Gravitational waves from the remnants of the first stars

Gravitational waves (GWs) provide a revolutionary tool to investigate yet unobserved astrophysical objects. Especially the first stars, which are believed to be more massive than present-day stars, might be indirectly observable via the merger of their compact remnants. We develop a self-consistent, cosmologically representative, semi-analytical model to simulate the formation of the first stars. By extrapolating binary stellar-evolution models at 10 per cent solar metallicity to metal-free stars, we track the individual systems until the coalescence of the compact remnants. We estimate the contribution of primordial stars to the merger rate density and to the detection rate of the Advanced Laser Interferometer Gravitational-Wave Observatory (aLIGO). Owing to their higher masses, the remnants of primordial stars produce strong GW signals, even if their contribution in number is relatively small. We find a probability of greater than or similar to 1 per cent that the current detection GW150914 is of primordial origin. We estimate that aLIGO will detect roughly 1 primordial BH-BH merger per year for the final design sensitivity, although this rate depends sensitively on the primordial initial mass function (IMF). Turning this around, the detection of black hole mergers with a total binary mass of similar to 300 M-circle dot would enable us to constrain the primordial IMF

Unveiling the gravitational universe at mu-Hz frequencies

Funding Information: Open access funding provided by Università degli Studi di Milano - Bicocca within the CRUI-CARE Agreement. Publisher Copyright: © 2021, The Author(s).We propose a space-based interferometer surveying the gravitational wave (GW) sky in the milli-Hz to mu-Hz frequency range. By the 2040s, the mu-Hz frequency band, bracketed in between the Laser Interferometer Space Antenna (LISA) and pulsar timing arrays, will constitute the largest gap in the coverage of the astrophysically relevant GW spectrum. Yet many outstanding questions related to astrophysics and cosmology are best answered by GW observations in this band. We show that a mu-Hz GW detector will be a truly overarching observatory for the scientific community at large, greatly extending the potential of LISA. Conceived to detect massive black hole binaries from their early inspiral with high signal-to-noise ratio, and low-frequency stellar binaries in the Galaxy, this instrument will be a cornerstone for multimessenger astronomy from the solar neighbourhood to the high-redshift Universe.Peer reviewe

Clinical assessment instruments validated for nursing practice in the Italian context: a systematic review of the literature

Aims. With the aim to identify the instruments validated for Italian nursing practice, a systematic review of the literature was undertaken.Results. A total of 101 instruments emerged. The majority (89; 88.1%) were developed in other countries; the remaining (14; 13.9%) were developed and validated in the Ital-ian context. The instruments were developed to measure patient’s problems (63/101; 62.4%), outcomes (27/101; 26.7%), risks (4/101; 4%) and others issues (7/101; 6.9%). The majority of participants involved in the validation processes were younger adults (49; 48.5%), older adults (40; 39.5%), children (4; 4%), adolescents (3; 3%), and children/adolescents (1; 1%). The instruments were structured primarily in the form of questionnaires (61; 60.4%), as a grid for direct observation (27; 26.7%) or in other forms (12; 11.9%). Among the 101 instruments emerged, there were 1 to 7 validation measures documented with on average 3.2 (95% CI 2.86-3.54) for each instrument.Conclusions. Developing validation studies giving priority to those instruments widely adopted in the clinical nursing practice is recommended.  

Laser Interferometer Space Antenna

Following the selection of The Gravitational Universe by ESA, and the successful flight of LISA Pathfinder, the LISA Consortium now proposes a 4 year mission in response to ESA's call for missions for L3. The observatory will be based on three arms with six active laser links, between three identical spacecraft in a triangular formation separated by 2.5 million km. LISA is an all-sky monitor and will offer a wide view of a dynamic cosmos using Gravitational Waves as new and unique messengers to unveil The Gravitational Universe. It provides the closest ever view of the infant Universe at TeV energy scales, has known sources in the form of verification binaries in the Milky Way, and can probe the entire Universe, from its smallest scales near the horizons of black holes, all the way to cosmological scales. The LISA mission will scan the entire sky as it follows behind the Earth in its orbit, obtaining both polarisations of the Gravitational Waves simultaneously, and will measure source parameters with astrophysically relevant sensitivity in a band from below $10^{-4}\,$Hz to above $10^{-1}\,$Hz.Comment: Submitted to ESA on January 13th in response to the call for missions for the L3 slot in the Cosmic Vision Programm

