Showing papers by "Smithsonian Astrophysical Observatory published in 2018"

Estimates of the Global Burden of Ambient PM2.5, Ozone, and NO2 on Asthma Incidence and Emergency Room Visits

Abstract: Background: Asthma is the most prevalent chronic respiratory disease worldwide, affecting 358 million people in 2015. Ambient air pollution exacerbates asthma among populations around the world and...

Cosmic evolution and metal aversion in superluminous supernova host galaxies

Abstract: SS acknowledges support from the CONICYT-Chile FONDECYT Postdoctorado fellowship 3140534 and the Feinberg Graduate School. SS and FEB acknowledge support from Basal-CATA PFB-06/2007, and Project IC120009 'Millennium Institute of Astrophysics (MAS)' of Iniciativa Cientifica Milenio del Ministerio de Economia, Fomento y Turismo. TK acknowledges support through the Sofja Kovalevskaja Award to P. Schady from the Alexander von Humboldt Foundation of Germany. AdUP and CT acknowledge support from the Ramon y Cajal fellowships and the Spanish Ministry of Economy and Competitiveness through project AyA2014-58381-P. RA acknowledges support from the European Research Council Advanced Grant c 'QUENCH'.r This paper is based partly on observations made with: ESO Telescopes at the La Silla Paranal Observatory; the 6.5-m Magellan Telescopes located at the Las Campanas Observatory, Chile; the GTC), installed in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias, in the island of La Palma; the CAHA at Calar Alto, Spain, operated jointly by the Max-Planck Institut fur Astronomie and the Instituto de Astrofisica de Andalucia (CSIC); the Nordic Optical Telescope, operated by the Nordic Optical Telescope Scientific Association at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofisica de Canarias; and Karl G. JVLA, New Mexico, United States of America. This research draws upon data provided by Cypriano as distributed by the National Optical Astronomy Observato (NOAO) Science Archive. NOAO is operated by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. This publication makes use of data products from the WISE, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. GALEX (Galaxy Evolution Explorer) is a NASA Small Explorer, launched in 2003 April. We gratefully acknowledge NASA's support for construction, operation, and science analysis for the GALEX mission, developed in cooperation with the Centre National d'Etudes Spatiales of France and the Korean Ministry of Science and Technology. Based in part on data collected at the Subaru Telescope, Hawaii, United States of America, which is operated by the National Astronomical Observatory of Japan. The NRAO) is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. Part of the funding for GROND was generously granted from the Leibniz-Prize to Prof G. Hasinger (DFG grant HA 1850/28-1).r Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy Office of Science. The SDSS-III web site is http://www.sdss3.org/. SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration, including the University of Arizona, the Brazilian Participation Group, Brookhaven National Laboratory, University of Cambridge, Carnegie Mellon University, University of Florida, the French Participation Group, the German Participation Group, Harvard University, the Instituto de Astrofisica de Canarias, the Michigan State/Notre Dame/JINA Participation Group, Johns Hopkins University, Lawrence Berkeley National Laboratory, Max Planck Institute for Astrophysics, Max Planck Institute for Extraterrestrial Physics, New Mexico State University, New York University, Ohio State University, Pennsylvania State University, University of Portsmouth, Princeton University, the Spanish Participation Group, University of Tokyo, University of Utah, Vanderbilt University, University of Virginia, University of Washington, and Yale University. Based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/IRFU, at CFHT, which is operated by the National Research Council (NRC) of Canada, the Institut National des Science de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France and the University of Hawaii. This work is partly based on data products produced at Terapix available at the Canadian Astronomy Data Centre as part of the CFHTLS, a collaborative project of NRC and CNRS.r This project used public archival data obtained withthe Dark Energy Camera by the Dark Energy Survey (DES). Funding for the DES Projects has been provided by the DOE and NSF (USA), MISE (Spain), STFC (UK), HEFCE (UK), NCSA (UIUC), KICP (U. Chicago), CCAPP (Ohio State), MIFPA (Texas A&M), CNPQ, FAPERJ, FINEP (Brazil), MINECO (Spain), DFG (Germany), and the collaborating institutions in the DES, which are Argonne Lab, UC Santa Cruz, University of Cambridge, CIEMAT-Madrid, University of Chicago, University College London, DES-Brazil Consortium, University of Edinburgh, ETH Zurich, Fermilab, University of Illinois, ICE (IEEC-CSIC), IFAE Barcelona, Lawrence Berkeley Lab, LMU Munchen and the associated Excellence Cluster Universe, University of Michigan, NOAO, University of Nottingham, Ohio State University, University of Pennsylvania, University of Portsmouth, SLAC National Lab, Stanford University, University of Sussex, and Texas A&M University.r This research has made use of the NASA/IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory and the California Institute of Technology, under contract with the National Aeronautics and Space Administration.

