A New Estimate of the Best Value for the Solar Galactocentric Distance
TL;DR: In this paper, a list of individual estimates of the solar Galactocentric distance, which were performed after 2017 by different methods, was made and used to calculate the best value of mean values.
Abstract: Using data from the literature, we made a list of individual estimates of the solar Galactocentric distance, which were performed after 2017 by different methods. These values have not yet been used to calculate the best value of mean $${{R}_{0}}$$
. For the sample containing 21 estimates, based on the standard approach, we found the weighted mean $${{\bar {R}}_{0}} = 8.14$$
kpc with the dispersion $$\sigma = 0.16$$
kpc, and using the median statistics, we obtained the estimate $${{R}_{0}} = 8.15 \pm 0.11$$
kpc. For practical use, the value $${{R}_{0}} = 8.1 \pm 0.1$$
kpc can be recommended.
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11 Jul 2022
TL;DR: In this paper , two complementary NuSTAR x-ray searches for keV-scale dark matter decaying to monoenergetic photons in the Milky Way halo were conducted, using the known intensity pattern of unfocused stray light across the detector planes to separate astrophysical emission from internal instrument backgrounds using ∼ 7-Ms/detector deep blank-sky exposures.
Abstract: We present two complementary NuSTAR x-ray searches for keV-scale dark matter decaying to monoenergetic photons in the Milky Way halo. In the first, we utilize the known intensity pattern of unfocused stray light across the detector planes—the dominant source of photons from diffuse sources—to separate astrophysical emission from internal instrument backgrounds using ∼ 7- Ms/detector deep blank-sky exposures. In the second, we present an updated parametric model of the full NuSTAR instrument background, allowing us to leverage the statistical power of an independent ∼ 20-Ms/detector stacked exposures spread across the sky. Finding no evidence of anomalous x-ray lines using either method, we set limits on the active-sterile mixing angle sin 2 (2 θ ) for sterile-neutrino masses 6–40 keV. The first key result is that we strongly disfavor a ∼ 7-keV sterile neutrino decaying into a 3.5-keV photon. The second is that we derive leading limits on sterile neutrinos with masses ∼ 15–18 keV and ∼ 25–40 keV, reaching or extending below the big bang nucleosynthesis limit. In combination with previous results, the parameter space for the neutrino minimal standard model is now nearly closed.
12 citations
TL;DR: In this article , the authors consider non-rotating primordial black holes (PBHs) formed in the early Universe are sources of neutrinos emitted via Hawking radiation and derive constraints on the abundance of comet-mass PBHs derived from the null observation of this neutrino flux.
Abstract: Primordial black holes (PBHs) formed in the early Universe are sources of neutrinos emitted via Hawking radiation. Such astrophysical neutrinos could be detected at Earth and constraints on the abundance of comet-mass PBHs could be derived from the null observation of this neutrino flux. Here, we consider non-rotating PBHs and improve constraints using Super-Kamiokande neutrino data, as well as we perform forecasts for next-generation neutrino (Hyper-Kamiokande, JUNO, DUNE) and dark matter (DARWIN, ARGO) detectors, which we compare. For PBHs less massive than ∼ few × 1014 g, PBHs would have already evaporated by now, whereas more massive PBHs would still be present and would constitute a fraction of the dark matter of the Universe. We consider monochromatic and extended (log-normal) mass distributions, and a PBH mass range spanning from 1012 g to ∼ 1016 g. Finally, we also compare our results with previous ones in the literature.
7 citations
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TL;DR: The Two Micron All Sky Survey (2MASS) as mentioned in this paper collected 25.4 Tbytes of raw imaging data from two dedicated 1.3 m diameter telescopes located at Mount Hopkins, Arizona and CerroTololo, Chile.
