The Main Mode of Galaxy/Star Formation? Avishai Dekel, HU Jerusalem Leiden, September 2008 HU Flow Team Birnboim, Freundlich, Goerdt, Neistein, Zinger Simulations Teyssier, Pichon, Kravtsov Massive Disk Buildup & Breakup by Cold Streams at z=2-3

Outline Massive galaxies at high z: ‘’narrow cold streams through hot halos Inflow rate into the halo and into the disk Smooth flows vs Mergers High-SFR galaxies at z=2-3 Disk breakup and bulge formation

Shock-Heating Scale M vir [M ʘ ] Birnboim & Dekel 03 Dekel & Birnboim 06 stable shock unstable shock typical halos 6x10 11 M ʘ Keres et al 05

Gas through shock: heats to virial temperature compression on a dynamical timescale versus radiative cooling timescale Shock-stability analysis (Birnboim & Dekel 03): post-shock pressure vs. gravitational collapse

The Critical Mass: Cosmological Simulations virial radius SPH Keres et al 2005, AMR Kravtsov et al M<<10 12 M ʘ cold flows M>10 12 M ʘ virial shock heating

Fraction of Cold Gas in Halos: Cosmological simulations (Kravtsov) ‏ Birnboim, Dekel, Neistein 2007 cold hot Zinger, Birnboim, Dekel, Kravtsov

Libeskind, Birnboim, Dekel 08 d(Entropy)/dt A virial shock in a 3D cosmological simulation: at M crit – rapid expansion from the inner halo to R vir

Cold Streams in Hot Massive Halos at High z Dekel & Birnboim 2006 Dekel et al. 2008

At High z, in Massive Halos: Cold Streams in Hot Halos Totally hot at z<1 in M>M shock Cold streams at z>2 shock no shock cooling Dekel & Birnboim 2006

density Temperature adiabatic infall shock- heated cold flows disk Analysis of Eulerian hydro simulations by Birnboim, Zinger, Dekel, Kravtsov Mass Distribution of Halo Gas

M*M* M vir [M ʘ ] all hot redshift z all cold cold filaments in hot medium M shock M shock >>M * M shock ~M * Cold Streams in Big Galaxies at High z Dekel & Birnboim 06 Fig. 7

the millenium cosmological simulation high-sigma halos: fed by relatively thin, dense filaments → cold narrow streams typical halos: reside in relatively thick filaments, fed ~spherically → no cold streams

M s ~M * M s >>M * Large-scale filaments grow self-similarly with M * (t) and always have typical width ~R * ∝M * 1/3 At high z, M shock halos are high-σ peaks: they are fed by a few thinner filaments of higher density Origin of dense filaments in hot halos ( M ≥ M shock ) at high z At low z, M shock halos are typical: they reside in thicker filaments of comparable density

Dark-matter inflow in a shell 1-3R vir M>>M * radial velocity temperature density one thick filament several thin filaments Seleson & Dekel M~M *

M*M* M vir [M ʘ ] all hot redshift z all cold cold filaments in hot medium M shock M shock >>M * M shock ~M * Cold Streams in Big Galaxies at High z

Gas Density in Massive Halos 2x10 12 M ʘ Ocvirk, Pichon, Teyssier 08 high z low z M=10 12 M ʘ

Critical Mass in Cosmological Simulations Ocvirk, Pichon, Teyssier 08 M stream M shock DB06 cold filaments in hot medium

Observed Maximum Bursts - Optical/UV-selected galaxies at z~ M star ~10 11 M ʘ SFR ~ 200 M ʘ yr -1 - Most of the mass is bursting -> gaseous input - Very rapid SFR: burst ~0.5 Gyr...t SFR < R vir /V vir ~ t cool << t Hubble - Disk morphology & kinematics: no major mergers Genzel et al. 2006, …

Massive high-z disks by cold narrow streams Dekel et al. 2008, Nature MareNostrum AMR simulation 50 Mpc cosmological box 1 kpc resolution Ocvirk, Pichon, Teyssier 2008 M vir =10 12 M ʘ at z=2.5

Gas density following dark-matter filaments

Entropy: virial shock & low-entropy streams

Inward gas flux: all in the streams.

