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Formation of the Galaxies: Current Issues

Formation of the Galaxies: Current Issues. 2006. Joe Silk University of Oxford

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Formation of the Galaxies: Current Issues

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  1. Formation of the Galaxies:Current Issues 2006 Joe Silk University of Oxford Gainesville, October 2006

  2. Some remarks about star formation…mass, light, chemistry control galaxy evolution • Low mass stars control M • Solar mass stars control light in a spheroidal galaxy • The most massive stars dominate the light in a disk galaxy • Intermediate mass stars control chemical evolution

  3. THE INITIAL STELLAR MASS FUNCTION • What determines the characteristic mass of a star? Is the IMF universal? Kroupa 2004

  4. Stars • Fundamental theory applied to a diffuse interstellar cloud that is collapsing under self-gravity • Minimum fragment mass • a robustbutwrong result! • Resolution: continuing accretion of cold gas, eventually halted by feedback that taps stellar energy via MHD turbulence • first stars were massive • In addition IMF most likely also involves fragmentation

  5. 3 PROCESSES PLAY A ROLE:FRAGMENTATION, ACCRETION, FEEDBACK NGC1333: Quillen et al. 2006 Klessen 2006 Shu 2006 Shu 2006 Pudritz et al. 2006

  6. Disk galaxy star formation is inefficient, due to SN feedback Accretion and minor mergers renew gas supply Ellipticals are old because infall is quenched….by AGN outflows Efficient early star formation occurred in massive spheroids and ellipticals There are likely to be two modes of star formation: disks/pseudobulges AND elliptical/spheroid formation Accretion, mergers and AGN outflows are key ingredients

  7. theory (CDM-motivated) observations too many Dwarfs but they are fragile luminosity too many Giants: a problem! Galaxies • Gas cooling time-scale • Dynamical time-scale • A necessary condition for star formation is cooling: So the BIG ISSUE is astrophysical feedback

  8. Ultraluminous infrared galaxies and the galaxy luminosity function Sanders 1999

  9. The red sequence evolves Blanton 2006 Bell et al. 2004

  10. Star formation was efficient in the most massive galaxies Papovich et al. 2006

  11. More evidence for a shorter timescale Maraston 2006

  12. AN EFFICIENT MODE OF STAR FORMATION IS NEEDED FOR SPHEROID FORMATION: THE CASE FOR POSITIVE FEEDBACK D. Thomas D. Thomas 2006

  13. THERE ARE PLAUSIBLY TWO MODES OF STAR FORMATION: REGULATED BY GAS SUPPLY, DYNAMICAL TIMESCALE …. DISK MODE: motivated by gravitational instability of cold disks star surface density gas surface density Star formation efficiency SFE = gas vcool m*,SN ESN initial 0.02 SPHEROID MODE: motivated by gas-rich mergers

  14. A GLOBAL STAR FORMATION LAW FOR DISKS Sajina et al. 2006 SFR=0.02 (GAS SURFACE DENSITY)/tdyn fits quiescent and starburst galaxies Need cold gas accretion via infall and/or minor mergers to maintain global disk instability Need low efficiency: due to SN feedback

  15. NGC 891 LOCAL COLD GAS FEEDING BY INFALL NGC 6946 HI contours Oosterloo et al. 2005 Boomsma et al 2005

  16. The Rate of Star Formation Three-phase ISM Perhaps porosity self-regulates!

  17. SFR with SN feedback in a multiphase ISM Slyz et al. (2005)

  18. HISTORY OF STAR FORMATION Allard et al. 2006: M100 Rocha-Pinto 2000: solar vicinity

  19. Star Formation Rate Simulation The Mice (NGC 4676 a,b) old stars + gas density-dependent SFR shock-induced SFR Barnes (2004)

  20. GALAXY LUMINOSITY FUNCTION space density of galaxies AGN Feedback Bower et al. 2006 luminosity

  21. Massive spheroids form first K. Bundy et al. 2006 Cimatti et al. 2006

  22. Build-up of luminosity and star formation rate Bouwens, Illingworth et al 2006

  23. AGN ARE ANTI-HIERARCHICAL Hasinger et al. 2006

  24. SMBH formation/feedback in galaxy spheroid formation LEdd/c=GMMgas/r2 • Fits observed normalisation and slope King (2003), Silk & Rees (1998) • Supernovae provide feedback in potential wells of low mass galaxies • SMBH outflows provide positive feedback in massive protospheroids • Blowout occurs/star formation terminates when SMBH- relation is saturated LEddMSMBH black hole mass spheroid velocity dispersion

  25. Triggered global star formation? OUTFLOWS FROM SMBH OVERPRESSURE ISM CLOUDS star formation timescale tjet<<tgal yields high efficiency Saxton et al. 2005 Labiano et al. 2005 z=0.27 radio galaxy

  26. star formation rate compared to renormalised black hole feeding rate Silverman et al. 2006

  27. gravity-induced star formation jet-enhanced star formation in spheroids suppression by ouflows comoving star formation rate x 10-3 comoving SMBH accretion rate feedback redshift

  28. at z~2, SMBH fall below the relation Star formation suppressed Star formation triggered Borys et al 2006

  29. AGN-induced outflows & star formation Boost by ~10! Observed scaling!

  30. C. Martin 2005: KI and NaI line profiles OUTFLOWS FROM ULIRGS Morganti et al. 2005: HI absorption

  31. Swinbank et al. 2006 a SCUBA galaxy at z=2.385

  32. multiplicative factor of AGN-triggered SN Everett &Murray 2006: extended injection of energy needed for NGC 4151 outflow

  33. X-ray absorbed QSOs in ULIRGs Ultraluminous starbursts associated with AGN absorption by ionised wind M. Page et al. 2006

  34. A UNIFIED THEORY NEGATIVE POSITIVE

  35. FRESH THEORETICAL INGREDIENTS ARE NEEDED!

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