The HI-H 2 Transition and Star Formation in Early-Type Galaxies

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The Molecular Fraction: HI Detected Early-Types ------ Krumholz et al. 2009 model Model assumptions: ζ’t=G’0 Z=1.0 Z=1.7 Z’d=Z’g=Z’ May not hold in Early-Types Fit Paramaters: Z=5 Z=1.3 Log 10 (Z)== -0.2 to 0.4 (e.g. Kuntschner et al. 2010) ϕ mol =10; ϕ CNM ~10 NGC 3032 and NGC 4150: High F mol at low Σ tot Z=17 Z=1.0 Both galaxies show indications of recent interactions or gas accretion! 10
Rmol-Pressure Relation Recall that Elmegreen’s (1993) model predicts: • Several studies of the HI and H2 maps of nearby spiral galaxies find that the molar fraction, Rmol, is a tight function of the midplane hydrostatic pressure (Blitz & Rosolowsky 2004, 2006; Leroy et al. 2008) • Blitz & Roslolowsky (2006) specifically find: where • The j(Z) dependence is assumed to be subsumed into this empirical relationship. 11
Page 1 and 2: The giant elliptical galaxy ESO 325
Page 3 and 4: Motivation It is well known that m
Page 5 and 6: Results NGC 807 Five Detections: N
Page 7 and 8: HI detected HI non-detected UGC 150
Page 9: Σcrit Versus Σtot
Page 13 and 14: Blitz & Rosolowsky 2006; Leroy et a
Page 15 and 16: ρs is constant over Hg? s>>Hg H Ko
Page 17 and 18: ρs is constant over Hg? s>>Hg H Az
Page 19 and 20: ρ s Constant with H g ? The MGE st
Page 21 and 22: Koyama & Ostriker 2008 ----> Hg: 5-
Page 23 and 24: Koyama & Ostriker 2008 ----> 23 Gas
Page 25 and 26: Rmol-Pressure Relation •Early-typ
Page 27 and 28: Summary • Observed HI surface den

The HI-H 2 Transition and Star Formation in Early-Type Galaxies

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