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MOLECULAR LINE PROBES OF STAR FORMATION LAWS IN GALAXIES

MOLECULAR LINE PROBES OF STAR FORMATION LAWS IN GALAXIES. Santiago GARCIA-BURILLO Observatorio Astronómico Nacional (OAN)-Spain. MOLECULAR LINE PROBES OF STAR FORMATION LAWS IN IR LUMINOUS GALAXIES. In collaboration with: Almudena Alonso-Herrero (CAB-CSIC)-Spain

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MOLECULAR LINE PROBES OF STAR FORMATION LAWS IN GALAXIES

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  1. MOLECULAR LINE PROBES OF STAR FORMATION LAWS IN GALAXIES Santiago GARCIA-BURILLO Observatorio Astronómico Nacional (OAN)-Spain

  2. MOLECULAR LINE PROBES OF STAR FORMATION LAWS IN IR LUMINOUS GALAXIES In collaboration with: Almudena Alonso-Herrero (CAB-CSIC)-Spain Javier Graciá-Carpio (MPG)-Germany Miguel Pereira-Santaella (CAB-CSIC)-Spain Luis Colina (CAB-CSIC)-Spain Pere Planesas (ALMA)-Chile Santiago Arribas (CAB-CSIC)-Spain

  3. SF Laws: Scaling Relations ρ(SFR) ~ ρgasα <---> ΣSFR ~ ΣgasαIfρ(SFR) ~ ρ / t free fall ~ ρgas1.5 Ifρ(SFR) ~ ρ x Ω ~ ρgas1.5 , in Q~1 disks In theory... Schmidt 1959; Silk 1997; Elmegreen 1997; Kennicutt 1998

  4. SF Laws: Scaling Relations ρ(SFR) ~ ρgasα <---> ΣSFR ~ ΣgasαIfρ(SFR) ~ ρ / t free fall ~ ρgas1.5 Ifρ(SFR) ~ ρ x Ω ~ ρgas1.5 , in Q~1 disks In theory... Schmidt 1959; Silk 1997; Elmegreen 1997; Kennicutt 1998 ΣSFR ?: UV, Hα, Pα, FIR, RC...Σgas ? : H2 (CO, HCN), HI, H2+HI… scales?: global, resolved, ... In practice...

  5. SF Laws: Scaling Relations ρ(SFR) ~ ρgasα <---> ΣSFR ~ ΣgasαIfρ(SFR) ~ ρ / t free fall ~ ρgas1.5 Ifρ(SFR) ~ ρ x Ω ~ ρgas1.5 , in Q~1 disks In theory... Schmidt 1959; Silk 1997; Elmegreen 1997; Kennicutt 1998 ΣSFR ?: UV, Hα, Pα, FIR, RC...Σgas ? : H2 (CO, HCN), HI, H2+HI… scales?: global, resolved, ... In practice... Star Formation Efficiency Power Laws for SFR SFE=SFR/Mgas ΣSFR ~ Σgasα ΣSFR ~ Σgas x Ω

  6. SF Laws: Scaling Relations Kennicutt 1998 Gas tracers: HI + CO(H2)Global fit on 100 galaxies; fit driven (?) by nuclear ‘extreme’ starbursts ΣSFR ~ Σgasα α~1.4 ΣSFR ~ Σgasα α~1.4 ΣSFR ~ Σgas x Ω

  7. SF Laws: Scaling Relations Bigiel et al 2008 Gas tracers: HI+CO(H2) Survey of 18 ‘normal’ SF galaxy disks with sub kpc-scale resolution ΣSFR ~ Σgasα α~1, if gas=H2

  8. SF Laws: Scaling Relations Genzel et al. 2010; see also Daddi et al 2010 A study of SF laws over cosmic time (´normal´ vs´extreme´ galaxies at all redshifts) SFE (mergers) ~ (5-6) x SFE (normal), for a given LCO ΣSFR(mergers) ~ 10 x ΣSFR(normal), for a given Σgas ΣSFR ~ Σgasα α~1.2

  9. SF Laws: ‘normal’ vs ‘extreme’ SF SFE=SFR/Mgas ΣSFR ~ Σgasα Any difference between ‘normal’ galaxies and ‘extreme SB’ if we use HCN as a tracer of Σgas ? HCN lines as a proxy for dense gas->change of SF laws? First studies point to no difference: ΣSFR~Σgasα, α~1 for ´all´ galaxies (e.g., Gao & Solomon 2004)

  10. Star Formation Efficiency: SFEdense ‘normal’ LIRGs+ULIRGs Gao & Solomon 2004 SFE dense=LFIR/LHCN ~ constant as a function of LFIR : from SFG to ´mergers´ However...

