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Clusters of galaxies are merging during the formation of large-scale structures in the Universe. Based on optical survey data, we identify a large sample of pre-mergers of galaxy clusters and merging subclusters in rich clusters. We find 39 382 partners within a velocity difference of 1500 km s |$^{-1}$| and a projected separation of 5  |$r_{500}$| around 33 126 main clusters, where |$r_{500}$| is the radius of the main cluster. Based on the galaxy distribution inside rich clusters with more than 30 member galaxy candidates, we identify subclusters by modelling the smoothed optical distribution with a two-component profile, and a coupling factor is obtained for merging subclusters in 7845 clusters. In addition, we find 3446 post-collision mergers according to the deviations of brightest cluster galaxies from other member galaxies, most of which have been partially validated by using the Chandra and XMM–Newton X-ray images. Two new bullet-like clusters have been identified by using the optical and X-ray images. The large samples of merging clusters of galaxies presented here are important databases for studying the hierarchical structure formation, cluster evolution, and the physics of intergalactic medium. [ABSTRACT FROM AUTHOR]

Double neutron star (DNS) systems offer excellent opportunities to test gravity theories. We report the timing results of PSR J1901+0658, the first pulsar discovered in the FAST Galactic Plane Pulsar Snapshot (GPPS) Survey. Based on timing observations by FAST over 5 yr, we obtain the phase-coherent timing solution and derive the precise measurements of its position, spin parameters, orbital parameters, and dispersion measure. It has a period of 75.7 ms, a period derivative of 2.169(6) × 10−19 s s−1, and a characteristic age of 5.5 Gyr. This pulsar is in an orbit with a period of 14.45 d and an eccentricity of 0.366. One post-Keplerian parameter, periastron advance, has been well-measured as being 0.00531(9) deg yr−1, from which the total mass of this system is derived to be 2.79(7) M⊙. The pulsar has the mass upper limit of 1.68 M⊙, so the lower limit for the companion mass is 1.11 M⊙. Because PSR J1901+0658 is a partially recycled pulsar in an eccentric binary orbit with such a large companion mass, it should be in a DNS system according to the evolution history of the binary system. [ABSTRACT FROM AUTHOR]

The individual subpulses of pulsars are regarded as their basic emission components, providing invaluable information for our understanding of the radio emission process in the pulsar magnetosphere. Nevertheless, subpulses are overlapped with each other along the rotation phase for most pulsars, making it difficult to study the statistical properties of subpulses. Among the pulsars observed by the Five-hundred-meter Aperture Spherical radio Telescope (FAST), PSR B1916+14 has a large number of isolated well-resolved subpulses in the high-time-resolution observations, having a typical width of 0.15 ms and a high linear polarization. We find that the number distribution of subpulses contributes dominantly to the mean profile. According to the emission geometry, these emission units come from a region roughly 155 km above the polar cap in the pulsar magnetosphere, and the length-scale of the basic emission units is approximately 120 m. The deviations of the polarization position angles for these single subpulses from the standard S-shaped curve are closely related to their fractional linear and circular polarization, and the large deviations tend to come from drifting subpulses. [ABSTRACT FROM AUTHOR]

G213.0−0.6 is a faint extended source situated in the anticentre region of the Galactic plane. It has been classified as a shell-type supernova remnant (SNR) based on its shell-like morphology, steep radio continuum spectrum, and high ratio of [S  ii ]/Hα. With new optical emission line data of Hα, [S  ii ], and [N  ii ] recently observed by the Large Sky Area Multi-Object Fiber Spectroscopic Telescope, the ratios of [S  ii ]/Hα and [N  ii ]/Hα are re-assessed. The lower values than those previously reported put G213.0−0.6 around the borderline of SNR-H  ii region classification. We decompose the steep-spectrum synchrotron and the flat-spectrum thermal free-free emission in the area of G213.0−0.6 with multi-frequency radio continuum data. G213.0−0.6 is found to show a flat spectrum, in conflict with the properties of a shell-type SNR. Such a result is further confirmed by TT-plots made between the 863-MHz, 1.4-GHz, and 4.8-GHz data. Combining the evidence extracted in both optical and radio continuum, we argue that G213.0−0.6 is possibly not an SNR, but an H  ii region instead. The V LSR pertaining to the Hα filaments places G213.0−0.6 approximately 1.9 kpc away in the Perseus Arm. [ABSTRACT FROM AUTHOR]

During observations of the Galactic Plane Pulsar Snapshot survey by the Five-hundred-meter Aperture Spherical radio Telescope, varying subpulse drifting of PSR J1857+0057 is detected. The follow-up observation confirms the quasi-regular changes of the drifting rate about every 50 periods. We determine the drift rate D through a linear fit to the pulse-central longitudes of subpulses in a drifting band, and determine P 3 from the cross-points of two fitted lines at the zero longitude for two neighbouring drifting bands. The low frequency modulation of about every 50 periods is found on variations of not only pulse intensity but also drift parameters. In most of low frequency modulation cycles, the integrated pulse intensity I and the absolute drift rate | D | tend to increase first and then decrease, and the drifting periodicity P 3 varies just in the opposite. In addition, the phase-forward intensity-enhancement is observed in many modulation cycles. Based on our polarization data, the average position angle curve for pulses with a smaller | D | and larger P 3 is slightly steep in the leading edge of pulse profile compared with that of the fully averaged profile. [ABSTRACT FROM AUTHOR]

