The cosmic merger rate density of compact objects: impact of star formation, metallicity, initial mass function and binary evolution

We evaluate the redshift distribution of binary black hole (BBH), black hole - neutron star binary (BHNS) and binary neutron star (BNS) mergers, exploring the main sources of uncertainty: star formation rate (SFR) density, metallicity evolution, common envelope, mass transfer via Roche lobe overflow, natal kicks, core-collapse supernova model and initial mass function. Among binary evolution processes, uncertainties on common envelope ejection have a major impact: the local merger rate density of BNSs varies from $\sim{}10^3$ to $\sim{}20$ Gpc$^{-3}$ yr$^{-1}$ if we change the common envelope efficiency parameter from $\alpha_{\rm CE}=7$ to 0.5, while the local merger rates of BBHs and BHNSs vary by a factor of $\sim{}2-3$. The BBH merger rate changes by one order of magnitude, when $1 \sigma$ uncertainties on metallicity evolution are taken into account. In contrast, the BNS merger rate is almost insensitive to metallicity. Hence, BNSs are the ideal test bed to put constraints on uncertain binary evolution processes, such as common envelope and natal kicks. Only models assuming values of $\alpha_{\rm CE}\gtrsim{}2$ and moderately low natal kicks (depending on the ejected mass and the SN mechanism), result in a local BNS merger rate density within the 90% credible interval inferred from the second gravitational-wave transient catalogue.Comment: 14 pages, 12 figures, 2 tables, accepted for publication in MNRA

Host galaxies of merging compact objects: mass, star formation rate, metallicity, and colours

Characterizing the properties of the host galaxies of merging compact objects provides essential clues to interpret current and future gravitational-wave detections. Here, we investigate the stellar mass, star formation rate (SFR), metallicity, and colours of the host galaxies of merging compact objects in the local Universe by combining the results of MOBSE population-synthesis models together with galaxy catalogues from the EAGLE simulation. We predict that the stellar mass of the host galaxy is an excellent tracer of the merger rate per galaxy n(GW) of double neutron stars (DNSs), double black holes (DBHs), and black hole-neutron star binaries (BHNSs). We find a significant correlation also between n(GW) and SFR. As a consequence, n(GW) correlates also with the r-band luminosity and with the g-r colour of the host galaxies. Interestingly, greater than or similar to 60 per cent, greater than or similar to 64 per cent, and greater than or similar to 73 per cent of all the DNSs, BHNSs, and DBHs merging in the local Universe lie in early-type galaxies, such as NGC 4993. We predict a local DNS merger rate density of similar to 238 Gpc(-3) yr(-1) and a DNS merger rate similar to 16-121 Myr(-1) for Milky Way-like galaxies. Thus, our results are consistent with both the DNS merger rate inferred from GW170817 and the one inferred from Galactic DNSs

Dynamics of black hole-neutron star binaries in young star clusters

Young star clusters are likely the most common birthplace of massive stars across cosmic time and influence the formation of compact binaries in several ways. Here, we simulate the formation of black hole-neutron star binaries (BHNSs) in young star clusters, by means of the binary population synthesis code MOBSE interfaced with the N-body code NBODY6++GPU. BHNSs formed in young star clusters (dynamical BHNSs) are significantly more massive than BHNSs formed from isolated binaries (isolated BHNSs): ~40 per cent of the dynamical BHNS mergers have a total mass of > 15 M0, while only ~0.01 per cent of the isolated BHNS mergers have mass in excess of this value. Hence, our models strongly support a dynamical formation scenario for GW190814, given its total mass of ~26 M0, if this event is a BHNS merger. All our dynamical BHNSs are ejected from their parent star cluster before they reach coalescence. Thus, a significant fraction of BHNS mergers occurring in the field might have originated in a young star cluster. The mass spectrum of BHNS mergers from gravitational-wave detections will provide a clue to differentiate between dynamical and isolated formation of BHNSs

New insights on binary black hole formation channels after GWTC-2: young star clusters versus isolated binaries

With the recent release of the second gravitational-wave transient catalogue (GWTC-2), which introduced dozens of new detections, we are at a turning point of gravitational wave astronomy, as we are now able to directly infer constraints on the astrophysical population of compact objects. Here, we tackle the burning issue of understanding the origin of binary black hole (BBH) mergers. To this effect, we make use of state-of-the-art population synthesis and N-body simulations, to represent two distinct formation channels: BBHs formed in the field (isolated channel) and in young star clusters (dynamical channel). We then use a Bayesian hierarchical approach to infer the distribution of the mixing fraction $f$, with $f=0$ ($f=1$) in the pure dynamical (isolated) channel. %that controls the proportion of isolated and dynamical BBHs. We explore the effects of additional hyper-parameters of the model, such as the spread in metallicity $\sigma_{\text{Z}}$ and the parameter $\sigma_{\text{sp}}$, describing the distribution of spin magnitudes. We find that the dynamical model is slightly favoured with a median value of $f=0.26$, when $\sigma_{\text{sp}}=0.1$ and $\sigma_{\text{Z}}=0.4$. Models with higher spin magnitudes tend to strongly favour dynamically formed BBHs ($f\le{}0.1$ if $\sigma_{\text{sp}}=0.3$). Furthermore, we show that hyper-parameters controlling the rates of the model, such as $\sigma_{\rm Z}$, have a large impact on the inference of the mixing fraction, which rises from $0.18$ to $0.43$ when we increase $\sigma_{\text{Z}}$ from 0.2 to 0.6, for a fixed value of $\sigma_{\text{sp}}=0.1$. Finally, our current set of observations is better described by a combination of both formation channels, as a pure dynamical scenario is excluded at the $99\%$ credible interval, except when the spin magnitude is high.Comment: 13 pages, 10 figures, 2 tables, published in MNRA

