bluuebunny/crossref_metadata_2025_split huggingface dataset:
Diagnosing cosmic ray modified shocks with H α polarimetry
Authors: Shimoda Jiro , Laming J Martin 
Published: August 2019

ABSTRACT
A novel diagnostic of cosmic ray modified shocks by polarimetry of H α emissions is suggested. In a cosmic ray modified shock, the pressure of cosmic rays is sufficiently high compared to the upstream ram pressure to force the background plasma to decelerate (measured in the shock rest frame). Simultaneously, a fraction of the hydrogen atoms co-existing in the upstream plasma collide with the decelerated protons and undergo charge-exchange reactions. As a result, hydrogen atoms with the same bulk velocity of the decelerated protons are generated. We show that when the shock is observed from edge-on, the H α radiated by these upstream hydrogen atoms is linearly polarized with a sizable degree of a few per cent as a result of resonant scattering of Ly β. The polarization direction depends strongly on the velocity modification; the direction is parallel to the shock surface for the case of no modification, while the direction is parallel to the shock velocity for the case of a modified shock.
The spectral energy distributions of active galactic nuclei
Authors: Brown M J I , Duncan K J , Landt H , Kirk M , Ricci C , Kamraj N , Salvato M , Ananna T 
Published: August 2019

ABSTRACT
We present spectral energy distributions (SEDs) of 41 active galactic nuclei, derived from multiwavelength photometry and archival spectroscopy. All of the SEDs span at least 0.09 to 30 $\mu$m, but in some instances wavelength coverage extends into the X-ray, far-infrared, and radio. For some active galactic nuclei (AGNs) we have fitted the measured far-infrared photometry with greybody models, while radio flux density measurements have been approximated by power laws or polynomials. We have been able to fill some of the gaps in the spectral coverage using interpolation or extrapolation of simple models. In addition to the 41 individual AGN SEDs, we have produced 72 Seyfert SEDs by mixing SEDs of the central regions of Seyferts with galaxy SEDs. Relative to the literature, our templates have broader wavelength coverage and/or higher spectral resolution. We have tested the utility of our SEDs by using them to generate photometric redshifts for 0 &lt; z ≤ 6.12 AGNs in the Boötes field (selected with X-ray, IR, and optical criteria) and, relative to SEDs from the literature, they produce comparable or better photometric redshifts with reduced flux density residuals.
The beam balance – measuring binary systems via relativistic beaming signals from stars and their companions
Authors: Penoyre Z 
Published: August 2019

ABSTRACT
In this paper, I show that the concept of relativistic beaming – the process by which light emitted by fast-moving sources is lensed towards the direction of motion – can be easily extended to model the signal from both the star and any secondary companions. Most companions will be cooler and less massive than their host star. Their lower mass leads to faster orbital velocities, and thus a potentially larger beaming effect. The lower temperature will mean that most of their light is emitted at longer wavelengths, where the relative photometric dominance of the primary is reduced. Thus, for some systems, the secondary companion can be the main contributor to observed relativistic beaming signals at long wavelengths. Furthermore, if the system is observed over a range of wavelengths we can independently constrain the temperature of the companion, and the mass and radius ratio of the binary. To conclude, I discuss the current and future observational prospects of this signal, using the properties of known exoplanets to show that such a signal may be observable by upcoming surveys.
Potential kick velocity distribution of black hole X-ray binaries and implications for natal kicks
Authors: Atri P , Miller-Jones J C A , Bahramian A , Plotkin R M , Jonker P G , Nelemans G , Maccarone T J , Sivakoff G R , Deller A T , Chaty S , Torres M A P , Horiuchi S , McCallum J , Natusch T , Phillips C J , Stevens J , Weston S 
Published: August 2019

