Bibliografie tematiche / Black hole population

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Letteratura scientifica selezionata sul tema "Black hole population"

Autore: Grafiati
Pubblicato: 26 ottobre 2024

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Articoli di riviste sul tema "Black hole population"

1

Nomoto, K., K. Maeda, H. Umeda e N. Tominaga. "Nucleosynthesis in Population III Supernovae". Highlights of Astronomy 13 (2005): 560–65. http://dx.doi.org/10.1017/s1539299600016580.

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AbstractStars more massive than ~ 20–25 M⊙ form a black hole at the end of their evolution. Stars with non-rotating black holes are likely to collapse ”quietly” ejecting a small amount of heavy elements (Faint supernovae). In contrast, stars with rotating black holes are likely to give rise to very energetic supernovae (Hypernovae). Nucleosynthesis in Hypernovae is characterized by larger abundance ratios (Zn,Co,V,Ti)/Fe and smaller (Mn,Cr)/Fe than normal supernovae, which can explain the observed trend of these ratios in extremely metal-poor stars. Nucleosynthesis in Faint supernovae is characterized by a large amount of fall-back. We show that the abundance pattern of the recently discovered most Fe-poor star, HE0107-5240, and other extremely metal-poor carbon-rich stars are in good accord with those of black-hole-forming supernovae, but not pair-instability supernovae. This suggests that black-hole-forming supernovae made important contributions to the early Galactic (and cosmic) chemical evolution as the First (Pop III) Supernovae.
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2

Stevenson, Simon. "Biases in Estimates of Black Hole Kicks from the Spin Distribution of Binary Black Holes". Astrophysical Journal Letters 926, n. 2 (1 febbraio 2022): L32. http://dx.doi.org/10.3847/2041-8213/ac5252.

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Abstract A population of more than 50 binary black hole mergers has now been observed by the LIGO and Virgo gravitational-wave observatories. While neutron stars are known to have large velocities associated with impulsive kicks imparted to them at birth in supernovae, whether black holes receive similar kicks, and of what magnitude, remains an open question. Recently, Callister et al. analyzed the binary black hole population under the hypothesis that they were all formed through isolated binary evolution and claimed that large black hole kicks (greater than 260 km s−1 at 99% confidence) were required for the spin distribution of merging binary black holes to match observations. Here we highlight that a key assumption made by Callister et al.—that all secondary black holes can be tidally spun up—is not motivated by physical models and may lead to a bias in their estimate of the magnitudes of black hole kicks. We make only minor changes to the Callister et al. model, accounting for a population of wider merging binaries where tidal synchronization is ineffective. We show that this naturally produces a bimodal spin distribution for secondary black holes and that the spin–orbit misalignments observed in the binary black hole population can be explained by more typical black hole kicks of order 100 km s−1, consistent with kicks inferred from Galactic X-ray binaries containing black holes. We conclude that the majority of the binary black hole population is consistent with forming through isolated binary evolution.
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3

Pesce, Dominic W., Daniel C. M. Palumbo, Angelo Ricarte, Avery E. Broderick, Michael D. Johnson, Neil M. Nagar, Priyamvada Natarajan e José L. Gómez. "Expectations for Horizon-Scale Supermassive Black Hole Population Studies with the ngEHT". Galaxies 10, n. 6 (2 dicembre 2022): 109. http://dx.doi.org/10.3390/galaxies10060109.

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We present estimates for the number of supermassive black holes (SMBHs) for which the next-generation Event Horizon Telescope (ngEHT) can identify the black hole “shadow”, along with estimates for how many black hole masses and spins the ngEHT can expect to constrain using measurements of horizon-resolved emission structure. Building on prior theoretical studies of SMBH accretion flows and analyses carried out by the Event Horizon Telescope (EHT) collaboration, we construct a simple geometric model for the polarized emission structure around a black hole, and we associate parameters of this model with the three physical quantities of interest. We generate a large number of realistic synthetic ngEHT datasets across different assumed source sizes and flux densities, and we estimate the precision with which our defined proxies for physical parameters could be measured from these datasets. Under April weather conditions and using an observing frequency of 230 GHz, we predict that a “Phase 1” ngEHT can potentially measure ∼50 black hole masses, ∼30 black hole spins, and ∼7 black hole shadows across the entire sky.
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Doctor, Zoheyr, Ben Farr e Daniel E. Holz. "Black Hole Leftovers: The Remnant Population from Binary Black Hole Mergers". Astrophysical Journal Letters 914, n. 1 (1 giugno 2021): L18. http://dx.doi.org/10.3847/2041-8213/ac0334.

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Callister, Thomas A., Simona J. Miller, Katerina Chatziioannou e Will M. Farr. "No Evidence that the Majority of Black Holes in Binaries Have Zero Spin". Astrophysical Journal Letters 937, n. 1 (1 settembre 2022): L13. http://dx.doi.org/10.3847/2041-8213/ac847e.

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Abstract The spin properties of merging black holes observed with gravitational waves can offer novel information about the origin of these systems. The magnitudes and orientations of black hole spins offer a record of binaries’ evolutionary history, encoding information about massive stellar evolution and the astrophysical environments in which binary black holes are assembled. Recent analyses of the binary black hole population have yielded conflicting portraits of the black hole spin distribution. Some works suggest that black hole spins are small but nonzero and exhibit a wide range of misalignment angles relative to binaries’ orbital angular momenta. Other works conclude that the majority of black holes are nonspinning while the remainder are rapidly rotating and primarily aligned with their orbits. We revisit these conflicting conclusions, employing a variety of complementary methods to measure the distribution of spin magnitudes and orientations among binary black hole mergers. We find that the existence of a subpopulation of black holes with vanishing spins is not required by current data. Should such a subpopulation exist, we conclude that it must contain ≲60% of binaries. Additionally, we find evidence for significant spin–orbit misalignment among the binary black hole population, with some systems exhibiting misalignment angles greater than 90°, and see no evidence for an approximately spin-aligned subpopulation.
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Rees, Martin J., e Marta Volonteri. "Massive black holes: formation and evolution". Proceedings of the International Astronomical Union 2, S238 (agosto 2006): 51–58. http://dx.doi.org/10.1017/s1743921307004681.

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AbstractSupermassive black holes are nowadays believed to reside in most local galaxies. Observations have revealed us vast information on the population of local and distant black holes, but the detailed physical properties of these dark massive objects are still to be proven. Accretion of gas and black hole mergers play a fundamental role in determining the two parameters defining a black hole: mass and spin. We briefly review here the basic properties of the population of supermassive black holes, focusing on the still mysterious formation of the first massive black holes, and their evolution from early times to now.
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Reynolds, Christopher S. "Observational Constraints on Black Hole Spin". Annual Review of Astronomy and Astrophysics 59, n. 1 (8 settembre 2021): 117–54. http://dx.doi.org/10.1146/annurev-astro-112420-035022.

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The spin of a black hole is an important quantity to study, providing a window into the processes by which a black hole was born and grew. Furthermore, spin can be a potent energy source for powering relativistic jets and energetic particle acceleration. In this review, I describe the techniques currently used to detect and measure the spins of black holes. It is shown that: ▪ Two well-understood techniques, X-ray reflection spectroscopy and thermal continuum fitting, can be used to measure the spins of black holes that are accreting at moderate rates. There is a rich set of other electromagnetic techniques allowing us to extend spin measurements to lower accretion rates. ▪ Many accreting supermassive black holes are found to be rapidly spinning, although a population of more slowly spinning black holes emerges at masses above [Formula: see text] as expected from recent structure formation models. ▪ Many accreting stellar-mass black holes in X-ray binary systems are rapidly spinning and must have been born in this state. ▪ The advent of gravitational wave astronomy has enabled the detection of spin effects in merging binary black holes. Most of the premerger black holes are found to be slowly spinning, a notable exception being an object that may itself be a merger product. ▪ The stark difference in spins between the black hole X-ray binary and the binary black hole populations shows that there is a diversity of formation mechanisms. Given the array of new electromagnetic and gravitational wave capabilities currently being planned, the future of black hole spin studies is bright.
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8

Treister, Ezequiel, Claudia M. Urry, Kevin Schawinski, Brooke D. Simmons, Priyamvada Natarajan e Marta Volonteri. "The Multiwavelength AGN Population and the X-ray Background". Proceedings of the International Astronomical Union 9, S304 (ottobre 2013): 188–94. http://dx.doi.org/10.1017/s1743921314003731.

