ACDS V10.0 - Detailed Description of II/363

ACDS V10.0 - Sat Jan 18 01:34:56 CET 2025

| # Detailed Description of II/363 : The band-merged unWISE Catalog (Schlafly+, 2019) |

Note : this is the description file of the original catalog. This HTML page corresponds well to the original description, but some minor changes in the format may have been introduced in the FITS output files in order to allow for arithmetic operations on quantities such as coordinates and times. h:m:s and d:m:s units are normally converted into degrees, and YYYY-MM-DD into julian days.
Similarly, some slight changes may have been introduced in the units; the value given in the HTML files supersedes the value indicated in the ReadMe file for this catalogue.

    II/363             The band-merged unWISE Catalog             (Schlafly+, 2019)
    ================================================================================
    The unWISE Catalog: two billion infrared sources from five years of WISE
    imaging.
        Schlafly E.F., Meisner A.M., Green G.M.
       <Astrophys. J. Suppl. Ser., 240, 30 (2019)>
       =2019ApJS..240...30S
       =2020yCat.2363....0S
    ================================================================================
    ADC_Keywords: Infrared sources ; Photometry, infrared ; Surveys

    Mission_Name: WISE

    Keywords: catalogs ; infrared: general ; surveys ; techniques: photometric

    Abstract:
        We present the unWISE Catalog, containing the positions and fluxes of
        roughly 2 billion objects observed by the Wide-field Infrared Survey
        Explorer (WISE) over the full sky. The unWISE Catalog has two
        advantages over the existing WISE catalog (AllWISE): first, it is
        based on significantly deeper imaging, and second, it features
        improved modeling of crowded regions. The deeper imaging used in the
        unWISE Catalog comes from the coaddition of all publicly available
        3-5um WISE imaging, including that from the ongoing
        NEOWISE-reactivation mission, thereby increasing the total exposure
        time by a factor of 5 relative to AllWISE. At these depths, even at
        high Galactic latitudes, many sources are blended with their
        neighbors; accordingly, the unWISE analysis simultaneously fits
        thousands of sources to obtain accurate photometry. Our new catalog
        detects sources roughly 0.7mag fainter than the AllWISE catalog at
        5{sigma}, and more accurately models millions of faint sources in the
        Galactic plane, enabling a wealth of Galactic and extragalactic
        science. In particular, relative to AllWISE, unWISE doubles the number
        of galaxies detected between redshifts 0 and 1 and triples the number
        between redshifts 1 and 2, cataloging more than half a billion
        galaxies over the whole sky.

    Description:
        The unWISE Catalog analyzes the unWISE coadds of the WISE images to
        detect two billion sources over the entire sky at 3.4 and 4.6microns.
        The WISE point spread function has a full-width at half-maximum of
        about 6", which coupled with the large number of sources means that
        many sources significantly overlap with others. To accurately model
        the photometry of these blended sources, the crowdsource (available on
        GitHub) analysis pipeline was used to simultaneously determine the
        positions and fluxes of all sources in the unWISE coadds. The greater
        depth of the unWISE coadds relative to those from the first year of
        the survey, combined with the crowdsource crowded-field modeling,
        allow the unWISE catalog to detect roughly three times as many sources
        as were detected in the AllWISE catalog.

    Acknowledging WISE in publications:
        Please include the following in any published material that makes use
        of the WISE data products:
       "This publication makes use of data products from the Wide-field
        Infrared Survey Explorer, which is a joint project of the University of
        California, Los Angeles, and the Jet Propulsion Laboratory/California
        Institute of Technology, funded by the National Aeronautics and Space
        Administration."

        Please cite one or more of:
        Lang, D., 2014, "unWISE: unblurred coadds of the WISE imaging"
        Astronomical Journal, 147, 108.

        Meisner, A.M., Lang, D., and Schlegel, D.J., 2017, "Full-depth Coadds
        of the WISE and First-year NEOWISE-Reactivation Images"
        Astronomical Journal, 153, 38.

        Meisner, A.M., Lang, D., and Schlegel, D.J., 2017, "Deep Full-sky
        Coadds from Three Years of WISE and NEOWISE Observations"
        Astronomical Journal, 154, 161.

    File Summary:

           FileName      Lrecl  Records   Explanations

    ×                   80        .   This file
    × ReadMe            80        .   This file
    × unwise.sam       563     1000   Sample of the band-merged unWISE catalog
                                      (among 2,214,734,224 sources)

