Grzegorz Pietrzyński et al. 2006 ApJ 648 366 doi:10.1086/505786
Grzegorz Pietrzyński1,2, Wolfgang Gieren1, Andrzej Udalski2, Igor Soszyński1,2, Fabio Bresolin3, Rolf-Peter Kudritzki3, Ronald Mennickent1, Marcin Kubiak2, Michał Szymański2 and Sebastian Hidalgo4
Show affiliationsWe have obtained mosaic images of NGC 3109 in the V and I bands on 74 nights, spanning approximately 1 yr. From these data, we have conducted an extensive search for Cepheid variables over the entire field of the galaxy, resulting in the discovery of 113 variables with periods ranging from 3.4 to 31.4 days. In this sample, 76 Cepheids, including many long-period variables, were not known before. For the previously known 45 Cepheids in this galaxy, our data proved that reported periods were wrong for 14 objects; for nearly all other previously known Cepheid variables, we were able to significantly improve on the periods. We construct period-luminosity relations from our data and obtain reddening-corrected distance moduli of 25.72 ± 0.03 mag in V and 25.66 ± 0.03 mag in I. The distance modulus derived from the reddening-independent V-I Wesenheit index turns out to be significantly shorter (25.54 ± 0.03 mag), which indicates that in addition to the foreground extinction of E(B-V) = 0.05 mag, there is an intrinsic to NGC 3109 reddening of about 0.05 mag. Our distance obtained based on the reddening-free Wesenheit magnitudes is consistent with earlier distance determinations of NGC 3109 from Cepheids and the tip of the red giant branch. We improve on our distance and extinction determination combining our optical data with the follow-up near-infrared observations of a subsample of NGC 3109 Cepheids.
Cepheids; distance scale; galaxies: distances and redshifts; galaxies: individual (NGC 3109)
Issue 1 (2006 September 1)
Received 2006 February 27, accepted for publication 2006 May 9
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