bluuebunny/crossref_metadata_2025_split huggingface dataset:
BOUNDEDNESS OF MAXIMAL FUNCTIONS ON NONDOUBLING PARABOLIC MANIFOLDS WITH ENDS
Authors: DOAN HONG CHUONG 
Published: March 2020

AbstractLet $M$ be a nondoubling parabolic manifold with ends. First, this paper investigates the boundedness of the maximal function associated with the heat semigroup ${\mathcal{M}}_{\unicode[STIX]{x1D6E5}}f(x):=\sup _{t>0}|e^{-t\unicode[STIX]{x1D6E5}}f(x)|$ where $\unicode[STIX]{x1D6E5}$ is the Laplace–Beltrami operator acting on $M$. Then, by combining the subordination formula with the previous result, we obtain the weak type $(1,1)$ and $L^{p}$ boundedness of the maximal function ${\mathcal{M}}_{\sqrt{L}}^{k}f(x):=\sup _{t>0}|(t\sqrt{L})^{k}e^{-t\sqrt{L}}f(x)|$ on $L^{p}(M)$ for $1<p\leq \infty$ where $k$ is a nonnegative integer and $L$ is a nonnegative self-adjoint operator satisfying a suitable heat kernel upper bound. An interesting thing about the results is the lack of both doubling condition of $M$ and the smoothness of the operators’ kernels.
Modeling and analysis of medium-resolution integrated-light spectra of globular clusters in dwarf galaxies
Authors: Sharina Margarita E. , Shimansky Vladislav V. 
Published: March 2020

AbstractThe study of ages, helium mass fraction (Y) and chemical composition of globular clusters in dwarf galaxies is important for understanding the physical conditions at the main evolutionary stages of the host galaxies and for constraining the build-up histories of large galaxies. We present the analysis of integrated-light spectra of 8 extragalactic and 20 Galactic globular clusters (GCs) using our population synthesis method. We calculate synthetic spectra of GCs according to the defined stellar mass functions using model atmospheres and stellar parameters ([Fe/H], Teff, and logg) set by theoretical isochrones. The main advantage of our method is the ability to determine not only chemical composition but also the age and mean Y in a cluster by modelling and analysis of Balmer absorption lines. The knowledge of Y and anomalies of light elements in star clusters is one of the key points for understanding the phenomenon of multiple stellar populations.
STRucture and Evolution of the GAlaxy (STREGA): The case of Pal 3
Authors: Moretti M. I. , Musella I. , Marconi M. , Ripepi V. , Molinaro R. 
Published: March 2020

AbstractIn the context of the STRucture and Evolution of the GAlaxy survey, we describe the preliminary results obtained for the fields around the globular cluster Pal 3 (about 2.75 square degrees), by exploiting the obtained g, r, i time series photometry. The final aim is to use variable stars as tools to verify and study the presence of streams around Pal 3. We found 20 candidate variable stars of which 7 RR Lyrae stars possibly belonging to Pal 3, also at large distance from the center. The distribution of the candidate RR Lyrae seems to confirm a preferential distribution in the north-east direction, confirming previous results in literature.
‘Status update’ for the AGB scenario for the formation of multiple populations
Authors: D’Antona Francesca 
Published: March 2020

AbstractThe Asymptotic Giant Branch (AGB) scenario for the formation of multiple populations has been quantitatively studied in the course of the last twenty years, examining the aspects both of nucleosynthesis and of the dynamics of formation of new stars in a cooling flow at the center of the first generation cluster, and of the following N–body evolution. The large complexity of these studies finds many validations in the properties of multiple populations. Here I shortly summarize recent accomplishments in the study of the evolution of massive AGBs and super–AGBs including the explanation of anomalous high lithium abundances in ‘extreme’ second generation stars in ω Cen and NGC 2808.
Investigation of the nearby open clusters with Gaia DR2 data
Authors: Seleznev Anton F. , Danilov Vladimir M. , Carraro Giovanni 
Published: March 2020

AbstractGaia DR2 catalog provides a unique possibility to study the three-dimensional structure and the three-dimensional velocity field of the nearby open clusters. We can either select stars with a maximum membership probability and the most accurate values for the proper motions, parallaxes, and the radial velocities, or study these clusters statistically using overwhelmingly large areas of sky of tens by tens degrees. The second approach allows us to reveal the extensive outer parts of the clusters - a corona and the tidal tails and to study the luminosity and mass functions of these clusters. We present the first results of the investigation of several nearby open clusters, including Pleiades, Alpha Persei, Ruprecht 147.
Structure of the open cluster Collinder 463 revealed by Gaia astrometry
Authors: Semionov Dmitrij 
Published: March 2020

