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26 April 2024 |
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The HI - Star Formation Connection: Open Questions | | Gerhardt R. Meurer
; O. Ivy Wong
; Daniel J. Hanish
; | | Date: |
19 Jun 2008 | | Abstract: | We show data from the Survey of Ionization in Neutral Gas Galaxies (SINGG)
and Survey of Ultraviolet emission in Neutral Gas Galaxies (SUNGG) which survey
the star formation properties of HI selected galaxies as traced by H-alpha and
ultraviolet emission, respectively. The correlations found demonstrate a strong
relationship between the neutral ISM, young massive stars, and the evolved
stellar populations. For example the correlation between R band surface
brightness and the HI cycling time is tighter than the Kennicutt-Schmidt Star
Formation Law. Other scaling relations from SINGG give strong direct
confirmation of the downsizing scenario: low mass galaxies are more gaseous and
less evolved into stars than high mass galaxies. There are strong variations in
the H-alpha to UV flux ratios within and between galaxies. The only plausible
explanations for this result are that either the escape fraction of ionizing
photons or the upper end of the IMF varies with galaxy mass. We argue for the
latter interpretation, although either result has major implications for
astrophysics. A detailed dissection of the massive star content in the extended
HI disk of NGC2915 provides a consistent picture of continuing star formation
with a truncated or steep IMF, while other GALEX results indicate that star
formation edges seen in Halpha are not always apparent in the UV. These and
other recent results settle some old questions but open many new questions
about star formation and its relation to the ISM. | | Source: | arXiv, 0806.3199 | | Services: | Forum | Review | PDF | Favorites | |
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