Distance and Reddening of the Isolated Dwarf Irregular Galaxy NGC 1156
Abstract
We present a photometric estimation of the distance and reddening values to the dwarf irregular galaxy NGC 1156, that is one of the best targets for the study of isolated dwarf galaxies in the nearby universe. We used imaging data sets of the Hubble Space Telescope (HST) Advanced Camera for Surveys, High Resolution Channel of the central region of NGC 1156 (26'' × 29'') available in the HST archive for this study. From the (U - B, B - V) color-color diagram, we first estimated the total (foreground + internal) reddening toward NGC 1156 of E (B - V) = 0.35±0.05 mag, whereas only the foreground reddening was previously known to be E (B - V) = 0.16 mag (1984, ApJS, 54, 33) or 0.24 mag (1998, ApJ, 500, 525). Based on the brightest-star method, selecting the three brightest blue supergiant (BSG) stars with a mean B magnitude of <B(3B)> = 21.94 and the three brightest red supergiant (RSG) stars with a mean V magnitude of <V(3R)> = 22.76, we derived the distance modulus to NGC 1156 to be (m - M)0,BSG = 29.16 mag and (m - M)0,RSG = 29.5 5 mag. By using weights of 1 for BSGs and 1.5 for RSGs, we finally obtained a weighted mean distance modulus to NGC 1156, (m - M)0 = 29.39 ± 0.20 mag (distance = 7.6 ± 0.7 Mpc), which is in agreement with previous estimates. Combining the photometry data of this study with those of Karachentsev, Musella, and Grimardi (1996, A&A, 310, 722) gives a smaller distance to NGC 1156, which is discussed together with the limits of the data.
- Publication:
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Publications of the Astronomical Society of Japan
- Pub Date:
- April 2012
- DOI:
- 10.1093/pasj/64.2.23
- arXiv:
- arXiv:1109.5780
- Bibcode:
- 2012PASJ...64...23K
- Keywords:
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- galaxies: dwarf irregular galaxies;
- galaxies: individual (NGC 1156);
- galaxies: photometry;
- Galaxy: globular clusters: individual (NGC 104);
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- 18 pages, 8 figures, Accepted by PASJ (2012 Apr issue)