Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 435, Issue 1, Pages 623-649Publisher
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stt1320
Keywords
methods: data analysis; techniques: image processing; galaxies: fundamental parameters; galaxies: photometry; galaxies: structure
Categories
Funding
- NPRP grant Qatar National Research Fund [08-643-1-112]
- NPRP grant
- STFC Advanced Fellowship
- Alfred P. Sloan Foundation
- National Science Foundation
- US Department of Energy
- National Aeronautics and Space Administration
- Japanese Monbukagakusho
- Max Planck Society
- Higher Education Funding Council for England
- American Museum of Natural History
- Astrophysical Institute Potsdam
- University of Basel
- University of Cambridge
- Case-Western Reserve University
- University of Chicago
- Drexel University
- Fermilab
- Institute for Advanced Study
- Johns Hopkins University
- Joint Institute for Nuclear Astrophysics
- Kavli Institute for Particle Astrophysics and Cosmology
- Chinese Academy of Sciences (LAMOST)
- Los Alamos National Laboratory
- Max-Planck-Institute for Astronomy (MPIA)
- Max-Planck-Institute for Astrophysics (MPA)
- New Mexico State University
- Ohio State University
- University of Pittsburgh
- University of Portsmouth
- Princeton University
- United States Naval Observatory
- University of Washington
- STFC [ST/H007156/1, ST/K00090X/1, ST/I001212/1] Funding Source: UKRI
- Science and Technology Facilities Council [ST/K00090X/1, ST/H007156/1, ST/I001212/1] Funding Source: researchfish
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We demonstrate a new multiwavelength technique for two-dimensional parametric modelling of galaxy surface-brightness profiles, which we have incorporated into the widely used software GALFIT. Our new method, named GALFITM, extends GALFIT3's current single-band fitting process by simultaneously using multiple images of the same galaxy to constrain a wavelength-dependent model. Each standard profile parameter may vary as a function of wavelength, with a user-definable degree of smoothness, from constant to fully free. The performance of GALFITM is evaluated by fitting elliptical Sersic profiles to ugriz imaging data for 4026 galaxies, comprising the original Sloan Digital Sky Survey (SDSS) imaging for 163 low-redshift (v less than or similar to 7000 km s(-1)) galaxies and 3863 artificially redshifted (0.01 less than or similar to z less than or similar to 0.25) images of the same galaxies. Comparing results from single-band and multiband techniques, we show that GALFITM significantly improves the extraction of information, particularly from bands with low signal-to-noise ratio (e. g. u and z SDSS bands) when combined with higher signal-to noise images. We also study systematic trends in the recovered parameters, particularly Sersic index, that appear when one performs measurements of the same galaxies at successively higher redshifts. We argue that it is vital that studies investigating the evolution of galaxy structure are careful to avoid or correct for these biases. The resulting multiband photometric structural parameters for our sample of 163 galaxies are provided. We demonstrate the importance of considering multiband measurements by showing that the Sersic indices of spiral galaxies increase to redder wavelengths, as expected for composite bulge-disc systems. Finally, for the ellipticals in our sample, which should be well represented by single-Sersic models, we compare our measured parameters to those from previous studies.
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