  11. Star Formation Efficiency: SFEdense 17 LIGs+ULIGs (Gracia-Carpio et al 2008) LIGs+ULIGs (Gracia-Carpio et al 2008) ‘normal’ LIRGs+ULIRGs Graciá-Carpio et al. 2008 New HCN data suggest higher SFEdense for LIGs and ULIGs

  12. Star Formation Efficiency: SFEdense LIGs+ULIGs (Gracia-Carpio et al 2008) high-z (Greve et al 2006) QSOs (Evans et al 2006) ‘normal’ LIRGs+ULIRGs Graciá-Carpio et al. 2008 New HCN data suggest higher SFEdense for LIGs and ULIGs

  13. Star Formation Efficiency: SFEdense ‘normal’ LIRGs+ULIRGs Graciá-Carpio et al. 2008 SFE dense (LIGs/ULIGs) ~ 3 x SFE dense (‘normal’ SFGs) LFIR~LHCN1.23 LFIR/LHCN constant but ~ LFIRn, n ~ 0.23

  14. SF Laws in LIRGs: a new sample García-Burillo et al. 2010, in prep Need of new HCN data for LIRGs: ´turning´ point in SF laws

  15. SF Laws in LIRGs: a new sample García-Burillo et al. 2010, in prep Need of new HCN data for LIRGs: ´turning´ point in SF lawsHCN / HCO+ IRAM 30m survey of 19 LIRGs: 99+19=28LIRGs extracted from 30 galaxy sample of Alonso-Herrero et al.2006 -30 nearby (v<5200km/s) LIRGs, 80% of RBGS sample -Sizes for dense molecular gas + SF disks < 10” << 30m-beam@88GHz‘Everything’ inside the beam-High-resolution imaging in several SF tracers-HST NICMOS Paα -CAHA + VLT Hα -Spitzer/MIPS 24mμCross-check of SFR values Spatially resolved images of SF: KS laws

  16. Star Formation Efficiency: SFEdense García-Burillo et al. 2010, in prep New data confirm enhanced SFE dense in LIRGs

  17. Star Formation Efficiency: SFEdense García-Burillo et al. 2010, in prep New data SFE dense=LFIR/LHCN constant but ~ LFIRn, n ~ 0.25 (+/-0.03)

  18. KS Laws for Dense Gas García-Burillo et al. 2010, in prep ΣSFR~Σndense , n~0.8 (+/- 0.05) for ‘normal’ galaxies

  19. KS Laws for Dense Gas García-Burillo et al. 2010, in prep ´normal´ vs ´IR luminous´bimodality? ΣSFR~Σndense , n~1.0 (+/- 0.05)for ‘LIRGs/ULIRGs’

  20. KS Laws for Dense Gas García-Burillo et al. 2010, in prep ΣSFR~Σndense , n~1.1 (+/- 0.03)global fit

  21. SF Laws in Galaxies: Bimodality? ´extreme´ SB (mergers)versus ´normal´ SF galaxies ΣSFR(mergers) ~ 10 x ΣSFR(normal), for a given Σgas ΣSFR(mergers) ~ 3 x ΣSFR(normal), for a given Σdense CO(mol. gas) HCN(dense mol. gas) Genzel et al. 2010 García-Burillo et al. 2010, in prep

  22. Conversion Factors: XHCNand SFEdense Graciá-Carpio et al. 2008 Extension of HCN + HCO+ -survey to J=3-2 lines LVG models One phase Two phases [HCN]/[HCO+] > 5-10 in most ULIRGsHCN ‘overabundance’ I nH2=105 cm-3,T=80K, [HCN]/[HCO+] ~103II nH2=104 cm-3,T=25K, [HCN]/[HCO+] ~1[HCN]/[HCO+] ~1 for LIRGs and ULIRGs!HCN ‘overabundance’vanishes! In either case: XHCN(LIRGs) ~ 3-5 x XHCN(ULIRGs)

