bluuebunny/crossref_metadata_2025 huggingface dataset:
Tracing Milky Way substructure with an RR Lyrae hierarchical clustering forest
Authors: Cook Brian T , Woods Deborah F , Ruprecht Jessica D , Varey Jacob , Mastandrea Radha , de Soto Kaylee , Harburg Jacob F , Rebbapragada Umaa , Mahabal Ashish A
Published: April 2022

RR Lyrae variable stars have long been reliable standard candles used to discern structure in the Local Group. With this in mind, we present a routine to identify groupings containing a statistically significant number of RR Lyrae variables in the Milky Way environment. RR Lyrae variable groupings, or substructures, with potential Galactic archaeology applications are found using a forest of agglomerative, hierarchical clustering trees, whose leaves are Milky Way RR Lyrae variables. Each grouping is validated by ensuring that the internal RR Lyrae variable proper motions are sufficiently correlated. Photometric information was collected from the Gaia second data release and proper motions from the (early) third data release. After applying this routine to the catalogue of 91 234 variables, we are able to report 16 unique RR Lyrae substructures with physical sizes of less than 1 kpc. Five of these substructures are in close proximity to Milky Way globular clusters with previously known tidal tails and/or a potential connection to Galactic merger events. One candidate substructure is in the neighbourhood of the Large Magellanic Cloud but is more distant (and older) than known satellites of the dwarf galaxy. Our study ends with a discussion of ways in which future surveys could be applied to the discovery of Milky Way stellar streams.
Multiwavelength temporal and spectral analysis of Blazar S5 1803+78
Authors: Priya Shruti , Prince Raj , Agarwal Aditi , Bose Debanjan , Özdönmez Aykut , Ege Ergün
Published: April 2022

Blazars are a class of AGN, one of their jets is pointed towards the earth. Here, we report about the multiwavelength study for blazar S5 1803+78 between MJD 58727 and MJD 59419. We analysed gamma-ray data collected by Fermi-LAT, X-ray data collected by Swift-XRT & NuSTAR, and optical photons detected by Swift-UVOT & TUBITAK observatory in Turkey. Three flaring states are identified by analysing the gamma-ray light curve. A day-scale variability is observed throughout the flares with the similar rise and decay times suggesting a compact emission region located close to the central engine. Cross-correlation studies are carried out between gamma-ray, radio, and X-ray bands, and no significant correlation is detected. The gamma-ray and optical emission are significantly correlated with zero time lag suggesting a co-spatial origin of them. The broad-band spectral energy distribution (SED) modelling was performed for all the flaring episodes as well as for one quiescent state for comparison. SEDs are best fitted with the synchrotron-self Compton (SSC) model under a one-zone leptonic scenario. The SED modelling shows that to explain the high flaring state, strong Doppler boosting is required.
Approach of the Hyades star cluster to the Solar system
Authors: Vereshchagin S V , Emel'yanenko V V , Sizova M D
Published: April 2022

We present the results of calculations of the motion of the Hyades open cluster in the gravitational field of the Galaxy in the recent past. Our calculations show that the recent close passage of Hyades by the Solar system could cause a noticeable shift of the perihelion distances q of comets. The shift is negligible from q = 3 au to 2.6 au for the semimajor axes a = 14 210 au, but for a = 40 000 au, the perihelion could change from q = 35 au to 34 au, and much more for distant orbits. This could result in the detection of new comets, and drive the migration of comets from the outer region of the Solar system towards the orbit of Neptune. The effect can be enhanced by the simultaneous passage of several stars. For example, if several stars approached the Sun simultaneously in the time interval from −1.5 to −1.0 Myr, the effect may be amplified up to ten times.
Being KLEVER at cosmic noon: Ionized gas outflows are inconspicuous in low-mass star-forming galaxies but prominent in massive AGN hosts
Authors: Concas Alice , Maiolino Roberto , Curti Mirko , Hayden-Pawson Connor , Cirasuolo Michele , Jones Gareth C , Mercurio Amata , Belfiore Francesco , Cresci Giovanni , Cullen Fergus , Mannucci Filippo , Marconi Alessandro , Cappellari Michele , Cicone Claudia , Peng Yingjie , Troncoso Paulina
Published: April 2022

We investigate the presence of ionized gas outflows in a sample of 141 main-sequence star-forming galaxies at 1.2 < z < 2.6 from the KLEVER (KMOS Lensed Emission Lines and VElocity Review) survey. Our sample covers an exceptionally wide range of stellar masses, 8.1 < log (M⋆/M⊙) < 11.3, pushing outflow studies into the dwarf regime thanks to gravitationally lensed objects. We stack optical rest-frame emission lines (H β, [O iii], H α, and [N ii]) in different mass bins and seek for tracers of gas outflows by using a novel, physically motivated method that improves over the widely used, simplistic double Gaussian fitting. We compare the observed emission lines with the expectations from a rotating disc (disc + bulge for the most massive galaxies) model, whereby significant deviations are interpreted as a signature of outflows. We find clear evidence for outflows in the most massive, log (M⋆/M⊙) > 10.8, AGN-dominated galaxies, suggesting that AGNs may be the primary drivers of these gas flows. Surprisingly, at log (M⋆/M⊙) ≤ 9.6, the observed line profiles are fully consistent with a rotating disc model, indicating that ionized gas outflows in dwarf galaxies might play a negligible role even during the peak of cosmic star-formation activity. Finally, we find that the observed mass loading factor scales with stellar mass as expected from the TNG50 cosmological simulation, but the ionized gas mass accounts for less than 2 ${{\ \rm per\ cent}}$ of the predicted value. This suggests that either the bulk of the outflowing mass is in other gaseous phases or the current feedback models implemented in cosmological simulations need to be revised.
The MAVERIC survey: a catalogue of radio sources in southern globular clusters from the Australia Telescope Compact Array
Authors: Tudor Vlad , Miller-Jones James C A , Strader Jay , Bahramian Arash , Shishkovsky Laura , Plotkin Richard M , Chomiuk Laura , Heinke Craig O , Maccarone Thomas J , Sivakoff Gregory R , Tremou Evangelia , Anderson Gemma E , Russell Thomas D , Tzioumis Anastasios K
Published: April 2022