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AbstractIn order to fully understand galaxy formation we need to know when in the cosmic history are supermassive black holes (SMBHs) growing more intensively, in what type of galaxies this growth is happening and what fraction of these sources are invisible at most wavelengths due to obscuration. Active Galactic Nuclei (AGN) population synthesis models that can explain the spectral shape and intensity of the cosmic X-ray background (CXRB) indicate that most of the SMBH growth occurs in moderate-luminosity (LX~ 1044 erg/s) sources (Seyfert-type AGN), at z~ 0.5−1 and in heavily obscured but Compton-thin, NH~ 1023cm−2, systems. However, this is not the complete history, as a large fraction of black hole growth does not emit significantly in X-rays either due to obscuration, intrinsic low luminosities or large distances. The integrated intensity at high energies indicates that a significant fraction of the total black hole growth, 22%, occurs in heavily-obscured systems that are not individually detected in even the deepest X-ray observations. We further investigate the AGN triggering mechanism as a function of bolometric luminosity, finding evidence for a strong connection between significant black hole growth events and major galaxy mergers from z~ 0 to z~ 3, while less spectacular but longer accretion episodes are most likely due to other (stochastic) processes. AGN activity triggered by major galaxies is responsible for ~60% of the total black hole growth. Finally, we constrain the total accreted mass density in supermassive black holes at z > 6, inferred via the upper limit derived from the integrated X-ray emission from a sample of photometrically selected galaxy candidates. We estimate an accreted mass density <1000 M⊙Mpc−3 at z~ 6, significantly lower than the previous predictions from some existing models of early black hole growth and earlier prior observations.
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Netzer, Hagai. "Black Hole Demographics: Statistical Characteristics of Accreting Black Holes". Proceedings of the International Astronomical Union 5, S267 (agosto 2009): 213–22. http://dx.doi.org/10.1017/s1743921310006319.

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This review summarizes the important properties of active black holes (BHs) up to z ~ 2; their mass, accretion rate, and growth rate. At higher redshifts, such information is only available for small samples that do not represent the entire population of active galactic nuclei (AGNs). Black hole spin is still unknown; it is speculated to change with redshift, but with little experimental evidence. The available data sets also enable a direct comparison of BH accretion rates and host galaxy star-formation rates (SFRs). The ratio of the BH growth rate g(BH) and the bulge growth rate g(bulge), suggests that the two are proportional to each other. The local value of g(bulge)/g(BH) in low-luminosity AGNs is of order 100 and the corresponding ratio in high-luminosity, high-redshift AGNs is of order 10. This has important implications regarding the parallel evolution of active BHs and their hosts.
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Zevin, Michael, e Daniel E. Holz. "Avoiding a Cluster Catastrophe: Retention Efficiency and the Binary Black Hole Mass Spectrum". Astrophysical Journal Letters 935, n. 1 (1 agosto 2022): L20. http://dx.doi.org/10.3847/2041-8213/ac853d.

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Abstract The population of binary black hole mergers identified through gravitational waves has uncovered unexpected features in the intrinsic properties of black holes in the universe. One particularly surprising and exciting result is the possible existence of black holes in the pair-instability mass gap, ∼50–120 M ⊙. Dense stellar environments can populate this region of mass space through hierarchical mergers, with the retention efficiency of black hole merger products strongly dependent on the escape velocity of the host environment. We use simple toy models to represent hierarchical merger scenarios in various dynamical environments. We find that hierarchical mergers in environments with high escape velocities (≳300 km s−1) are efficiently retained. If such environments dominate the binary black hole merger rate, this would lead to an abundance of high-mass mergers that is potentially incompatible with the empirical mass spectrum from the current catalog of binary black hole mergers. Models that efficiently generate hierarchical mergers, and contribute significantly to the observed population, must therefore be tuned to avoid a “cluster catastrophe” of overproducing binary black hole mergers within and above the pair-instability mass gap.
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Più fonti

Tesi sul tema "Black hole population"

1

Plowman, Joseph Eugene. "Constraining massive black hole population models with gravitational wave observations". Thesis, Montana State University, 2010. http://etd.lib.montana.edu/etd/2010/plowman/PlowmanJ0510.pdf.

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A number of scenarios have been proposed for the origin of the supermassive black holes (SMBHs) that are found in the centres of most galaxies. Many such scenarios predict a high-redshift population of massive black holes (MBHs), with masses in the range 10² to 10⁵ times that of the Sun. When the Laser Interferometer Space Antenna (LISA) is finally operational, it is likely that it will detect on the order of 100 of these MBH binaries as they merge. The differences between proposed population models produce appreciable effects in the portion of the population which is detectable by LISA, so it is likely that the LISA observations will allow us to place constraints on them. However, gravitational wave detectors such as LISA will not be able to detect all such mergers nor assign precise black hole parameters to the merger, due to weak gravitational wave signal strengths. This dissertation explores LISA's ability to distinguish between several MBH population models. In this way, we go beyond predicting a LISA observed population and consider the extent to which LISA observations could inform astrophysical modelers. The errors in LISA parameter estimation are applied in two ways, with an 'Error Kernel' that is marginalized over astrophysically uninteresting 'sample' parameters, and with a more direct method which generates random sample parameters for each source in a population realization. We consider how the distinguishability varies depending on the choice of source parameters (1 or 2 parameters chosen from masses, redshift or spins) used to characterize the model distributions, with confidence levels determined by 1 or 2-dimensional tests based on the Kolmogorov-Smirnov test.
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2

Buchner, Johannes. "On the obscuration of the growing supermassive black hole population". Diss., Ludwig-Maximilians-Universität München, 2015. http://nbn-resolving.de/urn:nbn:de:bvb:19-181878.

