Large Magellanic Cloud Near-Infrared Synoptic Survey. II. The Wesenheit relations and their application to the Distance scale

TL;DR

This paper develops new near-infrared and optical Cepheid Period-Wesenheit relations, applies them to determine distances to the LMC and M31, and finds consistent results with no metallicity dependence.

Contribution

It introduces new near-infrared P-W relations for Cepheids in the LMC and M31, and provides improved distance estimates using these relations.

Findings

LMC distance modulus of 18.47 mag with 0.07 mag uncertainty

M31 distance modulus of 24.46 mag with 0.20 mag uncertainty

No evidence for metallicity dependence in near-infrared P-W relations

Abstract

We present new near-infrared Cepheid Period-Wesenheit relations in the LMC using time-series observations from the Large Magellanic Cloud Near-Infrared Synoptic Survey. We also derive optical$+$near-infrared P-W relations using $V$ and $I$~magnitudes from OGLE-III. We employ our new $JHK_s$ data to determine an independent distance to the LMC of $\mu_{\rm LMC} = 18.47\pm0.07 {\textit{(statistical)}}$~mag, using an absolute calibration of the Galactic relations based on several distance determination methods and accounting for the intrinsic scatter of each technique. We also derive new near-infrared Period-Luminosity and Wesenheit relations for Cepheids in M31 using observations from the PHAT survey. We use the absolute calibrations of the Galactic and LMC $W_{J,H}$ relations to determine the distance modulus of M31, $\mu_{\rm M31} = 24.46\pm0.20$~mag. We apply a simultaneous fit to Cepheids in several Local Group galaxies covering a range of metallicities ($7.7<12+\log[O/H]<8.6$~dex) to determine a global slope of -$3.244\pm0.016$~mag/dex for the $W_{J,K_s}$ relation and obtain robust distance estimates. Our distances are in good agreement with recent TRGB based distance estimates and we do not find any evidence for a metallicity dependence in the near-infrared P-W relations.