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The 'red supergiant (RSG) problem' describes the claim that the brightest RSG progenitors to Type II-P supernovae (SNe) are significantly fainter than RSGs in the field. This mismatch has been interpreted by several authors as being a manifestation of the mass threshold for the production of black holes (BHs), such that stars with initial masses above a cut-off of M hi = 17 M⊙ and below 25 M⊙ will die as RSGs, but with no visible SN explosion as the BH is formed. However, we have previously cautioned that this cut-off is more likely to be higher and has large uncertainties (⁠|$M_{\rm hi}=19^{+4}_{-2}\,\mathrm{ M}_{\odot }$|⁠), meaning that the statistical significance of the RSG problem is less than 2σ. Recently, Kochanek has claimed that our work is statistically flawed, and with his analysis has argued that the upper mass cut-off is as low as M hi = 15.7 ± 0.8 M⊙, giving the RSG problem a significance of >10σ. In this letter, we show that Kochanek's low cut-off is caused by a statistical misinterpretation, and the associated fit to the progenitor mass spectrum can be ruled out at the 99.6 per cent confidence level. Once this problem is remedied, Kochanek's best fit becomes |$M_{\rm hi} =19^{+4}_{-2}\,\mathrm{ M}_{\odot }$|⁠ , in excellent agreement with our work. Finally, we argue that, in the search for an RSG 'vanishing' as it collapses directly to a BH, any such survey would have to operate for decades before the absence of any such detection became statistically significant. [ABSTRACT FROM AUTHOR]

Observations indicate that members of close stellar binaries often have mass ratios close to unity, while longer period systems exhibit a more uniform mass-ratio distribution. This paper provides a theoretical explanation for this finding by determining the tidal equilibrium states for binary star systems – subject to the constraints of conservation of angular momentum and constant total mass. This work generalizes previous treatments by including the mass fraction as a variable in the optimization problem. The results show that the lowest energy state accessible to the system corresponds to equal mass stars on a circular orbit, where the stellar spin angular velocities are both synchronized and aligned with the orbit. These features are roughly consistent with observed properties of close binary systems. We also find the conditions required for this minimum energy state to exist: (1) the total angular momentum must exceed a critical value, (2) the orbital angular momentum must be three times greater than the total spin angular momentum, and (3) the semimajor axis is bounded from above. The last condition implies that sufficiently wide binaries are not optimized with equal mass stars, where the limiting binary separation occurs near a 0 ≈ 16 R *. [ABSTRACT FROM AUTHOR]

While the stellar initial mass function (IMF) appears to be close to universal within the Milky Way galaxy, it is strongly suspected to be different in the primordial universe, where molecular hydrogen cooling is less efficient and the gas temperature can be higher by a factor of 30. In between these extreme cases, the gas temperature varies depending on the environment, metallicity, and radiation background. In this paper we explore if changes of the gas temperature affect the IMF of the stars considering fragmentation and accretion. The fragmentation behaviour depends mostly on the Jeans mass at the turning point in the equation of state (EOS) where a transition occurs from an approximately isothermal to an adiabatic regime due to dust opacities. The Jeans mass at this transition in the EOS is always very similar, independent of the initial temperature, and therefore the initial mass of the fragments is very similar. Accretion on the other hand is strongly temperature dependent. We argue that the latter becomes the dominant process for star formation efficiencies above 5–7  per cent, increasing the average mass of the stars. [ABSTRACT FROM AUTHOR]

Annular structures in protoplanetary discs, such as gaps and rings, are now ubiquitously found by high-resolution Atacama Large Millimetre Array observations. Under the hypothesis that they are opened by planets, in this paper we investigate how the minimum planet mass needed to open a gap varies across different stellar host masses and distances from the star. The dependence on the stellar host mass is particularly interesting because, at least in principle, gap opening around low-mass stars should be possible for lower mass planets, giving us a look into the young, low-mass planet population. Using dusty hydrodynamical simulations, we find however the opposite behaviour, as a result of the fact that discs around low-mass stars are geometrically thicker: gap opening around low-mass stars can require more massive planets. Depending on the theoretical isochrone employed to predict the relationship between stellar mass and luminosity, the gap opening planet mass could also be independent of stellar mass, but in no case we find that gap opening becomes easier around low-mass stars. This would lead to the expectation of a lower incidence of such structures in lower mass stars, since exoplanet surveys show that low-mass stars have a lower fraction of giant planets. More generally, our study enables future imaging observations as a function of stellar mass to be interpreted using information on the mass versus luminosity relations of the observed samples. [ABSTRACT FROM AUTHOR]

In this third paper of the MOVES (Multiwavelength Observations of an eVaporating Exoplanet and its Star) programme, we combine Hubble Space Telescope far-ultraviolet (FUV) observations with XMM–Newton / Swift X-ray observations to measure the emission of HD 189733 in various FUV lines, and its soft X-ray spectrum. Based on these measurements we characterize the interstellar medium towards HD 189733 and derive semisynthetic XUV spectra of the star, which are used to study the evolution of its high-energy emission at five different epochs. Two flares from HD 189733 are observed, but we propose that the long-term variations in its spectral energy distribution have the most important consequences for the environment of HD 189733b. Reduced coronal and wind activity could favour the formation of a dense population of Si2+ atoms in a bow-shock ahead of the planet, responsible for pre- and in-transit absorption measured in the first two epochs. In-transit absorption signatures are detected in the Lyman α line in the second, third, and fifth epochs, which could arise from the extended planetary thermosphere and a tail of stellar wind protons neutralized via charge-exchange with the planetary exosphere. We propose that increases in the X-ray irradiation of the planet, and decreases in its EUV irradiation causing lower photoionization rates of neutral hydrogen, favour the detection of these signatures by sustaining larger densities of H0 atoms in the upper atmosphere and boosting charge-exchanges with the stellar wind. Deeper and broader absorption signatures in the last epoch suggest that the planet entered a different evaporation regime, providing clues as to the link between stellar activity and the structure of the planetary environment. [ABSTRACT FROM AUTHOR]

The MZ relation between stellar mass (M*) and metallicity (Z) of nearby galaxies has been described as both a global and local property, i.e. valid also on sub-galaxy scales. Here, we show that Z has remained a local property, following the gravitational potential, since z  = 3. In absorption, the MZ relation has been well studied, and was in place already at z  = 5.1. A recent absorption study of gamma-ray burst galaxies revealed a close match to damped Lyα (DLA) galaxies, surprising due to their vastly different impact parameters and leading the authors to suggest that local metallicity follows the local gravitational potential. In this paper, we formulate an observational test of this hypothesis. The test, in essence, forms a prediction that the velocity dispersion of the absorbing gas in galaxy haloes, normalized by the central velocity dispersion, must follow a steep log scale slope of −0.015 dex |$\rm kpc^{-1}$| as a function of impact parameter out to at least 20–30 kpc. We then compile an archival data and literature-based sample of galaxies seen in both emission and absorption suitable for the test, and find that current data confirm the hypothesis out to 40–60 kpc. In addition, we show that the distribution of the velocity offsets between z em and z abs favours a model where DLA systems are composed of individual sub-clouds distributed along the entire path through the halo, and disfavours a model where they are one single cloud with a bulk motion and internal sub-structure. [ABSTRACT FROM AUTHOR]

Using deep images from the Hyper Suprime-Cam (HSC) survey and taking advantage of its unprecedented weak lensing capabilities, we reveal a remarkably tight connection between the stellar mass distribution of massive central galaxies and their host dark matter halo mass. Massive galaxies with more extended stellar mass distributions tend to live in more massive dark matter haloes. We explain this connection with a phenomenological model that assumes, (1) a tight relation between the halo mass and the total stellar content in the halo, (2) that the fraction of in situ and ex situ mass at r <10 kpc depends on halo mass. This model provides an excellent description of the stellar mass functions (SMFs) of total stellar mass (⁠|$M_{\star }^{\mathrm{max}}$|⁠) and stellar mass within inner 10 kpc (⁠|$M_{\star }^{10}$|⁠) and also reproduces the HSC weak lensing signals of massive galaxies with different stellar mass distributions. The best-fitting model shows that halo mass varies significantly at fixed total stellar mass (as much as 0.4 dex) with a clear dependence on |$M_{\star }^{10}$|⁠. Our two-parameter |$M_{\star }^{\mathrm{max}}$| – |$M_{\star }^{10}$| description provides a more accurate picture of the galaxy–halo connection at the high-mass end than the simple stellar–halo mass relation (SHMR) and opens a new window to connect the assembly history of haloes with those of central galaxies. The model also predicts that the ex situ component dominates the mass profiles of galaxies at r < 10 kpc for log  M ⋆ ≥ 11.7. The code used for this paper is available online https://github.com/dr-guangtou/asap [ABSTRACT FROM AUTHOR]

