Jeremiah P. Ostriker

Columbia University, New York, New York, United States

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Publications (395)2003.72 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: We present a hydrodynamical simulation of the turbulent, magnetized, supernova-driven interstellar medium (ISM) in a stratified box that dynamically couples the injection and evolution of cosmic rays (CRs) and a self-consistent evolution of the chemical composition. CRs are treated as a relativistic fluid in the advection-diffusion approximation. The thermodynamic evolution of the gas is computed using a chemical network that follows the abundances of H+, H, H2, CO, C+, and free electrons and includes (self-)shielding of the gas and dust. We find that CRs perceptibly thicken the disk with the heights of 90% (70%) enclosed mass reaching ~1.5 kpc (~0.2 kpc). The simulations indicate that CRs alone can launch and sustain strong outflows of atomic and ionized gas with mass loading factors of order unity, even in solar neighbourhood conditions and with a CR energy injection per supernova (SN) of 10^50 erg, 10% of the fiducial thermal energy of a SN. The CR-driven outflows have moderate launching velocities close to the midplane (~100 km/s) and are denser (\rho~1e-24 - 1e-26 g/cm^3), smoother and colder than the (thermal) SN-driven winds. The simulations support the importance of CRs for setting the vertical structure of the disk as well as the driving of winds.
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    Miao Li · Jeremiah P. Ostriker · Renyue Cen · Greg L. Bryan · Thorsten Naab
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    ABSTRACT: Supernovae are the most energetic among stellar feedback processes, and are crucial for regulating the interstellar medium (ISM) and launching galactic winds. We explore how supernova remnants (SNRs) create a multiphase medium by performing high resolution, 3D hydrodynamical simulations at various SN rates, $S$, and ISM average densities, $n$. We find that the evolution of a SNR in a self-consistently generated three-phase ISM is qualitatively different from that in a uniform or a two-phase warm/cold medium. By traveling faster and further in the cooling-inefficient hot phase, the spatial-temporal domain of a SNR is enlarged by $>10^{2.5}$ in a hot-dominated multiphase medium (HDMM) compared to the uniform case. We then examine the resultant ISM as we vary $n$ and $S$, finding that a steady state can only be achieved when the hot gas volume fraction \fvh $\lesssim 0.6\pm 0.1$. Above that, overlapping SNRs render connecting topology of the hot gas, and such a HDMM is subjected to thermal runaway with growing pressure and \fvh. Photoelectric heating (PEH) has a surprisingly strong impact on \fvh. For $n \gtrsim 3 cm^{-3}$, a reasonable PEH rate is able to suppress the ISM from undergoing thermal runaway. Overall, we determine that the critical SN rate for the onset of thermal runaway is roughly $S_{crit} = 200 (n/1cm^{-3})^k (E_{SN}/10^{51} erg)^{-1} kpc^{-3} Myr^{-1}$, where k=(1.2,2.7) for $n$ < 1 and >1 cm$^{-3}$, respectively. We present a fitting formula of the ISM pressure $P(n, S)$, which can be used as an effective equation of state in cosmological simulations. The observed velocities of OB stars imply that the core collapse SN are almost randomly located on scales $\lesssim$ 150 pc. Despite the 5 orders of magnitude span of $(n,S)$, the average Mach number shows very small variations: $M \approx 0.5\pm 0.2, 1.2\pm 0.3, 2.3\pm 0.9$ for the hot, warm and cold phases, respectively.
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    Andrea Kulier · Jeremiah P. Ostriker
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    ABSTRACT: Halo Abundance Matching has been used to construct a one-parameter mapping between galaxies and dark matter haloes by assuming that halo mass and galaxy luminosity (or stellar mass) are monotonically related. While this approach has been reasonably successful, it is known that galaxies must be described by at least two parameters, as can be seen from the two-parameter Fundamental Plane on which massive early-type galaxies lie. In this paper, we derive a connection between initial dark matter density perturbations in the early universe and present-day virialized dark matter haloes by assuming simple spherical collapse combined with conservation of mass and energy. We find that $z = 0$ halo concentration, or alternatively the inner slope of the halo density profile $\alpha$, is monotonically and positively correlated with the collapse redshift of the halo. This is qualitatively similar to the findings of some previous works based on numerical simulations, with which we compare our results. We then describe how the halo mass and concentration (or inner slope $\alpha$) can be used as two halo parameters in combination with two parameters of early-type galaxies to create an improved abundance matching scheme.