Treatment decision-making of secondary prevention after venous thromboembolism. data from the real-life START2-POST-VTE register

Patients with venous thromboembolism (VTE) should receive a decision on the duration of anticoagulant treatment (AT) that is often not easy to make. Sixteen Italian clinical centers included patients with recent VTE in the START2-POST-VTE register and reported the decisions taken on duration of AT in each patient and the reasons for them. At the moment of this report, 472 (66.9%) of the 705 patients included in the registry were told to stop AT in 59.3% and to extend it in 40.7% of patients. Anticoagulant treatment lasted ≥3 months in >90% of patients and was extended in patients with proximal deep vein thrombosis because considered at high risk of recurrence or had thrombophilic abnormalities. d-dimer testing, assessment of residual thrombus, and patient preference were also indicated among the criteria influencing the decision. In conclusion, Italian doctors stuck to the minimum 3 months AT after VTE, while the secondary or unprovoked nature of the event was not seen as the prevalent factor influencing AT duration which instead was the result of a complex and multifactorial evaluation of each patient

Association between plasma omentin-1 levels in type 2 diabetic patients and peripheral artery disease.

BACKGROUND: Type-2 diabetes mellitus is one of the major risk factors of atherosclerosis, particularly in peripheral artery disease (PAD). Several studies have documented a correlation between omentin-1 serum levels, atherosclerosis, and cardiovascular diseases. However, a clear link between circulating omentin-1 and PAD in diabetic patients has yet to be established. The aim of this study was to investigate the potential role of omentin-1 in PAD in type-2 diabetic patients. METHODS: In this cross-sectional study, we analyzed omentin-1 serum levels by ELISA in 600 type-2 diabetic patients with (n = 300) and without (n = 300) PAD at Fontaine's stage II, III, or IV. RESULTS: We found that omentin-1 serum levels were significantly lower in diabetic patients with PAD than in diabetic controls (29.46 vs 49.24 ng/mL, P < 0.001) and that the levels gradually decreased in proportion to disease severity (P < 0.05). The association between omentin-1 levels and PAD remained significant after adjusting for major risk factors in a multivariate analysis. CONCLUSIONS: Our results suggest that omentin-1 is reduced in type 2 diabetic patients with PAD and that omentin-1 levels are related to disease severity

Exercise and Protein Intake: A Synergistic Approach against Sarcopenia

Sarcopenia, the age-dependent loss of muscle mass and function/strength, is increasingly recognized as a major risk factor for adverse outcomes in frail older people. As such, the skeletal muscle is a relevant target for interventions aimed at preventing or postponing the occurrence of negative health-related events in late life. The association among physical inactivity, insufficient intake of energy and protein, and poor muscle health in older adults suggests that physical exercise and targeted nutritional supplementation may offer substantial therapeutic gain against sarcopenia and its negative correlates. This view is supported by observational studies as well as by small-scale clinical trials. In this review, we summarize the available evidence on the beneficial effects of behavioral interventions on sarcopenia. We also briefly describe how the knowledge gathered so far has been used to design the "Sarcopenia and Physical fRailty IN older people: multicomponenT Treatment strategies" (SPRINTT) project. The randomized clinical trial conducted within SPRINTT will provide robust evidence on the effectiveness of exercise and nutrition at preventing negative outcomes associated with sarcopenia and physical frailty

Sex and Gender Differences in Ischemic Heart Disease: Endocrine Vascular Disease Approach (EVA) Study Design

Improvements in ischemic heart disease (IHD) management have been unbalanced between sexes, with coronary microvascular dysfunction considered the likely underlying reason. The Endocrine Vascular disease Approach (EVA) is an observational study (Clinicaltrial.gov NCT02737982) aiming to assess sex and gender interactions between coronary circulation, sexual hormones, and platelet function. Consecutive patients with IHD undergoing coronary angiography will be recruited: (1) to assess sex and gender differences in angiographic reperfusion indexes; (2) to evaluate the effects of estrogen/androgen on sex-related differences in myocardial ischemia; (3) to investigate the platelet biology differences between men and women with IHD; (4) to verify sex- and gender-driven interplay between response to percutaneous coronary intervention, platelets, sex hormones, and myocardial damage at baseline and its impact on 12-month outcomes. The integration of sex and gender in this translational project on IHD will contribute to the identification of new targets for further innovative clinical interventions