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					The Prospect of Observing the KS Relation at High-z



                    Desika Narayanan
                    Harvard-Smithsonian CfA



    Chris Hayward        T.J. Cox             Lars Hernquist
        Harvard            Carnegie              Harvard
 Kennicutt-Schmidt SFR Laws




Locally: Bigiel 2008; Krumholz et al. 2009
        Molecular Kennicutt-Schmidt SFR Laws

    Local: CO J=1-0               z~2: CO (J=3-2)




S
F
R




          Total H2 Gas Mass




Gao & Solomon 2004


                                  z~2 Bouché et al. 2007
Theoretical Approach: SPH simulations of
                galaxies
                                           Prescriptions for multi-phase
                                           ISM (McKee-Ostriker)

                                           SF (volumetric Schmidt law)

                                           BH growth and associated
                                           Feedback
              QuickTime™ and a
                decompressor
        are neede d to see this picture.


                                           Halos scaled to z~2 concentration

                                           For z~2 study, isolated galaxies
                                           Mbar ~ 1011 M, MMW disks


                                           SF follows SFR   1, 1.5, 2
    Springel et al. (2003-2005)
Non-LTE Radiative Transfer (Synthetic Molecular Line Emission)
•   3D Monte Carlo code developed based on improved Bernes (1979) algorithm
•   Considers full statistical equilibrium with collisional and radiative processes
•   Sub-grid algorithm considering mass spectrum GMCs as SIS; Mcloud=104-106 M, (Blitz
    et al. 2006, Rosolowsky 2007, Bolatto et al. 2008)
•   Uniform Galactic CO Abundance, no H2 at NH < 1021 cm-2




                             Desika Narayanan   SFR@50, Spineto       DN+ 2006,2008
                         SUNRISE (dust RT) to ‘Select’ Galaxies

                                    Diffuse ISM
         GMC




Physics Included in Monte Carlo IR RT:
-IR transfer of stellar and AGN spectrum
(starburst 99 for stars and Hopkins+ 07 for AGN)

-dust radiative equilibrium

-Kroupa IMF, ULIRG/SMG DTG (same as MW
DTM)

-Stellar Clusters surrounded by HII regions
and PDRs (MAPPINGS; Groves et al. 2008)

   Jonsson, Groves & Cox (2009)
        Does Differential Excitation Matter?:
             Local Universe Example
  CO (J=1-0)                          CO (J=3-2)




                                 Index = 1.0




        SFR ~ CO (1-0)1.5              SFR ~ CO (3-2)0.9



                             Narayanan et al. 2005
Gao & Solomon 2004           Iono et al. 2008
           Molecular Kennicutt-Schmidt SFR Laws

        CO J=1-0                         HCN J=1-0




     Index = 1.5                      Index = 1.0




                         Gao & Solomon (2004)
SF follows SFR   1.5
           Molecular Kennicutt-Schmidt SFR Laws

     CO (J=1-0)                        CO (J=3-2)




                                    Index = 1.0




             SFR ~ CO (1-0)1.5            SFR ~ CO (3-2)0.9



                                 Narayanan et al. 2005
  Gao & Solomon 2004             Iono et al. 2008
SF follows SFR   1.5
 Differential Excitation; Underlying n=1.5 KS Index
         SFR-CO index           SFR-HCN index

          CO (J=1-0)                      HCN (J=1-0)


                  CO (J=3-2)




                               Krumholz & Thompson 2007
                               Narayanan et al. 2008


SF follows SFR   1.5
HCN (HCN (J=3-2) Observational Survey




                Bussmann, DN, Shirley, Wu,
                Juneau, Vanden Bout, Solomon et al. (2008)
      HCN (HCN (J=3-2) Observational Survey




Bussmann, DN, Shirley, Juneau et al. 2008
Getting to the KS Relation at z~2




                      SF follows SFR   1, 1.5, 2
Getting to the KS Relation at z~2




                      SF follows SFR   1, 1.5, 2
            Getting to the KS Relation at z~2




                               SFR-LCO index versus Transition
                               for KS = 2 galaxies
SF follows SFR   1, 1.5, 2
     Mapping the CO 3-2 KS relation at z~2 to the underlying
                  volumetric Schmidt Relation




Physical KS index vs. SFR-CO (J=3-2) index   Data from Tacconi et al. 2010:

                                             SFR ~ L(CO3-2)0.97
                        Conclusions




1. Excitation Matters
                        Conclusions




1. Excitation Matters




2. Getting the KS
relation at high-z is
feasible (now!)
GADGET SPH Simulations

                                          Prescriptions for multi-phase
                                          ISM (McKee-Ostriker), SF,
                                          BH growth and associated
                                          Feedback (though BH winds turned
                                          off)

                                          100 galaxies used:
                                                    20 disk Galaxies
                                                    80 merger snapshots


                                          SF follows SFR   1.5

                                          Assuming the free-fall time argument
                                          for SFR ~  1.5 holds




Springel et al. (2003-2005),

                  Desika Narayanan   SFR@50, Spineto
     Can we Recover the Basic Relations?
         SFR-CO index                   SFR-HCN index

                                                HCN (J=1-0)
           CO (J=1-0)
SFR ~    1.5 (assumed   Schmidt Law)
                 CO (J=3-2)
              (observed)
SFR ~ Lmol
Lmolecule ~  


Then =1.5/
So we need to understand how line luminosity varies
with gas density


SF follows SFR   1.5                    Narayanan et al. 2008
SFR ~  1.5 (assumed Schmidt Law)
SFR ~ L Fiducial Disk Galaxy
                 (observed)
         molecule

Lmolecule ~       Then =1.5/
                               V200=115 km/s
                               fgas=0.2

                       CO (J=1-0)




                                    Narayanan et al. 2008
SFR ~  1.5 (assumed Schmidt Law)
SFR ~ L Fiducial Disk Galaxy
                 (observed)
         molecule

Lmolecule ~       Then =1.5/
                               V200=115 km/s
                               fgas=0.2

Then =1.5/           Low ncrit


                             Increasing density will
                             increase the gas mass,
                             thus increasing the CO (1-0)
                             luminosity proportionally




                                       Narayanan et al. 2008
SFR ~  1.5 (assumed Schmidt Law)
SFR ~ L Fiducial Disk Galaxy
                 (observed)
         molecule

Lmolecule ~       Then =1.5/
                               V200=115 km/s
                               fgas=0.2

Then =1.5/           High ncrit




                                    Narayanan et al. 2008
SFR ~  1.5 (assumed Schmidt Law)
SFR ~ L Fiducial Disk Galaxy
                 (observed)
         molecule

Lmolecule ~       Then =1.5/
                               V200=115 km/s
                               fgas=0.2

Then =1.5/



                             Increasing density will
                             increase the gas mass,
                             thus increasing the CO (1-0)
                             luminosity proportionally




                                 <n> >> ncrit slope=1.5
                                 <n> << ncrit slope < 1.5

				
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posted:8/24/2012
language:English
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