Type Ibn supernovae (SNe Ibn) are intriguing stellar explosions whose spectra exhibit narrow helium lines with little hydrogen. They trace the presence of circumstellar material (CSM) formed via pre-SN eruptions of their stripped-envelope progenitors. Early work has generally assumed that SNe Ibn come from massive Wolf–Rayet (WR) stars via single-star evolution. In this paper, we report ultraviolet (UV) and optical observations of two nearby Type Ibn SNe 2006jc and 2015G conducted with the Hubble Space Telescope (HST) at late times. A point source is detected at the position of SN 2006jc, and we confirm the conclusion of Maund et al. that it is the progenitor's binary companion. Its position on the Hertzsprung–Russell (HR) diagram corresponds to a star that has evolved off the main sequence (MS); further analysis implies a low initial mass for the companion star (M 2 ≤ 12.3 |$^{+2.3}_{-1.5}$|  M⊙) and a secondary-to-primary initial mass ratio very close to unity (q  =  M 2/ M 1 ∼ 1); the SN progenitor's hydrogen envelope had been stripped through binary interaction. We do not detect the binary companion of SN 2015G. For both SNe, the surrounding stellar populations have relatively old ages and argue against any massive WR stars as their progenitors. These results suggest that SNe Ibn may have lower mass origins in interacting binaries. As a result, they also provide evidence that the giant eruptions commonly seen in massive luminous blue variables (LBVs) can also occur in much lower mass, stripped-envelope stars just before core collapse. [ABSTRACT FROM AUTHOR]

In our earlier 2019 paper, we evaluated the reliability of Schwarzschild's orbit-superposition dynamical modelling method in estimating the internal mass distribution, intrinsic stellar shapes and orbit distributions of early-type galaxies (ETGs) taken from the Illustris cosmological simulation. We now apply the same techniques to galaxies taken from the integral-field survey Mapping Nearby Galaxies with APO (MaNGA), using a sample of 149 ETGs in the mass range of |$10^{9.90}\!-\! 10^{11.80} \, \mathrm{M}_{\odot }$| and made up of 105 central and 44 satellite galaxies. We find that low-mass ETGs with log (M */M⊙) < 11.1 have an average dark matter fraction of ∼0.2 within one effective radius R e, tend to be oblate-like, and are dominated by rotation about their minor axis. High-mass ETGs with log (M */M⊙) > 11.1 have an average dark matter fraction of ∼0.4 within one effective radius R e, tend to be prolate-like, and are dominated by rotation about their major axis and by centrophilic orbits. The changes of internal structures within one R e are dominated by the total stellar mass of the individual galaxies. We find no differences of internal structures between central and satellite ETGs for the same stellar masses. However, for similar stellar mass and colour distributions, we find that ETGs more prolate-like, or with more hot orbits, tend to have higher close neighbour counts at rp  ∼ 40 kpc. [ABSTRACT FROM AUTHOR]

We introduce the 'Engineering Dwarfs at Galaxy Formation's Edge' (EDGE) project to study the cosmological formation and evolution of the smallest galaxies in the Universe. In this first paper, we explore the effects of resolution and sub-grid physics on a single low-mass halo (⁠|$M_{\rm halo}=10^{9}{\, \rm M}_\odot$|⁠), simulated to redshift z  = 0 at a mass and spatial resolution of |$\sim 20{\, \rm M}_\odot$| and ∼3 pc. We consider different star formation prescriptions, supernova feedback strengths, and on-the-fly radiative transfer (RT). We show that RT changes the mode of galactic self-regulation at this halo mass, suppressing star formation by causing the interstellar and circumgalactic gas to remain predominantly warm (∼104 K) even before cosmic reionization. By contrast, without RT, star formation regulation occurs only through starbursts and their associated vigorous galactic outflows. In spite of this difference, the entire simulation suite (with the exception of models without any feedback) matches observed dwarf galaxy sizes, velocity dispersions, V -band magnitudes, and dynamical mass-to-light-ratios. This is because such structural scaling relations are predominantly set by the host dark matter halo, with the remaining model-to-model variation being smaller than the observational scatter. We find that only the stellar mass–metallicity relation differentiates the galaxy formation models. Explosive feedback ejects more metals from the dwarf, leading to a lower metallicity at a fixed stellar mass. We conclude that the stellar mass–metallicity relation of the very smallest galaxies provides a unique constraint on galaxy formation physics. [ABSTRACT FROM AUTHOR]

This paper considers how planetesimal impacts affect planetary atmospheres. Atmosphere evolution depends on the ratio of gain from volatiles to loss from atmosphere stripping f v; for constant bombardment, atmospheres with f v < 1 are destroyed in finite time, but grow linearly with time for f v > 1. An impact outcome prescription is used to characterize how f v depends on planetesimal impact velocities, size distribution, and composition. Planets that are low mass and/or close to the star have atmospheres that deplete in impacts, while high-mass and/or distant planets grow secondary atmospheres. Dividing these outcomes is an f v = 1 impact shoreline analogous to Zahnle and Catling's cosmic shoreline. The impact shoreline's location depends on assumed impacting planetesimal properties, so conclusions for the atmospheric evolution of a planet like the Earth with f v ≈ 1 are only as strong as those assumptions. Application to the exoplanet population shows that the gap in the planet radius distribution at ∼1.5 R⊕ is coincident with the impact shoreline, which has a similar dependence on orbital period and stellar mass to the observed gap. Given sufficient bombardment, planets below the gap would be expected to lose their atmospheres, while those above could have atmospheres enhanced in volatiles. The level of atmosphere alteration depends on the total bombardment a planet experiences, and so on the system's (usually unknown) other planets and planetesimals, though massive distant planets would have low accretion efficiency. Habitable zone planets around lower luminosity stars are more susceptible to atmosphere stripping, disfavouring M stars as hosts of life-bearing planets if Earth-like bombardment is conducive to the development of life. [ABSTRACT FROM AUTHOR]

Hydrodynamical cosmological simulations have recently made great advances in reproducing galaxy mass assembly over cosmic time – as often quantified from the comparison of their predicted stellar mass functions to observed stellar mass functions from data. In this paper, we compare the clustering of galaxies from the hydrodynamical cosmological simulated light-cone Horizon-AGN to clustering measurements from the VIDEO survey observations. Using mocks built from a VIDEO-like photometry, we first explore the bias introduced into clustering measurements by using stellar masses and redshifts derived from spectral energy distribution fitting, rather than the intrinsic values. The propagation of redshift and mass statistical and systematic uncertainties in the clustering measurements causes us to underestimate the clustering amplitude. We then find that clustering and halo occupation distribution (HOD) modelling results are qualitatively similar in Horizon-AGN and VIDEO. However, at low stellar masses, Horizon-AGN underestimates the observed clustering by up to a factor of ∼3, reflecting the known excess stellar mass to halo mass ratio for Horizon-AGN low-mass haloes, already discussed in previous works. This reinforces the need for stronger regulation of star formation in low-mass haloes in the simulation. Finally, the comparison of the stellar mass to halo mass ratio in the simulated catalogue, inferred from angular clustering, to that directly measured from the simulation validates HOD modelling of clustering as a probe of the galaxy–halo connection. [ABSTRACT FROM AUTHOR]

