The Panchromatic View of the Magellanic Clouds From Classical Cepheids. I. Distance, Reddening, and Geometry of the Large Magellanic Cloud Disk

Abstract

We present a detailed investigation of the Large Magellanic Cloud (LMC) disk using classical Cepheids. Our analysis is based on optical (I,V ; OGLE-IV), near-infrared (NIR: J,H,K S ) and midinfrared (MIR: w1; WISE) mean magnitudes. By adopting new templates to estimate the NIR mean magnitudes from single-epoch measurements, we build the currently most accurate, largest and homogeneous multi-band dataset of LMC Cepheids. We determine Cepheid individual distances using optical and NIR Period-Wesenheit relations (PWRs), to measure the geometry of the LMC disk and its viewing angles. Cepheid distances based on optical PWRs are precise at 3%, but accurate to 7%, while the ones based on NIR PWRs are more accurate (to 3%), but less precise (2%-15%), given the higher photometric error on the observed magnitudes. We found an inclination i=25.05 ± 0.02 (stat.) ± 0.55 (syst.) deg, and a position angle of the lines of nodes P.A.=150.76 ± 0.02 (stat.) ± 0.07 (syst.) deg. These values agree well with estimates based either on young (Red Supergiants) or on intermediate-age (Asymptotic Giant Branch, Red Clump) stellar tracers, but they significantly differ from evaluations based on old (RR Lyrae) stellar tracers. This indicates that young/intermediate and old stellar populations have different spatial distributions. Finally, by using the reddening-law fitting approach, we provide a reddening map of the LMC disk which is ten times more accurate and two times larger than similar maps in the literature. We also found an LMC true distance modulus of µ 0,LM C = 18.48 ± 0.10 (stat. and syst.) mag, in excellent agreement with the currently most accurate measurement (Pietrzyński et al. 2013).

Empirical Calibration of the Reddening Maps in the Magellanic Clouds

“…The 0.087 mag spread of the reddening difference can be caused by large errors of reddening measurements for single Cepheids, spread of the reddenings obtained to particular Cepheids and large differences of the reddening law R V values for particular stars. We note that Inno et al (2016) obtained reddening value with the R V value fixed to 3.2. For the first overtone Cepheids (338 objects) the mean difference of our values and Inno et al (2016) values is 0.06 mag.…”

“…We note that Inno et al (2016) obtained reddening value with the R V value fixed to 3.2. For the first overtone Cepheids (338 objects) the mean difference of our values and Inno et al (2016) values is 0.06 mag. Since we can not find any reason why there should be reddening difference for fundamental mode Cepheids and first overtone stars, we decided to exclude the latter ones from the comparison.…”

On a New Theoretical Framework for RR Lyrae Stars. II. Mid-infrared Period–Luminosity–Metallicity Relations

“…We used the synthetic PLZ relations to obtain predicted absolute magnitudes, M λ , in the RIJHK, IRAC, and WISE bands. From these predicted absolute magnitudes, reddened distance moduli (m M -l l ) were calculated, and then used in combination with a universal reddening law to fit both the true distance modulus (μ 0 ) and visual band extinction (A V ) of each star using a weighted least-squares fit of the form and has recently been employed on classical Cepheids by Gieren et al (2005) and Inno et al (2016). The reddening law we adopted was that of Cardelli et al (1989), which we extended into the IRAC and WISE bands according to Indebetouw et al (2005) and Madore et al (2013) respectively.…”

Hubble Law: Measure and Interpretation

“…A spectrum could be used or at least a polychromatic method (see a recent application to LMC of polychromatic method by Inno et al [41]). …”