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Aktive Galaxienkerne (AGN) werden durch das Wachstum super-schwere schwarze Löcher, die im Zentrum jeder massiven Galaxie sitzen, betrieben. Da enge Korrelationen ihrer Massen zu Eigenschaften der elliptischen Galaxienkomponente beobachtet werden, und durch ihre extreme Leuchtkraft ist es naheliegend, dass AGN einen wichtigen Baustein von Galaxien bilden. Der erste Schritt, AGN zu verstehen ist es, ihre Häufigkeit zu ermitteln, sowie die Leuchtkraft der Population. Dieses Unterfangen wird dadurch erschwert, dass die meisten AGN von Gas und Staub umgeben sind. Selbst im energiereichen Röntgenbereich, der in dieser Arbeit verwendet wird, wird die intrinsische Strahlung durch Absorption um mehrere Größenordnung verringert. Die vorliegenden Doktorarbeit untersucht zuerst die Eigenschaften dieser Wolken, im speziellen ihre Geometrie, Säulendichteverteilung und ihr Verhältnis zur Leuchtkraft des AGN. Dazu werden ∼ 300 AGN von der längst-beobachteten Röntgenregion, der Chandra Deep Field South Kampagne verwendet. Eine neue Bayesische Methode zur Spektralanalyse wurde entwickelt, um verschiedene physikalisch motivierte Modelle für den Aufbau der Wolken zu vergleichen. Das Röntgenspektrum reagiert, hauptsächlich dank Compton-Streuung, auf die Gesamtbedeckung der Quelle durch das Gas. Eine detaillierte Analyse zeigt, dass die Wolken mit einer Torus (“Donut”) Form konsistent sind, und sowohl vollständige Bedeckung als auch eine Scheiben-artige Konfiguration ausgeschlossen werden können. Außerdem ist eine weiteren Komponente höherer Dichte notwendig um zusätzlich beobachtete Compton-Reflektion zu erklären. Dies deutet auf eine strukturierte Formation hin, wie etwa ein Torus mit einem Dichtegradienten. Die Untersuchung der gesamten AGN-Population inklusive der AGN mit hohen Säulendichten, verlangt eine große Stichprobe mit einem genauen Verständnis für die Stichprobenverzerrung, sowie fortgeschrittene statistische Inferenzmethoden. Diese Arbeit baut auf eine ∼ 2000 AGN große Stichprobe die durch Röntgenemission detektiert wurde, bestehend aus mehrschichtigen Kampagnen aus den CDFS, AEGIS-XD, COSMOS and XMM-XXL Regionen. Die Röntgenspektren wurden im Detail mit einem physikalischen Spektralmodell analysiert, um die intrinsische Leuchtkraft, Rotverschiebung, sowie Säulendichte (N_H) für jedes Objekt zu erhalten, inklusive der Messunsicherheit. Außerdem wurden in dieser Arbeit neue statistische Methoden entwickelt um die richtige Assoziation zu optischen/infraroten Objekten zu finden, und um die Unsicherheiten durch Objekte ohne Pendant, der Rotverschiebungsmessung, sowie der Poissonfehler des Röntgenspektrums in alle Ergebnisse einzubinden. Einen weiteren wichtigen Beitrag bildet eine Bayesische, nicht-parametrische Methode um die unverzerrte Dichte von AGN in kosmologischen Volumen als Funktion von intrinsischer Leuchtkraft, Rotverschiebung und Säulendichte (N H ) der verbergenden Wolken zu rekonstruieren. Obwohl in dieser Methode lediglich Glattheit verwendet wird, kann dieser Ansatz dieselben Formen der Leuchtkraftverteilung sowie ihre Entwicklung rekonstruieren, die sonst oft in emprischen Modellen verwendet werden, jedoch ohne diese apriori anzunehmen. Im Großen und Ganzen kann die Leuchtkraftverteilung, in allen Rotverschiebungsschalen, als Potenzgesetz mit einem Umbruchspunkt beschrieben werden. Sowohl die Normalisation als auch der Leuchtkraftumbruchspunkt entwickeln sich über den Lauf des Universums, allerdings zeigen die Daten keine Belege für eine Veränderung der Form der Verteilung. Dies deutet darauf hin, im Gegensatz zu Aussagen vorherigen Studien, dass der Rückkopplungsmechanismus zwischen AGN und beherbergender Galaxie immer gleich funktioniert, und sich nur die Anzahl und Größe der wachsenden Systeme verändert. Die nicht-parametrische Rekonstruktionsmethode verwendet keine Annahmen darüber wie sich z.B. die Häufigkeiten von Säulendichte des verdeckenden Gases mit Leuchtkraft oder Rotverschiebung verändert. Dies erlaubt sehr robuste Schlüsse über den Anteil der verdeckten AGN (N_H > 10^22 cm −2 ), die 77 +4 −5 % der Population ausmachen sowie den Anteil der Compton-dicken AGN (38 +8 −7 %), die sich hinter enormen Säulendichten (N_H > 10^24 cm −2 ) verbergen. Insbesondere dass der letztere Anteil bestimmt werden konnte, lässt endlich Schlüsse darauf zu, wieviel AGN “verdeckt” wachsen. Außerdem suggeriert es, dass der Torus einen großen Teil des AGN verdeckt. Basierend auf der Leuchtkraft der gesamten AGN Population wurde die Masse, die über den Lauf der Zeit in schwarzen Löchern gesperrt wurde, geschätzt, und die Massendichte der supermassereichen schwarzen Löcher im heutigen Universum vorhergesagt. Die Rekonstruktion bringt außerdem zu Tage, dass der Anteil der verdeckten AGN (insbesondere der Compton-dünnen AGN) eine negative Leuchtkraftabhängigkeit aufweist, und dass sich diese Abhängigkeit über die Geschichte des Universums entwickelt hat. Dieses Resultat wird in dieser Arbeit im Zusammenhang mit bestehenden Modellen interpretiert und ist möglicherweise ein Nebeneffekt eines nicht-hierarchischen Wachstums von AGN.
Active Galactic Nuclei (AGN) are powered by the growth of super-massive black holes (SMBHs), which can be found at the centre of every massive galaxy. Due to tight scaling relationships of their masses with properties of their host spheroidal components, as well as the massive energy output AGN release, they are thought to play an important role in the formation and evolution of galaxies. The first step to understanding AGN is to determine their prevalence in the Universe, as well as the luminosity output of their entire population. This enterprise is hampered by the fact that most AGN are obscured by thick layers of gas and dust, making them difficult to detect. Even in the energetic X-ray wavelengths employed in this work, the intrinsic radiation of obscured AGN is suppressed by multiple orders of magnitude. In this work I first study the properties of this obscurer, specifically its geometry, column density distribution and its relation to the AGN luminosity. For this, ∼ 300 AGN from the deepest X-ray field to date, the Chandra Deep Field South survey, are used. I apply a novel Bayesian spectral analysis methodology to distinguish between several physically motivated models for the obscurer. The X-ray spectrum is, mainly due to Compton scattering, sensitive to the covering fraction of the obscurer. A detailed spectral analysis shows that the obscurer is consistent with a torus (“donut”) shape, but complete covering as well as disk-like configurations can be excluded. Furthermore, a high-density component is necessary to explain additional observed Compton-reflection beyond that expected from the line-of-sight obscuration, indicating a structured obscurer such as a torus with a density gradient. The study of the population of AGN requires a large sample with detailed understanding of the selection effect and sophisticated inference techniques. A X-ray selected sample of ∼ 2000 AGN from a multi-tiered survey including the CDFS, AEGIS-XD, COSMOS and XMM-XXL fields is analysed in detail. Through Bayesian spectral analysis with a physical model, the intrinsic luminosity, redshift and column density (N H ) is obtained for each source, including their uncertainties. This thesis also develops advanced statistical methodology for choosing the correct counterpart, and propagates the uncertainty from missing counterparts, redshift estimation as well as the Poisson noise from X-ray spectra into all final results. Another important new contribution is a Bayesian non-parametric technique to reconstruct the unbiased number density of AGN in cosmological volumes as a function of intrinsic luminosity, redshift and column density (N_H). Despite only assuming smoothness, this approach is capable of reproducing the shapes commonly assumed for the luminosity function and its evolution, without assuming them a priori. Overall, the luminosity function appears to be consistent with a double powerlaw at all redshifts studied. Both the normalisation and break luminosity evolve over time, while there is no evidence that the shape changes. This indicates that contrary to previous claims, the feedback mechanism works the same across the history of the Universe, but only the number and luminosity scale of the accreting systems changes. The non-parametric reconstruction allows the study of the fraction of obscured AGN up to the Compton-thick regime in a very robust way, i.e. without assuming a luminosity or redshift-dependent behaviour a priori. About 77 +4 −5 % of AGN are obscured (N_H > 10^22 cm −2), while 38 +8 −7 % belong to the heavily obscured, elusive Compton-thick class (N_H > 10^24 cm −2). The latter fraction in particular finally constrains the importance of obscured growth phases in the life of accreting SMBHs. Based on the total luminosity output of the AGN population, the mass locked into black holes over cosmic time is estimated, and the mass density of relic SMBHs in the local Universe is predicted, and matches local estimates. The large fraction of obscured AGN suggests that the obscuring torus must have a large angular extent. The non-parametric reconstruction also finds and characterises a negative luminosity dependence for the fraction of obscured AGN, in particular those that are Compton-thin, which are less prevalent at high luminosities. Additionally, this luminosity dependence appears to evolve with redshift. These findings are discussed in the context of existing models and it is concluded that the observed evolution may be to first order a side-effect of a anti-hierarchical growth of super-massive black holes.
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3

Buchner, Johannes [Verfasser], e Kirpal [Akademischer Betreuer] Nandra. "On the obscuration of the growing supermassive black hole population / Johannes Buchner. Betreuer: Kirpal Nandra". München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2015. http://d-nb.info/1070762989/34.

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4

Pierra, Grégoire. "Cosmologie avec les sirènes sombres et populations de binaires de trous noirs avec les ondes gravitationnelles de LIGO-Virgo-KAGRA". Electronic Thesis or Diss., Lyon 1, 2024. http://www.theses.fr/2024LYO10162.

