Volker Bromm

University of Texas at Austin, Austin, Texas, United States

Are you Volker Bromm?

Claim your profile

Publications (150)736.47 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: We present a new near-field cosmological probe of the initial mass function (IMF) of the first stars. Specifically, we constrain the lower-mass limit of the Population III (Pop III) IMF with the total number of stars in large, unbiased surveys of the Milky Way bulge and halo. We model the early star formation history in a Milky-Way like halo with a semi-analytic approach, based on Monte-Carlo sampling of dark matter merger trees, combined with a treatment of the most important feedback mechanisms, such as stellar radiation and metal enrichment. Assuming a logarithmically flat Pop III IMF and varying its low mass limit, we derive the number of expected survivors of these first stars, using them to estimate the probability to detect any such Pop III fossil in stellar archaeological surveys. Our model parameters are calibrated with existing empirical constraints, such as the optical depth to Thomson scattering. Following our analysis, the most promising region to find possible Pop III survivors is the stellar halo of the Milky Way, which is the best target for future surveys. We find that if no genuine Pop III survivor is detected in a sample size, of $4 \times 10^6$ ($2 \times 10^7$) halo stars with well-controlled selection effects, then we can exclude the hypothesis that the primordial IMF extended down below $0.8 M_\odot$ at a confidence level of 68% (99%). With the sample size of the Hamburg/ESO survey, we can tentatively exclude Pop III stars with masses below $0.65 M_\odot$ with a confidence level of 95%, although this is subject to significant uncertainties. To fully harness the potential of our approach, future large surveys are needed that employ uniform, unbiased selection strategies for high-resolution spectroscopic follow-up.
    11/2014;
  • [Show abstract] [Hide abstract]
    ABSTRACT: We present the Cosmic Lyman-$\alpha$ Transfer code (COLT), a new massively parallel Monte-Carlo radiative transfer code, to simulate Lyman-$\alpha$ (Ly$\alpha$) resonant scattering through neutral hydrogen as a probe of the first galaxies. We explore the interaction of centrally produced Ly$\alpha$ radiation with the host galactic environment. The Ly$\alpha$ photons emitted from the luminous starburst region escape with characteristic features in the line profile depending on the density distribution, ionization structure, and bulk velocity fields. For example, the presence of anisotropic ionization exhibits a tall peak close to line centre with a skewed tail that drops off gradually. Furthermore, moderate (~10 km/s) outflow produces an amplified peak redward of line centre. Idealized models of first galaxies explore the effect of mass, anisotropic H II regions, and radiation pressure driven winds on Ly$\alpha$ observables. We employ mesh refinement to resolve critical structures. We also post-process an ab initio cosmological simulation and examine images captured at various escape distances within the 1 Mpc$^3$ comoving volume. Finally, we discuss the emergent spectra and surface brightness profiles of these objects in the context of high-$z$ observations. The first galaxies will likely be observed through the red damping wing of the Ly$\alpha$ line. Observations will be biased toward galaxies with an intrinsic red peak located far from line centre that reside in extensive H II super bubbles, which allows Hubble flow to sufficiently redshift photons away from line centre and thereby facilitate transmission through the intergalactic medium (IGM). Even with gravitational lensing to boost the luminosity we predict that Ly$\alpha$ emission from stellar clusters within haloes of $M_{\rm vir}<10^9~{\rm M}_\odot$ is generally too faint to be detected by the James Webb Space Telescope (JWST).
    09/2014;
  • Volker Bromm
    Science (New York, N.Y.). 08/2014; 345(6199):868-9.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: To constrain the properties of the first stars with the chemical abundance patterns observed in metal-poor stars, one must identify any non-trivial effects that the hydrodynamics of metal dispersal can imprint on the abundances. We use realistic cosmological hydrodynamic simulations to quantify the distribution of metals resulting from one Population III supernova and from a small number of such supernovae. Overall, supernova ejecta remain highly inhomogeneous throughout the simulations. When the supernova bubbles collapse, quasi-virialized metal-enriched clouds, fed by fallback from the bubbles and by streaming of metal-free gas from the cosmic web, grow in the centers of the dark matter halos. Partial turbulent homogenization on scales resolved in the simulation is observed in the clouds, and the vortical time scales are short enough to ensure true homogenization on subgrid scales. However, the abundances in the clouds differ from the gross yields of the supernovae. Continuing the simulations until the cloud have gone into gravitational collapse, we predict that the abundances in second-generation stars will be deficient in the innermost mass shells of the supernova (if only one has exploded) or in the ejecta of the latest supernovae (when multiple have exploded). This indicates that hydrodynamics gives rise to biases complicating linear mapping between nucleosynthetic sources and abundance patterns in surviving stars.
