227 research outputs found
PERANCANGAN VLAN PADA PT VIRGO RAMAYANA RECORD
No full textPERANCANGAN VLAN PADA PT VIRGO RAMAYANA RECORD
Commissioning status of the Virgo interferometer
No full textAn Erratum for this article has been published in 2010 Class. Quantum Grav. 27 149801 (The full author list for this article was omitted in error).International audienceThe Virgo interferometer is one of the big observatories aimed at detecting gravitational waves. This paper will describe the Virgo + upgrades and the commissioning work performed between the first Virgo science run (VSR1) and the second Virgo science run (VSR2). Some first results of VSR2 will be discussed, which was recently started with a good duty cycle and an inspiral range for the detection of binary neutron-star inspirals of 10 Mpc. To conclude, an outlook will be given on some future upgrades of the detector
The Next Generation Virgo Cluster Survey. XXXIV. Ultracompact Dwarf Galaxies in the Virgo Cluster
No full text70 pages, 24 figures, 6 tables, accepted for publication in ApJSInternational audienceWe present a study of ultra compact dwarf (UCD) galaxies in the Virgo cluster based mainly on imaging from the Next Generation Virgo Cluster Survey (NGVS). Using ∼100 deg 2 of u * giz imaging , we have identified more than 600 candidate UCDs, from the core of Virgo out to its virial radius. Candidates have been selected through a combination of magnitudes, ellipticities, colors, surface bright-nesses, half-light radii and, when available, radial velocities. Candidates were also visually validated from deep NGVS images. Subsamples of varying completeness and purity have been defined to explore the properties of UCDs and compare to those of globular clusters and the nuclei of dwarf galaxies with the aim of delineating the nature and origins of UCDs. From a surface density map, we find the UCDs to be mostly concentrated within Virgo's main subclusters, around its brightest galaxies. We identify Corresponding author: Chengze Liu [email protected] arXiv:2007.15275v1 [astro-ph.GA] 30 Jul 2020 2 Liu et al. several subsamples of UCDs-i.e., the brightest, largest, and those with the most pronounced and/or asymmetric envelopes-that could hold clues to the origin of UCDs and possible evolutionary links with dwarf nuclei. We find some evidence for such a connection from the existence of diffuse envelopes around some UCDs, and comparisons of radial distributions of UCDs and nucleated galaxies within the cluster
IceCube-Gen2: A Vision for the Future of Neutrino Astronomy in Antarctica
No full text20 pages, 12 figures. Address correspondence to: E. Blaufuss, F. Halzen, C. Kopper (Changed to add one missing author, no other changes from initial version.)20 pages, 12 figures. Address correspondence to: E. Blaufuss, F. Halzen, C. Kopper (Changed to add one missing author, no other changes from initial version.)20 pages, 12 figures. Address correspondence to: E. Blaufuss, F. Halzen, C. Kopper (Changed to add one missing author, no other changes from initial version.)The recent observation by the IceCube neutrino observatory of an astrophysical flux of neutrinos represents the "first light" in the nascent field of neutrino astronomy. The observed diffuse neutrino flux seems to suggest a much larger level of hadronic activity in the non-thermal universe than previously thought and suggests a rich discovery potential for a larger neutrino observatory. This document presents a vision for an substantial expansion of the current IceCube detector, IceCube-Gen2, including the aim of instrumenting a volume of clear glacial ice at the South Pole to deliver substantial increases in the astrophysical neutrino sample for all flavors. A detector of this size would have a rich physics program with the goal to resolve the sources of these astrophysical neutrinos, discover GZK neutrinos, and be a leading observatory in future multi-messenger astronomy programs
Recommended from our members
