Precision age indicators that exploit chemically peculiar stars

TL;DR

This paper explores the potential of chemically peculiar stars as precise age indicators for stellar populations, offering a new method that could improve galaxy star formation history analysis by detecting CP star features in integrated spectra.

Contribution

It introduces a novel approach to age dating of stellar populations using CP star signatures, which are detectable in integrated spectra and less affected by dust or nebular contamination.

Findings

CP stars are detectable in high-quality spectra of young and intermediate populations.

CP features correlate with specific age ranges, enabling age estimation.

The method offers an alternative to traditional photometric and spectral age indicators.

Abstract

We would like to find a way to improve the determination of galaxy star formation history from integrated light spectroscopy. To this end, several classes of chemically peculiar (CP) stars arise during the course of normal evolution in single stars and noninteracting binary stars. An aging stellar population has periods of time in which CP stars contribute to the integrated light, and others in which the contributions fade. The HgMn stars, for example, occupy a narrow temperature range of 10500 to 16000 K, which maps to a narrow range of ages. Wolf-Rayet stars, He-poor stars, Bp-Ap stars, Am-Fm stars, and C stars all become very common in a normal stellar population at various ages between zero and several Gyr, fading in and out in a way that is analogous to features used in stellar spectral classification. We examine population fractions and light fractions in order to assess the feasibility of using CP stars as age tracers. We find that, even though CP stars do not usually dominate in number, there are enough of them so that the CP spectral features are detectable in high-quality integrated spectra of young and intermediate age stellar populations. The new technique should be calibratable and useful. Furthermore, using CP signatures as age dating tools sidesteps reliance on photometry that is susceptible to dust and Balmer features that are susceptible to nebular fill-in.