AbstractIn this work we present our new estimates of the fundamental parameters of the open cluster Collinder 463, based on Gaia astrometric and PanSTARRS photometric data. In addition to updating previously available parameter values we highlight the existence of an extended stellar “halo” which is closely related to the presently known star cluster.
A new diagnostic for multiple populations: NGC 6388 as a test case
Authors: Bragaglia Angela , Carretta Eugenio 
Published: March 2020

AbstractRecently, the sample size of stars with detailed, homogeneous abundances in the massive bulge Globular cluster NGC 6388 expanded to 185 giants. We use this wealth of data to present first results on its multiple stellar populations. In particular, i) we introduce a new diagnostic plot to survey the occurrence of very high temperature for H-burning in the first-generation polluters, and ii) we pinpoint a restricted temperature range reached by polluters at work in NGC 6388.
MOCCA-SURVEY Database I: Dissolution of tidally filling star clusters harboring black hole subsystem
Authors: Giersz Mirek , Askar Abbas , Wang Long , Hypki Arkadiusz , Leveque Agostino , Spurzem Rainer 
Published: March 2020

AbstractWe investigate the dissolution process of star clusters embedded in an external tidal field and harboring a subsystem of stellar-mass black hole. For this purpose we analyzed the MOCCA models of real star clusters contained in the Mocca Survey Database I. We showed that the presence of a stellar-mass black hole subsystem in tidally filling star cluster can lead to abrupt cluster dissolution connected with the loss of cluster dynamical equilibrium. Such cluster dissolution can be regarded as a third type of cluster dissolution mechanism. We additionally argue that such a mechanism should also work for tidally under-filling clusters with a top-heavy initial mass function.
Mass loss of different stellar populations in globular clusters
Authors: Tailo Marco 
Published: March 2020

AbstractOnce the age and metallicity are fixed, the colour distribution of horizontal branch stars in a globular cluster depends on few parameters: the helium abundance of the population and the mass lost during the pre-HB stages. These parameters are usually derived from the HB itself, hence they are degenerate. Breaking this degeneracy and understanding their role is a tricky and challenging problem that no study has solved yet. Combining the information obtained from the chromosome maps and the analysis of multi-band photometry with state of the art stellar evolution models, we can obtain a solid estimate of Y for the various stellar populations in a GC. We will then have, for the first time, the possibility to break the parameters’ degeneracy on the HB, understand the role of the mass loss, and lay the foundation to build another piece of the multiple populations mosaic.
N-body chaos, phase-space transport and relaxation in numerical simulations
Authors: Di Cintio Pierfrancesco , Casetti Lapo 
Published: March 2020

AbstractUsing direct N-body simulations of self-gravitating systems we study the dependence of dynamical chaos on the system size N. We find that the N-body chaos quantified in terms of the largest Lyapunov exponent Λmax decreases with N. The values of its inverse (the so-called Lyapunov time tλ) are found to be smaller than the two-body collisional relaxation time but larger than the typical violent relaxation time, thus suggesting the existence of another collective time scale connected to many-body chaos.
The Chandrasekhar Spitzer controversy and the (ir)relevance of distant interactions
Authors: van Albada Tjeerd S. , Szomoru Arpad 
Published: March 2020

AbstractWe have done N-body simulations with N up to 106, with the aim to determine whether fluctuations in the force field of a globular cluster are caused by nearby or distant encounters. We find that distant encounters are insignificant, in agreement with Chandrasekhar’s expectations, contrary to general opinion.
Modeling Pulsars in dense star clusters
Authors: Ye Claire S. , Kremer Kyle , Chatterjee Sourav , Rodriguez Carl L. , Rasio Frederic A. 
Published: March 2020