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Les ondes gravitationnelles constituent une nouvelle sonde pour explorer l’Univers et étudier des phénomènes cosmiques jusque-là inaccessibles. Cette thèse se base sur des données d’ondes gravitationnelles récoltées par les détecteurs de la collaboration scientifique LIGO-Virgo-KAGRA. La première partie de ce travail porte sur la cosmologie avec les sirènes sombres, une méthode qui utilise les fusions de trous noirs pour mesurer les distances cosmologiques et inférer la valeur de la constante de Hubble, sans nécessiter de contrepartie électromagnétique. Elle présente également ICAROGW, un code d’inférence bayésienne hiérarchique, utilisant les données d’ondes gravitationnelles et des modèles décrivant les propriétés astrophysiques des trous noirs, comme leurs masses, leurs distances ou encore leurs spins, pour mesurer la constante de Hubble. La deuxième partie de cette étude teste particulièrement la robustesse des sirènes sombres pour la cosmologie. Elle explore l’impact des modèles de population de trous noirs sur l’estimation de la constante de Hubble, tout particulièrement lorsque certains processus astrophysiques ne sont pas modélisés. La troisième partie s’attache à la recherche et à l’identification de sous-populations de binaires de trous noirs dans l’univers. Elle examine la manière dont différents canaux de formation peuvent influencer les caractéristiques intrinsèques de ces objets compacts, notamment à travers les corrélations potentielles entre leur masse et leur spin. L’existence de ces corrélations serait révélatrice de la présence de sous-populations de trous noirs, comme les trous noirs hiérarchiques issus de coalescences précédentes. Enfin, le manuscrit se termine par une étude sur l’utilisation de méthodes de machine learning pour améliorer la qualité des données de l’interféromètre Virgo et détecter la présence de bruits non-gaussiens. Ces travaux explorent également l’intégration potentielle des résultats d’iDQ dans les algorithmes de détection des signaux d’ondes gravitationnelles, visant ainsi à renforcer le niveau de confiance dans ces détections
Gravitational waves constitute a new probe for exploring the Universe and studying cosmic phenomena that were previously inaccessible. This thesis is based on gravitational wave data collected by the LIGO-Virgo-KAGRA scientific collaboration detectors. The first part of this work focuses on cosmology with dark sirens, a method that uses binary black hole mergers to measure cosmological distances and infer the value of the Hubble constant, without requiring an electromagnetic counterpart. It also presents ICAROGW, a hierarchical Bayesian inference code that uses gravitational wave data and models describing the astrophysical properties of black holes, such as their masses, distances, and spins, to estimate the Hubble constant. The second part of this study tests in particular the robustness of the dark siren method for cosmology. It explores the impact of binary black hole population parameterization on the estimation of the Hubble constant, especially when certain astrophysical processes are not modelled. The third part focuses on the search and identification of subpopulations of binary black holes in the universe. It examines how different formation channels can influence the intrinsic characteristics of these compact objects, particularly through po- tential correlations between their mass and spin. The existence of these correlations would be indicative of the presence of subpopulations of black holes, such as hierarchical black holes, resulting from previous mergers. Finally, the manuscript concludes with a study on the use of machine learning methods to improve the quality of the Virgo interferometer data and detect the presence of non-Gaussian noises. This work also explores the potential integration of iDQ results into gravitational wave signal detection algorithms, thereby aiming to strengthen the confidence level in these detections
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Higgins, Jennifer C. "Survival, Home Range and Spatial Relationships of Virginia's Exploited Black Bear Population". Thesis, Virginia Tech, 1997. http://hdl.handle.net/10919/36765.

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Eighty-three (21M, 62F) of 194 black bears captured during 1994-1996 were equipped with radio collars. Annual survival rates estimated with Kaplain-Meier staggered entry approach for radio collared adult females, adult males, subadult females, and subadult males were 95.3, 100.0, 90.4 and 50.0% respectively. Hunting, handling, vehicle collisions, and natural causes accounted for 81.0, 11.1, 3.2, and 1.6% of mortality. Twenty, 9.8, and 70.6 % of bears harvested were harvested in the deer firearm season, the deer archery season, and the bear firearm season, respectively. Twenty-three cubs were equipped with expandable radio collars (11M,10F) or transmitters implanted subcutaneously (2M,0F) in 1995-1996. Six cubs (4M, 2F) died, 6 (3M,3F) survived their first year, and the status of 11 cubs (6M, 5F) was unknown. Survival rates (date marked until 4 December) estimated with Kaplain-Meier and Heisey-Fuller were 64.3 and 64.7% respectively. Interval survival rates were 71% (15 March to 31 May), 100% (1 June to 31 July), 92% (1 August to 31 August), and 100% (1 September to 4 December). Intraspecific aggression (33.3%), starvation (16.7%), unknown causes (16.7%) and predation (16.7%) were the causes of mortality. Total home range size for males and adult, subadult, and transitional age females were 7.2, 5.5, 5.6 and 7.2 km2 (95% MCP) and 11.2, 6.8, 9.0, and 10.0 km2 (95% normal kernel). Females with cubs had larger fall ranges than spring and summer ranges. Seasonal ranges of solitary females did not differ when estimated with MCP. Bears exhibited home range overlap among and within sex classes.
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6

Jones, Michael D. "DNA-based Population Estimation, Harvest Vulnerability, and Home Range Dynamics of Black Bears in Western Maryland". Thesis, West Virginia University, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=1522522.

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After nearly being extirpated from the state, black bears in Maryland have rebounded to a point where recreational harvest has now become an important management tool. Having a better understanding of bear population parameters, movements, and harvest vulnerability allows managers to implement hunting more effectively and responsibly. To estimate demographics of the Maryland bear population, we implemented noninvasive genetic sampling of bear hair during summer 2011. We used a model-based sampling design that allowed us to collect samples more efficiently. We used presence-only maximum entropy (Maxent) modeling to classify the study area based on predicted probability of bear occurrence, and allocated the majority of our hair snares to areas with high or medium probabilities. Using microsatellite analysis and mark-recapture methods, we estimated the bear population at 701 individuals. This represents a nearly doubling of the population since the previous estimate in 2005. Our density estimate (0.25 bears/km2) is comparable to other estimates from southeastern and mid-Atlantic states. Our sampling approach did lead to more efficient sample collection, with more hair samples collected at snares located in areas with predicted high or medium probability of bear occurrence than those in low probability areas. However, in the eastern portion of our study area, where bear occurrence is presumed to be much lower, our sampling effort seemed insufficient to collect enough samples for reliable abundance estimation. As a first step toward quantifying harvest vulnerability, we used Global Positioning System (GPS) units to record movements and spatial behaviors of 108 bear hunters during the 2005–2007 Maryland bear hunting seasons. Median values showed that hunters traveled 2.9 km per hunting event, but only 0.6 km from their starting point. Hunters did not seem to show any preferential use of areas based on the landscape metrics we examined (e.g., elevation, distance from nearest road) except cover type, where 81% of locations were in deciduous forests. We found few differences between spatial behaviors of groups of hunters based on harvest success, residency, and previous bear hunting experience, as classified using post-hunt mail surveys. One notable difference is that successful hunters used steeper slopes than unsuccessful hunters. We also found that hunter perceptions of total distance traveled and distance from nearest roads were often highly inaccurate, showing that hunter surveys are not a useful tool for collecting those data. For Garrett County, Maryland, we used the hunter locations to create a Maxent model of the spatial distribution of harvest pressure. We also created a model using fall telemetry locations of female bears and compared the models to identify areas of high (i.e., high hunter and high bear occurrence) and low (i.e., low hunter and high bear occurrence) harvest vulnerability. Both models showed higher probability of occurrence on public lands. Both high and low vulnerability areas comprised small portions of the county. The low vulnerability areas included 9 larger blocks (>1 km 2), which were 2.3 times steeper, 2.0 times farther from roads, and 1.5 times farther from streams than the medians for the study area. Those characteristics may limit hunter access to and use of the areas. Our predicted high vulnerability areas did not correspond to most previous bear harvest locations, indicating that our definition of harvest vulnerability often does not translate to actual harvest. Finally, we used GPS collars to track female bear locations in Garrett County and examine home range dynamics. Fixed kernel estimates for annual, spring, summer, and fall home ranges were 10.40 km 2, 8.93 km2, 16.08 km2, and 19.35 km 2, respectively. Fall and summer home ranges were larger than spring home ranges, but summer and fall ranges were similar. Solitary females had mean spring home ranges 6.9 times larger than females with cubs-of-the-year, but ranges did not differ during other seasons. Bears exhibited high levels of home range fidelity, with home range centroids shifting little among seasons or years. Intraspecific overlap of home ranges occurred during all 3 seasons, but was most common in summer. The results of this study provide Maryland bear biologists and managers with essential information about the state’s bear population. Home range estimates represent important baseline information to determine appropriate spatial scales of management. The abundance estimates will be used to set proper harvest quotas with the goal of slowing the bear population growth. The hunter movement analysis and harvest vulnerability modeling may be used by managers to adjust harvest regulations to increase the efficacy of the hunting seasons.

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7

Volonteri, Marta, Amy E. Reines, Hakim Atek, Daniel P. Stark e Maxime Trebitsch. "High-redshift Galaxies and Black Holes Detectable with the JWST: A Population Synthesis Model from Infrared to X-Rays". IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/626181.

