bluuebunny/crossref_metadata_2025_split huggingface dataset:
Angular Momentum Evolution of Galaxies: the Perspective of Hydrodynamical Simulations
Authors: Lagos Claudia del P. 
Published: March 2020

AbstractUntil a decade ago, galaxy formation simulations were unable to simultaneously reproduce the observed angular momentum (AM) of galaxy disks and bulges. Improvements in the interstellar medium and stellar feedback modelling, together with advances in computational capabilities, have allowed the current generation of cosmological galaxy formation simulations to reproduce the diversity of AM and morphology that is observed in local galaxies. In this review I discuss where we currently stand in this area from the perspective of hydrodynamical simulations, specifically how galaxies gain their AM, and the effect galaxy mergers and gas accretion have on this process. I discuss results which suggest that a revision of the classical theory of disk formation is needed, and by discussing what the current challenges are.
Metallicity gradients in nearby star forming galaxies
Authors: Belfiore Francesco 
Published: March 2020

AbstractI study the gas phase metallicity (O/H) radial profiles in a representative sample of 550 nearby star forming galaxies with resolved spectroscopic data from the SDSS-IV MaNGA survey. Using strong-line ratio diagnostics (R23 and O3N2) and referencing to the effective (half-light) radius (Re), I find that the metallicity gradient steepens with stellar mass going from log(M/Mȯ) = 9.0 to log(M/Mȯ) = 10.5. At higher masses a flattening of the metallicity radial profile is observed in the central regions (R < 1Re). These findings are in agreement with recent independent analysis of other large samples of nearby galaxies.
Dust-to-gas ratio and metallicity gradients in DustPedia galaxies
Authors: Bianchi Simone ,   the DustPedia consortium
Published: March 2020

AbstractFar-infrared photometric observations from the Herschel Space Observatory offer the opportunity to study the dust-to-gas ratio at a resolved scale in nearby galaxies. The amount, and gradient, of solid-phase metals can thus be compared with metallicity measurements in the gas phase. We describe our preliminary work on the topic with data from the DustPedia project.
Galactic archaeology: Understanding the metallicity gradients with chemo-dynamical models
Authors: Minchev I. , Anders F. , Chiappini C. 
Published: March 2020

AbstractRadial metallicity gradients measured today in the interstellar medium (ISM) and stellar components of disk galaxies are the result of chemo-dynamical evolution since the beginning of disk formation. This makes it difficult to infer the disk past without knowledge of the ISM metallicity gradient evolution with cosmic time. We show that abundance gradients are meaningful only if stellar age information is available. The observed gradient inversion with distance from the disk mid-plane seen in the Milky Way can be explained as the effect of inside-out disk formation and disk flaring of mono-age populations. A novel recent method is presented for constraining the evolution of the Galactic ISM metallicity with radius and time directly from the observations, while at the same time recovering the birth radii of any stellar sample with precise metallicity and age measurements.
The evolution of the oxygen radial gradients in spiral galaxies
Authors: Mollá M. , Cavichia O. , Gibson B. , Tissera P. , Sánchez-Blázquez P. , Díaz A. I. , Ascasibar Y. , Few C. G. , Sánchez S. F. , Maciel W. J. 
Published: March 2020

AbstractWe analyse the evolution with redshift of the radial gradient of oxygen abundances in spiral disks resulting from our MULCHEM chemical evolution models, computed for galaxies of different sizes or masses, studying the relationships between the gradients and galaxy characteristics as the stellar mass, the size, the gas fraction or the star formation rate for z < 4.
Resolving gas-phase metallicity gradients of 0.1 ≲ z ≲ 0.8 galaxies
Authors: Carton David 
Published: March 2020

AbstractWe present gas-phase metallicity gradients of 84 star-forming galaxies between 0.08 < z
< 0.84. Using the galaxies with reliably determined metallicity gradients, we measure the median metallicity gradient to be negative (

$\[ - 0.039_{ - 0.009}^{ + 0.007}{\kern 1pt} dex/kpc\]$

). Underlying this, however, is significant scatter: (8 ± 3)% [7] of galaxies have significantly positive metallicity gradients, (38 ± 5)% [32] have significantly negative gradients, (31 ± 5)% [26] have gradients consistent with being flat. (The remaining (23 ± 5)% [19] have unreliable gradient estimates.)
The dust/gas/metallicity scaling relations in the Local Universe
Authors: Casasola V. , Bianchi S. , De Vis P. , Magrini L. , Corbelli E. ,   DustPedia collaboration
Published: March 2020

