The Romulus cosmological simulations: a physical approach to the formation, dynamics and accretion models of SMBHs

(shortened) In this contribution an average or Galactic-field IMF is defined, stressing that there is evidence for a change in the power-law index at only two masses: near 0.5 Msun and 0.08 Msun. Using this supposed universal IMF, the uncertainty inherent to any observational estimate of the IMF is investigated, by studying the scatter introduced by Poisson noise and the dynamical evolution of star clusters. It is found that this apparent scatter reproduces quite well the observed scatter in power-law index determinations, thus defining the fundamental limit within which any true variation becomes undetectable. Determinations of the power-law indices alpha are subject to systematic errors arising mostly from unresolved binaries. The systematic bias is quantified here, with the result that the single-star IMFs for young star-clusters are systematically steeper by d_alpha=0.5 between 0.1 and 1 Msun than the Galactic-field IMF, which is populated by, on average, about 5 Gyr old stars. The MFs in globular clusters appear to be, on average, systematically flatter than the Galactic-field IMF, and the recent detection of ancient white-dwarf candidates in the Galactic halo and absence of associated low-mass stars suggests a radically different IMF for this ancient population. Star-formation in higher-metallicity environments thus appears to produce relatively more low-mass stars.

(Abridged) We present far-infrared (FIR) photometry at 150 micron and 205 micron of eight low-redshift starburst galaxies obtained with the ISO Photometer. Five of the eight galaxies are detected in both wavebands and these data are used, in conjunction with IRAS archival photometry, to model the dust emission at lambda>40 micron. The FIR spectral energy distributions (SEDs) are best fitted by a combination of two modified Planck functions, with T~40-55 K (warm dust) and T~20-23 K (cool dust), and with a dust emissivity index epsilon=2. The cool dust can be a major contributor to the FIR emission of starburst galaxies, representing up to 60% of the total flux. This component is heated not only by the general interstellar radiation field, but also by the starburst itself. The cool dust mass is up to ~150 times larger than the warm dust mass, bringing the gas-to-dust ratios of the starbursts in our sample close to Milky Way values, once rescaled for the appropriate metallicity. The ratio between the total dust FIR emission in the range 1-1000 micron and the IRAS FIR emission in the range 40-120 micron is ~1.75, with small variations from galaxy to galaxy. The FIR emission predicted by the dust reddening of the UV-to-nearIR stellar emission is within a factor ~2 of the observed value in individual galaxies and within 20% when averaged over a large sample. If our sample of local starbursts is representative of high-redshift (z>1), UV-bright, star-forming galaxies, these galaxies' FIR emission will be generally undetected in sub-mm surveys, unless (1) their bolometric luminosity is comparable to or larger than that of ultraluminous FIR galaxies and (2) their FIR SED contains a cool dust component.

We review the observed demographics and inferred evolution of supermassive black holes (BHs) found by dynamical modeling of spatially resolved kinematics. Most influential was the discovery of a tight correlation between BH mass and the velocity dispersion of the host-galaxy bulge. It and other correlations led to the belief that BHs and bulges coevolve by regulating each other's growth. New results are now replacing this simple story with a richer and more plausible picture in which BHs correlate differently with different galaxy components. BHs are found in pure-disk galaxies, so classical (elliptical-galaxy-like) bulges are not necessary to grow BHs. But BHs do not correlate with galaxy disks. And any correlations with disk-grown pseudobulges or halo dark matter are so weak as to imply no close coevolution. We suggest that there are four regimes of BH feedback. 1- Local, stochastic feeding of small BHs in mainly bulgeless galaxies involves too little energy to result in coevolution. 2- Global feeding in major, wet galaxy mergers grows giant BHs in short, quasar-like "AGN" events whose feedback does affect galaxies. This makes classical bulges and coreless-rotating ellipticals. 3- At the highest BH masses, maintenance-mode feedback into X-ray gas has the negative effect of helping to keep baryons locked up in hot gas. This happens in giant, core-nonrotating ellipticals. They inherit coevolution magic from smaller progenitors. 4- Independent of any feedback physics, the averaging that results from successive mergers helps to engineer tight BH correlations.