Progenitor Mass Research Articles

Seimei/KOOLS-IFU mapping of the gas and dust distributions in Galactic PNe: Unveiling the origin and evolution of the Galactic halo PN H4-1

Abstract H4-1 is a planetary nebula (PN) located in the Galactic halo, and is notably carbon-rich and one of the most metal-deficient PNe in the Milky Way. To unveil its progenitor evolution through accurate measurement of the gas mass, we conducted a comprehensive investigation of H4-1, using the newly obtained Seimei/KOOLS-IFU spectra and multiwavelength spectro-photometry data. The emission-line images generated from the KOOLS-IFU data cube successfully resolve the ellipsoidal nebula and the equatorial flattened disk that are frequently seen in bipolar PNe evolved from massive progenitors. By a fully data-driven method, we directly derived the seven elemental abundances, the gas-to-dust mass ratio, and the gas and dust masses based on our own distance scale. By comparing the observed quantities with both the photoionization model and the binary nucleosynthesis model, we conclude that the progenitors of initial masses of 1.87 M$_{\odot }$ and 0.82 M$_{\odot }$ are second-generation stars formed ∼4 Gyr after the Big Bang that have undergone mass transfers and a binary merger, and have ultimately evolved into a PN showing unique chemical abundances. Our binary model successfully reproduces the observed abundances and also explains the evolutionary time scale of H4-1.

Dust from evolved stars: a pilot analysis of the AGB to PN transition

ABSTRACT We present a novel approach to address dust production by low- and intermediate-mass stars. We study the asymptotic giant branch (AGB) phase, during which the formation of dust takes place, from the perspective of post-AGB and planetary nebula (PN) evolutionary stage. Using results from stellar evolution and dust formation modelling, we interpret the spectral energy distribution of carbon-dust-rich sources currently evolving through different evolutionary phases, believed to descend from progenitors of similar mass and chemical composition. Comparing the results of different stages along the AGB to PNe transition, we can provide distinct insights on the amount of dust and gas released during the very late AGB phases. While the post-AGB traces the history of dust production back to the tip of the AGB phase, investigating the PNe is important to reconstruct the mass-loss process experienced after the last thermal pulse. The dust surrounding the post-AGB was formed soon after the tip of the AGB. The PNe dust-to-gas ratio is ∼10−3, 2.5 times smaller than what expected for the same initial mass star during the last AGB interpulse, possibly suggesting that dust might be destroyed during the PN phase. Measuring the amount of dust present in the nebula can constrain the capacity of the dust to survive the central star heating.

Study on the X-Ray Re-brightening Signature of GRB 220117A

The Swift/XRT detected the X-ray afterglow of long burst GRB 220117A, which began to rebrighten 300 s after triggering and followed a single power-law decay segment after thousands of seconds of the orbital observation gap. This segment is different from the shallow decay segment (plateau) and flare, and may belong to a giant X-ray bump. We investigated this segment by the fall-back accretion model and found that the model can interpret this segment with reasonable parameter values. Within this physical model scenario, the fall-back accretion rate reaches a peak value ∼1.70 × 10−5 M ⊙ s−1 around 300 s in the central engine frame, which is compatible with the late mass supply rate of some low-metallicity massive progenitor stars. The initial black hole (BH) spin is and implies that this re-brightening signature requires a larger BH spin. The total accretion mass during the fall-back process is M acc = (3.09 ± 0.02) × 10−2 M ⊙. The jet energy from the fall-back accretion is (9.77 ± 0.65) × 1052 erg, with a ratio of 0.066 to the isotropic-equivalent radiation energies of the GRB prompt phase in the 1–104 keV band. The fall-back radius r p corresponding to the peak time of fall-back t p is (3.16 ± 0.05) × 1010 cm, which is consistent with the typical radius of Wolf–Rayet stars. In summary, our results provide additional support for the origin of the long burst from the core collapse of Wolf–Rayet stars, and its late central engine activity is likely due to the fall-back accretion process.

