The HI - Star formation connection: Open questions

Gerhardt R. Meurer, O. Ivy Wong, Daniel J. Hanish

Research output: Chapter in Book/Conference paperConference paperpeer-review

1 Citation (Scopus)


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 Hα 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 Hα 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 NGC 2915 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 Hα 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.

Original languageEnglish
Title of host publicationThe Evolution of Galaxies Through the Neutral Hydrogen Window
Number of pages7
Publication statusPublished - 2008
Externally publishedYes
EventThe Evolution of Galaxies Through the Neutral Hydrogen Window - Arecibo, Puerto Rico
Duration: 1 Feb 20083 Feb 2008

Publication series

NameAIP Conference Proceedings
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616


ConferenceThe Evolution of Galaxies Through the Neutral Hydrogen Window
Country/TerritoryPuerto Rico


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