Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007aas...211.1603d&link_type=abstract
American Astronomical Society, AAS Meeting #211, #16.03; Bulletin of the American Astronomical Society, Vol. 39, p.766
Astronomy and Astrophysics
Astronomy
Scientific paper
The star formation histories and evolution of 70 dwarf irregular galaxies that reside in differing local and global environments are investigated. The local environment is defined by the local galaxy number density, where high indicates at least one neighbor within 200 kpc and low indicates no neighbors within 1 Mpc. The global environment is classified as either the field or a galaxy group / cluster. The shallow gravitational potentials of dwarf irregular galaxies make these objects highly susceptible to changes in morphology or dynamics by external perturbations. Therefore, such galaxies are ideal candidates for a study of the role of environment in galaxy evolution.
Absolute magnitudes, colors, central surface brightnesses, and star formation rates were compared using photometry from UBVRIJHK and Hα imaging. With a high degree of statistical significance, galaxies in local high density environments have brighter central and effective surface brightnesses, while those in global high density environments have brighter absolute magnitudes, central and effective surface brightnesses, and higher star formation rates. However, no difference is seen among the different environments when considering star formation rates normalized by HI mass. Sersic profiles were fit to V and R band surface brightness profiles of the galaxies. No correlation exists between the structural characteristics and galaxy environment.
Spectral energy distribution models were generated by varying the rate of stellar formation and amplitude to replicate periodic burst and constant star formation rate scenarios, and compared to photometry. Of the 28 galaxies for which star formation history analysis was performed, roughly half were well fit by one of the models. Periodic burst systems account for roughly half of those galaxies, with the remaining galaxies being better represented by continuously star forming systems. The star formation histories are uncorrelated with the local and global environments.
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