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J/AJ/115/130      NGC 925 & NGC 1637 supergiants VRI CCD photometry (Sohn+ 1998)

VRI CCD photometry of supergiant stars in the barred galaxies NGC 925 and NGC 1637 Sohn Y.J., Davidge T.J. <Astron. J. 115, 130 (1998)> =1998AJ....115..130S
ADC_Keywords: Stars, supergiant ; Photometry, VRI ; Photometry, CCD Keywords: galaxies: individual (NGC 925, NGC 1637) - galaxies: stellar content Abstract: 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. The majority of supergiants in NGC 1637 appear to be younger than 40Myr and have initial masses between 8 and 60 M. 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 µ0=29.67 for NGC 925 and µ0=29.47 for NGC 1637, corresponding to linear distances of 8.6+1.1-1.0 and 7.8+1.0-0.9Mpc, respectively. The distance computed for NGC 925 is in good agreement with that recently derived from Cepheids. Objects: ---------------------------------------------------------- RA (2000) DE Designation(s) ---------------------------------------------------------- 02 27 16.5 +33 34 14 NGC 925 04 41 28.1 -02 51 53 NGC 1637 ---------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table3.dat 60 437 Positions, magnitudes and colors of NGC 925 stars table4.dat 60 435 Positions, magnitudes and colors of NGC 1637 stars
See also: J/AJ/112/2559 : Supergiants in NGC 672 (Sohn+ 1996) J/AJ/109/517 : Photoelectric types of bright galaxies (Buta+ 1995) Byte-by-byte Description of file: table3.dat table4.dat
Bytes Format Units Label Explanations
1- 3 I3 --- [SD98] Identification number (1) 5- 12 F8.3 pix Xc X coordinate (2) 14- 20 F7.3 pix Yc Y coordinate (2) 22- 26 F5.2 mag Vmag V magnitude 28- 31 F4.2 mag e_Vmag rms uncertainty on Vmag 33- 37 F5.2 mag V-I V-I colour index 39- 42 F4.2 mag e_V-I rms uncertainty on V-I 44- 48 F5.2 mag R-I R-I colour index 50- 53 F4.2 mag e_R-I rms uncertainty on R-I 55- 56 I2 --- HK1 ? HII region identification (3) 57 A1 --- --- [,] Dash 59- 60 I2 --- HK2 ? HII region identification (3)
Note (1): in Simbad, <[SD98] NGC 925 NNN> for table3.dat <[SD98] NGC 1637 NNN> for table4.dat Note (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". Note (3): Hodge & Kennicutt (1983AJ.....88..296H) HII region identification <HK NGC 925 NNN> in Simbad. Only in table3.dat
History: Copied from the electronic version of AJ References: Sohn & Davidge Paper I. 1996AJ....111.2280S Sohn & Davidge Paper II. 1996AJ....112.2559S, Cat. J/AJ/112/2559
(End) Patricia Bauer [CDS] 09-Mar-1998
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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