Rapidly rotating massive Population III stars: a solution for high carbon enrichment in CEMP-no stars

ABSTRACT Very metal-poor stars that have [Fe/H] < −2 and that are enhanced in C relative to Fe ([C/Fe] > +0.7) but have no enhancement of heavy elements ([Ba/Fe] < 0) are known as carbon-enhanced metal-poor (CEMP-no) stars. These stars are thought to be produced from a gas that was polluted by the supernova (SN) ejecta of the very first generation (Population III) massive stars. The very high enrichment of C (A(C) ≳ 6) observed in many of the CEMP-no stars is difficult to explain by current models of SN explosions from massive Population III stars when a reasonable dilution of the SN ejecta, which is consistent with detailed simulation of metal mixing in minihaloes, is adopted. We explore rapidly rotating Population III stars that undergo efficient mixing and reach a quasi-chemically homogeneous (QCH) state. We find that QCH stars can eject large amounts of C in the wind and that the resulting dilution of the wind ejecta in the interstellar medium can lead to a C enrichment of A(C) ≲ 7.75. The core of QCH stars can produce up to an order of magnitude of more C than non-rotating progenitors of similar mass and the resulting SN can lead to a C enrichment of A(C) ≲ 7. Our rapidly rotating massive Population III stars cover almost the entire range of A(C) observed in CEMP-no stars and are a promising site for explaining the high C enhancement in the early Galaxy. Our work indicates that a substantial fraction of Population III stars were likely rapid rotators.

A population of Type Ibc supernovae with massive progenitors

If high-mass stars (≳20 − 25 M⊙) are the progenitors of stripped-envelope (SE) supernovae (SNe), their massive ejecta should lead to broad, long-duration lightcurves. Instead, literature samples of SE SNe have reported relatively narrow lightcurves corresponding to ejecta masses between 1 − 4 M⊙ that favor intermediate-mass progenitors (≲20 − 25 M⊙). Working with an untargeted sample from a single telescope to better constrain their rates, we searched the Palomar Transient Factory (PTF) and intermediate-PTF (iPTF) sample of SNe for SE SNe with broad lightcurves. Using a simple observational marker of g- or r-band lightcurve stretch compared to a template to measure broadness, we identified eight significantly broader Type Ibc SNe after applying quantitative sample selection criteria. The lightcurves, broad-band colors, and spectra of these SNe are found to evolve more slowly relative to typical Type Ibc SNe, proportional with the stretch parameter. Bolometric lightcurve modeling and their nebular spectra indicate high ejecta masses and nickel masses, assuming radioactive decay powering. Additionally, these objects are preferentially located in low-metallicity host galaxies with high star formation rates, which may account for their massive progenitors, as well as their relative absence from the literature. Our study thus supports the link between broad lightcurves (as measured by stretch) and high-mass progenitor stars in SE SNe with independent evidence from bolometric lightcurve modeling, nebular spectra, host environment properties, and photometric evolution. In the first systematic search of its kind using an untargeted sample, we used the stretch distribution to identify a higher than previously appreciated fraction of SE SNe with broad lightcurves (∼13%). Correcting for Malmquist and lightcurve duration observational biases, we conservatively estimate that a minimum of ∼6% of SE SNe are consistent with high-mass progenitors. This result has implications for the progenitor channels of SE SNe, including late stages of massive stellar evolution, the origin of the observed oxygen fraction in the universe, and formation channels for stellar-mass black holes.

