bluuebunny/crossref_metadata_2025_split huggingface dataset:
Integrated spectroscopy of extragalactic Globular Clusters
Authors: Sakari Charli M. 
Published: March 2020

AbstractIntegrated light (IL) spectroscopy enables studies of stellar populations beyond the Milky Way and its nearest satellites. In this paper, I will review how IL spectroscopy reveals essential information about globular clusters and the assembly histories of their host galaxies, concentrating particularly on the metallicities and detailed chemical abundances of the GCs in M31. I will also briefly mention the effects of multiple populations on IL spectra, and how observations of distant globular clusters help constrain the source(s) of light-element abundance variations. I will end with future perspectives, emphasizing how IL spectroscopy can bridge the gap between Galactic and extragalactic astronomy.
Chemical composition of globular clusters in dwarf galaxies
Authors: Larsen Søren S. 
Published: March 2020

AbstractThis contribution gives an update on on-going efforts to characterise the detailed chemical abundances of Local Group globular clusters (GCs) from integrated-light spectroscopy. Observations of a sample of 20 GCs so far, located primarily within dwarf galaxies, show that at low metallicities the [α/Fe] ratios are generally indistinguishable from those in Milky Way GCs. However, the “knee” above which [α/Fe] decreases towards Solar-scaled values occurs at lower metallicities in the dwarfs, implying that GCs follow the same trends seen in field stars. Efforts are underway to establish NLTE corrections for integrated-light abundance measurements, and preliminary results for Mn are discussed.
Galactic Globular Clusters: A new catalog of masses, structural parameters, velocity dispersion profiles, proper motions and space orbits
Authors: Hilker Michael , Baumgardt Holger , Sollima Antonio , Bellini Andrea 
Published: March 2020

AbstractWe collected radial velocities of more than 50.000 individual stars in 156 Galactic globular clusters (GGC) and matched them with HST photometry and Gaia DR2 proper motions. This allowed us to derive the GGC’s mean proper motions and space velocities. By fitting a large set of N-body simulations to their velocity dispersion and surface density profiles, combined with new measurements of their internal radially dependent mass functions, we have determined their present-day masses and structural parameters, and for 144 GGCs their internal kinematics. We also derive the initial cluster masses by calculating the cluster orbits backwards in time applying suitable recipes to account for mass-loss and dynamical friction. The new fundamental parameters of GGCs are publicly available via an online database, which will regularly be updated.
The VISCACHA survey – deep and resolved photometry of star clusters in the Magellanic Clouds
Authors: Dias Bruno , Maia Francisco , Kerber Leandro , dos Santos João F. C. , Bica Eduardo , Armond Tina , Barbuy Beatriz , Fraga Luciano , Hernandez-Jimenez Jose A. , Katime Santrich Orlando J. , Oliveira Raphael A. P. , Pérez-Villegas Angeles , Piatti Andrés E. , Quint Bruno , Sanmartin David , Angelo Mateus S. , Souza Stefano O. , Vieira Rodrigo G. , Westera Pieter , Parisi Celeste , Geisler Doug , Minniti Dante , Saito Roberto , Bassino Lilia P. , De Bórtoli Bruno J. , Figueiredo André , Rímulo Leandro 
Published: March 2020

AbstractThe VISCACHA (VIsible Soar photometry of star Clusters in tApii and Coxi HuguA†) Survey is an ongoing project based on deep and spatially resolved photometric observations of Magellanic Cloud star clusters, collected using the SOuthern Astrophysical Research (SOAR) telescope together with the SOAR Adaptive Module Imager. So far we have used >300h of telescope time to observe ∼150 star clusters, mostly with low mass (M < 104M⊙) on the outskirts of the LMC and SMC. With this high-quality data set, we homogeneously determine physical properties using deep colour-magnitude diagrams (ages, metallicities, reddening, distances, mass, luminosity and mass functions) and structural parameters (radial density profiles, sizes) for these clusters which are used as a proxy to investigate the interplay between the Magellanic Clouds and their evolution. We present the VISCACHA survey and its initial results, based on our first two papers. The project’s long term goals and expected legacy to the community are also addressed.
Searching Gaia for extended structure in Globular Clusters
Authors: Kuzma Pete B. , Ferguson Annette M. N. , Peñarrubia Jorge 
Published: March 2020

