1. Speaker: Bingxiao Xu Peking University
Galaxy Bulge Formation: Interplay with Dark Matter Halo and Central Supermassive Black Hole
Speaker: Bingxiao Xu
Peking University

2. Outline Introduction Galaxy Bulge Formation (Gravothermal Instability)
Stellar Feedback in Bulge Formation
Obscured Black Hole Growth
Discussion and Conclusion

3. Introduction Baryon component: disk + bulge (elliptical) Observations:
Bulge formation ≠ disk formation
High SFR (relatively short formation timescale)
Similarity in comoving space density:
High redshift starburst galaxies are the progenitors of the local spheroidal component

4. Galaxy Merger Angular momentum can be efficiently removed
Central starburst is triggered

5. Observational Contradiction
Some high-redshift starburst galaxies don’t show clear evidence of galaxy merge !
Large scale star formation region (~10kpc)
Monolithic Collapse Scenario
Large amount of gas collapse and turn into star in a short time
(Eggen, Lynden-Bell & Sandage, 1962)

6. Modeling Detail Inner NFW Density Profile Polytropic Gas Sphere
Hydrostatic Equilibrium Equation

7. Gravothermal Instability
Self-gravity will change the thermal properties of the syetem (negative heat capacity)
Method: see the change of dP/dV with fixed encolsed mass M at every radius R
dP/dV>0: gravothermal unstable
dP/dV<0: gravothermal stable

8. Analysis Result P_c -- Gamma Relation Isothermal Gas Sphere
Collapsed Gas Mass:

9. Stellar Feedback Supernova Explosion Stellar Wind
Neglecting the heating effects (extremely dense environment )
Momentum Deposition Rate:
The outward momentum feedback will make the star formation in proto-bulge self-regulated!

10. Obscured Black Hole Growth
The star-forming region can not extend to innermost region (galactic nuclear)
Inward Stellar Feedback Should Exist!
Necessity:
To conserve the local momentum
To confine and obscure central SMBH growth (recent SMGs observations)

11. Sketch Map
Balance Condition:
SMTH feedback = Inward stellar feedback

12. Modeling Result Star Formation Rate Star Formation Efficiency
M_{BH}-Sigma Relation
M_{BH}-M_{Bulge} Relation

13. Discussion & Conclusion
The onset of gravothermal Instability is more possible for smaller polytropic index (near-isothermal distribution ).
The outward stellar feedback resists the gravity to make the star formation self-regulated while the inward feedback confine and obscure the SMTH growth.
Extremely high SFR & SFE can be derived, and the BH-Bulge relations are insensitive to the primordial gas fraction.
astro-ph/ ApJ in press

14. Thank you!