Radio continuum observations offer a new window on compact objects in globular clusters compared to typical X-ray or optical studies. As part of the MAVERIC survey, we have used the Australia Telescope Compact Array to carry out a deep (median central noise level ≈4 $\mu$Jy beam-1) radio continuum survey of 26 southern globular clusters at central frequencies of 5.5 and 9.0 GHz. This paper presents a catalogue of 1285 radio continuum sources in the fields of these 26 clusters. Considering the surface density of background sources, we find significant evidence for a population of radio sources in seven of the 26 clusters, and also identify at least 11 previously known compact objects (six pulsars and five X-ray binaries). While the overall density of radio continuum sources with 7.25-GHz flux densities ≳ 20 $\mu$Jy in typical globular clusters is relatively low, the survey has already led to the discovery of several exciting compact binaries, including a candidate ultracompact black hole X-ray binary in 47 Tuc. Many of the unclassified radio sources near the centres of the clusters are likely to be true cluster sources, and multiwavelength follow-up will be necessary to classify these objects and better understand the demographics of accreting compact binaries in globular clusters.
Hydrodynamic simulations of electron-capture supernovae: progenitor and dimension dependence
Authors: Zha Shuai , O’Connor Evan P , Couch Sean M , Leung Shing-Chi , Nomoto Ken’ichi
Published: April 2022

We present neutrino-transport hydrodynamic simulations of electron-capture supernovae (ECSNe) in flash with new two-dimensional (2D) collapsing progenitor models. These progenitor models feature the 2D modelling of oxygen-flame propagation until the onset of core collapse. We perform axisymmetric simulations with six progenitor models that, at the time of collapse, span a range of propagating flame front radii. For comparison, we also perform a simulation with the same set-up using the canonical, spherically symmetrical progenitor model n8.8. We found that the variations in the progenitor models inherited from simulations of stellar evolution and flame propagation do not significantly alter the global properties of the neutrino-driven ECSN explosion, such as the explosion energy (∼1.36–1.48 × 1050 erg) and the mass (∼0.017–0.018 M⊙) and composition of the ejecta. Due to aspherical perturbations induced by the 2D flame, the ejecta contains a small amount (≲1.8 × 10−3 M⊙) of low-Ye (0.35 < Ye < 0.4) component. The baryonic mass of the protoneutron star is ∼1.34 M⊙ (∼1.357 M⊙) with the new (n8.8) progenitor models when simulations end at ∼400 ms and the discrepancy is due to updated weak-interaction rates in the progenitor evolutionary simulations. Our results reflect the nature of ECSN progenitors containing a strongly degenerate oxygen–neon–magnesium (ONeMg) core and suggest a standardized ECSN explosion initialized by ONeMg core collapse. Moreover, we carry out a rudimentary three-dimensional simulation and find that the explosion properties are fairly compatible with the 2D counterpart. Our paper facilitates a more thorough understanding of ECSN explosions following the ONeMg core collapse, though more three-dimensional simulations are still needed.
Climate uncertainties caused by unknown land distribution on habitable M-Earths
Authors: Macdonald Evelyn , Paradise Adiv , Menou Kristen , Lee Christopher
Published: April 2022

A planet’s surface conditions can significantly impact its climate and habitability. In this study, we use the 3D general circulation model exoplasim to systematically vary dayside land cover on a synchronously rotating, temperate rocky planet under two extreme and opposite continent configurations, in which either all of the land or all of the ocean is centred at the substellar point. We identify water vapour and sea ice as competing drivers of climate, and we isolate land-dependent regimes under which one or the other dominates. We find that the amount and configuration of land can change the planet’s globally averaged surface temperature by up to ∼20 K, and its atmospheric water vapour content by several orders of magnitude. The most discrepant models have partial dayside land cover with opposite continent configurations. Since transit spectroscopy may permit observations of M-dwarf planets’ atmospheres, but their surfaces will be difficult to observe, these land-related climate differences likely represent a limiting uncertainty in a given planet’s climate, even if its atmospheric composition is known. Our results are robust to variations in atmospheric CO2 concentration, stellar temperature, and instellation.
Four pulsar discoveries in NGC 6624 by TRAPUM using MeerKAT
Authors: Abbate F , Ridolfi A , Barr E D , Buchner S , Burgay M , Champion D J , Chen W , Freire P C C , Gautam T , Grießmeier J M , Künkel L , Kramer M , Padmanabh P V , Possenti A , Ransom S , Serylak M , Stappers B W , Venkatraman Krishnan V , Behrend J , Breton R P , Levin L , Men Y
Published: April 2022