    See also:
     VII/237 : HYPERLEDA. I. Catalog of galaxies (Paturel+, 2003)
     II/311  : The WISE All-Sky data Release (Cutri+ 2012)
     II/328  : The AllWISE data Release (Cutri+ 2013)
     I/337   : Gaia DR1 (Gaia Collaboration, 2016)
     J/ApJS/197/19 : First brown dwarfs discovered by WISE (Kirkpatrick+, 2011)
     J/ApJ/757/83  : The Blanco Cosmology Survey (BCS) (Desai+, 2012)
     J/ApJ/792/30  : NEOWISE magnitudes for near-Earth objects (Mainzer+, 2014)
     J/AJ/152/63   : NEOWISE reactivation mission: 2nd yr data (Nugent+, 2016)
     J/ApJS/224/24 : The COSMOS2015 catalog (Laigle+, 2016)
     J/ApJ/819/24  : z>4.5 QSOs with SDSS and WISE. I. Opt. spectra (Wang+, 2016)
     http://catalog.unwise.me/ : The unWISE Catalog home page
     http://www.jpl.nasa.gov/missions/wide-field-infrared-survey-explorer-wise/ :
                                                                  The WISE home page

    Byte-by-byte Description of file:  unwise.sam

       Bytes Format Units      Label   Explanations

       1- 16  A16   ---        objID   Unique object identifier (unwise_objid)
      18- 28  F11.7 deg        RAdeg   W1 right ascension, if available;
                                        otherwise W2 right ascension (J2000) (ra)
      30- 40  F11.7 deg        DEdeg   W1 declination, if available;
                                        otherwise W2 declination (J2000) (dec)
      42- 49  F8.3  pix        XposW1  [-0.5/2048] x coordinate in the W1 band (xW1)
      51- 58  F8.3  pix        XposW2  [-0.5/2048] x coordinate in the W2 band (xW2)
      60- 67  F8.3  pix        YposW1  [-0.5/2048] y coordinate in the W1 band (yW1)
      69- 76  F8.3  pix        YposW2  [-0.5/2048] y coordinate in the W2 band (yW2)
      78- 89  E12.5 309.05nJy  FW1     [-1337840/5.3E10] Flux in the W1 (3.4um) band
                                        in "Vega nMgy" (fluxW1) (1)
      91-102  E12.5 167.66nJy  FW2     [-4367380/7E10] Flux in the W2 (4.6um) band
                                        in "Vega nMgy" (fluxW2) (1)
     104-128  F25.3 pix      e_XposW1  [0/1E20] Uncertainty in XposW1 (dxW1)
     130-154  F25.3 pix      e_XposW2  [0/1E20] Uncertainty in XposW2 (dxW2)
     156-180  F25.3 pix      e_YposW1  [0/1E20] Uncertainty in YposW1 (dyW1)
     182-206  F25.3 pix      e_YposW2  [0/1E20] Uncertainty in YposW2 (dyW2)
     208-218  E11.5 309.05nJy  e_FW1   [0/1E10] Uncertainty in FW1
                                        (statistical only) (dfluxW1) (1)
     220-230  E11.5 167.66nJy  e_FW2   [0/1E10] Uncertainty in FW2
                                        (statistical only) (dflxW2) (1)
     232-238  F7.5  ---        q_W1    [0/1] Quality factor on W1 (1=good detection)
                                        (qfW1) (2)
     240-246  F7.5  ---        q_W2    [0/1] Quality factor on W2 (1=good detection)
                                        (qfW2) (2)
     248-257  E10.4 ---       rchi2W1  [0/3271100] Average chi square per pixel
                                        on W1, weighted by PSF
     259-268  E10.4 ---       rchi2W2  [0/172620] Average {xi}2 per pixel on W2,
                                        weighted by PSF
     270-277  F8.4  ---        fFW1    [-64/564] Fraction of W1 flux in this
                                        object's PSF that comes from this object
                                        (fracfluxW1)
     279-286  F8.4  ---        fFW2    [-29.1/156.5] Fraction of W2 flux in this
                                        object's PSF that comes from this object
                                        (fracfluxW2)
     288-299  E12.5 309.05nJy  FW1lbs  [-2.6E9/1.9E9] Local-background-subtracted W1
                                        flux in "Vega nMgy" (fluxlbsW1) (1)
     301-312  E12.5 167.66nJy  FW2lbs  [-1.2E10/2E10] Local-background-subtracted W2
                                        flux in "Vega nMgy" (fluxlbsW2) (1)
     314-324  E11.5 309.05nJy e_FW1lbs  [0/2.5E9] Uncertainty in FW1lbs
                                        (dfluxlbsW1) (1)
     326-336  E11.5 167.66nJy e_FW2lbs  [0/8E9] Uncertainty in FW2lbs
                                        (dfluxlbsW2) (1)
     338-343  F6.4  pix        fwhmW1  [0/3] Full-width at half-maximum of PSF in W1
     345-350  F6.4  pix        fwhmW2  [0/3] Full-width at half-maximum of PSF in W2
     352-364  E13.6 ---       SpModW1  [-2844/2819] SExtractor spread_model
                                        parameter on W1 (~0=point source)
                                        (spread_modelW1)
     366-378  E13.6 ---       SpModW2  [-20259/7281] SExtractor spread_model
                                        parameter on W2 (~0=point source)
                                        (spread_modelW2)
     380-391  E12.6 ---     e_SpModW1  [0/3.1E8] Uncertainty in SpModW1
                                        (dspread_modelW1)
     393-408  F16.6 ---     e_SpModW2  [0/5.3E8] Uncertainty in SpModW2
                                        (dspread_modelW2)
     410-421  E12.5 309.05nJy  skyW1   [-7572/52355] Sky in W1 in "Vega nMgy" (1)
     423-434  E12.5 167.66nJy  skyW2   [-8322/54067] Sky in W2 in "Vega nMgy" (1)
     436-446  F11.7 deg       RAW1deg  Right Ascension from individual-image
                                        catalogs in W1 (ra12W1)
     448-458  F11.7 deg       RAW2deg  Right Ascension from individual-image
                                        catalogs in W2 (ra12W2)
     460-470  F11.7 deg       DEW1deg  Declination from individual-image catalogs
                                        in W1 (dec12W1)
     472-482  F11.7 deg       DEW2deg  Declination from individual-image catalogs
                                        in W2 (dec12W2)
     484-491  A8    ---       coaddID  Coadd unique ID (coadd_id)
     493-510  A18   ---       detIDW1  ? Unique detection ID in W1 (unwise_detidW1)
     512-529  A18   ---       detIDW2  ? Unique detection ID in W2 (unwise_detidW2)
     531-535  I5    ---        nmW1    [0/23582] Number of single-exposure images of
                                        this part of sky in coadd in W1
     537-541  I5    ---        nmW2    [0/23187] Number of single-exposure images of
                                        this part of sky in coadd in W2
         543  I1    ---        PrimW1  [0/1] The center of this source is in the
                                        primary region of its coadd in W1
                                        (primary12W1)
         545  I1    ---        PrimW2  [0/1] The center of this source is in the
                                        primary region of its coadd in W2
                                        (primary12W2)
     547-549  I3    ---       FlagsW1  [0/249] unWISE Coadd Flags flags at central
                                        pixel in W1 (flags_unwiseW1) (3)
     551-553  I3    ---       FlagsW2  [0/243] unWISE Coadd Flags flags at central
                                        pixel W2 (flags_unwiseW2) (3)
     555-557  I3    ---     f_FlagsW1  [0/250] Additional informational flags at
                                        central pixel in W1 (flags_infoW1) (4)
     559-561  I3    ---     f_FlagsW2  [0/250] Additional informational flags at
                                        central pixel in W2 (flags_infoW2) (4)
         563  I1    ---        Prim    [0/1] W1 primary status, if available;
                                        otherwise W2 primary status (primary1)

