Upper Mass Limit Research Articles

Using action space clustering to constrain the recent accretion history of Milky Way-like galaxies

ABSTRACT In the currently favoured cosmological paradigm galaxies form hierarchically through the accretion of satellites. Since a satellite is less massive than the host, its stars occupy a smaller volume in action space. Actions are conserved when the potential of the host halo changes adiabatically, so stars from an accreted satellite would remain clustered in action space as the host evolves. In this paper, we identify recently disrupted accreted satellites in three Milky Way-like disc galaxies from the cosmological baryonic FIRE-2 simulations by tracking satellites through simulation snapshots. We try to recover these satellites by applying the cluster analysis algorithm Enlink to the orbital actions of accreted star particles in the z = 0 snapshot. Even with completely error-free mock data we find that only 35 per cent (14/39) satellites are well recovered while the rest (25/39) are poorly recovered (i.e. either contaminated or split up). Most (10/14 ∼70 per cent) of the well-recovered satellites have infall times <7.1 Gyr ago and total mass >4 × 108M⊙ (stellar mass more than 1.2 × 106 M⊙, although our upper mass limit is likely to be resolution dependent). Since cosmological simulations predict that stellar haloes include a population of in situ stars, we test our ability to recover satellites when the data include 10–50 per cent in situ contamination. We find that most previously well-recovered satellites stay well recovered even with 50 per cent contamination. With the wealth of 6D phase space data becoming available we expect that cluster analysis in action space will be useful in identifying the majority of recently accreted and moderately massive satellites in the Milky Way.

Supermassive stars with random transverse magnetic fields

ABSTRACT Gravitational dynamic collapses of supermassive stars (SMSs) triggered at certain critical stages may give rise to black holes (BHs) in a broad mass range that populate the Universe including the early Universe. SMSs have been speculated as the progenitors or seeds of supermassive BHs that power quasars and active galactic nuclei. We study quasi-spherical magnetostatic equilibria and magnetohydrodynamic (MHD) radial pulsational (in)stability properties of non-rotating SMSs involving random transverse magnetic fields (RTMFs) using the general relativity (GR). With RTMFs, the maxima of the gravitational binding energy mark the GR MHD transition from stability to instability and the RTMF does not modify the GR stability criterion significantly when the ratio ${\cal M}/\left|\Omega \right|\lesssim0.1$, where $\cal M$ is the total magnetic energy and Ω is the total gravitational potential energy. When $0.1\lesssim{\cal M}/\left|\Omega \right|\lesssim1$, nevertheless, the critical GR magnetostatic equilibria on the verge of GR MHD collapses or explosions may change drastically, raising the upper mass limit at the onset of GR MHD instability from ∼105 to ∼106 M⊙ and even higher. For ${\cal M}/\left|\Omega \right|\sim 1$, the evolution track of magnetized SMS is shifted towards the redder part of the Hertzsprung–Russell diagram, featuring a sort of ‘magnetic reddening’ associated with the stellar ‘magnetized envelope inflation’. By estimates, the RTMF energy stored in an SMS can be as large as ∼1057 erg, enough to power gamma-ray bursts, fast radio bursts, or other forms of powerful electromagnetic wave bursts. It is possible for magnetized massive stars to dynamically form BHs in the mass range from several tens to thousands of solar masses without necessarily triggering the central electron-positron e± instability inside such stars – this fact is highly pertinent to the reports of LIGO-Virgo gravitational wave event scenario of binary BH mergers.