Estimating Ejecta Masses of Stripped-envelope Supernovae Using Late-time Light Curves

Stripped-envelope supernovae (SESNe) are a subclass of core-collapse supernovae that are deficient in hydrogen (SN IIb, SN Ib) and possibly helium (SN Ic) in their spectra. Their progenitors are likely stripped of this material through a combination of stellar winds and interactions with a close binary companion, but the exact ejecta mass range covered by each subtype and how it relates to the zero-age main-sequence progenitor mass is still unclear. Using a combination of semianalytic modeling and numerical simulations, we discuss how the properties of SESN progenitors can be constrained through different phases of the bolometric light curve. We find that the light-curve rise time is strongly impacted by the strength of radioactive nickel mixing and treatment of helium recombination. These can vary between events and are often not accounted for in simpler modeling approaches, leading to large uncertainties in ejecta masses inferred from the rise. Motivated by this, we focus on the late-time slope, which is determined by gamma-ray leakage. We calibrate the relationship between ejecta mass, explosion energy, and gamma-ray escape time T 0 using a suite of numerical models. Application of the fitting function we provide to bolometric light curves of SESNe should result in ejecta masses with approximately 20% uncertainty. With large samples of SESNe coming from current and upcoming surveys, our methods can be utilized to better understand the diversity and origin of the progenitor stars.

Uncovering new white dwarf–open cluster associations using Gaia DR3

Context. Open clusters (OCs) provide homogeneous samples of white dwarfs (WDs) with known distances, extinctions, and total ages. The unprecedented astrometric precision of Gaia allows us to identify many novel OC–WD pairs. Studying WDs in the context of their parent OCs makes it possible to determine the properties of WD progenitors and study the initial–final mass relation (IFMR). Aims. We seek to find potential new WD members of OCs in the solar vicinity. The analysis of OC members’ parallaxes allows us to determine the OC distances to a high precision, which in turn enables us to calculate WD masses and cooling ages and to constrain the IFMR. Methods. We searched for new potential WD members of nearby OCs using the density-based machine learning clustering algorithm HDBSCAN. The clustering analysis was applied in five astrometric dimensions – positions in the sky, proper motions and parallaxes, and in three dimensions where the positional information was not considered in the clustering analysis. The identified candidate OC WDs were further filtered using the photometric criteria and properties of their putative host OCs. The masses and cooling ages of the WDs were calculated via a photometric method using all available Gaia, Pan-STARRS, SDSS, and GALEX photometry. The WD progenitor masses were determined using the ages and metallicities of their host OCs. Results. Altogether, 63 OC WD candidates were recovered, 27 of which are already known in the literature. We provide characterization for 36 novel WDs that have significant OC membership probabilities. Six of them fall into relatively unconstrained sections of the IFMR where the relation seems to exhibit nonlinear behavior. We were not able to identify any WDs originating from massive progenitors that would even remotely approach the widely adopted WD progenitor mass limit of 8 M⊙; this confirms the paucity of such objects residing in OCs and hints at a presence of velocity kicks for nascent WDs.

Circumstellar material ejected violently by a massive star immediately before its death

Type II supernovae represent the most common stellar explosions in the Universe, for which the final stage evolution of their hydrogen-rich massive progenitors towards core-collapse explosion are elusive. The recent explosion of SN 2023ixf in a very nearby galaxy, Messier 101, provides a rare opportunity to explore this longstanding issue. With the timely high-cadence flash spectra taken within 1–5 days after the explosion, we can put stringent constraints on the properties of the surrounding circumstellar material around this supernova. Based on the rapid fading of the narrow emission lines and luminosity/profile of Hα emission at very early times, we estimate that the progenitor of SN 2023ixf lost material at a mass-loss rate Ṁ≈6×10-4M⊙a-1 over the last 2–3 years before explosion. This close-by material, moving at a velocity vw≈55kms-1, accumulates a compact CSM shell at the radius smaller than 7×1014 cm from the progenitor. Given the high mass-loss rate and relatively large wind velocity presented here, together with the pre-explosion observations made about two decades ago, the progenitor of SN 2023ixf could be a short-lived yellow hypergiant that evolved from a red supergiant shortly before the explosion.

