bluuebunny/crossref_metadata_2025_split huggingface dataset:
The KMOS Lens-Amplified Spectroscopic Survey (KLASS): kinematics and clumpiness of low-mass galaxies at cosmic noon
Authors: Girard M , Mason C A , Fontana A , Dessauges-Zavadsky M , Morishita T , Amorín R , Fisher D B , Jones T , Schaerer D , Schmidt K B , Treu T , Vulcani B 
Published: July 2020

ABSTRACT
We present results from the KMOS Lens-Amplified Spectroscopic Survey (KLASS), an ESO Very Large Telescope (VLT) large program using gravitational lensing to study the spatially resolved kinematics of 44 star-forming galaxies at 0.6 &lt; z &lt; 2.3 with a stellar mass of 8.1 &lt; log(M⋆/M⊙) &lt; 11.0. These galaxies are located behind six galaxy clusters selected from the Hubble Space Telescope Grism Lens-Amplified Survey from Space (GLASS). We find that the majority of the galaxies show a rotating disc, but most of the rotation-dominated galaxies only have a low υ rot/σ0 ratio (median of υrot/σ0 ∼ 2.5). We explore the Tully–Fisher relation by adopting the circular velocity, $V_{\mathrm{ circ}}=(\upsilon _{\mathrm{ rot}}^2+3.4\sigma _0^2)^{1/2}$, to account for pressure support. We find that our sample follows a Tully–Fisher relation with a positive zero-point offset of +0.18 dex compared to the local relation, consistent with more gas-rich galaxies that still have to convert most of their gas into stars. We find a strong correlation between the velocity dispersion and stellar mass in the KLASS sample. When combining our data to other surveys from the literature, we see an increase of the velocity dispersion with stellar mass at all redshift. We obtain an increase of υrot/σ0 with stellar mass at 0.5 &lt; z &lt; 1.0. This could indicate that massive galaxies settle into regular rotating discs before the low-mass galaxies. For higher redshift (z &gt; 1), we find a weak increase or flat trend. We find no clear trend between the rest-frame UV clumpiness and the velocity dispersion and υrot/σ0. This could suggest that the kinematic properties of galaxies evolve after the clumps formed in the galaxy disc or that the clumps can form in different physical conditions.
Estimating local seeing at Observatorio Astronómico Nacional in San Pedro Mártir using CFD simulations of the atmospheric boundary layer
Authors: Sánchez García R , Richer M G , Gómez Martínez R , Avila R 
Published: July 2020

ABSTRACT
We present computational fluid dynamics simulations of the atmospheric boundary layer (ABL) at the Observatorio Astronómico Nacional in the Sierra San Pedro Mártir (OAN-SPM) whose objective is to model the seeing observed at the site. We constrain the simulations using observations of the seeing, the vertical profile of the wind speed, and the vertical profile of the temperature, the first two resolved as a function of wind direction. We successfully model the seeing observed under typical wind conditions for each direction by adopting input profiles of the wind speed, the turbulent kinetic energy, and the energy dissipation. The resulting vertical profiles of the index of refraction structure constant are qualitatively similar to the mean profile derived from studies at the site.
The formation times and building blocks of Milky Way-mass galaxies in the FIRE simulations
Authors: Santistevan Isaiah B , Wetzel Andrew , El-Badry Kareem , Bland-Hawthorn Joss , Boylan-Kolchin Michael , Bailin Jeremy , Faucher-Giguère Claude-André , Benincasa Samantha 
Published: July 2020