We report four new pulsars discovered in the core-collapsed globular cluster (GC) NGC 6624 by the TRAPUM Large Survey Project with the MeerKAT telescope. All of the new pulsars found are isolated. PSR J1823−3021I and PSR J1823−3021K are millisecond pulsars with period of respectively 4.319 and 2.768 ms. PSR J1823−3021J is mildly recycled with a period of 20.899 ms, and PSR J1823−3022 is a long period pulsar with a period of 2.497 s. The pulsars J1823−3021I, J1823−3021J, and J1823−3021K have position and dispersion measure (DM) compatible with being members of the GC and are therefore associated with NGC 6624. Pulsar J1823−3022 is the only pulsar bright enough to be re-detected in archival observations of the cluster. This allowed the determination of a timing solution that spans over two decades. It is not possible at the moment to claim the association of pulsar J1823−3022 with the GC given the long period and large offset in position (∼3 arcmin) and DM (with a fractional difference of 11 percent compared the average of the pulsars in NGC 6624). The discoveries made use of the beamforming capability of the TRAPUM backend to generate multiple beams in the same field of view which allows sensitive searches to be performed over a few half-light radii from the cluster centre and can simultaneously localize the discoveries. The discoveries reflect the properties expected for pulsars in core-collapsed GCs.
Hybrid photometric redshifts for sources in the COSMOS and XMM-LSS fields
Authors: Hatfield P W , Jarvis M J , Adams N , Bowler R A A , Häußler B , Duncan K J
Published: April 2022

In this paper, we present photometric redshifts for 2.7 million galaxies in the XMM-LSS and COSMOS fields, both with rich optical and near-infrared data from VISTA and HyperSuprimeCam. Both template fitting (using galaxy and active galactic nuclei templates within LePhare) and machine learning (using gpz) methods are run on the aperture photometry of sources selected in the Ks-band. The resulting predictions are then combined using a Hierarchical Bayesian model, to produce consensus photometric redshift point estimates and probability distribution functions that outperform each method individually. Our point estimates have a root mean square error of ∼0.08–0.09, and an outlier fraction of ∼3–4 percent when compared to spectroscopic redshifts. We also compare our results to the COSMOS2020 photometric redshifts, which contain fewer sources, but had access to a larger number of bands and greater wavelength coverage, finding that comparable photo-z quality can be achieved (for bright and intermediate luminosity sources where a direct comparison can be made). Our resulting redshifts represent the most accurate set of photometric redshifts (for a catalogue this large) for these deep multisquare degree multiwavelength fields to date.
The Quasar Feedback Survey: revealing the interplay of jets, winds, and emission-line gas in type 2 quasars with radio polarization
Authors: Silpa S , Kharb P , Harrison C M , Girdhar A , Mukherjee D , Mainieri V , Jarvis M E
Published: April 2022

We present results from a combined radio polarization and emission-line study of five type 2 quasars at z < 0.2 with the Karl G. Jansky Very Large Array (VLA) B-array at 5 GHz and Hubble Space Telescope (HST) [O iii] observations. These five sources are known to exhibit close association between radio structures and ionized gas morphology and kinematics. Four sources (J0945+1737, J1000+1242, J1356+1026, and J1430+1339) show polarization in the current data. J1010+1413 is the unpolarized source in our sample. We detect $0.5{-}1{{\ \rm per\ cent}}$ fractional polarization in the radio cores and a high fractional polarization ($10{-}30{{\ \rm per\ cent}}$) in the lobes of these sources. The morphological, spectral, and polarization properties suggest a jet origin for radio emission in J0945+1737, J1000+1242, J1010+1413, and J1430+1339 whereas the current data cannot fully discern the origin of radio emission (jet or wind) in J1356+1026. An anticorrelation between various polarized knots in the radio and [O iii] emission is observed in our sources, similar to that observed in some radio-loud AGN in the literature. This suggests that the radio emission is likely to be depolarized by the emission-line gas. By modelling the depolarization effects, we estimate the size of the emission-line gas clouds to be ∼(2.8 ± 1.7) × 10−5 parsec and the amount of thermal material mixed with the synchrotron plasma to be ∼(1.01 ± 0.08) × 106 M⊙ in the lobe of J0945+1737 (which exhibits the most prominent polarization signature in its lobe). The current work demonstrates that the interplay of jets/winds and emission-line gas is most likely responsible for the nature of radio outflows in radio-quiet AGN.
The detection efficiency of Type Ia supernovae from the Zwicky Transient Facility: limits on the intrinsic rate of early flux excesses
Authors: Magee M R , Cuddy C , Maguire K , Deckers M , Dhawan S , Frohmaier C , Miller A A , Nordin J , Coughlin M W , Feinstein F , Riddle R
Published: April 2022

Samples of young Type Ia supernovae have shown ‘early excess’ emission in a few cases. Similar excesses are predicted by some explosion and progenitor scenarios and hence can provide important clues regarding the origin of thermonuclear supernovae. They are, however, only predicted to last up to the first few days following explosion. It is therefore unclear whether such scenarios are intrinsically rare or whether the relatively small sample size simply reflects the difficulty in obtaining sufficiently early detections. To that end, we perform toy simulations covering a range of survey depths and cadences, and investigate the efficiency with which young Type Ia supernovae are recovered. As input for our simulations, we use models that broadly cover the range of predicted luminosities. Based on our simulations, we find that in a typical 3 d cadence survey, only ∼10 per cent of Type Ia supernovae would be detected early enough to rule out the presence of an excess. A 2 d cadence, however, should see this increase to ∼15 per cent. We find comparable results from more detailed simulations of the Zwicky Transient Facility surveys. Using the recovery efficiencies from these detailed simulations, we investigate the number of young Type Ia supernovae expected to be discovered assuming some fraction of the population comes from scenarios producing an excess at early times. Comparing the results of our simulations to observations, we find that the intrinsic fraction of Type Ia supernovae with early flux excesses is $\sim 28^{+13}_{-11}{{\ \rm per\ cent}}$.
The evolution of the high-frequency variability in the black hole candidate GRS 1915+105 as seen by RXTE
Authors: Zhang Yuexin , Méndez Mariano , García Federico , Karpouzas Konstantinos , Zhang Liang , Liu Honghui , Belloni Tomaso M , Altamirano Diego
Published: April 2022

