upon the published 157-month catalog. The catalog is also available at <a href="https://swift.gsfc.nasa.gov/results/bs157mon/">https://swift.gsfc.nasa.gov/results/bs157mon/</a>. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/sixsrvycat
- Title:
- Swift-INTEGRAL X-Ray (SIX) Survey Catalog
- Short Name:
- SIXSRVYCAT
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The supermassive black holes at the center of active galactic nuclei (AGNs) are surrounded by obscuring matter that can block nuclear radiation. Depending on the amount of blocked radiation, the flux from the AGN can be too faint to be detected by currently operating hard X-ray (above 15 keV) missions. At these energies, only ~1% of the intensity of the cosmic X-ray background (CXB) can be resolved into point-like sources that are AGNs. In this work, the authors address the question of undetected sources contributing to the CXB with a very sensitive and new hard X-ray survey: the Swift-INTEGRAL X-ray (SIX) survey, which is obtained with the new approach of combining the Swift/BAT and INTEGRAL/IBIS X-ray observations. The authors merge the observations of both missions, which enhances the exposure time and reduces systematic uncertainties. As a result, they obtain a new survey over a wide sky area of 6200 deg<sup>2</sup> covering the region of the North Ecliptic Pole (NEP) and extending to the contiguous Coma region that is more sensitive than the surveys of Swift/BAT or INTEGRAL/IBIS alone. Their sample comprises 113 sources having S/N ratios of above 4.8 sigma: 86 AGNs (Seyfert-like and blazars), 5 galaxies, 2 clusters of galaxies, 3 Galactic sources, 3 previously detected unidentified X-ray sources, and 14 unidentified sources. The scientific outcome from the study of the sample has been properly addressed to study the evolution of AGNs at a redshift below 0.4. The authors do not find any evolution using the 1/V<sub>max</sub> method. Their sample of faint sources is a suitable target for the new generation of hard X-ray telescopes with focusing techniques. This table was created by the HEASARC in August 2012 based on an electronic version of Table 2 from the reference paper which was obtained from the ApJS web site. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/swiftft
- Title:
- Swift Serendipitous Survey in Deep XRT GRB Fields (SwiftFT)
- Short Name:
- SWIFTFT
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains the SwiftFT catalog of point sources detected by the X-ray Telescope (XRT) on board the Swift satellite in observations centered on gamma-ray bursts (GRBs) during the first four years of operation (Jan 2005 - Dec 2008). Swift is a NASA mission with international participation dedicated to the gamma-ray burst study. It carries three instruments. The BAT is the large field of view instrument and operates in the 10-300 keV energy band; and two narrow field instruments, XRT and UVOT, that operate in the X-ray and UV/optical regime, respectively. The catalog was derived including pointing positions of the 374 fields centered on the GRBs covering a total area of ~32.55 square degrees. Since GRBs are distributed randomly in the sky, the survey covers totally unrelated parts of the sky, and is highly uniform courtesy of the XRT's stable point spread function and small vignetting correction factors. The observations for a particular field were merged together and the source search analysis was restricted to a circular area of 10 arcmin radius centered in the median of the individual observation aim points. The total exposure considering all the fields is of 36.8 Ms, with ~32% of the fields having more than 100 ks exposure time, and ~28% with exposure time in the range 50-100 ks. The catalog was generated by running the detection algorithm in the XIMAGE package version 4.4.1 that locates the point sources using a sliding-cell method. The average background intensity is estimated in several small square boxes uniformly located within the image. The position and intensity of each detected source are calculated in a box whose size maximizes the signal-to-noise ratio. The detect algorithm was run separately in the following three energy bands: 0.3-3 (Soft), 2-10 (Hard), and 0.3-10 (Full) keV. For each detections the three count rates in the soft, hard, and full bands are all corrected for dead times and vignetting using exposure maps and for the PSF. Hardness ratios are calculated using the three energy band and defined as HR = (c<sub>H</sub> - c<sub>S</sub>)/(c<sub>H</sub> + c<sub>S</sub>) where c<sub>S</sub> and c<sub>H</sub> are the count rates in the S(oft) and H(ard) bands, respectively. The catalog was cleaned of spurious and extended sources by visual inspection of all the observations. Count rates in the three bands were converted into flux in the 0.5-10, 0.5-2, and 2-10 keV energy bands, respectively. The flux was estimated using a power law spectrum with photon spectral index of 1.8 and a Galactic N<sub>H</sub> of 3.3 x 10<sup>20</sup> cm<sup>-2</sup>. Each row in the catalog is a unique source. The detections from the soft, hard, and full bands were merged into a single catalog using a matching radius of 6 arcsec and retaining detection with a significance level of being spurious <= 2 x 10<sup>-5</sup> in at least one band. There are 9387 total entries in the catalog. The SWIFTFT acronym honors both the Swift satellite and the memory of Francesca Tamburelli who made numerous crucial contributions to the development of the Swift-XRT data reduction software. This database table was created by the HEASARC in November 2021 based on the electronic version available from the ASI Data Center <a href="https://www.asdc.asi.it/xrtgrbdeep_cat/">https://www.asdc.asi.it/xrtgrbdeep_cat/</a> and published in the Astronomy and Astrophysics Journal. This catalog is also available as the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/528/A122">CDS catalog J/A+A/528/A122</a>. The HEASARC added the source_number parameter, a counter to numerically identify each source in the catalog, as well as Galactic coordinates and changed the source name from SWIFTFTJHHMMSS.s+DDMM.m to SWIFTFT JHHMMSS.s+DDMM.m, adding a space between the catalog prefix and the formatted J2000 coordinates. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/swuvotssc