ABSTRACT
Surveys of the Milky Way (MW) and M31 enable detailed studies of stellar populations across ages and metallicities, with the goal of reconstructing formation histories across cosmic time. These surveys motivate key questions for galactic archaeology in a cosmological context: When did the main progenitor of an MW/M31-mass galaxy form, and what were the galactic building blocks that formed it? We investigate the formation times and progenitor galaxies of MW/M31-mass galaxies using the Feedback In Realistic Environments-2 cosmological simulations, including six isolated MW/M31-mass galaxies and six galaxies in Local Group (LG)-like pairs at z = 0. We examine main progenitor ‘formation’ based on two metrics: (1) transition from primarily ex-situ to in-situ stellar mass growth and (2) mass dominance compared to other progenitors. We find that the main progenitor of an MW/M31-mass galaxy emerged typically at z ∼ 3–4 ($11.6\!\!-\!\!12.2\, \rm {Gyr}$ ago), while stars in the bulge region (inner 2 kpc) at z = 0 formed primarily in a single main progenitor at z ≲ 5 (${\lesssim} \!12.6\, \rm {Gyr}$ ago). Compared with isolated hosts, the main progenitors of LG-like paired hosts emerged significantly earlier (Δz ∼ 2, $\Delta t\!\sim \!1.6\, \rm {Gyr}$), with ∼4× higher stellar mass at all z ≳ 4 (${\gtrsim} \!12.2\, \rm {Gyr}$ ago). This highlights the importance of environment in MW/M31-mass galaxy formation, especially at early times. On average, about 100 galaxies with $\rm {\it{ M}}_\rm {star}\!\gtrsim \!10^5\, \rm {M}_\odot$ went into building a typical MW/M31-mass system. Thus, surviving satellites represent a highly incomplete census (by ∼5×) of the progenitor population.
The effect of non-linear mutual friction on pulsar glitch sizes and rise times
Authors: Celora T , Khomenko V , Antonelli M , Haskell B 
Published: July 2020

ABSTRACT
Observations of pulsar glitches have the potential to provide constraints on the dynamics of the high density interior of neutron stars. However, to do so, realistic glitch models must be constructed and compared to the data. We take a step towards this goal by testing non-linear models for the mutual friction force, which is responsible for the exchange of angular momentum between the neutron superfluid and the observable normal component in a glitch. In particular, we consider a non-linear dependence of the drag force on the relative velocity between superfluid vortices and the normal component, in which the contributions of both kelvin and phonon excitations are included. This non-linear model produces qualitatively new features, and is able to reproduce the observed bimodal distribution of glitch sizes in the pulsar population. The model also suggests that the differences in size distributions in individual pulsars may be due to the glitches being triggered in regions with different pinning strengths, as stronger pinning leads to higher vortex velocities and a qualitatively different mutual friction coupling with respect to the weak pinning case. Glitches in pulsars that appear to glitch quasi-periodically with similar sizes may thus be due to the same mechanisms as smaller events in pulsars that have no preferred glitch size, but simply originate in stronger pinning regions, possibly in the core of the star.
The low-luminosity Type II SN 2016aqf: a well-monitored spectral evolution of the Ni/Fe abundance ratio
Authors: Müller-Bravo Tomás E , Gutiérrez Claudia P , Sullivan Mark , Jerkstrand Anders , Anderson Joseph P , González-Gaitán Santiago , Sollerman Jesper , Arcavi Iair , Burke Jamison , Galbany Lluís , Gal-Yam Avishay , Gromadzki Mariusz , Hiramatsu Daichi , Hosseinzadeh Griffin , Howell D Andrew , Inserra Cosimo , Kankare Erki , Kozyreva Alexandra , McCully Curtis , Nicholl Matt , Smartt Stephen , Valenti Stefano , Young Dave R 
Published: July 2020

ABSTRACTLow-luminosity Type II supernovae (LL SNe II) make up the low explosion energy end of core-collapse SNe, but their study and physical understanding remain limited. We present SN 2016aqf, an LL SN II with extensive spectral and photometric coverage. We measure a V-band peak magnitude of −14.58 mag, a plateau duration of ∼100 d, and an inferred 56Ni mass of 0.008 ± 0.002 M⊙. The peak bolometric luminosity, Lbol ≈ 1041.4 erg s−1, and its spectral evolution are typical of other SNe in the class. Using our late-time spectra, we measure the [O i] λλ6300, 6364 lines, which we compare against SN II spectral synthesis models to constrain the progenitor zero-age main-sequence mass. We find this to be 12 ± 3 M⊙. Our extensive late-time spectral coverage of the [Fe ii] λ7155 and [Ni ii] λ7378 lines permits a measurement of the Ni/Fe abundance ratio, a parameter sensitive to the inner progenitor structure and explosion mechanism dynamics. We measure a constant abundance ratio evolution of $0.081^{+0.009}_{-0.010}$ and argue that the best epochs to measure the ratio are at ∼200–300 d after explosion. We place this measurement in the context of a large sample of SNe II and compare against various physical, light-curve, and spectral parameters, in search of trends that might allow indirect ways of constraining this ratio. We do not find correlations predicted by theoretical models; however, this may be the result of the exact choice of parameters and explosion mechanism in the models, the simplicity of them, and/or primordial contamination in the measured abundance ratio.
Machine learning classification of Kuiper belt populations
Authors: Smullen Rachel A , Volk Kathryn 
Published: July 2020

