Some First Stars Were Red: Detecting Signatures of Massive Population III Formation Through Long-Term Stochastic Color Variations
TL;DR: In this paper, high-resolution cosmological zoom-in simulations of massive star formation in high-z halos were used to identify stars formed in pristine environments (Pop III) within the first billion years.
Abstract: Identifying stars formed in pristine environments (Pop III) within the first billion years is vital to uncovering the earliest growth and chemical evolution of galaxies. Pop III galaxies, however, are typically expected to be too faint and too few in number to be detectable by forthcoming instruments without extremely long integration times and/or extreme lensing. In an environment, however, where star formation is suppressed until a halo crosses the atomic cooling limit (e.g., by a modest Lyman-Werner flux, high baryonic streaming velocities, and/or dynamical heating effects),primordial halos can form substantially more numerous and more massive stars. Some of these stars will in-turn be accreting more rapidly than they can thermally relax at any given time. Using high resolution cosmological zoom-in simulations of massive star formation in high-z halos, we find that such rapidly accreting stars produce prominent spectral features which would be detectable by {\it JWST}. The rapid accretion episodes within the halo lead to stochastic reprocessing of 0--20\% of the total stellar emission into the rest-frame optical over long timescales, a unique signature which may allow deep observations to identify such objects out to $z \sim 10-13$ using mid- and wide-band NIRCam colors alone.
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TL;DR: In this paper , the radio-loud quasar SDSS J0836+0054 at z = 5.8 could be part of a surprisingly rich structure of galaxies.
Abstract: Abstract Observations of luminous quasars and their supermassive black holes at z ≳ 6 suggest that they formed at dense matter peaks in the early universe. However, few studies have found definitive evidence that the quasars lie at cosmic density peaks, in clear contrast with theory predictions. Here we present new evidence that the radio-loud quasar SDSS J0836+0054 at z = 5.8 could be part of a surprisingly rich structure of galaxies. This conclusion is reached by combining a number of findings previously reported in the literature. Bosman et al. obtained the redshifts of three companion galaxies, confirming an overdensity of i 775 dropouts found by Zheng et al. By comparing this structure with those found near other quasars and large overdense regions in the field at z ∼ 6–7, we show that the SDSS J0836+0054 field is among the densest structures known at these redshifts. One of the spectroscopic companions is a very massive star-forming galaxy ( log 10 ( ⋆ / M ⊙ ) = 10.3 − 0.2 + 0.3 ) based on its unambiguous detection in a Spitzer 3.6 μ m image. This suggests that the quasar field hosts not one, but at least two rare, massive dark matter halos ( log 10 ( h / M ⊙ ) ≳ 12 ), corresponding to a galaxy overdensity of at least 20. We discuss the properties of the young radio source. We conclude that the environment of SDSS J0836+0054 resembles, at least qualitatively, the type of conditions that may have spurred the direct collapse of a massive black hole seed according to recent theory.
4 citations
TL;DR: In this article , the authors examined stars with mass just below the general relativistic instability supernova mass range and found that the lower mass pulsating models are even brighter than the higher mass supernovae because the pulsations occur in the late helium burning phase when the stars have extremely large radii.
Abstract: The origin of high-redshift quasars and their supermassive black hole engines is unclear. One promising solution is the collapse of a primordial supermassive star. Observational confirmation of this scenario may be challenging, but a general relativistic instability supernova provides one avenue for such. Previous studies have found that a general relativistic instability supernova has a potentially decades-long plateau phase visible to JWST at high redshift. In this work, we examine stars with mass just below the general relativistic instability supernova mass range. These stars pulsate, ejecting a portion of their envelopes. They then contract quasi-statically back to an equilibrium temperature, at which point they again become unstable and pulsate once more. Because each pulse consumes a small amount of the available nuclear fuel, there exists the possibility of multiple pulsations. We present simulations of the contracting phase, the pulsation, and the light-curve phase. We find that the lower mass pulsating models are even brighter than the higher mass supernovae because the pulsations occur in the late helium burning phase when the stars have extremely large radii. The fact that the pulsations are more luminous and occur in a wider mass range than the supernovae bodes well for observation.
3 citations
TL;DR: In this article , an accurate model of the Lyman-Werner (LW) radiation field at z ≥ 6, by post-processing the physics-rich high-resolution FiBY simulation, is presented.
