bluuebunny/crossref_metadata_2025_split huggingface dataset:
COWS: a filament finder for Hessian cosmic web identifiers
Authors: Pfeifer Simon , Libeskind Noam I , Hoffman Yehuda , Hellwing Wojciech A , Bilicki Maciej , Naidoo Krishna 
Published: May 2022

ABSTRACT
The large-scale galaxy and matter distribution is often described by means of the cosmic web made up of voids, sheets, filaments, and knots. Many different recipes exist for identifying this cosmic web. Here, we focus on a sub-class of cosmic web identifiers, based on the analysis of the Hessian matrix, and proposed a method, called COsmic Web Skeleton (COWS), of separating a set of filaments cells into an ensemble of individual discreet filaments. Specifically, a thinning algorithm is applied to velocity shear tensor-based cosmic web (V-web) to identify the spine of the filaments. This results in a set of filaments with well-defined end point and length. It is confirmed that these sit at local density ridges and align with the appropriate direction defined by the underlying velocity field. The radial density profile of these curved cylindrical filaments, as well as the distribution of their lengths is also examined. The robustness of all results is checked against resolution and the V-web threshold. The code for the COWS method has been made publicly available.
Low levels of sulphur dioxide contamination of Venusian phosphine spectra
Authors: Greaves Jane S , Rimmer Paul B , Richards Anita M S , Petkowski Janusz J , Bains William , Ranjan Sukrit , Seager Sara , Clements David L , Silva Clara Sousa , Fraser Helen J 
Published: May 2022

ABSTRACT
New analysis is presented of the 1.1 mm wavelength absorption lines in Venus’ atmosphere that suggested the presence of phosphine. We retrieve a sulphur dioxide observation from the JCMT archive that was simultaneous within a few days of the PH3 1-0 spectrum obtained in 2017 June, and demonstrate via a radiative transfer calculation that contamination of PH3 by SO2 was ≈10 per cent. We also present ALMA 2019 spectra of PH3 1-0 and an SO2 transition acquired simultaneously, and infer that SO2 line-contamination was ≲2 per cent (for the least-noisy half of the planetary disc). The contamination-subtracted ALMA and JCMT spectra (of 6–8σ sigma confidence) are now consistent with similar absorption-depths at the two epochs. The two values span −1.9(±0.2) 10−4 of the continuum signal (which was re-estimated for ALMA), albeit for differing planetary areas. This suggests that the abundance attributed to phosphine in Venus’ atmosphere was broadly similar in 2017 and 2019.
grumpy: a simple framework for realistic forward modelling of dwarf galaxies
Authors: Kravtsov Andrey , Manwadkar Viraj 
Published: May 2022

ABSTRACT
We present a simple regulator-type framework designed specifically for modelling formation of dwarf galaxies. Despite its simplicity, when coupled with realistic mass accretion histories of haloes from simulations and reasonable choices for model parameter values, the framework can reproduce a remarkably broad range of observed properties of dwarf galaxies over seven orders of magnitude in stellar mass. In particular, we show that the model can simultaneously match observational constraints on the stellar mass–halo mass relation, as well as observed relations between stellar mass and gas phase and stellar metallicities, gas mass, size, and star formation rate, as well as general form and diversity of star formation histories of observed dwarf galaxies. The model can thus be used to predict photometric properties of dwarf galaxies hosted by dark matter haloes in N-body simulations, such as colours, surface brightnesses, and mass-to-light ratios and to forward model observations of dwarf galaxies. We present examples of such modelling and show that colours and surface brightness distributions of model galaxies are in good agreement with observed distributions for dwarfs in recent observational surveys. We also show that in contrast with the common assumption, the absolute magnitude–halo mass relation is generally predicted to have a non-power law form in the dwarf regime, and that the fraction of haloes that host detectable ultra-faint galaxies is sensitive to reionization redshift (zrei) and is predicted to be consistent with observations for zrei ≲ 9.
The first nova eruption in a novalike variable: YZ Ret as seen in X-rays and γ-rays
Authors: Sokolovsky Kirill V , Li Kwan-Lok , Lopes de Oliveira Raimundo , Ness Jan-Uwe , Mukai Koji , Chomiuk Laura , Aydi Elias , Steinberg Elad , Vurm Indrek , Metzger Brian D , Babul Aliya-Nur , Kawash Adam , Linford Justin D , Nelson Thomas , Page Kim L , Rupen Michael P , Sokoloski Jennifer L , Strader Jay , Kilkenny David 
Published: May 2022

