| Authors Affiliation: | Department of Physics, Cotton University, Panbazar, Guwahati 781001, Assam, India
Department of Physics, Cotton University, Panbazar, Guwahati 781001, Assam, India
Department of Physics, State University of New York Oswego, Oswego, NY 13126, USA
Max Planck Institute for Astrophysics, Garching, Germany
Department of Astronomy, Yale University, CT, USA
Stellar Astrophysics Centre, Aarhus, Denmark
INAF-Osservatorio Astronomico di Capodimonte, Via Moiariello 16, 801301, Napoli, Italy |
| Abstract : | The period-luminosity (PL) relation of Cepheids in the Large Magellanic Cloud (LMC) plays a pivotal role in extra-galactic distance measurement and the determination of the Hubble constant $(H_{0})$. In this work, we present a detailed study of the LMC geometry based on multi-phase PL relations of these Cepheids. We analyse a combined sample of $\sim$3300 fundamental (FU) and first overtone (FO) mode classical Cepheids. We determine the distance modulus and reddening values of individual Cepheids by fitting a simultaneous reddening law to the apparent distance modulus values. We estimate the LMC viewing angle parameters: the inclination angle $(i)$ and position angle of the line of nodes $(\theta_{\rm lon})$ by fitting a plane of the form $z = f(x,y)$ to the three-dimensional distribution of Cepheids in Cartesian coordinates $(x,y,z)$. The values of LMC viewing angles from multi-phase PL relations are found to be: $i = 22\rlap{.}^{\circ}87 \pm 0\rlap{.}^{\circ}43 ~\textrm{(stat.)} \pm 0\rlap{.}^{\circ}82 ~\textrm{(syst.)}$, $\theta_{\rm lon} = 154\rlap{.}^{\circ}76 \pm 1\rlap{.}^{\circ}16 ~\textrm{(stat.)} \pm 0\rlap{.}^{\circ}82 ~\textrm{(syst.)}$, respectively. We have found evidences suggesting that the LMC disk is warped and has a flared structure. The use of multi-phase PL relations in multiple bands results in lower uncertainties for the LMC viewing angle parameters compared to those derived from the mean light PL relations. This shows that the use of multi-phase PL relations with multi-wavelength photometry significantly improves the precision of these measurements, allowing better constraints on the morphology and the structure of the LMC. |