AbstractA growing number of studies are revealing that many Milky Way globular clusters possess extended stellar structures beyond their traditional boundaries. Just how ubiquitous these structures are, and how they originate, are key questions to explore. In this contribution, we present a Bayesian technique that we have developed to separate probable members of globular clusters from the dominant Milky Way fore/background at large clustercentric radii and hence facilitate quantitative analyses of these intriguing structures. We demonstrate the promise of our method by showing how it recovers the known extended features around Palomar 5 and NGC 7089.
Imprints of evolution on the internal kinematics of Globular Clusters
Authors: Watkins Laura L. , van der Marel Roeland P. , Bellini Andrea , Libralato Mattia , Anderson Jay 
Published: March 2020

AbstractGlobular clusters are collisional systems, meaning that the stars inside them interact on timescales much shorter than the age of the Universe. These frequent interactions transfer energy between stars and set up observable trends that tell the story of a cluster’s evolution. This contribution focuses on what we can learn by studying velocity anisotropy and energy equipartition in globular clusters with Hubble Space Telescope proper motions.
The connection between stellar and nuclear clusters: Can an IMBH be sitting at the heart of the Milky Way?
Authors: Arca Sedda Manuel 
Published: March 2020

AbstractA vast number of observed galactic nuclei are known to harbour a central supermassive black hole (SMBH). In their early lifetime, these systems might have witnessed the strong interaction between the SMBH and massive star clusters formed in the inner galactic regions. Due to the strong tidal field exerted from the SMBH, clusters are likely to undergo tidal disruption, releasing their stars all around the SMBH, and possibly driving the formation of a nuclear cluster (NC). This mechanism can contribute to populate galactic nuclei with intermediate-mass black holes (IMBH). Interactions with the central SMBH can lead to the formation of tight massive BH binaries (MBBH) that undergo coalescence via gravitational waves (GW) emission. We discuss this mechanism in the context of the Milky Way centre, exploring the possibility that SgrA*, the Galactic SMBH, has an IMBH companion.
Globular clusters and their link with stellar populations in the Milky Way
Authors: Yong David 
Published: March 2020

AbstractObservations of stellar chemical compositions enable us to identify connections between globular clusters and stellar populations in the Milky Way. In particular, chemical abundance ratios provide detailed insight into the chemical enrichment histories of star clusters and the field populations. For some elements, there are striking differences between field and cluster stars which reflect different nucleosynthetic processes and/or chemical evolution. The goal of this talk was to provide an overview of similarities and differences in chemical compositions between globular clusters and the Milky Way as well as highlighting a few areas for further examination.
A unified construction of stellar evolution and chemical evolution models for the multiple populations in globular clusters
Authors: Jang Sohee , Kim Jenny J. , Lee Young-Wook 
Published: March 2020

AbstractRecent investigations of multiple stellar populations in globular clusters (GCs) suggest that the horizontal-branch (HB) morphology and mean period of type ab RR Lyrae variables are mostly sensitive to helium abundance, while the star formation timescale has the greatest effect on our chemical evolution model constructed to reproduce the Na-O anti-correlation of GCs. Therefore, by combining the results from synthetic HB model with those from chemical evolution model, we could put better constraints on star formation history and chemical evolution in GCs with multiple populations. From such efforts made for four GCs, M4, M5, M15, and M80, we find that consistent results can be obtained from these two independent models.
GEP I: A globular cluster in the center of the dwarf spheroidal galaxy Andromeda XXV?
Authors: Cusano Felice , Garofalo Alessia , Clementini Gisella 
Published: March 2020