AbstractWe have combined data of the DustPedia project with observations of gas components of the interstellar medium (ISM) and metallicity abundances for late-type DustPedia galaxies to definitively characterize the ISM scaling relations in the Local Universe. In particular, we have focused on the comparison of the dust-to-gas mass ratio with gas phase metallicities.
New Insights in Extragalactic Magnetic Fields
Authors: Feretti Luigina , Govoni Federica , Heald George , Rudnick Lawrence , Johnston-Hollitt Melanie 
Published: March 2020

AbstractIn this contribution we introduce the motivation and goals of IAU Focus Meeting 8, “New Insights in Extragalactic Magnetic Fields”. We provide a background for the nine contributions included in these proceedings, as well as the online contributions. A recap of the meeting is provided in the form of audience feedback that was collected during the wrap-up session at the conclusion of FM8.
Origins of Cosmic magnetism
Authors: Subramanian Kandaswamy 
Published: March 2020

AbstractThe standard picture for the origin of magnetic fields in astrophysical systems involves turbulent dynamo amplification of a weak seed field. Dynamos convert kinetic energy of motions to magnetic energy. While it is relatively easy for magnetic energy to grow, explaining the observed degree of coherence of cosmic magnetic fields generated by turbulent dynamos, remains challenging. We outline potential resolution of these challenges. Another intriguing possibility is that magnetic fields originated at some level from the early universe.
Magnetic fields in the intergalactic medium and in the cosmic web
Authors: Brüggen Marcus , O’Sullivan Shane , Bonafede Annalisa , Vazza Franco 
Published: March 2020

AbstractIn these proceedings we discuss advances in the theory and observation of magnetic fields in the intergalactic medium and in the cosmic web. We make the point that, despite perhaps unsurmountable obstacles in simulating a small-scale dynamo, currently most cosmological magnetohydrodynamical simulations paint a similar picture of magnetic field amplification in the cosmos. However, observations of magnetic fields in the intergalactic medium turn out to be very difficult. As a case in point, we present recent work on Faraday rotation measurement in the direction of a giant galaxy with the Low Frequency Array (LOFAR). These observations demonstrate the currently unique capability of LOFAR to measure Faraday rotation at the high accuracy and angular resolution required to investigate the magnetisation of large-scale structure filaments of the cosmic web.
A fresh view of magnetic fields and cosmic ray electrons in halos of spiral galaxies
Authors: Dettmar Ralf-Jürgen , Heesen Volker ,   the CHANG-ES Team
Published: March 2020

AbstractRecent numerical models of the multiphase ISM underline the importance of cosmic rays and magnetic fields for the physics of the ISM in disc galaxies. Observations of properties of the ISM in galactic halos constrain models of the expected exchange of matter between the star-forming disc and the environment (circumgalactic medium, CGM). We present new observational evidence from radio-continuum polarization studies of edge-on galaxies on magnetic field strength and structure as well as cosmic ray electron transport in galactic halos. The findings are discussed in the context of the disk-halo interaction of the interstellar medium. In addition, it is also briefly demonstrated how recent LOFAR observations of edge-on galaxies further constrain the extent of magnetic fields in galactic halos.
Techinques and algorithmic advances in the SKA era
Authors: Vacca V. , Govoni F. , Murgia M. , Enßlin T. , Oppermann N. , Feretti L. , Giovannini G. , Jasche J. , Junklewitz H. , Loi F. 
Published: March 2020

AbstractThe new generation of radio interferometers will deliver an unprecedented amount of deep and high resolution observations. In this proceedings, we present recent algorithmic advances in the context of the study of cosmic magnetism in order to extract all the information contained in these data.
Monitoring solar activity with PEPSI
Authors: Dineva Ekaterina , Denker Carsten , Strassmeier Klaus G. , Ilyin Ilya , Pevtsov Alexei A. 
Published: March 2020

