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.

Transcript

1. DustPedia: Multiwavelength
   Photometry & Imagery of 875
   Nearby Galaxies in 42 Bands
   Christopher Clark
   Sam Verstocken, Simone Bianchi.
   & the DustPedia team
   cclark@stsci.edu
   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.
   CAAPR
   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
   parallel
   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
   band
   Combine apertures
   from all bands to
   generate final aperture
   Perform photometry
   for all bands in parallel
   Alternatively, user may
   provide pre-defined
   apertures
   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
   extinction
   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
   corresponding
   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).
   dustpedia.com
   

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