The H alpha Galaxy Survey VII. The spatial distribution of star formation within disks and bulges

TL;DR

This study examines how star formation is spatially distributed within galaxy disks and bulges, revealing that star formation patterns are consistent across galaxy types and influenced by bar structures, with implications for galaxy evolution.

Contribution

It provides a detailed analysis of the spatial distribution of star formation in a large sample of nearby galaxies, highlighting the role of bars and galaxy type in star formation patterns.

Findings

Star formation distribution is similar to old stellar populations in most galaxies.

Barred galaxies show distinct star formation concentrated at bar ends.

Star formation patterns are consistent across different galaxy sizes and luminosities.

Abstract

We analyse the current build-up of stellar mass within the disks and bulges of nearby galaxies through a comparison of the spatial distributions of forming and old stellar populations. H alpha and R-band imaging are used to determine the distributions of young and old stellar populations in 313 S0a - Im field galaxies out to 40 Mpc. Concentration indices and mean normalised light profiles are calculated as a function of galaxy type and bar classification. The mean profiles and concentration indices show a strong and smooth dependence on galaxy type. Apart from a central deficit due to bulge/bar light in some galaxy types, mean H alpha and R-band profiles are very similar. Mean profiles within a given type are remarkably constant even given wide ranges in galaxy luminosity and size. SBc, SBbc and particularly SBb galaxies have profiles that are markedly different from those of unbarred galaxies. H alpha emission from SBb galaxies is studied in detail; virtually all show resolved central components and concentrations of star formation at or just outside the bar-end radius. In these galaxies, star formation has the same radial distribution as R-band light, i.e. stellar mass is building at approximately constant morphology, with no strong evidence for outer truncation or inside-out disk formation. (Abridged.)