AbstractLooking for variable stars in the M31 dwarf spheroidal satellite Andromeda XXV (And XXV), which we have observed with the LBC at the LBT, we serendipitously discovered a clustering of stars (Gep I) of 12 arcsec in diameter, near the center of And XXV. This is one of the very few clusters known to be associated with a dwarf spheroidal galaxy. The half light radius (rh) of Gep I at the distance of And XXV corresponds to 25 pc in linear extension. Radius and absolute V (MV∼ −4.9 mag) magnitude place Gep I in the region of the MV-rh plane that seems to be forbidden to ordinary globular clusters (GCs). The seeing-limited resolution of our photometry could resolve only a few bright stars in Gep I. The CMD of these sources is compatible with an old stellar population placed at a heliocentric distance of ∼750–800 kpc, thus confirming a real concentration of old stars. The ground-based CMD of Gep I is severely incomplete. Future high resolution imaging and spectroscopy of the brightest stars will permit to disentangle the puzzle on the real nature of Gep I.
Globular cluster tidal interactions and mergers in the Galactic disc
Authors: Mastrobuono-Battisti Alessandra , Khoperskov Sergey , Di Matteo Paola , Haywood Misha 
Published: March 2020

AbstractThe Galactic globular cluster system went and is still going through dynamical processes that require to be explored in detail. Here we illustrate how primordial massive globular clusters born in the Milky Way’s disc evolved by stripping material from each other or even merging very early during their lives. These processes might explain the puzzling presence of star-by-star spreads in iron content observed in massive globular clusters and should be taken into account when studying globular cluster stellar populations. In this context, we show how the direct comparison between the predictions provided by our direct N-body simulations and observations can shed light on the origin and chemo-dynamical evolution of globular clusters.
The building blocks of the Milky Way halo using APOGEE and Gaia or Is the Galaxy a typical galaxy?
Authors: Schiavon Ricardo P. , Mackereth J. Ted , Pfeffer Joel , Crain Rob A. , Bovy Jo 
Published: March 2020

AbstractWe summarise recent results from analysis of APOGEE/Gaia data for stellar populations in the Galactic halo, disk, and bulge, leading to constraints on the contribution of dwarf galaxies and globular clusters to the stellar content of the Milky Way halo. Intepretation of the extant data in light of cosmological numerical simulations suggests that the Milky Way has been subject to an unusually intense accretion history at z ≳ 1.5.
Kinematical evolution of Globular Clusters
Authors: Tiongco Maria A. , Vesperini Enrico , Varri Anna Lisa 
Published: March 2020

AbstractWe present several results of the study of the evolution of globular clusters’ internal kinematics, as driven by two-body relaxation and the interplay between internal angular momentum and the external Galactic tidal field. Via a large suite of N-body simulations, we explored the three-dimensional velocity space of tidally perturbed clusters, by characterizing their degree of velocity dispersion anisotropy and their rotational properties. These studies have shown that a cluster’s kinematical properties contain distinct imprints of the cluster’s initial structural properties, dynamical history, and tidal environment. Building on this fundamental understanding, we then studied the dynamics of multiple stellar populations in globular clusters, with attention to the largely unexplored role of angular momentum.
Perspectives on the Future of Land Surface Models and the Challenges of Representing Complex Terrestrial Systems
Authors: Fisher Rosie A. , Koven Charles D. 
Published: March 2020

AbstractLand surface models (LSMs) are a vital tool for understanding, projecting, and predicting the dynamics of the land surface and its role within the Earth system, under global change. Driven by the need to address a set of key questions, LSMs have grown in complexity from simplified representations of land surface biophysics to encompass a broad set of interrelated processes spanning the disciplines of biophysics, biogeochemistry, hydrology, ecosystem ecology, community ecology, human management, and societal impacts. This vast scope and complexity, while warranted by the problems LSMs are designed to solve, has led to enormous challenges in understanding and attributing differences between LSM predictions. Meanwhile, the wide range of spatial scales that govern land surface heterogeneity, and the broad spectrum of timescales in land surface dynamics, create challenges in tractably representing processes in LSMs. We identify three “grand challenges” in the development and use of LSMs, based around these issues: managing process complexity, representing land surface heterogeneity, and understanding parametric dynamics across the broad set of problems asked of LSMs in a changing world. In this review, we discuss progress that has been made, as well as promising directions forward, for each of these challenges.
Simulated Trends in Ionosphere‐Thermosphere Climate Due to Predicted Main Magnetic Field Changes From 2015 to 2065
Authors: Cnossen I. , Maute A. 
Published: March 2020

