Stellar population gradients in galaxy discs from the CALIFA survey

Abstract

While studies of gas-phase metallicity gradients in disc galaxies are common, very little has been done towards the acquisition of stellar abundance gradients in the same regions. We present here a comparative study of the stellar metallicity and age distributions in a sample of 62 nearly face-on, spiral galaxies with and without bars, using data from the CALIFA survey. We measure the slopes of the gradients and study their relation with other properties of the galaxies. We find that the mean stellar age and metallicity gradients in the disc are shallow and negative. Furthermore, when normalized to the effective radius of the disc, the slope of the stellar population gradients does not correlate with the mass or with the morphological type of the galaxies. In contrast to this, the values of both age and metallicity at ∼2.5 scale lengths correlate with the central velocity dispersion in a similar manner to the central values of the bulges, although bulges show, on average, older ages and higher metallicities than the discs. One of the goals of the present paper is to test the theoretical prediction that non-linear coupling between the bar and the spiral arms is an efficient mechanism for producing radial migrations across significant distances within discs. The process of radial migration should flatten the stellar metallicity gradient with time and, therefore, we would expect flatter stellar metallicity gradients in barred galaxies. However, we do not find any difference in the metallicity or age gradients between galaxies with and without bars. We discuss possible scenarios that can lead to this lack of difference.

Study of the stellar population properties in the discs of ten spiral galaxies

“…This is expected if the disc components assembled through an inside-out or outside-in process (Brook et al 2004;Muñoz-Mateos et al 2007). The distribution of the age and metallicity gradients is consistent with that of the unbarred disc galaxies studied by Sánchez-Blázquez et al (2014) once their gradients are rescaled to the disc scalelength.…”

“…Yoachim & Dalcanton (2008) and MacArthur et al (2009) detected the presence of an old stellar population (8-10 Gyrs) in the disc-dominated region of 9 edge-on and 8 low inclined spirals, respectively. This result was confirmed by Sánchez-Blázquez et al (2011) andSánchez-Blázquez et al (2014) who studied 62 nearly face-on spirals without finding any significant difference between the discs of unbarred and barred galaxies. Discs are characterised by a large spread in metallicity spanning values between [Z/H]=0 and [Z/H]=-0.2 (Yoachim & Dalcanton 2008).…”

firefly (Fitting IteRativEly For Likelihood analYsis): a full spectral fitting code

“…The ability of the code to recover parameters successfully was shown in Ocvirk et al (2006b), where a detailed analysis of single and double burst mock galaxies was conducted. Although the strengths of STECKMAP lie in its ability to recover parameters accurately from high S/N data, there have been studies using the code at SDSS-like signal-to-noise (see Sánchez-Blázquez et al (2014)). However, since most of their work is much more tuned for high S/N objects, and different stellar population models are used, a deeper comparison between FIREFLY and STECKMAP would prove difficult to make.…”

SDSS-IV MaNGA-resolved Star Formation and Molecular Gas Properties of Green Valley Galaxies: A First Look with ALMA and MaNGA

“…If "nature" processes dominate, galaxies would be expected to grow, evolve, and die inside-out (White & Frenk 1991;Mo et al 1998). Recent IFU observations demonstrate that many nearby spiral galaxies show negative gradients in stellar ages and metallicities, supporting this inside-out picture (González Delgado et al 2014;Sánchez-Blázquez et al 2014;Li et al 2015;Belfiore et al 2017;Goddard et al 2017). On the other hand, if "nurture" dominates galaxy evolution, external processes such as ram-pressure stripping (Gunn & Gott 1972), high speed galaxy encounters (Moore et al 1996), galaxy mergers (Mihos & Hernquist 1994), and "strangulation" (Larson et al 1980;Balogh et al 2000;Peng et al 2015) are responsible for quenching.…”