J/AJ/115/130 J/AJ/115/130 NGC 925 & NGC 1637 supergiants VRI CCD photometry Y -J Sohn T J Davidge Astron. J. 115 130 1998 1998AJ....115..130S J/AJ/112/2559 : Supergiants in NGC 672 (Sohn+ 1996) J/AJ/109/517 : Photoelectric types of bright galaxies (Buta+ 1995) Sohn & Davidge Paper I. 1996AJ....111.2280S Sohn & Davidge Paper II. 1996AJ....112.2559S, Cat. <J/AJ/112/2559> Photometry, CCD Photometry, VRI Stars, supergiant galaxies: individual (NGC 925, NGC 1637) galaxies: stellar content V, R, and I CCD images obtained with the Canada-France-Hawaii Telescope are used to investigate the bright stellar content of the barred spiral galaxies NGC 925 and NGC 1637. Not counting objects located in H II regions, we detect 295 supergiants in NGC 925 and 266 in NGC 1637. Comparisons with theoretical isochrones indicate that massive star formation in NGC 925 has been ongoing for at least a few tens of millions of years. Most of the supergiants in NGC 925 are younger than 20Myr and have masses between 10 and 60M_{sun}_. The majority of supergiants in NGC 1637 appear to be younger than 40Myr and have initial masses between 8 and 60 M_{sun}_. The luminosity functions of supergiants in both galaxies follow power laws with exponents d(logn)/d(logV)=0.50+/-0.05 for NGC 925 and 0.62+/-0.04 for NGC 1637. These values are shallower than what is seen in most spiral galaxies, although there are some exceptions. Archival Hubble Space Telescope images of NGC 925 are used to assess the effects of blending on our photometric measurements. We conclude that crowding could cause a flattening of the luminosity function and bias the brightnesses of the most luminous stars. The brightest red supergiants are used to estimate the distance moduli of these galaxies. After applying corrections for blending, we find that {mu}_0_=29.67 for NGC 925 and {mu}_0_=29.47 for NGC 1637, corresponding to linear distances of 8.6^+1.1^_-1.0_ and 7.8^+1.0^_-0.9_Mpc, respectively. The distance computed for NGC 925 is in good agreement with that recently derived from Cepheids.

NGC 92502 27 16.5+33 34 14 NGC 163704 41 28.1-02 51 53

[SD98] Identification number number=1 In Simbad, [SD98] NGC 925 NNN for table3.dat [SD98] NGC 1637 NNN for table4.dat --- Xc X coordinate number=2 The field centers are 2h 24m 16.5s +33deg 20' 48" (1950) for NGC 925 4h 38m 57.6s -02deg 57' 35" (1950) for NGC 1637 1 pix = 1.13". pix Yc Y coordinate number=2 The field centers are 2h 24m 16.5s +33deg 20' 48" (1950) for NGC 925 4h 38m 57.6s -02deg 57' 35" (1950) for NGC 1637 1 pix = 1.13". pix Vmag V magnitude mag e_Vmag rms uncertainty on Vmag mag V-I V-I colour index mag e_V-I rms uncertainty on V-I mag R-I R-I colour index mag e_R-I rms uncertainty on R-I mag HK1 HII region identification number=3 Hodge & Kennicutt (1983AJ.....88..296H) HII region identification <HK NGC 925 NNN> in Simbad. Only in table3.dat --- --- Dash --- HK2 HII region identification number=3 Hodge & Kennicutt (1983AJ.....88..296H) HII region identification <HK NGC 925 NNN> in Simbad. Only in table3.dat --- Patricia Bauer CDS 1998Mar09 UNKNOWN UNKNOWN Copied from the electronic version of AJ J_AJ_115_130.xml