The Jeans Conjecture and the IMF Desika Narayanan Bart J Bok Fellow - PowerPoint PPT Presentation

The Jeans Conjecture and the IMF Desika Narayanan Bart J Bok Fellow University of Arizona (with Romeel Davé) Monday, August 13, 12

Is the IMF at high- z Top-Heavy? Indirect evidence from z ~2 SFRs Davé 2008 Monday, August 13, 12

Is the IMF at high- z Top-Heavy? Indirect evidence from z ~2 SFRs Davé 2008 Wilkins & Trentham (2008) Narayanan & Davé (2012) Monday, August 13, 12

Is the IMF at high- z Top-Heavy? Wilkins & Trentham (2008) Narayanan & Davé (2012) Davé 2008 van Dokkum 2008 Monday, August 13, 12

Is the IMF at high- z Top-Heavy? Wilkins & Trentham (2008) Narayanan & Davé (2012) Davé 2008 van Dokkum 2008 Tacconi 2008 Monday, August 13, 12

Is the IMF at high- z Top-Heavy? (then how are their descendents bottom-heavy?) y v a e H m o t t o B y l g n i s a e r c n I Conroy & van Dokkum 2012 Monday, August 13, 12

Gadget: to get model discs and Sunrise: to get dust mergers at z=0,2 temperatures Jonsson et al. 2006, 2009 Springel et al. 2003-2005 Jonsson & Primack 2010 T.J. Cox et al. 2005-2008 Monday, August 13, 12

Assumption: M crit ~ M J André et al. 2010 Monday, August 13, 12

M J ~ T 3/2 / n 1/2 becomes efficient scales with SFR CI/CII at n~10 4 cm -3 HI H 2 CI/CII CI/CII HI H 2 CI/CII CO H 2 CO H 2 H 2 H 2 CO H 2 CO CO CI/CII HI H 2 CO CO CI/CII CO H 2 CO CO CO H 2 CO H 2 CO H 2 H 2 CI/CII CI/CII HI CI/CII H 2 CI/CII Av ~ 1 CI/CII HI ∑ GMC > 100 M ⦿ pc -2 Krumholz, McKee & Leroy (2011) Narayanan et al. (2011b) Desika Narayanan Monday, August 13, 12

M J ~ T 3/2 / n 1/2 becomes efficient scales with SFR at n~10 4 cm -3 Narayanan & Davé 2012 Monday, August 13, 12

M J ~ T 3/2 / n 1/2 M halo SFR M c Kroupa M/L Narayanan & Davé (in prep.) Monday, August 13, 12

M J ~ T 3/2 / n 1/2 M halo n~10 4 -10 5 cm -3 T gas ~ T dust SFR M c Kroupa M/L Narayanan & Davé (in prep.) Monday, August 13, 12

z=0-2 SFR-M * relation Model IMF SFRs Invariant IMF SFRs Narayanan & Davé (2012) Desika Narayanan Monday, August 13, 12

Comparing Cosmic SFR Density Evolution against Stellar Mass buildup Narayanan & Davé (2012) Desika Narayanan Monday, August 13, 12

M J ~ T 3/2 / n 1/2 M halo n~10 4 -10 5 cm -3 T gas ~ T dust SFRs < SFR MW SFR T gas < 10 K M c Kroupa M/L Narayanan & Davé (in prep.) Monday, August 13, 12

Narayanan & Davé (in prep.) Monday, August 13, 12

Conclusions Under the Jeans Assumption: 1. Dust-gas coupling can raise temperatures in high- z galaxies enough to drive top-heavy/bottom-light IMFs 2. Decreased SFRs in gas where CRs dominate the temperature can promote bottom-heavy IMFs at low- z: More massive galaxies have increasingly bottom-heavy IMFs at z ~0 Do the Jeans properties of GMCs relate at all to the stellar IMF? Monday, August 13, 12