  23. Conversion Factors: XHCNand SFEdense Graciá-Carpio et al. 2008 XHCN-conversion factor may be 3-5 times lower at high LFIR!!SFEdense=SFR/Mdensechanges by a factor ~3x(3-5) ~10 from ‘normal’ to ‘extreme’

  24. SF models: ‘local’ vs ‘global’ Krumholtz et al. 2009 (K09) HI/H2 fractionProperties of GMCsSFE = SFR ff/tff Analytic model for a ‘universal’ SF law: SF regulated by local processes within clouds: CO+HI SF laws vs model *Good agreement for ‘normal’ SFG*ΣSFR in ‘extreme’ SB underpredicted! Krumholtz et al. 2009

  25. SF models: ‘local’ vs ‘global’ Krumholtz et al. 2007 (K07) K07´s model underpredict SFEdense in ‘extreme’ SBs! Krumholtz et al. 2007 Failure of models focused on local processes suggest SF in ‘extreme’ SBsare driven by galactic-scale dynamical effects

  26. SF models: ‘local’ vs ‘global’ Genzel et al. 2010 SFR ~ Mgas1.4+/- 0.2 x Ω 0.8+/-0.2 CO(mol. gas)

  27. SF models: ‘local’ vs ‘global’ Genzel et al. 2010 SFR ~ Mgas1.4+/- 0.2 x Ω 0.8+/-0.2 CO(mol. gas) HCN ??(dense mol. gas)work in progress…

  28. SF models: ‘local’ vs ‘global’ Genzel et al. 2010 SFR ~ Mgas1.4+/- 0.2 x Ω 0.8+/-0.2 CO(mol. gas) HCN ??(dense mol. gas)work in progress… Two parameter fit makes `bimodality´ disappear Best fit implies power law indexes n ≠ 1 ?! ΣSFR ~ Σgas x Ω Silk 1997; Elmegreen 1997; Kennicutt 1998; Tan 2000; Tasker & Tan 2009

  29. CONCLUSIONS Observational evidence of bimodality in SF laws: ´normal´ SF galaxies (SFG) vs ´extreme´ SB (LIRGs/ULIRGs/SMGs) CO/HCN data suggest SFE and ΣSFR enhanced in ‘extreme’ SB Bimodality in SF laws may disappear if galactic-scale dynamical processes are explicitly included.

  30. CONCLUSIONS Observational evidence of bimodality in SF laws: ´normal´ SF galaxies (SFG) vs ´extreme´ SB (LIRGs/ULIRGs/SMGs) CO/HCN data suggest SFE and ΣSFR enhanced in ‘extreme’ SB Bimodality in SF laws may disappear if galactic-scale dynamical processes are explicitly included. Future directions… Multiline studies of molecular gas (CO, HCN,…,HCO+) -constrain (n(H2), Tk) and I->N(H2) conversion factors Spatially resolved SF laws at ~100pc scales -local ‘normal’ galaxies (NUGA; work in progress…) -local IR luminous galaxies (tbd)

  31. Star Formation Efficiency: SFEdense García-Burillo et al. 2010, in prep SFE dense=LFIR/LHCN constant but ~ LFIRn, n ~ 0.25 (+/-0.03)

  32. The SFE law: from z=0 to high-z galaxies NORMAL + LIGs A higher SFE in ULIGs/HyLIGS?or A contribution from embedded AGNs to LFIR?

  33. SF Laws in LIRGs/ULIRGs ‘normal’ LIRGs+ULIRGs Graciá-Carpio et al. 2008 Different SFEdense imply significant turn upward in KS law at high LFIRΣSFR~Σndense , n~0.9for ‘normal’ galaxies n~1.2for LIRGs/ULIRGs These results confirm predictions of Krumholz & McKee´s SF models

  34. LIRGs: a new sample HST NICMOS Paα images of LIRG sample FOV~19” Alonso-Herrero et al. 2006

  35. SF Laws: Scaling Relations Kennicutt 1998 ΣSFR ~ Σgasα α~1.4 ΣSFR ~ Σgas x Ω

  36. SF Laws: Scaling Relations Bouché et al 2007 ΣSFR ~ Σgasα α~1.7 ΣSFR ~ (Σgas x Ω)1.14

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