AbstractThe strength and structure of the Earth's magnetic field is gradually changing. During the next 50 years the dipole moment is predicted to decrease by
3.5%, with the South Atlantic Anomaly expanding, deepening, and continuing to move westward, while the magnetic dip poles move northwestward. We used simulations with the Thermosphere‐Ionosphere‐Electrodynamics General Circulation Model to study how predicted changes in the magnetic field will affect the climate of the thermosphere‐ionosphere system from 2015 to 2065. The global mean neutral density in the thermosphere is expected to increase slightly, by up to 1% on average or up to 2% during geomagnetically disturbed conditions (
). This is due to an increase in Joule heating power, mainly in the Southern Hemisphere. Global mean changes in total electron content (TEC) range from
3% to +4%, depending on season and UT. However, regional changes can be much larger, up to about
35% in the region of
45°S to 45°N and 110°W to 0°W during daytime. Changes in the vertical
drift are the most important driver of changes in TEC, although other plasma transport processes also play a role. A reduction in the low‐latitude upward
drift weakens the equatorial ionization anomaly in the longitude sector of
105–60°W, manifesting itself as a local increase in electron density over Jicamarca (12.0°S, 76.9°W). The predicted increase in neutral density associated with main magnetic field changes is very small compared to observed trends and other trend drivers, but the predicted changes in TEC could make a significant contribution to observationally detectable trends.
Observations of Turbulence at a Near‐Surface Temperature Front in the Arctic Ocean
Authors: Koenig Zoé , Fer Ilker , Kolås Eivind , Fossum Trygve O. , Norgren Petter , Ludvigsen Martin 
Published: March 2020

AbstractHigh‐resolution ocean temperature, salinity, current, and turbulence data were collected at an Arctic thermohaline front in the Nansen Basin. The front was close to the sea ice edge and separated the cold and fresh surface melt water from the warm and saline mixed layer. Measurements were made on 18 September 2018, in the upper 100 m, from a research vessel and an autonomous underwater vehicle. Destabilizing surface buoyancy fluxes from a combination of heat loss to the atmosphere and cross‐front Ekman transport by down‐front winds reduced the potential vorticity in the upper ocean. Turbulence structure in the mixed layer was generally consistent with turbulence production through convection by heat loss to atmosphere and mechanical forcing by moderate winds. Conditions at the front were favorable for forced symmetric instability, a mechanism drawing energy from the frontal geostrophic current. A clear signature of increased dissipation from symmetric instability could not be identified; however, this instability could potentially account for the increased dissipation rates at the front location down to 40 m depth that could not be explained by the atmospheric forcing. This turbulence was associated with turbulent heat fluxes of up to 10 W m−2, eroding the warm and cold intrusions observed between 30 and 60 m depth. A Seaglider sampled across a similar frontal structure in the same region 10 days after our survey. The submesoscale‐to‐turbulence‐scale transitions and resulting mixing can be widespread and important in the Atlantic sector of the Arctic Ocean.
Infrasound and Gravity Waves Over the Andes Observed by a Pressure Sensor on Board a Stratospheric Balloon
Authors: Poler Guerman , Garcia Raphaël F. , Bowman Daniel C. , Martire Léo 
Published: March 2020

