Recursos de colección
Caltech Authors (155.447 recursos)
Repository of works by Caltech published authors.
Group = TAPIR
Repository of works by Caltech published authors.
Group = TAPIR
Balogh, Michael L.; Rettura, Alessandro; Wetzel, Andrew
We describe a new Large Program in progress on the Gemini North and South telescopes: Gemini Observations of Galaxies in Rich Early Environments (GOGREEN). This is an imaging and deep spectroscopic survey of 21 galaxy systems at 1 < z < 1.5, selected to span a factor >10 in halo mass. The scientific objectives include measuring the role of environment in the evolution of low-mass galaxies, and measuring the dynamics and stellar contents of their host haloes. The targets are selected from the SpARCS, SPT, COSMOS, and SXDS surveys, to be the evolutionary counterparts of today's clusters and groups. The...
Chen, Baoyi; Stein, Leo C.
Linear perturbation theory is a powerful toolkit for studying black hole spacetimes. However, the perturbation equations are hard to solve unless we can use separation of variables. In the Kerr spacetime, metric perturbations do not separate, but curvature perturbations do. The cost of curvature perturbations is a very complicated metric-reconstruction procedure. This procedure can be avoided using a symmetry-adapted choice of basis functions in highly symmetric spacetimes, such as near-horizon extremal Kerr. In this paper, we focus on this spacetime and (i) construct the symmetry-adapted basis functions; (ii) show their orthogonality; and (iii) show that they lead to separation of...
Renzo, M.; Ott, C. D.; Shore, S. N.; de Mink, S. E.
Mass loss processes are a key uncertainty in the evolution of massive stars. They determine the amount of mass and angular momentum retained by the star, thus influencing its evolution and presupernova structure. Because of the high complexity of the physical processes driving mass loss, stellar evolution calculations must employ parametric algorithms, and usually only include wind mass loss. We carried out an extensive parameter study of wind mass loss and its effects on massive star evolution using the open-source stellar evolution code MESA. We provide a systematic comparison of wind mass loss algorithms for solar-metallicity, nonrotating, single stars in...
Hafen, Zachary; Faucher-Giguère, Claude-André; Anglés-Alcázar, Daniel; Kereš, Dušan; Feldmann, Robert; Chan, T. K.; Quataert, Eliot; Murray, Norman; Hopkins, Philip F.
We use cosmological hydrodynamic simulations with stellar feedback from the FIRE (Feedback In Realistic Environments) project to study the physical nature of Lyman limit systems (LLSs) at z ≤ 1. At these low redshifts, LLSs are closely associated with dense gas structures surrounding galaxies, such as galactic winds, dwarf satellites and cool inflows from the intergalactic medium. Our analysis is based on 14 zoom-in simulations covering the halo mass range M_h ≈ 10^9–10^(13) M⊙ at z = 0, which we convolve with the dark matter halo mass function to produce cosmological statistics. We find that the majority of cosmologically selected...
Feldmann, Robert; Quataert, Eliot; Hopkins, Philip F.; Faucher-Giguère, Claude-André; Kereš, Dušan
We analyse the star formation rates (SFRs), colours and dust extinctions of galaxies in massive (10^(12.5) – 10^(13.5)M⊙) haloes at z ∼ 2 in high-resolution, cosmological zoom-in simulations as part of the Feedback In Realistic Environments (FIRE) project. The simulations do not model feedback from active galactic nuclei (AGNs) but reproduce well the observed relations between stellar and halo mass and between stellar mass and SFR. About half (a third) of the simulated massive galaxies (massive central galaxies) at z ∼ 2 have broad-band colours classifying them as ‘quiescent’, and the fraction of quiescent centrals is steeply decreasing towards higher...
Lee, Hyunseok; Hopkins, Philip F.; Squire, Jonathan
We study the dynamics of large, charged dust grains in turbulent giant molecular clouds (GMCs). Massive dust grains behave as aerodynamic particles in primarily neutral dense gas, and thus are able to produce dramatic small-scale fluctuations in the dust-to-gas ratio. Hopkins & Lee directly simulated the dynamics of neutral dust grains in supersonic magnetohydrodynamic turbulence, typical of GMCs, and showed that the dust-to-gas fluctuations can exceed factor ∼1000 on small scales, with important implications for star formation, stellar abundances and dust behaviour and growth. However, even in primarily neutral gas in GMCs, dust grains are negatively charged and Lorentz forces...
Murchikova, E. M.; Abdikamalov, E.; Urbatsch, T.
Carefully accounting for neutrino transport is an essential component of many astrophysical studies. Solving the full transport equation is too expensive for most realistic applications, especially those involving multiple spatial dimensions. For such cases, resorting to approximations is often the only viable option for obtaining solutions. One such approximation, which recently became popular, is the M1 method. It utilizes the system of the lowest two moments of the transport equation and closes the system with an ad hoc closure relation. The accuracy of the M1 solution depends on the quality of the closure. Several closures have been proposed in the...
