The Distance of the LocalGroup Galaxy IC 1613 Obtained from Baade's Work on its Stellar Content
Abstract
Fiftynine variables were found by Baade over the face of IC 1613 from a series of plates taken with the 100inch reflector from 1929 to 1937. Of these, thirtyseven are definite Cepheids ranging in period from 146 days to 2 days, four are probable Cepheids, thirteen are irregular, one is a probable SRc, one is an eclipsing binary, and three are of unknown type. Photometry depends on a photoelectric sequence of thirtyeight stars measured with the 200inch reflector in the interval 11.6 < B < 21.7. Magmtndes of 279 secondary standards used for the variables have been determined relative to the basic sequence. The values are listed in the Appendix. Two interpretations of the periodluminosity relation are given for the Cepheids. The apparent blue modulus is (rn  M)AB = 24.55 as found from the most recent calibration of the PL relation. A reddening of E(B  V) 0.03 gives the true modulus as (m  Al)0 = 24.43. The integrated absolute magnitude of IC 1613 is MB = 14.45. The brightest blue supergiant is star 22A with ` B = 7.55. The brightest red supergiant is the irregular red variable V42 with MB = 6.05, or Mv 8.0 if B = V is assumed to be 2.0. The largest Hii region has a linear size of 167 pc. These absolute magnitudes and linear dimensions are much smaller than corresponding values in intrinsically brighter latetype galaxies. The total extent of the Population II component of IC 1613 is by 20;3, or 5600 by 4500 pc. The Population I component covers a region only half these dimensions.
 Publication:

The Astrophysical Journal
 Pub Date:
 May 1971
 DOI:
 10.1086/150939
 Bibcode:
 1971ApJ...166...13S