Subjects: Mechanics >> Other Disciplines of Mechanics submitted time 2024-08-13 Cooperative journals: 《应用力学学报》
Abstract：
The superconductor Nb3Sn has demonstrated great potential for its applications in the manufacturing of high field superconducting magnets and superconducting resonant cavities.The electromechanical coupling effect involved in the superconducting transition of Nb3Sn has adverse effects on the electromagnetic performance and safe operation of superconducting magnets.In view of the fact that Nb3Sn has two phase structures:cubic phase and tetragonal phase,based on the results of the first principles and the polycrystalline finite element calculation,the mechanical models of cubic Nb3Sn,tetragonal Nb3Sn as well as the mixture of the cubic phase and the tetragonal phase are established.The electromechanical coupling model,accounting for the mechanical deformation induced critical temperature degradation and the strain-dependent normal-state resistivity variations,is also developed.The results indicate that the phase structure will lead to the difference in the elastic properties of single crystal; however,the local stress state of polycrystalline Nb3Sn with different phase structures under hydrostatic pressure is independent of the phase structure,and the grain boundary stress concentration depends only on the grain morphology and orientation.The evolution of the electronic density of states at the Fermi surface under external loading is basically the same for the different phase structures,which makes the mechanical deformation-induced critical temperature degradation response independent of the phase structure.The normal state resistivity variation of the mixed phase Nb3Sn can be characterized by the T2 law based on the assumption of electron-electron scattering if the temperature is lower than the martensitic transition temperature.When the temperature is higher than the martensitic phase transition temperature,the contribution of electron-phonon coupling to the normal state resistivity should be considered because the cubic phase transforms into a tetragonal phase; thus the extended Woodard-Cody resistivity model can be used to describe the strain effect of macroscopic resistivity.The results of this paper enhance the understanding of the mechanism of the degradation of the critical temperature and provide some basis for understanding the effect of phase structure on the critical properties and normal state resistivity of Nb3Sn.
Subjects: Mechanics >> Other Disciplines of Mechanics submitted time 2024-08-13 Cooperative journals: 《应用力学学报》
Abstract：
In order to promote the development of bamboo structures,a new design method for bamboo structures based on topology optimization is suggested and the corresponding static tests research for contrast are completed as well.First,the systematic method for guiding bamboo structure design by the light of evolutionary structural optimization was discussed.Then,combined with engineering examples,a dual-lane bridge structure wasoptimally designed to two kinds based on optimization feasible domains of evolving separately to pressure bearing structure and tension structure.Afterwards,the static tests research was carried out for contrast.The results show that the optimal designed bridge structures coincided with Michell-type truss structures.Their structural stiffness was significantly higher than that of empirical design members.Furthermore,the pressure bearing topological arch structures had larger stiffness about three times than the tension topological suspension structures,and yet their ultimate bearing capacity was slightly lower.Thus,the new design method based on evolutionary structural optimization can obtain different schemes by the guidance of appropriate optimization feasible domains according to different design requirements for bearing capacity and stiffness.It is so simple and practical that provides an optimal design method for engineering bamboo structure,which can be analyzed and calculated automatically.
Subjects: Nuclear Science and Technology >> Radiation Physics and Technology submitted time 2024-07-29
Abstract： The off-situ accurate reconstruction of the core neutron field is an important step in realizing real-time reactor monitoring. The existing off-situ reconstruction method of the neutron field is only applicable to cases wherein a single region changes at a specified location of the core. However, when the neutron field changes are complex, the accurate identification of the individual changed regions becomes challenging, which seriously affects the accuracy and stability of the neutron field reconstruction. Therefore, this study proposed a dual-task hybrid network architecture (DTHNet) for off-situ reconstruction of the core neutron field, which trained the outermost assembly reconstruction task and the core reconstruction task jointly such that the former could assist the latter in the reconstruction of the core neutron field under core complex changes. Furthermore, to exploit the characteristics of the ex-core detection signals, this study designed a global-local feature upsampling module that efficiently distributed the ex-core detection signals to each reconstruction unit to improve the accuracy and stability of reconstruction. Reconstruction experiments were performed on the simulation datasets of the CLEAR-I reactor to verify the accuracy and stability of the proposed method. The results showed that when the location uncertainty of a single region did not exceed nine and the number of multiple changed regions did not exceed five. Further, the reconstructed ARD was within 2%, RDmax was maintained within 17.5%, and the number of RD≥10% was maintained within 10. Furthermore, when the noise interference of the ex-core detection signals were within ±2%, although the average number of RD≥10% increased to 16, the average ARD was still within in 2%, and the average RDmax was within 22%. Collectively, these results show that, theoretically, the DTHNet can accurately and stably reconstruct most of the neutron field under certain complex core changes.