Abstract:
The Lyman-Werner (LW) radiation field is a key ingredient in the chemo-thermal evolution of gas in the Early Universe, as it dissociates H2 molecules, the primary cooling channel in an environment devoid of metals and dust. Despite its important role, it is still not implemented in cosmological simulations on a regular basis, in contrast to the ionising UV background. This is in part due to uncertainty in the source modelling, their spectra and abundance, as well as the detailed physics involved in the propagation of the photons and their interactions with the molecules. The goal of this work is to produce an accurate model of the LW radiation field at z ≥ 6, by post-processing the physics-rich high-resolution FiBY simulation. Our novelties include updated cross sections for H2, $\rm {H^-}$ and $\rm {H^+_2}$ chemical species, IGM absorption by neutral Hydrogen and various spectral models for Population III and Population II stars. With our fiducial set of parameters, we show that the mean LW intensity steadily increases by three orders of magnitude from z ∼ 23 to z ∼ 6, while spatial inhomogeneities originate from massive star-forming galaxies that dominate the photon budget up to a distance of ∼100 proper kpc. Our model can be easily applied to other simulations or semi-analytical models as an external radiation field that regulates the formation of stars and massive black hole seeds in high-z low-mass halos.
TL;DR: In this paper , the authors use the explicit gas dynamics code PPMstar to simulate the hydrogen-burning core of a 104m-M supermassive main-sequence star and conclude that the radiation pressure-dominated nature of the interior does not noticeably affect the behaviour of convection compared to the case of core convection in a massive main-sequential star where gas pressure dominates.
Abstract:
Supermassive stars are Population III stars with masses exceeding 104 M⊙ that could be the progenitors of the first supermassive black holes. Their interiors are in a regime where radiation pressure dominates the equation of state. In this work, we use the explicit gas dynamics code PPMstar to simulate the hydrogen-burning core of a 104 M⊙ supermassive main-sequence star. These are the first 3D hydrodynamics simulations of core convection in supermassive stars. We perform a series of ten simulations at different heating rates and on Cartesian grids with resolutions of 7683, 11523 and 17283. We examine different properties of the convective flow, including its large-scale morphology, its velocity spectrum and its mixing properties. We conclude that the radiation pressure-dominated nature of the interior does not noticeably affect the behaviour of convection compared to the case of core convection in a massive main-sequence star where gas pressure dominates. Our simulations also offer support for the use of mixing-length theory in 1D models of supermassive stars.
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TL;DR: In this paper, the authors present the first cosmological results based on Planck measurements of the cosmic microwave background (CMB) temperature and lensing-potential power spectra, which are extremely well described by the standard spatially-flat six-parameter ΛCDM cosmology with a power-law spectrum of adiabatic scalar perturbations.
Abstract: This paper presents the first cosmological results based on Planck measurements of the cosmic microwave background (CMB) temperature and lensing-potential power spectra. We find that the Planck spectra at high multipoles (l ≳ 40) are extremely well described by the standard spatially-flat six-parameter ΛCDM cosmology with a power-law spectrum of adiabatic scalar perturbations. Within the context of this cosmology, the Planck data determine the cosmological parameters to high precision: the angular size of the sound horizon at recombination, the physical densities of baryons and cold dark matter, and the scalar spectral index are estimated to be θ∗ = (1.04147 ± 0.00062) × 10-2, Ωbh2 = 0.02205 ± 0.00028, Ωch2 = 0.1199 ± 0.0027, and ns = 0.9603 ± 0.0073, respectively(note that in this abstract we quote 68% errors on measured parameters and 95% upper limits on other parameters). For this cosmology, we find a low value of the Hubble constant, H0 = (67.3 ± 1.2) km s-1 Mpc-1, and a high value of the matter density parameter, Ωm = 0.315 ± 0.017. These values are in tension with recent direct measurements of H0 and the magnitude-redshift relation for Type Ia supernovae, but are in excellent agreement with geometrical constraints from baryon acoustic oscillation (BAO) surveys. Including