ABSTRACT
In the outer Solar system, the Kuiper belt contains dynamical subpopulations sculpted by a combination of planet formation and migration and gravitational perturbations from the present-day giant planet configuration. The subdivision of observed Kuiper belt objects (KBOs) into different dynamical classes is based on their current orbital evolution in numerical integrations of their orbits. Here, we demonstrate that machine learning algorithms are a promising tool for reducing both the computational time and human effort required for this classification. Using a Gradient Boosting Classifier, a type of machine learning regression tree classifier trained on features derived from short numerical simulations, we sort observed KBOs into four broad, dynamically distinct populations – classical, resonant, detached, and scattering – with a &gt;97 per cent accuracy for the testing set of 542 securely classified KBOs. Over 80 per cent of these objects have a &gt;3σ probability of class membership, indicating that the machine learning method is classifying based on the fundamental dynamical features of each population. We also demonstrate how, by using computational savings over traditional methods, we can quickly derive a distribution of class membership by examining an ensemble of object clones drawn from the observational errors. We find two major reasons for misclassification: inherent ambiguity in the orbit of the object – for instance, an object that is on the edge of resonance – and a lack of representative examples in the training set. This work provides a promising avenue to explore for fast and accurate classification of the thousands of new KBOs expected to be found by surveys in the coming decade.
GEOMAX: beyond linear compression for three-point galaxy clustering statistics
Authors: Gualdi Davide , Gil-Marín Héctor , Manera Marc , Joachimi Benjamin , Lahav Ofer 
Published: July 2020

ABSTRACT
We present the GEOMAX algorithm and its python implementation for a two-step compression of bispectrum measurements. The first step groups bispectra by the geometric properties of their arguments; the second step then maximizes the Fisher information with respect to a chosen set of model parameters in each group. The algorithm only requires the derivatives of the data vector with respect to the parameters and a small number of mock data, producing an effective, non-linear compression. By applying GEOMAX to bispectrum monopole measurements from BOSS DR12 CMASS redshift-space galaxy clustering data, we reduce the 68 per cent credible intervals for the inferred parameters (b1, b2, f, σ8) by 50.4, 56.1, 33.2, and 38.3 per cent with respect to standard MCMC on the full data vector. We run the analysis and comparison between compression methods over 100 galaxy mocks to test the statistical significance of the improvements. On average, GEOMAX performs ∼15 per cent better than geometrical or maximal linear compression alone and is consistent with being lossless. Given its flexibility, the GEOMAX approach has the potential to optimally exploit three-point statistics of various cosmological probes like weak lensing or line-intensity maps from current and future cosmological data sets such as DESI, Euclid, PFS, and SKA.
A non-linear mathematical model for the X-ray variability of the microquasar GRS 1915+105 – III. Low-frequency quasi-periodic oscillations
Authors: Massaro E , Capitanio F , Feroci M , Mineo T 
Published: July 2020

ABSTRACT
The X-ray emission from the microquasar GRS 1915+105 shows, together with a very complex variability on different time-scales, the presence of low-frequency quasi-periodic oscillations (LFQPOs) at frequencies lower than ∼30 Hz. In this paper, we demonstrate that these oscillations can be consistently and naturally obtained as solutions of a system of two ordinary differential equations, which is able to reproduce almost all variability classes of GRS 1915+105. We modified the Hindmarsh–Rose model and obtained a system with two dynamical variables x(t), y(t), where the first one represents the X-ray flux from the source, and an input function J(t), whose mean level J0 and its time evolution is responsible of the variability class. We found that for values of J0 around the boundary between the unstable and the stable interval, where the equilibrium points are of spiral type, one obtains an oscillating behaviour in the model light curve similar to the observed ones with a broad Lorentzian feature in the power density spectrum and, occasionally, with one or two harmonics. Rapid fluctuations of J(t), as those originating from turbulence, stabilize the LFQPOs, resulting in a slowly amplitude modulated pattern. To validate the model, we compared the results with real RXTE data, which resulted remarkably similar to those obtained from the mathematical model. Our results allow us to favour an intrinsic hypothesis on the origin of LFQPOs in accretion discs ultimately related to the same mechanism responsible for the spiking limit cycle.
Analysis of Phobos’ dynamical environment considering effects of ephemerides and physical libration
Authors: Wang Yue , Wu Xiaojie 
Published: July 2020