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The first billion years of the Universe has been a pivotal time: stars, black holes (BHs), and galaxies formed and assembled, sowing the seeds of galaxies as we know them today. Detecting, identifying, and understanding the first galaxies and BHs is one of the current observational and theoretical challenges in galaxy formation. In this paper we present a population synthesis model aimed at galaxies, BHs, and active galactic nuclei (AGNs) at high redshift. The model builds a population based on empirical relations. The spectral energy distribution of galaxies is determined by age and metallicity, and that of AGNs by BH mass and accretion rate. We validate the model against observations, and predict properties of galaxies and AGN in other wavelength and/or luminosity ranges, estimating the contamination of stellar populations (normal stars and high-mass X-ray binaries) for AGN searches from the infrared to X-rays, and vice versa for galaxy searches. For high-redshift galaxies with stellar ages <1 Gyr, we find that disentangling stellar and AGN emission is challenging at restframe UV/optical wavelengths, while high-mass X-ray binaries become more important sources of confusion in X-rays. We propose a color-color selection in the James Webb Space Telescope bands to separate AGN versus star-dominated galaxies in photometric observations. We also estimate the AGN contribution, with respect to massive, hot, and metal-poor stars, at driving high-ionization lines, such as C IV and He II. Finally, we test the influence of the minimum BH mass and occupation fraction of BHs in low-mass galaxies on the restframe UV/near-IR and X-ray AGN luminosity function.
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8

Kinugawa, Tomoya. "The binary population synthesis in the early universe and the detection rate of gravitational waves from the binary black holes". 京都大学 (Kyoto University), 2016. http://hdl.handle.net/2433/215304.

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9

Charisi, Maria. "A Population of Short-Period Variable Quasars from PTF as Supermassive Black Hole Binary Candidates". Thesis, 2017. https://doi.org/10.7916/D88S52C3.

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Supermassive black hole binaries (SMBHBs) are the natural consequence of galaxy mergers and should form frequently in galactic nuclei. Especially at sub-parsec separations, where the binary evolution is slow, SMBHBs should be fairly abundant. However, the observational evidence remains elusive. In this thesis, we focus on periodic variability of quasars as a potential signature of compact SMBHBs. First, we present a systematic search for periodic variability in the photometric database of the Palomar Transient Factory. Our search in a large sample of ~35,000 quasars returned 50 candidates, 33 of which remain significant after the reanalysis of extended light curves including data from the Catalina Real-Time Transient Survey and the intermediate PTF. Our candidates have periods of a few hundred days. Next, we focus on independent signatures that could verify the binary nature of the candidates. We present a case study of quasar PKS 1302-102, the first candidate that emerged from the large time-domain surveys. We search for multiple periodic components in the variability with a characteristic frequency pattern predicted by hydrodynamical simulations of circumbinary disks. We do not find compelling evidence for a secondary period. Additionally, in compact SMBHBs, relativistic Doppler boost should be significant and may dominate the variability. This model was suggested as a smoking-gun signature for quasar PKS 1302-102, since it is not expected in quasars with a single BH and it offers a robust prediction, which can be tested with multi-wavelength data. With a control sample of non-periodic quasars, we test whether this signature is distinct from the intrinsic multi-wavelength variability of quasars. We concluded that the Doppler boost does not provide a sharp test for SMBHBs.
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10

Singh, Neha. "Exploring compact binary populations with Einstein Telescope". Doctoral thesis, 2021. https://depotuw.ceon.pl/handle/item/4091.

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Einstein Telescope (ET) is a future third-generation gravitational wave detector consisting of three overlapping interferometers, arranged in an equilateral configuration with arm-opening angles of 60 degrees. We perform a joint analysis of short duration gravitational wave signals from compact binary systems, long duration signals from compact binary systems and also analyse the Pop I and Pop II, Pop III and globular cluster compact binary mergers using the current design of the ET. We study the capability of ET as a single instrument for this analysis. The observation with a single instrument implies that the delay time in the detection in multiple detectors cannot be used to constrain the location of the source hence we use different antenna patterns for each of the three detectors that make ET to obtain information to constrain position in the sky and polarization. We present an algorithm to estimate the angles describing the location of the source, the inclination and polarisation of an inspiralling compact binary system using the ratios of the SNRs generated in each of the three detectors in single ET, and also provide estimates of the chirp mass, redshift, mass ratios and total mass of the source. For the short duration signals we conclude that in the best case single ET can constrain the 90% probability area of localization in the sky to a minimum value of ≈ 40 square degrees, for effective signal to noise of ρ ef f = 103. The values of chirp mass M and mass ratio q can also be constrained within 10% for ρ ef f ∼ 100, however the typical accuracies are of the order of 25%. Thus we show that single ET can constrain the distances, chirp masses and mass ratios with 20-30% accuracy for most sources. We take into account the effect of rotation of the Earth on the antenna pattern function to analyse long duration signals from coalescing low mass compact binary systems. We find that in this case the single ET can constrain the 90% probability area of localization in the sky to a minimum value of 6 square degrees, for the effective signal to noise ratio of ρ ef f = 73, but only 1% of binaries can be localised within 500 square degrees. The values of the chirp mass M and mass total mass M can be constrained within 2% while redshift z and luminosity distance D L can be estimated with an error of 10% for ρ ef f = 100 using single ET. We analyze binaries originating in stars from Population I and II, from Pop III and from globular clusters and estimate the constraints on the chirp mass, redshift and merger rate with redshift for these classes of compact object binaries. This analysis shows the capability of single ET to detect and distinguish different compact binary populations. We conclude that ET as a single instrument is capable of detecting and distinguishing different compact binary populations. The mass distributions characteristics of different compact binary populations can also be estimated with single ET assuming that sufficient number of binaries will be detected from each of these populations. We also show that populations are distinguishable in the combined bulk detection.
W niniejszej pracy zajmujemy się analizą potencjału naukowego Teleskopu Einsteina, czyli przyszłego detektora fal grawitacyjnych trzeciej generacji. Teleskop Einsteina ma być zbudowany na planie trójkąta równobocznego, i zawierać po dwa interferometry w każdym wierzchołku. Praca zawiera zarówno analizę krótkotrwałych sygnałów fal grawitacyjnych z koalescencji układów podwójnych obiektów zwartych, jak i analizę sygnałów długotrwałych. W dalszej części pracy metody te zastosowane są do analizy układów podwójnych pochodzących z gwiazd populacji I i II, z populacji III oraz z gromad kulistych. Co istotne w przypadku obserwacji tylko jednym instrumentem nie można lokalizować źródeł za pomocą analizy różnicy czasów przyjścia sygnału w różnych detektorach. W celu rozwiązania tego problemu korzystamy z faktu, że każdy z detektorów ma inną odpowiedź kątową, co pozwala nałożyć ograniczenia na położenie na niebie oraz polaryzację źródła porównując stosunki sygnału do szumu w poszczególnych detektorach. W dalszej części uzyskujemy ograniczenia na masę ćwierku M, masę całkowitą M , stosunek mas q oraz przesunięcie ku czerwieni obserwowanej koalescencji obiektów zwartych. W przypadku sygnałów krótkich najmniejszy obszar lokalizacji na poziomie 90% to 40 stopni kwadratowych, kiedy efektywny stosunek sygnału do szumu wynosi około 103. Błędy wyznaczenia masy ćwierku i stosunku mas dochodzą do 10% dla efektywnego sygnału do szumu około 100, jednakże typowe wartości błędów to 25%. A zatem Teleskop Einsteina, jako pojedynczy instrument, powala wyznaczyć przesunięcie ku czerwieni, odległość i masę ćwierku dla większości źródeł z dokładnością 20-30%. Dla źródeł długotrwałych uwzględniamy również obrót Ziemi. W tym przypadku najlepsza lokalizacja to około 6 stopni kwadratowych dla efektywnego sygnału do szumu około 73. Jednakże tylko 1% źródeł może być zlokalizowanych z dokładnością poniżej 500 stopni kwadratowych. Wartości masy ćwierku i całkowitej masy układu mogą być wyznaczone z dokładnością osiągającą 2%, podczas gdy przesuniecie ku czerwieni i odległość z dokładnością dochodzącą do 10% dla efektywnego sygnału do szumu około 100. Ostatnia część pracy poświęcona jest analizie syntetycznych populacji układów podwójnych obiektów zwartych pochodzących z gwiazd populacji I i II, z populacji III oraz z gromad kulistych. Wyznaczamy dla każdej nich rozkłady wykrytych mas ćwierku, mas całkowitych i przesunięć ku czerwieni oraz zależność tempa koalescencji od przesunięcia ku czerwieni. Ta analiza pokazuje, że Teleskop Einsteina jako pojedynczy instrument, jest w stanie wykryć i rozróżnić poszczególne populacje układów podwójnych. Ponadto Teleskop Einsteina będzie mógł określić rozkłady masy i przesunięć ku czerwieni poszczególnych populacji zakładając, że każda z nich jest odpowiednio liczna.
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Libri sul tema "Black hole population"

1

Charisi, Maria. A Population of Short-Period Variable Quasars from PTF as Supermassive Black Hole Binary Candidates. [New York, N.Y.?]: [publisher not identified], 2017.

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2

Clark, Christopher J. Gaining Voice. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780190933562.001.0001.

