Table 2 - uploaded by Ji Hoon Kim
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Many results in modern astrophysics rest on the notion that the Initial
Mass Function (IMF) is universal. Our observations of a sample of HI
selected galaxies in the light of Halpha and the far-ultraviolet (FUV)
challenge this result. The extinction corrected flux ratio Halpha/FUV
from these two tracers of star formation shows strong correlations w...
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Citations
... But the computational approach has changed dramatically through the discovery of the IGIMF Theory in 2003 (Kroupa and Weidner 2003). The generic prediction of the IGIMF theory that the GWIMF steepens at high stellar masses with decreasing galaxy-wide SFR, has been confirmed by observations of thousands of star forming galaxies (Gunawardhana et al. 2011;Hoversten and Glazebrook 2008;Lee et al. 2009;Meurer et al. 2009). ...
... Before briefly explaining this computational approach it is useful to address the perhaps most important observational evidence which unambiguously indicates a systematic change of the GWIMF from top-light at very low star formation rates (SFRs) to top-heavy at high SFRs. Surveys of hundreds and thousands of starforming galaxies have used various photometric tracers such as H˛flux to test for the high-mass end of the GWIMF, UV flux to test for the intermediate mass stellar population and red broadband colors to test for the intermediate and lower-mass end of the GWIMF (Gunawardhana et al. 2011;Hoversten and Glazebrook 2008;Lee et al. 2009;Meurer et al. 2009). The data analysis and the investigations of various biases such as from dust attenuation, loss of photons and others, is highly involved and reported in these works in much detail. ...
Until recently the great majority of naturalists believed that species were immutable productions, and had been separately created. This view has been ably maintained by many authors. Some few naturalists, on the other hand, have believed that species undergo modification, and that the existing forms of life are the descendants by true generation of preexisting forms.
Few intergalactic, plausibly primordial clouds of neutral atomic hydrogen (H(i)) have been found in the local Universe, suggesting that such structures have either dispersed, become ionized or produced a stellar population on gigayear timescales. The Leo ring, a massive (M(H(i)) approximately 1.8 x 10(9)M[symbol: see text], M[symbol: see text] denoting the solar mass), 200-kpc-wide structure orbiting the galaxies M105 and NGC 3384 with a 4-Gyr period, is a candidate primordial cloud. Despite repeated atttempts, it has previously been seen only from H i emission, suggesting the absence of a stellar population. Here we report the detection of ultraviolet light from gaseous substructures of the Leo ring, which we attribute to recent massive star formation. The ultraviolet colour of the detected complexes is blue, implying the onset of a burst of star formation or continuous star formation of moderate (approximately 10(8)-yr) duration. Measured ultraviolet-visible photometry favours models with low metallicity (Z approximately Z[symbol: see text]/50-Z[symbol: see text]/5, Z[symbol: see text] denoting the solar metallicity), that is, a low proportion of elements heavier than helium, although spectroscopic confirmation is needed. We speculate that the complexes are dwarf galaxies observed during their formation, but distinguished by their lack of a dark matter component. In this regard, they resemble tidal dwarf galaxies, although without the enrichment preceding tidal stripping. If structures like the Leo ring were common in the early Universe, they may have produced a large, yet undetected, population of faint, metal-poor, halo-lacking dwarf galaxies.