    Monthly Notices of the Royal Astronomical Society 03/2015; 452(4). DOI:10.1093/mnras/stv1564 · 5.11 Impact Factor
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    Nicholas C. Stone · Jeremiah P. Ostriker
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    ABSTRACT: We present a new potential-density pair designed to model nearly isothermal star clusters (and similar self-gravitating systems) with a central core and an outer turnover radius, beyond which density falls off as $r^{-4}$. In the intermediate zone, the profile is similar to that of an isothermal sphere (density $\rho \propto r^{-2}$), somewhat less steep than the King 1962 profile, and with the advantage that many dynamical quantities can be written in a simple closed form. We derive analytic expressions for the cluster binding energy, central velocity dispersion, and escape velocity, and apply these to create toy models for cluster core collapse and evaporation. We rederive classical results for evaporating, collapsing, and quasi-equilibrium (heated) clusters, and fit our projected surface brightness profiles to observed globular and open clusters. We find that the quality of the fit is generally at least as good as that for the surface brightness profiles of King 1962. This model can be used for convenient computation of the dynamics and evolution of globular and nuclear star clusters.
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    ABSTRACT: We use hydrodynamical simulations in a (256 pc)3 periodic box to model the impact of supernova (SN) explosions on the multiphase interstellar medium (ISM) for initial densities n = 0.5–30 cm−3 and SN rates 1–720 Myr−1. We include radiative cooling, diffuse heating, and the formation of molecular gas using a chemical network. The SNe explode either at random positions, at density peaks, or both. We further present a model combining thermal energy for resolved and momentum input for unresolved SNe. Random driving at high SN rates results in hot gas (T ≳ 106 K) filling >90 per cent of the volume. This gas reaches high pressures (104 < P/kB < 107 K cm−3) due to the combination of SN explosions in the hot, low-density medium and confinement in the periodic box. These pressures move the gas from a two-phase equilibrium to the single-phase, cold branch of the cooling curve. The molecular hydrogen dominates the mass (>50 per cent), residing in small, dense clumps. Such a model might resemble the dense ISM in high-redshift galaxies. Peak driving results in huge radiative losses, producing a filamentary ISM with virtually no hot gas, and a small molecular hydrogen mass fraction (≪1 per cent). Varying the ratio of peak to random SNe yields ISM properties in between the two extremes, with a sharp transition for equal contributions. The velocity dispersion in H i remains ≲10 km s−1 in all cases. For peak driving, the velocity dispersion in Hα can be as high as 70 km s−1 due to the contribution from young, embedded SN remnants.
    Monthly Notices of the Royal Astronomical Society 10/2014; 449(1). DOI:10.1093/mnras/stv324 · 5.11 Impact Factor
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    Christine M. Simpson · Greg L. Bryan · Cameron Hummels · Jeremiah P. Ostriker
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    ABSTRACT: We describe a new method for adding a prescribed amount of kinetic energy to simulated gas modeled on a cartesian grid by directly altering grid cells' mass and velocity in a distributed fashion. The method is explored in the context of supernova feedback in high-resolution hydrodynamic simulations of galaxy formation. In idealized tests at varying background densities and resolutions, we show convergence in behavior between models with different initial kinetic energy fractions at low densities and/or at high resolutions. We find that in high density media ($\gtrsim$ 50 cm$^{-3}$) with coarse resolution ($\gtrsim 4$ pc per cell), results are sensitive to the initial fraction of kinetic energy due to the early rapid cooling of thermal energy. We describe and test a resolution dependent scheme for adjusting this fraction that approximately replicates our high-resolution tests. We apply the method to a prompt supernova feedback model, meant to mimic Type II supernovae, in a cosmological simulation of a $10^9$ Msun halo. We find that depositing small amounts of supernova energy in kinetic form (as little as 1%) has a dramatic impact on the evolution of the system, resulting in an order of magnitude suppression of stellar mass. We discuss the distribution of stellar metallicities in the resulting system and find that while the mean metallicity is much more consistent with observations than in previous models, significant discrepancies remain that are likely due to our simplistic assumptions for the source of stellar feedback that neglect contributions from Type Ia supernovae and stellar winds.