Understanding the Internal Magnetic Field Configurations of ICMEs Using More than 20 Years of Wind Observations

Abstract: The magnetic topology, structure, and geometry of the magnetic obstacles embedded within interplanetary coronal mass ejections (ICMEs) are not yet fully and consistently described by in situ models and reconstruction techniques. The main goal of this work is to better understand the status of the internal magnetic field of ICMEs and to explore in situ signatures to identify clues to develop a more accurate and reliable in situ analytical models. We take advantage of more than 20 years of Wind observations of transients at 1 AU to compile a comprehensive database of ICMEs through three solar cycles, from 1995 to 2015. The catalog is publicly available at and is fully described in this article. We identify and collect the properties of 337 ICMEs, of which 298 show organized magnetic field signatures. To allow for departures from idealized magnetic configurations, we introduce the term “magnetic obstacle” (MO) to signify the possibility of more complex configurations. To quantify the asymmetry of the magnetic field strength profile within these events, we introduce the distortion parameter (DiP) and calculate the expansion velocity within the magnetic obstacle. Circular-cylindrical geometry is assumed when the magnetic field strength displays a symmetric profile. We perform a statistical study of these two parameters and find that only 35% of the events show symmetric magnetic profiles and a low enough expansion velocity to be compatible with the assumption of an idealized cylindrical static flux rope, and that 41% of the events do not show the expected relationship between expansion and magnetic field compression in the front, with the maximum magnetic field closer to the first encounter of the spacecraft with the magnetic obstacle; 18% show contractions (i.e. apparent negative expansion velocity), and 30% show magnetic field compression in the back. We derive an empirical relation between DiP and expansion velocity that is the first step toward improving reconstructions with possible applications to space weather studies. In summary, our main results demonstrate that the assumed correlation between expanding structure and asymmetric magnetic field is not always valid. Although 59% of the cases could be described by circular-cylindrical geometry, with or without expansion, the remaining cases show significant in situ signatures of departures from circular-cylindrical geometry. These results will aid in the development of more accurate in situ models to reconcile image.

A Population of Bona Fide Intermediate-mass Black Holes Identified as Low-luminosity Active Galactic Nuclei

Abstract: Nearly every massive galaxy harbors a supermassive black hole (SMBH) in its nucleus. SMBH masses are millions to billions $M_{\odot}$, and they correlate with properties of spheroids of their host galaxies. While the SMBH growth channels, mergers and gas accretion, are well established, their origin remains uncertain: they could have either emerged from massive "seeds" ($10^5-10^6 M_{\odot}$) formed by direct collapse of gas clouds in the early Universe or from smaller ($100 M_{\odot}$) black holes, end-products of first stars. The latter channel would leave behind numerous intermediate mass black holes (IMBHs, $10^2-10^5 M_{\odot}$). Although many IMBH candidates have been identified, none is accepted as definitive, thus their very existence is still debated. Using data mining in wide-field sky surveys and applying dedicated analysis to archival and follow-up optical spectra, we identified a sample of 305 IMBH candidates having masses $3\times10^4

The Fornax Deep Survey with the VST. IV. A size and magnitude limited catalog of dwarf galaxies in the area of the Fornax cluster

Abstract: Context. The Fornax Deep Survey (FDS), an imaging survey in the u', g', r', and i'-bands, has a supreme resolution and image depth compared to the previous spatially complete Fornax Cluster Catalog (FCC). Our new data allows us to study the galaxies down to r'-band magnitude m(r') approximate to 21 mag (M-r' approximate to -10.5 mag), which opens a new parameter regime to investigate the evolution of dwarf galaxies in the cluster environment. After the Virgo cluster, Fornax is the second nearest galaxy cluster to us, and with its different mass and evolutionary state, it provides a valuable comparison that makes it possible to understand the various evolutionary effects on galaxies and galaxy clusters. These data provide an important legacy dataset to study the Fornax cluster. Aims. We aim to present the Fornax Deep Survey (FDS) dwarf galaxy catalog, focusing on explaining the data reduction and calibrations, assessing the quality of the data, and describing the methods used for defining the cluster memberships and first order morphological classifications for the catalog objects. We also describe the main scientific questions that will be addressed based on the catalog. This catalog will also be invaluable for future follow-up studies of the Fornax cluster dwarf galaxies. Methods. As a first step we used the SExtractor fine-tuned for dwarf galaxy detection, to find galaxies from the FDS data, covering a 26 deg(2) area of the main cluster up to its virial radius, and the area around the Fornax A substructure. We made 2D-decompositions of the identified galaxies using GALFIT, measure the aperture colors, and the basic morphological parameters like concentration and residual flux fraction. We used color-magnitude, luminosity-radius and luminosity-concentration relations to separate the cluster galaxies from the background galaxies. We then divided the cluster galaxies into early- and late-type galaxies according to their morphology and gave first order morphological classifications using a combination of visual and parametric classifications. Results. Our final catalog includes 14 095 galaxies. We classify 590 galaxies as being likely Fornax cluster galaxies, of which 564 are dwarfs (M-r' (') > -18.5 mag) consisting our Fornax dwarf catalog. Of the cluster dwarfs we classify 470 as early-types, and 94 as late-type galaxies. Our final catalog reaches its 50% completeness limit at magnitude M-r' = -10.5 mag and surface brightness (mu) over bar (e,r') = 26 mag arcsec(-2), which is approximately three magnitudes deeper than the FCC. Based on previous works and comparison with a spectroscopically confirmed subsample, we estimate that our final Fornax dwarf galaxy catalog has less than or similar to 10% contamination from the background objects.