Price, Sedona H.; Kriek, Mariska; Feldmann, Robert; Quataert, Eliot; Hopkins, Philip F.; Faucher-Giguère, Claude-André; Kereš, Dušan; Barro, Guillermo
Accurate measurements of galaxy masses and sizes are key to tracing galaxy evolution over time. Cosmological zoom-in simulations provide an ideal test bed for assessing the recovery of galaxy properties from observations. Here, we utilize galaxies with M_* ~ 10^10 - 10^(11.5) M_☉ at z ~ 1.7–2 from the MassiveFIRE cosmological simulation suite, part of the Feedback in Realistic Environments (FIRE) project. Using mock multi-band images, we compare intrinsic galaxy masses and sizes to observational estimates. We find that observations accurately recover stellar masses, with a slight average underestimate of ~ 0.06 dex and a ~ 0.15 dex scatter. Recovered...
Blackman, Jonathan; Field, Scott E.; Scheel, Mark A.; Galley, Chad R.; Ott, Christian D.; Boyle, Michael; Kidder, Lawrence E.; Pfeiffer, Harald P.; Szilágyi, Béla
A generic, noneccentric binary black hole (BBH) system emits gravitational waves (GWs) that are completely described by seven intrinsic parameters: the black hole spin vectors and the ratio of their masses. Simulating a BBH coalescence by solving Einstein’s equations numerically is computationally expensive, requiring days to months of computing resources for a single set of parameter values. Since theoretical predictions of the GWs are often needed for many different source parameters, a fast and accurate model is essential. We present the first surrogate model for GWs from the coalescence of BBHs including all seven dimensions of the intrinsic noneccentric parameter...
Furusawa, S.; Togashi, H.; Nagakura, H.; Sumiyoshi, K.; Yamada, S.; Suzuki, H.; Takano, M.
We have constructed a nuclear equation of state (EOS) that includes a full nuclear ensemble for use in core-collapse supernova simulations. It is based on the EOS for uniform nuclear matter that two of the authors derived recently, applying a variational method to realistic two- and three-body nuclear forces. We have extended the liquid drop model of heavy nuclei, utilizing the mass formula that accounts for the dependences of bulk, surface, Coulomb and shell energies on density and/or temperature. As for light nuclei, we employ a quantum-theoretical mass evaluation, which incorporates the Pauli- and self-energy shifts. In addition to realistic...
Fernández, Rodrigo; Foucart, Francois; Kasen, Daniel; Lippuner, Jonas; Desai, Dhruv; Roberts, Luke F.
We investigate the ejecta from black hole—neutron star mergers by modeling the formation and interaction of mass ejected in a tidal tail and a disk wind. The outflows are neutron-rich, giving rise to optical/infrared emission powered by the radioactive decay of r-process elements (a kilonova). Here we perform an end-to-end study of this phenomenon, where we start from the output of a fully-relativistic merger simulation, calculate the post-merger hydrodynamical evolution of the ejecta and disk winds including neutrino physics, determine the final nucleosynthetic yields using post-processing nuclear reaction network calculations, and compute the kilonova emission with a radiative transfer code....
Fedrow, J. M.; Ott, C. D.; Sperhake, U.; Blackman, J.; Haas, R.; Reisswig, C.; De Felice, A.
We present results from a controlled numerical experiment investigating the effect of stellar density gas on the coalescence of binary black holes (BBHs) and the resulting gravitational waves (GWs). This investigation is motivated by the proposed stellar core fragmentation scenario for BBH formation and the associated possibility of an electromagnetic counterpart to a BBH GW event. We employ full numerical relativity coupled with general-relativistic hydrodynamics and set up a 30+30M_⊙ BBH (motivated by GW150914) inside gas with realistic stellar densities. Our results show that at densities ρ≳10^6−10^7gcm^(−3) dynamical friction between the BHs and gas changes the coalescence dynamics and the...
da Silva Schneider, Andre; Roberts, Luke F.; Ott, Christian D.
The equation of state (EOS) of dense matter is an essential ingredient for
numerical simulations of core-collapse supernovae and neutron star mergers. The
properties of matter near and above nuclear saturation density are uncertain,
which translates into uncertainties in astrophysical simulations and their
multi-messenger signatures. Therefore, a wide range of EOSs spanning the
allowed range of nuclear interactions are necessary for determining the
sensitivity of these astrophysical phenomena and their signatures to variations
in input microphysics. We present a new set of finite temperature EOSs based on
experimentally allowed Skyrme forces. We employ a liquid drop model of nuclei
to capture the non-uniform phase of nuclear matter at sub-saturation...
