Fourier Dissection of Early-Type Galaxy Bars

Abstract

This paper reports on a near-infrared survey of early-type galaxies designed to provide information on bar strengths, bulges, disks, and bar parameters in a statistically well-defined sample of S0-Sa galaxies. Early-type galaxies have the advantage that their bars are relatively free of the effects of dust, star formation, and spiral structure that complicate bar studies in later type galaxies. We describe the survey and present results on detailed analysis of the relative Fourier intensity amplitudes of bars in 26 early-type galaxies. We also evaluate the symmetry assumption of these amplitudes with radius, used recently for bar-spiral separation in later-type galaxies. The results show a wide variety of radial Fourier profiles of bars, ranging from simple symmetric profiles that can be represented in terms of a single gaussian component, to both symmetric and asymmetric profiles that can be represented by two overlapping gaussian components. More complicated profiles than these are also found, often due to multiple bar-like features including extended ovals or lenses. Based on the gravitational bar torque indicator Q_b, double-gaussian bars are stronger on average than single-gaussian bars, at least for our small sample. We show that published numerical simulations where the bar transfers a large amount of angular momentum to the halo can account for many of the observed profiles. The range of possibilities encountered in models seems well-represented in the observed systems.Comment: Accepted for publication in AJ. 20 pages, 10 figures, uses emulateapj. Figures have been reduced in resolution here; a full-resolution preprint can be downloaded from http://bama.ua.edu/~rbuta/nirs0s/nirs0s_paper2.html . Further information on the Near-Infrared S0 Survey can be obtained from the NIRS0S website at http://bama.ua.edu/~rbuta/nirs0s/nirs0s.htm

Variation of Galactic Bar Length with Amplitude and Density as Evidence for Bar Growth over a Hubble Time

“…Figure 2 (top right) includes three previous surveys in which this correlation was present but not noticed. The crosses are from K-band images of eight different barred galaxies studied by Regan & Elmegreen (1997), the circles are from -band K s images of 24 different early-type (S0-Sa) barred galaxies in Buta et al (2006), and the triangles are from 10 I-band images of different galaxies in Elmegreen & Elmegreen (1985). Among these three samples, there are only three overlapping galaxies and they are only between the 1985 and 1997 surveys.…”

The Carnegie-Irvine Galaxy Survey. I. Overview and Atlas of Optical Images

“…The Ohio State University Bright Spiral Galaxy Survey (OSUBSGS; Eskridge et al 2002) enforced more rigorous selection criteria to define a set of 205 galaxies and expanded the photometric coverage to the near-infrared (NIR). The lack of early-types in OSUBSGS compelled subsequent attempts to extend the sample to include S0 systems, but only in the NIR (Laurikainen et al 2005;Buta et al 2006). Despite the utility of the Frei and OSUBSGS samples, they had limitations in terms of image quality and filter set.…”

Dynamical Simulations of NGC 2523 and NGC 4245

“…The potential may then be derived from the convolution of the density with the function 1/R (Quillen et al 1994), combined with an assumption for the vertical density distribution. For NGC 2523 and NGC 4245, the potentials were derived from 2.15 μm K s -band images obtained for the Near-Infrared S0 Survey (NIRS0S; Laurikainen et al 2005Laurikainen et al , 2006Buta et al 2006) The K s -band light distribution is useful for estimating the potential due to the reduced extinction effects from dust and the weakened influence of young Population I complexes. Before the gravitational potential was derived, the K s -band images were converted into a surface mass density by assuming a M/L that accounts for the average disk V-K s color gradient using formulae from Bell & de Jong (2001).…”