We report five new fast radio bursts (FRBs) discovered from the Galactic Plane Pulsar Snapshot (GPPS) survey by the Five-hundred-meter Aperture Spherical radio Telescope (FAST): FRB 20210126, FRB 20210208, FRB 20210705, FRB 20211005, and FRB 20220306. To date, no repeating bursts from these FRB sources have been detected in the follow-up monitoring observations, leading to their classification as potential one-off events. We obtain the basic parameters for these bursts, including position, dispersion measure, pulse width, spectral index, scattering time-scale, etc. The fluences and flux densities are generally lower in comparison to the values observed in one-off bursts discovered by other telescopes. Among the observed bursts, polarization data for four bursts were recorded during observations. Consequently, we obtain polarization profiles and Faraday rotation measures for these bursts. [ABSTRACT FROM AUTHOR]

Timing observations are crucial for determining the basic parameters of newly discovered pulsars. Using the Five-hundred-meter Aperture Spherical radio Telescope (FAST) with the L-band 19-beam receiver covering the frequency range of 1.0–1.5 GHz, the FAST Galactic Plane Pulsar Snapshot (GPPS) Survey has discovered more than 600 faint pulsars with flux densities of only a few or a few tens of μJy at 1.25 GHz. To obtain accurate position, spin parameters and dispersion measure of a pulsar, and to calculate derived parameters such as the characteristic age and surface magnetic field, we collect available FAST pulsar data obtained either through targeted follow-up observations or through coincidental survey observations with one of the 19 beams of the receiver. From these data we obtain time of arrival (TOA) measurements for 30 newly discovered pulsars as well as for 13 known pulsars. We demonstrate that the TOA measurements acquired by the FAST from any beams of the receiver in any observation mode (e.g. the tracking mode or the snapshot mode) can be combined to get timing solutions. We update the ephemerides of 13 previously known pulsars and obtain the first phase-coherent timing results for 30 isolated pulsars discovered in the FAST GPPS Survey. Notably, PSR J1904+0853 is an isolated millisecond pulsar, PSR J1906+0757 is a disrupted recycled pulsar, and PSR J1856+0211 has a long period of 9.89 s that can constrain pulsar death lines. Based on these timing solutions, all available FAST data have been added together to obtain the best pulse profiles for these pulsars. [ABSTRACT FROM AUTHOR]

Spider pulsars are neutron stars that have a companion star in a close orbit. The companion star sheds material to the neutron star, spinning it up to millisecond rotation periods, while the orbit shortens to hours. The companion is eventually ablated and destroyed by the pulsar wind and radiation1,2. Spider pulsars are key for studying the evolutionary link between accreting X-ray pulsars and isolated millisecond pulsars, pulsar irradiation effects and the birth of massive neutron stars3–6. Black widow pulsars in extremely compact orbits (as short as 62 minutes7) have companions with masses much smaller than 0.1 M⊙. They may have evolved from redback pulsars with companion masses of about 0.1–0.4 M⊙ and orbital periods of less than 1 day8. If this is true, then there should be a population of millisecond pulsars with moderate-mass companions and very short orbital periods9, but, hitherto, no such system was known. Here we report radio observations of the binary millisecond pulsar PSR J1953+1844 (M71E) that show it to have an orbital period of 53.3 minutes and a companion with a mass of around 0.07 M⊙. It is a faint X-ray source and located 2.5 arcminutes from the centre of the globular cluster M71.PSR J1953+1844 (M71E) has an orbital period of 53.3 minutes and a companion with a mass of 0.07 M⊙, making it a bridging object between redbacks and black widows in the evolutionary track. [ABSTRACT FROM AUTHOR]

During cluster mergers, the intracluster gas and member galaxies undergo dynamic evolution, but at different time-scales and reach different states. We collect 24 galaxy clusters in quasi-equilibrium state as indicated by the X-ray image, and calculate the cluster orientations and three kinds of dynamical parameters, i.e. the normalized centroid offset, the sphere index, and the ellipticity, for these clusters from the distributions of member galaxies and also the intracluster gas. We find consistent alignments for the orientations estimated from the two components. However, the three kinds of dynamical parameters indicated by member galaxies are systematically larger than those derived from the gas component, suggesting that the gas component is more relaxed than member galaxies. Differences of dynamical features between the intracluster gas and member galaxies are independent of cluster mass and concentration. We conclude that the intracluster gas reaches the dynamic equilibrium state earlier than the almost-collisionless member galaxies. [ABSTRACT FROM AUTHOR]

Using photometric data from the Dark Energy Survey and the Wide-field Infrared Survey Explorer, we estimate photometric redshifts for 105 million galaxies using the nearest-neighbour algorithm. From such a large data base, 151 244 clusters of galaxies are identified in the redshift range of 0.1 < z ≲ 1.5 based on the overdensity of the total stellar mass of galaxies within a given photometric redshift slice, among which 76 826 clusters are newly identified and 30 477 clusters have a redshift z > 1. We cross-match these clusters with those in the catalogues identified from the X-ray surveys and the Sunyaev–Zel'dovich (SZ) effect by the Planck , South Pole Telescope and Atacama Cosmology Telescope surveys, and get the redshifts for 45 X-ray clusters and 56 SZ clusters. More than 95 per cent SZ clusters in the sky region have counterparts in our catalogue. We find multiple optical clusters in the line of sight towards about 15 per cent of SZ clusters. [ABSTRACT FROM AUTHOR]