Abstract
We use very long baseline interferometry to measure the proper motions of three black hole X-ray binaries (BHXBs). Using these results together with data from the literature and Gaia DR2 to collate the best available constraints on proper motion, parallax, distance, and systemic radial velocity of 16 BHXBs, we determined their three-dimensional Galactocentric orbits. We extended this analysis to estimate the probability distribution for the potential kick velocity (PKV) a BHXB system could have received on formation. Constraining the kicks imparted to BHXBs provides insight into the birth mechanism of black holes (BHs). Kicks also have a significant effect on BH–BH merger rates, merger sites, and binary evolution, and can be responsible for spin–orbit misalignment in BH binary systems. 75 per cent of our systems have potential kicks $\gt 70\, \rm {km\,s^{-1}}$. This suggests that strong kicks and hence spin–orbit misalignment might be common among BHXBs, in agreement with the observed quasi-periodic X-ray variability in their power density spectra. We used a Bayesian hierarchical methodology to analyse the PKV distribution of the BHXB population, and suggest that a unimodal Gaussian model with a mean of 107 $\pm \,\,16\, \rm {km\,s^{-1}}$ is a statistically favourable fit. Such relatively high PKVs would also reduce the number of BHs likely to be retained in globular clusters. We found no significant correlation between the BH mass and PKV, suggesting a lack of correlation between BH mass and the BH birth mechanism. Our python code allows the estimation of the PKV for any system with sufficient observational constraints.
Siblings, friends and acquaintances: testing galaxy association methods
Authors: Caso J P , Vega-Martínez C A 
Published: August 2019

ABSTRACT
In order to constrain the limitations of association methods applied to galaxy surveys, we analysed the catalogue of haloes at z = 0 of a cosmological simulation, trying to reproduce the limitations dealt with by an observational survey. We focused on the percolation method, usually called the friends of friends method, commonly used in the literature. The analysis was carried out on the dark matter cosmological simulation MDPL2, from the MultiDark project. The results point to a large fraction of contaminants for massive haloes in high-density environments. Thresholds in the association parameters and the subsequent analysis of observational properties can mitigate the occurrence of fake positives. The use of tests for substructures can also be efficient in particular cases.
Timing of young radio pulsars – I. Timing noise, periodic modulation, and proper motion
Authors: Parthasarathy A , Shannon R M , Johnston S , Lentati L , Bailes M , Dai S , Kerr M , Manchester R N , Osłowski S , Sobey C , van Straten W , Weltevrede P 
Published: August 2019

ABSTRACT
The smooth spin-down of young pulsars is perturbed by two non-deterministic phenomenon, glitches, and timing noise. Although the timing noise provides insights into nuclear and plasma physics at extreme densities, it acts as a barrier to high-precision pulsar timing experiments. An improved methodology based on the Bayesian inference is developed to simultaneously model the stochastic and deterministic parameters for a sample of 85 high-$\dot{E}$ radio pulsars observed for ∼10 yr with the 64-m Parkes radio telescope. Timing noise is known to be a red process and we develop a parametrization based on the red-noise amplitude (Ared) and spectral index (β). We measure the median Ared to be $-10.4^{+1.8}_{-1.7}$ yr3/2 and β to be $-5.2^{+3.0}_{-3.8}$ and show that the strength of timing noise scales proportionally to $\nu ^{1}|\dot{\nu }|^{-0.6\pm 0.1}$, where ν is the spin frequency of the pulsar and $\dot{\nu }$ is its spin-down rate. Finally, we measure significant braking indices for 19 pulsars and proper motions for 2 pulsars, and discuss the presence of periodic modulation in the arrival times of 5 pulsars.
Working towards an optimal sampling of the 21 cm signal parameter space
Authors: Eames Evan , Doussot Aristide , Semelin Benoît 
Published: August 2019