Magnetic Field Amplification in Galaxy Clusters and Its Simulation

Abstract: We review the present theoretical and numerical understanding of magnetic field amplification in cosmic large-scale structure, on length scales of galaxy clusters and beyond. Structure formation drives compression and turbulence, which amplify tiny magnetic seed fields to the microGauss values that are observed in the intracluster medium. This process is intimately connected to the properties of turbulence and the microphysics of the intra-cluster medium. Additional roles are played by merger induced shocks that sweep through the intra-cluster medium and motions induced by sloshing cool cores. The accurate simulation of magnetic field amplification in clusters still poses a serious challenge for simulations of cosmological structure formation. We review the current literature on cosmological simulations that include magnetic fields and outline theoretical as well as numerical challenges.

Majority of Solar Wind Intervals Support Ion-Driven Instabilities.

Abstract: We perform a statistical assessment of solar wind stability at 1 AU against ion sources of free energy using Nyquist's instability criterion. In contrast to typically employed threshold models which consider a single free-energy source, this method includes the effects of proton and ${\mathrm{He}}^{2+}$ temperature anisotropy with respect to the background magnetic field as well as relative drifts between the proton core, proton beam, and ${\mathrm{He}}^{2+}$ components on stability. Of 309 randomly selected spectra from the Wind spacecraft, 53.7% are unstable when the ion components are modeled as drifting bi-Maxwellians; only 4.5% of the spectra are unstable to long-wavelength instabilities. A majority of the instabilities occur for spectra where a proton beam is resolved. Nearly all observed instabilities have growth rates $\ensuremath{\gamma}$ slower than instrumental and ion-kinetic-scale timescales. Unstable spectra are associated with relatively large ${\mathrm{He}}^{2+}$ drift speeds and/or a departure of the core proton temperature from isotropy; other parametric dependencies of unstable spectra are also identified.

The Black Hole in the Most Massive Ultracompact Dwarf Galaxy M59-UCD3

Abstract: We examine the internal properties of the most massive ultracompact dwarf galaxy (UCD), M59-UCD3, by combining adaptive-optics-assisted near-IR integral field spectroscopy from Gemini/NIFS and Hubble Space Telescope (HST) imaging. We use the multiband HST imaging to create a mass model that suggests and accounts for the presence of multiple stellar populations and structural components. We combine these mass models with kinematics measurements from Gemini/NIFS to find a best-fit stellar mass-to-light ratio (M/L) and black hole (BH) mass using Jeans anisotropic models (JAMs), axisymmetric Schwarzschild models, and triaxial Schwarzschild models. The best-fit parameters in the JAM and axisymmetric Schwarzschild models have BHs between 2.5 and 5.9 million solar masses. The triaxial Schwarzschild models point toward a similar BH mass but show a minimum χ at a BH mass of ∼0. Models with a BH in all three techniques provide better fits to the central V profiles, and thus we estimate the BH mass to be 4.2 × 10M (estimated 1σ uncertainties). We also present deep radio imaging of M59-UCD3 and two other UCDs in Virgo with dynamical BH mass measurements, and we compare these to X-ray measurements to check for consistency with the fundamental plane of BH accretion. We detect faint radio emission in M59cO but find only upper limits for M60-UCD1 and M59-UCD3 despite X-ray detections in both these sources. The BH mass and nuclear light profile of M59-UCD3 suggest that it is the tidally stripped remnant of a ∼10-10 M galaxy.