GRS 1915+105 can show type-C quasi-periodic oscillations (QPOs) in the power density spectrum. A high-frequency QPO (HFQPO) at 67 Hz has been observed in this source, albeit less often than the type-C QPOs. Besides these features, GRS 1915+105 sometimes shows a broad bump in the power spectrum at around 30–150 Hz. We study the power spectra of GRS 1915+105 with the Rossi X-ray Timing Explorer when the source was in the χ class. We find that the rms amplitude of the bump depends strongly upon both the frequency of the type-C QPO and the hardness ratio, and is correlated with the corona temperature and anticorrelated with the radio flux at 15 GHz. The characteristic frequency of the bump is better correlated with a combination of the frequency of the type-C QPO and the hardness ratio than with the frequency of the type-C QPO alone. The rms amplitude of the bump generally increases with energy from ∼1–2 per cent at ∼3 keV to ∼10–15 per cent at ∼30 keV. We suggest that the bump and the HFQPO may be the same variability component but the properties of the corona affect the coherence of this variability, leading either to a HFQPO when the spectrum is in the relatively soft γ class, or to a bump when the spectrum is in the hard χ class. Finally, we discuss the anticorrelation between the rms amplitude of the bump and the radio flux in the context of the relation between the corona and the jet.
The annual cycle in scintillation time-scale of PMN J1726+0639
Authors: Bignall Hayley E , Tuntsov Artem V , Stevens Jamie , Bannister Keith , Walker Mark A , Reynolds Cormac
Published: April 2022

We discovered rapid intra-day variability in radio source PMN J1726+0639 at GHz frequencies, during a survey to search for such variability with the Australia Telescope Compact Array. Follow-up observations were conducted over 2 yr and revealed a clear, repeating annual cycle in the rate, or characteristic time-scale, of variability, showing that the observed variations can be attributed to scintillations from interstellar plasma inhomogeneities. The strong annual cycle includes an apparent ‘standstill’ in April and another in September. We fit kinematic models to the data, allowing for finite anisotropy in the scintillation pattern. The cycle implies a very high degree of anisotropy, with an axial ratio of at least 13:1, and the fit is consistent with a purely one-dimensional scintillation pattern. The position angle of the anisotropy, and the transverse velocity component are tightly constrained. The parameters are inconsistent with expectations from a previously proposed model of scattering associated with plasma filaments radially oriented around hot stars. We note that evidence for a foreground interstellar cloud causing anomalous Ca ii absorption towards the nearby star Rasalhague (α Oph) has been previously reported, and we speculate that the interstellar scintillation of PMN J1726+0639 might be associated with this nearby cloud.
The physical origin of dark energy constraints from rubin observatory and CMB-S4 lensing tomography
Authors: Yu Byeonghee , Ferraro Simone , Knight Z Robert , Knox Lloyd , Sherwin Blake D
Published: April 2022

We seek to clarify the origin of constraints on the dark energy equation of state parameter from CMB lensing tomography, that is the combination of galaxy clustering and the cross-correlation of galaxies with CMB lensing in a number of redshift bins. We focus on the analytic understanding of the origin of the constraints. Dark energy information in these data arises from the influence of three primary relationships: distance as a function of redshift (geometry), the amplitude of the power spectrum as a function of redshift (growth), and the power spectrum as a function of wavenumber (shape). We find that the effects from geometry and growth play a significant role and partially cancel each other out, while the shape effect is unimportant. We also show that Dark Energy Task Force figure of merit forecasts from the combination of LSST galaxies and CMB-S4 lensing are comparable to the forecasts from cosmic shear in the absence of the CMB lensing map, thus providing an important independent check. Compared to the forecasts with the LSST galaxies alone, combining CMB lensing and LSST clustering information increases the FoM by roughly a factor of 3–4 in the optimistic scenario where systematics are fully under control. We caution that achieving these forecasts will likely require a full analysis of higher-order biasing, photometric redshift uncertainties, and stringent control of other systematic limitations, which are outside the scope of this work, whose primary purpose is to elucidate the physical origin of the constraints.
Comparing implementations of self-interacting dark matter in the gizmo and arepo codes
Authors: Meskhidze Helen , Mercado Francisco J , Sameie Omid , Robles Victor H , Bullock James S , Kaplinghat Manoj , Weatherall James O
Published: April 2022