    The Astrophysical Journal 10/2014; 809(1). DOI:10.1088/0004-637X/809/1/69 · 5.99 Impact Factor
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    ABSTRACT: We investigate the evolution of stellar population gradients from z = 2 to 0 in massive galaxies at large radii (r > 2Reff) using 10 cosmological zoom simulations of haloes with 6 × 1012 M⊙ < Mhalo < 2 × 1013 M⊙. The simulations follow metal cooling and enrichment from SNII, SNIa and asymptotic giant branch winds. We explore the differential impact of an empirical model for galactic winds that reproduces the mass–metallicity relation and its evolution with redshift. At larger radii the galaxies, for both models, become more dominated by stars accreted from satellite galaxies in major and minor mergers. In the wind model, fewer stars are accreted, but they are significantly more metal-poor resulting in steep global metallicity (〈∇Zstars〉 = −0.35 dex dex−1) and colour (e.g. 〈∇g − r〉 = −0.13 dex dex−1) gradients in agreement with observations. In contrast, colour and metallicity gradients of the models without winds are inconsistent with observations. Age gradients are in general mildly positive at z = 0 (〈∇Agestars〉 = 0.04 dex dex−1) with significant differences between the models at higher redshift. We demonstrate that for the wind model, stellar accretion is steepening existing in situ metallicity gradients by about 0.2 dex by the present day and helps to match observed gradients of massive early-type galaxies at large radii. Colour and metallicity gradients are significantly steeper for systems which have accreted stars in minor mergers, while galaxies with major mergers have relatively flat gradients, confirming previous results. The effect of stellar migration of in situ formed stars to large radii is discussed. This study highlights the importance of stellar accretion for stellar population properties of massive galaxies at large radii, which can provide important constraints for formation models.
    Monthly Notices of the Royal Astronomical Society 10/2014; 449(1). DOI:10.1093/mnras/stv274 · 5.11 Impact Factor
  • Blue Waters Symposium 2014, Champaign, IL; 07/2014
  • Brandon S. Hensley · Jeremiah P. Ostriker · Luca Ciotti
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    ABSTRACT: We study the effects of a detailed dust treatment on the properties and evolution of early-type galaxies containing central black holes, as determined by active galactic nucleus (AGN) feedback. We find that during cooling flow episodes, radiation pressure on the dust in and interior to infalling shells of cold gas can greatly impact the amount of gas able to be accreted and therefore the frequency of AGN bursts. However, the overall hydrodynamic evolution of all models, including mass budget, is relatively robust to the assumptions on dust. We find that IR re-emission from hot dust can dominate the bolometric luminosity of the galaxy during the early stages of an AGN burst, reaching values in excess of 1046 erg s–1. The AGN-emitted UV is largely absorbed, but the optical depth in the IR does not exceed unity, so the radiation momentum input never exceeds L BH/c. We constrain the viability of our models by comparing the AGN duty cycle, broadband luminosities, dust mass, black hole mass, and other model predictions to current observations. These constraints force us towards models wherein the dust to metals ratios are 1% of the Galactic value, and only models with a dynamic dust to gas ratio are able to produce both quiescent galaxies consistent with observations and high obscured fractions during AGN "on" phases. During AGN outbursts, we predict that a large fraction of the FIR luminosity can be attributed to warm dust emission ( 100 K) from dense dusty gas within ≤1 kpc reradiating the AGN UV emission.