- Title:
- Swift/UVOT Serendipitous Source Catalog, v1.1
- Short Name:
- SWUVOTSSC
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The first version of the Swift UVOT Serendipitous Source Catalog (UVOTSSC) provides positions and magnitudes, as well as errors and upper limits of confirmed sources, for observations taken from the start of operations in 2005 until October 1st of 2010. The first version of the UVOTSSC has been produced by processing the image data obtained from the Swift Ultraviolet and Optical Telescope (UVOT). The data processing was performed at the Mullard Space Science Laboratory (MSSL, University College London, U.K.) using Swift FTOOLS from NASA's High Energy Astrophysics Software package (HEASoft-6.11), with some customizing of the UVOT packages in order to get more complete source detection and to properly apply quality flags to those sources that were detected within the UVOT image artifacts. The total number of observations with 17'x17' images used for version 1 of the catalog is 23,059, giving 6,200,016 sources in total, of which 2,027,265 have multiple entries in the source table because they have been detected in more than one observation. Some sources were only observed in one filter. The total number of entries in the source table is 13,860,568. The S/N ratio for all sources exceeds 5 in at least one UVOT filter, the rest of the filters having a S/N greater than 3. U, B, V, UVW2, UVM2 and UVW1 refer to the filter bandpasses defined in the UVOT Filterwheel section of the MSSL documentation at <a href="http://www.mssl.ucl.ac.uk/www_astro/uvot/uvot_instrument/filterwheel/filterwheel.html">http://www.mssl.ucl.ac.uk/www_astro/uvot/uvot_instrument/filterwheel/filterwheel.html</a>. The initially released version of the catalog (2015) was done with the source identifier "SWIFTUVOT" for each source, and was made available in that form. The decision was subsequently made to rename the catalog sources by including the catalog version number. In addition, in a few instances multiple source IDs shared the same name (IAUNAME). They will be distinguished by having a letter a,b,c,.. appended to their name. Sources brighter than 0.96 counts per frame have not been included because their coincidence loss is too large to correct for. This HEASARC table contains version 1.1 of the Swift UVOT source table and contains 13,860,568 entries for the individual detections of 6,200,016 sources. The HEASARC has changed the names of many of the parameters from those given in the original table. In such cases, we have listed the original names in parentheses at the end of the parameter descriptions given below. There is a second related table which gives a summary of the observations from which the UVOTSSC sources listed in this table have been detected and measured, which is available at the HEASARC as the SWUVOTSSOB table. This table was created by the HEASARC in May 2017 based upon the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/II/339">CDS Catalog II/339</a> file uvotssc1.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/swxcscat
- Title:
- Swift X-Ray Telescope Cluster Survey Catalog
- Short Name:
- SWXCSCAT
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains the Swift X-ray Cluster Survey (SWXCS) catalog obtained using archival data from the X-ray telescope (XRT) on board the Swift satellite acquired from 2005 February to 2012 November, extending the first release of the SWXCS. The catalog provides positions and soft X-ray fluxes for a flux-limited sample of X-ray group and cluster candidates. In Table 3 of the reference paper (available at the HEASARC as the linked table SWXCSOXID), when possible, optical counterparts are given for these candidates. The authors consider the fields with Galactic latitude |b| > 20 degrees so as to avoid regions of high H I column density. They discard all of the observations targeted at groups or clusters of galaxies, as well as particular extragalactic fields not suitable for searching for faint extended sources. The authors finally select ~ 3000 useful fields covering a total solid angle of ~ 400 deg<sup>2</sup>. They identify extended source candidates in the soft-band (0.5-2 keV) images of these fields using the software EXSdetect, which is specifically calibrated for the XRT data. Extensive simulations are used to evaluate contamination and completeness as a function of the source signal, allowing the authors to minimize the number of spurious detections and to robustly assess the selection function. The final catalog includes 263 candidate galaxy clusters and groups down to a flux limit of 7 x 10<sup>-15</sup> erg/cm<sup>2</sup>/s in the soft band (0.5 - 2.0 keV), and the log N - log S is in very good agreement with previous deep X-ray surveys. In the reference paper, the final list of sources is cross-correlated with published optical, X-ray, and Sunyaev-Zel'dovich catalogs of clusters. The authors find that 137 sources have been previously identified as clusters in the literature in independent surveys, while 126 are new detections. Currently, they have collected redshift information for 158 sources (60% of the entire sample). From the entire Swift XRT archive in the period 2005 February-2012 November, the authors have selected all the fields that can be used to build an unbiased, serendipitous X-ray cluster catalog. This table was created by the HEASARC in March 2015 based on an electronic version of Table 2 from the reference paper which was obtained from the CDS as their catalog J/ApJS/216/28 file table2.dat. This is a service provided by NASA HEASARC .
