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Title: An IMF Study of the Dwarf Starburst Galaxy NGC 4214
Authors: 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 ionising 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 normalise the ionising 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 solar masses. 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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Title: The dust SED of dwarf galaxies I. The case of NGC 4214
Authors: Israel Hermelo, Ute Lisenfeld, Monica Relaņo, Richard J. Tuffs, Cristina C. Popescu, Brent Groves

The goal of the present study is to establish the physical origin of dust heating and emission based on radiation transfer models, which self-consistently connect the emission components from diffuse dust and the dust in massive star forming regions. NGC 4214 is a nearby dwarf galaxy with a large set of ancillary data, ranging from the ultraviolet (UV) to radio, including maps from SPITZER, HERSCHEL and detections from PLANCK. We mapped this galaxy with MAMBO at 1.2 mm at the IRAM 30 m telescope. We extract separate dust emission components for the HII regions (plus their associated PDRs on pc scales) and for the diffuse dust (on kpc scales). We analyse the full UV to FIR/submm SED of the galaxy using a radiation transfer model which self-consistently treats the dust emission from diffuse and SF complexes components, considering the illumination of diffuse dust both by the distributed stellar populations, and by escaping light from the HII regions. While maintaining consistency with the framework of this model we additionally use a model that provides a detailed description of the dust emission from the HII regions and their surrounding PDRs on pc scales. Due to the large amount of available data and previous studies for NGC 4214 very few free parameters remained in the model fitting process. We achieve a satisfactory fit for the emission from HII+PDR regions on pc scales, with the exception of the emission at 8\mi, which is underpredicted by the model. For the diffuse emission we achieve a good fit if we assume that about 30-70% of the emission escaping the HII+PDR regions is able to leave the galaxy without passing through a diffuse ISM, which is not an unlikely scenario for a dwarf galaxy which has recently undergone a nuclear starburst. We determine a dust-to-gas mass ratio of 350-390 which is close to the expected value based on the metallicity.

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Hubble's newest camera has taken an image of galaxy NGC 4214.

This galaxy glows brightly with young stars and gas clouds, and is an ideal laboratory to research star formation and evolution.
Dwarf galaxy NGC 4214 may be small, but what it lacks in size it makes up for in content. It is packed with everything an astronomer could ask for, from hot, young star-forming regions to old clusters with red supergiants.
The intricate patterns of glowing ionised hydrogen gas, cavities blown clear of gas by stellar wind, and bright stellar clusters of NGC 4214 can be seen in this optical and near-infrared image, taken using the Wide Field Camera 3 (WFC3) instrument on the NASA/ESA Hubble Space Telescope.

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Zooming in on NGC 4214

NGC 4214 is a barred irregular galaxy located around 10 million light-years away in the constellation Canes Venatici.
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Ed ~ The galaxy hosted Supernova 2010U



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