Egg Incubation Mechanics of Giant Birds

Simple SummaryExtinct giant birds have been a source of imagination, and knowledge of their incubation mechanics is crucial to our understanding of the evolution of avian reproduction. Despite the extensive studies on avian eggs, our understanding of the eggshell mechanics of giant birds, particularly the extinct ones, remains incomplete—most of these prior works were based on empirical or allometric relationships with limited quantitative analysis. In the present study, with the help of advanced three-dimensional computer simulation using data from published fossil records, we obtain more comprehensive quantitative analysis to answer important questions related to contact incubation of giant birds. Specifically, how much safety margin does the reversed sexual size dimorphism (RSSD) of moas provide? What is the theoretical upper limit of body mass for contact incubation? Is the Williams’ egg, or the putative Genyornis oological material (PGOM), really the egg of the extinct giant bird Genyornis newtoni, as commonly accepted since its discovery in 1981?Finite element analysis (FEA) was used to conduct mechanical analyses on eggshells of giant birds, and relate this to the evolution and reproductive behavior of avian species. We aim to (1) investigate mechanical characteristics of eggshell structures of various ratite species, enabling comparisons between species with or without reversed sexual size dimorphism (RSSD); (2) quantify the safety margin provided by RSSD; (3) determine whether the Williams’ egg can have been incubated by an extinct giant bird Genyornis newtoni; (4) determine the theoretical maximum body mass for contact incubation. We use a dimensionless number C to quantify relative shell stiffness with respect to the egg size, allowing for comparison across wide body masses. We find that RSSD in moas significantly increases the safety margin of contact incubation by the lighter males. However, their safety margins are still smaller than those of the moa species without RSSD. Two different strategies were adopted by giant birds—one is RSSD and thinner shells, represented by some moa species; the other is no RSSD and regular shells, represented by the giant elephant bird. Finally, we predicted that the upper limit of body mass for contact incubation was 2000 kg.

The Tarantula Massive Binary Monitoring

Context. The evolution of the most massive stars and their upper-mass limit remain insufficiently constrained. Very massive stars are characterized by powerful winds and spectroscopically appear as hydrogen-rich Wolf–Rayet (WR) stars on the main sequence. R 144 is the visually brightest WR star in the Large Magellanic Cloud. R 144 was reported to be a binary, making it potentially the most massive binary observed yet. However, the orbit and properties of R 144 have yet to be established. Aims. Our aim is to derive the physical, atmospheric, and orbital parameters of R 144 and to interpret its evolutionary status. Methods. We performed a comprehensive spectral, photometric, orbital, and polarimetric analysis of R 144. We measured radial velocities via cross-correlation. Spectral disentangling was performed using the shift-and-add technique. We used the Potsdam Wolf–Rayet code for the spectral analysis. We further present X-ray and optical light curves of R 144, and we analyse the latter using a hybrid model combining wind eclipses and colliding winds to constrain the orbital inclination i. Results. R 144 is an eccentric (e = 0.51) 74.2−d binary comprising two relatively evolved (age ≈2 Myr), H-rich WR stars (surface mass fraction XH ≈ 0.4). The hotter primary (WN5/6h, T* = 50 kK) and the cooler secondary (WN6/7h, T* = 45 kK) have nearly equal masses of M sin3 i = 48.3 ± 1.8 M⊙ and 45.5 ± 1.9 M⊙, respectively. The combination of low rotation and H depletion observed in the system is reproduced well by contemporary evolution models that include boosted mass loss at the upper-mass end. The systemic velocity of R 144 and its relative isolation suggest that this binary was ejected as a runaway from the neighbouring R 136 cluster. The optical light curve shows a clear orbital modulation that can be explained as a combination of two processes: excess emission stemming from wind-wind collisions and double wind eclipses. Our light-curve model implies an orbital inclination of i = 60.4 ± 1.5°, resulting in accurately constrained dynamical masses of M1,dyn = 74 ± 4 M⊙ and M2,dyn = 69 ± 4 M⊙. Assuming that both binary components are core H-burning, these masses are difficult to reconcile with the derived luminosities (log L1,2∕L⊙ = 6.44, 6.39), which correspond to evolutionary masses of the order of M1, ev ≈ 110 M⊙ and M2, ev ≈ 100 M⊙. Taken at face value, our results imply that both stars have high classical Eddington factors of Γe = 0.78 ± 0.10. If the stars are on the main sequence, their derived radii (R* ≈ 25 R⊙) suggest that they are only slightly inflated, even at this high Eddington factor. Alternatively, the stars could be core He-burning, strongly inflated from the regular size of classical WR stars (≈ 1 R⊙); this scenario could help resolve the observed mass discrepancy. Conclusions. R144 is one of the few very massive extragalactic binaries ever weighed without the usage of evolution models, but poses several challenges in terms of the measured masses of its components. To advance, we strongly advocate for future polarimetric, photometric, and spectroscopic monitoring of R 144 and other very massive binaries.