Stars, Gas, and Star Formation of Distant Post-starburst Galaxies

We present a comprehensive multiwavelength study of five post-starburst galaxies with M * > 1011 M ⊙ at z ∼ 0.7, examining their stars, gas, and current and past star formation activities. Using optical images from the Subaru Telescope and Hubble Space Telescope, we observe a high incidence of companion galaxies and low surface brightness tidal features, indicating that quenching is closely related to interactions between galaxies. From optical spectra provided by the LEGA-C survey, we model the stellar continuum to derive the star formation histories and show the stellar masses of progenitors ranging from 2 × 109 M ⊙ to 1011 M ⊙, undergoing a burst of star formation several hundred million years prior to observation, with a decay timescale of ∼100 Myr. Our Atacama Large Millimeter/submillimeter Array observations detect CO(2-1) emission in four galaxies, with the molecular gas spreading over up to >1″, or ∼10 kpc, with a mass of up to ∼2 × 1010 M ⊙. However, star-forming regions are unresolved by either the slit spectra or 3 GHz continuum observed by the Very Large Array. Comparisons between the star formation rates (SFRs) and gas masses, and the sizes of CO emission and star-forming regions suggest a low star-forming efficiency. We show that the SFRs derived from IR and radio luminosities with commonly used calibrations tend to overestimate the true values because of the prodigious amount of radiation from old stars and the contribution from active galactic nuclei (AGNs), as the optical spectra reveal weak AGN-driven outflows.

Luminous Radio Emission from the Superluminous Supernova 2017ens at 3.3 yr after Explosion

We present the results from a multiyear radio campaign of the superluminous supernova (SLSN) SN 2017ens, which yielded the earliest radio detection of an SLSN to date at the age of ∼3.3 yr after explosion. SN 2017ens was not detected at radio frequencies in the first ∼300 days but reached L ν ≈ 1028 erg s−1 cm−2 Hz−1 at ν ∼ 6 GHz, ∼1250 days post explosion. Interpreting the radio observations in the context of synchrotron radiation from the supernova shock interaction with the circumstellar medium (CSM), we infer an effective mass-loss rate at r ∼ 1017 cm from the explosion’s site, for a wind speed of v w = 50–60 km s−1 as measured from optical spectra. These findings are consistent with the spectroscopic metamorphosis of SN 2017ens from hydrogen poor to hydrogen rich ∼190 days after explosion reported by Chen et al. SN 2017ens is thus an addition to the sample of hydrogen-poor massive progenitors that explode shortly after having lost their hydrogen envelope. The inferred circumstellar densities, implying a CSM mass up to ∼0.5 M ☉, and low velocity of the ejection suggest that binary interactions (in the form of common-envelope evolution and subsequent envelope ejection) play a role in shaping the evolution of the stellar progenitors of SLSNe in the ≲500 yr preceding core collapse.

Gravitational Wave Eigenfrequencies from Neutrino-driven Core-collapse Supernovae

Core-collapse supernovae (CCSNe) are predicted to produce gravitational waves (GWs) that may be detectable by Advanced LIGO/Virgo. These GW signals carry information from the heart of these cataclysmic events, where matter reaches nuclear densities. Recent studies have shown that it may be possible to infer the properties of the proto-neutron star (PNS) via GWs generated by hydrodynamic perturbations of the PNS. However, we lack a comprehensive understanding of how these relationships may change with the properties of CCSNe. In this work, we build a self-consistent suite of over 1000 exploding CCSNe from a grid of progenitor masses and metallicities combined with six different nuclear equations of state (EOS). Performing a linear perturbation analysis on each model, we compute the resonant GW frequencies of the PNS, and we motivate a time-agnostic method for identifying characteristic frequencies of the dominant GW emission. From this, we identify two characteristic frequencies, of the early- and late-time signal, that measure the surface gravity of the cold remnant neutron star, and simultaneously constrain the hot nuclear EOS. However, we find that the details of the CCSN model, such as the treatment of gravity or the neutrino transport, and whether it explodes, noticeably change the magnitude and evolution of the PNS eigenfrequencies.