    08/2014;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We present the results of the stellar feedback from Pop~III binaries by employing improved, more realistic Pop~III evolutionary stellar models. To facilitate a meaningful comparison, we consider a fixed mass of 60 solar masses (Msun) incorporated in Pop~III stars, either contained in a single star, or split up in binary stars of 30 Msun each or an asymmetric case of one 45 Msun and one 15 Msun star. Whereas the sizes of the resulting HII regions are comparable across all cases, the HeIII regions around binary stars are significantly smaller than that of the single star. Consequently, the He$^{+}$ 1640 angstrom recombination line is expected to become much weaker. Supernova feedback exhibits great variety due to the uncertainty in possible explosion pathways. If at least one of the component stars dies as a hypernova about ten times more energetic than conventional core-collapse supernovae, the gas inside the host minihalo is effectively blown out, chemically enriching the intergalactic medium (IGM) to an average metallicity of $10^{-4}-10^{-3}$ solar metallicity (Zsun), out to $\sim 2$ kpc. The single star, however, is more likely to collapse into a black hole, accompanied by at most very weak explosions. The effectiveness of early chemical enrichment would thus be significantly reduced, in difference from the lower mass binary stars, where at least one component is likely to contribute to heavy element production and dispersal. Important new feedback physics is also introduced if close binaries can form high-mass x-ray binaries, leading to the pre-heating and -ionization of the IGM beyond the extent of the stellar HII regions.
    07/2014;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We investigate the impact of an ionising X-ray background on metal-free Population III stars within a minihalo at $z\simeq25$ starting from cosmological initial conditions. Using the smoothed particle hydrodynamics code GADGET-2, we attain sufficient numerical resolution to follow the gas collapsing into the centre of the minihalo up to densities of $n=10^{12}\,cm^{-3}$, at which point we form sink particles. This allows us to study how the presence of a cosmic X-ray background (CXB) affects the formation of H$_2$ and HD in the gas before it becomes fully molecular. Using a suite of simulations for a range of possible CXB models, we follow each simulation for 5000 yr after the formation of the first sink particle. The CXB provides two competing effects, with X-rays both heating the gas and enhancing its ability to cool by increasing the free electron fraction, allowing more H$_2$ to form. We find that X-ray heating dominates below $n\sim1\,cm^{-3}$, while the additional cooling catalysed by X-ray ionisation becomes more important above $n\sim10^2\,cm^{-3}$. Heating the gas impedes its collapse, decreasing the total amount of gas available for star formation. However if the CXB is strong enough, the gas that does collapse cools sufficiently to activate HD cooling, leading to further cooling and fragmentation. If at the same time the CXB is also not so strong as to choke off the supply of gas collapsing into the halo, this additional cooling allows more of the available gas to collapse to high densities, counteracting the effects of X-ray heating at low densities and increasing both the total mass and number of sink particles dramatically. This leads to a `Goldilocks' range of CXB strengths for which fragmentation increases significantly, from 2-3 sink particles to 10; continuing to increase the CXB chokes off the gas supply and suppresses both sink formation and fragmentation.
    07/2014;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We use cosmological simulations to assess how the explosion of the first stars in supernovae (SNe) influences early cosmic history. Specifically, we investigate the impact by SNe on the host systems for Population III (Pop III) star formation and explore its dependence on halo environment and Pop III progenitor mass. We then trace the evolution of the enriched gas until conditions are met to trigger second-generation star formation. To this extent, we quantify the recovery timescale, which measures the time delay between a Pop III SN explosion and the appearance of cold, dense gas, out of which second-generation stars can form. We find that this timescale is highly sensitive to the Pop III progenitor mass, and less so to the halo environment. For Pop III progenitor masses M < 40 solar mass, recovery is prompt, ~ 10 Myr. For more massive progenitors, including those exploding in pair instability SNe, second-generation star formation is delayed significantly, for up to a Hubble time. The dependence of the recovery time on the mass of the SN progenitor is mainly due to the ionizing impact of the progenitor star. Photoionization heating increases the gas pressure and initiates a hydrodynamical response that reduces the central gas density, an effect that is stronger in more massive and hence more luminous progenitors. The gas around lower mass Pop III stars remains therefore denser and hence the SN remnants cool more rapidly, facilitating the subsequent re-condensation of the gas and formation of a second generation of stars. In most cases, the second-generation stars are already metal-enriched, thus belonging to Population II. The recovery timescale is a key quantity governing the nature of the first galaxies, able to host low-mass, long-lived stellar systems. These in turn are the target of future deep-field campaigns with the James Webb Space Telescope.