Galaxies and galaxy groups located along the line of sight towards gravitationally lensed quasars produce high-order perturbations of the gravitational potential at the lens position. When these perturbation are too large, they can induce a systematic error on H 0 of a few per cent if the lens system is used for cosmological inference and the perturbers are not explicitly accounted for in the lens model. In this work, we present a detailed characterization of the environment of the lens system WFI 2033−4723 (⁠|$z_{\rm src} =\,$| 1.662, |$z_{\rm lens}=\,$| 0.6575), one of the core targets of the H0LiCOW project for which we present cosmological inferences in a companion paper. We use the Gemini and ESO-Very Large telescopes to measure the spectroscopic redshifts of the brightest galaxies towards the lens, and use the ESO-MUSE integral field spectrograph to measure the velocity-dispersion of the lens (⁠|$\sigma _{\rm {los}}= 250^{+15}_{-21}$|  km s−1) and of several nearby galaxies. In addition, we measure photometric redshifts and stellar masses of all galaxies down to i < 23 mag, mainly based on Dark Energy Survey imaging (DR1). Our new catalogue, complemented with literature data, more than doubles the number of known galaxy spectroscopic redshifts in the direct vicinity of the lens, expanding to 116 (64) the number of spectroscopic redshifts for galaxies separated by less than 3 arcmin (2 arcmin ) from the lens. Using the flexion-shift as a measure of the amplitude of the gravitational perturbation, we identify two galaxy groups and three galaxies that require specific attention in the lens models. The ESO MUSE data enable us to measure the velocity-dispersions of three of these galaxies. These results are essential for the cosmological inference analysis presented in Rusu et al. [ABSTRACT FROM AUTHOR]

The star formation main sequence (SFMS) is a tight relation between the galaxy star formation rate (SFR) and its total stellar mass (M ⋆). Early-type galaxies (ETGs) are often considered as low-SFR outliers of this relation. We study, for the first time, the separated distribution in the SFR versus M ⋆ of bulges and discs of 49 ETGs from the CALIFA survey. This is achieved using c2d , a new code to perform spectrophotometric decompositions of integral field spectroscopy data cubes. Our results reflect that: (i) star formation always occurs in the disc component and not in bulges; (ii) star-forming discs in our ETGs are compatible with the SFMS defined by star-forming galaxies at z ∼ 0; (iii) the star formation is not confined to the outskirts of discs, but it is present at all radii (even where the bulge dominates the light); (iv) for a given mass, bulges exhibit lower sSFR than discs at all radii; and (v) we do not find a deficit of molecular gas in bulges with respect to discs for a given mass in our ETGs. We speculate our results favour a morphological quenching scenario for ETGs. [ABSTRACT FROM AUTHOR]

We introduce algorithms for black hole physics, i.e. black hole formation, accretion, and feedback, into the Numerical Investigation of a Hundred Astrophysical Objects (NIHAO) project of galaxy simulations. This enables us to study high mass, elliptical galaxies, where feedback from the central black hole is generally thought to have a significant effect on their evolution. We furthermore extend the NIHAO suite by 45 simulations that encompass z  = 0 halo masses from 1 × 1012 to |$4 \times 10^{13}\, \mathrm{M}_{\odot }$|⁠ , and resimulate five galaxies from the original NIHAO sample with black hole physics, which have z  = 0 halo masses from 8 × 1011 to |$3 \times 10^{12}\, \mathrm{M}_{\odot }$|⁠. Now NIHAO contains 144 different galaxies and thus has the largest sample of zoom-in simulations of galaxies, spanning z  = 0 halo masses from 9 × 108 to |$4 \times 10^{13}\, \mathrm{M}_{\odot }$|⁠. In this paper we focus on testing the algorithms and calibrating their free parameters against the stellar mass versus halo mass relation and the black hole mass versus stellar mass relation. We also investigate the scatter of these relations, which we find is a decreasing function with time and thus in agreement with observations. For our fiducial choice of parameters we successfully quench star formation in objects above a z  = 0 halo mass of |$10^{12}\, \mathrm{M}_{\odot }$|⁠ , thus transforming them into red and dead galaxies. [ABSTRACT FROM AUTHOR]

Neutron stars with near-Eddington observable luminosities were shown to harbour levitating atmospheres, suspended above their surfaces. We report a new method to simultaneously measure the mass and radius of a neutron star based on oscillations of such atmospheres. In this paper, we present an analytic derivation of a family of relativistic, oscillatory, spherically symmetric eigenmodes of the optically and geometrically thin levitating atmospheres, including the damping effects induced by the radiation drag. We discover characteristic maxima in the frequencies of the damped oscillations and show that from a measurement of the frequency maximum and of the luminosity one can determine the mass and radius of the neutron star. In addition to the stellar parameters, observation of the variation of the oscillation frequencies with flux would allow us to estimate the stellar luminosity and therefore the distance to the source with an accuracy of a few per cent. We also show that the ratio of any two undamped eigenfrequencies depends only on the adiabatic index of the atmosphere, while for the damped eigenfrequencies, this ratio varies with the luminosity. The damping coefficient is independent of the mode number of the oscillations. Signatures of the dynamics of such atmospheres will be reflected in the source's X-ray light curves. [ABSTRACT FROM AUTHOR]

The most metal-poor, high redshift damped Lyman-α systems (DLAs) provide a window to study some of the first few generations of stars. In this paper, we present a novel model to investigate the chemical enrichment of the near-pristine DLA population. This model accounts for the mass distribution of the enriching stellar population, the typical explosion energy of their supernovae, and the average number of stars that contribute to the enrichment of these DLAs. We conduct a maximum likelihood analysis of these model parameters using the observed relative element abundances ([C/O], [Si/O], and [Fe/O]) of the 11 most metal-poor DLAs currently known. We find that the mass distribution of the stars that have enriched this sample of metal-poor DLAs can be well-described by a Salpeter-like IMF slope at M > 10 M⊙ and that a typical metal-poor DLA has been enriched by ≲ 72 massive stars (⁠|$95{{\ \rm per\ cent}}$| confidence), with masses ≲ 40 M⊙. The inferred typical explosion energy (⁠|$\hat{E}_{\rm exp}=1.8^{+0.3}_{-0.2}\times 10^{51}~{\rm erg}$|⁠) is somewhat lower than that found by recent works that model the enrichment of metal-poor halo stars. These constraints suggest that some of the metal-poor DLAs in our sample may have been enriched by Population II stars. Using our enrichment model, we also infer some of the typical physical properties of the most metal-poor DLAs. We estimate that the total stellar mass content is |$\log _{10}(M_{\star }/{\rm M_{\odot }})=3.5^{+0.3}_{-0.4}$| and the total gas mass is |$\log _{10}({M_{\rm gas}}/~{\rm M_{\odot }})= 7.0^{+0.3}_{-0.4}$| for systems with a relative oxygen abundance [O/H] ≈ −3.0. [ABSTRACT FROM AUTHOR]

Dwarf stars with debris discs and planets appear to be excellent laboratories to study the core accretion theory of planets formation. These systems are however, insufficiently studied. In this paper we present the main metallicity and lithium abundance properties of these stars together with stars with only debris discs and stars with only planets. Stars without detected planets or discs are also considered. The analysed sample is formed by main-sequence FGK field single stars. Apart from the basic stellar parameters, we include the use of dusty discs masses. The main results show for the first time that the dust mass of debris disc stars with planets correlate with metallicity. We confirm that these disc dust masses are related to their central stellar masses. Separately, the masses of stars and those of planets also correlate with metallicity. We conclude that two conditions are necessary to form giant planets: to have a sufficient metallicity and also a sufficient protoplanetary mass of gas and dust. The debris discs masses of stars without giant planets do not correlate with metallicity, because they do not fulfil these two conditions. Concerning lithium, by adopting a stellar model for lithium depletion based on a strong interaction between the star and a protoplanetary disc, we found that in agreement with the model predictions, observations indicate that the main lithium depletion occurs during this initial protoplanetary evolution stage. We show that the ultimately lithium depletion is independent of the presence or absence of planets and appears to be only age dependent. [ABSTRACT FROM AUTHOR]

