Recursos de colección

Caltech Authors (160.010 recursos)

Repository of works by Caltech published authors.

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Mostrando recursos 1 - 20 de 439

  1. SIDM on fire: hydrodynamical self-interacting dark matter simulations of low-mass dwarf galaxies

    Robles, Victor H.; Bullock, James S.; Elbert, Oliver D.; Fitts, Alex; González-Samaniego, Alejandro; Boylan-Kolchin, Michael; Hopkins, Philip F.; Faucher-Giguère, Claude-André; Kereš, Dušan; Hayward, Christopher C.
    We compare a suite of four simulated dwarf galaxies formed in 10^(10)  M⊙ haloes of collisionless cold dark matter (CDM) with galaxies simulated in the same haloes with an identical galaxy formation model but a non-zero cross-section for DM self-interactions. These cosmological zoom-in simulations are part of the Feedback In Realistic Environments (FIRE) project and utilize the FIRE-2 model for hydrodynamics and galaxy formation physics. We find the stellar masses of the galaxies formed in self-interacting dark matter (SIDM) with σ/m = 1 cm^2 g^(−1) are very similar to those in CDM (spanning M⋆ ≈ 10^(5.7–7.0)M⊙) and all runs lie on a similar...

  2. Heartbeat stars, tidally excited oscillations and resonance locking

    Fuller, Jim
    Heartbeat stars are eccentric binary stars in short-period orbits whose light curves are shaped by tidal distortion, reflection and Doppler beaming. Some heartbeat stars exhibit tidally excited oscillations and present new opportunities for understanding the physics of tidal dissipation within stars. We present detailed methods to compute the forced amplitudes, frequencies and phases of tidally excited oscillations in eccentric binary systems. Our methods (i) factor out the equilibrium tide for easier comparison with observations, (ii) account for rotation using the traditional approximation, (iii) incorporate non-adiabatic effects to reliably compute surface luminosity perturbations, (iv) allow for spin–orbit misalignment and (v) correctly...

  3. Heartbeat stars, tidally excited oscillations and resonance locking

    Fuller, Jim
    Heartbeat stars are eccentric binary stars in short-period orbits whose light curves are shaped by tidal distortion, reflection and Doppler beaming. Some heartbeat stars exhibit tidally excited oscillations and present new opportunities for understanding the physics of tidal dissipation within stars. We present detailed methods to compute the forced amplitudes, frequencies and phases of tidally excited oscillations in eccentric binary systems. Our methods (i) factor out the equilibrium tide for easier comparison with observations, (ii) account for rotation using the traditional approximation, (iii) incorporate non-adiabatic effects to reliably compute surface luminosity perturbations, (iv) allow for spin–orbit misalignment and (v) correctly...

  4. Comparing models for IMF variation across cosmological time in Milky Way-like galaxies

    Guszejnov, Dávid; Hopkins, Philip F.; Ma, Xiangcheng
    One of the key observations regarding the stellar initial mass function (IMF) is its near-universality in the Milky Way (MW), which provides a powerful way to constrain different star formation models that predict the IMF. However, those models are almost universally ‘cloud-scale’ or smaller – they take as input or simulate single molecular clouds (GMCs), clumps or cores, and predict the resulting IMF as a function of the cloud properties. Without a model for the progenitor properties of all clouds that formed the stars at different locations in the MW (including ancient stellar populations formed in high redshift, likely gas-rich...

  5. Comparing models for IMF variation across cosmological time in Milky Way-like galaxies

    Guszejnov, Dávid; Hopkins, Philip F.; Ma, Xiangcheng
    One of the key observations regarding the stellar initial mass function (IMF) is its near-universality in the Milky Way (MW), which provides a powerful way to constrain different star formation models that predict the IMF. However, those models are almost universally ‘cloud-scale’ or smaller – they take as input or simulate single molecular clouds (GMCs), clumps or cores, and predict the resulting IMF as a function of the cloud properties. Without a model for the progenitor properties of all clouds that formed the stars at different locations in the MW (including ancient stellar populations formed in high redshift, likely gas-rich...

  6. Halo histories versus Galaxy properties at z = 0 – I. The quenching of star formation

    Tinker, Jeremy L.; Wetzel, Andrew R.; Conroy, Charlie; Mao, Yao-Yuan
    We test whether halo age and galaxy age are correlated at fixed halo and galaxy mass. The formation histories, and thus ages, of dark matter haloes correlate with their large-scale density ρ, an effect known as assembly bias. We test whether this correlation extends to galaxies by measuring the dependence of galaxy stellar age on ρ. To clarify the comparison between theory and observation, and to remove the strong environmental effects on satellites, we use galaxy group catalogues to identify central galaxies and measure their quenched fraction, f_Q, as a function of large-scale environment. Models that match halo age to...

