New insight on galaxy structure from GALPHAT I. Motivation, methodology, and benchmarks for Sersic models

Details New insight on galaxy structure from GALPHAT I. Motivation, methodology, and benchmarks for Sersic models New insight on galaxy structure from GALPHAT I. Motivation, methodology, and benchmarks for Sersic models

2010-10-06

arxiv.org/abs/1010.1266v1

Astronomy and Astrophysics

Astrophysics

Cosmology and Extragalactic Astrophysics

Submitted to MNRAS. The submitted version with high resolution figures can be downloaded from http://www.astro.umass.edu/~iy

Scientific paper

We introduce a new galaxy image decomposition tool, GALPHAT (GALaxy PHotometric ATtributes), to provide full posterior probability distributions and reliable confidence intervals for all model parameters. GALPHAT is designed to yield a high speed and accurate likelihood computation, using grid interpolation and Fourier rotation. We benchmark this approach using an ensemble of simulated Sersic model galaxies over a wide range of observational conditions: the signal-to-noise ratio S/N, the ratio of galaxy size to the PSF and the image size, and errors in the assumed PSF; and a range of structural parameters: the half-light radius $r_e$ and the Sersic index $n$. We characterise the strength of parameter covariance in Sersic model, which increases with S/N and $n$, and the results strongly motivate the need for the full posterior probability distribution in galaxy morphology analyses and later inferences. The test results for simulated galaxies successfully demonstrate that, with a careful choice of Markov chain Monte Carlo algorithms and fast model image generation, GALPHAT is a powerful analysis tool for reliably inferring morphological parameters from a large ensemble of galaxies over a wide range of different observational conditions. (abridged)

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