Star formation in blue compact dwarf Galaxies

S. Ramya1,2*, T. P. Prabhu1 and D. K. Sahu1
1Indian Institute of Astrophysics, Bengaluru 560 034, India
2Department of Physics, Bangalore University, Bengaluru, India

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Blue compact dwarf galaxies (BCDGs) are dwarfs undergoing current burst of star formation (SF). In our work, we determine the ages of the underlying old stellar population to be ~ 4 Gyr that is dominating the mass of the galaxy, underlying the current burst of SF. An intermediate population of ~ 500 Myr which dominates the stellar light from the galaxy is also detected. The burst of SF at the present epoch spans ~ 10 Myr as estimated from various age estimators like Hα, diagnostic diagrams and colour-colour diagrams. BCDGs undergo a burst of SF for a longer duration (of about a few 100 Myr to a Gyr) followed by a short/long quiescence. The amount of column density of localized neutral hydrogen required for the current burst to occur seems to be 1021 cm-2. This could be the threshold required for SF. Radio continuum emission reveals that the emission is coincident with the star forming regions. The star formation rates (SFR) estimated from Hα match well with the SFR estimated using non-thermal radio emission for individual star forming regions, but are ~ 6 - 7 times less as compared to the SFR calculated from far-IR (FIR) emission.

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Keywords : star forming regions; spectrum of star forming regions; Hα photometry; general - galaxies: dwarfs, blue compact dwarf galaxies, galaxies: stellar content