- ID:
- ivo://CDS.VizieR/J/AJ/158/35
- Title:
- Swift UVOT Stars Survey. III. Galactic open clusters
- Short Name:
- J/AJ/158/35
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As part of the Swift/Ultraviolet-Optical Telescope Stars Survey, we present near-ultraviolet (NUV; 3000-1700 {AA}) point-source photometry for 103 Galactic open clusters. These data, taken over the span of the mission, provide a unique and unprecedented set of NUV point-source photometry on simple stellar populations. After applying a membership analysis fueled mostly by Gaia DR2 (Cat. I/345) proper motions, we find that 49 of these 103 have clear precise color-magnitude diagrams (CMDs) amenable to investigation. We compare the CMDs to theoretical isochrones and find good agreement between the theoretical isochrones and the CMDs. The exceptions are the fainter parts of the main sequence and the red giant branch in the uvw2-uvw1 CMDs, which is most likely due to either the difficulty of correcting for the red leak in the uvw2 filter or limitations in our understanding of UV opacities for cool stars. For the most part, our derived cluster parameters - age, distance, and reddening - agree with the consensus literature, but we find a few clusters that warrant substantial revision from literature values, notably NGC 2304, NGC 2343, NGC 2360, NGC 2396, NGC 2428, NGC 2509, NGC 2533, NGC 2571, NGC 2818, Collinder 220, and NGC 6939. A number of these are clusters in the third Galactic quadrant, where previous studies may have mistaken the disk sequence for the cluster. However, the Gaia DR2 proper motions clearly favor a different sequence. A number of clusters also show white dwarf and blue straggler sequences. We confirm the presence of extended main-sequence turnoffs in NGC 2360 and NGC 2818 and show hints of them in a number of other clusters that may warrant future spectroscopic study. Most of the clusters in the study have low extinction, and the rest are well fit by a "Milky Way-like" extinction law. However, Collinder 220 hints at a possible "LMC-like" extinction law. We finally provide a comprehensive point-source catalog to the community as a tool for future investigation.
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- ID:
- ivo://nasa.heasarc/skyview/swiftxrt
- Title:
- Swift XRT Combined Intensity Images
- Short Name:
- SWIFTXRT
- Date:
- 25 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The Swift XRT (<a href="https://ads.harvard.edu/abs/2005SSRv..120..165B">Burrows et al 2005, SSRv, 120, 165</a>) is a sensitive, broad-band (0.2 - 10 keV) X-ray imager with an effective area of about 125 cm**2 at 1.5 keV. The 600 x 600 pixel CCD at the focus provides a 23.6' x 23.6' field of view with a pixel scale of 2.36". The point spread function is 18" (HPD) at 1.5 keV. <p> These XRT surveys represent the data from the first 12.5 years of Swift X-ray observations. They include all data taken in photon counting mode. A total of just over 8% of the sky has some non-zero exposure. The fraction of sky exposed as a function of the exposure is given in the following table: <table border> <tr><th>Exposure</th><td>>0</td> <td>10</td> <td>30</td> <td>100</td> <td>300</td> <td>1000</td> <td>3000</td> <td>1000</td> <td>30000</td> <td>100000</td><td>300000</td></tr> <tr><th>Coverage</th> <td> 8.42 </td><td> 8.37 </td><td> 8.29 </td><td> 7.67 </td><td> 7.29 </td><td> 5.68 </td> <td> 3.40 </td><td> 1.26 </td><td> 0.35 </td><td> 0.044 </td><td> 0.00118</td></th> </table> The individual exposure and counts maps have been combined into a Hierarchical Progressive Survey (HiPS) where the data are stored in tiles in the HEALPix projection at a number of different resulutions. The highest resolution pixels (HEALPix order 17) have a size of roughly 1.6". Data are also stored at lower resolutions at factors of 1/2, 1/4, 1/8, 1/16, and 1/32, and in an all sky image with a resolution 1/256 of the higest resolution. An intensity map has been created as the ratio of the counts and exposure maps. <p> These surveys combine the basic count and exposure maps provided as standard products in the Swift XRT archive in obsid/xrt/products/*xpc_(sk|ex).img.gz. The surveys were created as follows: <ul> <li>All of the exposure maps available in the archive in mid-May 2017 were combined using the CDS-developed Hipsgen tool. This includes 129,063 observations for which both count and exposure files were found in PC mode. Three exposures where there was a counts map but no exposure map were ignored. A few exposure files had more than one exposure extension. 