We reason that, without physical fine-tuning, neither the supermassive black holes (SMBHs) nor the stellar bulges can self-regulate or inter-regulate by driving away already fallen cold gas to produce the observed correlation between them. We suggest
an alternative scenario where the observed mass ratios of the SMBHs to bulges reflect the angular momentum distribution of infallen gas such that the mass reaching the stable accretion disc is a small fraction of that reaching the bulge region, averaged over the cosmological time scales. We test this scenario using high resolution, large-scale cosmological hydrodynamic simulations (without AGN feedback), assuming the angular momentum distribution of gas landing in the bulge region to yield a Mestel disc that is supported by independent simulations resolving the Bondi radii of SMBHs. A mass ratio of $0.1-0.3%$ between the very low angular momentum gas that free-falls to the sub-parsec region to accrete to the SMBH and the overall star formation rate is found. This ratio is found to increase with increasing redshift to within a factor of $sim 2$, suggesting that the SMBH to bulge ratio is nearly redshift independent, with a modest increase with redshift, a testable prediction. Furthermore, the duty cycle of active galactic nuclei (AGN) with high Eddington ratios is expected to increase significantly with redshift. Finally, while SMBHs and bulges are found to coevolve on $sim 30-150$Myr time scales or longer, there is indication that, on shorer time scales, the SMBH accretion rate and star formation may be less correlated.
Simulations have indicated that most of the escaped Lyman continuum photons escape through a minority of solid angles with near complete transparency, with the remaining majority of the solid angles largely opaque, resulting in a very broad and skewe
d probability distribution function (PDF) of the escape fraction when viewed at different angles. Thus, the escape fraction of Lyman continuum photons of a galaxy observed along a line of sight merely represents the properties of the interstellar medium along that line of sight, which may be an ill-representation of true escape fraction of the galaxy averaged over its full sky. Here we study how Lyman continuum photons escape from galaxies at $z=4-6$, utilizing high-resolution large-scale cosmological radiation-hydrodynamic simulations. We compute the PDF of the mean escape fraction ($left<f_{rm esc,1D}right>$) averaged over mock observational samples, as a function of the sample size, compared to the true mean (had you an infinite sample size). We find that, when the sample size is small, the apparent mean skews to the low end. For example, for a true mean of 6.7%, an observational sample of (2,10,50) galaxies at $z=4$ would have have 2.5% probability of obtaining the sample mean lower than $left<f_{rm esc,1D}right>=$(0.007%, 1.8%, 4.1%) and 2.5% probability of obtaining the sample mean being greater than (43%, 18%, 11%). Our simulations suggest that at least $sim$ 100 galaxies should be stacked in order to constrain the true escape fraction within 20% uncertainty.
Recent large surveys have found a reversal of the star formation rate (SFR)-density relation at z=1 from that at z=0 (e.g. Elbaz et al.; Cooper et al.), while the sign of the slope of the color-density relation remains unchanged (e.g. Cucciati et al.
; Quadri et al.). We use state-of-the-art adaptive mesh refinement cosmological hydrodynamic simulations of a 21x24x20 (Mpc/h)$^3$ region centered on a cluster to examine the SFR-density and color-density relations of galaxies at z=0 and z=1. The local environmental density is defined by the dark matter mass in spheres of radius 1 Mpc/h, and we probe two decades of environmental densities. Our simulations produce a large increase of SFR with density at z=1, as in the observations of Elbaz et al. We also find a significant evolution to z=0, where the SFR-density relation is much flatter. The color-density relation in our simulations is consistent from z=1 to z=0, in agreement with observations. We find that the increase in the median SFR with local density at z=1 is due to a growing population of star-forming galaxies in higher-density environments. At z=0 and z=1 both the SFR and cold gas mass are tightly correlated with the galaxy halo mass, and therefore the correlation between median halo mass and local density is an important cause of the SFR-density relation at both redshifts. We also show that the local density on 1 Mpc/h scales affects galaxy SFRs as much as halo mass at z=0. Finally, we find indications that the role of the 1 Mpc/h scale environment reverses from z=0 to z=1: at z=0 high-density environments depress galaxy SFRs, while at z=1 high-density environments tend to increase SFRs.
Aims: We offer a new, simpler picture of the local interstellar medium, made of a single continuous cloud enveloping the Sun. This new outlook enables the description of a diffuse cloud from within and brings to light some unexpected properties. Meth
ods: We re-examine the kinematics and abundances of the local interstellar gas, as revealed by the published results for the ultraviolet absorption lines of MgII, FeII, and HI. Results: In contrast to previous representations, our new picture of the local interstellar medium consists of a single, monolithic cloud that surrounds the Sun in all directions and accounts for most of the matter present in the first 50 parsecs around the Sun. The cloud fills the space around us out to about 9 pc in most directions, although its boundary is very irregular with possibly a few extensions up to 20 pc. The cloud does not behave like a rigid body: gas within the cloud is being differentially decelerated in the direction of motion, and the cloud is expanding in directions perpendicular to this flow, much like a squashed balloon. Average HI volume densities inside the cloud vary between 0.03 and 0.1 cm-3 over different directions. Metals appear to be significantly depleted onto grains, and there is a steady increase in depletion from the rear of the cloud to the apex of motion. There is no evidence that changes in the ionizing radiation influence the apparent abundances. Secondary absorption components are detected in 60% of the sight lines. Almost all of them appear to be interior to the volume occupied by the main cloud. Half of the sight lines exhibit a secondary component moving at about -7.2 km/s with respect to the main component, which may be the signature of a shock propagating toward the clouds interior.
