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

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

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

Stars Fundamental theory applied to a diffuse interstellar cloud that is collapsing under self-gravity Minimum fragment mass a robust but wrong 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

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

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 Disk galaxy star formation is inefficient, due to SN feedback Accretion and minor mergers renew gas supply Accretion, mergers and AGN outflows are key ingredients

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

Ultraluminous infrared galaxies and the galaxy luminosity function Sanders 1999

The red sequence evolves Bell et al Blanton 2006

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

More evidence for a shorter timescale Maraston 2006

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

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

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

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

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

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

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

Star Formation Rate Simulation The Mice (NGC 4676 a,b) old stars + gasdensity-dependent SFRshock-induced SFR Barnes (2004)

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

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

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

AGN ARE ANTI-HIERARCHICAL Hasinger et al. 2006

SMBH formation/feedback in galaxy spheroid formation 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 L Edd /c=GMM gas /r 2 L Edd  M SMBH black hole mass spheroid velocity dispersion

Triggered global star formation? OUTFLOWS FROM SMBH OVERPRESSUR E ISM CLOUDS star formation timescale t jet <<t gal yields high efficiency Labiano et al z=0.27 radio galaxy Saxton et al. 2005

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

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

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

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

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

Swinbank et al a SCUBA galaxy at z=2.385

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

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

A UNIFIED THEORY NEGATIVE POSITIVE

FRESH THEORETICAL INGREDIENTS ARE NEEDED!