This paper reports on the atomic hydrogen gas (H  i) observations of the spiral galaxy NGC 1566 using the newly commissioned Australian Square Kilometre Array Pathfinder radio telescope. We measure an integrated H  i flux density of |$180.2$|  Jy km s−1 emanating from this galaxy, which translates to an H  i mass of |$1.94\times 10^{10}\, \mathrm{ M}_{\odot }$| at an assumed distance of |$21.3$|  Mpc. Our observations show that NGC 1566 has an asymmetric and mildly warped H  i disc. The H  i -to-stellar mass fraction (M |$_{\rm{H\,{{\small I}}}}$| /M∗) of NGC 1566 is 0.29, which is high in comparison with galaxies that have the same stellar mass (⁠|$10^{10.8}$|  M⊙). We also derive the rotation curve of this galaxy to a radius of |$50$|  kpc and fit different mass models to it. The NFW, Burkert, and pseudo-isothermal dark matter halo profiles fit the observed rotation curve reasonably well and recover dark matter fractions of 0.62, 0.58, and 0.66, respectively. Down to the column density sensitivity of our observations (⁠|$N_{\rm{H\,{{\small I}}}}\, =\, 3.7\times 10^{19}$|  cm−2), we detect no H  i clouds connected to, or in the nearby vicinity of, the H  i disc of NGC 1566 nor nearby interacting systems. We conclude that, based on a simple analytic model, ram pressure interactions with the IGM can affect the H  i disc of NGC 1566 and is possibly the reason for the asymmetries seen in the H  i morphology of NGC 1566. [ABSTRACT FROM AUTHOR]

We have recently developed a post-processing framework to estimate the abundance of atomic and molecular hydrogen (H  i and H2, respectively) in galaxies in large-volume cosmological simulations. Here we compare the H  i and H2 content of IllustrisTNG galaxies to observations. We mostly restrict this comparison to z ≈ 0 and consider six observational metrics: the overall abundance of H  i and H2, their mass functions, gas fractions as a function of stellar mass, the correlation between H2 and star formation rate, the spatial distribution of gas, and the correlation between gas content and morphology. We find generally good agreement between simulations and observations, particularly for the gas fractions and the H  i mass–size relation. The H2 mass correlates with star formation rate as expected, revealing an almost constant depletion time that evolves up to z  = 2 as observed. However, we also discover a number of tensions with varying degrees of significance, including an overestimate of the total neutral gas abundance at z  = 0 by about a factor of 2 and a possible excess of satellites with no or very little neutral gas. These conclusions are robust to the modelling of the H  i /H2 transition. In terms of their neutral gas properties, the IllustrisTNG simulations represent an enormous improvement over the original Illustris run. All data used in this paper are publicly available as part of the IllustrisTNG data release. [ABSTRACT FROM AUTHOR]

This paper presents stellar mass functions and i -band luminosity functions for Sloan Digital Sky Survey (SDSS) galaxies with i < 21 using clustering redshifts. From these measurements, we also compute targeting completeness measurements for the Baryon Oscillation Spectroscopic Survey (BOSS). Clustering redshifts is a method of obtaining the redshift distribution of a sample of galaxies with only photometric information by measuring the angular cross-correlation with a spectroscopic sample in different redshift bins. We construct a spectroscopic sample containing data from the BOSS + eBOSS surveys, allowing us to recover redshift distributions from photometric data out to z ≃ 2.5. We produce k -corrected i -band luminosity functions and stellar mass functions by applying clustering redshifts to SDSS DR8 galaxies in small bins of colour and magnitude. There is little evolution in the mass function between 0.2 < z < 0.8, implying that the most massive galaxies form most of their mass before z  = 0.8. These mass functions are used to produce stellar mass completeness estimates for the BOSS, giving a stellar mass completeness of |$80{{\ \rm per\ cent}}$| above M ⋆ > 1011.4 between 0.2 < z < 0.7, with completeness falling significantly at redshifts higher than 0.7, and at lower masses. Large photometric data sets will be available in the near future (DECaLS, DES, Euclid), so this and similar techniques will become increasingly useful in order to fully utilize these data. [ABSTRACT FROM AUTHOR]

In this paper, we study the molecular gas content of a representative sample of 67 of the most massive early-type galaxies (ETGs) in the local universe, drawn uniformly from the MASSIVE survey. We present new Institut de Radioastronomie Millimétrique (IRAM) 30-m telescope observations of 30 of these galaxies, allowing us to probe the molecular gas content of the entire sample to a fixed molecular-to-stellar mass fraction of 0.1 per cent. The total detection rate in this representative sample is 25 |$^{+5.9}_{-4.4}$|  per cent, and by combining the MASSIVE and atlas 3D molecular gas surveys, we find a joint detection rate of 22.4 |$^{+2.4}_{-2.1}$|  per cent. This detection rate seems to be independent of galaxy mass, size, position on the Fundamental Plane, and local environment. We show here for the first time that true slow rotators can host molecular gas reservoirs, but the rate at which they do so is significantly lower than for fast rotators. Objects with a higher velocity dispersion at fixed mass (a higher kinematic bulge fraction) are less likely to have detectable molecular gas, and where gas does exist, have lower molecular gas fractions. In addition, satellite galaxies in dense environments have ≈0.6 dex lower molecular gas-to-stellar mass ratios than isolated objects. In order to interpret these results, we created a toy model, which we use to constrain the origin of the gas in these systems. We are able to derive an independent estimate of the gas-rich merger rate in the low-redshift universe. These gas-rich mergers appear to dominate the supply of gas to ETGs, but stellar mass loss, hot halo cooling, and transformation of spiral galaxies also play a secondary role. [ABSTRACT FROM AUTHOR]

Explaining the internal distribution and motions of stars and gas in galaxies is a key aspect in understanding their evolution. In previous work we identified five well-resolved galaxies with atypical kinematics from a cosmological simulation; two had kinematically distinct cores (KDCs), and three had counter-rotating gas and stars (CRGD). In this paper, we show that (i) the KDC galaxies have flattening of stellar [O/Fe] at large galactocentric radii due to the minor mergers that gave rise to the KDCs, and (ii) the CRGD galaxies have an abrupt transition in the gas metallicity maps, from high metallicity in the centre to very low metallicity further out. These galaxies are embedded in dark matter filaments where there is a ready supply of near-pristine gas to cause this effect. The non-linear increase in gas metallicity is also seen in the radial profiles, but when the metallicity gradients are measured, the difference is buried in the scatter of the relation. We also find that all five galaxies are fairly compact, with small effective radii given their stellar masses. This is because they have not experienced major mergers that kinematically heat the stars, and would have destroyed their unusual kinematics. In order to detect these signatures of minor mergers or accretion, the galaxy scaling relations or radial metallicity profiles are not enough, and it is necessary to obtain the two-dimensional maps with integral field spectroscopy observations. [ABSTRACT FROM AUTHOR]

We introduce our new code myosotis (Make Your Own Synthetic ObservaTIonS) which is designed to produce synthetic observations from simulated clusters. The code can synthesize observations from both ground- and spaced-based observatories, for a range of different filters, observational conditions and angular/spectral resolution. In this paper, we highlight some of the features of myosotis, creating synthetic observations from young massive star clusters. Our model clusters are simulated using nbody6 code and have different total masses, half-mass radii, and binary fractions. The synthetic observations are made at the age of 2 Myr with Solar metallicity and under different extinction conditions. For each cluster, we create synthetic images of the Hubble Space Telescope (HST) in the visible (WFPC2/ F 555 W) as well as Very Large Telescopes in the nearIR (SPHERE/IRDIS/ K s). We show how myosotis can be used to look at mass function (MF) determinations. For this aim we re-estimate stellar masses using a photometric analysis on the synthetic images. The synthetic MF slopes are compared to their actual values. Our photometric analysis demonstrate that depending on the adopted filter, extinction, angular resolution, and pixel sampling of the instruments, the power-law index of the underlying MFs can be shallower than the observed ones by at least ±0.25 dex which is in agreement with the observed discrepancies reported in the literature, specially for young star clusters. [ABSTRACT FROM AUTHOR]

