An Initial Mass Function Study of the Dwarf Starburst Galaxy NGC 4214

Creators: Andrews, J. E.; Calzetti, D.; Chandar, R.; Lee, J. C.; Elmegreen, B. G.; Kennicutt, R. C.; Whitmore, B.; Kissel, J. S.; Da Silva, Robert L.; Krumholz, Mark R.; O'Connell, R. W.; Dopita, M. A.; Frogel, Jay A.; Kim, Hwihyun

Abstract

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_☉. 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 Hα luminosities, which needs to be taken into account when conducting this type of analysis.

Additional Information

© 2013 American Astronomical Society. Received 2012 November 13; accepted 2013 February 18; published 2013 March 25. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program GO-11360. We thank the referee for valuable comments on the paper. J.A. and D.C. acknowledge partial support for this study from the grant associated with program GO-11360 (PI: R. W. O'Connell), which was provided by NASA through the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. M.R.K. acknowledges support from an Alfred P. Sloan Fellowship, from the NSF through grant CAREER-0955300, and from NASA through a Chandra Space Telescope Grant and through Astrophysics Theory and Fundamental Physics Grant NNX09AK31G. The work of R.L.dS. is supported by a National Science Foundation Graduate Research Fellowship.

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