Progenitors and explosion properties of supernova remnants hosting central compact objects: II. A global systematic study with a comparison to nucleosynthesis models

ABSTRACT Core-collapse explosions of massive stars leave behind neutron stars, with a known diversity that includes the ‘Central Compact Objects’ (CCOs). Typified by the neutron star discovered near the centre of the Cas A supernova remnant (SNR), CCOs have been observed to shine only in X-rays. To address their supernova progenitors, we perform a systematic study of SNRs that contain a CCO and display X-ray emission from their shock-heated ejecta. We make use of X-ray data primarily using the Chandra X-ray observatory, complemented with XMM–Newton. This study uses a systematic approach to the analysis of each SNR aimed at addressing the supernova progenitor as well as the explosion properties (energy and ambient density). After fitting for the ejecta abundances estimated from a spatially resolved spectroscopic study, we compare the data to six nucleosynthesis models making predictions on supernova ejecta yields in core-collapse explosions. We find that the explosion models commonly used by the astrophysics community do not match the ejecta yields for any of the SNRs, suggesting additional physics, for example multidimensional explosion models or updated progenitor structures, are required. Overall we find low-mass (≤25 solar masses) progenitors among the massive stars population and low-energy explosions (<1051 ergs). We discuss degeneracies in our model fitting, particularly how altering the explosion energy affects the estimate of the progenitor mass. Our systematic study highlights the need for improving on the theoretical models for nucleosynthesis predictions as well as for sensitive, high-resolution spectroscopy observations to be acquired with next generation X-ray missions.

Neutrino-driven Winds in Three-dimensional Core-collapse Supernova Simulations

In this paper, we analyze the neutrino-driven winds that emerge in 12 unprecedentedly long-duration 3D core-collapse supernova simulations done using the code Fornax. The 12 models cover progenitors with zero-age main-sequence mass between 9 and 60 solar masses. In all our models, we see transonic outflows that are at least 2 times as fast as the surrounding ejecta and that originate generically from a proto−neutron star surface atmosphere that is turbulent and rotating. We find that winds are common features of 3D simulations, even if there is anisotropic early infall. We find that the basic dynamical properties of 3D winds behave qualitatively similarly to those inferred in the past using simpler 1D models, but that the shape of the emergent wind can be deformed, very aspherical, and channeled by its environment. The thermal properties of winds for less massive progenitors very approximately recapitulate the 1D stationary solutions, while for more massive progenitors they deviate significantly owing to aspherical accretion. The Y e temporal evolution in winds is stochastic, and there can be some neutron-rich phases. Though no strong r-process is seen in any model, a weak r-process can be produced, and isotopes up to 90Zr are synthesized in some models. Finally, we find that there is at most a few percent of a solar mass in the integrated wind component, while the energy carried by the wind itself can be as much as 10%–20% of the total explosion energy.

Modeling of the nebular-phase spectral evolution of stripped-envelope supernovae

We present an extended grid of multi-epoch 1D nonlocal thermodynamic equilibrium radiative transfer calculations for nebular-phase Type Ibc supernovae (SNe) from He-star explosions. Compared to our previous work, which was focused on a post-explosion epoch of 200 days, here we study the spectral evolution from 100 to about 450 days. We also augment the model set with progenitors that evolved without wind mass loss. Models with the same final, pre-SN mass have similar yields and produce essentially the same emergent spectra. Hence, the uncertain progenitor mass loss history compromises the inference of the initial, main sequence mass. This shortcoming does not affect Type IIb SNe in which mass-loss has left a small residual H-rich envelope in the progenitor star at core collapse and, hence, an intact He core. However, our 1D models with a different pre-SN mass tend to yield widely different spectra, as seen through variations in the strong emission lines due to [N II] λλ 6548, 6583, [O I] λλ 6300, 6364, [Ca II] λλ 7291, 7323, [Ni II] λ 7378, and the forest of Fe II lines below 5500 Å. At the lower mass end, the ejecta are He-rich, and at 100 days, they cool through He I, N II, Ca II, and Fe II lines, with N II and Fe II dominating at 450 days. These models, associated with He giants, stand in conflict to observed SNe Ib, which typically lack strong N II emission. Instead, they may lead to SNe Ibn or, because of additional stripping by a companion star, ultra-stripped SNe Ic. In contrast, for higher pre-SN masses, the ejecta are progressively He poor and cool at 100 days through O I, Ca II, and Fe II lines, with O I and Ca II dominating at 450 days. Non-uniform, aspherical, large-scale mixing is more likely to determine the SN type at intermediate pre-SN masses, rather than any compositional differences. Variations in clumping and mixing, as well as departures from spherical symmetry would increase the spectral diversity, but also introduce additional degeneracies. More robust predictions from spectral modeling thus require that careful attention be paid to the initial conditions by incorporating the salient features of physically consistent 3D explosion models.