ABSTRACT
A dynamical model is developed in the body-fixed frame of Phobos, in which the high-precision gravity field and exact physical libration of Phobos, the gravity of Mars with J2, and the gravity perturbations of the Sun, Jupiter, and Earth are considered. The JPL development ephemeris are applied to calculate the positions of celestial bodies. Phobos is considered as a homogeneous polyhedron with 16 037 vertices to characterize its irregular shape and the corresponding gravity field. The physical libration of Phobos is incorporated into its rotational motion by using the results in ‘Report of the IAU WGCCRE’. With the proposed model, equivalent gravity and slope on Phobos surface are calculated and analysed. The liftoff velocity is also computed and presented. Besides, the orbital environment is also investigated. Instantaneous equilibrium points in the Mars–Phobos system are computed and demonstrated, and the acceleration of a particle in the vicinity of Phobos is analysed to find out the main influencing factor in different regions. Quasi-satellite orbits and libration point orbits, which were determined in the circular restricted three-body problem model, are simulated in different dynamical models. The results applying the newly developed high-fidelity dynamical model have shown significant differences with respect to existing models, suggesting that dynamical models with higher accuracy are needed for close-range orbital activities.
Probing the high-z IGM with the hyperfine transition of 3He+
Authors: Khullar Shivan , Ma Qingbo , Busch Philipp , Ciardi Benedetta , Eide Marius B , Kakiichi Koki 
Published: July 2020

ABSTRACT
The hyperfine transition of 3He+ at 3.5 cm has been thought as a probe of the high-z IGM, since it offers a unique insight into the evolution of the helium component of the gas, as well as potentially give an independent constraint on the 21 cm signal from neutral hydrogen. In this paper, we use radiative transfer simulations of reionization driven by sources such as stars, X-ray binaries, accreting black holes and shock heated interstellar medium, and simulations of a high-z quasar to characterize the signal and analyse its prospects of detection. We find that the peak of the signal lies in the range ∼1–50 μK for both environments, but while around the quasar it is always in emission, in the case of cosmic reionization a brief period of absorption is expected. As the evolution of He ii is determined by stars, we find that it is not possible to distinguish reionization histories driven by more energetic sources. On the other hand, while a bright QSO produces a signal in 21 cm that is very similar to the one from a large collection of galaxies, its signature in 3.5 cm is very peculiar and could be a powerful probe to identify the presence of the QSO. We analyse the prospects of the signal’s detectability using SKA1-mid as our reference telescope. We find that the noise power spectrum dominates over the power spectrum of the signal, although a modest signal-to-noise ratio can be obtained when the wavenumber bin width and the survey volume are sufficiently large.
VALES VI: ISM enrichment in star-forming galaxies up to z ∼ 0.2 using 12CO(1–0), 13CO(1–0), and C18O(1–0) line luminosity ratios
Authors: Méndez-Hernández H , Ibar E , Knudsen K K , Cassata P , Aravena M , Michałowski M J , Zhang Zhi-Yu , Lara-López M A , Ivison R J , van der Werf P , Villanueva V , Herrera-Camus R , Hughes T M 
Published: July 2020

ABSTRACT
We present Atacama Large Millimeter/sub-millimeter Array (ALMA) observations towards 27 low-redshift (0.02 &lt; z &lt; 0.2) star-forming galaxies taken from the Valparaíso ALMA/APEX Line Emission Survey. We perform stacking analyses of the 12CO(1–0), 13CO(1–0), and C18O(1–0) emission lines to explore the L′ [12CO(1–0)]/L′ [13CO(1–0)] [hereafter L′ (12CO)/L′ (13CO)] and L′ [13CO(1–0)]/L′ [C18O(1–0)] [hereafter L′ (13CO)/L′ (C18O)] line luminosity ratio dependence as a function of different global galaxy parameters related to the star formation activity. The sample has far-IR luminosities of $10^{10.1\!-\!11.9}\,$ L⊙ and stellar masses of 109.8–10.9 M⊙ corresponding to typical star-forming and starburst galaxies at these redshifts. On average, we find an L′ (12CO)/L′ (13CO) line luminosity ratio value of 16.1 ± 2.5. Galaxies with pieces of evidence of possible merging activity tend to show higher L′ (12CO)/L′ (13CO) ratios by a factor of 2, while variations of this order are also found in galaxy samples with higher star formation rates (SFRs) or star formation efficiencies (SFEs). We also find an average L′ (13CO)/L′ (C18O) line luminosity ratio of 2.5 ± 0.6, which is in good agreement with those previously reported for starburst galaxies. We find that galaxy samples with high LIR, SFR, and SFE show low L′ (13CO)/L′ (C18O) line luminosity ratios with high L′ (12CO)/L′ (13CO) line luminosity ratios, suggesting that these trends are produced by selective enrichment of massive stars in young starbursts.
MeerKAT-16 H i observation of the dIrr galaxy WLM
Authors: Ianjamasimanana Roger , Namumba Brenda , Ramaila Athanaseus J T , Saburova Anna S , Józsa Gyula I G , Myburgh Talon , Thorat Kshitij , Carignan Claude , Maina Eric , de Blok W J G , Andati Lexy A L , Hugo Benjamin V , Kleiner Dane , Kamphuis Peter , Serra Paolo , Smirnov Oleg M , Maccagni Filippo M , Makhathini Sphesihle , Molnár Dániel Cs , Perkins Simon , Ramatsoku Mpati , White Sarah V 
Published: July 2020