Abstract
With a statistical detection of the 21 cm signal fluctuations from the Epoch of Reionization (EoR) expected in the next few years, there is an interest in developing robust and precise techniques to constrain the underlying astrophysical parameters. Bayesian inference with Markov Chain Monte Carlo, or different types of supervised learning for backward modelling (from signal to parameters) are examples of such techniques. They usually require many instances of forward modelling (from parameters to signal) in sampling the parameters space, either when performing the steps of the Markov Chain or when building a training sample for supervised learning. As forward modelling can be costly (if performed with numerical simulations for example), we should attempt to perform an optimal sampling according to some principle. With this goal in mind, we present an approach based on defining a metric on the space of observables, induced by the manner through which the modelling creates a mapping from the parameter space onto the space of observables. This metric bears a close connection to Jeffreys’ prior from information theory. It is used to generate a homogeneous and isotropic sampling of the signal space with two different methods. We show that when the resulting optimized samplings, created with 21cmFAST, are used to train a neural network we obtain a modest reduction of the χ2 error on parameter reconstruction of ∼20%, for one of the two optimized sampling methods, (compared to a naïve sampling of the same size).
Brown dwarf census with the Dark Energy Survey year 3 data and the thin disc scale height of early L types
Authors: Carnero Rosell A , Santiago B , dal Ponte M , Burningham B , da Costa L N , James D J , Marshall J L , McMahon R G , Bechtol K , De Paris L , Li T , Pieres A , García-Bellido J , Abbott T M C , Annis J , Avila S , Bernstein G M , Brooks D , Burke D L , Carrasco Kind M , Carretero J , De Vicente J , Drlica-Wagner A , Fosalba P , Frieman J , Gaztanaga E , Gruendl R A , Gschwend J , Gutierrez G , Hollowood D L , Maia M A G , Menanteau F , Miquel R , Plazas A A , Roodman A , Sanchez E , Scarpine V , Schindler R , Serrano S , Sevilla-Noarbe I , Smith M , Sobreira F , Soares-Santos M , Suchyta E , Swanson M E C , Tarle G , Vikram V , Walker A R ,   (DES Collaboration)
Published: August 2019

ABSTRACT
In this paper we present a catalogue of 11 745 brown dwarfs with spectral types ranging from L0 to T9, photometrically classified using data from the Dark Energy Survey (DES) year 3 release matched to the Vista Hemisphere Survey (VHS) DR3 and Wide-field Infrared Survey Explorer (WISE) data, covering ≈2400 deg2 up to iAB = 22. The classification method follows the same phototype method previously applied to SDSS-UKIDSS-WISE data. The most significant difference comes from the use of DES data instead of SDSS, which allow us to classify almost an order of magnitude more brown dwarfs than any previous search and reaching distances beyond 400 pc for the earliest types. Next, we also present and validate the GalmodBD simulation, which produces brown dwarf number counts as a function of structural parameters with realistic photometric properties of a given survey. We use this simulation to estimate the completeness and purity of our photometric LT catalogue down to iAB = 22, as well as to compare to the observed number of LT types. We put constraints on the thin disc scale height for the early L (L0–L3) population to be around 450 pc, in agreement with previous findings. For completeness, we also publish in a separate table a catalogue of 20 863 M dwarfs that passed our colour cut with spectral types greater than M6. Both the LT and the late M catalogues are found at DES release page https://des.ncsa.illinois.edu/releases/other/y3-mlt.
Dust survival rates in clumps passing through the Cas A reverse shock – I. Results for a range of clump densities
Authors: Kirchschlager Florian , Schmidt Franziska D , Barlow M J , Fogerty Erica L , Bevan Antonia , Priestley Felix D 
Published: August 2019

ABSTRACT
The reverse shock in the ejecta of core-collapse supernovae is potentially able to destroy newly formed dust material. In order to determine dust survival rates, we have performed a set of hydrodynamic simulations using the grid-based code astrobear in order to model a shock wave interacting with clumpy supernova ejecta. Dust motions and destruction rates were computed using our newly developed external, post-processing code paperboats, which includes gas drag, grain charging, sputtering, and grain–grain collisions. We have determined dust destruction rates for the oxygen-rich supernova remnant Cassiopeia A as a function of initial grain sizes and clump gas density. We found that up to $30\,\mathrm{{{\ \rm per\ cent}}}$ of the carbon dust mass is able to survive the passage of the reverse shock if the initial grain size distribution is narrow with radii around ∼10–50 nm for high gas densities, or with radii around $\sim 0.5\!-\!1.5\,\mathrm{\mu m}$ for low and medium gas densities. Silicate grains with initial radii around 10–30 nm show survival rates of up to $40\,\mathrm{{{\ \rm per\ cent}}}$ for medium- and high-density contrasts, while silicate material with micron-sized distributions is mostly destroyed. For both materials, the surviving dust mass is rearranged into a new size distribution that can be approximated by two components: a power-law distribution of small grains and a lognormal distribution of grains having the same size range as the initial distribution. Our results show that grain–grain collisions and sputtering are synergistic and that grain–grain collisions can play a crucial role in determining the surviving dust budget in supernova remnants.
The VMC survey – XXXIV. Morphology of stellar populations in the Magellanic Clouds
Authors: El Youssoufi Dalal , Cioni Maria-Rosa L , Bell Cameron P M , Rubele Stefano , Bekki Kenji , de Grijs Richard , Girardi Léo , Ivanov Valentin D , Matijevic Gal , Niederhofer Florian , Oliveira Joana M , Ripepi Vincenzo , Subramanian Smitha , van Loon Jacco Th 
Published: August 2019