    The Astrophysical Journal 06/2014; 789(1):78. DOI:10.1088/0004-637X/789/1/78 · 5.99 Impact Factor
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    Ena Choi · Jeremiah P. Ostriker · Thorsten Naab · Ludwig Oser · Benjamin P. Moster
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    ABSTRACT: We employ cosmological hydrodynamical simulations to investigate the effects of AGN feedback on the formation of massive galaxies with present-day stellar masses of $M_{\rm stel}= 8.8 \times 10^{10}{\rm -}6.0 \times 10^{11} {\thinspace {\rm M}_{{\odot }}}$. Using smoothed particle hydrodynamics simulations with a pressure-entropy formulation that allows an improved treatment of contact discontinuities and fluid mixing, we run three sets of simulations of 20 haloes with different AGN feedback models: (1) no feedback, (2) thermal feedback, and (3) mechanical and radiation feedback. We assume that seed black holes are present at early cosmic epochs at the centre of emerging dark matter haloes and trace their mass growth via gas accretion and mergers with other black holes. Both feedback models successfully recover the observed MBH–σ relation and black hole-to-stellar mass ratio for simulated central early-type galaxies. The baryonic conversion efficiencies are reduced by a factor of 2 compared to models without any AGN feedback at all halo masses. However, massive galaxies simulated with thermal AGN feedback show a factor of ∼10–100 higher X-ray luminosities than observed. The mechanical/radiation feedback model reproduces the observed correlation between X-ray luminosities and velocity dispersion, e.g. for galaxies with σ = 200 km s− 1, the X-ray luminosity is reduced from 1042 erg s− 1 to 1040 erg s− 1. It also efficiently suppresses late-time star formation, reducing the specific star formation rate from 10−10.5 yr− 1 to 10−14 yr− 1 on average and resulting in quiescent galaxies since z = 2, whereas the thermal feedback model shows higher late-time in situ star formation rates than observed.
    Monthly Notices of the Royal Astronomical Society 03/2014; 449(4). DOI:10.1093/mnras/stv575 · 5.11 Impact Factor
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    Zhaoming Gan · Feng Yuan · Jeremiah P. Ostriker · Luca Ciotti · Gregory S. Novak
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    ABSTRACT: Based on two-dimensional high resolution hydrodynamic numerical simulation, we study the mechanical and radiative feedback effects from the central AGN on the cosmological evolution of an isolated elliptical galaxy. Physical processes such as star formation and supernovae are considered. The inner boundary of the simulation domain is carefully chosen so that the fiducial Bondi radius is resolved and the accretion rate of the black hole is determined self-consistently. In analogy to previous works, we assume that the specific angular momentum of the galaxy is low. It is well-known that when the accretion rates are high and low, the central AGNs will be in cold and hot accretion modes, which correspond to the radiative and kinetic feedback modes, respectively. The emitted spectrum from the hot accretion flows is harder than that from the cold accretion flows, which results in a higher Compton temperature accompanied by a more efficient radiative heating. Such a difference of the Compton temperature between the two feedback modes, the focus of this study, has been neglected in previous works. Significant differences in the kinetic feedback mode are found as a result of the stronger Compton heating and accretion becomes more chaotic. More importantly, if we constrain models to correctly predict black hole growth and AGN duty cycle after cosmological evolution, we find that the favored model parameters are constrained: mechanical feedback efficiency diminishes with decreasing luminosity (the maximum efficiency being $\simeq 10^{-3.5}$) and X-ray Compton temperature increases with decreasing luminosity, although models with fixed mechanical efficiency and Compton temperature can be found that are satisfactory as well. We conclude that radiative feedback in the kinetic mode is much more important than previously thought.