Subjects: Physics >> Nuclear Physics Subjects: Physics >> Interdisciplinary Physics and Related Areas of Science and Technology submitted time 2024-08-09
Abstract： Scanning magnets are devices responsible for deflecting particles to specific locations in particle therapy utilizing spot scanning techniques. To ensure the distortion of the scanned beams’ shapes remains within an acceptable level, it is necessary to guarantee that the homogeneity of the field integrals is sufficiently high in the two transversal directions within the good field region. Typically, this is accomplished by adding shims on both sides of magnet poles. In this study, we innovatively proposed a method to perform multi-objective optimization of shim parameters and excitation currents by the state-of-the-art evolutionary algorithm Non- dominated Sorting Genetic Algorithm-III (NSGA-III). Furthermore computer vision (CV) was implemented to automatically evaluate both the beam shape distortions and the centroids of the scanned beam spots at the target plane to assist efficient optimization process. With this method, optimal parameters of scanning magnets which have capability of scanning a carbon beam of 400 MeV/u beam energy across a 20 cm × 20 cm field size with a source-to-axis distance of 255 cm were obtained successfully. Meanwhile, we also conducted eddy current and temperature rise analysis, laminated steel plates with 19 slits cut near the pole gaps were used to reduce eddy
currents due to rapid variation of magnetic fields during the scanning process. Based on the optimized magnets
parameters, eddy current and temperature analyses were performed and the temperature rises were found to be near 40°C and 54°C for the Y and X magnets respectively at the designed scanning speeds, which meets the requirements for normal operation. This proposed procedure of optimization is expected to facilitate efficient and sophisticated design of various magnets applied to charged particle accelerators.
Peer Review Status:
Awaiting Review
Subjects: Nuclear Science and Technology >> Other Disciplines of Nuclear Science submitted time 2024-02-01
Abstract： Betavoltaic nuclear batteries show promise as compact and enduring power sources for microelectromechanical systems (MEMS). Current theoretical calculations often overlook practical diode characteristics like surface recombination (S), bulk recombination within the space-charge region (R-SCR), series resistance (Rs) and shunt resistance (Rsh), resulting in significant gaps between theoretical predictions and experimental results, with differences in JSC, VOC, or converter efficiency up to tenfold. To address this, a Practical Diode Model, integrating these practical characteristics, is developed via Monte Carlo and Physics-Based Compact Model Co-Simulation.We quantitatively analyze the differential impacts and synergistic effects of these practical characteristics on JSC, VOC, FF, and Pout, highlighting the detrimental effects of S, R-SCR, and Rs, while emphasizing the beneficial role of Rsh. Further analysis of the degree of influence of S, Rs, and Rsh on output power reveals a priority ranking order of Rs, S, and Rsh for Si-based batteries, and S, Rsh, and Rs for SiC-based batteries. This approach effectively bridges the theoretical-experimental gap, evidenced by J-V curves closely matching tested batteries and negligible relative errors of -0.8% to 0.6% between Pout values and their tested counterparts, emphasizing its accuracy in predictions. We predict output performance across material qualities, obtaining achievable powers of 16.82 and 73.90 nW/cm2 for planar Si- and SiC-based batteries, and evaluate the quality levels of existing batteries. Furthermore, our model can forecast the performance of 3D batteries by incorporating an extended electron-hole pair generation rate model into 3D structures, achieving 28 μW/cm3 for the 63Ni-Si-based multi-layer battery, surpassing planar silicon and suitable for MEMS applications.