  7. Halo histories versus Galaxy properties at z = 0 – I. The quenching of star formation

    Tinker, Jeremy L.; Wetzel, Andrew R.; Conroy, Charlie; Mao, Yao-Yuan
    We test whether halo age and galaxy age are correlated at fixed halo and galaxy mass. The formation histories, and thus ages, of dark matter haloes correlate with their large-scale density ρ, an effect known as assembly bias. We test whether this correlation extends to galaxies by measuring the dependence of galaxy stellar age on ρ. To clarify the comparison between theory and observation, and to remove the strong environmental effects on satellites, we use galaxy group catalogues to identify central galaxies and measure their quenched fraction, f_Q, as a function of large-scale environment. Models that match halo age to...

  8. Stellar feedback strongly alters the amplification and morphology of galactic magnetic fields

    Su, Kung-Yi; Hayward, Christopher C.; Hopkins, Philip F.; Quataert, Eliot; Faucher-Giguère, Claude-André; Kereš, Dušan
    Using high-resolution magnetohydrodynamic simulations of idealized, non-cosmological galaxies, we investigate how cooling, star formation, and stellar feedback affect galactic magnetic fields. We find that the amplification histories, saturation values, and morphologies of the magnetic fields vary considerably depending on the baryonic physics employed, primarily because of differences in the gas density distribution. In particular, adiabatic runs and runs with a sub-grid (effective equation of state) stellar feedback model yield lower saturation values and morphologies that exhibit greater large-scale order compared with runs that adopt explicit stellar feedback and runs with cooling and star formation but no feedback. The discrepancies mostly lie in gas denser than the galactic average, which requires cooling...

  9. Modeling chemical abundance distributions for dwarf galaxies in the Local Group: the impact of turbulent metal diffusion

    Escala, Ivanna; Wetzel, Andrew; Kirby, Evan N.; Hopkins, Philip F.; Ma, Xiangcheng; Wheeler, Coral; Kereš, Dušan; Faucher-Giguère, Claude-André; Quataert, Eliot
    We investigate stellar metallicity distribution functions (MDFs), including Fe and ${\alpha}$-element abundances, in dwarf galaxies from the Feedback in Realistic Environments (FIRE) project. We examine both isolated dwarf galaxies and those that are satellites of a Milky Way-mass galaxy. In particular, we study the effects of including a sub-grid turbulent model for the diffusion of metals in gas. Simulations that include diffusion have narrower MDFs and abundance ratio distributions, because diffusion drives individual gas and star particles toward the average metallicity. This effect provides significantly better agreement with observed abundance distributions of dwarf galaxies in the Local Group, including the small intrinsic scatter in [${\alpha}$/Fe] vs. [Fe/H] (less than 0.1...

  10. Simulating galaxies in the reionization era with FIRE-2: morphologies and sizes

    Ma, Xiangcheng; Hopkins, Philip F.; Boylan-Kolchin, Michael; Faucher-Giguère, Claude-André; Quataert, Eliot; Feldmann, Robert; Garrison-Kimmel, Shea; Hayward, Christopher C.; Kereš, Dušan; Wetzel, Andrew
    We study the morphologies and sizes of galaxies at z>5 using high-resolution cosmological zoom-in simulations from the Feedback In Realistic Environments project. The galaxies show a variety of morphologies, from compact to clumpy to irregular. The simulated galaxies have more extended morphologies and larger sizes when measured using rest-frame optical B-band light than rest-frame UV light; sizes measured from stellar mass surface density are even larger. The UV morphologies are usually dominated by several small, bright young stellar clumps that are not always associated with significant stellar mass. The B-band light traces stellar mass better than the UV, but it can also be biased by the bright clumps. At...

  11. Stacked Star Formation Rate Profiles of Bursty Galaxies Exhibit “Coherent” Star Formation

    Orr, Matthew E.; Hayward, Christopher C.; Nelson, Erica J.; Hopkins, Philip F.; Faucher-Giguère, Claude-André; Kereš, Dušan; Chan, T. K.; Schmitz, Denise M.; Miller, Tim B.
    In a recent work based on 3200 stacked Hα maps of galaxies at z ~ 1, Nelson et al. find evidence for "coherent star formation": the stacked star formation rate (SFR) profiles of galaxies above (below) the "star formation main sequence" (MS) are above (below) that of galaxies on the MS at all radii. One might interpret this result as inconsistent with highly bursty star formation and evidence that galaxies evolve smoothly along the MS rather than crossing it many times. We analyze six simulated galaxies at z ~ 1 from the Feedback in Realistic Environments (FIRE) project in a...