    06/2014;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We simulate the formation of a metal-poor ($10^{-2}\,Z_{\odot}$) stellar cluster in one of the first galaxies to form in the early Universe, specifically a high-redshift atomic cooling halo ($z\sim14$). This is the first calculation that resolves the formation of individual metal-enriched stars in simulations starting from realistic cosmological initial conditions. We follow the evolution of a single dense clump among several in the parent halo. The clump forms a cluster of $\sim40$ stars and sub-stellar objects within $7000$ yrs and could continue forming stars $\sim5$ times longer. Protostellar dust heating has a negligible effect on the star formation efficiency, at least during the early evolutionary stages, but it moderately suppresses gaseous fragmentation and brown dwarf formation. We observe fragmentation in thin gaseous filaments and sustained accretion in larger, rotating structures as well as ejections by binary interactions. The stellar initial mass function above $0.1\,M_{\odot}$, evaluated after $\sim10^4$ yrs of fragmentation and accretion, seems in agreement with the recent measurement in ultra-faint dwarf spheroidal Galactic satellites of Geha et al. (2013).
    01/2014; 440(1).
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We use cosmological simulations of high-redshift minihalos to investigate the effect of dark matter annihilation (DMA) on the collapse of primordial gas. We numerically investigate the evolution of the gas as it assembles in a Population III stellar disk. We find that when DMA effects are neglected, the disk undergoes multiple fragmentation events beginning at ~ 500 yr after the appearance of the first protostar. On the other hand, DMA heating and ionization of the gas speeds the initial collapse of gas to protostellar densities and also affects the stability of the developing disk against fragmentation, depending on the DM distribution. We compare the evolution when we model the DM density with an analytical DM profile which remains centrally peaked, and when we simulate the DM profile using N-body particles (the 'live' DM halo). When utilizing the analytical DM profile, DMA suppresses disk fragmentation for ~ 3500 yr after the first protostar forms, in agreement with earlier work. However, when using a 'live' DM halo, the central DM density peak is gradually flattened due to the mutual interaction between the DM and the rotating gaseous disk, reducing the effects of DMA on the gas, and enabling secondary protostars of mass ~ 1 M_sol to be formed within ~ 900 yr. These simulations demonstrate that DMA is ineffective in suppressing gas collapse and subsequent fragmentation, rendering the formation of long-lived dark stars unlikely. However, DMA effects may still be significant in the early collapse and disk formation phase of primordial gas evolution.
    12/2013; 441(1).
  • Source
    Volker Bromm
    [Show abstract] [Hide abstract]
    ABSTRACT: Understanding the formation of the first stars is one of the frontier topics in modern astrophysics and cosmology. Their emergence signalled the end of the cosmic dark ages, a few hundred million years after the Big Bang, leading to a fundamental transformation of the early Universe through the production of ionizing photons and the initial enrichment with heavy chemical elements. We here review the state of our knowledge, separating the well understood elements of our emerging picture from those where more work is required. Primordial star formation is unique in that its initial conditions can be directly inferred from the Λ cold dark matter (ΛCDM) model of cosmological structure formation. Combined with gas cooling that is mediated via molecular hydrogen, one can robustly identify the regions of primordial star formation, the so-called minihalos, having total masses of ∼10(6) M⊙ and collapsing at redshifts z ≃ 20-30. Within this framework, a number of studies have defined a preliminary standard model, with the main result that the first stars were predominantly massive. This model has recently been modified to include a ubiquitous mode of fragmentation in the protostellar disks, such that the typical outcome of primordial star formation may be the formation of a binary or small multiple stellar system. We will also discuss extensions to this standard picture due to the presence of dynamically significant magnetic fields, of heating from self-annihalating WIMP dark matter, or cosmic rays. We conclude by discussing possible strategies to empirically test our theoretical models. Foremost among them are predictions for the upcoming James Webb space telescope (JWST), to be launched ∼2018, and for 'stellar archaeology', which probes the abundance pattern in the oldest, most-metal poor stars in our cosmic neighborhood, thereby constraining the nucleosynthesis inside the first supernovae.