Massive early-type galaxies follow a tight relation between the mass of their central supermassive black hole (M BH) and their stellar mass (M ⋆). The origin of observed positive outliers from this relation with extremely high M BH (⁠|$\gt 10^{9}\, \rm M_{\odot }$|⁠) remains unclear. We present a study of such outliers in the Hydrangea/C-EAGLE cosmological hydrodynamical simulations, designed to enable the study of high-mass galaxy formation and evolution in cluster environments. We find 69 M BH(M ⋆) outliers at |$z$|  = 0, defined as those with |$M_{\rm BH}\gt 10^{7}\, \rm M_{\odot }$| and M BH/ M ⋆ > 0.01. This paper focuses on a sample of five extreme outliers, that have been selected based on their M BH and M ⋆ values, which are comparable to the most recent estimates of observed positive outliers. This sample of five outliers, classified as 'black hole monster galaxies' (BMGs), was traced back in time to study their origin and evolution. In agreement with the results of previous simulations for lower mass M BH(M ⋆) outliers, we find that these galaxies became outliers due to a combination of their early formation times and tidal stripping. For BMGs with |$M_{\rm BH}\gt 10^9\, \rm M_{\odot }$|⁠, major mergers (with a stellar mass ratio of μ > 0.25) at early times (⁠|$z$| > 2) precede the rapid growth of their supermassive BHs. Furthermore, the scatter in the relation between M BH and stellar velocity dispersion, σ, correlates positively with the scatter in [Mg/Fe](σ). This indicates that the alpha enhancement of these galaxies, which is closely related to their star formation history, is related to the growth of their central BHs. [ABSTRACT FROM AUTHOR]

We study the physical properties of the ionized gas in local discs using the sample of 38 nearby ∼108.5–11.2 M⊙ Star-Forming Main-Sequence (SFMS) galaxies observed so far as part of the MUSE Atlas of Disks (MAD). Specifically, we use all strong emission lines in the MUSE wavelength range 4650–9300 Å to investigate the resolved ionized gas properties on ∼100 pc scales. This spatial resolution enables us to disentangle H  ii regions from the diffuse ionized gas (DIG) in the computation of gas metallicities and star formation rates (SFRs) of star-forming regions. The gas metallicities generally decrease with radius. The metallicity of the H  ii regions is on average ∼0.1 dex higher than that of the DIG, but the metallicity radial gradient in both components is similar. The mean metallicities within the inner galaxy cores correlate with the total stellar mass of the galaxies. On our < 100 pc scales, we find two correlations previously reported at kpc scales: a spatially resolved mass–metallicity relation (RMZR) and a spatially resolved SFMS (RSFMS). We find no secondary dependence of the RMZR with the SFR density. We find that both resolved relations have a local origin, as they do not depend on the total stellar mass. The observational results of this paper are consistent with the inside-out scenario for the growth of galactic disks. [ABSTRACT FROM AUTHOR]

In this third paper of the series, we investigate the effects of warm dark matter (WDM) with a particle mass of |$m_\mathrm{WDM}=3\, \mathrm{keV}$| on the smallest galaxies in our Universe. We present a sample of 21 hydrodynamical cosmological simulations of dwarf galaxies and 20 simulations of satellite-host galaxy interaction that we performed both in a cold dark matter (CDM) and WDM scenario. In the WDM simulations, we observe a higher critical mass for the onset of star formation. Structure growth is delayed in WDM, as a result WDM haloes have a stellar population on average 2 Gyr younger than their CDM counterparts. Nevertheless, despite this delayed star formation, CDM and WDM galaxies are both able to reproduce the observed scaling relations for velocity dispersion, stellar mass, size, and metallicity at |$z$|  = 0. WDM satellite haloes in a Milky Way mass host are more susceptible to tidal stripping due to their lower concentrations, but their galaxies can even survive longer than the CDM counterparts if they live in a dark matter halo with a stee per central slope. In agreement with our previous CDM satellite study we observe a steepening of the WDM satellites' central dark matter density slope due to stripping. The difference in the average stellar age for satellite galaxies, between CDM and WDM, could be used in the future for disentangling these two models. [ABSTRACT FROM AUTHOR]

This paper presents optical (ugri Hα)–infrared (JHK s, 3.6–8.0 μm) photometry and Gaia astrometry of 55 Classical T-Tauri stars (CTTS) in the star-forming region Sh 2-012 and its central cluster NGC 6383. The sample was identified based on photometric Hα emission linewidths, and has a median age of 2.8 ± 1.6 Myr, with a mass range between 0.3 and 1  M⊙. 94 per cent of CTTS with near-infrared cross-matches fall on the near-infrared T-Tauri locus, with all stars having mid-infrared photometry exhibiting evidence for accreting circumstellar discs. CTTS are found concentrated around the central cluster NGC 6383, and towards the bright rims located at the edges of Sh 2-012. Stars across the region have similar ages, suggestive of a single burst of star formation. Mass accretion rates (⁠|$\dot{M}_{\textrm{acc}}$|⁠) estimated via Hα and u -band line intensities show a scatter (0.3 dex) similar to spectroscopic studies, indicating the suitability of Hα photometry to estimate |$\dot{M}_{\textrm{acc}}$|⁠. Examining the variation of |$\dot{M}_{\textrm{acc}}$| with stellar mass (M *), we find a smaller intercept in the |$\dot{M}_{\textrm{acc}}$| – M * relation than oft-quoted in the literature, providing evidence to discriminate between competing theories of protoplanetary disc evolution. [ABSTRACT FROM AUTHOR]

We study the impact of a warm dark matter (WDM) cosmology on dwarf galaxy formation through a suite of cosmological hydrodynamical zoom-in simulations of |$M_{\rm halo} \approx 10^{10}\, \mathrm{ M}_{\odot }$| dark matter haloes as part of the Feedback in Realistic Environments (FIRE) project. A main focus of this paper is to evaluate the combined effects of dark matter physics and stellar feedback on the well-known small-scale issues found in cold dark matter (CDM) models. We find that the |$z$|  = 0 stellar mass of a galaxy is strongly correlated with the central density of its host dark matter halo at the time of formation, |$z$| f, in both CDM and WDM models. WDM haloes follow the same M ⋆(⁠|$z$|  = 0)– V max(⁠|$z$| f) relation as in CDM, but they form later, are less centrally dense, and therefore contain galaxies that are less massive than their CDM counterparts. As a result, the impact of baryonic effects on the central gravitational potential is typically diminished relative to CDM. However, the combination of delayed formation in WDM and energy input from stellar feedback results in dark matter profiles with lower overall densities. The WDM galaxies studied here have a wider diversity of star formation histories (SFHs) than the same systems simulated in CDM, and the two lowest M ⋆ WDM galaxies form all of their stars at late times. The discovery of young ultrafaint dwarf galaxies with no ancient star formation – which do not exist in our CDM simulations – would therefore provide evidence in support of WDM. [ABSTRACT FROM AUTHOR]

We present results from an ongoing investigation using the Kilo Degree Survey (KiDS) on the VLT Survey Telescope (VST) to provide a census of ultra-compact massive galaxies (UCMGs), defined as galaxies with stellar masses |${M_{\star }}\gt 8 \times 10^{10} \, \rm {\mathrm{ M}_\odot}$| and effective radii |${R_{\rm e}}\lt 1.5\, \rm kpc$|⁠. UCMGs, which are expected to have undergone very few merger events, provide a unique view on the accretion history of the most massive galaxies in the Universe. Over an effective sky area of nearly 330 deg2, we select UCMG candidates from KiDS multicolour images, which provide high quality structural parameters, photometric redshifts, and stellar masses. Our sample of ∼1000 photometrically selected UCMGs at |$z$| < 0.5 represents the largest sample of UCMG candidates assembled to date over the largest sky area. In this paper, we present the first effort to obtain their redshifts using different facilities, starting with first results for 28 candidates with redshifts |$z$| < 0.5, obtained at NTT and TNG telescopes. We confirmed, as bona fide UCMGs, 19 out of the 28 candidates with new redshifts. A further 46 UCMG candidates are confirmed with literature spectroscopic redshifts (35 at |$z$| < 0.5), bringing the final cumulative sample of spectroscopically confirmed lower- z UCMGs to 54 galaxies, which is the largest sample at redshifts below 0.5. We use these spectroscopic redshifts to quantify systematic errors in our photometric selection, and use these to correct our UCMG number counts. We finally compare the results to independent data sets and simulations. [ABSTRACT FROM AUTHOR]

