The S4G perspective on circumstellar dust extinction of AGB stars in M100

TL;DR

This study investigates how circumstellar dust extinction affects the near-infrared brightness of AGB stars in clusters within M100, revealing significant impacts on their contribution to galaxy light and implications for high-redshift galaxy modeling.

Contribution

It provides empirical evidence linking dust extinction to AGB star brightness and offers a method to improve age and mass estimates of distant galaxies by accounting for dust effects.

Findings

Dust extinction can reduce AGB star brightness by up to 1 mag in K-band.

AGB contribution to galaxy flux can be halved due to dust effects.

Methodology for selecting AGB-dominated clusters improves high-z galaxy modeling.

Abstract

We examine the effect of circumstellar dust extinction on the near-IR contribution of asymptotic giant branch (AGB) stars in intermediate-age clusters throughout the disk of M100. For our sample of 17 AGB-dominated clusters we extract optical-to-mid-IR SEDs and find that NIR brightness is coupled to the mid-IR dust emission in such a way that a significant reduction of AGB light, of up to 1 mag in K-band, follows from extinction by the dust shell formed during this stage. Since the dust optical depth varies with AGB chemistry (C-rich or O-rich), our results suggest that the contribution of AGB stars to the flux from their host clusters will be closely linked to the metallicity and the progenitor mass of the AGB star, to which dust chemistry and mass-loss rate are sensitive. Our sample of clusters--each the analogue of a ~1 Gyr old post-starburst galaxy--has implications within the context of mass and age estimation via SED modelling at high z: we find that the average ~0.5 mag extinction estimated here may be sufficient to reduce the AGB contribution in (rest-frame) K-band from ~70%, as predicted in the latest generation of synthesis models, to ~35%. Our technique for selecting AGB-dominated clusters in nearby galaxies promises to be effective for discriminating the uncertainties associated with AGB stars in intermediate-age populations that plague age and mass estimation in high-z galaxies.