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This book adopts a multifaceted approach to study of black state legislators across the country. Using the descriptive representation framework, multiple facets of black representation are studied. Black seat share is the primary facet considered, and it is measured as the proportion of seats held by blacks in the state legislature. The black representation ratio measures the black seat share relative to the black population share. Parity exists when blacks are represented in the state legislature at a rate that matches their population share. Legislative black caucuses are also studied in this work, representing the institutionalization of the black presence in state legislatures. The first half of the book shows that while black people are critical for explaining black representation in state legislatures, that institutional and non-racial demographic factors also account for the black seat share, black representation ratio, and emergence of state legislative black caucuses. A “demographics is destiny” explanation insufficiently accounts for blacks gaining voice in state legislatures. The second half the book considers the consequences of black representation in state government. On the one hand, a greater black presence increases education spending, black political involvement, and liberalizes black public opinion. On the other hand, an increased black presence is linked with less liberal welfare policy, in particular in places where Democrats hold the majority of state legislative seats. Thus, an increased black presence in the legislature can be seen as a double-edged sword.
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Archer, Richard. The World of Hosea Easton and David Walker. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780190676643.003.0001.

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Hosea Easton and David Walker described and analyzed racism in New England during the late 1820s. New England had initially been more receptive to its black population than were other sections of the United States, but as their populations of free people of African descent dramatically increased, states began to reverse themselves. By the 1820s, laws forbade free people of African descent from marrying whites, employment was limited to the most menial jobs, and education—where available—was inadequate. African Americans could not serve on juries or hold public office. Their housing opportunities were restricted, and they were segregated in church seating. They were barred from theaters, hotels, hospitals, stagecoaches, and steamships. Worst of all, whites denied blacks their humanity. Their belief that people of color were inferior to themselves underlay slavery and racism.
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4

Brown, Karida L. Gone Home. University of North Carolina Press, 2018. http://dx.doi.org/10.5149/northcarolina/9781469647036.001.0001.

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Since the 2016 presidential election, Americans have witnessed countless stories about Appalachia: its changing political leanings, its opioid crisis, its increasing joblessness, and its declining population. These stories, however, largely ignore black Appalachian lives. Karida L. Brown’s Gone Home offers a much-needed corrective to the current whitewashing of Appalachia. In telling the stories of African Americans living and working in Appalachian coal towns, Brown offers a sweeping look at race, identity, changes in politics and policy, and black migration in the region and beyond. Drawn from over 150 original oral history interviews with former and current residents of Harlan County, Kentucky, Brown shows that as the nation experienced enormous transformation from the pre- to the post-civil rights era, so too did black Americans. In reconstructing the life histories of black coal miners, Brown shows the mutable and shifting nature of collective identity, the struggles of labor and representation, and that Appalachia is far more diverse than you think.
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5

Edwards, Erica R. The Other Side of Terror. NYU Press, 2021. http://dx.doi.org/10.18574/nyu/9781479808427.001.0001.

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The year 1968 was the height of the worldwide Black liberation struggle and the beginning of a new era in Black studies and Black culture in the United States. It also marked a turning point for the global reach of US power, which was built on the counterinsurgency honed on Black and other oppressed populations at home. The next five decades consolidated the culture of US empire, with the imperial grammars of Blackness justifying the domestic carceral regime and US and US-backed wars and occupations abroad. This study reveals the troubling ways that the long war on terror relied on the labor and the fantasies of Black women to justify the imperial spread of capitalist democracy. With attention to the way government agencies, intellectual and political elites, corporations, and universities disciplined and surveilled Black women, but also included and celebrated them, it probes the intimacy between security and Black womanhood since 1968. It also carefully chronicles the collective craft of Black feminist organizing and writing on the other side of terror, which tracked the changes in racial power and transformed African American literature and Black studies. With analyses of writers like Toni Cade Bambara, Nikky Finney, June Jordan, Claudia Rankine, and Alice Randall and television shows like Scandal and HBO’s In Treatment, this book weaves together a Black feminist cultural history of the long war on terror.
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Bullock, III, Charles S., Susan A. MacManus, Jeremy D. Mayer e Mark J. Rozell. African American Statewide Candidates in the New South. Oxford University Press, 2022. http://dx.doi.org/10.1093/oso/9780197607428.001.0001.

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African American candidates for statewide office in the United States face unique challenges given the nation’s complicated racial dynamics. At the dawn of the twenty-first century, the United States had elected only one African American as governor in its history—L. Douglas Wilder, a grandson of slaves who achieved this historic goal in 1989 in Virginia, once the capital of the Confederacy. Numerous media accounts at the time declared a major breakthrough in racial politics in the United States with one national news magazine actually featuring in bold type on its cover “The End of the Civil War.” More than thirty years since Wilder’s election, while Black candidates have risen to office in states such as Illinois, Massachusetts, and California, there are not many successes for African American candidates seeking statewide office in the South. This is particularly puzzling because Blacks are most numerous in the South, as a percentage of the population. This book includes analyses of the campaigns of mostly unsuccessful and some successful Black statewide candidates in the South. The purpose is to untangle the factors that lead to electoral success for these candidates, and those that continue to hold them back, from the vantage of recent election cycles with some historically close races in the South featuring African American candidates for governor of Florida and Georgia (2018), for lieutenant governor in Virginia (2017), and for the US Senate in South Carolina and Georgia (2020). But statewide contests are not limited to state offices; some of the most important southern campaigns in the twenty-first century have featured Black candidates running in the southern presidential primaries. Most notably, Barack Obama’s 2008 nomination campaign blazed a trail in the South that many believed was a template for a new style of black politics. Examining broader regional demographic and political trends, the authors project that the South is on the threshold of a major breakthrough for African American statewide candidates, which will have a substantial role in not only fundamentally changing the political dynamics of the region, but nationally as well. This change will be driven by not only African American candidates and voters but a rising coalition regionally of minorities and also White voters increasingly willing to vote for Black candidates.
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7

Monforti, Jessica Lavariega. One Hundred Years since Women’s Suffrage. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780190265144.003.0006.

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One hundred years since women won the right to vote in federal elections, the representation of women in elected office falls far below proportionality. The disparity is even greater for women of color: while significant proportions of the US population are Asian American, Black, and Latina women, few women of color hold elective office. Of the ninety-seven women who were elected in 2012 and are serving in the 113th Congress, only nine are Latina. These women are often marginalized by both their ethnorace and their gender. This chapter examines one hundred years of Latina political candidates, those who successfully ran for federal office, and the multiple, intersecting marginalities they faced and conquered in order to win their congressional elections.
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van Rooy, Bertus. English in South Africa. A cura di Markku Filppula, Juhani Klemola e Devyani Sharma. Oxford University Press, 2014. http://dx.doi.org/10.1093/oxfordhb/9780199777716.013.017.

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South African English (SAfE) traces its roots to the 1820 British settlers. From here, it spread to the descendants of Indian indentured labourers, who later shifted to English as home language. English diffused as second language to the indigenous African population and speakers of Afrikaans, and today occupies an important position as language of government, education, business, and the media. SAfE has borrowed vocabulary from Afrikaans, ancestral Indian languages, and in recent years also from other South African languages. Phonetically, SAfE has raised front vowels, the short front /i/ has allophones that range from high front in KIN to centralized in PIN, and a back vowel realization of START. Non-native varieties display various degrees of vowel contrast reduction. The modal must is used more extensively than in other varieties of English, while Black SAfE also uses the progressive aspect for a wider timespan than just temporariness.
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9

Feinberg, Melissa. The Power of the Powerless. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780190644611.003.0006.

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This chapter considers the fear of shortage or scarcity. The Stalinist period was a time of scarcity in Eastern Europe. Shortages of even basic goods were common; accordingly, the West defined Communist regimes as places of extreme deprivation. But when confronted with the spectacle of scarce goods, refugees were anything but powerless. Asked about the material situation at home, they emphasized their cleverness, guile, and ability to work the system in order to acquire whatever they needed. Many told stories of buying and selling on the black market or even denouncing others to improve their daily existence. But although many refugees emphasized how they defied the system, broke the law, and even bribed the police, these tales did not prompt Western analysts to revise their picture of Eastern Europe’s Communist regimes as totalitarian dystopias where the population was held powerless under the shadow of paralyzing fear.
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Rodriguez, Andrea, Alison McFadden, Chris Murray e Catriona Laird. Engaging People from Ethic Minority Groups in Health and Oral Health Research: an infographic. A cura di Siyang Yuan. University of Dundee, 2022. http://dx.doi.org/10.20933/100001268.