    Note (1): All fluxes are in Vega nanomaggies (nMgy; Finkbeiner+
        2004AJ....128.2577F), so that the Vega magnitude of a source is given
        by 22.5-2.5log(flux). The absolute calibration is ultimately inherited
        from AllWISE through the calibration of Meisner+ (2017AJ....154..161M).
        This inheritance depends on details of the PSF normalization at large
        radii, which is uncertain. To improve the agreement between unWISE and
        AllWISE fluxes, we recommend subtracting 4mmag from unWISE W1 and
        32mmag from unWISE W2 fluxes.

        Corresponding AB magnitudes are given by the following equations:
        mW1,AB=mW1,Vega+2.699
        mW2,AB=mW2,Vega+3.339

        Following these conversion laws, columns in nanomaggies were
        determined by CDS staff to be in units of 309.05nJy and 167.66nJy
        for W1 and W2, respectively.
    Note (2): The "quality factor" is a concept inherited from PS1. It tabulates
        the PSF-weighted fraction of pixels contributing to this detection.
        Good detections will have quality factors close to one. Heavily
        saturated detections will have quality factors close to zero.
    Note (3):  The unWISE flags simply give the value of the unWISE mask image for
        the central pixel of the unWISE catalog source, after "collapsing" the
        time-resolved masks into a smaller number of bits appropriate for
        static sources. All bits mark features of very bright stars. These
        flags are described in more detail here: http://catalog.unwise.me/
        files/unwisebitmaskwriteup-03Dec2018.pdf
        ---------------------------------------
         Bit   Description
        ---------------------------------------
         0     In core or wings
         1     In diffraction spike
         2     In ghost
         3     In first latent
         4     In second latent
         5     In circular halo
         6     Saturated
         7     In geometric diffraction spike
        ---------------------------------------
    Note (4): The unWISE info flags contain additional fields related to the
        crowdsource processing or unWISE coadd bright star mask.
        ---------------------------------------------------------------------------
         Bit   Description
        ---------------------------------------------------------------------------
         0     In PSF of bright star falling off coadd
         1     In HyperLeda large galaxy
         2     In "big object" (e.g., a Magellanic cloud)
         3     Pixel may contain the centroid of a very bright star
         4     crowdsource considers this pixel potentially affected by saturation
         5     Pixel may contain nebulosity
         6     Sources in this pixel will not be aggressively deblended
         7     Candidate sources in this pixel must be "sharp" to be optimized
        ---------------------------------------------------------------------------

    History:
        Downloaded from http://catalog.unwise.me/catalogs.html
    ================================================================================
    (End)                               F.-X. Pineau, E. Perret [CDS]    17-Feb-2020