Using the Global Magneto-Ionic Medium Survey (GMIMS) Low-Band South (LBS) southern sky polarization survey, covering 300–480 MHz at 81  arcmin resolution, we reveal the brightest region in the southern polarized sky at these frequencies. The region, G150−50, covers nearly 20  |$\deg ^2$|⁠ , near (l, b) ≈ (150○, −50○). Using GMIMS-LBS and complementary data at higher frequencies (∼0.6–30 GHz), we apply Faraday tomography and Stokes QU -fitting techniques. We find that the magnetic field associated with G150−50 is both coherent and primarily in the plane of the sky, and indicates that the region is associated with Radio Loop II. The Faraday depth spectra across G150−50 are broad and contain a large-scale spatial gradient. We model the magnetic field in the region as an expanding shell, and we can reproduce both the observed Faraday rotation and the synchrotron emission in the GMIMS-LBS band. Using QU fitting, we find that the Faraday spectra are produced by several Faraday dispersive sources along the line of sight. Alternatively, polarization horizon effects that we cannot model are adding complexity to the high-frequency polarized spectra. The magnetic field structure of Loop II dominates a large fraction of the sky, and studies of the large-scale polarized sky will need to account for this object. Studies of G150−50 with high angular resolution could mitigate polarization horizon effects, and clarify the nature of G150−50. [ABSTRACT FROM AUTHOR]

We investigated the genetic diversity and population genetic structure of six morphologically distinct Ethiopian donkey populations using 12 equine microsatellite markers. The donkey populations were Abyssinian (AB), Afar (AF), Hararghe (HA), Ogaden (OG), Omo (OM) and Sinnar (SI). Blood samples were collected from 180 genetically unrelated donkeys (30 individuals per population). Population genetic diversity estimates showed that total number and mean number of observed alleles, average observed and expected heterozygositywere 94, 5.208 ± 0.0229, 0.555 ± 0.023 and 0.588 ± 0.022, respectively. Highly significant deficiency in heterozygote was detectedwithin the overall samples (FIS = 0.055 ± 0.021; P < 0.001). Though highly significant (P < 0.001), heterozygote deficiency within populations relative to total population was moderate (FST = 0.046 ± 0.016), suggesting a higher diversity within the populations (95.4%) than between populations. Various genetic distance estimation methods produced a similar topology of un-rooted dendrograms that grouped the overall Ethiopian donkeys into lowland (Ogaden, Omo and Sinnar) and highland (Abyssinian, Afar and Hararghe) genetic lineages. Likewise, Bayesian clustering analysis produced a similar pattern of clustering that was highly concordant with traditional donkey classification systems in Ethiopia. [ABSTRACT FROM AUTHOR]

In the framework of the relativistic mean field theory, the neutrino emission from the baryonic direct URCA processes and nucleonic modified URCA processes in neutron star (NS) matter is investigated. We discuss particularly the influence of the extension of the SU(6) spin-flavor symmetry to the SU(3) flavor symmetry on the sizes of the neutrino energy losses, baryonic density and mass ranges of the above neutrino emission processes. In the nucleonic direct URCA processes, the neutrino energy losses in NS matter consisted of npe μ are observably higher than these in NS matter involving hyperons. For NS matter involving hyperons, the neutrino energy losses with the SU(3) flavor symmetry are slightly lower than those with the SU(6) spin-flavor symmetry. In the hyperonic direct URCA processes, the neutrino energy losses for the reactions of Λ → p + l + ν ̄ l and Ξ − → Λ + l + ν ̄ l with the SU(3) flavor symmetry are obviously smaller than these with the SU(6) spin-flavor symmetry. However, the neutrino energy loss of the reaction of Ξ − → Ξ 0 + e + ν ̄ e with the SU(3) flavor symmetry is observably higher than that with the SU(6) spin-flavor symmetry. Moreover, the threshold densities of processes for Ξ − → Ξ 0 + e + ν ̄ e with the SU(3) flavor and SU(6) spin-flavor symmetries are 0.868 fm − 3 and 0.806 fm − 3 (corresponding to 2.118 M ⊙ and 1.838 M ⊙ ), respectively, which mean that it only happens in the interior of the massive NSs. For the neutron and proton branch modified URCA processes, the neutrino emission rates with the SU(3) flavor symmetry are also less than those with the SU(6) spin-flavor symmetry. [ABSTRACT FROM AUTHOR]

We have developed a collective plasma radio emission model for the radio pulsars based on the implications of the tangent model. The secondary pair (electron–positron) plasma particles get arranged into a phased array like an antenna due to plasma waves and radiate in phase. We have reproduced the polarization profiles by considering different viewing conditions in the pulsars having an oblique dipolar magnetic field. We find that when there is a resonance between the radio and the plasma waves, the flux of emitted radio waves gets enhanced. We numerically estimated the collective radio emission due to relativistic plasma. The model predicts the correlation between the sign reversal circular polarization and the polarization angle swing and the brightness temperature in the range ∼1031–1033 K. [ABSTRACT FROM AUTHOR]

As radio telescopes become more sensitive, radio frequency interference (RFI) is becoming more important for interesting signals of radio astronomy. There is a demand for developing an automatic, accurate and efficient RFI mitigation method. Therefore, we have investigated an RFI detection algorithm. First, we introduce an asymmetrically reweighted penalized least squares (ArPLS) method to estimate the baseline more accurately. After removing the estimated baseline, several novel strategies were proposed based on the SumThreshold algorithm for detecting different types of RFI. The threshold parameter in SumThreshold can be determined automatically and adaptively. The adaptiveness is essential for reducing human intervention and for the online RFI processing pipeline. Applications to data from the Five-hundred-meter Aperture Spherical Telescope (FAST) show that the proposed scheme based on ArPLS and SumThreshold is superior to some typically available methods for RFI detection with respect to efficiency and performance. [ABSTRACT FROM AUTHOR]