AbstractSynoptic Sun-as-a-star observations are carried out with the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI), which receives light from the Solar Disk-Integration (SDI) telescope. Daily spectra are produced with a high signal-to-noise ratio, providing access to unprecedented quasi-continuous, long-term, disk-integrated spectra of the Sun with high spectral and temporal resolution. We developed tools to monitor and study solar activity on different time-scales ranging from daily changes, over periods related to solar rotation, to annual and decadal trends. Strong chromospheric absorption lines, such as the Ca ii H & K λ3934 & 3968 Å lines, are powerful diagnostic tools for solar activity studies, since they trace the variations of the solar magnetic field. Other lines, such as Hα λ6563 Å line and the near-infrared (NIR) Ca ii λ8542 Å line, provide additional information on the physical properties in this highly complex and dynamic atmospheric layer. Currently, we work on a data pipeline for extraction, calibration, and analysis of the PEPSI/SDI data. We compare the SDI data with daily spectra from the Integrated Sunlight Spectrometer (ISS), which is part of the Synoptic Long-Term Investigation of the Sun (SOLIS) facility operated by the U.S. National Solar Observatory (NSO). This facilitates cross-calibration and validation of the SDI data.
Strategies for flux calibration in massive spectroscopic surveys
Authors: Prieto Carlos Allende 
Published: March 2020

AbstractOptical large-scale medium-resolution spectroscopic surveys such as SDSS, LAMOST, DESI, WEAVE or 4MOST are subject to constraints that limit the choice of flux calibrators, and the attained precision. The use of optical fibers, a large but limited field of view, the tiling strategies and tight schedules, are all factors that call for a careful evaluation of the flux calibration procedures.The density of stars with well-known spectral energy distributions is so low that makes them unsuitable for flux calibration of large scale spectroscopic surveys. The alternative is to use stars with relatively simple spectra, which can be approximated well by synthetic spectra based on model atmospheres. One example are white dwarfs (Bohlin 1996), but their density is also too low for practical purposes: a few per square degree down to 19th magnitude. An alternative choice, exploited by the SDSS, are halo turn-off F-type stars (Stoughton et al.2002). A-type stars offer another option, albeit with lower densities at high Galactic latitudes (Allende Prieto del Burgo 2016). Ideally, one would use stars of various spectral types. The most common type, halo turn-off stars, can be used for the actual calibration, and the others for quality assessment.The spectral typing needs to be performed before spectra are flux calibrated. Our group has explored various strategies for continuum normalization (the removal of the instrument response), finding good results using a running mean filter (Aguado et al.2017; Allende Prieto et al.2014). Interpolation in the models speeds up the model fitting process, but it is important to ensure that interpolations are sufficiently accurate (see, e.g. Mészáros Allende Prieto 2013).Fiber-fed spectrographs are particularly challenging, since errors in positioning fibers, guiding errors, or differential atmospheric refraction, add up. In our tests with data from the Baryonic Oscillations Spectroscopic Survey (BOSS; Dawson et al.2016), we conclude that while the flux calibration is statistically accurate (<5%), individual spectra can exhibit much larger excursions, in excess of 20%.
Atomic data for stellar spectroscopy
Authors: Heiter Ulrike 
Published: March 2020

AbstractHigh-precision spectroscopy of large stellar samples plays a crucial role for several topical issues in astrophysics, such as studying the chemical evolution of the Milky Way Galaxy. Data are accumulating from instruments that obtain high-quality spectra of stars in the ultraviolet, optical and infrared wavelength regions on a routine basis. The interpretation of these spectra is often based on synthetic stellar spectra, either calculated on the fly or taken from a spectral library. One of the most important ingredients of these spectra is a set of high-quality transition data for numerous species, in particular neutral and singly ionized atoms. We rely heavily on the continuous activities of laboratory astrophysics groups that produce and improve the relevant experimental and theoretical atomic data. As an example, we briefly describe the efforts done in the context of the Gaia-ESO Public Spectroscopic Survey to compile and assess the best available data in a standard way, providing a list of recommended lines for analysis of optical spectra of FGK stars. The line data, together with specialised analysis methods, allow different surveys to obtain abundances with typical precisions of ∼0.1 dex on an industrial scale for ∼10 chemical elements. Several elements with urgent need for better atomic data have been identified.
Gaia Photometric Catalogue: the calibration of the DR2 photometry
Authors: Evans D. W. , Riello M. , De Angeli F. , Carrasco J. M. , Montegriffo P. , Fabricius C. , Jordi C. , Palaversa L. , Diener C. , Busso G. , Cacciari C. , Pancino E. , van Leeuwen F. 
Published: March 2020

