The Araucaria Project: Distance to the Local Group Galaxy NGC 3109 from Near‐Infrared Photometry of Cepheids

We present near-infrared J- and K-band photometry of 77 Cepheid variables inthe Local Group galaxy NGC 3109. Combining our data with the previouslypublished optical V- and I-band photometry of Cepheids in this galaxy we derivean accurate distance and interstellar reddening to NGC 3109. Adopting adistance modulus of 18.5 mag for the Large Magellanic Cloud, we obtain a truedistance modulus to NGC 3109 of (m-M)_0 = 25.571 +- 0.024 mag (random error),corresponding to a distance of 1.30 +- 0.02 Mpc. The systematic uncertainty onthis value (apart from the adopted LMC distance) is of the order of +-3%, themain contributors to this value being the uncertainty on the photometric zeropoints, and the effect of blending with unresolved companion stars. The totalreddening determined from our multiwavelength solution is E(B-V)=0.087 +- 0.012mag. About half of the reddening is produced internal to NGC 3109. Our distanceresult is consistent with previous determinations of the distance to NGC 3109,but has significantly reduced error bars.Comment: Accepted for publication in Ap