  12. Neutrino Emissions in All Flavors up to the Pre-bounce of Massive Stars and the Possibility of Their Detections

    Kato, Chinami; Nagakura, Hiroki; Furusawa, Shun; Takahashi, Koh; Umeda, Hideyuki; Yoshida, Takashi; Ishidoshiro, Koji; Yamada, Shoichi
    This paper is a sequel to our 2015 paper, Kato et al., which calculated the luminosities and spectra of electron-type anti-neutrinos (ν[overbar]_e) from the progenitors of core-collapse supernovae. Expecting that the capability to detect electron-type neutrinos (ν_e) will increase dramatically with the emergence of liquid-argon detectors such as DUNE, we broaden the scope in this study to include all flavors of neutrinos emitted from the pre-bounce phase. We pick up three progenitor models of electron capture supernovae (ECSNe) and iron-core collapse supernovae (FeCCSNe). We find that the number luminosities reach ~10^(57) s^(–1) and ~10^(53) s^(–1) at maximum for ν_e and...

  13. A Detailed Comparison of Multidimensional Boltzmann Neutrino Transport Methods in Core-collapse Supernovae

    Richers, Sherwood; Nagakura, Hiroki; Ott, Christian D.; Dolence, Joshua; Sumiyoshi, Kohsuke; Yamada, Shoichi
    The mechanism driving core-collapse supernovae is sensitive to the interplay between matter and neutrino radiation. However, neutrino radiation transport is very difficult to simulate, and several radiation transport methods of varying levels of approximation are available. We carefully compare for the first time in multiple spatial dimensions the discrete ordinates (DO) code of Nagakura, Yamada, and Sumiyoshi and the Monte Carlo (MC) code Sedonu, under the assumptions of a static fluid background, flat spacetime, elastic scattering, and full special relativity. We find remarkably good agreement in all spectral, angular, and fluid interaction quantities, lending confidence to both methods. The DO...

  14. Not so lumpy after all: modelling the depletion of dark matter subhaloes by Milky Way-like galaxies

    Garrison-Kimmel, Shea; Wetzel, Andrew; Bullock, James S.; Hopkins, Philip F.; Boylan-Kolchin, Michael; Faucher-Giguère, Claude-André; Kereš, Dušan; Quataert, Eliot; Sanderson, Robyn E.; Graus, Andrew S.; Kelley, Tyler
    Among the most important goals in cosmology is detecting and quantifying small (M_(halo)≃10^(6−9) M⊙) dark matter (DM) subhaloes. Current probes around the Milky Way (MW) are most sensitive to such substructure within ∼20 kpc of the halo centre, where the galaxy contributes significantly to the potential. We explore the effects of baryons on subhalo populations in ΛCDM using cosmological zoom-in baryonic simulations of MW-mass haloes from the Latte simulation suite, part of the Feedback In Realistic Environments (FIRE) project. Specifically, we compare simulations of the same two haloes run using (1) DM-only (DMO), (2) full baryonic physics and (3) DM...

  15. The distribution of density in supersonic turbulence

    Squire, Jonathan; Hopkins, Philip F.
    We propose a model for the statistics of the mass density in supersonic turbulence, which plays a crucial role in star formation and the physics of the interstellar medium (ISM). The model is derived by considering the density to be arranged as a collection of strong shocks of width ∼M^(-2), where M is the turbulent Mach number. With two physically motivated parameters, the model predicts all density statistics for M > 1 turbulence: the density probability distribution and its intermittency (deviation from lognormality), the density variance–Mach number relation, power spectra and structure functions. For the proposed model parameters, reasonable agreement...

  16. Gemini Observations of Galaxies in Rich Early Environments (GOGREEN) I: survey description

    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...

  17. Separating metric perturbations in near-horizon extremal Kerr spacetimes

    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...

  18. Systematic survey of the effects of wind mass loss algorithms on the evolution of single massive stars

    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...

  19. Low-redshift Lyman limit systems as diagnostics of cosmological inflows and outflows

    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...

  20. Colours, star formation rates and environments of star-forming and quiescent galaxies at the cosmic noon

    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...

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