Abstract: Between 1997 June and 2001 February the Two Micron All Sky Survey (2MASS) collected 25.4 Tbytes of raw imagingdatacovering99.998%ofthecelestialsphereinthenear-infraredJ(1.25 � m),H(1.65 � m),andKs(2.16 � m) bandpasses. Observations were conducted from two dedicated 1.3 m diameter telescopes located at Mount Hopkins, Arizona,andCerroTololo,Chile.The7.8sofintegrationtimeaccumulatedforeachpointontheskyandstrictquality control yielded a 10 � point-source detection level of better than 15.8, 15.1, and 14.3 mag at the J, H, and Ks bands, respectively, for virtually the entire sky. Bright source extractions have 1 � photometric uncertainty of <0.03 mag and astrometric accuracy of order 100 mas. Calibration offsets between any two points in the sky are <0.02 mag. The 2MASS All-Sky Data Release includes 4.1 million compressed FITS images covering the entire sky, 471 million source extractions in a Point Source Catalog, and 1.6 million objects identified as extended in an Extended Source Catalog.
12,126 citations
TL;DR: In this paper, the authors present the results of 16 years of monitoring stellar orbits around the massive black hole in the center of the Milky Way, using high-resolution near-infrared techniques.
Abstract: We present the results of 16 years of monitoring stellar orbits around the massive black hole in the center of the Milky Way, using high-resolution near-infrared techniques. This work refines our previous analysis mainly by greatly improving the definition of the coordinate system, which reaches a long-term astrometric accuracy of 300 μas, and by investigating in detail the individual systematic error contributions. The combination of a long-time baseline and the excellent astrometric accuracy of adaptive optics data allows us to determine orbits of 28 stars, including the star S2, which has completed a full revolution since our monitoring began. Our main results are: all stellar orbits are fit extremely well by a single-point-mass potential to within the astrometric uncertainties, which are now 6× better than in previous studies. The central object mass is , where the fractional statistical error of 1.5% is nearly independent from R 0, and the main uncertainty is due to the uncertainty in R 0. Our current best estimate for the distance to the Galactic center is R 0 = 8.33 ± 0.35 kpc. The dominant errors in this value are systematic. The mass scales with distance as (3.95 ± 0.06) × 106(R 0/8 kpc)2.19 M ☉. The orientations of orbital angular momenta for stars in the central arcsecond are random. We identify six of the stars with orbital solutions as late-type stars, and six early-type stars as members of the clockwise-rotating disk system, as was previously proposed. We constrain the extended dark mass enclosed between the pericenter and apocenter of S2 at less than 0.066, at the 99% confidence level, of the mass of Sgr A*. This is two orders of magnitudes larger than what one would expect from other theoretical and observational estimates.
1,787 citations
TL;DR: In this paper, the authors review the key integrated, structural and kinematic parameters of the Galaxy, and point to uncertainties as well as directions for future progress, and show that the Galaxy is a luminous (L⋆) barred spiral with a central box/peanut bulge, a dominant disk, and a diffuse stellar halo.
Abstract: Our Galaxy, the Milky Way, is a benchmark for understanding disk galaxies. It is the only galaxy whose formation history can be studied using the full distribution of stars from faint dwarfs to supergiants. The oldest components provide us with unique insight into how galaxies form and evolve over billions of years. The Galaxy is a luminous (L⋆) barred spiral with a central box/peanut bulge, a dominant disk, and a diffuse stellar halo. Based on global properties, it falls in the sparsely populated “green valley” region of the galaxy color-magnitude diagram. Here we review the key integrated, structural and kinematic parameters of the Galaxy, and point to uncertainties as well as directions for future progress. Galactic studies will continue to play a fundamental role far into the future because there are measurements that can only be made in the near field and much of contemporary astrophysics depends on such observations.
1,084 citations
Pontifical Catholic University of Chile1, University of Hertfordshire2, Queen Mary University of London3, European Southern Observatory4, National University of Cordoba5, University of Michigan6, University of La Serena7, University of Florida8, University of São Paulo9, Space Telescope Science Institute10, Universidade Federal do Rio Grande do Sul11, Valparaiso University12, University of Chile13, Chinese Academy of Sciences14, University of Sheffield15, Hungarian Academy of Sciences16, Imperial College London17, National University of La Plata18, University of Concepción19, Max Planck Society20, University of Cambridge21, University of Manchester22, Spanish National Research Council23, University of Southampton24, INAF25, Rochester Institute of Technology26, European Space Research and Technology Centre27, University of Padua28, Andrés Bello National University29, University of Leicester30, Hartebeesthoek Radio Astronomy Observatory31, University of Kent32
TL;DR: In this article, the authors proposed a method to solve the problem of single-input single-output (SISO) communication in the context of artificial neural networks (ANNs).
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