1. Neil Trentham September 7, 2004 What fraction of stars formed in infrared galaxies? Giavalisco et al. 2004

2. Neil Trentham September 7, 2004 Low obscuration in normal galaxies M74 is a Sc galaxy

3. Neil Trentham September 7, 2004 Heavy Obscuration in extreme galaxies Sanders et al. (1988) GRB 010222 host (Frail et al. 2001)

4. Neil Trentham March 26, 2004 Ramirez-Ruiz et al. (2002) Soifer et al. (1987) Berger et al. (1993): 4/20 GRB hosts have SFRs of about 500 M sun /yr. Others are much less.

5. Neil Trentham September 7, 2004

6. Neil Trentham September 7, 2004 Field galaxy evolution Dickinson et al. (2003) Van Dokkum et al. (2004)

7. Neil Trentham September 7, 2004 GRB host galaxy statistics Tanvir Tanvir Tanvir et al. (2004) Long-duration bursts appear to be linked to the deaths of massive stars and hence ongoing star formation. Berger et al. (2003) find 4/20 of their sample of well-localized GRB hosts are luminous IR galaxies. This suggests that 20-50% of cosmic star formation happened in IR galaxies.

8. Neil Trentham September 7, 2004 IR backgrounds + source counts Blain et al. (2002) AGNs not major contributor to IR background or would overproduce local MDO density. Adelberger & Steidel (2000)

9. Neil Trentham September 7, 2004 IMF considerations cB58 (z=2.7) Pettini et al.(2000) 30 Doradus Selman et al. (1999) Status of IMFs in starbursts reviewed 6/9. Can it be top-heavy in IR galaxies?

10. Neil Trentham September 7, 2004 Densities in IR galaxies Either 1)Much lower than ULIGs like Arp 220, which have above 100 M sun /pc 3 Or 2) Very active redistribution of stars (constraint on SSC sizes) Lamers et al. (2004)

11. Neil Trentham September 7, 2004 Summary 1.Considerations from optical Madau-Lilly plot and  (z) relation do not leave much room for IR galaxies. Possible disagreement from IR background considerations. 2.My best guesses are: f opt = 0.2, f IR,low = 0.6, f IR, high = 0.2 3.f(SFR) is probably bimodal. The IMF might be top heavy in IR galaxies but is not in UV luminous ones. 4.Strongest constraints will come from many measurements combined.