A thermal soft X-ray component is often detected in low-level accreting neutron stars (NSs), but is not detected in low-level accreting stellar-mass black holes (BHs). In this paper, we investigate the origin of such a thermal soft X-ray component in the framework of the self-similar solution of the advection-dominated accretion flow (ADAF) around NSs. It is assumed that a fraction, f th, of the energy transferred on to the surface of the NS is thermalized at the surface of the NS as the soft photons to be scattered in the ADAF. We self-consistently calculate the structure and the corresponding emergent spectrum of the ADAF by considering the radiative coupling between the soft photons from the surface of the NS and the ADAF itself. We show that the Compton y -parameter of the ADAF for NSs is systematically lower than that of BHs. Meanwhile, we find that the temperature of the thermal soft X-ray component in NSs decreases with decreasing mass accretion rate, which is qualitatively consistent with observations. We test the effect of f th on the structure, as well as the emergent spectrum of the ADAF. It is found that a change of f th can significantly change the temperature of the thermal soft X-ray component as well as the spectral slope in hard X-rays. Finally, it is suggested that the value of f th can be constrained by fitting the high-quality X-ray data, such as the XMM–Newton spectrum between 0.5 and 10 keV in a future work. [ABSTRACT FROM AUTHOR]

Stellar spin–orbit misalignments (obliquities) in hot Jupiter (HJ) systems have been extensively probed. Such obliquities may reveal clues about HJ dynamical histories. Common explanations for generating obliquities include high-eccentricity migration and primordial disc misalignment. This paper investigates another mechanism for producing stellar spin–orbit misalignments in systems hosting a close-in planet with an external, modestly inclined companion. Spin–orbit misalignment may be excited due to a secular resonance, occurring when the precession rate of the stellar spin axis (driven by the inner planet) becomes comparable to the nodal precession rate of the inner planet (driven by the companion). Due to the spin-down of the host star via magnetic braking, this resonance may be achieved during the star's main-sequence lifetime for a wide range of planet masses and orbital architectures. Obliquity excitation is accompanied by a decrease in mutual inclination between the inner planet and perturber, and can thus erase high inclinations. For HJs, the stellar spin axis is strongly coupled to the orbital axis, and obliquity excitation by a giant planet companion requires a strong perturber, usually located within 1–2 au. For warm Jupiters (WJs), the spin and orbital axes are more weakly coupled, and the resonance may be achieved for distant giant planet perturbers (at several to tens of au). Since WJs have a high occurrence rate of distant planetary companions with appropriate properties for resonant obliquity excitation, stellar obliquities in WJ systems may be common, particularly for WJs orbiting cool stars that have undergone significant spin-down. [ABSTRACT FROM AUTHOR]

We investigate a relation between surface densities of star formation rate (SFR) and stellar mass (M *) at a ∼1 kpc scale namely spatially resolved star formation main sequence (SFMS) in massive (log (M */ M ⊙) > 10.5) face-on disc galaxies at 0.01 < $$z$$ < 0.02 and 0.8 < $$z$$ < 1.8 and examine evolution of the relation. The spatially resolved SFMS of $$z$$ ∼ 0 galaxies is discussed in a companion paper. For $$z$$ ∼ 1 sample, we use eight bands imaging data set from Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey and 3D- HST and perform a pixel-to-pixel spectral energy distribution fitting to derive the spatially resolved SFR and M *. We find a linear spatially resolved SFMS in the $$z$$ ∼ 1 galaxies that lie on the global SFMS, while a ‘flattening’ at high Σ* end is found in that relation for the galaxies that lie below the global SFMS. Comparison with the spatially resolved SFMS of the $$z$$ ∼ 0 galaxies shows smaller difference in the specific SFR (sSFR) at low Σ* than that at high Σ*. This trend is consistent with the evolution of the sSFR(r) radial profile, which shows a faster decrease in the central region than in the outskirt, agrees with the inside–out quenching scenario. We then derive an empirical model for the evolution of the Σ*(r), ΣSFR(r), and sSFR(r) radial profiles. Based on the empirical model, we estimate the radial profile of the quenching time-scale and reproduce the observed spatially resolved SFMS at $$z$$ ∼ 1 and ∼0. [ABSTRACT FROM AUTHOR]

We report the discovery, spectroscopic confirmation, and first lens models of the first, strongly lensed quasars from a combined search in WISE and Gaia-DR1 over the DES footprint. Their Einstein radii span a range between ≈2.0 arcsec and ≈0.4 arcsec. Two of these (WGD2038-4008, RA = 20:38:02.65, Dec. = −40:08:14.64; WGD2021-4115, RA = 20:21:39.45, Dec. = −41:15:57.11) also have confirmed deflector redshifts. The four-image lens WGD2038-4008, with source and deflector redshifts s = 0.777 ± 0.001 and zl = 0.230 ± 0.002, respectively, has a deflector with radius R eff ≈ 3.4 arcsec, stellar mass $$\log (M_{\star }/M_{\odot })=11.64^{+0.20}_{-0.43}$$, and extended isophotal shape variation. Simple lens models yield Einstein radii R E = (1.30 ± 0.04) arcsec, axis ratio q = 0.75 ± 0.1 (compatible with that of the starlight) and considerable shear-ellipticity degeneracies. The two-image lens WGD2021-4115 has zs = 1.390 ± 0.001 and zl = 0.335 ± 0.002, and Einstein radius R E = (1.1 ± 0.1) arcsec, but higher-resolution imaging is needed to accurately separate the deflector and faint quasar image. Analogous lens model degeneracies hold for the other six lenses (J0146-1133, J0150-4041, J0235-2433, J0245-0556, J0259-2338, and J0508-2748) shown in this paper. [ABSTRACT FROM AUTHOR]

HCN(1–0) emission traces dense gas and correlates very strongly with star formation rates (SFRs) on scales from small Milky Way clouds to whole galaxies. The observed correlation offers strong constraints on the efficiency of star formation in dense gas, but quantitative interpretation of this constraint requires a mapping from HCN emission to gas mass and density. In this paper, we provide the required calibration by post-processing high-resolution simulations of dense, star-forming clouds to calculate their HCN emission (LHCN) and to determine how that emission is related to the underlying gas density distribution and star formation efficiency. We find that HCN emission traces gas with a luminosity-weighted mean number density of $0.8-1.7 \times 10^4 \, \mbox{cm}^{-3}$ and that HCN luminosity is related to mass of dense gas of ${\gtrsim } 10^4 \, \mbox{cm}^{-3}$ with a conversion factor of $\alpha _{\rm HCN}\approx 14\, {\rm M}_\odot /\, ({\rm K\, km\, s^{-1}\, pc^2})$. We also measure a new empirical relationship between the SFR per global mean free-fall time (εff) and the SFR–HCN relationship, SFR/ $L_{\rm HCN}\approx 2.0 \times 10^{-7}\, ({\rm \epsilon _{ff}}/0.01)^{1.1}\, {\rm M}_\odot \, {\rm yr^{-1}}/\, ({\rm K\, km\, s^{-1}\, pc^2})$. The observed SFR–HCN correlation constrains εff ≈ 1 per cent with a factor of ∼3 systematic uncertainty. The scatter in εff from cloud-to-cloud within the Milky Way is a factor of a few. We conclude that LHCN is an effective tracer of dense gas and that the IR–HCN correlation is a significant diagnostic of the microphysics of star formation in dense gas. [ABSTRACT FROM AUTHOR]

We present the sphinx suite of cosmological adaptive mesh refinement simulations, the first radiation-hydrodynamical simulations to simultaneously capture large-scale reionization and the escape of ionizing radiation from thousands of resolved galaxies. Our 5 and 10 co-moving Mpc volumes resolve haloes down to the atomic cooling limit and model the interstellar medium with better than ≈10 pc resolution. The project has numerous goals in improving our understanding of reionization and making predictions for future observations. In this first paper, we study how the inclusion of binary stars in computing stellar luminosities impacts reionization, compared to a model that includes only single stars. Owing to the suppression of galaxy growth via strong feedback, our galaxies are in good agreement with observational estimates of the galaxy luminosity function. We find that binaries have a significant impact on the timing of reionization: with binaries, our boxes are 99.9 percent ionized by volume at $$z$$ ≈ 7, while without them our volumes fail to reionize by $$z$$ = 6. These results are robust to changes in volume size, resolution, and feedback efficiency. The escape of ionizing radiation from individual galaxies varies strongly and frequently. On average, binaries lead to escape fractions of ≈7–10 percent, about three times higher than with single stars only. The higher escape fraction is a result of a shallower decline in ionizing luminosity with age, and is the primary reason for earlier reionization, although the higher integrated luminosity with binaries also plays a subdominant role. [ABSTRACT FROM AUTHOR]

