Stellar Variability and Distance Indicators in the Near-infrared in Nearby Galaxies. II. Pulsating Stars in the Carina Dwarf Spheroidal

TL;DR

This study uses near-infrared time-series observations of pulsating stars in the Carina dwarf galaxy to accurately determine its distance, confirming the reliability of RR Lyrae stars as standard candles and exploring metallicity effects on other variable stars.

Contribution

First homogeneous near-infrared pulsation data for Carina dSph, providing precise distance measurements and insights into period-luminosity relations and metallicity dependence.

Findings

RR Lyrae distance modulus: 20.079 mag

Distance to Carina: 103.7 kpc

Metallicity affects ACep period-luminosity relation

Abstract

We present homogeneous, near-infrared ($JHK_s$ bands) time-series observations of the classical Carina dwarf Spheroidal (dSph) galaxy to determine accurate and precise distances using the pulsating stars as standard candles. These observations cover two Carina dSph fields ($\sim10.8'\times10.8'$) obtained with the FourStar infrared camera mounted on the 6.5-m Magellan Telescope. We collected precise photometric measurements of 43 RR Lyrae, 11 anomalous Cepheids (ACep), and 102 dwarf Cepheids (DCep) in Carina dSph. Using RR Lyrae, we obtained a distance modulus of $20.079\pm0.028\mathrm{(statistical)}\pm0.045\mathrm{(systematic)}$~mag, or a distance to Carina of $103.7\pm1.3\mathrm{(statistical)}\pm2.2\mathrm{(systematic)}$~kpc. The literature calibrations based on SX Phoenicis or delta-Scuti stars were used to anchor the $JHK_s$ period-luminosity relations for DCep. This resulted in a distance modulus that is in excellent agreement with RR Lyrae based determination. Finally, the distance moduli estimates using the ACep were found to be systematically smaller than the RR Lyrae-based distance modulus, suggesting a metallicity dependence on the ACep period-luminosity relation.