The Carnegie-Irvine Galaxy Survey. II. Isophotal Analysis

TL;DR

This paper details the isophotal analysis of the Carnegie-Irvine Galaxy Survey, providing a comprehensive catalog of galaxy brightness profiles, geometric parameters, and non-axisymmetric features like bars and spiral arms, with robust calibration methods.

Contribution

It introduces a uniform analysis of galaxy isophotes, including Fourier decomposition techniques to quantify asymmetries and structures, enhancing the understanding of galaxy morphology.

Findings

Diverse brightness profiles in disk galaxies, with many showing non-exponential outer regions.

Quantitative measures of bars, spiral arms, and lopsidedness in galaxy light distributions.

Robust sky subtraction and calibration techniques validated through crosschecks.

Abstract

The Carnegie-Irvine Galaxy Survey (CGS) is a comprehensive investigation of the physical properties of a complete, representative sample of 605 bright (B_T <= 12.9 mag) galaxies in the southern hemisphere. This contribution describes the isophotal analysis of the broadband (BVRI) optical imaging component of the project. We pay close attention to sky subtraction, which is particularly challenging for some of the large galaxies in our sample. Extensive crosschecks with internal and external data confirm that our calibration and sky subtraction techniques are robust with respect to the quoted measurement uncertainties. We present a uniform catalog of one-dimensional radial profiles of surface brightness and geometric parameters, as well as integrated colors and color gradients. Composite profiles highlight the tremendous diversity of brightness distributions found in disk galaxies and their dependence on Hubble type. A significant fraction of S0 and spiral galaxies exhibit non-exponential profiles in their outer regions. We perform Fourier decomposition of the isophotes to quantify non-axisymmetric deviations in the light distribution. We use the geometric parameters, in conjunction with the amplitude and phase of the m=2 Fourier mode, to identify bars and quantify their size and strength. Spiral arm strengths are characterized using the m=2 Fourier profiles and structure maps. Finally, we utilize the information encoded in the m=1 Fourier profiles to measure disk lopsidedness. The databases assembled here and in Paper I lay the foundation for forthcoming scientific applications of CGS.