AbstractGaia DR2 was released in April 2018 and contains a photometric catalogue of more than 1 billion sources. This release contains colour information in the form of integrated BP and RP photometry in addition to the latest G-band photometry. The level of uncertainty can be as good as 2 mmag with some residual systematics at the 10 mmag level. The addition of colour information greatly enhances the value of the photometric data for the scientific community. A high level overview of the photometric processing, with a focus on the improvements with respect to Gaia DR1, was given. The definition of the Gaia photometric system, a crucial part of the calibration of the photometry, was also explained. Finally, some of the photometric improvements expected for the next data release were described.
Effectively Coordinating Museums and Planetariums Worldwide
Authors: SubbaRao Mark U. 
Published: March 2020

AbstractInformal science educators at museums and planetariums face the challenging task of engaging a diverse public audience in contemporary science. To do this they need a solid background in the science itself, educational pedagogy, and modern practices in science communication. The task has gotten even more challenging in the era of big data. Interpreting and visualizing these datasets in planetarium shows and museum exhibits requires specialized technical skills. Furthermore, the increasing pace of discovery means that informal science educators have less time to accomplish these tasks. This presentation will summarize a variety of museum and planetarium community efforts to address these challenges through worldwide collaboration and coordination among museums and planetariums. Solutions include content sharing and distribution mechanisms as well as networking museums and planetariums together to create global worldwide events.
FM14 Session 3: The IAU National Outreach Coordinators (NOCs) Network – Coordinating and Catalyzing Astronomy Outreach Worldwide
Authors: Cheung Sze-leung , Simpemba Prospery C. , Benkhaldoun Zouhair , Aubé Martin , Moumen Ismael , Suleiman Raid M. , Czart Krzysztof , Brudziński Tomasz , Grochowalski Paweł , Nowak Agnieszka , Pałka Dawid , Pęcek Krzysztof , Sporna Artur , Morcos A. B. , Randriamanakoto Zara , Randrianjanahary L. , Randriamiarinarivo N. , Sosa Andrea , Albornoz Fernando , Basedas Adrian , Fariello Carlos , Gastelu Daniel , Giménez Fernando , Maciel Andrea , Méndez Oscar , Motta Katyuska , Pezano Valentina , Pintos Reina , Ramírez Jorge , Scarpa Daniel , Yamaoka Hitoshi 
Published: March 2020

AbstractSection 3 of the FM14 focus on the The IAU National Outreach Contacts (NOC) Network. This paper also contains supplementary materials that point to poster presentations that can be found online.
Modeling of Streamer Ignition and Propagation in the System of Two Approaching Hydrometeors
Authors: Jánský Jaroslav , Pasko Victor P. 
Published: March 2020

AbstractFirst‐principles plasma fluid modeling is used for investigation of electrical gas discharges ignited by a configuration of two approaching conducting hydrometeors with typical radii on the order of several millimeters under thunderstorm conditions (i.e., at an elevated location in the Earth's atmosphere corresponding to half of air density at ground level and at applied electric field approximately half of that required for avalanche multiplication of electrons in air). It is demonstrated that ultraviolet photons produced by the electrical discharges developing due to the electric field enhancement in the gap between two hydrometeors and resultant photoionization in the discharge volume lead to much less stringent conditions for conversion of these discharges to a filamentary streamer form than in the case not accounting for the effects of photoionization. It is also demonstrated that this photoionization feedback is critical for understanding and correct description of the subsequent streamer discharges developing on the outer periphery of two hydrometeors whose potential is equalized due to the electrical connection established by the initial streamer discharge between them. The initial streamer ignition between the hydrometeors can be preceded by the corona development, which can have detrimental effect on the ignition. However, it is demonstrated that for hydrometeors approaching with a speed of
10 m/s the effect of this onset corona is small.
Global Statistics of Ice Microphysical and Optical Properties at Tops of Optically Thick Ice Clouds
Authors: van Diedenhoven Bastiaan , Ackerman Andrew S. , Fridlind Ann M. , Cairns Brian , Riedi Jérôme 
Published: March 2020