Searches for Gravitational Waves from Known Pulsars at Two Harmonics in the Second and Third LIGO-Virgo Observing Runs
No full textWe present a targeted search for continuous gravitational waves (GWs) from 236 pulsars using data from the third observing run of LIGO and Virgo (O3) combined with data from the second observing run (O2). Searches were for emission from the l = m = 2 mass quadrupole mode with a frequency at only twice the pulsar rotation frequency (single harmonic) and the l = 2, m = 1, 2 modes with a frequency of both once and twice the rotation frequency (dual harmonic). No evidence of GWs was found, so we present 95% credible upper limits on the strain amplitudes h0 for the single-harmonic search along with limits on the pulsars' mass quadrupole moments Q22 and ellipticities ε. Of the pulsars studied, 23 have strain amplitudes that are lower than the limits calculated from their electromagnetically measured spin-down rates. These pulsars include the millisecond pulsars J0437-4715 and J0711-6830, which have spin-down ratios of 0.87 and 0.57, respectively. For nine pulsars, their spin-down limits have been surpassed for the first time. For the Crab and Vela pulsars, our limits are factors of ∼100 and ∼20 more constraining than their spin-down limits, respectively. For the dual-harmonic searches, new limits are placed on the strain amplitudes C21 and C22. For 23 pulsars, we also present limits on the emission amplitude assuming dipole radiation as predicted by Brans-Dicke theory. © 2022. The Author(s)Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
The Next Generation Virgo Cluster Survey. VIII. The spatial distribution of globular clusters in the virgo cluster
No full textWe report on a large-scale study of the distribution of globular clusters (GCs) throughout the Virgo cluster, based on photometry from the Next Generation Virgo Cluster Survey (NGVS), a large imaging survey covering Virgo's primary subclusters (Virgo A = M87 and Virgo B = M49) out to their virial radii. Using the g \u2032 o, (g \u2032 - i \u2032)o color-magnitude diagram of unresolved and marginally resolved sources within the NGVS, we have constructed two-dimensional maps of the (irregular) GC distribution over 100 deg2 to a depth of g \u2032 o =24.We present the clearest evidence to date showing the difference in concentration between red and blue GCs over the full extent of the cluster, where the red (more metal-rich) GCs are largely located around the massive early-type galaxies in Virgo, while the blue (metal-poor) GCs have a much more extended spatial distribution with significant populations still present beyond 83\u2032 (~215 kpc) along the major axes of both M49 and M87. A comparison of our GC maps to the diffuse light in the outermost regions of M49 and M87 show remarkable agreement in the shape, ellipticity, and boxiness of both luminous systems. We also find evidence for spatial enhancements of GCs surrounding M87 that may be indicative of recent interactions or an ongoing merger history. We compare the GC map to that of the locations of Virgo galaxies and the X-ray intracluster gas, and find generally good agreement between these various baryonic structures.We calculate the Virgo cluster contains a total population of NGC = 67,300\ub114,400, of which 35% are located in M87 and M49 alone. For the first time, we compute a cluster-wide specific frequency SN,CL = 2.8\ub10.7, after correcting for Virgo's diffuse light. We also find a GC-to-baryonic mass fraction \u3b5b = 5.7 \ub1 1.1
7 10-4 and a GC-to-total cluster mass formation efficiency \u3b5t = 2.9 \ub1 0.5
7 10-5, the latter values slightly lower than but consistent with those derived for individual galactic halos. Taken as a whole, our results show that the production of the complex structures in the unrelaxed Virgo cluster core (including the production of the diffuse intracluster light) is an ongoing and continuing process.Peer reviewed: YesNRC publication: Ye
Oficjum „Prudens virgo lampadae aptata” jako signum distinctivum liturgii katedry w Würzburgu od XIV do XVI w.
