Estimating Sky Level

Abstract

We develop an improved sky background estimator which employs optimal filters for both spatial and pixel intensity distributions. It incorporates growth of masks around detected objects and a statistical estimate of the flux from undetected faint galaxies in the remaining sky pixels. We test this algorithm for underlying sky estimation and compare its performance with commonly used sky estimation codes on realistic simulations which include detected galaxies, faint undetected galaxies, and sky noise. We then test galaxy surface brightness recovery using GALFIT 3, a galaxy surface brightness profile fitting optimizer, yielding fits to Sérsic profiles. This enables robust sky background estimates accurate at the 4 parts-per-million level. This background sky estimator is more accurate and is less affected by surface brightness profiles of galaxies and the local image environment compared with other methods.

16 pages, 7 figures, 1 table, accepted by PASP

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• The missing light of the Hubble Ultra Deep Field
• Convergence of Lobatto-type Runge-Kutta methods for partitioned differential-algebraic systems of index 2
• Galapagos-2/Galfitm/GAMA -- multi-wavelength measurement of galaxy structure: separating the properties of spheroid and disk components in modern surveys
• A Method To Characterize the Wide-Angle Point Spread Function of Astronomical Images
• Strategies for optimal sky subtraction in the low surface brightness regime
• The SOPHIE search for northern extrasolar planets-XIX. A system including a cold sub-Neptune potentially transiting a V = 6.5 star HD88986
• Sky Subtraction in an Era of Low Surface Brightness Astronomy
• Enabling catalog simulations of transient and variable sources based on LSST cadence strategies
• Galaxy blending effects in deep imaging cosmic shear probes of cosmology
• Memoirs of mass accretion: probing the edges of intracluster light in simulated galaxy clusters