1,720,964 research outputs found
Exploring galaxies-gravitational waves cross-correlations as an astrophysical probe
No full textGravitational waves astronomy has opened a new opportunity to study the Universe. Full exploitation of this window can especially be provided by combining data coming from gravitational waves experiments with luminous tracers of the Large Scale Structure, like galaxies. In this work we investigate the cross-correlation signal between gravitational waves resolved events, as detected by the Einstein Telescope, and actively star-forming galaxies. The galaxies distribution is computed through their UV and IR luminosity functions and the gravitational waves events, assumed to be of stellar origin, are self-consistently computed from the aforementioned galaxies distribution. We provide a state-of-the-art treatment both on the astrophysical side, {taking} into account the impact of the star formation and chemical evolution histories of galaxies, and in computing the cross-correlation signal, for which we include lensing and relativistic effects. {We find that the measured cross-correlation signal can be sufficiently strong to overcome the noise and provide a clear signal. As a possible application of this methodology, we consider a proof-of-concept case in which we aim at discriminating a metallicity dependence on the compact objects merger efficiency against a reference case with no metallicity dependence.} When considering galaxies with a Star Formation Rate ψ > 10 Mo ̇/yr, a Signal-to-Noise ratio around a value of 2-4 is gained after a decade of observation time, depending on the observed fraction of the sky. This formalism can be exploited as an astrophysical probe and could potentially allow to test and compare different astrophysical scenarios
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Lyman- forest constraints on Primordial Black Holes as Dark Matter
Full text linkThe renewed interest in the possibility that primordial black holes (PBHs) may constitute a significant part of dark matter has provided motivation for revisiting old observational constraints, as well as developing new ones. We present new limits on the PBH abundance, from a comprehensive analysis of high-resolution high-redshift Lyman-α forest data. Poisson fluctuations in the PBH number density induce a small-scale power enhancement which departs from the standard cold dark matter prediction. Using a grid of hydrodynamic simulations exploring different values of astrophysical parameters, we obtain a marginalized upper limit on the PBH mass of fPBHMPBH∼60M⊙ at 2σ, when a Gaussian prior on the reionization redshift is imposed, preventing its posterior distribution from peaking on very high values, which are disfavored by the most recent estimates obtained both through cosmic microwave background and intergalactic medium observations. Such a bound weakens to fPBHMPBH∼170M⊙ when a conservative flat prior is instead assumed. Both limits significantly improve on previous constraints from the same physical observable. We also extend our predictions to nonmonochromatic PBH mass distributions, ruling out large regions of the parameter space for some of the most viable PBH extended mass functions.The renewed interest in the possibility that primordial black holes (PBHs) may constitute a significant part of the dark matter has motivated revisiting old observational constraints, as well as developing new ones. We present new limits on the PBH abundance, from a comprehensive analysis of high-resolution, high-redshift Lyman- forest data. Poisson fluctuations in the PBH number density induce a small-scale power enhancement which departs from the standard cold dark matter prediction. Using a grid of hydrodynamic simulations exploring different values of astrophysical parameters, {we obtain a marginalized upper limit on the PBH mass of at , when a Gaussian prior on the reionization redshift is imposed, preventing its posterior distribution to peak on very high values, which are disfavoured by the most recent estimates obtained both through Cosmic Microwave Background and Inter-Galactic Medium observations. Such bound weakens to , when a conservative flat prior is instead assumed. Both limits significantly improves previous constraints from the same physical observable.} We also extend our predictions to non-monochromatic PBH mass distributions, ruling out large regions of the parameter space for some of the most viable PBH extended mass functions
Gravitational waves × HI intensity mapping: Cosmological and astrophysical applications
No full textTwo of the most rapidly growing observables in cosmology and astrophysics are gravitational waves (GW) and the neutral hydrogen (HI) distribution. In this work, we investigate the cross-correlation between resolved gravitational wave detections and HI signal from intensity mapping (IM) experiments. By using a tomographic approach with angular power spectra, including all projection effects, we explore possible applications of the combination of the Einstein Telescope and the SKAO intensity mapping surveys. We focus on three main topics: (i) statistical inference of the observed redshift distribution of GWs; (ii) constraints on dynamical dark energy models as an example of cosmological studies; (iii) determination of the nature of the progenitors of merging binary black holes, distinguishing between primordial and astrophysical origin. Our results show that: (i) the GW redshift distribution can be calibrated with good accuracy at low redshifts, without any assumptions on cosmology or astrophysics, potentially providing a way to probe astrophysical and cosmological models; (ii) the constrains on the dynamical dark energy parameters are competitive with IM-only experiments, in a complementary way and potentially with less systematics; (iii) it will be possible to detect a relatively small abundance of primordial black holes within the gravitational waves from resolved mergers. Our results extend towards GW × IM the promising field of multi-tracing cosmology and astrophysics, which has the major advantage of allowing scientific investigations in ways that would not be possible by looking at single observables separately
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
First Insights Into the Biological and Physical–Chemical Diversity of Various Salt Ponds of Trapani, Sicily
Full text linkThe salt ponds of Trapani, Sicily, represent an extreme and under-explored ecosystem characterised by varying salinity gradients and environmental conditions. These ponds, integral to traditional salt extraction, include cold, driving, hot and crystallizer ponds, each hosting diverse microbial communities. This study aimed to explore the biological and physical-chemical diversity of 11 ponds during the salt production season in Trapani. We conducted comprehensive physical-chemical characterizations, including measurements of pH, conductivity, viscosity, density, organic carbon and ion concentration. Microbial DNA was extracted from salt pond waters and subjected to metabarcoding of 16S rRNA genes to determine the diversity of archaea and bacteria. High-throughput sequencing revealed significant variations in microbial communities across different pond types and seasons. Cold ponds showed a higher diversity of moderately halophilic organisms, while crystallizer and feeding ponds were dominated by extreme halophiles, particularly archaeal genus Halorubrum and Haloquadratum and bacterial genus Salinibacter. Statistical analyses indicated that environmental parameters, especially salinity and temperature, significantly influenced microbial community composition. Our findings enhance the understanding of microbial ecology in saline environments and highlight the potential of halophilic microorganisms. This study provides a foundation for future research into the functional roles of these microorganisms and their industrial applications
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