    Reports on Progress in Physics 10/2013; 76(11):112901. · 13.23 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Recent work suggests that the first generation of stars, the so-called Population III (Pop III), could have formed primarily in binaries or as members of small multiple systems. Here we investigate the impact of X-ray feedback from High-Mass X-ray Binaries (HMXBs) left behind in stellar binary systems after the primary forms a black hole (BH), accreting gas at a high rate from the companion, a process that is thought to be favored at the low metallicities characteristic of high-redshift gas. Thanks to their large mean free path, X-rays are capable of preionizing and preheating the gas in the intergalactic medium (IGM) and in haloes long before the reionization of the Universe is complete, and thus could have strongly affected the formation of subsequent generations of stars as well as reionization. We have carried out zoomed hydrodynamical cosmological simulations of minihaloes, accounting for the formation of Pop III stars and their collapse into BHs and HMXBs, and the associated radiation-hydrodynamic feedback from UV and X-ray photons. We find no strong net feedback from HMXBs on the simulated star formation history. On the other hand, the preheating of the IGM by HMXBs leads to a strong suppression of small-scale structures and significantly lowers the recombination rate in the IGM, thus yielding a net positive feedback on reionization. We further show that X-ray feedback from HMXBs can augment the ionizing feedback from the Pop III progenitor stars to suppress gas accretion onto the first BHs, limiting their growth into supermassive BHs. Finally, we show that X-ray ionization by HMXBs leaves distinct signatures in the properties of the high-redshift hydrogen that may be probed in upcoming observations of the redshifted 21cm spin-flip line.
    10/2013; 440(4).
  • [Show abstract] [Hide abstract]
    ABSTRACT: Population III stars are believed to have been more massive than typical stars today and to have formed in relative isolation. The thermodynamic impact of metals is expected to induce a transition leading to clustered, low-mass Population II star formation. In this work, we present results from three cosmological simulations, only differing in gas metallicity, that focus on the impact of metal fine-structure line cooling on the formation of stellar clusters in a high-redshift atomic cooling halo. Introduction of sink particles allows us to follow the process of gas hydrodynamics and accretion onto cluster stars for 4 Myr corresponding to multiple local free-fall times. At metallicities at least 10^-3 Zsun, gas is able to reach the CMB temperature floor and fragment pervasively resulting in a stellar cluster of size ~1 pc and total mass ~1000 Msun. The masses of individual sink particles vary, but are typically ~100 Msun, consistent with the Jeans mass when gas cools to the CMB temperature, though some solar mass fragments are also produced. At the low metallicity of 10^-4 Zsun, fragmentation is completely suppressed on scales greater than 0.01 pc and total stellar mass is lower by a factor of 3 than in the higher metallicity simulations. The sink particle accretion rates, and thus their masses, are determined by the mass of the gravitationally unstable gas cloud and the prolonged gas accretion over many Myr. The simulations thus exhibit features of both monolithic collapse and competitive accretion. Even considering possible dust induced fragmentation that would occur at higher densities, the formation of a bona fide stellar cluster seems to require metal line cooling and metallicities of at least 10^-3 Zsun.
    Monthly Notices of the Royal Astronomical Society 07/2013; · 5.52 Impact Factor
  • Source
    Alexander P. Ji, Anna Frebel, Volker Bromm
    [Show abstract] [Hide abstract]
    ABSTRACT: We investigate the impact of dust-induced gas fragmentation on the formation of the first low-mass, metal-poor stars (< 1M_sun) in the early universe. Previous work has posited the existence of a critical dust-to-gas ratio, below which dust thermal cooling is unable to cause fragmentation. Using silicon-based (rather than carbon-based) dust compositions, we compute such critical dust-to-gas ratios and associated critical silicon abundances. We evaluate the robustness of these critical values by considering variations in the dust chemical composition, grain size distribution, and star formation environment. Variations in the dust chemical composition are less important than variations in the size distribution, and the most likely environment where dust cooling becomes significant is in a rotationally supported protostellar disk. We test the dust cooling theory by comparing to silicon abundances observed in metal-poor stars. Several stars have silicon abundances low enough to rule out fragmentation induced by dust which follows a standard Milky Way grain size distribution. Moreover, two of the most iron-poor stars have such low silicon abundances that even dust with a shocked grain size distribution cannot easily explain their formation. We see evidence that stars with [Fe/H] < -4.0 exhibit either high carbon and low silicon abundances or the reverse. This suggests that the earliest low-mass star formation in the most metal-poor regime likely proceeded through two distinct pathways, one that relied on fine structure cooling and one that relied on dust cooling. This naturally explains both the carbon-rich and carbon-normal stars at extremely low [Fe/H].
