查看更多>>摘要：We develop a Python tool to estimate the tail distribution of the number of dark matter halos beyond a mass threshold and in a given volume in a light-cone.The code is based on the extended Press-Schechter model and is computationally efficient,typically taking a few seconds on a personal laptop for a given set of cosmological parameters.The high efficiency of the code allows a quick estimation of the tension between cosmological models and the red candidate massive galaxies released by the James Webb Space Telescope,as well as scanning the theory space with the Markov Chain Monte Carlo method.As an example application,we use the tool to study the cosmological implication of the candidate galaxies presented in Labbé et al.The standard ∧ cold dark matter(∧CDM)model is well consistent with the data if the star formation efficiency can reach～0.3 at high redshift.For a low star formation efficiency ε～0.1,the ∧CDM model is disfavored at～2σ-3σ confidence level.
查看更多>>摘要：The overabundance of the red and massive candidate galaxies observed by the James Webb Space Telescope(JWST)implies efficient structure formation or large star formation efficiency at high redshift z～10.In the scenario of a low or moderate star formation efficiency,because massive neutrinos tend to suppress the growth of structure of the universe,the JWST observation tightens the upper bound of the neutrino masses.Assuming A cold dark matter cosmology and a star formation efficiency ∈[0.05,0.3](flat prior),we perform joint analyses of Planck+JWST and Planck+BAO+JWST,and obtain improved constraints Σmv＜0.196eV and Σmv＜0.111 eV at 95％ confidence level,respectively.Based on the above assumptions,the inverted mass ordering,which implies Σmv≥0.1eV,is excluded by Planck+BAO+JWST at 92.7％ confidence level.
查看更多>>摘要：For the ASO-S/HXI payload,the accuracy of the flare reconstruction is reliant on important factors such as the alignment of the dual grating and the precise measurement of observation orientation.To guarantee optimal functionality of the instrument throughout its life cycle,the Solar Aspect System(SAS)is imperative to ensure that measurements are accurate and reliable.This is achieved by capturing the target motion and utilizing a physical model-based inversion algorithm.However,the SAS optical system's inversion model is a typical ill-posed inverse problem due to its optical parameters,which results in small target sampling errors triggering unacceptable shifts in the solution.To enhance inversion accuracy and make it more robust against observation errors,we suggest dividing the inversion operation into two stages based on the SAS spot motion model.First,the as-rigid-as-possible(ARAP)transformation algorithm calculates the relative rotations and an intermediate variable between the substrates.Second,we solve an inversion linear equation for the relative translation of the substrates,the offset of the optical axes,and the observation orientation.To address the ill-posed challenge,the Tikhonov method grounded on the discrepancy criterion and the maximum a posteriori(MAP)method founded on the Bayesian framework are utilized.The simulation results exhibit that the ARAP method achieves a solution with a rotational error of roughly±3".5(1/2-quantile);both regularization techniques are successful in enhancing the stability of the solution,the variance of error in the MAP method is even smaller—it achieves a translational error of approximately±18μm(1/2-quantile)in comparison to the Tikhonov method's error of around±24μm(1/2-quantile).Furthermore,the SAS practical application data indicates the method's usability in this study.Lastly,this paper discusses the intrinsic interconnections between the regularization methods.
查看更多>>摘要：The China Space Station Telescope(CSST)is a two-meter space telescope with multiple back-end instruments.The Fine Guidance Sensor(FGS)is an essential subsystem of the CSST Precision Image Stability System to ensure the required absolute pointing accuracy and line-of-sight stabilization.In this study,we construct the Main Guide Star Catalog for FGS.To accomplish this,we utilize the information about the FGS and object information from the Gaia Data Release 3.We provide an FGS instrument magnitude and exclude variables,binaries,and high proper motion stars from the catalog to ensure uniform FGS guidance capabilities.Subsequently,we generate a HEALPix index,which provides a hierarchical tessellation of the celestial sphere,and employ the Voronoi algorithm to achieve a homogeneous distribution of stars across the catalog.This distribution ensures adequate coverage and sampling of the sky.The performance of the CSST guide star catalog was assessed by simulating the field of view of the FGS according to the CSST mock survey strategy catalog.The analysis of the results indicates that this catalog provides adequate coverage and accuracy.The catalog's performance meets the FGS requirements,ensuring the functioning of the FGS and its guidance capabilities.
查看更多>>摘要：The receiver is a signal receiving device placed at the focus of the telescope.In order to improve the observation efficiency,the concept of phased array receiver has been proposed in recent years,which places a small phased array at the focal plane of the reflector,and flexible pattern and beam scanning functions can be achieved through a beamforming network.If combined with the element multiplexing,all beams within the entire field of view can be observed simultaneously to achieve continuous sky coverage.This article focuses on the front-end array of phased array receiver at 0.7-1.8 GHz for QiTai Telescope,and designs a Vivaldi antenna array of PCB structure with dual line polarization.Each polarization antenna is designed to arrange in a rectangle manner by 11 x 10.Based on the simulation results of the focal field,32,18,and eight elements were selected to form one beam at 0.7,1.25,and 1.8 GHz.An analog beamforming network was constructed,and the measured gains of axial beam under uniform weighting were 19.32,13.72,and 15.22 dBi.Combining the beam scanning method of reflector antenna,the pattem test of different position element sets required for PAF beam scanning was carried out under independent array.The pattern optimization at 1.25 GHz was carried out by weighting method of conjugate field matching.Compared with uniform weighting,the gain,sidelobe level,and main beam direction under conjugate field matching have been improved.Although the above test and simulation results are slightly different,which is related to the passive array and laboratory testing condition,the relevant work has accumulated experience in the development of the front-end array for the phased array receiver,and has good guiding significance for future performance verification after the array is installed on the telescope.