Wandering of the central black hole in a galactic nucleus and correlation of the black hole mass with the bulge mass

Abstract We investigate a mechanism for a super-massive black hole at the center of a galaxy to wander in the nucleus region. A situation is supposed in which the central black hole tends to move by the gravitational attractions from the nearby molecular clouds in a nuclear bulge but is braked via the dynamical frictions from the ambient stars there. We estimate the approximate kinetic energy of the black hole in an equilibrium between the energy gain rate through the gravitational attractions and the energy loss rate through the dynamical frictions in a nuclear bulge composed of a nuclear stellar disk and a nuclear stellar cluster as observed from our Galaxy. The wandering distance of the black hole in the gravitational potential of the nuclear bulge is evaluated to get as large as several 10 pc, when the black hole mass is relatively small. The distance, however, shrinks as the black hole mass increases, and the equilibrium solution between the energy gain and loss disappears when the black hole mass exceeds an upper limit. As a result, we can expect the following scenario for the evolution of the black hole mass: When the black hole mass is smaller than the upper limit, mass accretion of the interstellar matter in the circumnuclear region, causing the AGN activities, makes the black hole mass larger. However, when the mass gets to the upper limit, the black hole loses the balancing force against the dynamical friction and starts spiraling downward to the gravity center. From simple parameter scaling, the upper mass limit of the black hole is found to be proportional to the bulge mass, and this could explain the observed correlation of the black hole mass with the bulge mass.

Studying the parameters of the extended \u03c3-\u03c9 model for neutron star matter

In this work we study the parameters of the extended σ-ω model for neutron star matter by a Bayesian analysis of state-of-the-art multi-messenger astronomy observations, namely mass, radius and tidal deformabilities. We have considered three parameters of the model, the Landau mass mL, the nuclear compressibility K0, and the value of the symmetry energy S0, all at saturation density n0. As a result, we are able to estimate the best values of the Landau mass of mL ≈ 0.73 GeV, whereas the values of K0 and S0 fall within already known empirical values. Furthermore, for neutron stars we find the most probable value of 13 km < R1.4 < 13.5 km and the upper mass limit of Mmax ≈ 2.2 M⊙.

A Mini-Neptune and a Radius Valley Planet Orbiting the Nearby M2 Dwarf TOI-1266 in Its Venus Zone: Validation with the Habitable-zone Planet Finder

Abstract We report on the validation of two planets orbiting the nearby (36 pc) M2 dwarf TOI-1266 observed by the TESS mission. This system is one of a few M dwarf multiplanet systems with close-in planets where the inner planet is substantially larger than the outer planet. The inner planet is sub-Neptune-sized (R = 2.46 ± 0.08 R ⊕) with an orbital period of 10.9 days, while the outer planet has a radius of R ⊕ and resides in the exoplanet radius valley—the transition region between rocky and gaseous planets. With an orbital period of 18.8 days, the outer planet receives an insolation flux of 2.4 times that of Earth, similar to the insolation of Venus. Using precision near-infrared radial velocities with the Habitable-zone Planet Finder Spectrograph, we place upper mass limits of 15.9 and 6.4 M ⊕ at 95% confidence for the inner and outer planet, respectively. A more precise mass constraint of both planets, achievable with current radial velocity instruments given the host star brightness (V = 12.9, J = 9.7), will yield further insights into the dominant processes sculpting the exoplanet radius valley.

On highly accurate, bound state calculations of the molecular diatomic ions

Results of highly accurate calculations obtained recently for a number of Coulomb two-centre ions with the unit electrical charges and are presented. In particular, we have determined (to very high accuracy) the total energies and other bound state properties of the ground (bound) states in the two-centre adiabatic (or molecular) H, D, HD, HT, T and DT ions. In these computations we used the new masses of hydrogen isotopes, which have been measured in recent high-energy experiments. Theory of soft adiabatic three-body systems with the unit electrical charges is also discussed. An accurate mass-interpolation formula is derived and tested for the total energies of model two-centre ions with very heavy masses of the point particles ( 100,000 ). This formula allows one to evaluate (to high accuracy) the total energies and other bound state properties of arbitrary two-centre ions, including very heavy systems. We also determine the upper mass limit for applicability of our universal expansion in the relative and/or perimetric coordinates. Highlights An effective procedure is developed for highly accurate numerical computations of bound states in the two-center molecular ions. Properties of many actual two-center ions, including the both and ions, have been determined to very high accuracy. Theory of the soft adiabatic (two-center) three-body systems is developed. Properties of these ions are now known to high accuracy. Accurate numerical method which allows one to predict the total energies and other properties of truly adiabatic systems with very large (or infinite) nuclear masses has been proposed, applied and studied in detail.