    07/2013;
  • Source
    Athena Stacy, Volker Bromm
    [Show abstract] [Hide abstract]
    ABSTRACT: We perform numerical simulations of the growth of a Population III stellar system under photodissociating feedback. We start from cosmological initial conditions at z = 100, self-consistently following the formation of a minihalo at z = 15 and the subsequent collapse of its central gas to high densities. The simulations resolve scales as small as ~ 1 AU, corresponding to gas densities of 10^16 cm^-3. Using sink particles to represent the growing protostars, we evolve the stellar system for the next 5000 years. We find that this emerging stellar group accretes at an unusually low rate compared with minihalos which form at earlier times (z = 20 - 30), or with lower baryonic angular momentum. The stars in this unusual system will likely reach masses ranging from < 1 M_sun to 5 M_sun by the end of their main-sequence lifetimes, placing them in the mass range for which stars will undergo an asymptotic giant branch (AGB) phase. Based upon the simulation, we predict the existence of Population III stars that have survived to the present day and have been enriched by mass overflow from a previous AGB companion.
    The Astrophysical Journal 07/2013; · 6.73 Impact Factor
  • Source
    Milos Milosavljevic, Volker Bromm
    [Show abstract] [Hide abstract]
    ABSTRACT: The population of dwarf spheroidal satellite galaxies in the Local Group has emerged as a powerful probe of dark matter clustering on small spatial scales and of cosmic reionization. The dwarf spheroidals are also interesting in view of the continuity of structural and chemical properties they share with each other, with dwarf irregular galaxies in the field, and with the more massive spheroidal galaxies in high-density environments. By connecting empirical constraints derived for star formation at low gas column densities and metallicities in the local universe with a model for dark matter and baryonic mass assembly, we provide an analytical description of how the dwarf spheroidals acquired their stellar content. Their progenitors formed stars until their gas content, initially reduced from the cosmic average by the thermal pressure of the reionized intergalactic medium, is finally ram pressure stripped during the progenitors' accretion onto the host galaxy. Dwarf spheroidal satellites of differing luminosities seem to share very similar most massive progenitor histories that reach thresholds for gas cooling by atomic line emission at epochs at which the Lagrangian volume of the Local Group should have been reionized. We hypothesize that it is the star formation in a reionized universe, rather than preceding reionization, that defines their properties. This model provides an explanation for the "common mass scale" relation of Strigari et al. (2008) and reproduces the empirical luminosity-size and luminosity-metallicity relations if assuming that star formation was quiescent and confined to the cold atomic phase stochastically condensing in partially rotationally supported HI disks.
    06/2013;
  • [Show abstract] [Hide abstract]
    ABSTRACT: We investigate the operation of the chemothermal instability in primordial star-forming clouds with a suite of three-dimensional, moving-mesh simulations. In line with previous studies, we find that the gas at the centre of high-redshift minihaloes becomes chemothermally unstable as three-body reactions convert the atomic hydrogen into a fully molecular gas. The competition between the increasing rate at which the gas cools and the increasing optical depth to H2 line emission creates a characteristic dip in the cooling time over the free-fall time on a scale of 100 au. As a result, the free-fall time decreases to below the sound-crossing time, and the cloud may become gravitationally unstable and fragment on a scale of a few tens of au during the initial free-fall phase. In three of the nine haloes investigated, secondary clumps condense out of the parent cloud, which will likely collapse in their own right before they are accreted by the primary clump. In the other haloes, fragmentation at such an early stage is less likely. However, given that previous simulations have shown that the infall velocity decreases substantially once the gas becomes rotationally supported, the amount of time available for perturbations to develop may be much greater than is evident from the limited period of time simulated here.