The problem of influence of tidal friction in both planetary and satellite bodies upon satellite’s orbital motion is considered. Using the differential equations in satellite’s rectangular planetocentric coordinates, the differential equations describing the changes in semimajor axis and eccentricity are derived. The equations in rectangular coordinates were taken from earlier works on the problem. The calculations carried out for a number of test examples prove that the averaged solutions of equations in coordinates and precise solutions of averaged equations in the Keplerian elements are identical. For the problem of tides raised on planet’s body, it was found that, if satellite’s mean motion n is equal to $$\frac{11}{18} \Omega$$, where Ω is the planet’s angular rotation rate, the orbital eccentricity does not change. This conclusion is in agreement with the results of other authors. It was also found that there is essential discrepancy between the equations in the elements obtained in this paper and analogous equations published by earlier researchers. [ABSTRACT FROM AUTHOR]

The first stars are known to form in primordial gas, either in minihaloes with about 106 M⊙ or so-called atomic cooling haloes of about 108 M⊙. Simulations have shown that gravitational collapse and disc formation in primordial gas yield dense stellar clusters. In this paper, we focus particularly on the formation of protostellar binary systems, and aim to quantify their properties during the early stage of their evolution. For this purpose, we combine the smoothed particle hydrodynamics code gradsph with the astrochemistry package krome. The gradsph–krome framework is employed to investigate the collapse of primordial clouds in the high-density regime, exploring the fragmentation process and the formation of binary systems. We observe a strong dependence of fragmentation on the strength of the turbulent Mach number $$\mathcal {M}$$ and the rotational support parameter β. Rotating clouds show significant fragmentation, and have produced several Popualtion III proto-binary systems. We report maximum and minimum mass accretion rates of 2.31 × 10−1 and 2.18 × 10−4 M⊙ yr−1, respectively. The mass spectrum of the individual Population III proto-binary components ranges from 0.88 to 31.96 M⊙ and has a sensitive dependence on the Mach number $$\mathcal {M}$$ as well as on the rotational parameter β. We also report a range from ∼0.01 to ∼1 for the mass ratio of our proto-binary systems. [ABSTRACT FROM AUTHOR]

The empirical upper luminosity boundary L max of cool supergiants (SGs), often referred to as the Humphreys-Davidson limit, is thought to encode information on the general mass-loss behaviour of massive stars. Further, it delineates the boundary at which single stars will end their lives stripped of their hydrogen-rich envelope, which in turn is a key factor in the relative rates of Type-II to Type-Ibc supernovae from single star channels. In this paper we have revisited the issue of L max by studying the luminosity distributions of cool SGs in the Large and Small Magellanic Clouds (LMC/SMC). We assemble samples of cool SGs in each galaxy which are highly complete above log L /L⊙= 5.0, and determine their spectral energy distributions from the optical to the mid-infrared using modern multiwavelength survey data. We show that in both cases L max appears to be lower than previously quoted, and is in the region of log  L /L⊙ = 5.5. There is no evidence for L max being higher in the SMC than in the LMC, as would be expected if metallicity-dependent winds were the dominant factor in the stripping of stellar envelopes. We also show that L max aligns with the lowest luminosity of single nitrogen-rich Wolf-Rayet stars, indicating of a change in evolutionary sequence for stars above a critical mass. From population synthesis analysis we show that the Geneva evolutionary models greatly overpredict the numbers of cool SGs in the SMC. We also argue that the trend of earlier average spectral types of cool SGs in lower metallicity environments represents a genuine shift to hotter temperatures. Finally, we use our new bolometric luminosity measurements to provide updated bolometric corrections for cool SGs. [ABSTRACT FROM AUTHOR]

Understanding how bulges grow in galaxies is a critical step towards unveiling the link between galaxy morphology and star-formation. To do so, it is necessary to decompose large sample of galaxies at different epochs into their main components (bulges and discs). This is particularly challenging, especially at high redshifts, where galaxies are poorly resolved. This work presents a catalog of bulge-disc decompositions of the surface brightness profiles of ∼17.600 H-band-selected galaxies in the CANDELS fields (F 160 W < 23, 0 < $$z$$ < 2) in 4 to 7 filters covering a spectral range of 430 - 1600 $$\mathrm{nm}$$. This is the largest available catalog of this kind up to $$z$$ = 2. By using a novel approach based on deep learning to select the best model to fit, we manage to control systematics arising from wrong model selection and obtain less-contaminated samples than previous works. We show that the derived structural properties are within $${\sim }10\hbox{--}20{\rm} \, \%$$ of random uncertainties. We then fit stellar population models to the decomposed spectral energy distributions of bulges and discs and derive stellar masses (and stellar mass bulge-to-total ratios) as well as rest-frame colors (U,V,J) for bulges and discs separately. All data products are publicly released with this paper and through the web page https://lerma.obspm.fr/huertas/form_CANDELS and will be used for scientific analysis in forthcoming works. [ABSTRACT FROM AUTHOR]

In this paper, we try to understand why the classical bulge fraction observed in S0 galaxies is significantly higher than that in spiral galaxies. We carry out a comparative study of the bulge and global properties of a sample of spiral and S0 galaxies in a fixed environment. Our sample is flux limited and contains 262 spiral and 155 S0 galaxies drawn from the Sloan Digital Sky Survey. We have classified bulges into classical and pseudo-bulge categories based on their position on the Kormendy diagram. Dividing our sample into bins of galaxy stellar mass, we find that the fraction of S0 galaxies hosting a classical bulge is significantly higher than the classical bulge fraction seen in spirals even at fixed stellar mass. We have compared the bulge and the global properties of spirals and S0 galaxies in our sample and find indications that spiral galaxies which host a classical bulge, preferentially get converted into S0 population as compared to pseudo-bulge hosting spirals. By studying the star formation properties of our galaxies in the NUV−r colour–mass diagram, we find that the pseudo-bulge hosting spirals are mostly star forming while the majority of classical bulge host spirals are in the green valley or in the passive sequence. We suggest that some internal process, such as AGN feedback or morphological quenching due to the massive bulge, quenches these classical bulge hosting spirals and transforms them into S0 galaxies, thus resulting in the observed predominance of the classical bulge in S0 galaxies. [ABSTRACT FROM AUTHOR]

Stellar age assignment still represents a difficult task in Astrophysics. This unobservable fundamental parameter can be estimated only through indirect methods, as well as generally the mass. Bayesian analysis is a statistical approach largely used to derive stellar properties by taking into account the available information about the quantities we are looking for. In this paper, we propose to apply the method to the double-lined spectroscopic binaries (SB2), for which the only available information about masses is the observed mass ratio of the two components. We validated the method on a synthetic sample of pre-main-sequence (PMS) SB2 systems showing the capability of the technique to recover the simulated age and masses. Then, we applied our procedure to the PMS eclipsing binaries Parenago 1802 and RX J0529.4+0041 A, whose masses of both components are known, by treating them as SB2 systems. The estimated masses are in agreement with those dynamically measured. We conclude that the method, if based on high resolution and high signal-to-noise spectroscopy, represents a robust way to infer the masses of the very numerous SB2 systems together with their age, allowing to date the hosting astrophysical environments. [ABSTRACT FROM AUTHOR]