ABSTRACT
The Magellanic Clouds are nearby dwarf irregular galaxies whose morphologies show different properties when traced by different stellar populations, making them an important laboratory for studying galaxy morphologies. We study the morphology of the Magellanic Clouds using data from the Visible and Infrared Survey Telescope for Astronomy survey of the Magellanic Clouds system. We used about 10 and 2.5 million sources across an area of ∼105 and ∼42 deg2 towards the Large and Small Magellanic Cloud (LMC and SMC), respectively. We estimated median ages of stellar populations occupying different regions of the near-infrared (J − Ks, Ks) colour–magnitude diagram. Morphological maps were produced and detailed features in the central regions were characterized for the first time with bins corresponding to a spatial resolution of 0.13 kpc (LMC) and 0.16 kpc (SMC). In the LMC, we find that main-sequence stars show coherent structures that grow with age and trace the multiple spiral arms of the galaxy, star-forming regions become dimmer as we progress in age, while supergiant stars are centrally concentrated. Intermediate-age stars, despite tracing a regular and symmetrical morphology, show central clumps and hints of spiral arms. In the SMC, young main-sequence stars depict a broken bar. Intermediate-age populations show signatures of elongation towards the Magellanic Bridge that can be attributed to the LMC–SMC interaction ∼200 Myr ago. They also show irregular central features suggesting that the inner SMC has also been influenced by tidal interactions.
Predicting relationships between solar jet variables
Authors: Freeman Leonard A 
Published: August 2019

Abstract
Studies of spicules and similar solar jets reveal a strong correlation between some of the kinematic variables, particularly between the initial velocity V, and the subsequent deceleration, a. It has been proposed that there is a linear relationship between these two variables and that this offers proof for a shock wave mechanism acting on the spicules, although the linear equations found are all different. It is shown here that the relationship is better described by a non-linear form: V is proportional to the square root of a. This relationship between V and a also provides a simple physical interpretation for the results. The different linear equations are found to be simply tangents to this (a, V) curve. Another method used to investigate the (a, V) connection is to determine the correlation coefficients between the kinematic variables from their scatter plots. It is also shown how these correlations also can be predicted from the mean value of the acceleration and height and their standard deviations for the sample under consideration. The implications of these results and the possibility that spicule behaviour is partly due to magnetic fields are discussed.
Dust accretion in binary systems: implications for planets and transition discs
Authors: Chachan Yayaati , Booth Richard A , Triaud Amaury H M J , Clarke Cathie 
Published: August 2019

Abstract
The presence of planets in binary systems poses interesting problems for planet formation theories, both in cases where planets must have formed in very compact discs around the individual stars and where they are located near the edge of the stable circumbinary region, where in situ formation is challenging. Dust dynamics is expected to play an important role in such systems, since dust trapping at the inner edge of circumbinary discs could aid in situ formation, but would simultaneously starve the circumstellar discs of the solid material needed to form planets. Here we investigate the dynamics of dust in binary systems using Smooth Particle Hydrodynamics. We find that all our simulations tend towards dust trapping in the circumbinary disc, but the timescale on which trapping begins depends on binary mass ratio (q) and eccentricity as well as the angular momentum of the infalling material. For q ≳ 0.1, we find that dust can initially accrete onto the circumstellar discs, but as the circumbinary cavity grows in radius, dust eventually becomes trapped in the circumbinary disc. For q = 0.01, we find that increasing the binary eccentricity increases the time required for dust trapping to begin. However, even this longer timescale is likely to be shorter than the planet formation timescale in the inner disc and is insufficient to explain the observed pre-transitional discs. This indicates that increase in companion eccentricity alone is not enough to allow significant transfer of solids from the outer to the inner disc.
Galaxy properties as revealed by MaNGA – II. Differences in stellar populations of slow and fast rotator ellipticals and dependence on environment
Authors: Bernardi M , Domínguez Sánchez H , Brownstein J R , Drory N , Sheth R K 
Published: August 2019