The Lynx X-Ray Observatory: Concept Study Overview and Status

Abstract: Lynx, one of four strategic mission concepts under study for the 2020 Astrophysics Decadal Survey, will provide leaps in capability over previous and planned X-ray missions, and will provide synergistic observations in the 2030s to a multitude of space- and ground-based observatories across all wavelengths. Lynx will have orders of magnitude improvement in sensitivity, on-axis sub-arcsecond imaging with arcsecond angular resolution over a large field of view, and high-resolution spectroscopy for point-like and extended sources. The Lynx architecture enables a broad range of unique and compelling science, to be carried out mainly through a General Observer Program. This Program is envisioned to include detecting the very first supermassive black holes, revealing the high-energy drivers of galaxy and structure formation, characterizing the mechanisms that govern stellar activity - including effects on planet habitability, and exploring the highest redshift galaxy clusters. An overview and status of the Lynx concept are summarized.

A 3.5 million Solar masses black hole in the centre of the ultracompact dwarf galaxy fornax UCD3

Abstract: The origin of ultracompact dwarfs (UCDs), a class of compact stellar systems discovered two decades ago, still remains a matter of debate. Recent discoveries of central supermassive black holes in UCDs likely inherited from their massive progenitor galaxies provide support for the tidal stripping hypothesis. At the same time, on statistical grounds, some massive UCDs might be representatives of the high luminosity tail of the globular cluster luminosity function. Here we present a detection of a 3.3(-1.2)(+1.4) x 10(6) M-circle dot black hole (1s uncertainty) in the centre of the UCD3 galaxy in the Fornax cluster, which corresponds to 4 per cent of its stellar mass. We performed isotropic Jeans dynamical modelling of UCD3 using internal kinematics derived from adaptive optics-assisted observations with the SINFONI spectrograph and seeing limited data collected with the FLAMES spectrograph at the ESO VLT. We rule out the zero black hole mass at the 3s confidence level when adopting a mass-to-light ratio inferred from stellar populations. This is the fourth supermassive black hole found in a UCD and the first one in the Fornax cluster. Similarly to other known UCDs that harbour black holes, UCD3 hosts metal rich stars enhanced in a-elements that support the tidal stripping of a massive progenitor as its likely formation scenario. We estimate that up to 80 per cent of luminous UCDs in galaxy clusters host central black holes. This fraction should be lower for UCDs in groups, because their progenitors are more likely to be dwarf galaxies, which do not usually host black holes massive enough to be detected.

Gaia and the Galactic Center Origin of Hypervelocity Stars

Abstract: We use new Gaia measurements to explore the origin of the highest velocity stars in the Hypervelocity Star Survey. The measurements reveal a clear pattern in the B-type stars. Halo stars dominate the sample at speeds about 100 km/s below Galactic escape velocity. Disk runaway stars have speeds up to 100 km/s above Galactic escape velocity, but most disk runaways are bound. Stars with speeds about 100 km/s above Galactic escape velocity originate from the Galactic center. Two bound stars may also originate from the Galactic center. Future Gaia measurements will enable a large, clean sample of Galactic center ejections for measuring the massive black hole ejection rate of hypervelocity stars, and for constraining the mass distribution of the Milky Way dark matter halo.

A refined search for pulsations in white dwarf companions to millisecond pulsars

Abstract: We present optical high-speed photometry of three millisecond pulsars with low-mass ($< 0.3 M_{\odot}$) white dwarf companions, bringing the total number of such systems with follow-up time-series photometry to five. We confirm the detection of pulsations in one system, the white dwarf companion to PSR J1738+0333, and show that the pulsation frequencies and amplitudes are variable over many months. A full asteroseismic analysis for this star is under-constrained, but the mode periods we observe are consistent with expectations for a $M_{\star} = 0.16 - 0.19 M_{\odot}$ white dwarf, as suggested from spectroscopy. We also present the empirical boundaries of the instability strip for low-mass white dwarfs based on the full sample of white dwarfs, and discuss the distinction between pulsating low-mass white dwarfs and subdwarf A/F stars.