    Monthly Notices of the Royal Astronomical Society 05/2013; 434(4). · 5.52 Impact Factor
  • Volker Bromm
    Science 11/2012; 338(6111):1160-1. · 31.20 Impact Factor
  • Source
    Athena Stacy, Volker Bromm
    [Show abstract] [Hide abstract]
    ABSTRACT: We perform a cosmological simulation in order to model the growth and evolution of Population III (Pop III) stellar systems in a range of host minihalo environments. A Pop III multiple system forms in each of the ten minihaloes, and the overall mass function is top-heavy compared to the currently observed initial mass function in the Milky Way. Using a sink particle to represent each growing protostar, we examine the binary characteristics of the multiple systems, resolving orbits on scales as small as 20 AU. We find a binary fraction of ~36%, with semi-major axes as large as 3000 AU. The distribution of orbital periods is slightly peaked at < 900 yr, while the distribution of mass ratios is relatively flat. Of all sink particles formed within the ten minihaloes, ~50% are lost to mergers with larger sinks, and ~50% of the remaining sinks are ejected from their star-forming disks. The large binary fraction may have important implications for Pop III evolution and nucleosynthesis, as well as the final fate of the first stars.
    Monthly Notices of the Royal Astronomical Society 11/2012; 433(2). · 5.52 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We analyze the cosmological simulations performed in the recent work of Greif et al. (2012), which followed the early growth and merger history of Pop III stars while resolving scales as small as 0.05 R_sol. This is the first set of cosmological simulations to self-consistently resolve the rotation and internal structure of Pop III protostars. We find that Pop III stars form under significant rotational support which is maintained for the duration of the simulations. The protostellar surfaces spin from ~50% to nearly 100% of Keplerian rotational velocity. These rotation rates persist after experiencing multiple stellar merger events. In the brief time period simulated (~ 10 yr), the protostars show little indication of convective instability, and their properties furthermore show little correlation with the properties of their host minihaloes. If Pop III protostars within this range of environments generally form with high degrees of rotational support, and if this rotational support is maintained for a sufficient amount of time, this has a number of crucial implications for Pop III evolution and nucleosynthesis, as well as the possibility for Pop III pair-instability supernovae, and the question of whether the first stars produced gamma-ray bursts.
    Monthly Notices of the Royal Astronomical Society 09/2012; 431(2). · 5.52 Impact Factor
  • Athena Stacy, Thomas H. Greif, Volker Bromm
    [Show abstract] [Hide abstract]
    ABSTRACT: We perform 3-D cosmological simulations to examine the growth of metal-free, Population III (Pop III) stars under radiative feedback. We trace the evolution of gas and dark matter until the formation of the first minihalo, and follow the collapse of the minihalo's gas up to densities of n = 1012cm-3. We then implement the sink particle method while modeling the effect of Lyman-Werner (LW) and ionizing radiation emitted by the initial protostar over the next 5000 yr. A disk assembles around the first protostar, and radiative feedback does not prevent further fragmentation of the disk to form multiple Pop III stars. Feedback leads to heating of the dense gas to several thousand Kelvin, and this warm region expands outward at the gas sound speed. Once this region extends to the size of the disk, the disk mass declines while the accretion rate onto the protostars is reduced by an order of magnitude. The main sink will approach an asymptotic value of 30 Msolar by the time it reaches the main sequence. Such unexpectedly low Pop III masses may have important consequences for the occurrence of pair-instability supernovae in the early Universe as well as the Pop III chemical signature in the oldest stars observable today.
    09/2012;

Publication Stats

4k Citations
736.47 Total Impact Points

Institutions

  • 2004–2014
    • University of Texas at Austin
      • Department of Astronomy
      Austin, Texas, United States
  • 2013
    • University of California, Berkeley
      Berkeley, California, United States
  • 2007–2011
    • Universität Heidelberg
      • Institute of Theoretical Physics
      Heidelberg, Baden-Wuerttemberg, Germany
  • 2010
    • Heidelberg University
      Tiffin, Ohio, United States
    • Stanford University
      Palo Alto, California, United States
  • 2002–2004
    • Harvard University
      • Department of Astronomy
      Cambridge, MA, United States
    • University of Cambridge
      • Institute of Astronomy
      Cambridge, England, United Kingdom
  • 2001–2004
    • Harvard-Smithsonian Center for Astrophysics
      • Smithsonian Astrophysical Observatory
      Cambridge, Massachusetts, United States
  • 2003
    • University of Exeter
      Exeter, England, United Kingdom
    • National Astronomical Observatory of Japan
      Edo, Tōkyō, Japan
  • 1998–2002
    • Yale University
      • Department of Astronomy
      New Haven, Connecticut, United States