ABSTRACT
Peaking at 3.7 mag on 2020 July 11, YZ Ret was the second-brightest nova of the decade. The nova’s moderate proximity (2.7 kpc, from Gaia) provided an opportunity to explore its multiwavelength properties in great detail. Here, we report on YZ Ret as part of a long-term project to identify the physical mechanisms responsible for high-energy emission in classical novae. We use simultaneous Fermi/LAT and NuSTAR observations complemented by XMM–Newton X-ray grating spectroscopy to probe the physical parameters of the shocked ejecta and the nova-hosting white dwarf. The XMM–Newton observations revealed a supersoft X-ray emission which is dominated by emission lines of C v, C vi, N vi, N vii, and O viii rather than a blackbody-like continuum, suggesting CO-composition of the white dwarf in a high-inclination binary system. Fermi/LAT-detected YZ Ret for 15 d with the γ-ray spectrum best described by a power law with an exponential cut-off at 1.9 ± 0.6 GeV. In stark contrast with theoretical predictions and in keeping with previous NuSTAR observations of Fermi-detected classical novae (V5855 Sgr and V906 Car), the 3.5–78-keV X-ray emission is found to be two orders of magnitude fainter than the GeV emission. The X-ray emission observed by NuSTAR is consistent with a single-temperature thermal plasma model. We do not detect a non-thermal tail of the GeV emission expected to extend down to the NuSTAR band. NuSTAR observations continue to challenge theories of high-energy emission from shocks in novae.
Stellar kinematics of dwarf galaxies from multi-epoch spectroscopy: application to Triangulum II
Authors: Buttry Rachel , Pace Andrew B , Koposov Sergey E , Walker Matthew G , Caldwell Nelson , Kirby Evan N , Martin Nicolas F , Mateo Mario , Olszewski Edward W , Starkenburg Else , Badenes Carles , Daher Christine Mazzola 
Published: May 2022

ABSTRACT
We present new MMT/Hectochelle spectroscopic measurements for 257 stars observed along the line of sight to the ultrafaint dwarf galaxy Triangulum II (Tri II). Combining results from previous Keck/DEIMOS spectroscopy, we obtain a sample that includes 16 likely members of Tri II, with up to 10 independent redshift measurements per star. To this multi-epoch kinematic data set, we apply methodology that we develop in order to infer binary orbital parameters from sparsely sampled radial velocity curves with as few as two epochs. For a previously identified (spatially unresolved) binary system in Tri II, we infer an orbital solution with period $296.0_{-3.3}^{+3.8} \rm ~ d$, semimajor axis $1.12^{+0.41}_{-0.24}\rm ~au$, and systemic velocity $-380.0 \pm 1.7 \rm ~km ~s^{-1}$ that we then use in the analysis of Tri II’s internal kinematics. Despite this improvement in the modelling of binary star systems, the current data remain insufficient to resolve the velocity dispersion of Tri II. We instead find a 95 per cent confidence upper limit of $\sigma _{v} \lesssim 3.4 \rm ~km~s^{-1}$.
First discoveries and localizations of Fast Radio Bursts with MeerTRAP: real-time, commensal MeerKAT survey
Authors: Rajwade K M , Bezuidenhout M C , Caleb M , Driessen L N , Jankowski F , Malenta M , Morello V , Sanidas S , Stappers B W , Surnis M P , Barr E D , Chen W , Kramer M , Wu J , Buchner S , Serylak M , Combes F , Fong W , Gupta N , Jagannathan P , Kilpatrick C D , Krogager J-K , Noterdaeme P , Núnẽz C , Prochaska J Xavier , Srianand R , Tejos N 
Published: May 2022

