THE CARNEGIE HUBBLE PROGRAM: THE LEAVITT LAW AT 3.6 {mu}m AND 4.5 {mu}m IN THE LARGE MAGELLANIC CLOUD
- Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)
- NASA Goddard Space Flight Center, Code 665, Greenbelt, MD 20771 (United States)
- Astronomy Department, Boston University, 725 Commonwealth Avenue, Boston, MA 02215 (United States)
The Carnegie Hubble Program is designed to improve the extragalactic distance scale using data from the post-cryogenic era of Spitzer. The ultimate goal is a determination of the Hubble constant to an accuracy of 2%. This paper is the first in a series on the Cepheid population of the Large Magellanic Cloud, and focusses on the period-luminosity (PL) relations (Leavitt laws) that will be used, in conjunction with observations of Milky Way Cepheids, to set the slope and zero point of the Cepheid distance scale in the mid-infrared. To this end, we have obtained uniformly sampled light curves for 85 LMC Cepheids, having periods between 6 and 140 days. PL and period-color relations are presented in the 3.6 {mu}m and 4.5 {mu}m bands. We demonstrate that the 3.6 {mu}m band is a superb distance indicator. The cyclical variation of the [3.6]-[4.5] color has been measured for the first time. We attribute the amplitude and phase of the color curves to the dissociation and recombination of CO molecules in the Cepheid's atmosphere. The CO affects only the 4.5 {mu}m flux making it a potential metallicity indicator.
- OSTI ID:
- 22004950
- Journal Information:
- Astrophysical Journal, Vol. 743, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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