Commenting
YES
Commenting
YES
Commenting
Subjects: Medicine, Pharmacy >> Preventive Medicine and Hygienics submitted time 2024-08-13
Abstract： Background Rheumatoid factor（RF）is a common autoantibody found in patients with primary Sjögren's syndrome（pSS），but its specific role in the disease is not fully understood. Objective To explore the clinical characteristics and significance of different RF levels in pSS. Methods This study included 262 pSS patients who visited the Department of Rheumatology of Traditional Chinese Medicine at China-Japan Friendship Hospital from December 2018 to September 2022.Patients were divided into three groups based on RF levels：negative group（RF<20 U/mL，n=137），low-titer positive group（RF：20-60 U/mL，n=47），and high-titer positive group（RF>60 U/mL，n=78）. Clinical data，including general information，clinical manifestations，symptom scores，and haematological indexes，were collected and analyzed using χ2 ，nonparametric test，and trend tests. Results The RF positivity rate in 262 pSS patients was 47.7%（125/262），including 14 males（5.3%）and 248 females（94.7%），with a median age of 57.0（49.0，63.0）years，an average age of onset of（48.7±11.6）years，and a median disease duration of 60.0（24.0，120.0）months. There were no significant differences in gender，age，age of onset，or disease duration among the three groups（P>0.05）. The top three common clinical manifestations in pSS patients were dry mouth（257 cases），dry eyes（247 cases），and fatigue（235 cases）. The incidence of haematological involvement and arthritis was higher in the high-titer positive group than in the negative group（P<0.05）. With the increase in RF titer，the incidence of haematological involvement（χ2 trend=6.992，Ptrend=0.008）and arthritis（χ2 trend=10.918，Ptrend=0.001）showed an upward trend. As RF titer increased，the proportions of pSS patients with antinuclear antibody ≥ 1 ∶ 160（χ2 trend=40.691，Ptrend<0.001），anti-SSA antibody positivity（χ2 trend=26.138，Ptrend<0.001），anti-Ro52 antibody positivity（χ2 trend=31.426，Ptrend<0.001），anti-SSB antibody positivity（χ2 trend=23.682，Ptrend<0.001），elevated erythrocyte sedimentation rate（χ2 trend=40.132，Ptrend<0.001），elevated immunoglobulin（Ig）A（χ2 trend=7.508，Ptrend=0.006），elevated IgG（χ2 trend=71.570，Ptrend<0.001），decreased complement 3（χ2 trend=7.452，Ptrend=0.006），decreased neutrophil count（χ2 trend=8.364，Ptrend=0.004），and decreased hemoglobin（χ2 trend=6.390，Ptrend=0.011）all showed an upward trend. Conclusion With the increase in RF titer，the proportion of pSS patients with serum immunological abnormalities and extra-glandular involvement increases. High RF titers have predictive value for arthritis and hematologic involvement.
Peer Review Status:Awaiting Review
Subjects: Medicine, Pharmacy >> Preventive Medicine and Hygienics submitted time 2024-08-13
Abstract： Background Given the increasing prevalence of the high incidence of bone and joint diseases in the elderly population，and significantly associated with higher mortality，more disability，decline in functional status and lower quality of life，this creates a large disease burden. There is currently no research on the prevalence and influencing factors of this disease in Henan Province. Objective To provide scientific basis for understanding the epidemic characteristics and influencing factors of bone and joint diseases in the elderly population in Henan Province and implementing precise prevention and control. Methods The multi-stage random cluster sampling method was used to obtain the demographic characteristics，past disease history，physical activity and physical indicators of permanent residents aged ≥ 18 years old in Henan Province in 2018 through questionnaires，medical physical examination，laboratory testing and other methods. 1 055 people aged≥ 60 years old were included in this study. Multivariate Logistic regression based on complex sampling was used to analyze the characteristics and influencing factors of bone and joint diseases in the elderly population with different characteristics in Henan Province. Results The incidence rate of bone and joint diseases among the elderly population in Henan Province in 2018 was 28.13%（95%CI=28.10%-28.15%）. Among them，women，urban areas，those with overweight or obesity，central obesity，dyslipidemia or hyperlipidemia，snoring history，moderate intensity activity，and non-smoking history have higher incidence rates，and the differences are statistically significant（P<0.05）. Multivariate Logistic regression analysis showed that males（OR=0.717，95%CI=0.550~0.933，P=0.013）were protective factors for bone and joint diseases in the elderly population，while overweight or obesity（OR=1.329，95%CI=1.050-1.684，P=0.018）and central obesity（OR=1.305，95%CI=1.047-1.626，P=0.018）were risk factors for bone and joint diseases in the elderly population. Conclusion Bone and joint diseases in the elderly population in Henan Province are related to gender，BMI，and central obesity. Targeted health education and comprehensive intervention should be carried out for women，overweight or obese individuals，and central obesity in the elderly population.
