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Enhancing and inhibiting star formation: High-resolution simulation studies of the impact of cold accretion, mergers and feedback on individual massive galaxies

Proceedings of the International Astronomical Union 8:S295 (2012) 13-16

Authors:

LC Powell, F Bournaud, D Chapon, J Devriendt, V Gaibler, S Khochfar, A Slyz, R Teyssier

Abstract:

The quest for a better understanding of the evolution of massive galaxies can be broadly summarised with 2 questions: how did they build up their large (stellar) masses and what eventually quenched their star formation (SF)? To tackle these questions, we use high-resolution ramses simulations (Teyssier 2002) to study several aspects of the detailed interplay between accretion (mergers and cold flows), SF and feedback in individual galaxies. We examine SF in major mergers; a process crucial to stellar mass assembly. We explore whether the merger-induced, clustered SF is as important a mechanism in average mergers, as it is in extreme systems like the Antennae. We find that interaction-induced turbulence drives up the velocity dispersion, and that there is a correlated rise in SFR in all our simulated mergers as the density pdf evolves to have an excess of very dense gas. Next, we introduce a new study into whether mechanical jet feedback can impact upon the ability of hot gas haloes to provide a supply of fuel for SF during mergers and in their remnants. Finally, we briefly review our recent study, in which we examine the effect of supernova (SN) feedback on galaxies accreting via the previously overlooked cold-mode, by resimulating a stream-fed galaxy at z ~ 9. A far-reaching galactic wind results yet it cannot suppress the cold, filamentary accretion or eject significant mass in order to reduce the SFR, suggesting that SN feedback may not be as effective as is often assumed. © 2013 International Astronomical Union.
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Synthetic X-ray spectra for simulations of the dynamics of an accretion flow irradiated by a quasar

ArXiv 1207.7194 (2012)

Authors:

SA Sim, D Proga, R Kurosawa, KS Long, L Miller, TJ Turner
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The Epoch of Disk Settling: z~1 to Now

ArXiv 1207.7072 (2012)

Authors:

Susan A Kassin, Benjamin J Weiner, SM Faber, Jonathan P Gardner, CNA Willmer, Alison L Coil, Michael C Cooper, Julien Devriendt, Aaron A Dutton, Puragra Guhathakurta, David C Koo, AJ Metevier, Kai G Noeske, Joel R Primack

Abstract:

We present evidence from a sample of 544 galaxies from the DEEP2 Survey for evolution of the internal kinematics of blue galaxies with stellar masses ranging 8.0 < log M* (M_Sun) < 10.7 over 0.2
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The Epoch of Disk Settling: z~1 to Now

(2012)

Authors:

Susan A Kassin, Benjamin J Weiner, SM Faber, Jonathan P Gardner, CNA Willmer, Alison L Coil, Michael C Cooper, Julien Devriendt, Aaron A Dutton, Puragra Guhathakurta, David C Koo, AJ Metevier, Kai G Noeske, Joel R Primack
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Galaxy Zoo: Bulgeless Galaxies With Growing Black Holes

ArXiv 1207.419 (2012)

Authors:

BD Simmons, C Lintott, K Schawinski, EC Moran, A Han, S Kaviraj, KL Masters, CM Urry, KW Willett, SP Bamford, RC Nichol

Abstract:

The growth of supermassive black holes appears to be driven by galaxy mergers, violent merger-free processes and/or `secular' processes. In order to quantify the effects of secular evolution on black hole growth, we study a sample of active galactic nuclei (AGN) in galaxies with a calm formation history free of significant mergers, a population that heretofore has been difficult to locate. Here we present an initial sample of 13 AGN in massive (M_* >~ 1e10 M_sun) bulgeless galaxies -- which lack the classical bulges believed inevitably to result from mergers -- selected from the Sloan Digital Sky Survey using visual classifications from Galaxy Zoo. Parametric morphological fitting confirms the host galaxies lack classical bulges; any contributions from pseudobulges are very small (typically < 5%). We compute black hole masses for the two broad-line objects in the sample (4.2e6 and 1.2e7 M_sun) and place lower limits on black hole masses for the remaining sample (typically M_BH >~ 1e6 M_sun), showing that significant black hole growth must be possible in the absence of mergers or violent disk instabilities. The black hole masses are systematically higher than expected from established bulge-black hole relations. However, if the mean Eddington ratio of the systems with measured black hole masses (L/L_Edd = 0.065) is typical, 10 of 13 sources are consistent with the correlation between black hole mass and total stellar mass. That pure disk galaxies and their central black holes may be consistent with a relation derived from elliptical and bulge-dominated galaxies with very different formation histories implies the details of stellar galaxy evolution and dynamics may not be fundamental to the co-evolution of galaxies and black holes.
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