1,082 files had two extensions and 1 file had 3 extensions. The 1084 HDUs in extensions were extracted as separate files and included in the total exposure. The value of 0 was given to the Hipsgen software as the null value for the FITS files. This caused the CDS software to treat such pixels as missing rather than 0 exposure. <li> The counts data was extracted from the counts maps for each observation using <i>SkyView</i> developed software. For any pixel in which a count was recorded, the corresponding exposure file was checked and if there was any exposure (in any of the associated extensions), then the count was retained. If there was no exposure in any of the extensions of the corresponding exposure file, the counts in the pixel were omitted. Once a count was accepted, the overlap between the counts map pixel and the pixels of the corresponding HiPS tile (or tiles) was computed. Each count was then assigned entirely to a single pixel in the HiPS tile randomly but with the destination pixel probabilities weighted by area of the overlap. Thus if several pixels were found in a given counts map pixel they might be assigned to different pixels in the output image. The HiPS pixels (~1.6") used were of substantially higher resolution than the XRT resolution of 18" and somewhat higher than the counts map resolution of 2.36". <p> A total of 183,750,428 photons were extracted from the counts maps while 15,226 were rejected as being from pixels with 0 exposure. There were 501 pixels which required special treatment as straddling the boundaries of the HEALPix projection. <li> The resulting counts tiles were then clipped using the exposure tiles that had been previously generated. Basically this transferred the coverage of the exposure tiles to the counts tiles. Any counts pixel where the corresponding exposure pixel was a NaN was changed to a NaN to indicate that there was no coverage in this region. <p> During the clipping process 137,730 HiPS level 8 were clipped (of 786,432 over the entire sky). There were 12,236 tiles for which there was some exposure but no counts found. During the clipping process 2 photons were found on pixels where there was no corresponding exposure in the exposure tiles. This can happen when the pixel assignment process noted above shifts a photon just outside the exposed region but should be -- as it was -- rare. These photons were deleted. <li> After creating the clipped level 8 counts maps, level 7 to 3 tiles and an all sky map where generated by averaging pixels 2x2 to decrease each level. When adding the four pixels in the level N map together only pixels whose value was not NaN were considered. <li> Finally an intensity map was created by dividing the counts tiles by the exposure tiles. To eliminate gross fluctuations due to rare counts in regions with very low exposure, only regions with exposure > 1 second were retained. A total of 30 photons were deleted due to this criterion. </ul> <p> Note that while any sampler may in principle be used with these data, the Spline sampler may give unexpected results. The spline computation propogates NaNs thought the image and means that even occasional NaNs can corrupt the output image completely. NaNs are very common in this dataset. Also, if the region straddles a boundary in the HEALPix projection, the size of the requested input region is likely to exceed memory limits since the HiPS data are considered a single very large image. Provenance: Data generated from public images at HEASARC archive. This is a service of NASA HEASARC.
- ID:
- ivo://CDS.VizieR/J/ApJS/185/433
- Title:
- SWIRE/Chandra survey in Lockman Hole Field
- Short Name:
- J/ApJS/185/433
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report a moderate-depth (70ks), contiguous 0.7deg^2^ Chandra survey in the Lockman Hole Field of the Spitzer/SWIRE Legacy Survey coincident with a completed, ultra-deep VLA survey with deep optical and near-infrared imaging in-hand. The primary motivation is to distinguish starburst galaxies and active galactic nuclei (AGNs), including the significant, highly obscured (logN_H_>23) subset. Chandra has detected 775 X-ray sources to a limiting broadband (0.3-8keV) flux ~4x10^-16^erg/cm^2^/s. We present the X-ray catalog, fluxes, hardness ratios, and multi-wavelength fluxes. The logN versus logS agrees with those of previous surveys covering similar flux ranges. The Chandra and Spitzer flux limits are well matched: 771 (99%) of the X-ray sources have infrared (IR) or optical counterparts, and 333 have MIPS 24um detections. There are four optical-only X-ray sources and four with no visible optical/IR counterpart. The very deep (~2.7uJy rms) VLA data yield 251 (>4{sigma}) radio counterparts, 44% of the X-ray sources in the field. More than 40% of the X-ray sources in the VLA field are radio-loud using the classical definition, RL. The majority of these are red and relatively faint in the optical so that the use of RL to select those AGNs with the strongest radio emission becomes questionable. Using the 24um to radio flux ratio (q_24_) instead results in 13 of the 147 AGNs with sufficient data being classified as radio-loud, in good agreement with the ~10% expected for broad-lined AGNs based on optical surveys. We conclude that q_24_ is a more reliable indicator of radio-loudness. Use of RL should be confined to the optically selected type 1 AGN.