AbstractOver a hundred millisecond radio pulsars (MSPs) have been observed in globular clusters (GCs), motivating theoretical studies of the formation and evolution of these sources through stellar evolution coupled to stellar dynamics. Here we study MSPs in GCs using realistic N-body simulations with our Cluster Monte Carlo code. We show that neutron stars (NSs) formed in electron-capture supernovae can be spun up through mass transfer to form MSPs. Both NS formation and spin-up through accretion are greatly enhanced through dynamical interaction processes. We find that our models for average GCs at the present day with masses ≍ 2 × 105M⊙ can produce up to 10 – 20 MSPs, while a very massive GC model with mass ≍ 106M⊙ can produce close to 100. We show that the number of MSPs is anti-correlated with the total number of stellar-mass black holes (BHs) retained in the host cluster. As a result, the number of MSPs in a GC could be used to place constraints on its BH population. Some intrinsic properties of MSP systems in our models (such as the magnetic fields and spin periods) are in good overall agreement with observations.
Chemical abundances of four red supergiants star clusters (RSGCs) in Scutum-Crux arm
Authors: Chun Sang-Hyun 
Published: March 2020

AbstractWe investigate the spectral properties of red supergiant stars in the four RSGCs (RSGC2, RSGC3, RSGC4, RSGC5, and Alicante 10) in the Scutum-Crux arm of the Milky Way. The high-resolution (R: 45,000) near-infrared (H and K bands) spectra for 41 red supergiants were obtained using IGRINS at Gemini South telescope. The calibration of effective temperatures and gravities are derived based on the EWTi and EWCO using supergiants in IGIRNS library. The resulted temperatures and gravities are consistent with previous results. Model spectra were synthesized using derived stellar parameters from which we estimate metallicities and chemical abundances like α-elements. In our preliminary result, we find that overall four RSGCs indeed have sub-solar metallicities as already known in previous studies. The metallicity properties of RSGCs are far off the nominal metallicity trend in this region, and this suggests recent low-metallicity gas fueling into the inner disk and bulge.
The evolution of intracluster medium in stellar clusters
Authors: Chantereau W. 
Published: March 2020

AbstractStars in globular clusters lose mass through slow stellar winds that are retained by the stellar cluster and should contribute to build up a non-negligible intracluster medium over time. However, all the observations so far found only a negligible amount of gas in GCs. We propose here to test different mechanisms such as ram-pressure stripping by the motion of the GC in the Galactic halo medium and the inclusion of ionising sources to explain the lack of gas in GCs. We use full 3D hydrodynamical simulations taking into account stellar winds, ionising radiation, radiative heating and radiative pressure. We find that the combined effect of ram-pressure and ionisation are able to explain the negligible amount of gas observed in the core of intermediate-mass and massive GCs.
Possible connection between P Cygni and neighboring open clusters
Authors: Beradze Sopia , Kochiashvili Nino 
Published: March 2020

AbstractAccording to earlier investigations by Turner and co-authors, P Cygni could be a member of a hypothetical, sparsely populated open cluster. The star lies near the east boundary of this hypothetical cluster. There is another known open cluster, IC 4996, in the vicinity of P Cygni. The same authors believe that the above mentioned two clusters are connected to each other and they could represent a double cluster. As P Cygni is a hypergiant and consequently has very strong and variable stellar wind, so a cluster membership can enable us to determine the age, distance, and reddening of the star relatively precisely. We used new data of different catalogues, for example, PPMXL and Gaia and tried to resolve the problem.
SOWAT: High-resolution imaging with only partial AO correction
Authors: Bosco Felix , Pott Jörg-Uwe , Schödel Rainer 
Published: March 2020

AbstractObservations of dense stellar systems such as globular clusters (GCs) are limited in resolution by the optical aberrations induced by atmospheric turbulence (atmospheric seeing). At the example of holographic speckle imaging, we now study, to which degree image reconstruction algorithms are able to remove residual aberrations from a partial adaptive optics (AO) correction, such as delivered from ground-layer AO (GLAO) systems. Simultaneously, we study, how such algorithms benefit from being applied to pre-corrected instead of natural point-spread functions (PSFs). We find that using partial AO corrections already lowers the demands on the holography reference star by ∼3 mag, what makes more fields accessible for this technique, and also that the discrete integration times may be chosen about 2–3× longer, since the effective wavefront evolution is slowed down by removing the perturbation power.
Merging black holes of any size and hierarchy
Authors: Fragione Giacomo 
Published: March 2020