Current planet formation theories provide successful frameworks with which to interpret the array of new observational data in this field. However, each of the two main theories (core accretion, gravitational instability) is unable to explain some key aspects. In many planet formation calculations, it is usual to treat the initial properties of the planet-forming disc (mass, radius, etc.) as free parameters. In this paper, we stress the importance of setting the formation of planet-forming discs within the context of the formation of the central stars. By exploring the early stages of disc formation, we introduce the concept of the Maximum Mass Solar Nebula, as opposed to the oft-used minimum mass solar nebula. It is evident that almost all protoplanetary discs start their evolution in a strongly self-gravitating state. In agreement with almost all previous work in this area, we conclude that on the scales relevant to planet formation these discs are not gravitationally unstable to gas fragmentation, but instead form strong, transient spiral arms. These spiral arms can act as efficient dust traps allowing the accumulation and subsequent fragmentation of the dust (but not the gas). This phase is likely to populate the disc with relatively large planetesimals on short time-scales while the disc is still veiled by a dusty-gas envelope. Crucially, the early formation of large planetesimals overcomes the main barriers remaining within the core accretion model. A prediction of this picture is that essentially all observable protoplanetary discs are already planet hosting. [ABSTRACT FROM AUTHOR]

Bow shocks and related density enhancements produced by the winds of massive stars moving through the interstellar medium provide important information regarding the motions of the stars, the properties of their stellar winds, and the characteristics of the local medium. Since bow-shock nebulae are aspherical structures, light scattering within them produces a net polarization signal even if the region is spatially unresolved. Scattering opacity arising from free electrons and dust leads to a distribution of polarized intensity across the bow-shock structure. That polarization encodes information about the shape, composition, opacity, density, and ionization state of the material within the structure. In this paper, we use the Monte Carlo radiative transfer code SLIP to investigate the polarization created when photons scatter in a bow-shock-shaped region of enhanced density surrounding a stellar source. We present results for electron scattering, and investigate the polarization behaviour as a function of optical depth, temperature, and source of photons for two different cases: pure scattering and scattering with absorption. In both regimes, we consider resolved and unresolved cases. We discuss the implications of these results as well as their possible use along with observational data to constrain the properties of observed bow-shock systems. In different situations and under certain assumptions, our simulations can constrain viewing angle, optical depth and temperature of the scattering region, and the relative luminosities of the star and shock. [ABSTRACT FROM AUTHOR]

Deriving circular velocities of galaxies from stellar kinematics can provide an estimate of their total dynamical mass, provided a contribution from the velocity dispersion of the stars is taken into account. Molecular gas (e.g. CO), on the other hand, is a dynamically cold tracer and hence acts as an independent circular velocity estimate without needing such a correction. In this paper, we test the underlying assumptions of three commonly used dynamical models, deriving circular velocities from stellar kinematics of 54 galaxies (S0-Sd) that have observations of both stellar kinematics from the Calar Alto Legacy Integral Field Area (CALIFA) survey, and CO kinematics from the Extragalactic Database for Galaxy Evolution (EDGE) survey. We test the asymmetric drift correction (ADC) method, as well as Jeans, and Schwarzschild models. The three methods each reproduce the CO circular velocity at 1Re to within 10 per cent. All three methods show larger scatter (up to 20 per cent) in the inner regions (R < 0.4Re) that may be due to an increasingly spherical mass distribution (which is not captured by the thin disc assumption in ADC), or non-constant stellar M/L ratios (for both the JAM and Schwarzschild models). This homogeneous analysis of stellar and gaseous kinematics validates that all three models can recover Mdyn at 1Re to better than 20 per cent, but users should be mindful of scatter in the inner regions where some assumptions may break down. [ABSTRACT FROM AUTHOR]

In this paper, we investigate whether the stellar initial mass function (IMF) of early-type galaxies depends on their host environment. To this purpose, we have selected a sample of early-type galaxies from the SPIDER catalogue, characterized their environment through the group catalogue of Wang et al., and used their optical Sloan Digital Sky Survey (SDSS) spectra to constrain the IMF slope, through the analysis of IMF-sensitive spectral indices. To reach a high enough signal-to-noise ratio, we have stacked spectra in velocity dispersion (σ0) bins, on top of separating the sample by galaxy hierarchy and host halo mass, as proxies for galaxy environment. In order to constrain the IMF, we have compared observed line strengths and predictions of MIUSCAT/EMILES synthetic stellar population models, with varying age, metallicity, and 'bimodal' (low-mass tapered) IMF slope (Γb). Consistent with previous studies, we find that Γb increases with σ0, becoming bottom-heavy (i.e. an excess of low-mass stars with respect to the Milky Way like IMF) at high σ0. We find that this result is robust against the set of isochrones used in the stellar populationmodels, as well as the way the effect of elemental abundance ratios is taken into account.We thus conclude that it is possible to use currently state-of-the-art stellar population models and intermediate resolution spectra to consistently probe IMF variations. For the first time, we show that there is no dependence of Γb on environment or galaxy hierarchy, as measured within the 3 arcsec SDSS fibre, thus leaving the IMF as an intrinsic galaxy property, possibly set already at high redshift. [ABSTRACT FROM AUTHOR]

Double Periodic Variables (DPVs) are hot Algols showing a long photometric cycle of uncertain origin. We report the discovery of changes in the orbital light curve of OGLE-LMC-DPV-097 which depend on the phase of its long photometric cycle. During the ascending branch of the long cycle the brightness at the first quadrature is larger than during the second quadrature, during the maximum of the long cycle the brightness is basically the same at both quadratures, during the descending branch the brightness at the second quadrature is larger than during the first quadrature, and during the minimum of the long cycle the secondary minimum disappears. We model the light curve at different phases of the long cycle and find that the data are consistent with changes in the properties of the accretion disc and two disc spots. The disc's size and temperature change with the long-cycle period. We find a smaller and hotter disc at minimum, and larger and cooler disc at maximum. The spot temperatures, locations, and angular sizes also show variability during the long cycle. [ABSTRACT FROM AUTHOR]

The distribution of galaxies in the stellar specific angular momentum versus stellar mass plane (j* - M*) provides key insights into their formation mechanisms. In this paper, we determine the location in this plane of a sample of 10 field/group unbarred lenticular (S0) galaxies from the Calar Alto Legacy Integral Field Area survey. We performed a bulge-disc decomposition both photometrically and kinematically to study the stellar specific angular momentum of the disc components alone and understand the evolutionary links between S0s and other Hubble types. We found that eight of our S0 discs have a distribution in the j* - M* plane that is fully compatible with that of spiral discs, while only two have values of j* lower than the spirals. These two outliers show signs of recent merging. Our results suggest that merger and interaction processes are not the dominant mechanisms in S0 formation in low-density environments. Instead, S0s appear to be the result of secular processes and the fading of spiral galaxies after the shutdown of star formation. [ABSTRACT FROM AUTHOR]

The ν -ray pulsar binary system PSR B1259-63 flares in GeV after each periastron. The origin of these flares is still under debate. Recently, in 2017, we proposed a mechanism that might explain the GeV flares. In that model, a transient accretion disc is expected to be formed from the matter that was gravity-captured by the neutron star from the main-sequence companion's circumstellar disc. The transient accretion disc exerts a spin-down torque on the neutron star (i.e. the propeller effect), which might be traceable via pulsar timing observations of PSR B1259-63. In this paper, we consider the propeller effect phenomenologically using a parameter x, which describes the coupling between the disc matter and the neutron star. Comparing the expected timing residuals with recent observations by Shannon et al., we conclude that the angular momentum transfer is very weak (with the coupling parameter x = 10-4). [ABSTRACT FROM AUTHOR]

(Sub)halo abundance matching (SHAM) assumes that one (sub) halo property, such as mass Mvir or peak circular velocity Vpeak, determines properties of the galaxy hosted in each (sub) halo such as its luminosity or stellar mass. This assumption implies that the dependence of galaxy luminosity functions (GLFs) and the galaxy stellar mass function (GSMF) on environmental density is determined by the corresponding halo density dependence. In this paper, we test this by determining from a Sloan Digital Sky Survey sample the observed dependence with environmental density of the ugriz GLFs and GSMF for all galaxies, and for central and satellite galaxies separately. We then show that the SHAM predictions are in remarkable agreement with these observations, even when the galaxy population is divided between central and satellite galaxies. However, we show that SHAM fails to reproduce the correct dependence between environmental density and g - r colour for all galaxies and central galaxies, although it better reproduces the colour dependence on environmental density of satellite galaxies. [ABSTRACT FROM AUTHOR]