The M31 Nearinfrared PeriodLuminosity Relation and its Nonlinearity for δ Cep Variables with 0.5 <= log (P) <= 1.7
Abstract
We present the largest M31 nearinfrared (F110W (close to J band), F160W (H band)) Cepheid sample so far. The sample consists of 371 Cepheids with photometry obtained from the Hubble Space Telescope PHAT program. The sample of 319 fundamental mode Cepheids, 16 first overtone Cepheids, and 36 type II Cepheids was identified using the median absolute deviation outlier rejection method we develop here. This method does not rely on priors and allows us to obtain this clean Cepheid sample without rejecting a large fraction of Cepheids. The obtained periodluminosity relations (PLRs) have a very small dispersion, i.e., 0.155 mag in F160W, despite using random phased observations. This remarkably small dispersion allows us to determine that the PLRs are significantly better described by a broken slope at 10 days than a linear slope. The use of our sample as an anchor to determine the Hubble constant gives a 3.2% larger Hubble constant compared to the Riess et al. sample.
 Publication:

The Astrophysical Journal
 Pub Date:
 February 2015
 DOI:
 10.1088/0004637X/799/2/144
 arXiv:
 arXiv:1405.5218
 Bibcode:
 2015ApJ...799..144K
 Keywords:

 catalogs;
 distance scale;
 galaxies: individual: M31;
 Local Group;
 stars: variables: Cepheids;
 Astrophysics  Astrophysics of Galaxies;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 Accepted for publication in ApJ. Note that the estimate of the Hubble constant changed from the first to the second version. The estimation is now using the difference in the anchor galaxy and therefore the magnitude difference gives an increased Hubble constant