Investigating gravitational collapse of a pebble cloud to form transneptunian binaries

Context. A large fraction of transneptunian objects are found in binary pairs, ~30% in the cold classical population between ahel ~ 39 and ~48 AU. Observationally, these binaries generally have components of similar size and colour. Previous work has shown that gravitational collapse of a pebble cloud is an efficient mechanism for producing such systems. Since the bi-lobate nature of 2014 MU69 (Arrokoth) was discovered, interest in gravitational collapse as a pathway for forming contact binaries has also grown. Aims. We investigate the formation of binary systems through gravitational collapse by considering a wider range of binary masses than previous studies. We analysed in detail the properties of the bound systems that are formed and compared them to observations. Methods. We performed N-body simulations of gravitational collapse of a pebble cloud using the REBOUND package, with an integrator designed for rotating reference frames and robust collision detection. We conducted a deep search for gravitationally bound particles at the end of the gravitational collapse phase and tested their stability. For all systems produced, not just for the most massive binaries, we investigated the population characteristics of their mass and orbital parameters. Results. We found that gravitational collapse is an efficient producer of bound planetesimal systems. On average, about 1.5 bound systems were produced per cloud in the mass range studied here. In addition to large equal-sized binaries, we found that gravitational collapse produces massive bodies with small satellites and low-mass binaries with a high mass ratio. Our results disfavour the collapse of high-mass clouds, in line with reported upper mass limits of clouds formed by the streaming instability. Gravitational collapse can create binary systems analogous to Arrokoth, and collisions in a collapsing cloud should be gentle enough to preserve a bi-lobed structure.

THE ADF AND THE t2 FORMALISM IN H II REGIONS BASED ON THE UPPER MASS LIMIT OF THE IMF FOR THE MW

We study in depth the abundance discrepancy problem in H II regions, this time from a different perspective than the usual one: by studying the effect of the upper mass limit (Mup) of the initial mass function (IMF) on the O, C, and He predicted by chemical evolution models for the Milky Way. We use abundances determined with the direct method (DM) and with the temperature independent method (TIM). We compare the predicted abundances at the present time with observations of Orion, M17, and M8 to determine the Mup value of the galactic IMF. From the DM abundances, the models predict an Mup = 25 − 45 M⨀, while from the TIM, CEMs derive an Mup = 70 − 110 M⨀. Spiral galaxies with the stellar mass and star formation rate of the MW are predicted to have an Mup ≈ 100 M⨀. These results support that abundances derived from the TIM are better than those derived from the DM.

Inferring the maximum and minimum mass of merging neutron stars with gravitational waves

We show that the maximum and the minimum mass of merging neutron stars can be estimated with upcoming gravitational wave observations. We simulate populations of binary neutron star signals and model their mass distribution including upper and lower cutoffs. The lower(upper) limit can be measured to $\sim 0.2(0.1)\text{M}_{\odot}$ with $50$ detections if the mass distribution supports neutron stars with masses close to the cutoffs. The upper mass limit informs about the high density properties of the neutron star equation of state, while the lower limit signals the divide between neutron stars and white dwarfs.

Effects of dark matter on the upper bound mass of neutron stars

Abstract Observations have indicated that we do not see neutron stars (NS) of mass near the theoretical upper limit as predicted. Here we invoke the role of dark matter (DM) particles in star formation, and their role in lowering the mass of remnants eventually formed from these stars. Massive stars can capture DM particles more effectively than the lower mass stars, thus further softening the equation of state of the remnant neutron stars. We also look at the capture of DM particles by the NS, which could further soften the upper mass limit of NS. The admixture of DM particles would be higher at earlier epochs (high z).