We first present a catalogue of photometric redshifts for 14.68 million galaxies derived from the 7-band photometric data of Hyper Suprime-Cam Subaru Strategic Program and the Wide-field Infrared Survey Explorer using the nearest-neighbour algorithm. The redshift uncertainty is about 0.024 for galaxies of z  ≤ 0.7, and steadily increases with redshift to about 0.11 at z  ∼ 2. From such a large data set, we identify 21 661 clusters of galaxies, among which 5537 clusters have redshifts z > 1 and 642 clusters have z > 1.5, significantly enlarging the high redshift sample of galaxy clusters. Cluster richness and mass are estimated, and these clusters have an equivalent mass of M 500 ≥ 0.7 × 1014 M⊙. We find that the stellar mass of the brightest cluster galaxies (BCGs) in each richness bin does not significantly evolve with redshift. The fraction of star-forming BCGs increases with redshift, but does not depend on cluster mass. [ABSTRACT FROM AUTHOR]

Fast radio bursts (FRBs) are millisecond-duration radio transients1,2 of unknown origin. Two possible mechanisms that could generate extremely coherent emission from FRBs invoke neutron star magnetospheres3–5 or relativistic shocks far from the central energy source6–8. Detailed polarization observations may help us to understand the emission mechanism. However, the available FRB polarization data have been perplexing, because they show a host of polarimetric properties, including either a constant polarization angle during each burst for some repeaters9,10 or variable polarization angles in some other apparently one-off events11,12. Here we report observations of 15 bursts from FRB 180301 and find various polarization angle swings in seven of them. The diversity of the polarization angle features of these bursts is consistent with a magnetospheric origin of the radio emission, and disfavours the radiation models invoking relativistic shocks. Polarization observations of the fast radio burst FRB 180301 with the FAST radio telescope show diverse polarization angle swings, consistent with a magnetospheric origin of the emission. [ABSTRACT FROM AUTHOR]

Nucleonic direct Urca processes and cooling of the massive neutron stars are studied by considering antikaon condensations. Calculations are performed in the relativistic mean field and isothermal interior approximations. Neutrino energy losses of the nucleonic direct Urca processes are reduced when the optical potential of antikaons changes from − 80 to − 130 MeV. If the center density of the massive neutron stars is a constant, the masses taper off with the optical potential of antikaons, and neutrino luminosities of the nucleonic direct Urca processes decrease for ρ CN = 0.5 fm − 3 but first increase and then decrease for larger ρ CN . Large optical potential of antikaons results in warming of the nonsuperfluid massive neutron stars. Massive neutron stars turn warmer with the protonic S 0 1 superfluids. However, the decline of the critical temperatures of the protonic S 0 1 superfluids for the large optical potential of antikaons can speed up the cooling of the massive neutron stars. [ABSTRACT FROM AUTHOR]

The dynamical state of galaxy clusters describes if clusters are relaxed dynamically or in a merging process of subclusters. Using archival images from the Chandra X-ray Observatory , we derive a set of parameters to describe the dynamical state for 964 galaxy clusters. Three widely used indicators for dynamical state, the concentration index c , the centroid shift ω, and the power ratio P 3/ P 0 are calculated in the circular central region with a radius of 500 kpc. We also derive two adaptive parameters, the profile parameter κ and the asymmetry factor α, in the best fitted elliptical region. The morphology index δ is then defined by combining these two adaptive parameters, which indicates the dynamical state of galaxy clusters and has good correlations to the concentration index c , the centroid shift ω, the power ratio P 3/ P 0, and the optical relaxation factor Γ. For a large sample of clusters, the dynamical parameters are continuously distributed from the disturbed to relaxed states with a peak in the between, rather than the bimodal distribution for the two states. We find that the newly derived morphology index δ works for the similar fundamental plane between the radio power, cluster mass, and the dynamical state for clusters with diffuse radio giant-haloes and mini-haloes. The offset between masses estimated from the Sunyaev–Zeld́ovich effect and X-ray images depends on dynamical parameters. All dynamical parameters for galaxy clusters derived from the Chandra archival images are available on http://zmtt.bao.ac.cn/galaxy_clusters/dyXimages/. [ABSTRACT FROM AUTHOR]

Sensitive radio continuum surveys of the Galactic plane are ideal for discovering new supernova remnants (SNRs). From the Sino-German λ6-cm polarization survey of the Galactic plane, an extended shell-like structure has been found at ℓ = 21 |${^{\circ}_{.}}$| 8, b  = −3 |${^{\circ}_{.}}$| 0, which has a size of about 1°. New observations were made with the Effelsberg 100-m radio telescope at λ11 cm to estimate the source spectrum, together with Urumqi λ6-cm and Effelsberg λ21-cm data. The spectral index of G21.8−3.0 was found to be α = −0.72 ± 0.16. Polarized emission was mostly detected in the eastern half of G21.8−3.0 at both λ6 and λ11 cm. These properties, together with the Hα filament along its northern periphery and the lack of infrared emission, indicate that the emission is non-thermal, as is usual in shell-type SNRs. [ABSTRACT FROM AUTHOR]