ABSTRACT
We report on the discovery and localization of fast radio bursts (FRBs) from the MeerTRAP project, a commensal fast radio transient-detection programme at MeerKAT in South Africa. Our hybrid approach combines a coherent search with an average field-of-view (FoV) of 0.4 $\rm deg^{2}$ with an incoherent search utilizing a FoV of ∼1.27 $\rm deg^{2}$ (both at 1284 MHz). Here, we present results on the first three FRBs: FRB 20200413A (DM = 1990.05 pc cm−3), FRB 20200915A (DM = 740.65 pc cm−3), and FRB 20201123A (DM = 433.55 pc cm−3). FRB 20200413A was discovered only in the incoherent beam. FRB 20200915A (also discovered only in the incoherent beam) shows speckled emission in the dynamic spectrum, which cannot be explained by interstellar scintillation in our Galaxy or plasma lensing, and might be intrinsic to the source. FRB 20201123A shows a faint post-cursor burst of about 200 ms after the main burst and warrants further follow-up to confirm whether it is a repeating FRB. FRB 20201123A also exhibits significant temporal broadening, consistent with scattering, by a turbulent medium. The broadening exceeds from what is predicted for the medium along the sightline through our Galaxy. We associate this scattering with the turbulent medium in the environment of the FRB in the host galaxy. Within the approximately 1 arcmin localization region of FRB 20201123A, we identify one luminous galaxy (r ≈ 15.67; J173438.35-504550.4) that dominates the posterior probability for a host association. The galaxy’s measured properties are consistent with other FRB hosts with secure associations.
Extreme mass ratio inspirals and tidal disruption events in nuclear clusters – I. Time-dependent rates
Authors: Broggi Luca , Bortolas Elisa , Bonetti Matteo , Sesana Alberto , Dotti Massimo 
Published: May 2022

ABSTRACT
In this paper, we develop a computationally efficient, two-population, time-dependent Fokker–Plank approach in the two dimensions of energy and angular momentum to study the rates of tidal disruption events (TDEs), extreme mass ratio inspirals (EMRIs), and direct plunges occurring around massive black holes (MBHs) in galactic nuclei. We test our code by exploring a wide range of the astrophysically relevant parameter space, including MBH masses, galaxy central densities, and inner density slopes. We find that mass segregation and, more in general, the time dependency of the distribution function regulate the event rate: TDEs always decline with time, whereas EMRIs and plunges reach a maximum and undergo a subsequent nearly exponential decay. Once suitably normalized, the rates associated to different choices of MBH mass and galaxy density overlap nearly perfectly. Based on this, we provide a simple scaling that allows to reproduce the time-dependent event rates for any MBH mass and underlying galactic nucleus. Although our peak rates are in general agreement with the literature relying on the steady-state (non-time-dependent) assumption, those can be sustained on a time-scale that strongly depends on the properties of the system. In particular, this can be much shorter than a Gyr for relatively light MBHs residing in dense systems. This warns against using steady-state models to compute global TDE, EMRI, and plunge rates and calls for a more sophisticated, time-dependent treatment of the problem.
Multiple variability time-scales of the early nitrogen-rich Wolf–Rayet star WR 7
Authors: Toalá J A , Bowman D M , Van Reeth T , Todt H , Dsilva K , Shenar T , Koenigsberger G , Estrada-Dorado S , Oskinova L M , Hamann W-R 
Published: May 2022

ABSTRACT
We present the analysis of the optical variability of the early, nitrogen-rich Wolf–Rayet (WR) star WR 7. The analysis of multisector Transiting Exoplanet Survey Satellite (TESS) light curves and high-resolution spectroscopic observations confirm multiperiodic variability that is modulated on time-scales of years. We detect a dominant period of 2.6433 ± 0.0005 d in the TESS sectors 33 and 34 light curves in addition to the previously reported high-frequency features from sector 7. We discuss the plausible mechanisms that may be responsible for such variability in WR 7, including pulsations, binarity, co-rotating interaction regions (CIRs), and clumpy winds. Given the lack of strong evidence for the presence of a stellar or compact companion, we suggest that WR 7 may pulsate in quasi-coherent modes in addition to wind variability likely caused by CIRs on top of stochastic low-frequency variability. WR 7 is certainly a worthy target for future monitoring in both spectroscopy and photometry to sample both the short (≲1 d) and long (≳1000 d) variability time-scales.
Acoustic waves and g-mode turbulence as energy carriers in a viscous intracluster medium
Authors: Choudhury Prakriti Pal , Reynolds Christopher S 
Published: May 2022