查看更多>>摘要：The solar flare is one of the most violent explosions,and can disturb the near-Earth space weather.Except for commonly single-peaked solar flares in soft X-ray,some special flares show intriguing a two-peak feature that is deserved much more attentions.Here,we reported a confined two-peaked solar flare and analyzed the associated eruptions using high-quality observations from Educational Adaptive-optics Solar Telescope and Solar Dynamics Observatory.Before the flare,a magnetic flux rope(MFR)formed through partially tether-cutting reconnection between two sheared arches.The flare occurred after the MFR eruption that was confined by the overlying strong field.Interestingly,a small underlying filament immediately erupted,which was possibly destabilized by the flare ribbon.The successive eruptions were confirmed by the analysis of the emission measure and the reconnection fluxes.Therefore,we suggest that the two peaks of the confined solar flare are corresponding to two episodes of magnetic reconnection during the successive eruptions of the MFR and the underlying filament.
查看更多>>摘要：The triggering mechanism for radio lobes from late-type galaxies is not fully understood.More samples are desired for a thorough investigation and statistics.By utilizing the optical data from the newly released Dark Energy Spectroscopic Instrument imaging surveys and the radio sources from the NRAO VLA Sky Survey and the Faint Images of the Radio Sky at Twenty-centimeter,we identify four Late-type Galaxies with double Radio Lobes(LaGRLs):J0217-3645,J0947+6220,J1412+3723 and J1736+5108.Including previously known LaGRLs,we confirm the correlation between radio power P1.4 GHz and stellar mass M*of host galaxies.Most(25/35)LaGRLs belong to the blue cloud galaxies,while the newly identified cases in this work are located within the region of the red sequence.We find a clear correlation between the differential radio power,i.e.,the offset from the P1.4 GHz-M*relation,and the galaxy color,indicating that bluer galaxies at a fixed M*tend to host more powerful radio lobes.Furthermore,the majority(31/36)of LaGRLs are either located in a galaxy group or displaying a disturbed morphology.We suggest that all of the galaxy mass,color and surrounding environment could play important roles in triggering radio lobes in late-type galaxies.
查看更多>>摘要：We investigate the population and several properties of radio pulsars whose emission does not null(non-nulling)through simulation of a large pulsar sample.Emission from a pulsar is identified as non-nulling if(i)the emission does not cease across the whole pulse profile,and(ii)the emission is detectable.For(i),we adopt a model for switching in the plasma charge density,and emission persists if the charge density is non-zero.For(ii),we assume that detectable emission originates from source points where it is emitted tangentially to the magnetic field-line and parallel to the line-of-sight.We find that pulsars exhibiting non-nulling emission possess obliquity angles with an average of 42°5,and almost half the samples maintain a duty cycle between 0.05 and 0.2.Furthermore,the pulsar population is not fixed but dependent on the obliquity angle,with the population peaking at 20°.In addition,three evolutionary phases are identified in the pulsar population as the obliquity angle evolves,with the majority of samples having an obliquity angle between 20° and 65°.Our results also suggest that emission from a pulsar may evolve between nulling and non-nulling during its lifetime.
查看更多>>摘要：We have developed a novel method for co-adding multiple under-sampled images that combines the iteratively reweighted least squares and divide-and-conquer algorithms.Our approach not only allows for the anti-aliasing of the images but also enables Point-Spread Function(PSF)deconvolution,resulting in enhanced restoration of extended sources,the highest peak signal-to-noise ratio,and reduced ringing artefacts.To test our method,we conducted numerical simulations that replicated observation runs of the China Space Station Telescope/the VLT Survey Telescope(VST)and compared our results to those obtained using previous algorithms.The simulation showed that our method outperforms previous approaches in several ways,such as restoring the profile of extended sources and minimizing ringing artefacts.Additionally,because our method relies on the inherent advantages of least squares fitting,it is more versatile and does not depend on the local uniformity hypothesis for the PSF.However,the new method consumes much more computation than the other approaches.
查看更多>>摘要：Rotating Radio Transients(RRATs)are a relatively new subclass of pulsars that emit detectable radio bursts sporadically.We analyzed 10 RRATs observed using the Parkes telescope,with eight of these observed via the ultra-wide-bandwidth low-frequency(UWL)receiver.We measured the burst rate and produced integrated profiles spanning multiple frequency bands for three RRATs.We also conducted a spectral analysis on both integrated pulses and individual pulses of three RRATs.All of their integrated pulses follow a simple power law,consistent with the known range of pulsar spectral indices.Their average spectral indices of single pulses are-0.9,-1.2,and-1.0 respectively,which are within the known range of pulsar spectral indices.Additionally,we find that the spreads of single-pulse spectral indices for these RRATs(ranging from-3.5 to+0.5)are narrower compared to what has been observed in other RRATs.Notably,the average spectral index and scatter of single pulses are both relatively small.For the remaining five RRATs observed at the UWL receiver,we also provide the upper limits on fluence and flux density.In addition,we obtain the timing solution of PSR J1709-43.Our analysis shows that PSRs J1919+1745,J1709-43,and J1649-4653 are potentially nulling pulsars or weak pulsars with sparse strong pulses.
万方数据
维普