Cepheid Metallicity in the Leavitt Law (C-MetaLL) Survey. V. New multiband (grizJHKs) Cepheid light curves and period-luminosity relations

TL;DR

This study provides new multiband light curves and period-luminosity relations for 78 Cepheids, analyzing their metallicity dependence and laying groundwork for improved distance measurements with future large surveys.

Contribution

It offers homogeneous multiband photometry and quantifies the metallicity dependence of Cepheid PL and PW relations using high-resolution spectroscopy.

Findings

Metallicity dependence varies between -0.30 and -0.55 mag/dex across bands.

Residuals are larger for metal-poor Cepheids with [Fe/H] < -0.3.

Slopes of PL and PW relations agree with previous literature.

Abstract

We present homogeneous multiband (grizJHKs) time-series observations of 78 Cepheids including 49 fundamental mode variables and 29 first-overtone mode variables. These observations were collected simultaneously using the ROS2 and REMIR instruments at the Rapid Eye Mount telescope. The Cepheid sample covers a large range of distances (0.5 - 19.7 kpc) with varying precision of parallaxes, and thus astrometry-based luminosity fits were used to derive PL and PW relations in optical Sloan (griz) and near-infrared (JHKs) filters. These empirically calibrated relations exhibit large scatter primarily due to larger uncertainties in parallaxes of distant Cepheids, but their slopes agree well with those previously determined in the literature. Using homogeneous high-resolution spectroscopic metallicities of 61 Cepheids covering -1.1 < [Fe/H] < 0.6 dex, we quantified the metallicity dependence of PL and PW relations which varies between $-0.30\pm0.11$ (in Ks) and $-0.55\pm0.12$ (in z) mag/dex in grizJHKs bands. However, the metallicity dependence in the residuals of the PL and PW relations is predominantly seen for metal-poor stars ([Fe/H] < -0.3 dex), which also have larger parallax uncertainties. The modest sample size precludes us from separating the contribution to the residuals due to parallax uncertainties, metallicity effects, and reddening errors. While this Cepheid sample is not optimal for calibrating the Leavitt law, upcoming photometric and spectroscopic datasets of the C-MetaLL survey will allow the accurate derivation of PL and PW relations in the Sloan and near-infrared bandpasses, which will be useful for the distance measurements in the era of the Vera C. Rubin Observatory's Legacy Survey of Space and Time and upcoming extremely large telescopes.