We characterize local large-scale regular magnetic fields as well as small-scale magnetic features in the solar vicinity by using the rotation measures of 494 pulsars within 3 kpc from the Sun. The local magnetic field in the Galactic disc is found to follow local spiral arms and to have a field strength of 1.6 μG, with a reversal at 140 pc inside the solar circle in the direction of the Galactic Centre. A field reversal in the first quadrant towards the Sagittarius arm is identified at about 1 kpc from the Sun. In the local Galactic halo, the toroidal fields have a field strength of more than 1.6 μG. Local small-scale magnetic bubbles are investigated by using nearby pulsars in and behind these structures. The Local Bubble might have a line-of-sight magnetic field strength of 0.5–2 μG mainly towards l  ∼ 90°; the upper shell of the Gum Nebula shows a possible amplification of the magnetic field with a factor of 2 probably by compression; the North Polar Spur does not contribute significant Faraday rotation, and perhaps its magnetic field is nearly perpendicular to the line of sight. An anomalous region in the fourth quadrant is found to have a field of 1.4 μG over a scale of 1 kpc, which implies a sub-Galactic structure with ordered fields opposite in direction to the large-scale disc field. We develop a model for the magnetic field in the Galactic halo based on the rotation measures of pulsars and averaged rotation measures of background radio sources. [ABSTRACT FROM AUTHOR]

Context. Large-scale radio continuum surveys provide data to get insights into the physical properties of radio sources. H II regions are prominent radio sources produced by thermal emission of ionised gas around young massive stars. Aims. We identify and analyse H II regions in the Sino-German λ6 cm polarisation survey of the Galactic plane. Methods. Objects with flat radio continuum spectra together with infrared and/or Hα emission were identified as H II regions. For H II regions with small apparent sizes, we cross-matched the λ6 cm small-diameter source catalogue with the radio H II region catalogue compiled by Paladini and the infrared H II region catalogue based on the WISE data. Effelsberg λ21 cm and λ11 cm continuum survey data were used to determine source spectra. High angular resolution data from the Canadian Galactic Plane Survey and the NRAO VLA Sky Survey were used to solve the confusion when low angular resolution observations were not sufficient. Extended H II regions were identified by eye by overlaying the Paladini and the WISE H II regions onto the λ6 cm survey images for coincidences. The TT-plot method was employed for spectral index verification. Results. A total of 401 H II regions were identified and their flux densities were determined with the Sino-German λ6 cm survey data. In the surveyed area, 76 pairs of sources are found to be duplicated in the Paladini H II region catalogue, mainly due to the non-distinction of previous observations with different angular resolutions and 78 objects in their catalogue are misclassified as H II regions, being actually planetary nebulae, supernova remnants, or extragalactic sources that have steep spectra. More than 30 H II regions and H II region candidates from our λ6 cm survey data, especially extended ones, do not have counterparts in the WISE H II region catalogue, of which 9 are identified for the first time. Our results imply that some more Galactic H II regions still await to be discovered and the combination of multi-domain observations is important for H II region identification. Based on the newly derived radio continuum spectra and the evidence of infrared emission, the previously identified SNRs G11.1−1.0, G20.4+0.1 and G16.4−0.5 are believed to be H II regions. [ABSTRACT FROM AUTHOR]

We identify a sample of 1959 massive clusters of galaxies in the redshift range of 0.7 < |$z$| < 1.0 from the survey data of Sloan Digital Sky Survey (SDSS) and Wide-field Infrared Survey Explorer (WISE). These clusters are recognized as the overdensity regions of galaxies in the foreground-cleaned WISE data around the SDSS luminous red galaxies, having a richness greater than 15 or an equivalent mass |$M_{500} \ge 2.5\times 10^{14}\, \mathrm{M}_{\odot }$|⁠. Among them, 1505 clusters are identified for the first time, which significantly enlarge the number of high-redshift clusters of |$z$| > 0.75. By comparing them with clusters at lower redshifts, we confirm that richer clusters host more luminous brightest cluster galaxies (BCGs) also at high redshifts, and that the fraction of blue galaxies is larger in clusters at higher redshifts. A small fraction of BCGs show ongoing star formation or active nuclei. The number density profile of member galaxies in stacked samples of clusters shows no significant redshift evolution. [ABSTRACT FROM AUTHOR]

Summary: The aim of the present study was to perform a preliminary analysis of the characterization and diversity of Y‐chromosome haplotypes/haplogroups in yak of Qinghai Province, China. A total of 322 male yaks from nine populations belonging to three officially recognized breeds (Gaoyuan, Huanhu and Datong) were sampled. Animals were genotyped using six previously reported Y‐SNPs present in the SRY,USP9Y,UTY,AMELY and OFD1Y genes and four new Y‐SNPs in the OFD1Y gene (g.569A>C, g.578A>C, g.608G>T and g.653G>C) identified in this study. Seven Y‐chromosome haplotypes (H1–H7) were identified according to the combination of the 10 Y‐SNPs. H1, H2 and H6 were the most common and shared haplotypes across all yak populations/breeds. Private haplotypes H3 and H7 were detected in the Datong breed; H4 in Guoleimude, Qumalai, Qilian, Tianjun and Ganglong populations; and H5 in Qumalai of Gaoyuan breed. Haplotype clustering and network analyses inferred two haplogroups, Y1 and Y2, indicating two divergent lineages of paternal origins of Qinghai yak. The analysis of molecular variance showed a significant difference among individuals (P < 0.0001) with more than 93% of the total genetic variation present within populations, suggesting a weak genetic structure among Qinghai yak populations. The overall Y‐haplotype diversity was 0.538 ± 0.028, showing a relatively high diversity in Qinghai yak. The Gaoyuan and Datong breeds had similar haplotype diversities (0.547 ± 0.030 and 0.553 ± 0.083, respectively), which were higher than that of the Huanhu breed (0.441 ± 0.098). Our results support the conservation and sustainable use of unique yak genetic resources in Qinghai. [ABSTRACT FROM AUTHOR]