Astrophysics with the Laser Interferometer Space Antenna

Laser Interferometer Space Antenna (LISA) will be a transformative experiment for gravitational wave astronomy as it will offer unique opportunities to address many key astrophysical questions in a completely novel way. The synergy with ground-based and other space-based instruments in the electromagnetic domain, by enabling multi-messenger observations, will add further to the discovery potential of LISA. The next decade is crucial to prepare the astrophysical community for LISA's first observations. This review outlines the extensive landscape of astrophysical theory, numerical simulations, and astronomical observations that are instrumental for modeling and interpreting the upcoming LISA datastream. To this aim, the current knowledge in three main source classes for LISA is reviewed: ultra-compact stellar-mass binaries, massive black hole binaries, and extreme or intermediate mass ratio inspirals. The relevant astrophysical processes and the established modeling techniques are summarized. Likewise, open issues and gaps in our understanding of these sources are highlighted, along with an indication of how LISA could help make progress in the different areas. New research avenues that LISA itself, or its joint exploitation with studies in the electromagnetic domain, will enable, are also illustrated. Improvements in modeling and analysis approaches, such as the combination of numerical simulations and modern data science techniques, are discussed. This review is intended to be a starting point for using LISA as a new discovery tool for understanding our Universe

Black holes, gravitational waves and fundamental physics: a roadmap

The grand challenges of contemporary fundamental physics—dark matter, dark energy, vacuum energy, inflation and early universe cosmology, singularities and the hierarchy problem—all involve gravity as a key component. And of all gravitational phenomena, black holes stand out in their elegant simplicity, while harbouring some of the most remarkable predictions of General Relativity: event horizons, singularities and ergoregions. The hitherto invisible landscape of the gravitational Universe is being unveiled before our eyes: the historical direct detection of gravitational waves by the LIGO-Virgo collaboration marks the dawn of a new era of scientific exploration. Gravitational-wave astronomy will allow us to test models of black hole formation, growth and evolution, as well as models of gravitational-wave generation and propagation. It will provide evidence for event horizons and ergoregions, test the theory of General Relativity itself, and may reveal the existence of new fundamental fields. The synthesis of these results has the potential to radically reshape our understanding of the cosmos and of the laws of Nature. The purpose of this work is to present a concise, yet comprehensive overview of the state of the art in the relevant fields of research, summarize important open problems, and lay out a roadmap for future progress. This write-up is an initiative taken within the framework of the European Action on 'Black holes, Gravitational waves and Fundamental Physics'

Massive Black Hole Merger Rates: The Effect of Kiloparsec Separation Wandering and Supernova Feedback

We revisit the predictions for the merger rate of massive black hole binaries detectable by the Laser Interferometer Space Antenna (LISA) and their background signal for pulsar-timing arrays. We focus on the effect of the delays between the merger of galaxies and the final coalescence of black hole binaries, and on supernova feedback on the black hole growth. By utilizing a semianalytic galaxy formation model, not only do we account for the driving of the evolution of binaries at separations less than or similar to 1 pc (gas-driven migration, stellar hardening, and triple/quadruple massive black hole systems), but we also improve on previous studies by accounting for the time spent by black hole pairs from kiloparsec down to parsec separation. We also include the effect of supernova feedback, which may eject gas from the nuclear region of low-mass galaxies, thus hampering the growth of black holes via accretion and suppressing their orbital migration in circumbinary disks. Despite including these novel physical effects, we predict that the LISA detection rate should still be greater than or similar to 2yr-1, irrespective of the model for the black hole seeds at high redshifts. Scenarios where black holes form from similar to 100M(circle dot) seeds are more significantly impacted by supernova feedback. We also find that for detectable events, the merging black holes typically have mass ratios between similar to 0.1 and 1. Predictions for the stochastic background in the band of pulsar-timing array experiments are instead rather robust and show only a mild dependence on the model