AbstractWith the hundreds of merging binary black holes (BHs) expected to be detected by LIGO, LISA, and other upcoming instruments, the modelling of astrophysical channels that lead to the formation of compact BH binaries has become of crucial importance. BHs of any size can form bound systems in every astrophysical environment, from the field to galactic nuclei. If a binary is too wide, it needs a catalysis process to harden and merge, as in the case a third objects orbiting the BH binary on a distant orbit. In this case, Kozai-Lidov cycles can pump up the binary eccentricity, thus driving it to a merger thanks to efficient energy dissipation at the pericenter. Some remarkable scenarios where the Kozai-Lidov mechanism operates are in triple and quadruple systems of stellar BHs, and in intermediate-mass BH-stellar BH binaries in orbit around a central supermassive BH in galactic nuclei.
Globular cluster system of NGC 3613, a massive elliptical galaxy in a poor environment
Authors: De Bórtoli Bruno J. , Bassino Lilia P. , Caso Juan P. , Ennis Ana I. 
Published: March 2020

AbstractWe present an analysis of the globular cluster system (GCS) of the galaxy NGC 3613, an intrinsically bright elliptical galaxy (MV = −21.5) in a low density environment (it is the central galaxy of a group of a dozen galaxies). Based on Gemini/GMOS photometry of NGC 3613 we obtained the following properties for this GCS. A ‘blue tilt’ is detected in the colour-magnitude diagram. The colour distribution is bimodal, presenting the two classical globular cluster (GC) sub-populations. The spatial and azimuthal projected distributions show that red sub-population correlates with the stellar component of the host galaxy.
UVIT observations of UV-Bright stars in four Galactic Globular Clusters
Authors: Kumar Ranjan , Pradhan Ananta C. , Parthasarathy M. , Ojha Devendra K. , Mohapatra Abhisek , Murthy Jayant 
Published: March 2020

AbstractWe have performed photometric analysis of four Galactic globular clusters (GGCs): NGC 4147, NGC 4590, NGC 5053 and NGC 7492 using far-UV and near-UV filters of the Ultraviolet Imaging Telescope (UVIT) on-board AstroSat. With the help of color-magnitude diagrams (CMDs), we have identified ~150 blue horizontal branch stars (BHBs), and ~40 blue straggler stars (BSS) in the four GGCs. We study the temperature and radial distribution of BHBs and BSS for the four GGCs.
The collision between the Milky Way and Andromeda and the fate of their Supermassive Black Holes
Authors: Schiavi Riccardo , Capuzzo-Dolcetta Roberto , Arca Sedda Manuel , Spera Mario 
Published: March 2020

AbstractOur Galaxy and the nearby Andromeda Galaxy (M31) form a bound system, even though the relative velocity vector of M31 is currently not well constrained. Their orbital motion is highly dependent on the initial conditions, but all the reliable scenarios imply a first close approach in the next 3–5 Gyrs. In our study, we simulate this interaction via direct N-body integration, using the HiGPUs code. Our aim is to investigate the dependence of the time of the merger on the physical and dynamical properties of the system. Finally, we study the dynamical evolution of the two Supermassive Black Holes placed in the two galactic centers, with the future aim to achieve a proper resolution to follow their motion until they form a tight binary system.
Kinematics of multiple stellar populations in Globular Clusters with Gaia
Authors: Cordoni G. , Milone A. P. , Mastrobuono-Battisti A. , Marino A. F. , Lagioia E. P. , Tailo M. 
Published: March 2020

AbstractThe internal dynamics of multiple stellar populations in Globular Clusters (GCs) provides unique constraints on the physical processes responsible for their formation. Specifically, the present-day kinematics of cluster stars, such as rotation and velocity dispersion, seems to be related to the initial configuration of the system. In recent work (Milone et al. 2018), we analyzed for the first time the kinematics of the different stellar populations in NGC 0104 (47 Tucanae) over a large field of view, exploiting the Gaia Data Release 2 proper motions combined with multi-band ground-based photometry. In this paper, based on the work by Cordoni et al. (2019), we extend this analysis to six GCs, namely NGC 0288, NGC 5904 (M 5), NGC 6121 (M 4), NGC 6752, NGC 6838 (M 71) and further explore NGC 0104. Among the analyzed clusters only NGC 0104 and NGC 5904 show significant rotation on the plane of the sky. Interestingly, multiple stellar populations in NGC 5904 exhibit different rotation curves.
Helium variations in Galactic and extragalactic Globular Clusters
Authors: Lagioia Edoardo P. , Milone Antonino P. , Marino Anna F. , Dotter Aaron , Cordoni Giacomo , Tailo Marco 
Published: March 2020