curvature, we find that the Universe is consistent with spatial flatness to percent level precision using Planck CMB data alone. We use high-resolution CMB data together with Planck to provide greater control on extragalactic foreground components in an investigation of extensions to the six-parameter ΛCDM model. We present selected results from a large grid of cosmological models, using a range of additional astrophysical data sets in addition to Planck and high-resolution CMB data. None of these models are favoured over the standard six-parameter ΛCDM cosmology. The deviation of the scalar spectral index from unity isinsensitive to the addition of tensor modes and to changes in the matter content of the Universe. We find an upper limit of r0.002< 0.11 on the tensor-to-scalar ratio. There is no evidence for additional neutrino-like relativistic particles beyond the three families of neutrinos in the standard model. Using BAO and CMB data, we find Neff = 3.30 ± 0.27 for the effective number of relativistic degrees of freedom, and an upper limit of 0.23 eV for the sum of neutrino masses. Our results are in excellent agreement with big bang nucleosynthesis and the standard value of Neff = 3.046. We find no evidence for dynamical dark energy; using BAO and CMB data, the dark energy equation of state parameter is constrained to be w = -1.13-0.10+0.13. We also use the Planck data to set limits on a possible variation of the fine-structure constant, dark matter annihilation and primordial magnetic fields. Despite the success of the six-parameter ΛCDM model in describing the Planck data at high multipoles, we note that this cosmology does not provide a good fit to the temperature power spectrum at low multipoles. The unusual shape of the spectrum in the multipole range 20 ≲ l ≲ 40 was seen previously in the WMAP data and is a real feature of the primordial CMB anisotropies. The poor fit to the spectrum at low multipoles is not of decisive significance, but is an “anomaly” in an otherwise self-consistent analysis of the Planck temperature data.
7,060 citations
TL;DR: In this paper, the authors present the first results based on Planck measurements of the CMB temperature and lensing-potential power spectra, which are extremely well described by the standard spatially-flat six-parameter LCDM cosmology.
Abstract: We present the first results based on Planck measurements of the CMB temperature and lensing-potential power spectra. The Planck spectra at high multipoles are extremely well described by the standard spatially-flat six-parameter LCDM cosmology. In this model Planck data determine the cosmological parameters to high precision. We find a low value of the Hubble constant, H0=67.3+/-1.2 km/s/Mpc and a high value of the matter density parameter, Omega_m=0.315+/-0.017 (+/-1 sigma errors) in excellent agreement with constraints from baryon acoustic oscillation (BAO) surveys. Including curvature, we find that the Universe is consistent with spatial flatness to percent-level precision using Planck CMB data alone. We present results from an analysis of extensions to the standard cosmology, using astrophysical data sets in addition to Planck and high-resolution CMB data. None of these models are favoured significantly over standard LCDM. The deviation of the scalar spectral index from unity is insensitive to the addition of tensor modes and to changes in the matter content of the Universe. We find a 95% upper limit of r<0.11 on the tensor-to-scalar ratio. There is no evidence for additional neutrino-like relativistic particles. Using BAO and CMB data, we find N_eff=3.30+/-0.27 for the effective number of relativistic degrees of freedom, and an upper limit of 0.23 eV for the summed neutrino mass. Our results are in excellent agreement with big bang nucleosynthesis and the standard value of N_eff=3.046. We find no evidence for dynamical dark energy. Despite the success of the standard LCDM model, this cosmology does not provide a good fit to the CMB power spectrum at low multipoles, as noted previously by the WMAP team. While not of decisive significance, this is an anomaly in an otherwise self-consistent analysis of the Planck temperature data.
6,201 citations
TL;DR: In this article, a comparison of plane-parallel non-LTE model atmospheres and comoving frame calculations is presented for massive Population III stars and stellar populations based on a recent stellar evolution tracks and up-to-date evolutionary synthesis models, with the aim to study their spectral properties, including their dependence on age, star formation history, and IMF.