Self-interacting dark matter (SIDM) models have received great attention over the past decade as solutions to the small-scale puzzles of astrophysics. Though there are different implementations of dark matter (DM) self-interactions in N-body codes of structure formation, there has not been a systematic study to compare the predictions of these different implementations. We investigate the implementation of dark matter self-interactions in two simulation codes:gizmo and arepo. We begin with identical initial conditions for an isolated 1010 M⊙ dark matter halo and investigate the evolution of the density and velocity dispersion profiles in gizmo and arepo for SIDM cross-section over mass of 1, 5, and 50 $\rm cm^2\, g^{-1}$. Our tests are restricted to the core expansion phase, where the core density decreases and core radius increases with time. We find better than 30 per cent agreement between the codes for the density profile in this phase of evolution, with the agreement improving at higher resolution. We find that varying code-specific SIDM parameters changes the central halo density by less than 10 per cent outside of the convergence radius. We argue that SIDM core formation is robust across the two different schemes and conclude that these codes can reliably differentiate between cross-sections of 1, 5, and 50 $\rm cm^2\, g^{-1}$, but finer distinctions would require further investigation.
Ejection–accretion connection in NLS1 AGN 1H 1934-063
Authors: Xu Y , Pinto C , Kara E , Masterson M , García J A , Fabian A C , Parker M L , Barret D , Alston W N , Cusumano G
Published: April 2022

Accretion and ejection of matter in active galactic nuclei (AGNs) are tightly connected phenomena and represent fundamental mechanisms regulating the growth of the central supermassive black hole and the evolution of the host galaxy. However, the exact physical processes involved are not yet fully understood. We present a high-resolution spectral analysis of a simultaneous XMM–Newton and NuSTAR observation of the narrow line Seyfert 1 (NLS1) AGN 1H 1934-063, during which the X-ray flux dropped by a factor of ∼6 and subsequently recovered within 140 kiloseconds. By means of the time-resolved and flux-resolved X-ray spectroscopy, we discover a potentially variable warm absorber and a relatively stable ultra-fast outflow (UFO, $v_\mathrm{UFO}\sim -0.075\, c$) with a mild ionization state ($\log (\xi /\mathrm{erg\, cm\, s^{-1})}\sim 1.6$). The detected emission lines (especially a strong and broad feature around 1 keV) are of unknown origin and cannot be explained with emission from plasmas in photo- or collisional-ionization equilibrium. Such emission lines could be well described by a strongly blueshifted (z ∼ −0.3) secondary reflection off the base of the equatorial outflows, which may reveal the link between the reprocessing of the inner accretion flow photons and the ejection. However, this scenario although being very promising is only tentative and will be tested with future observations.
The absence of periodicity in repeating FRB
Authors: Katz J I
Published: April 2022

Popular fast radio burst (FRB) models involve rotating magnetized neutron stars, yet no rotational periodicities have been found. Small data sets exclude exact periodicity in FRB 121102. Recent observations of over 1500 bursts from each of FRB 121102 and FRB 20201124A have also not found periodicity. Periodograms of events with cosine-distributed random offsets as large as ±0.6P from a strict period P would still reveal the underlying periodicity. The sensitivity of periodograms of long data series, such as bursts observed on multiple days, to slow frequency drifts is mitigated by considering individual observing sessions, and results are shown for FRB 121102. Models of repeating FRB without intrinsic periodicity are considered, as are models of apparently non-repeating FRBs.
The contribution of non-central radio galaxies to AGN feedback in rich galaxy clusters
Authors: Seth Ruchika , O’Sullivan Ewan , Sebastian Biny , Raychaudhury Somak , Schellenberger Gerrit , Haines Christopher P
Published: April 2022

We present a combined radio/X-ray study of six massive galaxy clusters, aimed at determining the potential for heating of the intra-cluster medium (ICM) by non-central radio galaxies. Since X-ray cavities associated with the radio lobes of non-central galaxies are generally not detectable, we use Giant Metrewave Radio Telescope 610 MHz observations to identify jet sources and estimate their size, and Chandra data to estimate the pressure of the surrounding ICM. In the radio, we detect 4.5 per cent of galaxies above the spectroscopic survey limit (M$^{*}_{K}$ + 2.0) of the Arizona cluster redshift survey (ACReS) that covers five of our six clusters. Approximately one-tenth of these are extended radio sources. Using star formation (SF) rates determined from mid-infrared data, we estimate the expected contribution to radio luminosity from the stellar population of each galaxy, and find that most of the unresolved or poorly resolved radio sources are likely SF dominated. The relatively low frequency and good spatial resolution of our radio data allows us to trace SF emission down to galaxies of stellar mass ∼10 9.5 M⊙. We estimate the enthalpy of the (AGN-dominated) jet/lobe and tailed sources, and place limits on the energy available from unresolved radio jets. We find jet powers in the range ∼1043 to 1046 erg s−1, comparable to those of brightest cluster galaxies. Our results suggest that while cluster-central sources are the dominant factor balancing ICM cooling over the long-term, non-central sources may have a significant impact, and that further investigation is possible and warranted.
Probing the Galactic halo with RR Lyrae stars – II. The substructures of the Milky Way
Authors: Wang F , Zhang H-W , Xue X-X , Huang Y , Liu G-C , Zhang L , Yang C-Q
Published: April 2022