Hopkins, Philip F.; Squire, Jonathan
Recently, Squire & Hopkins (2017) showed any coupled dust-gas mixture is
subject to a class of linear 'resonant drag instabilities' (RDI). These can
drive large dust-to-gas ratio fluctuations even at arbitrarily small
dust-to-gas mass ratios $\mu$. Here, we explore the RDI in the simple case
where the gas satisfies neutral hydrodynamics and supports acoustic waves
($\omega^{2}=c_{s}^{2}\,k^{2}$). The gas and dust are coupled via an arbitrary
drag law and subject to external accelerations (e.g. gravity, radiation
pressure). If there is any dust drift velocity, the system is unstable. The
instabilities exist for all dust-to-gas ratios $\mu$ and their growth rates
depend only weakly on $\mu$, as $\sim\mu^{1/3}$. The behavior changes...
Zhao, Xinyu; Kesden, Michael; Gerosa, Davide
In the post-Newtonian (PN) regime, the time scale on which the spins of binary black holes precess is much shorter than the radiation-reaction time scale on which the black holes inspiral to smaller separations. On the precession time scale, the angle between the total and orbital angular momenta oscillates with nutation period τ, during which the orbital angular momentum precesses about the total angular momentum by an angle α. This defines two distinct frequencies that vary on the radiation-reaction time scale: the nutation frequency ω≡2π/τ and the precession frequency Ω≡α/τ. We use analytic solutions for generic spin precession at 2PN...
O’Shaughnessy, Richard; Gerosa, Davide; Wysocki, Daniel
The inferred parameters of the binary black hole GW151226 are consistent with nonzero spin for the most massive black hole, misaligned from the binary’s orbital angular momentum. If the black holes formed through isolated binary evolution from an initially aligned binary star, this misalignment would then arise from a natal kick imparted to the first-born black hole at its birth during stellar collapse. We use simple kinematic arguments to constrain the characteristic magnitude of this kick, and find that a natal kick v_k≳50 km/s must be imparted to the black hole at birth to produce misalignments consistent with GW151226. Such large...
O’Shaughnessy, Richard; Blackman, Jonathan; Field, Scott E.
The recent direct observation of gravitational waves has further emphasized the desire for fast, low-cost, and accurate methods to infer the parameters of gravitational wave sources. Due to expense in waveform generation and data handling, the cost of evaluating the likelihood function limits the computational performance of these calculations. Building on recently developed surrogate models and a novel parameter estimation pipeline, we show how to quickly generate the likelihood function as an analytic, closed-form expression. Using a straightforward variant of a production-scale parameter estimation code, we demonstrate our method using surrogate models of effective-one-body and numerical relativity waveforms. Our study...
Guszejnov, Dávid; Hopkins, Philip F.; Krumholz, Mark R.
Stars are strongly clustered on both large (∼pc) and small (∼binary) scales, but there are few analytic or even semi-analytic theories for the correlation function and multiplicity of stars. In this paper, we present such a theory, based on our recently developed semi-analytic framework called MISFIT (Minimalistic Star Formation Including Turbulence), which models gravito-turbulent fragmentation, including the suppression of fragmentation by protostellar radiation feedback. We compare the results including feedback to a control model in which it is omitted. We show that both classes of models robustly reproduce the stellar correlation function at >0.01 pc scales, which is well approximated by...
Muratov, Alexander L.; Kereš, Dušan; Faucher-Giguère, Claude-André; Hopkins, Philip F.; Ma, Xiangcheng; Anglés-Alcázar, Daniel; Chan, T. K.; Torrey, Paul; Hafen, Zachary H.; Quataert, Eliot; Murray, Norman
We present an analysis of the flow of metals through the circumgalactic medium (CGM) in the Feedback in Realistic Environments (FIRE) simulations of galaxy formation, ranging from isolated dwarfs to L* galaxies. We find that nearly all metals produced in high-redshift galaxies are carried out in winds that reach 0.25R_(vir). When measured at 0.25R_(vir) the metallicity of outflows is slightly higher than the interstellar medium (ISM) metallicity. Many metals thus reside in the CGM. Cooling and recycling from this reservoir determine the metal budget in the ISM. The outflowing metal flux decreases by a factor of ∼2–5 between 0.25R_(vir) and...
Gerosa, Davide; Berti, Emanuele
Advanced LIGO detectors at Hanford and Livingston made two confirmed and one marginal detection of binary black holes during their first observing run. The first event, GW150914, was from the merger of two black holes much heavier that those whose masses have been estimated so far, indicating a formation scenario that might differ from “ordinary” stellar evolution. One possibility is that these heavy black holes resulted from a previous merger. When the progenitors of a black hole binary merger result from previous mergers, they should (on average) merge later, be more massive, and have spin magnitudes clustered around a dimensionless...