AbstractThe study of infrasound (acoustic) and gravity waves sources and propagation in the atmosphere of a planet gives us precious insight on atmosphere dynamics, climate, and even internal structure. The implementation of modern pressure sensors with high rate sampling on stratospheric balloons is improving their study. We analyzed the data from the National Aeronautics and Space Administration Ultra Long Duration Balloon mission (16 May to 30 June 2016). Here, we focus on the balloon's transit of the Andes Mountains. We detected gravity waves that are associated to troposphere convective activity and mountain waves. An increase of the horizontal wavelengths from 50 to 70 km with increasing distance to the mountains is favoring the presence of mountain waves. We also report on the detection of infrasounds generated by the mountains in the 0.01–0.1 Hz range with a pressure amplitude increase by a factor 2 relative background signal. Besides, we characterized the decrease of microbaroms power when the balloon was flying away from the ocean coast. These observations suggest, in a way similar to microseisms for seismometers, that microbaroms are the main background noise sources recorded in the stratosphere even far from the ocean sources. Finally, we observed a broadband signal above the Andes, between 0.45 and 2 Hz, probably associated with a thunderstorm. The diversity of geophysical phenomena captured in less than a day of observation stresses the interest of high rate pressure sensors on board long‐duration balloon missions.
Arctic Sea Ice Loss as a Potential Trigger for Central Pacific El Niño Events
Authors: Kim Hyerim , Yeh Sang‐Wook , An Soon‐Il , Park Jae‐Heung , Kim Baek‐Min , Baek Eun‐Hyuk 
Published: March 2020

AbstractLittle attention has been paid to the influence of Arctic sea ice loss on climate variability in the tropical Pacific. By analyzing observational data sets, we hypothesized that anomalous Arctic sea ice concentration variations have the potential to influence tropical Pacific sea surface temperature (SST) variability via atmosphere‐ocean coupled processes in the eastern subtropical North Pacific. To test this hypothesis, we conducted idealized model experiments with 15 ensembles in which historical SSTs for 1951–2016 were restored in the Arctic only with different initial conditions. We found that a positive phase of North Pacific Oscillation‐like atmospheric circulation, which is modulated by a sea ice reduction in the Pacific Arctic sector, triggers El Niño‐like warming in the central tropical Pacific. This implies that connections between the Arctic and the tropics should be considered for further understanding of changes in El Niño and other tropical Pacific climate variability in a changing climate.
Programming effects of maternal stress on the circadian system of adult offspring
Authors: Yun Seongsik , Lee Eun Jeong , Choe Han Kyoung , Son Gi Hoon , Kim Kyungjin , Chung Sooyoung 
Published: March 2020

AbstractMaternal stress has long-lasting influences on the brain functions of offspring, and several brain regions have been proposed to mediate such programming. Although perinatal programming of crosstalk between the circadian and stress systems has been proposed, the functional consequences of prenatal stress on the circadian system and the underlying mechanisms remain largely unknown. Therefore, we investigated whether exposing pregnant mice to chronic restraint stress had prolonged effects on the suprachiasmatic nucleus (SCN), which bears the central pacemaker for mammalian circadian rhythms, of offspring. SCN explants from maternally stressed mice exhibited altered cyclic expression patterns of a luciferase reporter under control of the mouse Per1 promoter (mPer1::LUC), which manifested as a decreased amplitude and impaired stability of the rhythm. Bioluminescence imaging at the single-cell level subsequently revealed that impaired synchrony among individual cells was responsible for the impaired rhythmicity. These intrinsic defects appeared to persist during adulthood. Adult male offspring from stressed mothers showed advanced-phase behavioral rhythms with impaired stability as well as altered clock gene expression in the SCN. In addition to affecting the central rhythm, maternal stress also had prolonged influences on the circadian characteristics of the adrenal gland and liver, as determined by circulating corticosterone levels and hepatic glycogen content, and on canonical clock gene mRNA expression in those tissues. Taken together, our findings suggest that the SCN is a key target of the programming effects of maternal stress. The widespread effects of circadian disruptions caused by a misprogrammed clock may have further impacts on metabolic and mental health in later life.