On the Lengths, Colors, and Ages of 18 Face‐on Bars

Abstract

Along with a brief analysis we present data obtained from BVRI and Ks images of a sample of 19 galaxies (18 barred and 1 unbarred) which will be further explored in a future paper. We measured the lengths and colors of the bars, created color maps and estimated global color gradients. Applying a method developed in a companion paper, we could distinguish for 7 galaxies in our sample those whose bars have been recently formed from the ones with already evolved bars. We estimated an average difference in the optical colors between young and evolved bars that may be translated to an age difference of the order of 10 Gyr, meaning that bars may be, at least in some cases, long standing structures. Moreover, our results show that, on average, evolved bars are longer than young bars. This seems to indicate that, during its evolution, a bar grows longer by capturing stars from the disk, in agreement with recent numerical and analytical results. Although the statistical significance of these results is low, and further studies are needed to confirm them, we discuss the implications from our results on the possibility of bars being a recurrent phenomenon. We also present isophotal contours for all our images as well as radial profiles of relevant photometric and geometric parameters.

Characterization of galactic bars from 3.6μm S4G imaging

“…Shen & Sellwood 2004;Villa-Vargas et al 2010;Athanassoula et al 2013). This is supported by studies showing that bars are typically composed of old stars (Gadotti & de Souza 2006;Sánchez-Blázquez et al 2011).…”

Physical Properties and Environments of Nearby Galaxies

“…Bars are typically dominated by evolved stellar populations (Gadotti & de Souza 2006), although they are also associated with enhanced nuclear and circumnuclear star formation (Ho, Filippenko & Sargent 1997), and frequently exhibit dust lanes, which is a signature of radially inflowing gas (Kormendy 1982;Athanassoula 1992;Sellwood & Wilkinson 1993;Friedli & Benz 1993). Barred galaxies are also observed to have larger reservoirs of molecular gas in their centers relative to unbarred galaxies (Sakamoto et al 1999;Sheth et al 2005) and flatter chemical abundance gradients (Zaritsky, Kennicutt & Huchra 1994;Martin & Roy 1994).…”

Star Formation Properties in Barred Galaxies (Sfb). I. Ultraviolet to Infrared Imaging and Spectroscopic Studies of NGC 7479

“…In general, star formation is located in the circumnuclear regions and in the ends of bars, while bars are typically dominated by evolved stellar populations (Gadotti & de Souza 2006). In a study of the barred spiral NGC 5383, Sheth et al (2000) found weak Hα emission in the bar between the bar ends and the central region despite the high gas column density in the bar dust lanes.…”