Calibrating The Cepheid Period-Luminosity Relation From The Infrared Surface Brightness Technique II. The Effect Of Metallicity And The Distance To The LMC

dc.contributor.utaustinauthorBarnes, Thomas G.en_US
dc.contributor.utaustinauthorNicolas Nardettoen_US
dc.creatorStorm, Jesperen_US
dc.creatorGieren, Wolfgangen_US
dc.creatorFouque, Pascalen_US
dc.creatorBarnes, Thomas G.en_US
dc.creatorSoszynski, I.en_US
dc.creatorPietrzynski, G.en_US
dc.creatorNardetto, Nicolasen_US
dc.creatorQueloz, D.en_US
dc.description.abstractContext. The extragalactic distance scale builds directly on the Cepheid period-luminosity (PL) relation as delineated by the sample of Cepheids in the Large Magellanic Cloud (LMC). However, the LMC is a dwarf irregular galaxy, quite different from the massive spiral galaxies used for calibrating the extragalactic distance scale. Recent investigations suggest that not only the zero-point but also the slope of the Milky Way PL relation differ significantly from that of the LMC, casting doubts on the universality of the Cepheid PL relation. Aims. We want to make a differential comparison of the PL relations in the two galaxies by delineating the PL relations using the same method, the infrared surface brightness method (IRSB), and the same precepts. We furthermore extend the metallicity baseline for investigating the zero-point dependence, by applying the method to five SMC Cepheids as well. Methods. The IRSB method is a Baade-Wesselink type method to determine individual distances to Cepheids. We apply a newly revised calibration of the method as described in an accompanying paper (Paper I) to 36 LMC and five SMC Cepheids and delineate new PL relations in the V, I, J, & K bands as well as in the Wesenheit indices in the optical and near-IR. Results. We present 509 new and accurate radial velocity measurements for a sample of 22 LMC Cepheids, enlarging our earlier sample of 14 stars to include 36 LMC Cepheids. The new calibration of the IRSB method is directly tied to the recent HST parallax measurements to ten MilkyWay Cepheids, and we find a LMC barycenter distance modulus of 18.45 +/- 0.04 (random error only) from the 36 individual LMC Cepheid distances. In the J, K bands we find identical slopes for the LMC and Milky Way PL relations and only a weak letallicity effect on the zero points (consistent with a zero effect), metal poor stars being fainter. In the optical we find the Milky Way slopes are slightly shallower than the LMC slopes (but again consistent with no difference in the slopes) and small effects on the zero points. However, the important Wesenheit index in V, (V - I) shows a metallicity effect on the slope and on the zero point which is likely to be significant. Conclusions. We find a significant metallicity effect on the W-VI index gamma(W-VI) = -0.23 +/- 0.10 mag dex(-1) as well as an effect on the slope. The K-band PL relation on the other hand is found to be an excellent extragalactic standard candle being metallicity insensitive in both slope and zero-point and at the same time being reddening insensitive and showing the least internal dispersion.en_US
dc.description.departmentMcDonald Observatoryen_US
dc.description.sponsorshipChilean Center for Astrophysics FONDAP 15010003en_US
dc.description.sponsorshipBASAL Centro de Astrofisica y Tecnologias Afines (CATA) PFB-06/2007en_US
dc.identifier.citationStorm, J., W. Gieren, P. Fouqué, T. G. Barnes, G. Pietrzyński, N. Nardetto, M. Weber, T. Granzer, and K. G. Strassmeier. >Calibrating the Cepheid period-luminosity relation from the infrared surface brightness technique-I. The p-factor, the Milky Way relations, and a universal K-band relation.> Astronomy & Astrophysics, Vol. 534 (Oct., 2011): A94.en_US
dc.relation.ispartofserialAstronomy & Astrophysicsen_US
dc.rightsAdministrative deposit of works to Texas ScholarWorks: This works author(s) is or was a University faculty member, student or staff member; this article is already available through open access or the publisher allows a PDF version of the article to be freely posted online. The library makes the deposit as a matter of fair use (for scholarly, educational, and research purposes), and to preserve the work and further secure public access to the works of the University.en_US
dc.subjectstars: variables: cepheidsen_US
dc.subjectstars: fundamental parametersen_US
dc.subjectmagellanic cloudsen_US
dc.subjectdistance scaleen_US
dc.subjectgravitational lensing experimenten_US
dc.subjecthigh-resolution spectroscopyen_US
dc.subjecttelescope key projecten_US
dc.subjectclassical cepheidsen_US
dc.subjectcolor relationsen_US
dc.subjecthubble constanten_US
dc.subjectastronomy & astrophysicsen_US
dc.titleCalibrating The Cepheid Period-Luminosity Relation From The Infrared Surface Brightness Technique II. The Effect Of Metallicity And The Distance To The LMCen_US
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