Fast radio bursts (FRBs) are millisecond-duration radio transients of unknown physical origin observed at extragalactic distances1–3. It has long been speculated that magnetars are the engine powering repeating bursts from FRB sources4–13, but no convincing evidence has been collected so far14. Recently, the Galactic magnetar SRG 1935+2154 entered an active phase by emitting intense soft γ-ray bursts15. One FRB-like event with two peaks (FRB 200428) and a luminosity slightly lower than the faintest extragalactic FRBs was detected from the source, in association with a soft γ-ray/hard-X-ray flare18–21. Here we report an eight-hour targeted radio observational campaign comprising four sessions and assisted by multi-wavelength (optical and hard-X-ray) data. During the third session, 29 soft-γ-ray repeater (SGR) bursts were detected in γ-ray energies. Throughout the observing period, we detected no single dispersed pulsed emission coincident with the arrivals of SGR bursts, but unfortunately we were not observing when the FRB was detected. The non-detection places a fluence upper limit that is eight orders of magnitude lower than the fluence of FRB 200428. Our results suggest that FRB–SGR burst associations are rare. FRBs may be highly relativistic and geometrically beamed, or FRB-like events associated with SGR bursts may have narrow spectra and characteristic frequencies outside the observed band. It is also possible that the physical conditions required to achieve coherent radiation in SGR bursts are difficult to satisfy, and that only under extreme conditions could an FRB be associated with an SGR burst. An 8-hour radio observational campaign of the Galactic magnetar SGR 1915+2154, assisted by multi-wavelength data, indicates that associations between fast radio bursts and soft γ-ray bursts are rare. [ABSTRACT FROM AUTHOR]

The pulsar dispersion measure (DM) accounts for the total electron content between a pulsar and us. High-precision observations for projects of pulsar timing arrays show temporal DM variations of millisecond pulsars. The aim of this paper is to decompose the DM variations of 30 millisecond pulsars using the Hilbert–Huang transform (HHT) method, so that we can determine the general DM trends resulting from interstellar clouds and the annual DM variation curves resulting from the solar wind, interplanetary medium and/or ionosphere. We find that the decomposed annual variation curves of 22 pulsars exhibit quasi-sinusoidal, one-component and double-component features of different origins. The amplitudes and phases of the curve peaks are related to the ecliptic latitude and longitude of pulsars, respectively. [ABSTRACT FROM AUTHOR]

We identify 47 600 clusters of galaxies from photometric data of Two Micron All Sky Survey (2MASS), Wide-field Infrared Survey Explorer (WISE), and SuperCOSMOS, among which 26 125 clusters are recognized for the first time and mostly in the sky outside the Sloan Digital Sky Survey (SDSS) area. About 90 per cent of massive clusters of M500 > 3 × 1014M☉ in the redshift range of 0.025 < z < 0.3 have been detected from such survey data, and the detection rate drops down to 50 per cent for clusters with a mass of M500 ∼ 1 × 1014M☉. Monte Carlo simulations show that the false detection rate for the whole cluster sample is less than 5 per cent. By cross-matching with ROSAT and XMM-Newton sources, we get 779 new X-ray cluster candidates which have X-ray counterparts within a projected offset of 0.2 Mpc. [ABSTRACT FROM AUTHOR]

Summary: The X chromosome shows a special interaction between demographic factors and genetic variation, and the analysis of X‐linked genomic variation can therefore provide insights into the unique effects of demography and selection on the horse genome that cannot be readily detected by autosomal markers. Debao (DB) ponies have experienced intense selective pressure for the development of their small stature (<106 cm at adult height). To identify selective sweeps on the X chromosome of the DB pony, we performed a genome‐wide scan of three Chinese horse breeds using an Equine SNP70 BeadChip. Using Yili and Mongolian horses (>134 cm at adult height) as reference groups, both FST and XP‐EHH revealed that five regions on the X chromosome were under strong selection, resulting in 95 overlapping genes. Seven of these genes, SMS, PHEX, ACSL4, CHRDL1, CACNA1F, DKC1 and CDKL5, are involved in bone development, growth hormone secretion and fat deposition. The region showing the strongest selection pressure was located at the position of 86.6–87.5 Mb. The subsequent genome‐wide association analysis of the adult height of three Chinese horse breeds detected the two most significant SNPs in the same region, and these two SNPs overlapped with the gene CHRDL1. As a member of the bone morphogenetic protein (BMP) superfamily, CHRDL1 antagonizes the function of BMP4 and plays an important role in embryonic bone formation and cartilage generation. Our results provide new insights into the X‐linked selection in Chinese Debao pony. [ABSTRACT FROM AUTHOR]

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Highly polarized components of pulse profiles are investigated by analysing observational data and simulating the emission processes. The highly polarized components appear at the leading or trailing part of a pulse profile, which preferably have a flat spectrum and a flat polarization angle curve compared with the low polarized components. By considering the emission processes and propagation effects, we simulate the distributions of wave modes and fractional linear polarization within the entire pulsar emission beam. We show that the highly polarized components can appear at the leading, central, and/or trailing parts of pulse profiles in the models, depending on pulsar geometry. The depolarization is caused by orthogonal modes or scattering. When a sight line cuts across pulsar emission beam with a small impact angle, the detected highly polarized component will be of the O mode, and have a flat polarization angle curve and/or a flat spectrum as observed. Otherwise, the highly polarized component will be of the X mode and have a steep polarization angle curve. [ABSTRACT FROM AUTHOR]