No full textThe author analyzes the Offices of St. Catherine of Alexandria Prudens virgo lampadae present in six sources in Würzburg. It is the Office composed of elements borrowed from other traditions, and original elements. This Office is a characteristic feature of the liturgy of Würzburg Cathedral.Autor analizuje oficja św. Katarzyny Aleksandryjskiej Prudens virgo lampadae obecne w sześciu źródłach w Würzburgu. Jest to oficjum składające się z elementów zapożyczonych z innych tradycji oraz z elementów oryginalnych. Oficjum to stanowi szczególną cechę liturgii katedry w Würzburgu
Improving our ability to distinguish gravitational-wave signals from detector transient noise for the fourth LIGO-Virgo-KAGRA observing run
No full textEsta investigación desarrolla una herramienta para clasificar ondas gravitacionales (GWs) de ruido de detector para informar la aceptación/retractación de eventos de GWs para la colaboración LIGO-Virgo-KAGRA.A pesar de haber alcanzado sensibilidades capaces de detectar la amplitud extremadamente pequeña de las ondas gravitacionales (GWs), los datos de los detectores LIGO y Virgo contienen frecuentes ráfagas de ruido transitorio no Gaussiano, comúnmente conocidas como "glitches". Los "glitches" se presentan en diversas morfologías de tiempo-frecuencia, y resultan especialmente problemáticos cuando imitan la forma de las GWs reales. Dada la mayor tasa de eventos esperada en el actual periodo de observación de LIGO-Virgo (O4), la validación de los candidatos de eventos de GWs requiere mayores niveles de automatización. Gravity Spy, una herramienta de aprendizaje automático que clasificó con éxito tipos comunes de "glitches" de LIGO y Virgo en observaciones anteriores, tiene el potencial de ser reestructurada como un clasificador de señales de GWs-vs-ruido de detector para distinguir entre "glitches" y señales de GW con precisión. Un clasificador de señales de GWs-vs-"glitches" utilizado para la automatización debe ser robusto y compatible con una amplia gama de ruido de fondo, nuevas fuentes de "glitches" y la probable aparición de "glitches" y GWs solapados en la misma ventana de tiempo. Presentamos GSpyNetTree, el Gravity Spy Convolutional Neural Network Decision Tree: un clasificador multi-etiqueta multi-CNN que utiliza CNNs en un árbol de decisión ordenado a través de la masa total de un evento candidato de onda gravitacional. Integrado en el Informe de Calidad de Datos de LIGO-Virgo (DQR, por sus siglas en inglés), GSpyNetTree es una de las herramientas esenciales en la evaluación de la necesidad de mitigación de "glitches" en O4. Esta tesis presenta el desarrollo de GSpyNetTree, su construcción y resultados, desde su origen como un clasificador multi-clase a su estado actual como clasificador multi-etiqueta. Por último, se evalúa su desempeño en candidatos de ondas gravitacionales del actual periodo de observación, O4, y se proponen técnicas para mejorar su desempeño en futuras iteraciones.Despite achieving sensitivities capable of detecting the extremely small amplitude of gravitational waves (GWs), LIGO and Virgo detector data contain frequent bursts of non-Gaussian transient noise, commonly known as 'glitches'. Glitches come in various time-frequency morphologies, and they are particularly challenging when they mimic the form of real GWs. Given the higher expected event rate in the current observing run (O4), LIGO-Virgo GW event candidate validation requires increased levels of automation. Gravity Spy, a machine learning tool that successfully classified common types of LIGO and Virgo glitches in previous observing runs, has the potential to be restructured as a signal-vs-glitch classifier to distinguish between glitches and GW signals accurately. A signal-vs-glitch classifier used for automation must be robust and compatible with a broad array of background noise, new sources of glitches, and the likely occurrence of overlapping glitches and GWs. This dissertation presents GSpyNetTree, the Gravity Spy Convolutional Neural Network Decision Tree: a multi-CNN multi-label classifier using CNNs in a decision tree sorted via total GW candidate mass. Integrated into the LIGO-Virgo Data Quality Report, GSpyNetTree is one of the essential tools in assessing the necessity of glitch mitigation in O4. This thesis presents the development, building process, and results of GSpyNetTree: from its origin as a multi-class classifier based on Gravity Spy, to its current O4 status as a multi-label classifier. Finally, the performance of GSpyNetTree identifying data quality issues in the public O4 GW candidates published in GraceDB is evaluated, and new ways to improve the tool's classifications are suggested.This material is based upon work supported by NSF's LIGO Laboratory, which is a major facility fully funded by the National Science Foundation.