We perform first-principles relativistic particle-in-cell simulations of aligned pulsar magnetosphere. We allow free escape of particles from the surface of a neutron star and continuously populate the magnetosphere with neutral pair plasma to imitat
e pair production. As pair plasma supply increases, we observe the transition from a charge-separated electrosphere solution with trapped plasma and no spin-down to a solution close to the ideal force-free magnetosphere with electromagnetically-dominated pulsar wind. We calculate the magnetospheric structure, current distribution and spin-down power of the neutron star. We also discuss particle acceleration in the equatorial current sheet.
We derive a suite of generalized Boltzmann equations, based on the density-matrix formalism, that incorporates the physics of neutrino oscillations for two- and three-flavor oscillations, matter refraction, and self-refraction. The resulting equation
s are straightforward extensions of the classical transport equations that nevertheless contain the full physics of quantum oscillation phenomena. In this way, our broadened formalism provides a bridge between the familiar neutrino transport algorithms employed by supernova modelers and the more quantum-heavy approaches frequently employed to illuminate the various neutrino oscillation effects. We also provide the corresponding angular-mome
DDSCAT 7.3 is an open-source Fortran-90 software package applying the discrete dipole approximation to calculate scattering and absorption of electromagnetic waves by targets with arbitrary geometries and complex refractive index. The targets may be
isolated entities (e.g., dust particles), but may also be 1-d or 2-d periodic arrays of target unit cells, allowing calculation of absorption, scattering, and electric fields around arrays of nanostructures. The theory of the DDA and its implementation in DDSCAT is presented in Draine (1988) and Draine & Flatau (1994), and its extension to periodic structures in Draine & Flatau (2008), and efficient near-field calculations in Flatau & Draine (2012). DDSCAT 7.3 includes support for MPI, OpenMP, and the Intel Math Kernel Library (MKL). DDSCAT supports calculations for a variety of target geometries. Target materials may be both inhomogeneous and anisotropic. It is straightforward for the user to import arbitrary target geometries into the code. DDSCAT automatically calculates total cross sections for absorption and scattering and selected elements of the Mueller scattering intensity matrix for user-specified scattering directions. DDSCAT 7.3 can efficiently calculate E and B throughout a user-specified volume containing the target. This User Guide explains how to use DDSCAT 7.3 to carry out electromagnetic scattering calculations, including use of DDPOSTPROCESS, a Fortran-90 code to perform calculations with E and B at user-selected locations near the target. A number of changes have been made since the last release, DDSCAT 7.2 .
Halo gas in low-z (z<0.5) >0.1L* galaxies in high-resolution, large-scale cosmological hydrodynamic simulations is examined with respect to three components: (cold, warm, hot) with temperatures equal to (<10^5, 10^{5-6}, >10^6)K, respectively. The wa
rm component is compared, utilizing O VI lambdalambda 1032, 1038 absorption lines, to observations and agreement is found with respect to the galaxy-O VI line correlation, the ratio of O VI line incidence rate in blue to red galaxies and the amount of O VI mass in star-forming galaxies. A detailed account of the sources of warm halo gas (stellar feedback heating, gravitational shock heating and accretion from the intergalactic medium), inflowing and outflowing warm halo gas metallicity disparities and their dependencies on galaxy types and environment is also presented. Having the warm component securely anchored, our simulations make the following additional predictions. First, cold gas is the primary component in inner regions, with its mass comprising 50% of all gas within galacto-centric radius r=(30,150)kpc in (red, blue) galaxies. Second, at r>(30,200)kpc in (red, blue) galaxies the hot component becomes the majority. Third, the warm component is a perpetual minority, with its contribution peaking at ~30% at r=100-300kpc in blue galaxies and never exceeding 5% in red galaxies. The significant amount of cold gas in low-z early-type galaxies found in simulations, in agreement with recent observations (Thom et al.), is intriguing, so is the dominance of hot gas at large radii in blue galaxies.
There have been many proposed explanations for the larger-than-expected radii of some transiting hot Jupiters, including either stellar or orbital energy deposition deep in the atmosphere or deep in the interior. In this paper, we explore the importa
nt influences on hot-Jupiter radius evolution of (i) additional heat sources in the high atmosphere, the deep atmosphere, and deep in the convective interior; (ii) consistent cooling of the deep interior through the planetary dayside, nightside, and poles; (iii) the degree of heat redistribution to the nightside; and (iv) the presence of an upper atmosphere absorber inferred to produce anomalously hot upper atmospheres and
Gas-giant planets that form via core accretion might have very different characteristics from those that form via disk-instability. Disk-instability objects are typically thought to have higher entropies, larger radii, and (generally) higher effectiv
e temperatures than core-accretion objects. We provide a large set of models exploring the observational consequences of high-entropy (hot) and low-entropy (cold) initial conditions, in the hope that this will ultimately help to distinguish between different physical mechanisms of planet formation. However, the exact entropies and radii of newly-formed planets due to these two modes of formation cannot, at present, be precisely predicted. We introduce a broad range of Warm Start gas-giant planet models. Between the hottest and the coldest models that we consider, differences in radii, temperatures, luminosities, and spectra persist for only a few million to a few tens of millions of years for planets that are a few times Jupiters mass or less. For planets that are ~five times Jupiters mass or more, significant differences between hottest-start and coldest-start models persist for on the order of 100 Myrs. We find that out of the standard infrared bands (J, H, K, L, M, N) the K and H bands are the most diagnostic of the initial conditions. A hottest-start model can be from ~4.5 magnitudes brighter (at Jupiters mass) to ~9 magnitudes brighter (at ten times Jupiters mass) than a coldest-start model in the first few million years. In more massive objects, these large differences in luminosity and spectrum persist for much longer than in less massive objects. We consider the influence of atmospheric conditions on spectra, and find that the presence or absence of clouds, and the metallicity of an atmosphere, can affect an objects apparent brightness in different bands by up to several magnitudes.
