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| Paper: |
Galapagos: A Semi-Automated Tool for Galaxy Profile Fitting |
| Volume: |
442, Astronomical Data Analysis Software and Systems XX (ADASSXX) |
| Page: |
155 |
| Authors: |
Häußler, B.; Barden, M.; Bamford, S. P.; Rojas, A. |
| Abstract: |
When it comes to measuring galaxy parameters, e.g. sizes (half-light
radii), shapes (axial ratios) or profiles (Sérsic indices), on a large sample of tens of
thousands of galaxies, e.g. COSMOS, STAGES or GEMS, or even millions of galaxies,
e.g. SDSS, an automated fitting routine is strongly required. In this work, we introduce
GALAPAGOS (Galaxy Analysis over Large Areas: Parameter Assessment by GALFITting
Objects from SEXTRACTOR), a code that enables users to carry out profile fitting on large
surveys in a mostly automated manner. After initial setup and specification of a set of
parameters, the code manages the whole process: source extraction (with SEXTRACTOR)
on the individual survey frames, masking and deblending, setup of the galaxy fitting
process (using GALFIT), the fitting itself, and finally the compilation of all the resulting
parameters into an object catalog; without the need for any user interaction. We
present these steps and highlight the strengths of GALAPAGOS compared to other codes
used for similar purposes. We have carried out thorough tests of the current version of
the code on both real and simulated data. We show results and discuss the statistical
and systematic biases of fitting codes in general and GALAPAGOS in particular. We find
that GALAPAGOS returns very accurate measurements of the galaxy parameters without
systematic bias and with only small statistical uncertainties, at least on 1-orbit HST data
and assuming an optimal setup. We also briefly present MEGAMORPH, which will open
up Galapagos for various survey strategies (including ground-based with variable PSF),
multi-wavelength data, Bulge/Disk decompositions and high-performance computing
facilities. |
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