A Comparison of Alpha Particle and Proton Beam Differential Flows in Collisionally Young Solar Wind

Abstract: In fast wind or when the local Coulomb collision frequency is low, observations show that solar wind minor ions and ion sub-populations flow with different bulk velocities. Measurements indicate that the drift speed of both alpha particles and proton beams with respect to the bulk or core protons rarely exceeds the local Alfven speed, suggesting that a magnetic instability or other wave-particle process limits their maximum drift. We compare simultaneous alpha particle, proton beam, and proton core observations from instruments on the Wind spacecraft spanning over 20 years. In nearly collisionless solar wind, we find that the normalized alpha particle drift speed is slower than the normalized proton beam speed; no correlation between fluctuations in both species' drifts about their means; and a strong anti-correlation between collisional age and alpha-proton differential flow, but no such correlation with proton beam-core differential flow. Controlling for the collisional dependence, both species' normalized drifts exhibit similar statistical distributions. In the asymptotic, zero Coulomb collision limit, the youngest measured differential flows most strongly correlate with an approximation of the Alfven speed that includes proton pressure anisotropy. In this limit and with this most precise representation, alpha particles drift at 67% and proton beam drift is approximately 105% of the local Alfven speed. We posit that one of two physical explanations is possible. Either (1) an Alfvenic process preferentially accelerates or sustains proton beams and not alphas or (2) alpha particles are more susceptible to either an instability or Coulomb drag than proton beams.

Magnetic Field Amplification in Galaxy Clusters and its Simulation

Abstract: We review the present theoretical and numerical understanding of magnetic field amplification in cosmic large-scale structure, on length scales of galaxy clusters and beyond. Structure formation drives compression and turbulence, which amplify tiny magnetic seed fields to the microGauss values that are observed in the intracluster medium. This process is intimately connected to the properties of turbulence and the microphysics of the intra-cluster medium. Additional roles are played by merger induced shocks that sweep through the intra-cluster medium and motions induced by sloshing cool cores. The accurate simulation of magnetic field amplification in clusters still poses a serious challenge for simulations of cosmological structure formation. We review the current literature on cosmological simulations that include magnetic fields and outline theoretical as well as numerical challenges.

Dust production and depletion in evolved planetary systems

Abstract: The infrared dust emission from the white dwarf GD 56 is found to rise and fall by 20 per cent peak-to-peak over 11.2 yr, and is consistent with ongoing dust production and depletion. It is hypothesized that the dust is produced via collisions associated with an evolving dust disc, temporarily increasing the emitting surface of warm debris, and is subsequently destroyed or assimilated within a few years. The variations are consistent with debris that does not change temperature, indicating that dust is produced and depleted within a fixed range of orbital radii. Gas produced in collisions may rapidly re-condense onto grains, or may accrete onto the white dwarf surface on viscous timescales that are considerably longer than Poynting–Robertson drag for micron-sized dust. This potential delay in mass accretion rate change is consistent with multi-epoch spectra of the unchanging Ca II and Mg II absorption features in GD 56 over 15 yr, although the sampling is sparse. Overall, these results indicate that collisions are likely to be the source of dust and gas, either inferred or observed, orbiting most or all polluted white dwarfs.

Nearby High-speed Stars in Gaia DR2

Abstract: We investigate the nature of nearby (10–15 kpc) high-speed stars in the Gaia DR2 archive identified on the basis of parallax, proper motion and radial velocity. Together with a consideration of their kinematic, orbital, and photometric properties, we develop a novel strategy for evaluating whether high-speed stars are statistical outliers of the bound population or unbound stars capable of escaping the Galaxy. Out of roughly 1.5 million stars with radial velocities, proper motions, and 5σ parallaxes, we identify just over 100 high-speed stars. Of these, only two have a nearly 100% chance of being unbound, with an indication that they are not just bound outliers; both are likely hyper-runaway stars. The rest of the high-speed stars are likely statistical outliers. We use the sample of high-speed stars to demonstrate that radial velocity alone provides a poor discriminant of nearby, unbound stars. However, these stars are efficiently identified from the tangential velocity, using just parallax and proper motion. Within the full Gaia DR2 archive of stars with 5σ parallax and proper motion but no radial velocity, we identify a sample of 19 with speeds significantly larger than the local escape speed of the Milky Way based on tangential motion alone.

GEOS-Chem High Performance (GCHP v11-02c): a next-generation implementation of the GEOS-Chem chemical transport model for massively parallel applications

Abstract: . Global modeling of atmospheric chemistry is a grand computational challenge because of the need to simulate large coupled systems of ∼100 –1000 chemical species interacting with transport on all scales. Offline chemical transport models (CTMs), where the chemical continuity equations are solved using meteorological data as input, have usability advantages and are important vehicles for developing atmospheric chemistry knowledge that can then be transferred to Earth system models. However, they have generally not been designed to take advantage of massively parallel computing architectures. Here, we develop such a high-performance capability for GEOS-Chem (GCHP), a CTM driven by meteorological data from the NASA Goddard Earth Observation System (GEOS) and used by hundreds of research groups worldwide. GCHP is a grid-independent implementation of GEOS-Chem using the Earth System Modeling Framework (ESMF) that permits the same standard model to operate in a distributed-memory framework for massive parallelization. GCHP also allows GEOS-Chem to take advantage of the native GEOS cubed-sphere grid for greater accuracy and computational efficiency in simulating transport. GCHP enables GEOS-Chem simulations to be conducted with high computational scalability up to at least 500 cores, so that global simulations of stratosphere–troposphere oxidant–aerosol chemistry at C180 spatial resolution ( ∼ 0.5 ∘ × 0.625 ∘ ) or finer become routinely feasible.