    The Astrophysical Journal 03/2014; 789(2). DOI:10.1088/0004-637X/789/2/150 · 5.99 Impact Factor
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    Brandon S. Hensley · Jeremiah P. Ostriker · Luca Ciotti
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    ABSTRACT: We study the effects of a detailed treatment of dust physics on the properties and evolution of early-type galaxies containing central black holes, as determined by AGN feedback. We find that during cooling flow episodes, radiation pressure on the dust in and interior to infalling shells of cold gas can greatly impact the amount of gas able to be accreted and therefore the frequency of AGN bursts. However, the overall hydrodynamic evolution of all models, including mass budget, is relatively robust to the assumptions on dust. Our most detailed models find that the dust to metals ratio is reduced by factors of $10^{-1}-10^{-2}$ relative to Milky Way abundances, and in quiescent phases the dust content of the galaxy would result in ~0.03 magnitudes of extinction to the center of the galaxy. We find that IR re-emission from hot dust can dominate the bolometric luminosity of the galaxy during the early stages of an AGN burst, reaching values in excess of $10^{46}$ erg/s. The AGN-emitted UV is largely absorbed, but the optical depth in the IR does not exceed unity, so the radiation momentum input never exceeds $L_{\rm BH}/c$. We constrain the viability of our models by comparing the energy output in each band, AGN duty cycle, FIR emission, dust mass and opacity, black hole mass, and other model predictions to current observations. These constraints force us to models wherein the destruction of dust in hot gas by sputtering and the competing growth of dust in cold gas results in depletion at the $\simeq10^{-2}$ level, and only models with a dynamic dust to gas ratio are able to produce both quiescent galaxies consistent with observations and high obscured fractions during AGN "on" phases. During AGN outbursts, we predict that a large fraction of the FIR luminosity can be attributed to warm dust emission ($\simeq100$ K) from dense dusty gas within $\leq$1 kpc reradiating the AGN UV emission.
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    Adam S Burrows · Jeremiah P Ostriker
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    ABSTRACT: Using basic physical arguments, we derive by dimensional and physical analysis the characteristic masses and sizes of important objects in the universe in terms of just a few fundamental constants. This exercise illustrates the unifying power of physics and the profound connections between the small and the large in the cosmos we inhabit. We focus on the minimum and maximum masses of normal stars, the corresponding quantities for neutron stars, the maximum mass of a rocky planet, the maximum mass of a white dwarf, and the mass of a typical galaxy. To zeroth order, we show that all these masses can be expressed in terms of either the Planck mass or the Chandrasekar mass, in combination with various dimensionless quantities. With these examples, we expose the deep interrelationships imposed by nature between disparate realms of the universe and the amazing consequences of the unifying character of physical law.
    Proceedings of the National Academy of Sciences 01/2014; 111(7). DOI:10.1073/pnas.1318003111 · 9.67 Impact Factor
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    ABSTRACT: We investigate the differential effects of metal cooling and galactic stellar winds on the cosmological formation of individual galaxies with three sets of cosmological, hydrodynamical zoom simulations of 45 halos in the mass range 10^11<M_halo<10^13M_sun. Models including both galactic winds and metal cooling (i) suppress early star formation at z>1 and predict reasonable star formation histories, (ii) produce galaxies with high cold gas fractions (30-60 per cent) at high redshift, (iii) significantly reduce the galaxy formation efficiencies for halos (M_halo<10^12M_sun) at all redshifts in agreement with observational and abundance matching constraints, (iv) result in high-redshift galaxies with reduced circular velocities matching the observed Tully-Fisher relation at z~2, and (v) significantly increase the sizes of low-mass galaxies (M_stellar<3x10^10M_sun) at high redshift resulting in a weak size evolution - a trend in agreement with observations. However, the low redshift (z<0.5) star formation rates of massive galaxies are higher than observed (up to ten times). No tested model predicts the observed size evolution for low-mass and high-mass galaxies simultaneously. Due to the delayed onset of star formation in the wind models, the metal enrichment of gas and stars is delayed and agrees well with observational constraints. Metal cooling and stellar winds are both found to increase the ratio of in situ formed to accreted stars - the relative importance of dissipative vs. dissipationless assembly. For halo masses below ~10^12M_sun, this is mainly caused by less stellar accretion and compares well to predictions from semi-analytical models but still differs from abundance matching models. For higher masses, the fraction of in situ stars is over-predicted due to the unrealistically high star formation rates at low redshifts.
