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Register a new userThe Impact of Black Hole Formation on Population Averaged Supernova Yields
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The landscape of black hole (BH) formation -- which massive stars explode as core-collapse supernovae (CCSN) and which implode to BHs -- profoundly affects the IMF-averaged nucleosynthetic yields of a stellar population. Building on the work of Sukhbold et al. (2016), we compute IMF-averaged yields at solar metallicity for a wide range of assumptions, including neutrino-driven engine models with extensive BH formation, models with a simple mass threshold for BH formation, and a model in which all stars from $8-120 text{M}_{odot}$ explode. For plausible choices, the overall yields of $alpha$-elements span a factor of three, but changes in relative yields are more subtle, typically $0.05-0.2$ dex. For constraining the overall level of BH formation, ratios of C and N to O or Mg are promising diagnostics. For distinguishing complex, theoretically motivated landscapes from simple mass thresholds, abundance ratios involving Mn or Ni are promising because of their sensitivity to the core structure of the CCSN progenitors. We confirm previous findings of a substantial (factor $2.5-4$) discrepancy between predicted O/Mg yield ratios and observationally inferred values, implying that models either overproduce O or underproduce Mg. No landscape choice achieves across-the-board agreement with observed abundance ratios; the discrepancies offer empirical clues to aspects of massive star evolution or explosion physics still missing from the models. We find qualitatively similar results using the massive star yields of Limongi & Chieffi (2018). We provide tables of IMF-integrated yields for several landscape scenarios, and more flexible user-designed models can be implemented through the publicly available $texttt{Versatile Integrator for Chemical Evolution}$ ($texttt{VICE}$; https://pypi.org/project/vice/).
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Observations of quasars at $ z > 6$ suggest the presence of black holes with a few times $rm 10^9 ~M_{odot}$. Numerous models have been proposed to explain their existence including the direct collapse which provides massive seeds of $rm 10^5~M_{odot}$. The isothermal direct collapse requires a strong Lyman-Werner flux to quench $rm H_2$ formation in massive primordial halos. In this study, we explore the impact of trace amounts of metals and dust enrichment. We perform three dimensional cosmological simulations for two halos of $rm > 10^7~M_{odot}$ with $rm Z/Z_{odot}= 10^{-4}-10^{-6}$ illuminated by an intense Lyman Werner flux of $rm J_{21}=10^5$. Our results show that initially the collapse proceeds isothermally with $rm T sim 8000$ K but dust cooling becomes effective at densities of $rm 10^{8}-10^{12} ~cm^{-3}$ and brings the gas temperature down to a few 100-1000 K for $rm Z/Z_{odot} geq 10^{-6}$. No gravitationally bound clumps are found in $rm Z/Z_{odot} leq 10^{-5}$ cases by the end of our simulations in contrast to the case with $rm Z/Z_{odot} = 10^{-4}$. Large inflow rates of $rm geq 0.1~M_{odot}/yr$ are observed for $rm Z/Z_{odot} leq 10^{-5}$ similar to a zero-metallicity case while for $rm Z/Z_{odot} = 10^{-4}$ the inflow rate starts to decline earlier due to the dust cooling and fragmentation. For given large inflow rates a central star of $rm sim 10^4~M_{odot}$ may form for $rm Z/Z_{odot} leq 10^{-5}$.
Supernovae (SNe) are considered to have a major role in dust enrichment of high redshift galaxies and, due to the short lifetimes of interstellar grains, in dust replenishment of local galaxies. Here we explore how SN dust yields depend on the mass, metallicity, and rotation rate of the progenitor stars, and on the properties of the explosion. To this aim, assuming uniform mixing inside the ejecta, we quantify the dust mass produced by a sample of SN models with progenitor masses $13~M_{odot} leq M leq 120~M_{odot}$, metallicity $rm -3 leq [Fe/H] leq 0$, rotation rate $rm v_{rm rot} = 0$ and $300$~km/s, that explode with a fixed energy of $1.2 times 10^{51}$~erg (FE models) or with explosion properties calibrated to reproduce the $rm ^{56}Ni$ - $M$ relation inferred from SN observations (CE models). We find that rotation favours more efficient dust production, particularly for more massive, low metallicity stars, but that metallicity and explosion properties have the largest effects on the dust mass and its composition. In FE models, SNe with $M leq 20 - 25 ~M_{odot}$ are more efficient at forming dust: between 0.1 and 1 $M_odot$ is formed in a single explosion, with a composition dominated by silicates, carbon and magnetite grains when $rm [Fe/H] = 0$, and by carbon and magnetite grains when $rm [Fe/H] < 0$. In CE models, the ejecta are massive and metal-rich and dust production is more efficient. The dust mass increases with $M$ and it is dominated by silicates, at all [Fe/H].