Instrument Calibration of the Interface Region Imaging Spectrograph (IRIS) Mission

Abstract: The Interface Region Imaging Spectrograph (IRIS) is a NASA small explorer mission that provides high-resolution spectra and images of the Sun in the 133 – 141 nm and 278 – 283 nm wavelength bands. The IRIS data are archived in calibrated form and made available to the public within seven days of observing. The calibrations applied to the data include dark correction, scattered light and background correction, flat fielding, geometric distortion correction, and wavelength calibration. In addition, the IRIS team has calibrated the IRIS absolute throughput as a function of wavelength and has been tracking throughput changes over the course of the mission. As a resource for the IRIS data user, this article describes the details of these calibrations as they have evolved over the first few years of the mission. References to online documentation provide access to additional information and future updates.

Evidence for a Pulsar Wind Nebula in the Type Ib Peculiar Supernova SN 2012au

Abstract: We present an optical spectrum of the energetic Type Ib supernova (SN) 2012au obtained at an unprecedented epoch of 6.2 years after explosion. Forbidden transition emission lines of oxygen and sulfur are detected with expansion velocities of 2300 km/s. The lack of narrow H Balmer lines suggests that interaction with circumstellar material is not a dominant source of the observed late-time emission. We also present a deep Chandra observation that reveals no X-ray emission down to a luminosity of L_X < 2 x 10^{38} erg/s (0.5-10 keV). Our findings are consistent with the notion that SN 2012au is associated with a diverse subset of SNe, including long-duration gamma-ray burst SNe and superluminous SNe, harboring pulsar/magnetar wind nebulae that influence core-collapse explosion dynamics on a wide range of energy scales. We hypothesize that these systems may all evolve into a similar late-time phase dominated by forbidden oxygen transitions, and predict that emission line widths should remain constant or broaden a few per cent per year due to the acceleration of ejecta by the pulsar/magnetar bubble.

A Geometrical 1% Distance to the Short-period Binary Cepheid V1334 Cygni

Abstract: This research is based on observations made with SOPHIE spectrograph on the 1.93-m telescope at Ob- A geometrical 1 % distance to a short-period binary Cepheid 11 servatoire de Haute-Provence (CNRS/AMU), France (ProgID: 13A.PNPS10, 13B.PNPS003, 14A.PNPS010, 15A.PNPS010, 16B.PNPS.KERV). This research is based on observations made with the Mercator Telescope, operated on the island of La Palma by the Flemish Community, at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofsica de Canarias. Hermes is supported by the Fund for Scientific Research of Flanders (FWO), Belgium; the Research Council of K.U.Leuven, Belgium; the Fonds National de la Recherche Scientifique (F.R.S.- FNRS), Belgium; the Royal Observatory of Belgium; the Observatoire de Genve, Switzerland; and the Th¨uringer Landessternwarte, Tautenburg, Germany. This work is also based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555 (ProgID 13454). We acknowledge the support of the French Agence Nationale de la Recherche (ANR-15-CE31-0012-01, project UnlockCepheids). WG and GP gratefully acknowledge financial support from the BASAL Centro de Astrofisica y Tecnologias Afines (CATA, AFB-170002). WG also acknowledges financial support from the Millenium Institute of Astrophysics (MAS) of the Iniciativa Cientifica Milenio del Ministerio de Economia, Fomento y Turismo de Chile (project IC120009). We acknowledge financial support from the Programme National de Physique Stellaire (PNPS) of CNRS/INSU, France. Support from the Polish National Science Centre grants MAESTRO UMO-2017/26/A/ST9/00446 and from the IdP II 2015 0002 64 grant of the Polish Ministry of Science and Higher Education is also acknowledged. The research leading to these results has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 695099 and 639889). NRE acknowledge support from the Chandra X-ray Center NASA (contract NAS8-03060) and the HST grants GO-13454.001-A and GO-14194.002. This work is based upon observations obtained with the Georgia State University Center for High Angular Resolution Astronomy Array at Mount Wilson Observatory. The CHARA Array is supported by the National Science Foundation under Grants No. AST-1211929, 1411654, and 1636624. Institutional support has been provided from the GSU College of Arts and Sciences and the GSU Office of the Vice President for Research and Economic Development. BP acknowledges financial support from the Polish National Science Center grant SONATA 2014/15/D/ST9/02248.