    Monthly Notices of the Royal Astronomical Society 09/2013; 436(4). DOI:10.1093/mnras/stt1770 · 5.11 Impact Factor
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    Ena Choi · Thorsten Naab · Jeremiah P. Ostriker · Peter H. Johansson · Benjamin P. Moster
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    ABSTRACT: We employ hydrodynamical simulations to study the effect of AGN mechanical and radiation feedback on the formation of bulge dominated galaxies via mergers of disk galaxies. The merging galaxies have mass-ratios of 1:1 to 6:1 and include pre-existing hot gaseous halos to properly account for the global impact of AGN feedback. We compare three models: (1) no black hole and no AGN feedback; (2) thermal AGN feedback; and (3) mechanical and radiative AGN feedback. The last model is motivated by observations of broad absorption line quasars which show winds with initial velocities of v_w ~ 10,000 km/s and also heating associated with the central AGN X-ray radiation. The primary changes in gas properties due to mechanical AGN feedback are lower thermal X-ray luminosity from the final galaxy - in better agreement with observations - and galactic outflows with higher velocity ~ 1000 km/s similar to recent direct observations of nearby merger remnants. The kinetic energy of the outflowing gas is a factor of ~ 20 higher than in the thermal feedback case. All merger remnants with momentum-based AGN feedback, independent of their progenitor mass-ratios, follow the observed relations between stellar velocity dispersion and black hole mass (M_BH-\sigma) as well as X-ray luminosity (L_X-\sigma) with 10^37.5 < L_X (0.3-8 keV) < 10^39.2 for velocity dispersions in the range of 120 km/s < \sigma < 190 km/s. In addition, the mechanical feedback produces a much greater AGN variability. We also show that gas is more rapidly and impulsively stripped from the galactic centres driving a moderate increase in galaxy size and decrease in central density with the mechanical AGN feedback model. However, the black hole mass growth required to produce the observed galaxy size and central density evolution is inconsistent with the observed M_BH-{\sigma} relation.
    Monthly Notices of the Royal Astronomical Society 08/2013; 442(1). DOI:10.1093/mnras/stu874 · 5.11 Impact Factor
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    Oleg Y. Gnedin · Jeremiah P. Ostriker · Scott Tremaine
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    ABSTRACT: We revisit the hypothesis that dense galactic nuclei are formed from inspiraling globular clusters. Recent advances in understanding of the continuous formation of globular clusters over cosmic time and the concurrent evolution of the galaxy stellar distribution allow us to construct a simple model that matches the observed spatial and mass distributions of clusters in the Galaxy and the giant elliptical galaxy M87. In order to compare with observations, we model the effects of dynamical friction and dynamical evolution, including stellar mass loss, tidal stripping of stars, and tidal disruption of clusters by the growing galactic nucleus. We find that inspiraling globular clusters form a dense central stellar cluster with an effective radius of several pc, with mass and radius comparable to the typical values in observed nuclear star clusters in late-type and low-mass early-type galaxies. The density contrast associated with the nuclear star cluster is less pronounced in giant elliptical galaxies. Thus disrupted globular clusters may contribute most of the mass of nuclear star clusters (NSCs) in galaxies with stellar mass below 10^{11} Msun. Our results indicate that the NSC mass as a fraction of mass of the galaxy stellar spheroid scales as M_{NSC}/M_{sph} ~ 0.0025 M_{sph,11}^{-0.5}. However, some fraction of the accumulated stellar debris may seed the growth of a central black hole via stellar dynamical core collapse, thereby relieving the problem of how to form luminous quasars at high redshift. Both the formation time of NSC and the core collapse time are less than 1 Gyr for galaxies more massive than the Milky Way.
    The Astrophysical Journal 07/2013; 785(1). DOI:10.1088/0004-637X/785/1/71 · 5.99 Impact Factor
  • Ludwig Oser · Manisha Gajbe · Kentaro Nagamine · Greg Bryan · Jeremiah P. Ostriker · Renyue Cen
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    ABSTRACT: We (the CAGE team) present a possible solution to the scaling problem that is inherent to cosmological simulations of structure formation. With an increasing number of computational nodes the resources that are lost due to communication overhead and load balancing is growing and thereby limiting the problem sizes and/or resolution level that can be computed in a reasonable amount of time. To alleviate this problem, we propose the HECA (Hierarchical Ensemble Computing Algorithm). Instead of running a full-box cosmological simulation, we perform multiple (only limited by the number of processing nodes) zoom-in simulations concurrently that are independent of each other and thereby providing a perfect scaling to large core counts. In these simulations we can reach a much higher resolution level that would be unfeasible to achieve in a full-box simulation. We show that with the help of HECA we are able to efficiently use the ressources provided by modern petascale supercomputers to simulate a statistically significant sample of galaxies.