Mass determinations of the three mini-Neptunes transiting TOI-125

ABSTRACT The Transiting Exoplanet Survey Satellite, TESS, is currently carrying out an all-sky search for small planets transiting bright stars. In the first year of the TESS survey, a steady progress was made in achieving the mission’s primary science goal of establishing bulk densities for 50 planets smaller than Neptune. During that year, the TESS’s observations were focused on the southern ecliptic hemisphere, resulting in the discovery of three mini-Neptunes orbiting the star TOI-125, a V = 11.0 K0 dwarf. We present intensive HARPS radial velocity observations, yielding precise mass measurements for TOI-125b, TOI-125c, and TOI-125d. TOI-125b has an orbital period of 4.65 d, a radius of 2.726 ± 0.075 RE, a mass of 9.50 ± 0.88 ME, and is near the 2:1 mean motion resonance with TOI-125c at 9.15 d. TOI-125c has a similar radius of 2.759 ± 0.10 RE and a mass of 6.63 ± 0.99 ME, being the puffiest of the three planets. TOI-125d has an orbital period of 19.98 d and a radius of 2.93 ± 0.17 RE and mass 13.6 ± 1.2 ME. For TOI-125b and d, we find unusual high eccentricities of 0.19 ± 0.04 and $0.17^{+0.08}_{-0.06}$, respectively. Our analysis also provides upper mass limits for the two low-SNR planet candidates in the system; for TOI-125.04 (RP = 1.36 RE, P = 0.53 d), we find a 2σ upper mass limit of 1.6 ME, whereas TOI-125.05 ($R_P=4.2^{+2.4}_{-1.4}$ RE, P = 13.28 d) is unlikely a viable planet candidate with an upper mass limit of 2.7 ME. We discuss the internal structure of the three confirmed planets, as well as dynamical stability and system architecture for this intriguing exoplanet system.

The ‘red supergiant problem’: the upper luminosity boundary of Type II supernova progenitors

ABSTRACT By comparing the properties of red supergiant (RSG) supernova (SN) progenitors to those of field RSGs, it has been claimed that there is an absence of progenitors with luminosities L above log (L/L⊙) &amp;gt; 5.2. This is in tension with the empirical upper luminosity limit of RSGs at log (L/L⊙) = 5.5, a result known as the ‘RSG problem’. This has been interpreted as an evidence for an upper mass threshold for the formation of black holes. In this paper, we compare the observed luminosities of RSG SN progenitors with the observed RSG L-distribution in the Magellanic Clouds. Our results indicate that the absence of bright SN II-P/L progenitors in this sample can be explained at least in part by the steepness of the L-distribution and a small sample size, and that the statistical significance of the RSG problem is between 1σ and 2σ . Secondly, we model the luminosity distribution of II-P/L progenitors as a simple power law with an upper and lower cut-off, and find an upper luminosity limit of $\log (L_{\rm hi}/\mathrm{L}_\odot) = 5.20^{+0.17}_{-0.11}$ (68 per cent confidence), though this increases to ∼5.3 if one fixes the power-law slope to be that expected from theoretical arguments. Again, the results point to the significance of the RSG problem being within ∼2σ. Under the assumption that all progenitors are the result of single-star evolution, this corresponds to an upper mass limit for the parent distribution of $M_{\rm hi} = 19.2\, {\rm M_\odot }$, $\pm 1.3 \, {\rm M_\odot (systematic)}$, $^{+4.5}_{-2.3} \, {\rm M_\odot }$ (random; 68 per cent confidence limits).