Abstract: We present realistic models for massive Population III stars and stellar populations based on non-LTE model atmospheres, recent stellar evolution tracks and up-to-date evolutionary synthesis models, with the aim to study their spectral properties, including their dependence on age, star formation history, and IMF. A comparison of plane parallel non-LTE model atmospheres and comoving frame calculations shows that even in the presence of some putative weak mass loss, the ionising spectra of metal-free populations differ little or negligibly from those obtained using plane parallel non-LTE models. As already discussed by Tumlinson & Shull ([CITE]), the main salient property of Pop III stars is their increased ionising flux, especially in the He+ continuum (>54 eV). The main result obtained for individual Pop III stars is the following: due to their redward evolution off the zero age main sequence (ZAMS) the spectral hardness measured by the He/H ionising flux is decreased by a factor ~2 when averaged over their lifetime. If such stars would suffer strong mass loss, their spectral appearance could, however, remain similar to that of their ZAMS position. The main results regarding integrated stellar populations are: – for young bursts and the case of a constant SFR, nebular continuous emission – neglected in previous studies – dominates the spectrum redward of Lyman-α if the escape fraction of ionising photons out of the considered region is small or negligible. In consequence predicted emission line equivalent widths are considerably smaller than found in earlier studies, whereas the detection of the continuum is eased. Nebular line and continuous emission strongly affect the broad band photometric properties of Pop III objects; – due to the redward stellar evolution and short lifetimes of the most massive stars, the hardness of the ionising spectrum decreases rapidly, leading to the disappearance of the characteristic He ii recombination lines after ~3 Myr in instantaneous bursts; – He ii λ 1640, Hα (and other) line luminosities usable as indicators of the star formation rate are given for the case of a constant SFR. For obvious reasons such indicators depend strongly on the IMF; – due to an increased photon production and reduced metal yields, the relative efficiency of ionising photon energy to heavy element rest mass production, η , of metal-poor and metal-free populations is increased by factors of ~4 to 18 with respect to solar metallicity and for “standard” IMFs; – the lowest values of 1.6–2.2% are obtained for IMFs exclusively populated with high mass stars (). If correct, the yields dominated by pair creation SNae then predict large overabundances of O/C and Si/C compared to solar abundance ratios. Detailed results are given in tabular form and as fit formulae for easy implementation in other calculations. The predicted spectra will be used to study the detectability of Pop III galaxies and to derive optimal search strategies for such objects.
854 citations
TL;DR: In this article, the minimum mass that a virialized gas cloud must have in order to be able to cool in a Hubble time is computed, using a detailed treatment of the chemistry of molecular hydrogen.
Abstract: The minimum mass that a virialized gas cloud must have in order to be able to cool in a Hubble time is computed, using a detailed treatment of the chemistry of molecular hydrogen. With a simple model for halo profiles, we reduce the problem to that of numerically integrating a system of chemical equations. The results agree well with numerically expensive three-dimensional simulations, and our approach has the advantage of being able to explore large regions of parameter space rapidly. The minimum baryonic mass Mb is found to be strongly redshift dependent, dropping from 106 M☉ at z ~ 15 to 5 × 103 M☉ at z ~ 100 as molecular cooling becomes effective. For z 100, Mb rises again, as cosmic microwave background photons inhibit H2 formation through the H- channel. Finally, for z 200, the H -->+2 channel for H2 formation becomes effective, driving Mb down toward Mb ~ 103 M☉. With a standard cold dark matter power spectrum with σ8 = 0.7, this implies that a fraction 10-3 of all baryons may have formed luminous objects by z = 30, which could be sufficient to reheat the universe.
814 citations
TL;DR: In this paper, the physical conditions under which supermassive black holes could have formed inside the first galaxies were considered and smoothed particle hydrodynamics simulations indicate that metal-free galaxies with a virial temperature of ~104 K and suppressed H2 formation (due to an intergalactic UV background) tend to form a binary black hole system that contains a substantial fraction of the total baryonic mass of the host galaxy.
Abstract: We consider the physical conditions under which supermassive black holes could have formed inside the first galaxies. Our smoothed particle hydrodynamics simulations indicate that metal-free galaxies with a virial temperature of ~104 K and suppressed H2 formation (due to an intergalactic UV background) tend to form a binary black hole system that contains a substantial fraction (10%) of the total baryonic mass of the host galaxy. Fragmentation into stars is suppressed without substantial H2 cooling. Our simulations follow the condensation of ~5 × 106 M☉ around the two centers of the binary down to a scale of 0.1 pc. Low-spin galaxies form a single black hole instead. These early black holes lead to quasar activity before the epoch of reionization. Primordial black hole binaries lead to gravitational radiation emission at redshifts z 10 that would be detectable by Laser Interferometer Space Antenna.
691 citations