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Migrant and BME (Black and Minority Ethnic) groups are more likely to suffer from poorer health and oral health outcomes in general. In Dundee, 10.6% of the population identified as an ethnic minority. However, they have been underrepresented in research and health promotion interventions for decades. This reinforces the importance of using participatory research to capture the realities and health needs of these groups to inform policy and interventions addressing health inequalities. The research project ‘Engaging People from Ethic Minority Groups in Health and Oral Health Research’ aimed to engage individuals from migrant and BME groups and researchers who work with these groups to share their experiences, views and perceived challenges and opportunities to improve migrant and BME groups’ research participation. As a specific objective we wanted to identify effective strategies to engage these socially excluded groups in health and oral health research. This infographic is one of the research outcomes in this project. It was co-designed with migrant and BME women living in Dundee to explore their experience and opinions of participation in health and oral health research. we hope this resource will contribute to improve the inclusivity and to maximise participation of research for a wide range of migrant and BME groups.
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Capitoli di libri sul tema "Black hole population"

1

De Zeeuw, P. T. "Central Black Holes and Dark Halos in Elliptical Galaxies". In Stellar Populations, 215–25. Dordrecht: Springer Netherlands, 1995. http://dx.doi.org/10.1007/978-94-011-0125-7_20.

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Elder, Jamee. "Theory Testing in Gravitational-Wave Astrophysics". In Synthese Library, 57–79. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-26618-8_4.

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AbstractThe LIGO-Virgo Collaboration achieved the first ‘direct detection’ of gravitational waves in 2015, opening a new “window” for observing the universe. Since this first detection (‘GW150914’), dozens of detections have followed, mostly produced by binary black hole mergers. However, the theory-ladenness of the LIGO-Virgo methods for observing these events leads to a potentially-vicious circularity, where general relativistic assumptions may serve to mask phenomena that are inconsistent with general relativity (GR). Under such circumstances, the fact that GR can ‘save the phenomena’ may be an artifact of theory-laden methodology.This paper examines several ways that the LIGO-Virgo observations are used in theory and hypothesis testing, despite this circularity problem. First, despite the threat of vicious circularity, these experiments succeed in testing GR. Indeed, early tests of GR using GW150914 are best understood as a response to the threat of theory-ladenness and circularity. Each test searches for evidence that LIGO-Virgo’s theory-laden methods are biasing their overall conclusions. The failure to find evidence of this places constraints on deviations from the predictions of GR. Second, these observations provide a basis for studying astrophysical and cosmological processes, especially through analyses of populations of events. As gravitational-wave astrophysics transitions into mature science, constraints from early tests of GR provide a scaffolding for these population-based studies. I further characterize this transition in terms of its increasing connectedness to other parts of astrophysics and the prominence of reasoning about selection effects and other systematics in drawing inferences from observations.Overall, this paper analyses the ways that theory and hypothesis testing operate in gravitational-wave astrophysics as it gains maturity. In particular, I show how these tests build on one another in order to mitigate a circularity problem at the heart of the observations.
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Moran, Edward C. "Distant X-Ray Galaxies: Insights from the Local Population". In Supermassive Black Holes in the Distant Universe, 225–43. Dordrecht: Springer Netherlands, 2004. http://dx.doi.org/10.1007/978-1-4020-2471-9_7.

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Haardt, Francesco. "From Population III Stars to (Super)Massive Black Holes". In The Initial Mass Function 50 Years Later, 501–6. Dordrecht: Springer Netherlands, 2005. http://dx.doi.org/10.1007/978-1-4020-3407-7_93.

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King, Chris N., Anna C. Church, Wesley L. James, Rhonda G. Okoth e Karen C. Matthews. "Birth Weight Outcomes for Non-Hispanic Black Women in a Home Visiting Program in Rural Mississippi: Observations from the Field". In Population Change and Public Policy, 81–89. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-57069-9_5.

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Agarwal, Bhaskar. "Primordial gas collapse in the presence of radiation: direct collapse black hole or Population III star?" In Formation of the First Black Holes, 115–24. WORLD SCIENTIFIC, 2019. http://dx.doi.org/10.1142/9789813227958_0006.

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Brown, Karida L. "Introduction". In Gone Home, 1–8. University of North Carolina Press, 2018. http://dx.doi.org/10.5149/northcarolina/9781469647036.003.0001.

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Every mass movement can be traced through the particular conditions under which the migrant self is formed and transformed. This introduction outlines the struggle of black Americans once slavery was outlawed by asking a key question: were they subjects or citizens? Though federal laws gave the now former slaves all the rights of citizens, state and local authorities allowed and enforced segregationist policies. These, in conjunction with various economic pressures, culminated in the African American Great Migration of 1910-1970. Brown, who positions herself as a third-generation descendent of a black Kentucky population that took part in this migration, claims that the collective memory of Appalachian blacks that undertook this stepwise migration deserves more attention.
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Bolton, Charles C. "The FEPC and Black Workers". In Home Front Battles, 65–92. Oxford University Press, 2024. http://dx.doi.org/10.1093/oso/9780197655610.003.0004.

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Abstract In the South, the Fair Employment Practices Committee (FEPC) proved particularly ineffectual in bringing about change. White Southerners had created a system of racial apartheid designed to legally enshrine social, legal, and economic discrimination against its Black population. FDR’s Executive Order 8802, which created the FEPC, endorsed nondiscrimination but provided few mechanisms to enforce it. The South had Black citizens who pressed for change, although challenging White supremacy in the region entailed personal risks. Most employers in the Deep South maintained discriminatory employment practices throughout the war. This chapter looks closely at three examples of how employers in the Deep South that made major contributions to war production managed to evade the requirements of Executive Order 8802 and limit Black industrial employment in the region: the Alabama Dry Dock and Shipbuilding Company in Mobile, Alabama; the Bell Bomber Plant in Marietta, Georgia; and the Ingalls Shipbuilding Corporation in Pascagoula, Mississippi.
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Brown, Karida L. "The Coming of the Coal Industry". In Gone Home, 11–26. University of North Carolina Press, 2018. http://dx.doi.org/10.5149/northcarolina/9781469647036.003.0002.

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This chapter provides historical context for the book and anchors the text in place. Drawing on archival data collected form Kentucky and Alabama-based archives and oral history data collected from African Americans in the sample population, Brown describes the conditions under which the coal mining industry emerged in eastern Kentucky at the turn of the twentieth century. She also describes the economic and social conditions of black life in post-Reconstruction Alabama. Through this historical analysis, Brown reveals the antecedents of the mass migration of African Americans from the Alabama black belt into the coalfields of eastern Kentucky. Moving beyond the individual level push-pull framework of mass migration analysis, this chapter focuses on the role of corporations and fin de siècle northern industrialists in initiating calculated mass migration streams to meet their demand for labor.
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Chu, C. Y. Cyrus. "Age-Specific Population Models: Steady States and Comparative Statics". In Population Dynamics. Oxford University Press, 1998. http://dx.doi.org/10.1093/oso/9780195121582.003.0007.

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Mainstream demographers studying the pattern of human population are used to classifying people by their ages. In the terminology of branching processes, the type space of the stochastic process is a subset of positive real numbers that characterize human ages. This chapter deals with this case and studies the corresponding steady states and comparative statics. I showed in chapter 2 that the dynamics of any type-specific population structure can be described by the equation Nt = QNt·l and that Q is block-decomposable in the age-specific case. The fact that the northeast block of Q being a zero matrix not only helps us derive the eigen-values and eigenvectors of Q but also helps us characterize the dynamic evolution of the birth size. Let Bt be the size of birth at period t, la = p1 × • • • × pa be the probability that a person can survive to age a, and ma be the average number of births per surviving member aged a. We see that the following accounting identity must hold: which is Lotka’s (1939) well-known renewal equation. is useful for deriving the steady-state age distribution. Given the assumption of a time-invariant fertility function mu, the total size of birth Bt, which is a linear combination of birth sizes of all fertile age groups, naturally grows at a constant rate in the steady state.
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Atti di convegni sul tema "Black hole population"

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Maccarone, Thomas J., Arunav Kundu, Stephen E. Zepf, I. C. Shih, Katherine L. Rhode, John J. Salzer, Gilles Bergond et al. "A Black Hole in an Extragalactic Globular Cluster". In A POPULATION EXPLOSION: The Nature & Evolution of X-ray Binaries in Diverse Environments. AIP, 2008. http://dx.doi.org/10.1063/1.2945073.

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Sa̧dowski, Aleksander, Janusz Ziółkowski, Krzysztof Belczyński, Tomasz Bulik, Reba M. Bandyopadhyay, Stefanie Wachter, Dawn Gelino e Christopher R. Gelino. "The Missing Population of Be+Black Hole X-Ray Binaries". In A POPULATION EXPLOSION: The Nature & Evolution of X-ray Binaries in Diverse Environments. AIP, 2008. http://dx.doi.org/10.1063/1.2945087.

