Panchromatic Hubble Andromeda Treasury. XIV. The Period-Age Relationship of Cepheid Variables in M31 Star Clusters

TL;DR

This study establishes an empirical period-age relation for Cepheid variables in M31 by analyzing 11 Cepheids in star clusters, calibrating photometry, and confirming the relation's consistency with existing literature, enabling precise age estimation.

Contribution

It presents the first empirical period-age relation for M31 Cepheids based on cluster ages, validated through high-resolution HST data and ground-based surveys.

Findings

The period-age relation for M31 Cepheids aligns with previous studies.

Calibration reduces crowding effects in ground-based photometry.

The relation enables accurate age estimates for Cepheids in M31.

Abstract

We present a sample of 11 M31 Cepheids in stellar clusters, derived from the overlap of the Panchromatic Hubble Andromeda Treasury (PHAT) cluster catalog and the Pan-STARRS1 (PS1) disk Cepheid catalog. After identifying the PS1 Cepheids in the HST catalog, we calibrate the PS1 mean magnitudes using the higher resolution HST photometry, revealing up to 1 magnitude offsets due to crowding effects in the ground-based catalog. We measure ages of the clusters by performing single stellar population fits to their color-magnitude diagrams (CMDs) excluding their Cepheids. From these cluster age measurements, we derive an empirical period-age relation which agrees well with the existing literature values. By confirming this relation for M31 Cepheids, we justify its application in high-precision pointwise age estimation across M31.