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J/AJ/105/894      Star formation in DDO 210 and NGC 3109         (Greggio+ 1993)

Star formation in dwarf irregular galaxies: DDO 210 and NGC 3109 GREGGIO L., MARCONI G., TOSI M., FOCARDI P. <Astron. J. 105, 894 (1993)> =1993AJ....105..894G
ADC_Keywords: Galaxies, optical; Photometry, CCD; Positional data Abstract: The method proposed in Paper I [Tosi et al., AJ, 102, 951 (1991)] to study the star formation histories in nearby irregulars is here applied to the galaxies DDO 210 and NGC 3109. To this purpose we have obtained deep CCD photometry of two regions in DDO 210 and three regions in NGC 3109, reaching V = 24 with the required accuracy of Sigma(V) ≤ 0.1 mag. Major information on the stellar populations, star formation rates, and initial mass functions of these regions in the last 1 Gyr are derived from the comparison of the observational color-magnitude diagrams and luminosity functions, with the corresponding synthetic diagrams and luminosity functions generated by a numerical simulation code based on stellar evolutionary tracks. In general, for both galaxies we find that in the last 1 Gyr the star formation activity has been rather continuous, possibly occurring in long episodes of moderate activity separated by short quiescent periods. According to our models the metallicity should be fairly low (in the range 0.05 ≤ Z/Zsun ≤ 0.5) and the initial mass function exponent in the vicinity of Salpeter's value, i.e., slightly flatter than in the solar neighborhood. The studied regions of NGC 3109 appear to contain different stellar populations (i.e., with slightly different metallicity and star formation histories), whereas those of DDO 210 seem to have fairly similar stellar contents, although for this galaxy the interpretation is more uncertain. As a by-product of our method we find that the distance modulus to DDO 210 should be (m-M)0 approx. 28, which places this galaxy beyond the edge of the Local Group. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2a.dat 45 435 Principal parameters from the selected stars in DDO 210 region A table2b.dat 45 148 Principal parameters from the selected stars in DDO 210 region B table3a.dat 56 1020 Principal parameters from the selected stars in NGC 3109 region A table3b.dat 56 653 Principal parameters from the selected stars in NGC 3109 region B table3c.dat 56 933 Principal parameters from the selected stars in NGC 3109 region C
Byte-by-byte Description of file: table2a.dat table2b.dat
Bytes Format Units Label Explanations
1- 3 I3 --- N Star number 4- 14 F11.6 pix X X pixel coordinate, referred to the bottom left corner of each frame 15- 25 F11.6 pix Y Y pixel coordinate 26- 35 F10.6 mag V V magnitude 36- 45 F10.6 mag B-V B-V color
Byte-by-byte Description of file: table3a.dat table3b.dat table3c.dat
Bytes Format Units Label Explanations
1- 4 I4 --- N Star number 5- 15 F11.6 pix X X pixel coordinate, referred to the bottom left corner of each frame 16- 26 F11.6 pix Y Y pixel coordinate 27- 36 F10.6 mag Vmag V magnitude 37- 46 F10.6 mag B-V B-V color 47- 56 F10.6 mag V-R V-R color
Note: The tables contains the data for all the objects detected with photometric error smaller than 0.1 mag. Origin: AAS CD-ROM series, Volume 1, 1993
(End) Patricia Bauer [CDS] 20-Jun-1994
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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