Missing red supergiants and carbon burning

ABSTRACT Recent studies on direct imaging of Type II core-collapse supernova progenitors indicate a possible threshold around MZAMS ∼ 16–20 M⊙, where red supergiants (RSG) with larger birth masses do not appear to result in supernova explosions and instead implode directly into a black hole. In this study, we argue that it is not a coincidence that this threshold closely matches the critical transition of central carbon burning in massive stars from the convective to radiative regime. In lighter stars, carbon burns convectively in the centre and result in compact final pre-supernova cores that are likely to result in explosions, while in heavier stars after the transition, it burns as a radiative flame and the stellar cores become significantly harder to explode. Using the $\rm {\small {kepler}}$ code we demonstrate the sensitivity of this transition to the rate of 12C(α, γ)16O reaction and the overshoot mixing efficiency, and we argue that the upper mass limit of exploding RSG could be employed to constrain uncertain input physics of massive stellar evolution calculations. The initial mass corresponding to the central carbon burning transition range from 14 to 26 M⊙ in recently published models from various groups and codes, and only a few are in agreement with the estimates inferred from direct imaging studies.

ALMA and NACO observations towards the young exoring transit system J1407 (V1400 Cen)

Aims. Our aim was to directly detect the thermal emission of the putative exoring system responsible for the complex deep transits observed in the light curve for the young Sco-Cen star 1SWASP J140747.93-394542.6 (V1400 Cen, hereafter J1407), confirming it as the occulter seen in May 2007, and to determine its orbital parameters with respect to the star. Methods. We used the Atacama Large Millimeter/submillimeter Array (ALMA) to observe the field centred on J1407 in the 340 GHz (Band 7) continuum in order to determine the flux and astrometric location of the ring system relative to the star. We used the VLT/NACO camera to observe the J1407 system in March 2019 and to search for the central planetary mass object at thermal infrared wavelengths. Results. We detect no point source at the expected location of J1407, and derive an upper limit 3σ level of 57.6 μJy. There is a point source detected at an angular separation consistent with the expected location for a free-floating ring system that occulted J1407 in May 2007, with a flux of 89 μJy consistent with optically thin dust surrounding a massive substellar companion. At 3.8 μm with the NACO camera, we detect the star J1407 but no other additional point sources within 1.3 arcsec of the star, with a lower bound on the sensitivity of 6 MJup at the location of the ALMA source, and down to 4 MJup in the sky background limit. Conclusions. The ALMA upper limit at the location of J1407 implies that a hypothesised bound ring system is composed of dust smaller than 1 mm in size, implying a young ring structure. The detected ALMA source has multiple interpretations, including: (i) it is an unbound substellar object surrounded by warm dust in Sco-Cen with an upper mass limit of 6 MJup, or (ii) it is a background galaxy.

The initial mass function in the extended ultraviolet disc of M83

ABSTRACT Using Hubble Space Telescope ACS/WFC data we present the photometry and spatial distribution of resolved stellar populations of four fields within the extended ultraviolet disc (XUV disc) of M83. These observations show a clumpy distribution of main-sequence stars and a mostly smooth distribution of red giant branch stars. We constrain the upper end of the initial mass function (IMF) in the outer disc using the detected population of main-sequence stars and an assumed constant star formation rate (SFR) over the last 300 Myr. By comparing the observed main-sequence luminosity function to simulations, we determine the best-fitting IMF to have a power-law slope α = −2.35 ± 0.3 and an upper mass limit $M_{\rm u}=25_{-3}^{+17} \, \mathrm{M}_\odot$. This IMF is consistent with the observed H $\rm \alpha$ emission, which we use to provide additional constraints on the IMF. We explore the influence of deviations from the constant SFR assumption, finding that our IMF conclusions are robust against all but strong recent variations in SFR, but these are excluded by causality arguments. These results, along with our similar studies of other nearby galaxies, indicate that some XUV discs are deficient in high-mass stars compared to a Kroupa IMF. There are over one hundred galaxies within 5 Mpc, many already observed with HST, thus allowing a more comprehensive investigation of the IMF, and how it varies, using the techniques developed here.

Skeletal muscle mass in female athletes: The average and the extremes.

