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The Radial Profiles of Gas, Gas Metallicity and SFR in the SAMs for Molecular and Atomic Gas

The Radial Profiles of Gas, Gas Metallicity and SFR in the SAMs for Molecular and Atomic Gas. Fu Jian Max Planck Institute for Astrophysics, Garching 18/12/2012. Millennium and Millennium II Simulation. Millennium Simulation: Springel et al. 2005

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The Radial Profiles of Gas, Gas Metallicity and SFR in the SAMs for Molecular and Atomic Gas

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  1. The Radial Profiles of Gas, Gas Metallicity and SFR in the SAMs for Molecular and Atomic Gas Fu Jian Max Planck Institute for Astrophysics, Garching 18/12/2012

  2. Millennium and Millennium II Simulation • Millennium Simulation: Springel et al. 2005 • Millennium II Simulation: Boylan-Kolchin et al. 2009 • The mass resolution of MS-II is 125 larger than MS: use to study dwarf galaxies and small galaxies at high z

  3. Two phase interstellar gas in SAMs of galaxy formation • Galaxy formation models including only cold gas phase in ISM (e.g DLB07, Guo11, Bower et al. 2006) • Post-Processing models including molecular and atomic phase based on the outputs of models without two-phase gas (Obreschkow et al. 2009; Power et al. 2010) not self-consistent • Models including the atomic-molecular transition and star formation processes throughout the calculation (Cook et al. 2010; Fu et al. 2010; Lagos et al. 2011) • Trace the atomic and molecular gas radial profiles throughout the history

  4. The SAMs of galaxy formation including molecular gas and neutral gas Based on Munich L-Galaxies model by Guo et al. 2011 models with similar methods in Fu et al. 2010 (based on DLB07) • Multiple concentric ring for each disk • The H2 formation recipes • H2 prescription 1: Krumholz et al. 2009; Mckee & Krumholz 2010 • H2 prescription 2: Pressure related H2 fraction recipe • H2 proportional star formation law

  5. The star formation model Leroy et al. 2008 Schruba et al. 2011 Genzel et al. 2010 for high z

  6. The problem of gas consumption time scale when adopting H2 proportional star formation law • Too fast gas consumption in inner disk • because of star formation and SN feedback Improper gas surface density profiles compared to the observations Solution: Include the radial gas inflow → Too much gas in outer disks flows inward to compensate too fast gas consumption in inner disk

  7. Radial gas inflow and gas surface density profiles • Galaxy chemical evolution models with radial gas inflow: Lacey & Fall (1985) , Portinari & Chiosi (2000), Spitoni & Matteucci (2011), Schönrich & Binney (2009) etc. • Physical Mechanisms: • The mixing of cooling gas with existant disk gas causes the change of specific angular momentum of gas disk • Suppress the increase of specific angular momentum of gas disk caused by the difference of the gas consumption at different radius • Assumption:

  8. Radial gas inflow and gas surface density profiles Bigiel et al. 2012

  9. Gas metallicity radial gradients and mixing of metal elements from star formation • DLB07 & Guo11: all metal from star formation mix with cold gas, supernova reheat cold gas and metal into halo hot gas too high gas metallicity in inner disk region too shallow gas metallicity radial gradients compared to observations (e.g Moran et al. 2012) • New model: metal from SN directly mix with halo hot gas; metal from AGB star mix with disk cold gas • flatter gas metallicity gradients

  10. Mass functions at z=0

  11. The trends of gas metallicity gradients • Moran et al. 2012 :174 galaxies with M* >1010M⊙ from GASS survey: Galaxies with larger M* tends to have flatter metallicity gradients • Models give similar trends

  12. The size of star formation rate surface density profiles • Larger galaxies have larger size of (Leroy et al. 2008; Moran et al. 2012)

  13. The size of star formation rate surface density profiles • In the unit of r/rd, the size of and rd tend to be similar lSFR ~ l*~lH2 (similar to results in Leroy et al. 2008)

  14. The HI disk size and HI mass Broeils & Rhee 1997; Swaters et al. 2002 The inner disk has almost constant average HI surface density because of the transition between HI and H2

  15. Conclusions • Radial gas inflow can solve the problem of too fast gas consumption in inner disk and give proper gas surface density profiles when adopting H2 proportional star formation law. • The fraction of metal element directly mix with cold/hot gas components can affect the results of gas metallicity radial gradients. • Smaller galaxies tend to have larger gas metallicity gradients • Larger galaxies tend to have larger size of star formation rate surface density profiles, because all have similar tends. • The HI disk size and HI mass:

  16. Thank you!

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