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Session 12 - Distance Scale.
Display session, Monday, January 13
Metropolitan Ballroom,

[12.06] The Hubble Space Telescope Extragalactic Distance Scale Key Project: The Discovery of Cepheids in NGC 2090

S. Sakai (JPL), R. L. Phelps, W. L. Freedman (OCIW), B. Madore (NED/JPL/Caltech), A. Saha (STScI), P. B. Stetson (DAO), R. C. Kennicutt (Steward Obs.), J. R. Mould (MSSSO), L. Ferrarese (Caltech), H. C. Ford (Johns Hopkins), J. A. Graham (DTM), M. Han, J. G. Hoessel (U. Wisconsin), J. P. Huchra (CfA), S. M. G. Hughes (RGO), G. D. Illingworth (Lick Obs.), N. Silbermann (IPAC/JPL)

NGC 2090 is a highly resolved ScII galaxy with an inclination that makes it suitable for Tully-Fisher (TF) studies. The high probability of resolving individual Cepheid variable stars, and hence the prospect of refining the calibration of the TF relation, made NGC 2090 an ideal target for observations as part of the HST Extragalactic Distance Scale Key Project.

The HST observing sequence for NGC2090, incorporating 13 separate visits, has been completed. Thirteen F555W (V) and 5 F814 (I) cosmic-ray split images were obtained. In this paper we report on the detection of 34 Cepheid variables in NGC 2090, with periods ranging between 5 < P < 58 days.

Apparent V and I period-luminosity relations have been constructed, assuming a fiducial distance modulus, \mu_o = 18.50 \pm 0.10 mag and a reddening, E(B-V) = 0.10 mag for the Large Magellanic Cloud. A true distance modulus of 30.41 \pm 0.05 mag is found for NGC 2090, corresponding to a distance of 12.1 \pm 0.3 Mpc. The apparent moduli are found to be \mu_ I = 30.55 \pm 0.04 mag and \mu_ v = 30.66 \pm 0.05 mag, with an inferred reddening E(V-I) = 0.11 mag.

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