    Proceedings of the Conference on Extreme Science and Engineering Discovery Environment: Gateway to Discovery; 07/2013
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    ABSTRACT: Accretion and merger triggered accretion episodes are thought to primarily contribute to the mass accumulation history of supermassive black holes throughout cosmic time. While this might be the dominant growth mode at high redshifts, at lower redshifts and for the most massive black holes, mergers themselves might add significantly to the mass budget. In this paper, we use merger trees derived from hydrodynamical cosmological simulations of a cluster and void region to examine the growth of SMBHs from 4 > z > 0. Mass gains from gas accretion and BH-BH mergers are tracked as are black holes that remain unmerged and "orbiting" due to insufficient dynamical friction in a merger remnant, as well as those that are ejected due to gravitational recoil. We find that gas accretion remains the dominant source of mass accumulation in almost all of the SMBHs produced; mergers contribute an average of 3.3 +/- 0.2% for all SMBHs in the cluster, and 1.3 +/- 0.2% in the void from z = 4 to 0. However, mergers are significant for massive SMBHs, with the contribution from mergers reaching a maximum of 20% in the cluster for black holes with mass around 10^9 M_sun. We also find that the total mass in orbiting SMBHs is generally negligible in the void, but significant in the cluster, with a median value of M_orbiting >~ 10^7 M_sun per galaxy for galaxies with stellar mass M_{*} > 10^11.5 M_sun. We find that 40% of SMBHs and approximately 14% of the total SMBH mass is found orbiting in the cluster region at z = 0. We estimate the correction to the Soltan argument due to such orbiting SMBHs as well as SMBHs ejected via gravitational slingshot effects to be in the range 1.6 - 15%, with a mean value of 7.4 +/- 3.7% in the estimate of the inventory of the integrated accreted mass density of SMBHs. We also calculate the total energy output and strain due to gravitational waves emitted by merging SMBHs.
    The Astrophysical Journal 07/2013; 799(2). DOI:10.1088/0004-637X/799/2/178 · 5.99 Impact Factor
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    Chao Liu · Feng Yuan · Jeremiah P. Ostriker · Zhaoming Gan · Xiaohong Yang
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    ABSTRACT: We perform time-dependent, 2DHD numerical simulations to study the dynamics of a slowly rotating accretion flow from sub-pc to pc scales under the irradiation from the central AGN. Compared to previous work, we improve the calculation of the radiative force due to X-rays. More importantly, in addition to radiative pressure and radiative heating/cooling directly from the central AGN, in the momentum equation we also include the force due to the scattered and reprocessed photons. We find that the accretion flow properties change significantly due to this "re-radiation" effect. The inflow rate at the inner boundary is reduced, while the outflow rate at the outer boundary is enhanced by about one order of magnitude. This effect is more significant when the density at the outer boundary is higher. The properties of outflows such as velocity, momentum and energy fluxes, and the ratio of outflow rate and the accretion rate, are calculated. We find that the efficiency of transferring the radiation power into the kinetic power of outflow is typically $10^{-3}$, far below the value of $\sim 0.05$ which is assumed in some cosmological simulations. The effect of the temperature of the gas at the outer boundary ($T_0$) is investigated. When $T_0$ is high, the emitted luminosity of the accretion flow oscillates. This is because in this case the gas around the Bondi radius can be more easily heated to be above the virial temperature due to its high internal energy. Another question we hope to address is the so-called "sub-Eddington" puzzle. Observationally, the luminosity of almost all AGNs are sub-Eddington, while theoretically the luminosity of an accretion flow can easily be super-Eddington. We find that even when the re-radiation effect is included and outflow does become much stronger, the luminosity, while reduced, can still be super-Eddington.
