J. E. Andrews, D. Calzetti, R. Chandar, J. C. Lee, B. G. Elmegreen, R. C. Kennicutt, B. Whitmore, J. S. Kissel, Robert L. da Silva, Mark R. Krumholz, R. W. O'Connell, M. A. Dopita, Jay A. Frogel, Hwihyun Kim
The production rate of ionizing photons in young < 8 Myr, unresolved stellar clusters in the nearby irregular galaxy NGC 4214 is probed using multi-wavelength Hubble Space Telescope WFC3 data. We normalize the ionizing photon rate by the cluster mass to investigate the upper end of the stellar initial mass function (IMF). We have found that within the uncertainties the upper end of the stellar IMF appears to be universal in this galaxy, and that deviations from a universal IMF can be attributed to stochastic sampling of stars in clusters with masses < 10^3 M_sun. Furthermore, we have found that there does not seem to be a dependence of the maximum stellar mass on the cluster mass. We have also found that for massive clusters, feedback may cause an underrepresentation in Ha luminosities, which needs to be taken into account when conducting this type of analysis.
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http://arxiv.org/abs/1302.5006
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