AbstractThe recent measurements of internal variations of helium in Galactic and extragalactic Globular Clusters (GCs) set binding constraints to the models of formation of Multiple Populations (MPs) in GCs, and gave rise, at the same time, to crucial questions related with the influence of the environment on MP formation as well as with the role played by GCs in the early galactic formation. We present the most recent estimates of helium enrichment in the main populations of a large sample of Galactic and extragalactic GCs.
Gravity, Topography, and Melt Generation Rates From Simple 3‐D Models of Mantle Convection
Authors: Lees Matthew E. , Rudge John F. , McKenzie Dan 
Published: March 2020

AbstractConvection in fluid layers at high Rayleigh number (Ra ∼106) have a spoke pattern planform. Instabilities in the bottom thermal boundary layer develop into hot rising sheets of fluid, with a component of radial flow toward a central upwelling plume. The sheets form the “spokes” of the pattern, and the plumes the “hubs.” Such a pattern of flow is expected to occur beneath plate interiors on Earth, but it remains a challenge to use observations to place constraints on the convective planform of the mantle. Here we present predictions of key surface observables (gravity, topography, and rates of melt generation) from simple 3‐D numerical models of convection in a fluid layer. These models demonstrate that gravity and topography have only limited sensitivity to the spokes and mostly reflect the hubs (the rising and sinking plumes). By contrast, patterns of melt generation are more sensitive to short‐wavelength features in the flow. There is the potential to have melt generation along the spokes but at a rate which is relatively small compared with that at the hubs. Such melting of spokes can only occur when the lithosphere is sufficiently thin (
km) and mantle water contents are sufficiently high (
ppm). The distribution of volcanism across the Middle East, Arabia, and Africa north of the equator suggests that it results from such spoke pattern convection.
Climate Models and Remote Sensing Retrievals Neglect Substantial Desert Dust Asphericity
Authors: Huang Yue , Kok Jasper F. , Kandler Konrad , Lindqvist Hannakaisa , Nousiainen Timo , Sakai Tetsu , Adebiyi Adeyemi , Jokinen Olli 
Published: March 2020

AbstractClimate models and remote sensing retrievals generally assume that dust aerosols are spherical or spheroidal. However, measurements show that dust aerosols deviate substantially from spherical and spheroidal shapes, as ratios of particle length to width (the aspect ratio) and height to width (height‐to‐width ratio) deviate substantially from unity. Here, we quantify dust asphericity by compiling dozens of measurements of aspect ratio and height‐to‐width ratio across the globe. We find that the length is on average 5 times larger than the height and that climate models and remote sensing retrievals underestimate this asphericity by a factor of ~3–5. Compiled measurements further suggest that North African dust becomes more aspherical during transport, whereas Asian dust might become less aspherical. We obtain globally‐averaged shape distributions, from which we find that accounting for dust asphericity increases gravitational settling lifetime by ~20%. This increased lifetime helps explain the underestimation of coarse dust transport by models.
Two‐Ray Reflection Resolution Algorithm for Planar Material Electromagnetic Property Measurement at the Millimeter‐Wave Bands
Authors: Zhang Jiliang , Liao Xi , Alayón Glazunov Andrés , Shao Yu , Wang Yang , Chu Xiaoli , Zhang Jie 
Published: March 2020

AbstractElectromagnetic (EM) reflection properties of building materials and structures have been investigated through practical measurements. However, the finite thickness of measured materials makes it challenging to resolve the rays reflected from the front and the back surfaces. In this paper, we therefore present a three‐step minimum least squares‐based algorithm to resolve two closely adjacent rays reflected from the front and the back surfaces of a board‐shaped material. Our analytical and numerical results show that the proposed algorithm achieves the Cramér‐Rao lower bound. The proposed algorithm is validated using measurement data for various materials and incident angles in the 40–50 GHz frequency band. The validation results show that the proposed algorithm is capable of resolving two closely adjacent rays with a root‐mean‐square deviation that is smaller than 0.08. Main applications of the proposed algorithm can be found in the frequency domain measurements of the EM wave reflections by typical building structures, e.g., window glass, doors, ceiling, and floors.