The author is grateful for computational resources provided by the LIGO Laboratory and supported by National Science Foundation Grants PHY-0757058 and PHY-0823459.FísicoPregradoOndas gravitacionale
Relating Modified Newtonian Dynamics to Dark matter: Application to a Virgo-like Galaxy cluster
No full textIn this thesis Modified Newtonian Dynamics (MOND) is explored in galaxy clusters similar to the Virgo cluster. MOND is a theory proposed to explain the flat rotation curves of galaxies and the velocities of galaxies within galaxy clusters, as an alternative to the Dark Matter (DM) model. MOND states that Newton’s law of gravitation is incorrect at accelerations of the order of and smaller than Milgrom’s constant a_0 = 1.2 · 10^−10m/s^2 [1]. The MOND potential φ_M created by a certain mass distribution ρ satisfies the MOND equation, a non-linear partial differential equation. For accelerations much smaller than a0 this equation gives a quadratic relation between the gradient of the potential (∇φ_M) and the mass distribution ρ, this is called deep MOND. This is much different from the Poisson equation, that infers a linear relation between ∇φ_M and the mass sources, and which still holds for accelerations much larger than a_0 [1], referred to as Newtonian Dynamics (ND). For accelerations around a0 an interpolation of deep MOND and ND is used. It appears that the potential and acceleration in Virgo-like clusters is according to ND at the center, and approaches deep MOND at the edge. Therefore an interpolation function µ is necessary to model such clusters accurately.When the MOND potential φ_M is substituted into the Poisson equation, a new mass distribution is found, the apparent mass distribution ρ_AM, which would need to match the actual mass distribution in DM models, which use the Poisson equation. This apparent mass distribution ρ_AM is the sum of the actual mass distribution ρ extracted from optical observations and the apparent dark mass distribution ρ_ADM, a distribution that is interpreted as a theoretical DM halo. This allows us to compare MOND and DM. With our method, realistic mass configurations of galaxy clusters that are Virgo-like, generate apparent mass distributions ρ_AM with regions containing negative mass. The existence, shapes and locations of these regions are in agreement with what Milgrom found [2]. The total mass of the actual mass distribution is M = 10^15M_sun, while the sum of the negative mass is M_negative ≈ −0.09 · 10^15M_sun = −0.09M is approximately 9% of the total mass. Since negative mass is not acceptable, this gives us the opportunity to create conditions to falsify either the MOND model or the DM model. Applied Mathematics | Applied Physic
The globular cluster systems of the three Virgo ellipticals
No full textAn analysis of the systems of globular clusters around three of the brightest elliptical galaxies in the Virgo cluster (NGC 4406, NGC 4472, and NGC 4486) has been carried out with a digital detector whose field is 9 arcmin on a side. The point-source detections reach to g = 25 mag, and nearly all galaxies brighter than g ≈ 22.5 mag can be eliminated. The author finds that the colors of the globular clusters show no detectable spatial gradient, and that the median color and the distribution in color are independent of cluster luminosity and spatial position within the halo of the underlying elliptical galaxy. The median color of the Virgo globular systems is slightly redder than that of the set of globulars in the Milky Way, implying a mean metallicity difference of about a factor of 3. The magnitude distribution is not a power law, having a definite turnover at g ≈ 24.2 mag, which constrains the distance to the Virgo cluster if one believes in a universal globular cluster luminosity function. In each of the three cases, the globular cluster system has the same ellipticity and position angle as the light of the halo of the underlying galaxy, but is more extended spatially in the case of NGC 4472 and NGC 4486
- …