- ID:
- ivo://CDS.VizieR/II/255
- Title:
- SWIRE ELAIS N1 Source Catalogs
- Short Name:
- II/255
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Spitzer Wide-area InfraRed Extragalactic survey (SWIRE; Lonsdale et al., 2003PASP..115..897L) Version 1.0 data products release includes an image atlas and a source catalogs from the first of the 6 SWIRE fields to be observed by Spitzer, the ELAIS-N1 field. The release includes both Spitzer IRAC and MIPS mid/far-infrared data products and also Ug'r'i'Z optical data covering the same regions of the sky from the Isaac Newton Telescope (INT) Wide-Field Survey (WFS; McMahon et al., 2001NewAR..45...97M; Gonzalez-Solares et al., 2004, MNRAS, in press). The Version 1.0 SWIRE ELAIS-N1 Source Catalogs have three parts: (1) a catalog including IRAC and MIPS 24{mu}m sources which have been band-merged together. The Spitzer source list has been positionally matched to the optical source list and we report optical position and 5-band magnitude data for each successful match. This catalog contains only sources lying with the region which has full coverage in all four IRAC bands; (2) a 70{mu}m catalog; and (3) a 160{mu}m catalog. The longer wavelength catalogs have not been band-merged with the IRAC+24{mu}m catalog or the optical source list at this time because of complex source confusion issues. The two MIPS-Ge catalogs cover the full area scanned by each MIPS-array, except for areas of low coverage around each edge, and are not restricted to the full IRAC coverage area. All data are available at http://data.spitzer.caltech.edu/popular/swire/20041027_enhanced_v1_EN1
- ID:
- ivo://CDS.VizieR/II/290
- Title:
- SWIRE Photometric Redshift Catalogue
- Short Name:
- II/290
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the SWIRE Photometric Redshift Catalogue 1025119 redshifts of unprecedented reliability and of accuracy comparable with or better than previous work. Our methodology is based on fixed galaxy and quasi-stellar object templates applied to data at 0.36-4.5um, and on a set of four infrared emission templates fitted to infrared excess data at 3.6-170um. The galaxy templates are initially empirical, but are given greater physical validity by fitting star formation histories to them, which also allows us to estimate stellar masses.
- ID:
- ivo://CDS.VizieR/J/ApJS/216/28
- Title:
- SWXCS III. Cluster catalog from 2005-2012 Swift data
- Short Name:
- J/ApJS/216/28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 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, soft fluxes, and, when possible, optical counterparts for a flux-limited sample of X-ray group and cluster candidates. We consider the fields with Galactic latitude |b|>20{deg} to avoid high H I column densities. We discard all of the observations targeted at groups or clusters of galaxies, as well as particular extragalactic fields not suitable to search for faint extended sources. We finally select ~3000 useful fields covering a total solid angle of ~400deg^2^. We identify extended source candidates in the soft-band (0.5-2keV) 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 us to minimize the number of spurious detections and to robustly assess the selection function. Our catalog includes 263 candidate galaxy clusters and groups down to a flux limit of 7x10^-15^erg/cm2/s in the soft band, and the logN-logS is in very good agreement with previous deep X-ray surveys. The final list of sources is cross-correlated with published optical, X-ray, and Sunyaev-Zeldovich catalogs of clusters. We find that 137 sources have been previously identified as clusters in the literature in independent surveys, while 126 are new detections. Currently, we have collected redshift information for 158 sources (60% of the entire sample).
