Bayesian fitting of multi-Gaussian expansion models to galaxy images

Abstract

Fitting parameterized models to images of galaxies has become the standard for measuring galaxy morphology. This forward modelling technique allows one to account for the PSF to effectively study semi-resolved galaxies. However, using a specific parameterization for a galaxy's surface brightness profile can bias measurements if it is not an accurate representation. Furthermore, it can be difficult to assess systematic errors in parameterized profiles. To overcome these issues we employ the Multi-Gaussian expansion (MGE) method of representing a galaxy's profile together with a Bayesian framework for fitting images. MGE flexibly represents a galaxy's profile using a series of Gaussians. We introduce a novel Bayesian inference approach which uses pre-rendered Gaussian components, which greatly speeds up computation time and makes it feasible to run the fitting code on large samples of galaxies. We demonstrate our method with a series of validation tests. By injecting galaxies, with properties similar to those observed at $z\sim 1.5$, into deep HST observations we show that it can accurately recover total fluxes and effective radii of realistic galaxies. Additionally we use degraded images of local galaxies to show that our method can recover realistic galaxy surface brightness and color profiles. Our implementation is available in an open source python package $\text{imcascade}$, which contains all methods needed for the preparation of images, fitting and analysis of results.

Accepted to ApJ, code available here: https://github.com/tbmiller-astro/imcascade

References in corpus (19)

• The NumPy array: a structure for efficient numerical computation
• 3D-HST+CANDELS: The Evolution of the Galaxy Size-Mass Distribution since $z=3$
• 3D-HST WFC3-selected Photometric Catalogs in the Five CANDELS/3D-HST Fields: Photometry, Photometric Redshifts and Stellar Masses
• A systematic variation of the stellar initial mass function in early-type galaxies
• Measuring the inclination and mass-to-light ratio of axisymmetric galaxies via anisotropic Jeans models of stellar kinematics
• The Evolution of Galaxy Structure over Cosmic Time
• Imfit: A Fast, Flexible New Program for Astronomical Image Fitting
• Morphology and star formation in IllustrisTNG: the build-up of spheroids and discs
• Half-mass radii for ~7,000 galaxies at 1.0 < z < 2.5: most of the evolution in the mass-size relation is due to color gradients
• ProFit: Bayesian Profile Fitting of Galaxy Images
• A physically motivated definition for the size of galaxies in an era of ultra-deep imaging
• An Implementation of Bayesian Lensing Shear Measurement
• The SAMI Galaxy Survey: stellar population and structural trends across the Fundamental Plane
• AutoProf -- I. An automated non-parametric light profile pipeline for modern galaxy surveys
• The kinematics of massive quiescent galaxies at $1.4<z<2.1$: dark matter fractions, IMF variation, and the relation to local early-type galaxies
• Comparing PyMorph and SDSS photometry. I. Background sky and model fitting effects
• Unified lensing and kinematic analysis for any elliptical mass profile
• Probabilistic model for dynamic galaxy decomposition
• A hybrid Fourier--Real Gaussian Mixture method for fast galaxy--PSF convolution

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• JWST reveals a high fraction of disk breaks at $1\le z\le 3$
• JWST Reveals Bulge-dominated Star-forming Galaxies at Cosmic Noon
• New Globular Cluster Candidates in the M81 group
• Self-Similar Buildup and Inside-Out Growth: Tracing the Evolution of Intermediate to High-Mass Star-Forming Galaxies Since $z=2$