Origin of Bi-modality and Downsizing Avishai Dekel HU Jerusalem Galaxies and Structures Through Cosmic Times Venice, March 2006
Summary Q: z<2: Bright, red & dead, E s. No big blues..bi-modality, environment dependence A: Shutdown in M halo >10 12 Trigger: virial shock heating (threshold mass)..maintenance: AGN feedback Birnboim & Dekel 03 Dekel & Birnboim 06 Cattaneo, Dekel et al. 06 Q: z~2-4: Massive, high-sfr disks(?) A: Cold flows (+mergers) even in M halo ~10 12 Q: Downsizing? A1: Not anti-hierarchical for DM halos! A2: Feedback in M halo <10 12 & the shutdown in M halo >10 12 Neistein, van den Bosch & Dekel 06 Cattaneo, Dekel, Faber 06 Q: From the blue to the red sequence A: Two tracks: early/late shutdown, wet/dry mergers Dekel et al. 05; Dekel & Cox 06
Bi-modality in color, SFR, bulge/disk 0.65<z<0.75 E/S0/Sa Disks and Irregulars M *crit ~3x10 10 M ʘ Bell
Color-Magnitude bimodality & B/D depend on environment ~ halo mass environment density: low high very high disks spheroids SDSS: Hogg et al. 03 M halo <6x10 11 field M halo >6x10 11 cluster
Downsizing 0.65<z<0.75 E/S0/Sa z~0-1 z~3 Disks and Irregulars Bell
Observed Characteristic Scale bi-modality/transition at M * ~3x10 10 M ʘ ~L * M halo ~6x10 11 M ʘ below: disks, blue, star forming, in field (small halos) above: spheroids, red, old stars, clustered (massive halos) luminous red galaxies at early times z~0-2 early star formation, then shutdown big blue galaxies at very early times z~2-4 early star formation in big objects very blue gal s regulated starbursts
Standard Picture of Infall to a Disk Rees & Ostriker 77, Silk 77, White & Rees 78, Perturbed expansion Halo virialization Gas infall, shock heating at the virial radius Radiative cooling Accretion to disc if t cool <t ff Stars & feedback M<M cool ~10 12-13 M
Cooling vs Free Fall Rees & Ostriker 77, Silk 77, White & Rees 78 Blumenthal, Faber, Primack & Rees 86 T 10 4 10 5 10 6 10 7 +3 +1 galaxies Brems. log gas density -1-3 -5 H 2 CDM t cool <t ff H upper bound too He big clusters 10 30 100 300 1000 virial velocity
Growth of a Massive Galaxy T K 10 11 M ʘ 10 12 M ʘ shock-heated gas disc Spherical hydro simulation Birnboim & Dekel 03
A Less Massive Galaxy T K 10 11 M ʘ cold infall shocked disc Spherical hydro simulation Birnboim & Dekel 03
Hydro Simulation: ~Massive M=3x10 11 Kravtsov et al. virial shock z=4 M=3x10 11 T vir =1.2x10 6 R vir =34 kpc virial shock
Less Massive M=1.8x10 10 Kravtsov et al. cold virial radius infall z=9 M=1.8x10 10 T vir =3.5x10 5 R vir =7 kpc
Mass Distribution of Halo Gas disk cold flows density adiabatic infall shockheated Temperature Analysis of Eulerian hydro simulations by (Biernboim, Zinger, Kravtsov, Dekel)
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 t 1 < t 1 cool compress t compress 21ρ 5 & ρ 4 3 R V s
Shock Stability (Birnboim & Dekel 03) : post-shock pressure vs. gravitational collapse ln P stable: adiabatic: γ = Birnboim & Dekel 03 ln ρ γ > 4 / 3 with cooling rate q (internal energy e): γ eff d(lnp) d(lnρ) ρ q = γ & ρ e e& = PV& q s = 5 3 5 21 t t comp cool t comp 21ρ 5 & ρ 4 3 R V s t cool e q T ρλ( T, Z) T 3 V 16 2 ρ post 4ρ pre Stability criterion: γ eff 10 > 7 t 1 < t 1 cool compress
Shock-Heating Scale Birnboim & Dekel 03; Dekel & Birnboim 06 stable shock M vir [M ʘ ] 120 6x10 11 M ʘ unstable shock 250 300 100 V vir [km/s]
Fraction of cold/hot accretion SPH simulation Keres, Katz, Weinberg, Dav e 2004 sharp transition Z=0, underestimate M shock
Cold Flows in Typical Halos 10 13 M vir [M ʘ ] 10 12 10 11 M * of Press Schechter shock heating 1σ (22%) 2σ (4.7%) at z>1 most halos are M<M shock cold flows 0 1 2 3 4 5 redshift z
at High z, in Massive Halos: Cold Streams in a Hot Medium in M>M shock Totally hot at z<1 shock Cold streams at z>2 cooling no shock
Cold, dense filaments and clumps (50%) riding on dark-matter filaments and sub-halos Birnboim, Zinger, Dekel, Kravtsov
cold streams in hot media at high z Fraction of cold/hot accretion M>M shock SPH simulation Keres, Katz, Weinberg, Dav e 2004
Cold Streams in Big Galaxies at High z 10 14 10 13 M vir [M ʘ ] 10 12 all hot M shock ~M * cold filaments in hot medium M shock >>M * M shock 10 11 all cold 10 10 M * 10 9 0 1 2 3 4 5 redshift z
high-sigma halos: fed by relatively thin, dense filaments cold flows typical halos: reside in relatively thick filaments, fed spherically no cold flows the millenium cosmological simulation
Once the halo gas is shock heated, what keeps it hot? Feedback Processes
