1 / 15

Equal- and unequal-mass mergers of disk and elliptical galaxies with black holes

Equal- and unequal-mass mergers of disk and elliptical galaxies with black holes. Peter Johansson University Observatory Munich. 8 th Sino-German workshop on galaxy formation and cosmology Kunming, February 26 th , 2009. Johansson, Naab , Burkert , 2009, ApJ , 690, 802.

primo
Download Presentation

Equal- and unequal-mass mergers of disk and elliptical galaxies with black holes

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Equal- and unequal-mass mergers of disk and elliptical galaxies with black holes Peter Johansson University Observatory Munich 8th Sino-German workshop on galaxy formation and cosmology Kunming, February 26th, 2009 Johansson, Naab, Burkert, 2009, ApJ, 690, 802

  2. The role of AGN feedback • 1) Observed relic supermassive black holes - quasars. • 2) Observed ULIRGs, merging galaxies with intense starburst and/or AGN activity. • 3) The observed MBH-σ & MBH-MBULGE relations. The coeval growth of black holes and galaxy bulges. • Simplified feedback energetics: SN/AGN- energy coupling/location: • Supernova II feedback • AGN feedback

  3. BH feedback model: Accretion • The Schwarzschild radius of a SMBH with M~107 Msunis RS~10-6 pc. Numerical Galaxy simulations at best resolve details down ~10 pc -> effective subresolution model. • Use the Tree-SPH GADGET-2 code (Springel et al. 2005) with cooling+SF+SNfeedback+BH feedback based on aBondi-Hoyle accretion model(Bondi 1952): α~100

  4. BH feedback model: Energetics • The radiative efficiency εr~0.1 (Sunyaev&Shakura 1973) and the thermal coupling εf~0.05 resulting in a total BH feedback energy efficiency of = 0.5%. • The SPH kernel is used to calculate the average gas density, temperature as well as the gas bulk velocity relative to the BH. • The BH mass grows stochastically by absorption of gas particles, include also smooth internal black hole mass, which is used to determine the accretion rate. • BHs will merge instantly if they come within a smoothing length and if their relative velocity is smaller than the local soundspeed. • Thermal FB energy distributed weighted within the SPH kernel.

  5. Model setup and BHs in isolated galaxies Isolated galaxies • Using the Springel (2000) method based on Hernquist (1993) we setup disk galaxies with Hernquist DM profiles+bulges& exponential discs with fgas=20%, 40%, 80%. • The BH is initially at rest in the centre of each model galaxy with a seed mass of 105 Msun. • We simulate a sample of isolated galaxies, 1:1 and 3:1 mergers, dry E-E and mixed E-Sp mergers.

  6. Numerical techniques ensuring BH merging 3:1 merger. Tests of BH merging prescription • The momentum is conserved in BH mergers. • For unequal-mass mergers ‘repositio-ning’ of the BHs at the position of the minimum of the potential. • The standard pre-scription is adequate for equal-mass mergers.

  7. 3:1 merger movie Total SFR Total MBH X-Y projection: Gas + BHs

  8. Varying the initial gas fraction and orbit 3:1 mergers • Variations in the initial gas mass fraction produce large differences in the final BH mass, 20%, 40%, 80%. • Variations in orbital geometry for a fixed initial gas mass fraction produce small differences in the final BH mass, shades of blue.

  9. BH accretion as a function of merger mass ratio • Systematic variations as a function of merger mass ratio.

  10. MBH-σ & MBH-M*relations for 3:1 and 1:1 mergers MBH-σ MBH-M* Lines: Observed relations - Tremaine et al. (2002) and Häring&Rix (2004).

  11. SFR&BH accretion for mixed and dry mergers Dry mergers (E-E) : fBH,ins~1-10% Mixed mergers (E-Sp): fBH,ins~20-30%

  12. MBH-σ & MBH-M*relations for mixed mergers MBH-σ MBH-M*

  13. MBH-σ & MBH-M*relations for dry mergers MBH-σ MBH-M*

  14. BHFP for disk and elliptical mergers 1:1 & 3:1 disk-disk mergers (Sp-Sp) Mixed&dry mergers (E-Sp&E-E) • Black hole fundamental plane (BHFP, Hopkins et al. 2007) MBH~s3.0±0.3R0.43±0.19or MBH~M*0.54±0.54s2.2±0.5. • Statistically equivalent formulation MBH-Ebind, Ebind~M*s2. • Lines: Observed relation from Hopkins et al. 2007: • log(MBH/Msun)=8.23±0.06+(0.71±0.06)log(M*σ2/ M0σ02)

  15. Conclusions/Summary • The simple BH accretion/feedback model works remarkably well in reproducing the observed MBH-σ,MBH-MBULGE & MBH-Ebindrelation for equal, unequal, E-E dry and mixed mergers. • The relation is the result of large-scale gas flows to the center of the galaxy and the self-regulation of MBH due to feedback energy. • Star formation is efficiently terminated in low merger ratio Sp-Sp mergers (≤3:1) and in mixed and dry mergers. • The global properties of the galaxy are insensitive to the details of the BH feedback model, but what about the detailed properties? Surface density profiles, kinematics, orbits... • Potential model improvements: Include spin of the BH, more physical accretion model, quasar mode vs. radio mode, jets....

More Related