Another example Always 3 streams?

Flux per solid angle

Average Assembly Rate into R vir by EPS Neistein, van den Bosch, Dekel 06; Birnboim, Dekel, Neistein 07; Neistein & Dekel 07, 08 Growth rate of main progenitor (time invariant): Approximate for LCDM ~ M=2x10 12 M ʘ z=2.2  dM/dt ~ 200 M ʘ yr -1 May explain high-SFR galaxies if - a similar flux penetrates to the disk - it is gas rich - SFR follows rapidly

Inflow Rate into the Disk ~~ At z~2-3, M~10 12 M ʘ, the input rate into the disk is comparable to the infall rate into the virial shock, most of it along narrow streams

Conditional Distribution of Gas Inflow Rate mergers >1:10 smooth flows

Assume scaling of P(Mdot|M) ‏ P(M) by Sheth-Tormen Comoving Number Density of Galaxies as a function of gas inflow rate Gas inflow rate > SFR but by a small margin  SFR very efficient! Star-Forming Gal’s Sub-Millimeter Gal’s SFR= prediction, e.g., n=2x10 -4 SFR<200

Contribution of Different Masses <12.5

At Different Redshifts 3 4 similar n(>SFR) at z=2-3

Streams in 3D: partly clumpy

Half the stream mass is in clump >1:10 Birnboim, Zinger, Dekel, Kravtsov

Inflow Rate into the Disk 50% of the flux is in mergers > 1:10 but the duty cycle is < 10%

Fraction of Mergers BzK/BX/BM are mostly mini-minor mergers <1:10, i.e. smooth flows Bright SMG are half-and-half mergers >1:10 and smooth flows SFG: Stream-Fed Galaxies At a given Mdot, 75% of the galaxies are fed by smooth flows

M*M* M vir [M ʘ ] all hot redshift z all cold cold filaments in hot medium M shock Stream Flux in halos of M at z

Streams – Clumpy Disk - Bulge ~ One stream with impact parameter ~ R disk determines the disk spin, while other streams generate turbulence The streams provide continuous rapid gas supply into a disk  Jeans instability At z>2, the streams maintain high dispersion:  Giant clumps. They interact, lose AM, and coalesce into a compact spheroid - “classical bulge” (Noguchi 99; Elmegreen, Bournaud, Elmegreen 08)

merger h halos accretion disk Old Paradigm radiative cooling cold hot cold gas  young stars spheroid  old stars

hot halo spheroid clumpy disk New Paradigm z>2 clumpy disk spheroid cold streams hot halo thick disk M v >10 12 z<1 new disk

Detectable by absorption: External source: c.d.>20 cm -2 at 30% sky coverage Internal source: c.d.>21 cm -2 at 5% sky coverage Column density of cold, in-streaming gas

Here is what it should look like in H α

M*M* M vir [M ʘ ] all hot redshift z all cold cold filaments in hot medium M shock M shock >>M * M shock ~M * When and where did most stars form? Dekel & Birnboim 06 ~ at z=2-3 in galaxies of ~10 11 M ʘ by cold streams

Conclusions: SFG = Stream-Fed Galaxies =2-3,~ At z=2-3, “disks” of ~10 11 M ʘ grow rapidly via narrow cold gas streams through shock-heated halos ~~ 200 M ʘ yr -1 Penetration: disk input rate ~ halo entry rate ~ 200 M ʘ yr -1 Streams are half Streams are half clumps >1:10 and half smooth, merger duty cycle <0.1 ~~ Abundance: SFR>150 at n~3x10 -4, SFR>500 at n~6x10 -5 Most sBzK/BX/BM are fed by smooth streams in halos M ʘ Half the SMG are mergers >1:10 At z>2, streams generate rotation & maintain gas-rich & turbulent disk  giant clumps  (1) SFR & (2) coalescence into a spheroid The cold streams should be detectable at z>2 in absorption and emission (DLAS? Lyman-limit? Lyman-alpha emitters?) ‏ Observed SFGs  SFR must closely follow gas input rate