ABSTRACT
Many recent works on the observed galaxy clusters in the X-rays highlight broadly two classes of exclusive energy carriers – sound waves and turbulence. In order to understand this dichotomy, we design an idealized three-dimensional hydrodynamic simulation of a cluster, to assess which of these carriers can dissipate energy in and around the core (≳100 kpc). Specifically, we explore how gentle (long-duration outbursts) and intermediate (shorter duration outbursts) feedback modes can function efficiently mediated by compressible (sound waves) and incompressible (g modes/instabilities/turbulence) disturbances. Since g modes are confined tightly to the central core, we attempt to maximize the flux of fast sound waves to distribute the feedback energy over a large distance. We find that the contribution to heat dissipation from sound and turbulence varies on the basis of the aforementioned feedback modes, namely: turbulence contributes relatively more than sound in the slow-piston regime and vice versa for the intermediate regime. For the first time in a 3D simulation, we show that up to $\lesssim 20{{\ \rm per\ cent}}$ (in some directions) of the injected power can be carried away by sound flux in the intermediate feedback but it reduces to $\lesssim 10 {{\ \rm per\ cent}}$ (in some directions) in the slow-piston regime. Lastly, we find that sound waves can be elusive if we deduce the equation of state (isobaric/isentropic) of the fluctuations from X-ray observations.
Coordinated time variability of multi-phase ultra-fast outflows in J132216.25 + 052446.3
Authors: Aromal P , Srianand R , Petitjean P 
Published: May 2022

ABSTRACT
We present a time variability analysis of broad absorption lines (BAL; spread over the velocity range of 5800–29 000 km s−1) seen in the spectrum of J132216.25 + 052446.3 (zem = 2.04806) at ten different epochs spanning over 19 yr. The strongest absorption component (BAL-A; spread over 5800–9900 km s−1) is made up of several narrow components having velocity separations close to C iv doublet splitting. The C iv, N v, and Si iv absorption from BAL-A show correlated optical depth variability without major changes in the velocity structure. A very broad and shallow absorption (BAL-C; spread over the velocity range 15 000–29 000 km s−1) emerged during our monitoring period coinciding with a dimming episode of J1322 + 0524. All the identified absorption lines show correlated variability with the equivalent widths increasing with decreasing flux. This together with the C iv emission line variability is consistent with ionization being the main driver of the correlated variability. The observed UV-continuum variations are weaker than what is required by the photoionization models. This together with a scatter in the C iv equivalent width at a given continuum flux can be understood if variations of the C iv ionizing photons are much larger than that of the UV continuum, the variations in the ionizing photon and UV fluxes are not correlated and/or the covering factor of the flow varies continuously. We suggest BAL-A is produced by a stable clumpy outflow located beyond the broad emission line region and BAL-C is a newly formed wind component located near the accretion disc and both respond to changes in the ionizing continuum.
Modelling the secular evolution of protoplanetary disc dust sizes – a comparison between the viscous and magnetic wind case
Authors: Zagaria Francesco , Rosotti Giovanni P , Clarke Cathie J , Tabone Benoît 
Published: May 2022

ABSTRACT
For many years, protoplanetary discs have been thought to evolve viscously: angular momentum redistribution leads to accretion and outward disc spreading. Recently, the hypothesis that accretion is due, instead, to angular momentum removal by magnetic winds gained new popularity: no disc spreading is expected in this case. In this paper, we run several 1D gas and dust simulations to make predictions on the time evolution of disc sizes in the dust and to assess whether they can be used to understand how discs evolve. We show that viscous and magnetic wind models have very different dust disc radii. In particular, magnetohydrodynamic wind models are compact and their sizes either remain constant or decrease with time. On the contrary, discs become larger with time in the viscous case (when α ≳ 10−3). Although current observations lack enough sensitivity to discriminate between these two scenarios, higher sensitivity surveys could be fruitful to this goal on a $1\!-\!10\, {\rm Myr}$ age range. When compared with the available ALMA (Atacama Large Millimeter/submillimeter Array) Band 7 data, both viscous and magnetic wind models are compatible with the observationally inferred dust radii in Lupus, Chamaeleon I, and Upper Sco. Furthermore, in the drift-dominated regime, the size–luminosity correlation is reproduced in Lupus, both in Band 7 and 3, while in Upper Sco a different slope than in the data is predicted. Sub-structures (potentially undetected) can explain several outliers with large observed sizes. Higher angular-resolution observations will be helpful to test our predictions in the case of more compact discs, expected in both frameworks, particularly at the age of Upper Sco.
The impact of filaments on dwarf galaxy properties in the Auriga simulations
Authors: Zheng Haonan , Liao Shihong , Hu Jia , Gao Liang , Grand Robert J J , Gu Qing , Guo Qi 
Published: May 2022