To examine the absolute and relative skeletal muscle mass (SM) in female athletes and to discuss the potential upper limit of whole-body muscle mass between large sized female and male athletes. Forty-five female athletes and forty-five recreationally active females (control) had muscle thickness measured by ultrasound at nine sites on the anterior and posterior aspects of the body. SM was estimated from an ultrasound-derived prediction equation. Body fat percentage and fat-free mass (FFM) were calculated from ultrasound measured subcutaneous fat thickness. To eliminate fat-free component of adipose tissue (FFAT), we calculated FFM minus FFAT (FFM-FFAT). FFM, FFM-FFAT, and muscle mass were markedly higher in athletes. Fat Mass was similar (Athlete: 14.9 kg vs Control: 12.9 kg [median value]). The large-sized female athletes had approximately 9 to 11 kg FFAT which corresponds to about 10% to 15% of FFM. Seven of the female athletes had more than 60 kg of FFM-FFAT, the largest of whom had 77.0 kg of FFM-FFAT. SM increased in a parabolic fashion reaching a value of 35 kg SM beyond 100 kg body mass. Only one of the athletes had a SM index of more than 13 kg/m2 . Female athletes had much greater muscle mass than controls. In large-sized female athletes, the influence of FFAT needs to be considered when interpreting their FFM. In addition, the largest SM index in female athletes was 13.2 kg/m2 , which was approximately 77% of that observed with the largest male athlete ever recorded. This difference appears similar to that observed in nonathletes.

Detection and characterisation of 54 massive companions with the SOPHIE spectrograph

Context. Brown dwarfs (BD) are substellar objects intermediate between planets and stars with masses of ~13–80 MJ. While isolated BDs are most likely produced by gravitational collapse in molecular clouds down to masses of a few MJ, a non-negligible fraction of low-mass companions might be formed through the planet-formation channel in protoplanetary discs. The upper mass limit of objects formed within discs is still observationally unknown, the main reason being the strong dearth of BD companions at orbital periods shorter than 10 yr, also known as the BD desert. Aims. To address this question, we aim at determining the best statistics of companions within the 10–100 MJ mass regime and located closer than ~10 au to the primary star, while minimising observation and selection bias. Methods. We made extensive use of the radial velocity (RV) surveys of northern hemisphere FGK stars within 60 pc of the Sun, performed with the SOPHIE spectrograph at the Observatoire de Haute-Provence. We derived the Keplerian solutions of the RV variations of 54 sources. Public astrometric data of the HIPPARCOS and Gaia missions allowed us to constrain the masses of the companions for most sources. We introduce GASTON, a new method to derive inclination combining RVs and Keplerian and astrometric excess noise from Gaia DR1. Results. We report the discovery of 12 new BD candidates. For five of them, additional astrometric data led to a revision of their mass in the M-dwarf regime. Among the seven remaining objects, four are confirmed BD companions, and three others are likely also in this mass regime. Moreover, we report the detection of 42 M-dwarfs within the range of 90 MJ–0.52 M⊙. The resulting M sin i-P distribution of BD candidates shows a clear drop in the detection rate below 80-day orbital period. Above that limit, the BD desert appears rather wet, with a uniform distribution of the M sin i. We derive a minimum BD-detection frequency around Solar-like stars of 2.0 ± 0.5%.

A Break in Spiral Galaxy Scaling Relations at the Upper Limit of Galaxy Mass

Abstract Super spirals are the most massive star-forming disk galaxies in the universe. We measured rotation curves for 23 massive spirals with the Southern African Large Telescope (SALT) and found a wide range of fast rotation speeds (240–570 km s−1), indicating enclosed dynamical masses of (0.6−4) × 1012 M ⊙. Super spirals with mass in stars log M stars / M ⊙ &gt; 11.5 break from the baryonic Tully–Fisher relation (BTFR) established for lower-mass galaxies. The BTFR power-law index breaks from 3.75 ± 0.11 to 0.25 ± 0.41 above a rotation speed of ∼340 km s−1. Super spirals also have very high specific angular momenta that break from the Fall relation. These results indicate that super spirals are undermassive for their dark matter halos, limited to a mass in stars of log M stars / M ⊙ &lt; 11.8 . Most giant elliptical galaxies also obey this fundamental limit, which corresponds to a critical dark halo mass of log M halo / M ⊙ ≃ 12.7 . Once a halo reaches this mass, its gas can no longer cool and collapse in a dynamical time. Super spirals survive today in halos as massive as log M halo / M ⊙ ≃ 13.6 , continuing to form stars from the cold baryons they captured before their halos reached critical mass. The observed high-mass break in the BTFR is inconsistent with the Modified Newtonian Dynamics theory.