Once the gas is shock heated, what keeps it hot? 1 photo-ionization cold hot feedback strength UV on dust SN AGN + hot medium Supernova feedback is not effective in massive galaxies AGN feedback could be effective in massive galaxies dynamical friction in groups 0 Most efficient star formers: M halo ~10 11-12 10 9 10 10 10 11 10 12 10 13 10 14 M vir [M ʘ ]
Emission Properties vs. Stellar Mass low-mass emission galaxies are almost all star formers high-mass emission galaxies are almost all AGN Kauffmann et al. 2004
<M/L> has a minimum at M crit Using conditional luminosity function: Van den Bosch, Mo, Yang 03 M/L Supernova feedback Shock heating activates AGN feedback Most efficient star formers: M halo ~10 11-12 10 11 12 13 14 M
Supernova Feedback Scale (Dekel & Silk 86, Dekel & Woo 03) Energy fed to the ISM during the adiabatic phase: E SN νε M& t rad M * ( trad tff ) M& M * t ff 0.01 for Λ T 1 at T ~ 10 5 K Energy required for blowout: E M SN gas V 2 V 11 crit 120 km/s Mcrit 7 10 M o SN feedback only in small galaxies
Shock Heating Triggers AGN Feedback in M>M shock Enough energy in AGNs Hot, dilute gas is vulnerable to AGN feedback, while cold streams are shielded Shock heating is the trigger for AGN fdbk Kravtsov et al. M shock provides the threshold for shutdown, AGNs may provide long-term maintenance
Cosmological hydro simulations Slyz & Devriendt 2005 dark matter gas density temperature dilute gas is pushed away dense clumps are shielded
4. Origin of the Bi-modality Dekel & Birnboim 06 cold vs ungrouped vs SN feedback vs hot grouped AGN feedback 15
Two Key Processes: Cold flows star burst Streams collide near center -- isothermal shock & efficient cooling dense, cold slab star burst Disk can survive Hot medium halt star formation dilute medium vulnerable to AGN fdbk shock-heated gas never cools shut down disk and star formation
From blue sequence to red sequence Dekel & Birnboim 06 10 14 M vir [M ʘ ] 10 13 10 12 10 11 10 10 hot all cold M shock cold in hot 10 9 0 1 2 3 4 5 redshift z
z=0 In a standard Semi Analytic Model (GalICS) Cattaneo, Dekel, Devriendt, Guiderdoni, Blaizot 05 excess of big blue no red sequence at z~1 data --- sam --- color not red enough too few galaxies at z~3 color u-r star formation at low z magnitude M r
With Shutdown Above 10 12 M ʘ color u-r magnitude M r
Standard color u-r magnitude M r
With Shutdown Above 10 12 M ʘ color u-r magnitude M r
Environment dependence via halo mass Bulge to disk ratio
How Bright Ellipticals make it to the Red Sequence Two Types of tracks: (Cattaneo, Dekel, Faber 06) early growth & shutdown later growth & shutdown passive z=1 z=2 z=1 very bright blue z~3 z=3 ~bright blue z~2 z=2 z=3 magnitude M V magnitude M V dry mergers z=1 z=2 dry mergers z=1 early wet mergers z=3 wet mergers z=2 z=3 stellar mass stellar mass
Downsizing due to Shutdown Cattaneo, dekel, Faber 2006 massive normal, central normal, satellite z=1 z=1 z=1 z=1 in place by z~1 turn red after z~1 z=1 z=1 z=1 z=1
Downsizing by Shutdown at M halo >10 12 The bright red & dead E s are in place by z~1 while smaller E s appear on the red sequence after z~1 z=2 M halo >10 12 z=1 M halo >10 12 M halo >10 12 z=0 small satellite big small central
Downsizing by Shutdown at M halo >10 12 M vir [M ʘ ] 10 14 10 13 10 12 small enter the red sequence after z~1 10 11 10 10 big red & dead already all hot in place by z~1 merge into big halo all cold cold filaments in hot medium big small central small M satellite * M shock 10 9 0 1 2 3 4 5 redshift z
Downsizing by Feedback and Shutdown 1 cold hot feedback strength SN AGN + hot medium 0 Regulated SFR, keeps gas for later star formation in small halos Shutdown of star formation earlier in massive halos, later in satellites 10 9 10 10 10 11 10 12 10 13 10 14 M vir [M ʘ ]
Is Downsizing Anti-hierarchical? Merger trees of dark-matter halos M>M min z=2 Upsizing of mass in main progenitor z=1 Downsizing of mass in all progenitors >M min big mass small mass z=0
Natural Downsizing in Hierarchical Clustering Neistein, van den Bosch, Dekel 2006 Formation time when half the mass has been assembled EPS all progenitors downsizing main progenitor upsizing
Conclusions 1. Galaxy type is driven by dark-halo mass:...m crit ~10 12 M ʘ by shock heating (+feedback & clustering) 2. Disk & star formation by cold flows riding DM filaments 3. Early (z>2) big halos (M~10 12 )....big high-sfr galaxies by cold flows in hot media 4. Late (z<2) big halos M>10 12 (groups):...virial shock heating triggers AGN feedback. shutdown of star formation red sequence 5. Late (z<2) small halos M<10 12 (field): blue disks M * <10 10.5 6. Downsizing is seeded in the DM hierarchical clustering 7. Downsizing is shaped up by feedback & shutdown M>10 12 8. Two different tracks from blue to red sequence
Thank you