ABSTRACT
With a hydrodynamical simulation using a simple galaxy formation model without taking into account feedback, our previous work has shown that dense and massive filaments at high redshift can provide potential wells to trap and compress gas, and hence affect galaxy formation in their resident low-mass haloes. In this paper, we make use of the Auriga simulations, a suite of high-resolution zoom-in hydrodynamical simulations of Milky Way-like galaxies, to study whether the conclusion still holds in the simulations with a sophisticated galaxy formation model. In agreement with the results of our previous work, we find that, compared to their counterparts with similar halo masses in the field, dwarf galaxies residing in filaments tend to have higher baryonic and stellar fractions. At the fixed parent halo mass, the filament dwarfs tend to have slightly higher star formation rates than those of field ones. But overall we do not find a clear difference in galaxy g − r colours between the filament and field populations. We also show that at high redshifts, the gas components in dwarf galaxies tend to have their spins aligned with the filaments in which they reside. Our results support a picture in which massive filaments at high redshift assist gas accretion and enhance star formation in their resident dwarf-sized dark matter haloes.
Towards an understanding of YSO variability: a multiwavelength analysis of bursting, dipping, and symmetrically varying light curves of disc-bearing YSOs
Authors: Lakeland Ben S , Naylor Tim 
Published: May 2022

ABSTRACT
Using simultaneous optical and infrared light curves of disc-bearing young stars in NGC 2264, we perform the first multiwavelength structure function study of YSOs. We find that dippers have larger variability amplitudes than bursters and symmetric variables at all time-scales longer than a few hours. By analysing optical-infrared colour time-series, we also find that the variability in the bursters is systematically less chromatic at all time-scales than the other variability types. We propose a model of YSO variability in which symmetric, bursting, and dipping behaviour is observed in systems viewed at low, intermediate, and high inclinations, respectively. We argue that the relatively short thermal time-scale for the disc can explain the fact that the infrared light curves for bursters are more symmetric than their optical counterparts, as the disc reprocesses the light from all rotational phases. From this model, we find that the accretion variability on to these YSOs roughly follows a random-walk.
A Population-Genetic Lens into the Process of Gene Loss Following Whole-Genome Duplication
Authors: Johri Parul , Gout Jean-Francois , Doak Thomas G , Lynch Michael 
Published: May 2022

Abstract
Whole-genome duplications (WGDs) have occurred in many eukaryotic lineages. However, the underlying evolutionary forces and molecular mechanisms responsible for the long-term retention of gene duplicates created by WGDs are not well understood. We employ a population-genomic approach to understand the selective forces acting on paralogs and investigate ongoing duplicate-gene loss in multiple species of Paramecium that share an ancient WGD. We show that mutations that abolish protein function are more likely to be segregating in retained WGD paralogs than in single-copy genes, most likely because of ongoing nonfunctionalization post-WGD. This relaxation of purifying selection occurs in only one WGD paralog, accompanied by the gradual fixation of nonsynonymous mutations and reduction in levels of expression, and occurs over a long period of evolutionary time, “marking” one locus for future loss. Concordantly, the fitness effects of new nonsynonymous mutations and frameshift-causing indels are significantly more deleterious in the highly expressed copy compared with their paralogs with lower expression. Our results provide a novel mechanistic model of gene duplicate loss following WGDs, wherein selection acts on the sum of functional activity of both duplicate genes, allowing the two to wander in expression and functional space, until one duplicate locus eventually degenerates enough in functional efficiency or expression that its contribution to total activity is too insignificant to be retained by purifying selection. Retention of duplicates by such mechanisms predicts long times to duplicate-gene loss, which should not be falsely attributed to retention due to gain/change in function.