By cross-matching the currently largest optical catalogue of galaxy clusters and the NVSS radio survey data base, we obtain a large complete sample of brightest cluster galaxies (BCGs) in the redshift range of 0.05 < z ≤ 0.45, which have radio emission and redshift information. We confirm that more powerful radio BCGs tend to be these optically very bright galaxies located in more relaxed clusters. We derived the radio luminosity functions of the largest sample of radio BCGs, and find that the functions depend on the optical luminosity of BCGs and the dynamic state of galaxy clusters. However, the radio luminosity function does not show significant evolution with redshift. [ABSTRACT FROM AUTHOR]

Iranian livestock diversity is still largely unexplored, in spite of the interest in the populations historically reared in this country located near the Fertile Crescent, a major livestock domestication centre. In this investigation, the genetic diversity and differentiation of 10 Iranian indigenous fat-tailed sheep breeds were investigated using 18 microsatellite markers. Iranian breeds were found to host a high level of diversity. This conclusion is substantiated by the large number of alleles observed across loci (average 13.83, range 7-22) and by the high within-breed expected heterozygosity (average 0.75, range 0.72-0.76). Iranian sheep have a low level of genetic differentiation, as indicated by the analysis of molecular variance, which allocated a very small proportion (1.67%) of total variation to the between-population component, and by the small fixation index ( FST = 0.02). Both Bayesian clustering and principal coordinates analysis revealed the absence of a detectable genetic structure. Also, no isolation by distance was observed through comparison of genetic and geographical distances. In spite of high within-breed variation, signatures of inbreeding were detected by the FIS indices, which were positive in all and statistically significant in three breeds. Possible factors explaining the patterns observed, such as considerable gene flow and inbreeding probably due to anthropogenic activities in the light of population management and conservation programmes, are discussed. [ABSTRACT FROM AUTHOR]

Soluble palladium and platinum phthalocyanines with coumarin moieties were synthesized with Q bands in the red and near-IR regions, in which the molar extinction coefficients were up to 1.01 × 105 cm−1 mol−1. These metallophthalocyanines were coupled with rubrene and applied in photon upconversion systems based on triplet–triplet annihilation. The highest upconversion efficiency of the palladium phthalocyanine was 5.6%, which is higher than that of the platinum phthalocyanine–rubrene system. The larger molar extinction coefficient resulted in high upconversion capability (＞105 cm−1 mol−1) and low saturation incident power (＜20 mW cm−2). [ABSTRACT FROM AUTHOR]

We report the discovery of a radio halo in the massive merging cluster MACSJ2243.3-0935, as well as a new radio relic candidate, using the Giant Meterwave Radio Telescope and the Karoo Array Telescope-7 telescope. The radio halo is coincident with the cluster X-ray emission and has a largest linear scale of approximately 0.9 Mpc. We measure a flux density of 10.0 ± 2.0 mJy at 610 MHz for the radio halo. We discuss equipartition estimates of the cluster magnetic field and constrain the value to be of the order of 1 μG. The relic candidate is detected at the cluster virial radius where a filament meets the cluster. The relic candidate has a flux density of 5.2 ± 0.8 mJy at 610 MHz.We discuss possible origins of the relic candidate emission and conclude that the candidate is consistent with an infall relic. [ABSTRACT FROM AUTHOR]

PSR B0919+06 generally radiates radio pulses in a normal phase range. It is known for its occasional perplexing abnormal emission events wherein individual pulses come to an earlier phase range for a few tens of periods and then it returns to its usual phase. Heretofore, only a few such events have been available for study. We observed PSR B0919+06 for about 30 h using the Jiamusi 66-m telescope at the Jiamusi Deep Space Station at the S band, and we detected 92 abnormal emission events. We identify four types of events based on the abrupted or gradual phase-shifting of individual pulses. The abnormal emission events are seen to occur randomly about every 1000-3000 periods, and they affect the leading edge of the mean profile by up to 2 per cent in amplitude. The abnormal emission events are probably related to gradual changes of emission processing in the pulsar magnetosphere. [ABSTRACT FROM AUTHOR]

Spiral arms shown by different components may not be spatially coincident, which can constrain formationmechanisms of spiral structure in a galaxy.We reassess the spiral arm tangency directions in the Milky Way through identifying the bump features in the longitude plots of survey data for infrared stars, radio recombination lines (RRLs), star formation sites, CO, high-density regions in clouds, and HI. The bump peaks are taken as indications for arm tangencies, which are close to the real density peaks near the spiral arm tangency point but often have ~1° offset to the interior of spiral arms. The arm tangencies identified from the longitude plots for RRLs, HII regions, methanol masers, CO, high-density gas regions, and HI gas appear nearly the same Galactic longitude, and therefore there is no obvious offset for spiral arms traced by different gas components. However, we find obvious displacements of 1.° 3-5°.8 of gaseous bump peaks from the directions of the maximum density of old stars near the tangencies of the Scutum-Centaurus Arm, the northern part of the Near 3 kpc Arm, and maybe also the Sagittarius Arm. The offsets between the density peaks of gas and old stars for spiral arms are comparable with the arm widths, which is consistent with expectations for quasi-stationary density wave in our Galaxy. [ABSTRACT FROM AUTHOR]