We identify substructures of the Galactic halo using 3003 type ab RR Lyrae stars with six-dimensional position–velocity information from the Sloan Digital Sky Survey, the Large Sky Area Multi-Object Fiber Spectroscopic Telescope and the Gaia Early Data Release 3. Based on this information, we define the separation of any two of the stars in the integrals of motion space and we identify substructures by utilizing the friends-of-friends algorithm. We identify members belonging to several known substructures: the Sagittarius stream, the Gaia-Enceladus-Sausage (GES), the Sequoia and the Helmi streams. In addition to these known substructures, there are three other substructures possibly associated with globular clusters NGC 5272, 6656 and 5024, respectively. Finally, we also find three remaining unknown substructures, one of which has large angular momentum and a mean metallicity −2.13 dex, which may be a new substructure. As for the GES, we find that it accounts for a large part of substructures in the inner halo and the apocentre distance is in the range 10–34 kpc, which suggests that the GES is mainly distributed in the inner halo. The near one-third proportion of the GES and the peak value of 20 kpc of the apocentre distance suggest that the GES could account for the break in the density profile of the Galactic halo at the Galactocentric distance ~20–25 kpc. The similarity when comparing the kinematic properties of the GES with the Hercules–Aquila Cloud and Virgo Overdensity suggests that the three substructures may have similar origins.
Kinetic simulation of electron, proton and helium acceleration in a non-relativistic quasi-parallel shock
Authors: Fang Jun , Xia Qi , Tian Shiting , Zhou Liancheng , Yu Huan
Published: April 2022

In addition to accelerating electrons and protons, non-relativistic quasi-parallel shocks are expected to possess the ability to accelerate heavy ions. The shocks in supernova remnants are generally supposed to be accelerators of Galactic cosmic rays, which consist of many species of particles. We investigate the diffusive shock acceleration of electrons, protons and helium ions in a non-relativistic quasi-parallel shock through a 1D particle-in-cell simulation with a helium-to-proton number density ratio of 0.1, which is relevant for Galactic cosmic rays. The simulation indicates that waves can be excited by the flow of energetic protons and helium ions upstream of a non-relativistic quasi-parallel shock with a sonic Mach number of 14 and an Alfvén Mach number of 19.5 in the shock rest frame, and that the charged particles are scattered by the self-generated waves and accelerated gradually. Moreover, the spectra of the charged particles downstream of the shock are thermal with a non-thermal tail, and the acceleration is efficient, with about $7{{\ \rm per\ cent}}$ and $5.4{{\ \rm per\ cent}}$ of the bulk kinetic energy transferred into the non-thermal protons and helium ions, respectively, in the near downstream region by the end of the simulation.
Temporal and spectral study of PKS 0208−512 during the 2019–2020 flare
Authors: Khatoon Rukaiya , Prince Raj , Shah Zahir , Sahayanathan Sunder , Gogoi Rupjyoti
Published: April 2022

We present a temporal and spectral study of the blazar PKS 0208−512, using recent flaring activity from 2019 November to 2020 May, as detected by the Fermi Large Area Telescope. The contemporaneous X-ray and optical/ultraviolet observations from theSwift X-Ray Telescope and UltraViolet and Optical Telescope are also used. During the activity state, the 2-d binned γ-ray light curve shows multiple peaks indicating subflares. To understand the possible physical mechanisms behind flux enhancement, we divided the activity state of the source into several flux states and carried out detailed temporal and spectral studies. The timing analysis of light curves suggests that peaks of subflares have rise and decay times of the order of days, with the flux doubling time ∼ 2 d. The 2-d binned γ-ray light curve shows double-lognormal flux distribution. The broad-band spectral energy distribution (SED) for three selected flux states can be well fitted under synchrotron, synchrotron self-Compton and external Compton emission mechanisms. We obtained the physical parameters of the jet by SED modelling and their confidence intervals through χ2-statistics. Our SED modelling results suggest that during the quiescent state, the γ-ray spectrum can be explained by considering the external Compton scattering of infrared photons from the dusty torus. However, γ-ray spectra corresponding to flares demand additional target photons from the broad-line region (BLR) along with infrared. These suggest that, during flares, the emission region is close to the edge of the BLR, while for the quiescent state, the emission region is away from the BLR. The best-fitting results suggest that a marginal increase in the magnetic field during the flaring episode can result in flux enhancement. This is possibly associated with the efficiency of particle acceleration during flaring states compared with the quiescent state.
On the physical nature of the Wilson–Bappu effect: revising the gravity and temperature dependence
Authors: Rosas-Portilla F , Schröder K -P , Jack D
Published: April 2022

We present a sample of 32 stars of spectral types G and K and luminosity classes I–V, with moderate activity levels, covering four orders of magnitude of surface gravity and a representative range of effective temperature. For each star we obtained high signal-to-noise ratio (S/N) spectra from the Telescopio Internacional de Guanajuato Robótico-Espectroscópico (TIGRE–HEROS) with a spectral resolving power of $R\approx 20\, 000$ and measured the Ca ii K line widths of interest, W0 and W1. The main physical parameters are determined by means of iSpec synthesis and Gaia EDR3 parallaxes. Mass estimates are based on matching to evolution models. Using this stellar sample, which is highly uniform in terms of spectral quality and assessment, we derive the best-fitting relation between emission-line width and gravity g, including a notable dependence on effective temperature Teff, of the form $W_1 \propto g^{-0.229} T_{\rm eff}^{+2.41}$. This result confirms the physical interpretation of the Wilson–Bappu effect as a line saturation and photon redistribution effect in the chromospheric Ca ii column density, under the assumption of hydrostatic equilibrium at the bottom of the chromosphere. While the column density (and hence W1) increases towards lower gravities, the observed temperature dependence is then understood as a simple ionization effect: in cooler stars, Ca ii densities decrease in favour of Ca i.
Pushchino multibeam pulsar search – II. Long-term variability of rotating radio transients
Authors: Smirnova T V , Tyul’bashev S A , Brylyakova E A , Kitaeva M A , Chashei I V , Tyul’basheva G E , Oreshko V V , Logvinenko S V
Published: April 2022