AbstractThe sizes and shapes of ice crystals in clouds affect fundamental microphysical processes, such as sedimentation and aggregation, as well as their optical properties. The evolution of ice crystal size and shape depends on temperature and supersaturation, as well as on other processes that may lead to various coexisting complex shapes. Here we present a global assessment of collocated size and shape characteristics and shortwave scattering properties of ice crystals at the tops of optically thick clouds inferred from space‐borne multiwavelength reflectance measurements and multiangle polarimetry. The results indicate systematic covariations of ice size, shape, and distortion, as well as variations with temperature that can be plausibly related to simplified ice crystal growth theory and in situ and laboratory data. This simplicity may be attributable to the temperature dependence of cloud top ice size and shapes commonly being dominated by vapor growth at conditions similar to those at cloud top. Such a conclusion may be viewed as somewhat surprising given the expectation that ice properties at cloud top will be an integral manifestation of processes occurring at lower levels within updrafts. We also find that, contrary to commonly used models, ice scattering asymmetry parameters decrease with increasing effective radius, reducing sensitivity of cloud reflectance to particle size.
QBO, ENSO, and Solar Cycle Effects in Short‐Term Nonmigrating Tidal Variability on Planetary Wave Timescales From SABER—An Information‐Theoretic Approach
Authors: Kumari Komal , Oberheide Jens 
Published: March 2020

AbstractMuch progress has been made in delineating and understanding the “tidal climate” of the mesosphere and lower thermosphere, that is, tidal variability on seasonal or longer timescales. Short‐term tidal variability on timescales of a few days is much less understood, mainly due to observational constraints imposed by satellite local solar time sampling. This paper presents a new approach to study the “tidal weather” in 16 years of SABER temperatures. Our focus is on the eastward‐propagating nonmigrating diurnal tide with zonal wave number 3 (DE3) that originates from tropical convection. The statistics of short‐term tidal variability derived from “tidal deconvolution” are analyzed using an information‐theoretic approach based on Bayesian statistics and time‐dependent probability density functions. The paper particularly discusses the statistical characteristics of interannual changes in short‐term DE3 variability on a quasi‐10‐day wave (Q10DW) timescale and relates it to various forcing and propagation conditions such as Quasi‐Biennial Oscillation (QBO), El Niño‐Southern Oscillation (ENSO), and solar cycle. Understanding the response to these drivers requires a separate treatment of symmetric and antisymmetric DE3 tidal modes. Symmetric DE3 mode variability is enhanced during the easterly phase of the QBO due to enhanced Q10DW activity and during the La Niña phase of ENSO due to enhanced convective forcing but does not show a solar cycle dependence because of stable polar vortex conditions in the southern hemisphere. Antisymmetric DE3 mode variability is enhanced in the westerly phase of the QBO during solar maximum due to Q10DW activity related to a more unstable polar vortex in the northern hemisphere.
Comparative Assessment of Climate Engineering Scenarios in the Presence of Parametric Uncertainty
Authors: Tran Giang T. , Oschlies Andreas , Keller David P. 
Published: March 2020

AbstractClimate engineering (CE) measures are increasingly discussed when dealing with the adverse impacts of climate change. While much research has focused on individual methods, few studies attempt to compare and rank the effectiveness of these measures. Furthermore, model uncertainties are seldom acknowledged and lesser still, estimated when CE scenarios are assessed. In this work, we quantify the variance in outcomes due to poorly constrained model parameters under several idealized CE scenarios. The four scenarios considered are (1) warming under the high emission scenario Representative Concentration Pathway 8.5 without CE applied and the same emission scenario with (2) afforestation,(3) solar radiation management, and (4) artificial ocean alkalinization. By considering the parametric uncertainty in model outputs, we demonstrate the problems with comparing these scenarios using a single parameter setting. Using statistical emulation, we estimate the probability distributions of several model outcomes. Based on such distributions, we suggest an approach to ranking the effectiveness of the scenarios considered according to their probability of avoiding climate thresholds.