1787. SXDF 100{mu}Jy catalogue
- ID:
- ivo://CDS.VizieR/J/MNRAS/372/741
- Title:
- SXDF 100{mu}Jy catalogue
- Short Name:
- J/MNRAS/372/741
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe deep radio imaging at 1.4GHz of the 1.3-deg^2^ Subaru/XMM-Newton Deep Field (SXDF), made with the Very Large Array in B and C configurations. We present a radio map of the entire field, and a catalogue of 505 sources covering 0.8deg^2^ to a peak flux density limit of 100uJy. Robust optical identifications are provided for 90 per cent of the sources, and suggested identifications are presented for all but 14 (of which seven are optically blank, and seven are close to bright contaminating objects). We show that the optical properties of the radio sources do not change with flux density, suggesting that active galactic nuclei (AGN) continue to contribute significantly at faint flux densities. We test this assertion by cross-correlating our radio catalogue with the X-ray source catalogue and conclude that radio-quiet AGN become a significant population at flux densities below 300uJy, and may dominate the population responsible for the flattening of the radio source counts if a significant fraction of them are Compton-thick.
- ID:
- ivo://CDS.VizieR/J/MNRAS/403/2063
- Title:
- SXDF X-ray groups and galaxy clusters
- Short Name:
- J/MNRAS/403/2063
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a search for galaxy clusters in the Subaru-XMM Deep Field (SXDF). We reach a depth for a total cluster flux in the 0.5-2keV band of 2x10^-15^erg/cm^2^/s over one of the widest XMM-Newton contiguous raster surveys, covering an area of 1.3deg^2^. Cluster candidates are identified through a wavelet detection of extended X-ray emission. The red-sequence technique allows us to identify 57 cluster candidates. We report on the progress with the cluster spectroscopic follow-up and derive their properties based on the X-ray luminosity and cluster scaling relations.
- ID:
- ivo://CDS.VizieR/IX/43
- Title:
- 1SXPS Swift X-ray telescope point source catalogue
- Short Name:
- IX/43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the 1SXPS (Swift-XRT Point Source) catalogue of 151,524 X-ray point-sources detected by the Swift-XRT in 8 years of operation. The catalogue covers 1905 square degrees distributed approximately uniformly on the sky. We analyze the data in two ways. First we consider all observations individually, for which we have a typical sensitivity of ~3e-13 erg.cm^-2^s^-1` (0.3-10 keV). Then we co-add all data covering the same location on the sky: these images have a typical sensitivity of ~9e-14 erg cm^-2^s^-1^ (0.3-10 keV). Our sky coverage is nearly 2.5 times that of 3XMM-DR4, although the catalog is a factor of ~1.5 less sensitive. The median position error is 5.5" (90% confidence), including systematics. Our source detection method improves on that used in previous XRT catalogues and we report >68,000 new X-ray sources. The goals and observing strategy of the Swift satellite allow us to probe source variability on multiple timescales, and we find ~30,000 variable objects in our catalog. For every source we give positions, fluxes, time series (in four energy bands and two hardness ratios), estimates of the spectral properties, spectra and spectral fits for the brightest sources, and variability probabilities in multiple energy bands and timescales.
- ID:
- ivo://CDS.VizieR/IX/58
- Title:
- 2SXPS Swift X-ray telescope point source catalogue
- Short Name:
- IX/58
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We present the 2SXPS (Swift-XRT Point Source) catalog, containing 206,335 point sources detected by the Swift X-ray Telescope (XRT) in the 0.3-10 keV energy range. This catalog represents a significant improvement over 1SXPS, with double the sky coverage (now 3,790deg^2^), and several significant improvements in source detection and classification. In particular, we present for the first time techniques to model the effect of stray light - significantly reducing the number of spurious sources detected. These techniques will be very important for future, large effective area X-ray mission such as the forthcoming Athena X-ray observatory. We also present a new model of the XRT point spread function, and a method for correctly localising and characterising piled up sources. We provide light curves - in four energy bands, two hardness ratios and two binning timescales -- for every source, and from these deduce that over 80,000 of the sources in 2SXPS are variable in at least one band or hardness ratio. The catalog data can be queried or downloaded via a bespoke web interface at https://www.swift.ac.uk/2SXPS, via HEASARC, or in Vizier (IX/58)