Pulses from 16 previously known rotating radio transients (RRATs) have been searched for with the 111 MHz daily monitoring program for 4 to 5.5 yr using the Large Phased Array (LPA) at Pushchino. The total number of pulses detected in such a long observation interval is only 90 for RRAT J0640+07, but is as high as 10 751 for RRAT J0302+22. The number and amplitude of pulses vary on time-scales from 6 to 20 months for RRATs J1336+33, J1404+11, J1848+15, J2051+12 and J2105+22, and the pulse number can increase by one or two orders of magnitude in active phases. Long-term trends are found for RRATs J0139+33 and J0302+22, which show a 2–3 times increase in detected pulse number over 1959 d. Some RRATs show annual variations in both pulse number and pulse amplitude. It is hard to explain all these variation time-scales by refractive scintillation on the interstellar medium. The annual and semi-annual variations are probably caused by scintillations on the inhomogeneous interplanetary plasma. Our data show that the number of observational sessions with no pulse detection over the threshold decreases exponentially with the length of pulse silence.
Astrometric identification of nearby binary stars – I. Predicted astrometric signals
Authors: Penoyre Zephyr , Belokurov Vasily , Evans N Wyn
Published: April 2022

We examine the capacity to identify binary systems from astrometric errors and deviations alone. Until the release of the fourth Gaia data release, we lack the full astrometric time-series that the satellite records, but as we show can still infer the presence of binaries from the best-fitting models, and their error, already available. We generate a broad catalogue of simulated binary systems within 100 pc, and examine synthetic observations matching the Gaia survey’s scanning law and astrometric data processing routine. We show how the unit weight error (UWE) and proper motion anomaly (PMA) vary as a function of period, and the properties of the binary. Both UWE and PMA peak for systems with a binary period close to the time baseline of the survey. Thus UWE can be expected to increase or remain roughly constant as we observe the same system over a longer baseline, and we suggest UWEeDR3 > 1.25 and ΔUWE/UWEeDR3 > −0.25 as criteria to select astrometric binaries. For stellar binaries, we find detectable significant astrometric deviations for 80–90 per cent of our simulated systems in a period range from months to decades. We confirm that for systems with periods less than the survey’s baseline the observed UWE scales ∝ ϖ (parallax), a (semimajor axis), and $\Delta =\frac{|q-l|}{(1+q)(1+l)}$, where q and l are the mass and light ratio, respectively, with a modest dependence on viewing angle. For longer periods the signal is suppressed by a factor of roughly ∝P−2 (period). PMA is largest in orbits with slightly longer periods but obeys the same approximate scaling relationships.
Amplified J-factors in the Galactic Centre for velocity-dependent dark matter annihilation in FIRE simulations
Authors: McKeown Daniel , Bullock James S , Mercado Francisco J , Hafen Zachary , Boylan-Kolchin Michael , Wetzel Andrew , Necib Lina , Hopkins Philip F , Yu Sijie
Published: April 2022

We use FIRE-2 zoom cosmological simulations of Milky Way size Galaxy haloes to calculate astrophysical J-factors for dark matter annihilation and indirect detection studies. In addition to velocity-independent (s-wave) annihilation cross-sections 〈σv〉, we also calculate effective J-factors for velocity-dependent models, where the annihilation cross-section is either p-wave (∝ v2/c2) or d-wave (∝ v4/c4). We use 12 pairs of simulations, each run with dark matter-only (DMO) physics and FIRE-2 physics. We observe FIRE runs produce central dark matter velocity dispersions that are systematically larger than in DMO runs by factors of ∼2.5–4. They also have a larger range of central (∼400 pc) dark matter densities than the DMO runs (ρFIRE/ρDMO ≃ 0.5–3) owing to the competing effects of baryonic contraction and feedback. At 3 deg from the Galactic Centre, FIRE J-factors are 3–60 (p-wave) and 10–500 (d-wave) times higher than in the DMO runs. The change in s-wave signal at 3 deg is more modest and can be higher or lower (∼0.3–7), though the shape of the emission profile is flatter (less peaked towards the Galactic Centre) and more circular on the sky in FIRE runs. Our results for s-wave are broadly consistent with the range of assumptions in most indirect detection studies. We observe p-wave J-factors that are significantly enhanced compared to most past estimates. We find that thermal models with p-wave annihilation may be within range of detection in the near future.
Discovery of cyclotron and narrow Fe Kα lines in HMXB GRO J1750–27
Authors: Sharma Prince , Jain Chetana , Dutta Anjan
Published: April 2022

We report on the timing and spectral analysis of transient Be X-ray pulsar GRO J1750–27 using the Nuclear Spectroscopic Telescope Array(NuSTAR) observation from 2021 September. This is the fourth outburst of the system since 1995. The NuSTAR observation was performed during the rising phase of the outburst. Pulsations at a period of 4.450710(1) s were observed in the 3–60 keV energy range. The average pulse profile comprised of a broad peak with a weak secondary peak, which evolved with energy. We did not find any appreciable variation in the X-ray emission during this observation. The broad-band phase-averaged spectrum is described by a blackbody, a power law, or Comptonization component. We report the discovery of Fe Kα line at 6.4 keV, along with the presence of two cyclotron resonant scattering features of around 36 and 42 keV. These lines indicate a magnetic field with the strength of $3.7_{-0.3}^{+0.1} \times 10^{12}$ and 4.4 ± 0.10 × 1012 G for the neutron star. We have estimated a source distance of ∼13.6–16.4 kpc based on the accretion-disc torque models.
The Holy and the God-Loved: The Dilemma in Plato’sEuthyphro
Authors: Frede Dorothea
Published: April 2022

