Galaxy evolution on resolved scales: ageing and quenching in CALIFA

TL;DR

This study examines how galaxies evolve by analyzing spatially-resolved data from CALIFA, distinguishing between smooth ageing and sudden quenching events, and finds most galaxies follow a secular inside-out evolution pattern.

Contribution

It extends previous work by analyzing kpc-scale resolved galaxy data, revealing diverse evolutionary sequences and evidence of recent quenching in a subset of galaxies.

Findings

Galaxies follow a narrow ageing sequence with intrinsic scatter.

Most galaxies are consistent with secular inside-out evolution.

A small fraction shows signs of recent quenching episodes.

Abstract

This work investigates the fundamental mechanism(s) that drive galaxy evolution in the Local Universe. By comparing two proxies of star-formation sensitive to different timescales, such as EW(H$\alpha$) and colours like $g-r$, one may distinguish between smooth secular evolution (ageing) and sudden changes (quenching) on the recent star formation history of galaxies. Building upon the results obtained from a former study based on 80.000 SDSS single-fibre measurements, we now focus on spatially-resolved (on kpc scales) galaxies, comparing with a sample of 637 nearby objects observed by the CALIFA survey. In general, galaxies cannot be characterised in terms of a single `evolutionary stage'. Individual regions within galaxies arrange along a relatively narrow ageing sequence, with some intrinsic scatter possibly due to their different evolutionary paths. These sequences, though, differ from one galaxy to another, although they are broadly consistent with the overall distribution found for the (central) SDSS spectra. We find evidence of recent quenching episodes (relatively blue colours and strong H$\alpha$ absorption) in a small fraction of galaxies (most notably, low-mass ellipticals), on global scales and individual regions (particularly at high metallicity). However, we argue that most of the systems, over their entire extent, are compatible with a secular inside-out scenario, where the evolutionary stage correlates with both global (mass, morphology, and environment) as well as local (surface brightness and metallicity) properties.