A.Kravtsov (U.Chicago) D. Ceverino (NMSU) O. Valenzuela (U.Washington) G. Rhee (UNLV) F. Governato, T.Quinn, G.Stinson (U.Washington) J.Wadsley (McMaster, Canada) Galaxy Formation

Hydrodynamic simulations of galaxies Rotation Curves and ISM of Dwarf Galaxies

Numerical simulations : recent progress Stellar Disk and Bulge: is there a thin disk? Is bulge too massive? Angular momentum Tully-Fisher relation Feedback How gas gets to the disk? Mbaryons/Mhalo ratio

Robertson et al Abadi et al 2003 Hydrodynamical simulations of galaxy formation in a cosmological context. ( DM particles) ( DM particles) gasstars

A LCDM galaxy at z=0 Governato et al 04 Age > 10 Gyr Age < 10 Gyr Only Stars are shown (brighter colors for younger ages) boxes 40 kpc across Disk Bulge + Stellar Halo N>

Increasing Resolution Conserves Angular Momentum in Disks 4000 DM DM DM If DM+stellar component not collisionless: Massive halo particles exchange E and J with disk particles ---> disks heat and lose angular momentum

Angular momentum of Stellar Disks increases with resolution. Galaxies still too concentrated Abadi et al Governato et al (see also Robertson 05 Okamoto 05) stars

High Spin Halo (0.05) Vc =170Km/sec Low Spin Halo (0.01) Vc =70Km/sec Due to sufficient resolution 300pc disks form with the right angular momentum Credits: Governato

8 10^11 solar masses3 10^12 solar masses Galaxies too concentrated. B/D 1:3 or higher. Peak velocity higher than in the real Milky Way. No realistic feedback yet! Governato et al. 04 Abadi et al 03 Governato

The Feedback and satellites : No Feedback.UV+SN Feedback Red: stars Blue: gas Total Mass 3e12 Msol Spin Parameter = Vrot Max 270 Km/sec Formation time z = 0.75 Last major merger z=3 Frame size ~ 200 Kpc

12 F.Governato: simulations with GASOLINE

13

14 F.Governato : simulations with GASOLINE

How gas gets to the disk The old picture is wrong: do not even think about spherical accretion and shocking to virial temperature Still not clear what fraction of gas comes with satellites and what comes with filaments

1 Mpc scale 100 kpc scale T gas Gas density Credits: Kravtsov 100pc resolution Z=4

350kpc Z=2.5 40pc resolution. Mvir(z=0)=1.e12Msun. Ndm=400K

350kpc Z=2.5

115kpc

7kpc

Isolated galaxies Observations Simulations

Simon etal 04: NGC 4605 Vmax =100km/s -- Usual problems with NFW. -- Disk is important: normal M/L R =1 M/L K = 0.5 1arcmin

Simon etal 04 NGC 4605 POSS II Changes in PA and inclination in central 1kpc are consistent with a weak bar

DDO 47: Vmax = 80km/s Distance = 4Mpc HI is very lumpy Stellar light does not align with HI

A large fraction of dwarf Galaxies in the central 1kpc has a maximal disk with expected stellar population (judging by colors). Signs of a weak bar are frequent. ISM is very clumpy. Observations:

LMC HI distribution Venn+Stavely Smith 2003) Cosmological Simulations: feeback, 300pc resolution … Governato 2004 Multiphase ISM is nicely reproduced

Valenzuela et al 05 Isolated Galaxy: NFW halo1-2M particles Exponential disk 200K particles Gas100K Resolution pc Star formation, feedback …. Stars: phase-on Two simulations: dwarf: 60km/s M33-type: 120km/s Code: GASOLINE

Stars Young Stars T<0.5G yrs Cold Gas T<1.5e4 Hot Gas T=1e5 K

Cold Gas T<1.5e4 Hot Gas T=1e5 K Stars Young Stars T<0.5G yrs

Cold gas hardly shows any traces of the bar. Filaments and lumps of cold gas Large bubbles filled by 10 5 K gas Stellar feedback feeds the multiphase ISM

Rotation Curves: Cold and Hot gas Little difference

Gas Rotation Circular Velocity Asymmetric drift (aka random motions) cannot help to explain why gas rotates too slow Rms Velocities < 20km/s

Recovering total density

Another simulation: dwarf 5 Resolution: 60pc stars Cold gas dm baryons Gas rms velocity Valenzuela, Rhee, Klypin, Governato et al Models of NGC3109 and NGC6822

Cold Gas density in the central 2kpc region: Clear signs of multiphase medium

Cold/Hot Gas: density Stars Cold Gas:velocity

NGC 6822 Observations Vcirc(total) Magellanic-type dwarf irregular 0.5Mpc from Milky Way

-In dwarf galaxies gas does not rotates fast enough: Vgas < Vcirc -Non-circular velocities are not large enough to account for the difference -Pressure support from 1e5K gas is one of key ingredients Core is ‘observed’ where there is a real cusp. CONCLUSIONS

Structure of the ISM at z= 0.5 ( several 10^6 particles per halo, gas clouds resolved down to 10^5 solar masses ) Ram Pressure Stripping Cold Gas in Disks High Velocity Clouds Gas Rich Satellites Hot Halo (Blue)

Bars in galaxies: Simulations with ART and Gadget pc resolution 200K disk particles 2M dm particles. Dt =1e4 yrs