The Fornax Cluster VLT Spectroscopic Survey. I - VIMOS spectroscopy of compact stellar systems in the Fornax core region

Abstract: We present the results of a wide spectroscopic survey aimed at detecting extragalactic globular clusters (GCs) in the core of the Fornax cluster. About 4500 low-resolution spectra (from 4800 to 10000 A) were observed in 25 VLT/VIMOS masks covering the central 1 deg(-2) around the dominant galaxy NGC 1399 corresponding to similar to 175 kpc galactocentric radius. We describe the methodology used for data reduction and data analysis. We found a total of 387 unique physical objects (372 GCs and 15 ultracompact dwarfs) in the field covered by our observations. Most of these objects lie in the region of NGC 1399 halo, with only 10 per cent likely belonging to other giant galaxies 48 of these objects have a literature counterpart. The new VIMOS data set is complementary to the many GC catalogues already present in the literature and it brings the total number of tracer particles around NGC 1399 to more than 1130 objects. With this comprehensive radial velocity sample, we have found that the velocity dispersion of the GC population (equally for red and blue GC populations) shows a relatively sharp increase from low velocity dispersion (similar to 250-350 km s(-1) ) to high velocity dispersion (similar to 300-4001cm s(-1) ) at projected radius of approximate to 10 arcmin (similar to 60 kpc) from the galaxy centre. This suggests that at a projected radius of approximate to 60 kpc both blue and red GC populations begin to be governed by the dominating Fornax cluster potential, rather than by the central NGC 1399 galaxy potential. This kinematic evidence corroborates similar results found using surface brightness analysis and planetary nebulae kinematics.

Gaia and the Galactic Center Origin of Hypervelocity Stars

Abstract: We use new Gaia measurements to explore the origin of the highest velocity stars in the Hypervelocity Star Survey. The measurements reveal a clear pattern in the B-type stars. Halo stars dominate the sample at speeds about 100 km/s below Galactic escape velocity. Disk runaway stars have speeds up to 100 km/s above Galactic escape velocity, but most disk runaways are bound. Stars with speeds about 100 km/s above Galactic escape velocity originate from the Galactic center. Two bound stars may also originate from the Galactic center. Future Gaia measurements will enable a large, clean sample of Galactic center ejections for measuring the massive black hole ejection rate of hypervelocity stars, and for constraining the mass distribution of the Milky Way dark matter halo.

Temperature structure in the Perseus cluster core observed with Hitomi

Abstract: The present paper explains the temperature structure of X-ray emitting plasma in the core of the Perseus cluster based on 1.8-20.0 keV data obtained with the Soft X-ray Spectrometer (SXS) on board the Hitomi Observatory. A series of four observations was carried out, with a total effective exposure time of 338 ks that covered a central region of similar to 7' in diameter. SXS was operated with an energy resolution of similar to 5 eV (full width at half maximum) at 5.9 keV. Not only fine structures of K-shell lines in He-like ions, but also transitions from higher principal quantum numbers were clearly resolved from Si through Fe. That enabled us to perform temperature diagnostics using the line ratios of Si, S, Ar, Ca, and Fe, and to provide the first direct measurement of the excitation temperature and ionization temperature in the Perseus cluster. The observed spectrum is roughly reproduced by a single-temperature thermal plasma model in collisional ionization equilibrium, but detailed line-ratio diagnostics reveal slight deviations from this approximation. In particular, the data exhibit an apparent trend of increasing ionization temperature with the atomic mass, as well as small differences between the ionization and excitation temperatures for Fe, the only element for which both temperatures could be measured. The best-fit two-temperature models suggest a combination of 3 and 5 keV gas, which is consistent with the idea that the observed small deviations from a single-temperature approximation are due to the effects of projecting the known radial temperature gradient in the cluster core along the line of sight. A comparison with the Chandra/ACIS and the XMM-Newton/RGS results, on the other hand, suggests that additional lower-temperature components are present in the intracluster medium (ICM), but not detectable with Hitomi/SXS giving its 1.8-20 keV energy band.