ABSTRACT
We present estimates of stellar population (SP) gradients from stacked spectra of slow rotator (SR) and fast rotator (SR) elliptical galaxies from the MaNGA-DR15 survey. We find that (1) FRs are ∼5 Gyr younger, more metal rich, less α-enhanced and smaller than SRs of the same luminosity Lr and central velocity dispersion σ0. This explains why when one combines SRs and FRs, objects which are small for their Lr and σ0 tend to be younger. Their SP gradients are also different. (2) Ignoring the FR/SR dichotomy leads one to conclude that compact galaxies are older than their larger counterparts of the same mass, even though almost the opposite is true for FRs and SRs individually. (3) SRs with σ0 ≤ 250 km s−1 are remarkably homogeneous within ∼Re: they are old, α-enhanced, and only slightly supersolar in metallicity. These SRs show no gradients in age and M*/Lr, negative gradients in metallicity, and slightly positive gradients in [α/Fe] (the latter are model dependent). SRs with σ0 ≥ 250 km s−1 are slightly younger and more metal rich, contradicting previous work suggesting that age increases with σ0. They also show larger M*/Lr gradients. (4) Self-consistently accounting for M*/L gradients yields Mdyn ≈ M* because gradients reduce Mdyn by ∼0.2 dex while only slightly increasing the M* inferred using a Kroupa (not Salpeter) initial mass function. (5) The SR population starts to dominate the counts above $M_*\ge 3\times 10^{11}\, \mathrm{M}_\odot$; this is the same scale at which the size–mass correlation and other scaling relations change. Our results support the finding that this is an important mass scale that correlates with the environment and above which mergers matter.
De novo design of programmable inducible promoters
Authors: Liu Xiangyang , Gupta Sanjan T P , Bhimsaria Devesh , Reed Jennifer L , Rodríguez-Martínez José A , Ansari Aseem Z , Raman Srivatsan 
Published: August 2019

Abstract
Ligand-responsive allosteric transcription factors (aTF) play a vital role in genetic circuits and high-throughput screening because they transduce biochemical signals into gene expression changes. Programmable control of gene expression from aTF-regulated promoter is important because different downstream effector genes function optimally at different expression levels. However, tuning gene expression of native promoters is difficult due to complex layers of homeostatic regulation encoded within them. We engineered synthetic promoters de novo by embedding operator sites with varying affinities and radically reshaped binding preferences within a minimal, constitutive Escherichia coli promoter. Multiplexed cell-based screening of promoters for three TetR-like aTFs generated with this approach gave rich diversity of gene expression levels, dynamic ranges and ligand sensitivities and were 50- to 100-fold more active over their respective native promoters. Machine learning on our dataset revealed that relative position of the core motif and bases flanking the core motif play an important role in modulating induction response. Our generalized approach yields customizable and programmable aTF-regulated promoters for engineering cellular pathways and enables the discovery of new small molecule biosensors.
Assessment of kinship detection using RNA-seq data
Authors: Blay Natalia , Casas Eduard , Galván-Femenía Iván , Graffelman Jan , de Cid Rafael , Vavouri Tanya 
Published: August 2019

AbstractAnalysis of RNA sequencing (RNA-seq) data from related individuals is widely used in clinical and molecular genetics studies. Prediction of kinship from RNA-seq data would be useful for confirming the expected relationships in family based studies and for highlighting samples from related individuals in case-control or population based studies. Currently, reconstruction of pedigrees is largely based on SNPs or microsatellites, obtained from genotyping arrays, whole genome sequencing and whole exome sequencing. Potential problems with using RNA-seq data for kinship detection are the low proportion of the genome that it covers, the highly skewed coverage of exons of different genes depending on expression level and allele-specific expression. In this study we assess the use of RNA-seq data to detect kinship between individuals, through pairwise identity by descent (IBD) estimates. First, we obtained high quality SNPs after successive filters to minimize the effects due to allelic imbalance as well as errors in sequencing, mapping and genotyping. Then, we used these SNPs to calculate pairwise IBD estimates. By analysing both real and simulated RNA-seq data we show that it is possible to identify up to second degree relationships using RNA-seq data of even low to moderate sequencing depth.