Is the holy holy because the gods love it or do the gods love it because it is holy? On the basis of this dilemma Plato works out the manifold and complex relationship between God and Morality in his dialogue Euthyphro. This dialogue not only plays a central role within Plato’s work on the question of the relationship between ethics and religion, but it also represents the starting point of the entire further Western debate about God and Morality. This article gives a basic interpretation of the text, situates the dilemma within the dialogue, traces its character, intention, and structure, unfolds the course of the argument, and offers a brief outlook on its reception.
St. Anselm of Canterbury on God and Morality
Authors: Rogers Katherin
Published: April 2022

Anselm of Canterbury, as a classical theist, does not hold that there is a moral, or value, order independent of God. What is good, indeed what is necessary and possible, depends on the will of God. But Anselm’s development of this claim does not succumb to the problems entailed by divine-command theory. One such problem addresses the question of whether or not the moral order is available to reason, bracketing Scripture and Church teaching. Anselm holds that to be just is to conform to God’s will. Nevertheless Anselm proposes a eudaimonistic ethical theory that allows reason to assess moral principles. And Anselm holds that the non-believer recognizes justice, even before he can appreciate the more general category of “good.”
Mismatch discrimination and sequence bias during end-joining by DNA ligases
Authors: Bilotti Katharina , Potapov Vladimir , Pryor John M , Duckworth Alexander T , Keck James L , Lohman Gregory J S
Published: April 2022

DNA ligases, critical enzymes for in vivo genome maintenance and modern molecular biology, catalyze the joining of adjacent 3′-OH and 5′-phosphorylated ends in DNA. To determine whether DNA annealing equilibria or properties intrinsic to the DNA ligase enzyme impact end-joining ligation outcomes, we used a highly multiplexed, sequencing-based assay to profile mismatch discrimination and sequence bias for several ligases capable of efficient end-joining. Our data reveal a spectrum of fidelity and bias, influenced by both the strength of overhang annealing as well as sequence preferences and mismatch tolerances that vary both in degree and kind between ligases. For example, while T7 DNA ligase shows a strong preference for ligating high GC sequences, other ligases show little GC-dependent bias, with human DNA Ligase 3 showing almost none. Similarly, mismatch tolerance varies widely among ligases, and while all ligases tested were most permissive of G:T mismatches, some ligases also tolerated bulkier purine:purine mismatches. These comprehensive fidelity and bias profiles provide insight into the biology of end-joining reactions and highlight the importance of ligase choice in application design.
A molecular beacon assay for monitoring RNA splicing
Authors: Omran Qusay Q , Fedorova Olga , Liu Tianshuo , Pyle Anna M
Published: April 2022

Small molecule targeting of self-splicing RNAs like group I and II introns has been limited in part by the lack of a universal high-throughput screening platform for studies of splicing inhibition and kinetics. Here, we present the development of a molecular beacon assay for monitoring the accumulation of spliced exons during RNA splicing reactions. In this case, we applied it to the autocatalyzed reaction of the H.c.LSU group II intron found in the mitochondria of the pathogenic dimorphic fungus Histoplasma capsulatum. We find that a molecular beacon with the loop length of 18 nucleotides selectively recognizes ligated exons formed during self-splicing and exhibits high fluorescent signal upon binding of its target. We demonstrate that the fluorescent assay using molecular beacons can be successfully applied to kinetic characterization of the splicing reaction and determination of inhibition constants for small molecules. The results presented herein offer support for a molecular beacon approach to identifying small molecule inhibitors of intron splicing.
LOMETS3: integrating deep learning and profile alignment for advanced protein template recognition and function annotation
Authors: Zheng Wei , Wuyun Qiqige , Zhou Xiaogen , Li Yang , Freddolino Lydia , Zhang Yang
Published: April 2022

Deep learning techniques have significantly advanced the field of protein structure prediction. LOMETS3 (https://zhanglab.ccmb.med.umich.edu/LOMETS/) is a new generation meta-server approach to template-based protein structure prediction and function annotation, which integrates newly developed deep learning threading methods. For the first time, we have extended LOMETS3 to handle multi-domain proteins and to construct full-length models with gradient-based optimizations. Starting from a FASTA-formatted sequence, LOMETS3 performs four steps of domain boundary prediction, domain-level template identification, full-length template/model assembly and structure-based function prediction. The output of LOMETS3 contains (i) top-ranked templates from LOMETS3 and its component threading programs, (ii) up to 5 full-length structure models constructed by L-BFGS (limited-memory Broyden–Fletcher–Goldfarb–Shanno algorithm) optimization, (iii) the 10 closest Protein Data Bank (PDB) structures to the target, (iv) structure-based functional predictions, (v) domain partition and assembly results, and (vi) the domain-level threading results, including items (i)–(iii) for each identified domain. LOMETS3 was tested in large-scale benchmarks and the blind CASP14 (14th Critical Assessment of Structure Prediction) experiment, where the overall template recognition and function prediction accuracy is significantly beyond its predecessors and other state-of-the-art threading approaches, especially for hard targets without homologous templates in the PDB. Based on the improved developments, LOMETS3 should help significantly advance the capability of broader biomedical community for template-based protein structure and function modelling.