    Monthly Notices of the Royal Astronomical Society 04/2013; 434(2). DOI:10.1093/mnras/stt1139 · 5.11 Impact Factor
  • G. S. Novak · J. P. Ostriker · L. Ciotti
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    ABSTRACT: To facilitate the study of black hole fuelling, star formation and feedback in galaxies, we outline a method for treating the radial forces on interstellar gas due to absorption of photons by dust grains. The method gives the correct behaviour in all of the relevant limits [dominated by the central point source; dominated by the distributed isotropic source; optically thin; optically thick to ultraviolet (UV)/optical; optically thick to infrared (IR)] and reasonably interpolates between the limits when necessary. The method is explicitly energy conserving so that UV/optical photons that are absorbed are not lost, but are rather redistributed to the IR where they may scatter out of the galaxy. We implement the radiative transfer algorithm in a two-dimensional hydrodynamical code designed to study feedback processes in the context of early-type galaxies. We find that the dynamics and final state of simulations are measurably but only moderately affected by radiative forces on dust, even when assumptions about the dust-to-gas ratio are varied from zero to a value appropriate for the Milky Way. In simulations with high gas densities designed to mimic ultraluminous IR galaxies with a star formation rate of several hundred solar masses per year, dust makes a more substantial contribution to the dynamics and outcome of the simulation. We find that, despite the large opacity of dust to UV radiation, the momentum input to the flow from radiation very rarely exceeds L/c due to two factors: the low opacity of dust to the re-radiated IR and the tendency for dust to be destroyed by sputtering in hot gas environments. We also develop a simplification of our radiative transfer algorithm that respects the essential physics but is much easier to implement and requires a fraction of the computational cost.
    Monthly Notices of the Royal Astronomical Society 12/2012; 427(4):2734-2756. DOI:10.1111/j.1365-2966.2012.21844.x · 5.11 Impact Factor

Publication Stats

31k Citations
2,003.72 Total Impact Points


  • 2013–2015
    • Columbia University
      • Columbia Astrophysics Laboratory
      New York, New York, United States
  • 1969–2014
    • Princeton University
      • Department of Astrophysical Sciences
      Princeton, New Jersey, United States
  • 1975–2012
    • University of Cambridge
      • Institute of Astronomy
      Cambridge, England, United Kingdom
  • 2009
    • Pontifical Catholic University of Chile
      • Departamento de Anatomía
      CiudadSantiago, Santiago Metropolitan, Chile
    • CA Technologies
      New York, New York, United States
  • 2007
    • Los Alamos National Laboratory
      • Theoretical Division
      Los Alamos, California, United States
  • 2002–2005
    • Cancer Research UK Cambridge Institute
      Cambridge, England, United Kingdom
  • 2004
    • University of Pennsylvania
      • Department of Physics and Astronomy
      Filadelfia, Pennsylvania, United States
  • 1993–2001
    • TRI/Princeton
      Princeton, New Jersey, United States
    • Hebrew University of Jerusalem
      Yerushalayim, Jerusalem, Israel
  • 1997–2000
    • The Astronomical Observatory of Brera
      Merate, Lombardy, Italy
  • 1998
    • The University of Tokyo
      • Department of Physics
      Tōkyō, Japan
  • 1996
    • University of Washington Seattle
      • Department of Astronomy
      Seattle, Washington, United States
  • 1995
    • Pusan National University
      Tsau-liang-hai, Busan, South Korea
  • 1991
    • University of Texas at Austin
      Austin, Texas, United States
  • 1990
    • Ibaraki University
      • Department of Physics
      Mito-shi, Ibaraki, Japan
  • 1983
    • Hokkaido University
      • Division of Physics
      Sapporo, Hokkaidō, Japan
  • 1982
    • Massachusetts Institute of Technology
      Cambridge, Massachusetts, United States
  • 1978
    • University of California, Berkeley
      • Department of Astronomy
      Berkeley, California, United States
  • 1976
    • Pasadena City College
      Pasadena, Texas, United States