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Post Info TOPIC: Araucaria Project
Blobrana


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RE: Araucaria Project
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Title: The Araucaria Project: The distance to the Small Magellanic Cloud from near infrared photometry of Type~II Cepheids
Authors: Ciechanowska A., Pietrzynski G., Szewczyk O., Gieren W., Soszynski I

We have obtained deep near infrared J- and K-band observations of 14 BL Herculis and 5 W Virginis SMC stars from the OGLE III survey with the ESO New Technology Telescope equipped with the SOFI infrared camera. From these observations, period-luminosity (P-L) relations in the J and Ks 2MASS bands were derived. The slopes of the K and J band relations of -2.15 ± 0.19 and -1.95 ± 0.24, respectively, agree very well with the corresponding slopes derived previously for population II Cepheids in globular clusters, Galactic bulge and in the Large Magellanic Cloud. The distance modulus to the SMC obtained from our data using P-L relation derived for globular cluster Cepheids equals 18.85 ± 0.07 (statistical) ± 0.07 (systematic without including potential metallicity effect), which within the uncertainties agrees well with the results obtained with other methods.

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Blobrana


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Posts: 131433
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Title: The Araucaria Project. Infrared TRGB distances to the Carina and Fornax dwarf spheroidal galaxies
Authors: G. Pietrzynski, M. Gorski, W. Gieren, V. Ivanov, F. Bresolin, R.P. Kudritzki

We present distance determinations for two Local Group dwarf spheroidal galaxies, Carina and Fornax, based on the near-infrared magnitudes of the tip of the red giant branch (TRGB). For Carina we derive true distance moduli of 20.09 and 20.13 mag in the J and K bands, respectively, while for Fornax the same distance modulus of 20.84 mag was derived in both filters. The statistical errors of these determinations are of order 0.03-0.04 mag, whereas the systematic uncertainties on the distances are 0.12 mag in the J band and 0.14 mag in the K band. The distances obtained from the near-infrared TRGB method in this paper agree very well with those obtained for these two galaxies from optical calibrations of the TRGB method, their horizontal branches, RR Lyrae variables, and the near-infrared magnitudes of their red clumps.

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