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Sadowski, Aleksander. "The Missing Population of Be+Black Hole X-Ray Binaries". In 7th INTEGRAL Workshop. Trieste, Italy: Sissa Medialab, 2009. http://dx.doi.org/10.22323/1.067.0076.

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Ziolkowski, Janusz. "The Missing Population of Be+Black Hole X-Ray Binaries". In VII Microquasar Workshop: Microquasars and Beyond. Trieste, Italy: Sissa Medialab, 2009. http://dx.doi.org/10.22323/1.062.0073.

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Sa̧dowski, Aleksander, Janusz Ziółkowski, Krzysztof Belczyński, Tomasz Bulik, Reba M. Bandyopadhyay, Stefanie Wachter, Dawn Gelino e Christopher R. Gelino. "Calculations of the Galactic Population of Black Hole X-Ray Binaries". In A POPULATION EXPLOSION: The Nature & Evolution of X-ray Binaries in Diverse Environments. AIP, 2008. http://dx.doi.org/10.1063/1.2945086.

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Soleri, P., D. Altamirano, R. Fender, P. Casella, V. Tudose, D. Maitra, R. Wijnands et al. "Multiwavelength Observations of the Black Hole Candidate Swift J1753.5-0127". In A POPULATION EXPLOSION: The Nature & Evolution of X-ray Binaries in Diverse Environments. AIP, 2008. http://dx.doi.org/10.1063/1.2945015.

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Meurs, Evert, Patrick Kavanagh, L. Norci e G. O'Halloran. "Distribution and population size of Black Hole binaries in the Galaxy". In 8th INTEGRAL Workshop “The Restless Gamma-ray Universe”. Trieste, Italy: Sissa Medialab, 2011. http://dx.doi.org/10.22323/1.115.0136.

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Galache, José Luis, Mike R. Garcia, Manuel P. Torres, Danny Steeghs, Steve S. Murray, Benjamin F. Williams, Reba M. Bandyopadhyay, Stefanie Wachter, Dawn Gelino e Christopher R. Gelino. "Monitoring Black Hole X-Ray Transients in M31 with Chandra and HST". In A POPULATION EXPLOSION: The Nature & Evolution of X-ray Binaries in Diverse Environments. AIP, 2008. http://dx.doi.org/10.1063/1.2945061.

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Gelino, Dawn M., Solen Balman, Umit Kiziloglu, Arda Yilmaz, Emrah Kalemci, John A. Tomsick, Reba M. Bandyopadhyay, Stefanie Wachter, Dawn Gelino e Christopher R. Gelino. "The Inclination Angle and Mass of the Black Hole in XTE J1118+480". In A POPULATION EXPLOSION: The Nature & Evolution of X-ray Binaries in Diverse Environments. AIP, 2008. http://dx.doi.org/10.1063/1.2945095.

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Marziani, Paola, S. Terefe Mengistue, A. del Olmo, J. Perea, A. Deconto-Machado, M. Pović, E. Bon e N. Bon. "THE DISK PLUS (FAILED) WIND SYSTEM OF 3C 47: A STORY OF ACCRETION DISKS AND BINARY BLACK HOLES". In VI Conference on Active Galactic Nuclei and ravitational Lensing. Astronomical Observatory Belgrade, Volgina 7, 11060 Belgrade 38, Serbia, 2024. http://dx.doi.org/10.69646/aob24012.

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Optically thick, geometrically thin accretion disks (ADs) around supermassive black holes are thought to contribute to broad-line emission in type-1 active galactic nuclei (AGN). However, observed emission line profiles most often deviate from those expected from a rotating disk, and the role of ADs in contributing to broad Balmer lines and high-ionization UV lines such as CIVλ1549 in radio-loud (RL or “jetted”) AGN remains unclear. We first quantified the low-ionization broad emission line properties of jetted quasars in the main sequence context. We confirm that broad emission lines show large redward asymmetry both in Hβ and Mg IIλ2800, and an unbiased comparison matching black hole mass and Eddington ratio suggests that the most powerful RL quasars show the highest redward asymmetries in Hβ in the general population of AGN. These shifts can be accounted for gravitational and transverse redshift effects, especially for black hole masses larger than MBH ≈ 108.7 M⊙. The analysis of the extremely jetted quasar 3C 47 added another piece to the puzzle: not only are the low ionization profiles of 3C 47 well-described by a relativistic Keplerian AD model, with disk emission between ≈ 100 and ≈ 1000 gravitational radii, but also the high-ionization line profiles can be understood as a combination of disk plus a failed wind contribution that is in turn hiding the disk emission. Constraints on radio properties and line profile variability suggest that the scenario of 3C 47 might involve the presence of a second black hole with secondary-to-primary mass ratio ∼ 0.5−1. We conjecture that the double peakers — type-1 AGN with Balmer line profiles consistent with AD emission — might have their emission truncated by the sweeping effect of a second black hole, and we analyze the implications for the general AGN population.
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Rapporti di organizzazioni sul tema "Black hole population"

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Chen, Gengbin, Tuo Lin, Manfeng Wu, Guiyuan Cai, Qian Ding, Jiayue Xu, Wanqi Li, Cheng Wu, Hongying Chen e Yue Lan. Effects of repetitive transcranial magnetic stimulation on upper-limb and finger function in stroke patients: a systematic review and meta-analysis of randomized controlled trials. INPLASY - International Platform of Registered Systematic Review and Meta-analysis Protocols, maggio 2022. http://dx.doi.org/10.37766/inplasy2022.5.0121.

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Review question / Objective: P:Adult patients (age ≥ 18 years) diagnosed with stroke based on relevant clinical examination; I:Intervention group with rTMS alone or in combination with other treatments with rTMS; C:Control group received sham treatment or no rTMS; O: Upper extremity function:the Fugl-Meyer Assessment Upper Extremity (FMA-UE); Hand function:box and block test(BBT), nine-hole peg test(NHPT), and Purdue pegboard test(PPT); S:Randomized controlled trials (rather than crossover designs). Condition being studied: In Europe, more than 1 million new cases of stroke are reported each year. The absolute number of stroke patients is expected to increase in the near future due to the progressive aging of the population. Approximately 50-80% of stroke survivors present with upper extremity dysfunction. Recovery of upper extremity function is associated with improvements in activities of daily living and mental health. However, few stroke survivors show full recovery of upper extremity function 6 months after stroke. In addition, rehabilitation has a limited impact on the recovery of hand motor function.
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DeSaix, Matthew. Bird community monitoring at New River Gorge National River, Gauley River National Recreation Area, and Bluestone National Scenic River, 1997 - 2018. National Park Service, gennaio 2022. http://dx.doi.org/10.36967/nrr-2289846.

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Birds are prominent features of National Park Service lands and are effective indicators for monitoring ecosystem health. Assessing the temporal change of avian species abundance depends on long-term monitoring of bird communities and trends, however long-term monitoring programs are generally uncommon. In this report, we summarize 22 years (1997-2018) of point count data across five sites on West Virginia National Park Service lands (three in New River Gorge National River, one in Gauley River National Recreation Area, and one in Bluestone National Scenic River) and compare these results to our analysis of Breeding Bird Survey data for the same time period across all of West Virginia. The objectives of this analysis are two-fold: 1) describe the biotic integrity of the National Park Service lands in West Virginia and 2) Quantify trends in guilds and species abundance. During the 20-year period of this survey, 85 breeding resident species were detected. The West Virginia National Park Service lands are home to stable populations of Wood Thrush and Yellow-billed Cuckoo, both species of continental concern by Partners in Flight. Seven species have declined precipitously on NPS lands during this time period. Three of these species are also experiencing declines across the rest of West Virginia (Blue-gray Gnatcatcher, Carolina Chickadee, Kentucky Warbler), but the other 4 species are stable across West Virginia (Acadian Flycatcher, Black-throated Green Warbler, Northern Parula, Swainson’s Warbler). Four species that are declining across West Virginia (Great Crested Flycatcher, Indigo Bunting, Red-eyed Vireo, and Worm-eating Warbler) are stable on southern West Virginia NPS lands. Additionally, the upper-canopy foraging guild of species has decreased significantly on NPS lands in southern West Virginia. An analysis of community biotic integrity revealed that the southern West Virginia NPS lands have been stable at a rating of high biotic integrity every year for the duration of this survey. Future research should delve into the underlying factors that may be driving the trends in abundance at different scales.
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