The failed supernova N6946-BH1 likely formed a black hole (BH); we age-date the surrounding population and infer an age and initial mass for the progenitor of this BH formation candidate. First, we use archival Hubble Space Telescope imaging to extract broadband photometry of the resolved stellar populations surrounding this event. Using this photometry, we fit stellar evolution models to the color-magnitude diagrams to measure the recent star formation history (SFH). Modeling the photometry requires an accurate distance; therefore, we measure the tip of the red giant branch (TRGB) and infer a distance modulus of $29.47 pm 0.079$ to NGC~6946, or a metric distance of $7.83 pm 0.29$ Mpc. To estimate the stellar populations age, we convert the SFH and uncertainties into a probabilistic distribution for the progenitors age. The region in the immediate vicinity of N6946-BH1 exhibits the youngest and most vigorous star formation for several hundred pc. This suggests that the progenitor is not a runaway star. From these measurements, we infer an age for the BH progenitor of $10.6^{+14.5}_{-5.9}$ Myr. Assuming that the progenitor evolved effectively as a single star, this corresponds to an initial mass of $17.9^{+29.9}_{-7.6}$ $M_{odot}$. Previous spectral energy distribution (SED) modeling of the progenitor suggests a mass of $sim$27 $M_{odot}$. Formally, the SED-derived mass falls within our narrowest 68% confidence interval; however, $91%$ of the probability distribtuion function we measure lies below that mass, putting some tension between the age and the direct-imaging results.
Fallback in core-collapse supernovae is considered a major ingredient for explaining abundance anomalies in metal-poor stars and the natal kicks and spins of black holes (BHs). We present a first 3D simulation of BH formation and fallback in an aborted neutrino-driven explosion of a $40$ solar mass zero-metallicity progenitor from collapse to shock breakout. We follow the phase up to BH formation using the relativistic CoCoNuT-FMT code. For the subsequent evolution to shock breakout we apply the moving-mesh code Arepo to core-collapse supernovae for the first time. Our simulation shows that despite early BH formation, neutrino-heated bubbles can survive for tens of seconds before being accreted, leaving them sufficient time to transfer part of their energy to sustain the shock wave as is propagates through the envelope. Although the initial net energy ($sim 2$ Bethe) of the neutrino-heated ejecta barely equals the binding energy of the envelope, $11,mathrm{M}_odot$ of hydrogen are still expelled with an energy of $0.23$ Bethe. We find no significant mixing and only a modest BH kick and spin, but speculate that stronger effects could occur for slightly more energetic explosions or progenitors with less tightly bound envelopes.
We perform a binary population synthesis calculation incorporating very massive population (Pop.) III stars up to 1500 $M_odot$, and investigate the nature of binary black hole (BBH) mergers. Above the pair-instability mass gap, we find that the typical primary black hole (BH) mass is 135-340 $M_odot$. The maximum primary BH mass is as massive as 686 $M_odot$. The BBHs with both of their components above the mass gap have low effective inspiral spin $sim$ 0. So far, no conclusive BBH merger beyond the mass gap has been detected, and the upper limit on the merger rate density is obtained. If the initial mass function (IMF) of Pop. III stars is simply expressed as $xi_m(m) propto m^{-alpha}$ (single power law), we find that $alpha gtrsim 2.8$ is needed in order for the merger rate density not to exceed the upper limit. In the future, the gravitational wave detectors such as Einstein telescope and Pre-DECIGO will observe BBH mergers at high redshift. We suggest that we may be able to impose a stringent limit on the Pop. III IMF by comparing the merger rate density obtained from future observations with that derived theoretically.
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