Star formation in dwarf irregular galaxies NGC 6822

Abstract

view Abstract Citations (75) References (47) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Star Formation in Dwarf Irregular Galaxies: NGC 6822 Marconi, G. ; Tosi, M. ; Greggio, L. ; Focardi, P. Abstract Our proposed method to study the star-formation histories in nearby irregulars is here applied to NGC 6822. To this purpose we have obtained accurate CCD photometry of three regions in the galaxy, reaching V~23.5 with the required accuracy of σ_BVR_ <= 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. 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, and that the initial mass function exponent α is in the vicinity of Salpeter `s value, i.e., slightly flatter than in the solar neighborhood. The studied regions of NGC 6822 appear to contain different stellar populations. The preferred star formation regime for region A is a continuous activity coupled with a moderately flat α. For region C, instead, our best models suggest a discontinuous star formation and a moderately steep α. NGC 6822 is the last object of our original sample of five nearby irregulars. We can then draw the scenario resulting from this sample: most of the observed fields appear to have experienced a gasping regime of star formation, with average exponent α =2.35 for the initial mass function. Despite their small sizes, the majority of the sample galaxies contain different stellar populations in different regions. Publication: The Astronomical Journal Pub Date: January 1995 DOI: 10.1086/117265 arXiv: arXiv:astro-ph/9409013 Bibcode: 1995AJ....109..173M Keywords: Dwarf Galaxies; Histories; Irregular Galaxies; Star Formation; Astronomical Photometry; Charge Coupled Devices; Color-Magnitude Diagram; Computerized Simulation; Galactic Evolution; Star Formation Rate; Stellar Luminosity; Astronomy; GALAXIES: INDIVIDUAL: NGC 6822; GALAXIES: IRREGULAR; STARS: FORMATION; GALAXIES: STELLAR CONTENT; Astrophysics E-Print: plain Tex format full text sources arXiv | ADS | data products SIMBAD (1781) NED (5) CDS (1)