Context. Superbubbles and supershells are the channels for transferring mass and energy from the Galactic disk to the halo. Magnetic fields are believed to play a vital role in their evolution. Aims. We study the radio continuum and polarized emission properties of theW4 superbubble to determine its magnetic field strength. Methods. New sensitive radio continuum observations were made atλ6 cm, λ11 cm, and λ21 cm. The total intensity measurements were used to derive the radio spectrum of the W4 superbubble. The linear polarization data were analysed to determine the magnetic field properties within the bubble shells. Results. The observations show a multi-shell structure of the W4 superbubble. A flat radio continuum spectrum that stems from optically thin thermal emission is derived from 1.4 GHz to 4.8 GHz. By fitting a passive Faraday screen model and considering the filling factor fine, we obtain the thermal electron density ne = 1.0/√fne (±5%) cm-3 and the strength of the line-of-sight component of the magnetic field B// = -5.0/√fne (±10%) µG (i.e. pointing away from us) within the western shell of the W4 superbubble. When the known tilted geometry of the W4 superbubble is considered, the total magnetic field Btot in its western shell is greater than 12 µG. The electron density and the magnetic field are lower and weaker in the high-latitude parts of the superbubble. The rotation measure is found to be positive in the eastern shell but negative in the western shell of the W4 superbubble, which is consistent with the case where the magnetic field in the Perseus arm is lifted up from the plane towards high latitudes. Conclusions. The magnetic field strength and the electron density we derived for the W4 superbubble are important parameters for evolution models of superbubbles breaking out of the Galactic plane. [ABSTRACT FROM AUTHOR]

The frequency dependence of pulsar linear polarization is investigated using simulations of emission and propagation processes. Linearly polarized waves are generated through curvature radiation by relativistic particles streaming along curved magnetic field lines, which have ordinary-mode (O-mode) and extraordinary-mode (X-mode) components. As the emitted waves propagate outwards, the two mode components are separated, due to refraction of the O mode, and their polarization states are also modified. According to the radius-to-frequency mapping, low-frequency emission is generated from the higher magnetosphere, where significant rotation effects lead the X and O modes to become separated. Hence, the low-frequency radiation has a large fraction of linear polarization. As the frequency increases, emission is generated from lower heights, where the rotation effect becomes weaker and the distribution regions of the two modes are more overlapped. Hence, more significant depolarization appears for emission at higher frequencies. In addition, the refraction effect of the O mode becomes significant in the very deep magnetosphere, which bends the O-mode emission towards the outer parts of a pulsar beam and also causes the separation of the mode distribution regions; hence the fractional linear polarization increases with frequency. If emission of different frequencies is generated from a region of the same height, significant O-mode refraction can result in the decrease of both profile width and fractional linear polarization. The observed frequency dependence of linear polarization for some pulsars can be explained naturally within the scope of our scenario. [ABSTRACT FROM AUTHOR]

The luminosity function of cluster galaxies provides a fundamental constraint on galaxy evolution in cluster environments. By using the bright member galaxies of a large sample of rich clusters identified from the Sloan Digital Sky Survey, we obtain the bright end of composite luminosity functions of cluster galaxies, and study their dependence on cluster dynamical states. After a redshift-evolution correction of absolute magnitude, the luminosity function of member galaxies can be well fitted by a Schechter function when the brightest cluster galaxies (BCGs) are excluded. The absolute magnitudes of BCGs follow a Gaussian function with a characteristic width of about 0.36 mag. We find that the luminosity function of galaxies in more relaxed clusters has a fainter characteristic absolute magnitude (M*), and these clusters have fewer bright non-BCG member galaxies but a brighter BCG. Our results suggest the co-evolution of galaxy population with a cluster dynamical state and support the hierarchical formation scenario of the BCGs. [ABSTRACT FROM PUBLISHER]

The dwarf blue sheep (Pseudois schaeferihaltenorth) belongs the subfamily Caprinae, which is distributed in Sichuan, Tibet, Yunnan, and Qinghai in China. In this study, the complete mitochondrial genome ofPseudois schaeferihaltenorth was sequenced. The mitogenome was 16 741 bp in length, consisting of 13 protein-coding genes, 22 transfer RNA (tRNA) genes, 2 ribosomal RNA (rRNA) genes, and a non-coding control region (D-loop region). As in other mammals, most mitochondrial genes are encoded on the heavy strand, except forND6and eight tRNA genes which are encoded on the light strand. The overall base composition of thePseudois schaeferi haltenorthis 33.54% A, 26.37% T, 26.91% C, and 13.18% G, A + T (59.91%) was higher than G + C (40.09%). The phylogenetic relationships was analyzed using the complete mitogenome sequence, results show thatP. schaeferihaltenorth should be a different species differ from the Genus pseudois hodgson. These information provide useful data for further study on the protection of genetic resources and the taxonomy of Caprinae. [ABSTRACT FROM AUTHOR]

We have obtained the rotation measures (RMs) of 2642 quasars by using cross-identification of the most updated quasar catalogue and the RM catalogue. After discounting the foreground Galactic Faraday rotation of the Milky Way, we obtain the residual rotation measure (RRM) of these quasars. We have carefully discarded the effects from measurement and systematical uncertainties of RRMs as well as large RRMs from RM outliers, and we have obtained marginal evidence for the redshift evolution of the real dispersion of RRMs which steadily increases to 10 rad m−2 about z ∼ 1 and is saturated at higher redshifts. Ionized clouds in the form of galaxy halos, galaxy clusters or cosmological filaments with different RM dispersion widths could produce the observed RRM evolutions. However, current data sets cannot constrain the contributions from galaxy halos and cosmic webs. Future measurements of RMs for a large sample of quasars with high precision are necessary to disentangle these different contributions. [ABSTRACT FROM PUBLISHER]