ABSTRACT
We present observations and models of the kinematics and the distribution of the neutral hydrogen (H i) in the isolated dwarf irregular galaxy, Wolf-Lundmark-Melotte (WLM). We observed WLM with the Green Bank Telescope (GBT) and as part of the MeerKAT Early Science Programme, where 16 dishes were available. The H i disc of WLM extends out to a major axis diameter of 30 arcmin (8.5 kpc), and a minor axis diameter of 20 arcmin (5.6 kpc) as measured by the GBT. We use the MeerKAT data to model WLM using the tirific software suite, allowing us to fit different tilted-ring models and select the one that best matches the observation. Our final best-fitting model is a flat disc with a vertical thickness, a constant inclination and dispersion, and a radially varying surface brightness with harmonic distortions. To simulate bar-like motions, we include second-order harmonic distortions in velocity in the tangential and vertical directions. We present a model with only circular motions included and a model with non-circular motions. The latter describes the data better. Overall, the models reproduce the global distribution and the kinematics of the gas, except for some faint emission at the 2σ level. We model the mass distribution of WLM with pseudo-isothermal (ISO) and Navarro–Frenk–White (NFW) dark matter halo models. The NFW and the ISO models fit the derived rotation curves within the formal errors, but with the ISO model giving better reduced chi-square values. The mass distribution in WLM is dominated by dark matter at all radii.
On the cosmological performance of photometrically classified supernovae with machine learning
Authors: Santos Marcelo Vargas dos , Quartin Miguel , Reis Ribamar R R 
Published: July 2020

ABSTRACT
The efficient classification of different types of supernovae is one of the most important problems for observational cosmology. However, spectroscopic confirmation of most objects in upcoming photometric surveys, such as the the Rubin Observatory Legacy Survey of Space and Time, will be unfeasible. The development of automated classification processes based on photometry has thus become crucial. In this paper, we investigate the performance of machine learning (ML) classification on the final cosmological constraints using simulated light-curves from the Supernova Photometric Classification Challenge, released in 2010. We study the use of different feature sets for the light-curves and many different ML pipelines based on either decision-tree ensembles or automated search processes. To construct the final catalogues we propose a threshold selection method, by employing a bias-variance tradeoff. This is a very robust and efficient way to minimize the mean squared error. With this method, we were able to obtain very strong cosmological constraints, which allowed us to keep $\sim 75{{\ \rm per\ cent}}$ of the total information in the Type Ia supernovae when using the SALT2 feature set, and $\sim 33{{\ \rm per\ cent}}$ for the other cases (based either on the Newling model or on standard wavelet decomposition).
The κ-cookbook: a novel generalizing approach to unify κ-like distributions for plasma particle modelling
Authors: Scherer K , Husidic E , Lazar M , Fichtner H 
Published: July 2020

ABSTRACT
In the literature different so-called κ-distribution functions are discussed to fit and model the velocity (or energy) distributions of solar wind species, pickup ions, or magnetospheric particles. Here, we introduce a generalized (isotropic) κ-distribution as a ‘cookbook’, which admits as special cases, or ‘recipes’, all the other known versions of κ-models. A detailed analysis of the generalized distribution function is performed, providing general analytical expressions for the velocity moments, Debye length, and entropy, and pointing out a series of general requirements that plasma distribution functions should satisfy. From a contrasting analysis of the recipes found in the literature, we show that all of them lead to almost the same macroscopic parameters with a small standard deviation between them. However, one of these recipes called the regularized κ-distribution provides a functional alternative for macroscopic parametrization without any constraint for the power-law exponent κ.