Densities and mass assembly histories of the Milky Way satellites are not a challenge to ΛCDM

ABSTRACT We use the GRUMPY galaxy formation model based on a suite of zoom-in, high-resolution, dissipationless Λ Cold Dark Matter (ΛCDM) simulations of the Milky Way (MW) sized haloes to examine total matter density within the half-mass radius of stellar distribution, ρtot(< r1/2), of satellite dwarf galaxies around the MW hosts and their mass assembly histories. We compare model results to ρtot(< r1/2) estimates for observed dwarf satellites of the Milky Way spanning their entire luminosity range. We show that observed MW dwarf satellites exhibit a trend of decreasing total matter density within a half-mass radius, ρtot(< r1/2), with increasing stellar mass. This trend is in general agreement with the trend predicted by the model. None of the observed satellites are overly dense compared to the results of our ΛCDM-based model. We also show that although the halo mass of many satellite galaxies is comparable to the halo mass of the MW progenitor at z ≳ 10, at these early epochs halos that survive as satellites to z = 0 are located many virial radii away from the MW progenitors and thus do not have a chance to merge with it. Our results show that neither the densities estimated in observed Milky Way satellites nor their mass assembly histories pose a challenge to the ΛCDM model. In fact, the broad agreement between density trends with the stellar mass of the observed and model galaxies can be considered as yet another success of the model.

Correction to: Subhalo abundance matching using progenitor mass at varying redshift: two modes of stellar mass growth imprinted into the Subaru HSC galaxy clustering

Correction to: Subhalo abundance matching using progenitor mass at varying redshift: two modes of stellar mass growth imprinted into the Subaru HSC galaxy clustering

The Prevalence and Influence of Circumstellar Material around Hydrogen-rich Supernova Progenitors

Narrow transient emission lines (flash-ionization features) in early supernova (SN) spectra trace the presence of circumstellar material (CSM) around the massive progenitor stars of core-collapse SNe. The lines disappear within days after the SN explosion, suggesting that this material is spatially confined, and originates from enhanced mass loss shortly (months to a few years) prior to the explosion. We performed a systematic survey of H-rich (Type II) SNe discovered within less than 2 days from the explosion during the first phase of the Zwicky Transient Facility survey (2018–2020), finding 30 events for which a first spectrum was obtained within <2 days from the explosion. The measured fraction of events showing flash-ionization features (>36% at the 95% confidence level) confirms that elevated mass loss in massive stars prior to SN explosion is common. We find that SNe II showing flash-ionization features are not significantly brighter, nor bluer, nor more slowly rising than those without. This implies that CSM interaction does not contribute significantly to their early continuum emission, and that the CSM is likely optically thin. We measured the persistence duration of flash-ionization emission and find that most SNe show flash features for ≈5 days. Rarer events, with persistence timescales >10 days, are brighter and rise longer, suggesting these may be intermediate between regular SNe II and strongly interacting SNe IIn.