Chromospheric Heating due to Cancellation of Quiet Sun Internetwork Fields

Abstract: RIS is a NASA small explorer mission developed and operated by LMSAL with mission operations executed at NASA Ames Research center and major contributions to downlink communications funded by ESA and the Norwegian Space Centre. M.G. was supported by NASA grant NNX16AC34G. J.dl.C.R. is supported by grants from the Swedish Research Council (2015-03994), the Swedish National Space Board (128/15), and the Swedish Civil Contingencies Agency (MSB). This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (SUNMAG, grant agreement 759548). B.D.P. was supported by NASA grant NNX11AN98G and NASA contracts NNG09FA40C (IRIS). The work of L.B.R. and S.E.P. was supported by the Spanish Ministerio de Economia and Competitividad through grants ESP2013-47349-C6-1-R and ESP2016-77548-C5-1-R, including a percentage from European FEDER funds. Image reconstruction was performed at IAA-CSIC supercomputing facilities. The Swedish 1 m Solar Telescope is operated by the Institute for Solar Physics of Stockholm University in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. M.C. was supported by the Research Council of Norway through its Centres of Excellence scheme, project number 262622, and through grants of computing time from the Programme for Supercomputing. This research has made use of NASA's Astrophysics Data System.

The Many Definitions of a Black Hole

Abstract: Although black holes are objects of central importance across many fields of physics, there is no agreed upon definition for them, a fact that does not seem to be widely recognized. Physicists in different fields conceive of and reason about them in radically different, and often conflicting, ways. All those ways, however, seem sound in the relevant contexts. After examining and comparing many of the definitions used in practice, I consider the problems that the lack of a universally accepted definition leads to, and discuss whether one is in fact needed for progress in the physics of black holes. I conclude that, within reasonable bounds, the profusion of different definitions is in fact a virtue, making the investigation of black holes possible and fruitful in all the many different kinds of problems about them that physicists consider, although one must take care in trying to translate results between fields.

The Black Hole in the Most Massive Ultracompact Dwarf Galaxy M59-UCD3

Abstract: We examine the internal properties of the most massive ultracompact dwarf galaxy (UCD), M59-UCD3, by combining adaptive optics assisted near-IR integral field spectroscopy from Gemini/NIFS, and Hubble Space Telescope (HST) imaging. We use the multi-band HST imaging to create a mass model that suggests and accounts for the presence of multiple stellar populations and structural components. We combine these mass models with kinematics measurements from Gemini/NIFS to find a best-fit stellar mass-to-light ratio ($M/L$) and black hole (BH) mass using Jeans Anisotropic Models (JAM), axisymmetric Schwarzschild models, and triaxial Schwarzschild models. The best fit parameters in the JAM and axisymmetric Schwarzschild models have black holes between 2.5 and 5.9 million solar masses. The triaxial Schwarzschild models point toward a similar BH mass, but show a minimum $\chi^2$ at a BH mass of $\sim 0$. Models with a BH in all three techniques provide better fits to the central $V_{rms}$ profiles, and thus we estimate the BH mass to be $4.2^{+2.1}_{-1.7} \times 10^{6}$ M$_\odot$ (estimated 1$\sigma$ uncertainties). We also present deep radio imaging of M59-UCD3 and two other UCDs in Virgo with dynamical BH mass measurements, and compare these to X-ray measurements to check for consistency with the fundamental plane of BH accretion. We detect faint radio emission in M59cO, but find only upper limits for M60-UCD1 and M59-UCD3 despite X-ray detections in both these sources. The BH mass and nuclear light profile of M59-UCD3 suggests it is the tidally stripped remnant of a $\sim$10$^{9-10}$ M$_\odot$ galaxy.

NuSTAR spectral analysis of two bright Seyfert 1 galaxies: MCG +8-11-11 and NGC 6814

Abstract: We report on the NuSTAR observations of two bright Seyfert 1 galaxies, namely MCG +8-11-11 (100 ks) and NGC 6814 (150 ks) The main goal of these observations was to investigate the Comptonization mechanisms acting in the innermost regions of an active galactic nucleus (AGN) which are believed to be responsible for the UV/X-ray emission The spectroscopic analysis of the NuSTAR spectra of these two sources revealed that although they had different properties overall (black hole masses, luminosity and Eddington ratios), they had very similar coronal properties Both presented a power-law spectrum with a high-energy cut-off at ∼150–200 keV, a relativistically broadened Fe K α line and the associated disc reflection component, plus a narrow iron line likely emitted in Compton thin and distant matter The intrinsic continuum was well described by Comptonization models that show for MCG +8-11-11 a temperature of the coronal plasma of kT_e ∼ 60 keV and an extrapolated optical depth τ = 18; for NGC 6814, the coronal temperature was kT_e ∼ 45 keV with an extrapolated optical depth of τ = 25 We compare and discuss these values to some most common Comptonization models that aim at explaining the energy production and stability of coronae in AGNs