Astro2020 science white paper: The gravitational wave view of massive black holes

Coalescing, massive black-hole (MBH) binaries are the most powerful sources of gravitational waves (GWs) in the Universe, which makes MBH science a prime focus for ongoing and upcoming GW observatories. The Laser Interferometer Space Antenna (LISA) -- a gigameter scale space-based GW observatory -- will grant us access to an immense cosmological volume, revealing MBHs merging when the first cosmic structures assembled in the Dark Ages. LISA will unveil the yet unknown origin of the first quasars, and detect the teeming population of MBHs of $10^4 - 10^7$ solar masses. forming within protogalactic halos. The Pulsar Timing Array, a galactic-scale GW survey, can access the largest MBHs the Universe, detecting the cosmic GW foreground from inspiraling MBH binaries of about 10^9 solar masses. LISA can measure MBH spins and masses with precision far exceeding that from electromagnetic (EM) probes, and together, both GW observatories will provide the first full census of binary MBHs, and their orbital dynamics, across cosmic time. Detecting the loud gravitational signal of these MBH binaries will also trigger alerts for EM counterpart searches, from decades (PTAs) to hours (LISA) prior to the final merger. By witnessing both the GW and EM signals of MBH mergers, precious information will be gathered about the rich and complex environment in the aftermath of a galaxy collision. The unique GW characterization of MBHs will shed light on the deep link between MBHs of $10^4-10^{10}$ solar masses and the grand design of galaxy assembly, as well as on the complex dynamics that drive MBHs to coalescence

Clinical assessment instruments validated for nursing practice in the Italian context: a systematic review of the literature

Aims. With the aim to identify the instruments validated for Italian nursing practice, a systematic review of the literature was undertaken. Results. A total of 101 instruments emerged. The majority (89; 88.1%) were developed in other countries; the remaining (14; 13.9%) were developed and validated in the Italian context. The instruments were developed to measure patient’s problems (63/101; 62.4%), outcomes (27/101; 26.7%), risks (4/101; 4%) and others issues (7/101; 6.9%). The majority of participants involved in the validation processes were younger adults (49; 48.5%), older adults (40; 39.5%), children (4; 4%), adolescents (3; 3%), and children/adolescents (1; 1%). The instruments were structured primarily in the form of questionnaires (61; 60.4%), as a grid for direct observation (27; 26.7%) or in other forms (12; 11.9%). Among the 101 instruments emerged, there were 1 to 7 validation measures documented with on average 3.2 (95% CI 2.86-3.54) for each instrument. Conclusions. Developing validation studies giving priority to those instruments widely adopted in the clinical nursing practice is recommended

Clinical assessment instruments validated for nursing practice in the Italian context: a systematic review of the literature

Aims. With the aim to identify the instruments validated for Italian nursing practice, a systematic review of the literature was undertaken. Results. A total of 101 instruments emerged. The majority (89; 88.1%) were developed in other countries; the remaining (14; 13.9%) were developed and validated in the Italian context. The instruments were developed to measure patient’s problems (63/101; 62.4%), outcomes (27/101; 26.7%), risks (4/101; 4%) and others issues (7/101; 6.9%). The majority of participants involved in the validation processes were younger adults (49; 48.5%), older adults (40; 39.5%), children (4; 4%), adolescents (3; 3%), and children/adolescents (1; 1%). The instruments were structured primarily in the form of questionnaires (61; 60.4%), as a grid for direct observation (27; 26.7%) or in other forms (12; 11.9%). Among the 101 instruments emerged, there were 1 to 7 validation measures documented with on average 3.2 (95% CI 2.86-3.54) for each instrument. Conclusions. Developing validation studies giving priority to those instruments widely adopted in the clinical nursing practice is recommended