GEMS: Galaxy Fitting Catalogs and Testing Parametric Galaxy Fitting Codes: GALFIT and GIM2D

By B. Haussler, D. H. Mcintosh, M. Barden, Eric F. Bell, Hans-Walter Rix, A. Borch, S. Beckwith, J. Caldwell, Catherine Heymans, K. Jahnke and 7 more. 2007

243 citations recorded by the source corpus.

In the context of measuring the structures of intermediate-redshift galaxies with HST ACS surveys, we tune, test, and compare two widely used fitting codes (GALFIT and GIM2D) for fitting single-component Sérsic models to both simulated and real galaxy data. Our study focuses on the GEMS survey with the sensitivity of typical HST survey data, and we include our final catalog of fit results for all 41,495 objects detected in GEMS. Using simulations, we find that fitting accuracy depends sensitively on galaxy profile shape. Exponential disks are well fit and have small measurement errors, whereas fits to de Vaucouleurs profiles show larger uncertainties owing to the large amount of light at large radii. Both codes provide reliable fits with little systematic error for galaxies with effective surface brightnesses brighter than that of the sky; the formal uncertainties returned by these codes significantly underestimate the true uncertainties (as estimated using the simulations). We find that GIM2D suffers significant systematic errors for spheroids with close companions owing to the difficulty of effectively masking out neighboring galaxy light; there appears to be no work-around to this important systematic in GIM2D's current implementation. While this crowding error affects only a small fraction of galaxies in GEMS, it must be accounted for in the analysis of deeper cosmological images or of more crowded fields with GIM2D. In contrast, GALFIT results are robust to the presence of neighbors because it can simultaneously fit the profiles of multiple companions as well as the galaxy of interest. We find GALFIT's robustness to nearby companions and factor of ≳20 faster runtime speed are important advantages over GIM2D for analyzing large HST ACS data sets.

Subfields: Astronomy and Astrophysics, Computer Vision and Pattern Recognition, Instrumentation

View Paper: https://www.semanticscholar.org/paper/671cd6bb3c449962e50213f468ac0fbd16c42596

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Citations in the corpus

WHAT TURNS GALAXIES OFF? THE DIFFERENT MORPHOLOGIES OF STAR-FORMING AND QUIESCENT GALAXIES SINCE z ∼ 2 FROM CANDELS (2011, methodology): “While the full dataset at shorter wavelengths in the UDS field has not been analyzed with GALFIT, it is possible to test if this may be an issue using GALFIT on a smaller set of CANDELS F160W data in the GOODS South area, in comparison with published GALFITs on the F850LP ACS GEMS data for the exten”
Image decomposition of barred galaxies and AGN hosts (2007, background): “…one usually finds samples of some hundreds or thousands of galaxies up to z ∼ 1 (e.g., Marleau & Simard 1998; Tasca & White 2005; Allen et al. 2006; Häussler et al. 2007; Huertas-Company et al. 2007, see also Pignatelli, Fasano & Cassata 2006), where fits are done in an automated fashion and…”
GALAXY STRUCTURE AND MODE OF STAR FORMATION IN THE SFR–MASS PLANE FROM z ∼ 2.5 TO z ∼ 0.1 (2011, methodology): “Häussler et al. (2007) arrive at the same qualitative conclusion when inserting simulated n = 1 and n = 4 galaxies in mock ACS images, and recovering the morphological parameters using GALFIT.”
THE MULTIWAVELENGTH SURVEY BY YALE–CHILE (MUSYC): DEEP MEDIUM-BAND OPTICAL IMAGING AND HIGH-QUALITY 32-BAND PHOTOMETRIC REDSHIFTS IN THE ECDF-S (2010, background): “Finally, we look at the subset of sources detected in the GEMS imaging (Häussler et al. 2007).”
DETAILED DECOMPOSITION OF GALAXY IMAGES. II. BEYOND AXISYMMETRIC MODELS (2009, methodology): “In practice, technical issues are not problematic even when Galfit is used for automated analysis (Häussler et al. 2007) 7.”
NEWLY QUENCHED GALAXIES AS THE CAUSE FOR THE APPARENT EVOLUTION IN AVERAGE SIZE OF THE POPULATION (2013, background): “…profile fit-based sizes are themselves prone to increasingly unstable behavior (i.e., large random errors) in the low surface brightness regime (Häussler et al. 2007) and at faint magnitudes; the results of profile-fits are unreliable for typical galaxies fainter than I814W ∼ 23 mag in the…”
STRUCTURAL PARAMETERS OF GALAXIES IN CANDELS (2012, methodology): “The simulated images are generated as described by Häussler et al. (2007), with the background noise taken directly from empty parts of the UDS F160W mosaic.”
Structural properties of pseudo-bulges, classical bulges and elliptical galaxies: a Sloan Digital Sky Survey perspective (2008, methodology): “Another possibility is to fit the entire galaxy as a single component, with a Sérsic function, and then use the Sérsic index so obtained (e.g. Blanton et al. 2005a,b; Häussler et al. 2007).”
A catalogue of 2D photometric decompositions in the SDSS-DR7 spectroscopic main galaxy sample: preferred models and systematics (2014, background): “GIM2D uses the Metropolis search algorithm (Metropolis et al. 1953) to optimize the model parameters rather than a gradient descent algorithm similar to GALFIT.”
EVOLUTION OF THE COLOR–MAGNITUDE RELATION IN GALAXY CLUSTERS AT z ∼ 1 FROM THE ACS INTERMEDIATE REDSHIFT CLUSTER SURVEY (2008, background): “…et al. 1998, ApJ, 501, 571 Goto, T. et al. 2005, ApJ, 621, 188 Gunn, J.E. et al. 1986, ApJ, 306, 30 Jorgensen, I., & Franx, M. 1994, ApJ, 433, 553 Häussler et al., 2007, ApJS, 172, 615 Högbom, J. A. 1974, A&AS, 15, 417 Hogg, D.W., et al. 2004, ApJL, 601, 29 Holden, B.P., et al., 2004, AJ, 127,…”
The Morphologies of Massive Galaxies at 1<z<3 in the CANDELS-UDS Field: Compact Bulges, and the Rise and Fall of Massive Disks (2012, methodology): “It is well established that the robustness of the GALFIT output depends heavily on the input files, such as the background-subtracted image, the σ map and the PSF (see Häussler et al. 2007 for a full discussion of these issues).”
MegaMorph - multiwavelength measurement of galaxy structure: complete Sersic profile information from modern surveys (2012, methodology): “We would also prefer to fit neighbouring galaxies where appropriate, rather an relying on masking (Häussler et al. 2007, hereafter H07).”