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

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 ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>∼</mml:mo> <mml:mn>10</mml:mn> <mml:mover> <mml:mo>.</mml:mo> <mml:mi mathvariant="normal">′</mml:mi> </mml:mover> <mml:mn>8</mml:mn> <mml:mo>×</mml:mo> <mml:mn>10</mml:mn> <mml:mover> <mml:mo>.</mml:mo> <mml:mi mathvariant="normal">′</mml:mi> </mml:mover> <mml:mn>8</mml:mn> </mml:math> ) 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 ± 0.028(statistical) ± 0.045(systematic) mag, or a distance to Carina of 103.7 ± 1.3(statistical) ± 2.2(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.