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DustPedia: Multiwavelength Photometry and Imagery of 876 Nearby Galaxies in 42 Ultraviolet–Microwave Bands

DustPedia: Multiwavelength Photometry and Imagery of 876 Nearby Galaxies in 42 Ultraviolet–Microwave Bands

Poster describing the DustPedia imagery and photometry published in C J R Clark et al (2018). Presented at:
"The ISM as a Window Onto Galaxy Evolution" symposium, European Week of Astronomy and Space Science, Liverpool, 2018;
"Cosmic Dust - Origin, Applications, and Implications" conference, Copenhagen, 2018;
"Exploring the Infrared Universe: The Promise of SPICA" conference, Crete, 2019;
"Linking the Milky Way and Nearby Galaxies" conference, Helsinki, 2019.

Chris Clark

April 03, 2018

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  1. DustPedia: Multiwavelength
    Photometry & Imagery of 875
    Nearby Galaxies in 42 Bands
    Christopher Clark
    Sam Verstocken, Simone Bianchi.
    & the DustPedia team
    [email protected]
    We present multiwavelength imagery and photometry across 42 UV–microwave bands
    for 875 nearby galaxies. This database contains custom Herschel reductions, plus
    standardised GALEX, SDSS, DSS, 2MASS, WISE, Spitzer, and Planck data. We also present
    CAAPR, the pipeline we use to conduct aperture-matched photometry of our data;
    CAAPR is designed to produce consistent photometry for the enormous range of galaxy
    and observation types we employ. The 27-band aperture-matched photometry, in
    combination with ancillary catalogue data from IRAS and Planck, represents 21857
    photometric measurements. This rich database of imagery & photometry will be
    invaluable for SPICA follow-up, and is publicly available at: dustpedia.astro.noa.gr
    Initiate pipeline for
    current target
    Most stages can be
    enabled / disabled
    The DustPedia sample contains every
    extended (1’s-1 (~40 Mpc) that was observed by the
    Herschel Space Observatory, excluding only
    the most extended Local Group galaxies.
    The DustPedia imagery database is centred
    around our custom Herschel reductions,
    produced using the most up-to date
    calibrations, combining all available Herschel
    data for each galaxy in the sample.
    Our multiwavelength ancillary imagery was
    assembled from the archives of GALEX, SDSS,
    DSS, 2MASS, WISE, Spitzer, and Planck. We
    combine all available data in each band, and
    the resulting FITS files are standardised to use
    consistent orientations, map sizes, header
    formats, and pixel units of Jy pix-1.
    This database is now publicly available, and is
    continuing to expand as more data is added,
    such as metallicity and gas measurements.
    Comprehensive & Adaptable
    Aperture Photometry Routine
    We developed the CAAPR pipeline to
    perform our aperture-matched photometry.
    In particular, CAAPR features a novel method
    for extrapolating aperture noise in maps too
    small to allow placement of random sky
    apertures. This ensures that all of our
    uncertainties are cross-comparable,
    vital for SED fitting. CAAPR
    is freely available
    on GitHub.
    Perform data
    preparation & aperture
    fitting for all bands in
    Fit and subtract large-
    scale sky structure
    Cutout / reproject
    input image
    Query web catalogues
    to find and remove
    foreground stars
    Example shown to left
    Fit elliptical aperture
    to source emission
    Example shown above
    Deconvolve aperture
    with PSF of current
    Combine apertures
    from all bands to
    generate final aperture
    Perform photometry
    for all bands in parallel
    Alternatively, user may
    provide pre-defined
    Convolve aperture
    with band PSF
    Perform photometry
    using elliptical source
    aperture and annular
    background aperture
    Model source emission
    in 2D to calculate
    aperture correction,
    using band PSF
    Correct flux for
    foreground Galactic
    Attempt to estimate
    aperture noise using
    full-size randomly-
    placed sky apertures
    If insufficient map area
    for full-size sky
    apertures, switch to
    noise extrapolation
    Extrapolate what
    aperture noise would
    be at full aperture size
    Place large numbers of
    smaller sky apertures
    across map, spanning a
    range of sizes
    Example of star-removal, for
    WISE 3.4 µm data of IC 342
    Overview illustration of our
    elliptical aperture fitting
    process, for SPIRE 250 µm
    data of NGC 5364
    Model trend between
    sky aperture area and
    aperture noise
    Output final results,
    and make image grid
    showing apertures
    See example below-left
    Single threaded Multi-threaded
    Multiple threads spawned
    Multiple threads collected
    The source apertures (solid green lines) and background annuli (dashed green lines)
    produced by CAAPR for our aperture-matched multiwavelength photometry of NGC 3686.
    The DustPedia photometry database contains
    the outputs of the 27-band aperture-matched
    photometry performed by CAAPR. We also
    provide supplementary photometry for IRAS
    and Planck, taken from existing datasets. All
    outputs have undergone manual inspection and
    flagging for a range of potential issues.
    In total, we present 21857 photometric
    measurements for our 875 galaxies. A typical
    DustPedia galaxy has multiwavelength
    photometry spanning 25 bands. An example
    SED is shown above.
    Multiwavelength SED of NGC 3686, illustrating the rich photometric
    coverage possible in DustPedia. Solid circles show our aperture-
    matched CAAPR fluxes; hollow circles show supplementary fluxes.
    For complete details of our imagery
    and photometry data products,
    along with a full description of the
    operation of CAAPR, please refer to
    C J R Clark et al (2018).

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