Type II-P supernova progenitor star initial masses and SN 2020jfo: direct detection, light-curve properties, nebular spectroscopy, and local environment

ABSTRACT We present optical, ultraviolet, and infrared data of the type II supernova (SN II) 2020jfo at 14.5 Mpc. This wealth of multiwavelength data allows us to compare different metrics commonly used to estimate progenitor masses of SN II for the same object. Using its early light curve, we infer SN 2020jfo had a progenitor radius of ≈700 R⊙, consistent with red supergiants of initial mass MZAMS =11–13 M⊙. The decline in its late-time light curve is best fit by a 56Ni mass of 0.018 ± 0.007 M⊙ consistent with that ejected from SN II-P with ≈13 M⊙ initial mass stars. Early spectra and photometry do not exhibit signs of interaction with circumstellar matter, implying that SN 2020jfo experienced weak mass-loss within the final years prior to explosion. Our spectra at &amp;gt;250 d are best fit by models from 12 M⊙ initial mass stars. We analysed integral field unit spectroscopy of the stellar population near SN 2020jfo, finding its massive star population had a zero age main sequence mass of 9.7$\substack{+2.5\\ -1.3}~{\rm M}_{\odot }$. We identify a single counterpart in pre-explosion imaging and find it has an initial mass of at most $7.2\substack{+1.2\\ -0.6}~{\rm M}_{\odot }$. We conclude that the inconsistency between this mass and indirect mass indicators from SN 2020jfo itself is most likely caused by extinction with AV = 2–3 mag due to matter around the progenitor star, which lowered its observed optical luminosity. As SN 2020jfo did not exhibit extinction at this level or evidence for interaction with circumstellar matter between 1.6 and 450 d from explosion, we conclude that this material was likely confined within ≈3000 R⊙ from the progenitor star.

Subhalo abundance matching using progenitor mass at varying redshift: two modes of stellar mass growth imprinted into the Subaru HSC galaxy clustering

ABSTRACT We propose a novel subhalo abundance matching (SHAM) model that uses the virial mass of the main progenitor of each (sub)halo Mprog as a proxy of the galaxy stellar mass M* at the time of observation. This Mprog model predicts the two-point correlation functions depending on the choice of the epoch zprog at which Mprog is quoted. With zprog as a fitting parameter, we apply the Mprog model to the angular correlation functions measured with varying stellar mass thresholds from M*, lim/(h−2 M⊙) = 1011–108.6 using a sample of galaxies at z ≃ 0.4 from the Subaru Hyper Suprime-Cam survey. The Mprog model can reproduce the observations very well over 10 h−1kpc–10 h−1Mpc. We find that, for the samples of 109.2 ≤ M*, lim/(h−2 M⊙) ≤ 1010.2, the correlation functions predicted by the widely used Vpeak model lack amplitudes at ≲1 h−1 Mpc, suggesting that Mprog is a better proxy of the galaxy stellar mass than conventional Vpeak. The zprog parameter is highest (zprog ≃ 3) for intermediate mass galaxies at M* ≃ 109.9 h−2 M⊙, and becomes smaller down to zprog ≃ 1 for both lower and higher mass galaxies. We interpret these trends as reflecting the downsizing in the in situ star formation in lower mass galaxies and the larger contribution of the ex situ stellar mass growth in higher mass galaxies.

Inferring the Progenitor Mass–Kinetic Energy Relation of Stripped-envelope Core-collapse Supernovae from Nebular Spectroscopy

The relation between the progenitor mass and the kinetic energy of the explosion is a key toward revealing the explosion mechanism of stripped-envelope core-collapse supernovae (SESNe). Here, we present a method to derive this relation using the nebular spectra of SESNe, based on the correlation between [O i]/[Ca ii], which is an indicator of progenitor mass, and the width of [O i], which measures the expansion velocity of the oxygen-rich material. To explain the correlation, the kinetic energy (E K) is required to be positively correlated with the progenitor mass as represented by the CO core mass (M CO). We demonstrate that SNe IIb/Ib and SNe Ic/Ic-BL follow the same M CO–E K scaling relation, which suggests that helium-rich and helium-deficient SNe share the same explosion mechanism. The M CO–E K relation derived in this work is compared with the ones derived from early phase observations. The results are largely in good agreement. Combined with early phase observations, the method presented in this work provides a chance to scan through the ejecta from the outermost region to the dense inner core, which is important to reveal the global properties of the ejecta and constrain the explosion mechanism of core-collapse SNe.