Peer Review Status:Awaiting Review
Subjects: Nuclear Science and Technology >> Radiation Physics and Technology submitted time 2024-07-29
Can Cheng
Yong-Ji Xie
Xun-Rong Xia
Jia-Yu Gu
Dong Zhao
Yi-Ze Chen
Ai-Yun Sun
Xu-Wen Liang
Wen-Bao Jia
Da-Qian Hei
Abstract： Neutron-induced gamma-ray imaging is a spectroscopic technique that uses characteristic gamma rays to infer the elemental distribution of an object. Currently, this technique requires the use of large facilities to supply a high neutron flux and a time-consuming detection procedure involving direct collimating measurements. In this study, a new method based on low neutron flux was proposed. A single-pixel gamma ray detector combined with random pattern gamma ray masks was used to measure the characteristic gamma rays emitted from the sample. Images of the elemental distribution in the sample, comprising 30 × 30 pixels, were reconstructed using the maximum-likelihood expectation-maximization algorithm. The results demonstrate that the elemental imaging of the sample can be accurately determined using this method. The proposed approach, which eliminates the need for high neutron flux and scanning measurements, can be used for in-field imaging applications.
Subjects: Astronomy >> Astrophysical processes submitted time 2023-02-19
Abstract： The Solar System's orbital structure is thought to have been sculpted by an episode of dynamical instability among the giant planets. However, the instability trigger and timing have not been clearly established. Hydrodynamical modeling has shown that while the Sun's gaseous protoplanetary disk was present the giant planets migrated into a compact orbital configuration in a chain of resonances. Here we use dynamical simulations to show that the giant planets' instability was likely triggered by the dispersal of the gaseous disk. As the disk evaporated from the inside-out, its inner edge swept successively across and dynamically perturbed each planet's orbit in turn. The associated orbital shift caused a dynamical compression of the exterior part of the system, ultimately triggering instability. The final orbits of our simulated systems match those of the Solar System for a viable range of astrophysical parameters. The giant planet instability therefore took place as the gaseous disk dissipated, constrained by astronomical observations to be a few to ten million years after the birth of the Solar System. Terrestrial planet formation would not complete until after such an early giant planet instability; the growing terrestrial planets may even have been sculpted by its perturbations, explaining the small mass of Mars relative to Earth.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Astrophysical processes submitted time 2023-02-19
Abstract： Building accurate and predictive models of the underlying mechanisms of celestial motion has inspired fundamental developments in theoretical physics. Candidate theories seek to explain observations and predict future positions of planets, stars, and other astronomical bodies as faithfully as possible. We use a data-driven learning approach, extending that developed in Lu et al. ($2019$) and extended in Zhong et al. ($2020$), to a derive stable and accurate model for the motion of celestial bodies in our Solar System. Our model is based on a collective dynamics framework, and is learned from the NASA Jet Propulsion Lab's development ephemerides. By modeling the major astronomical bodies in the Solar System as pairwise interacting agents, our learned model generate extremely accurate dynamics that preserve not only intrinsic geometric properties of the orbits, but also highly sensitive features of the dynamics, such as perihelion precession rates. Our learned model can provide a unified explanation to the observation data, especially in terms of reproducing the perihelion precession of Mars, Mercury, and the Moon. Moreover, Our model outperforms Newton's Law of Universal Gravitation in all cases and performs similarly to, and exceeds on the Moon, the Einstein-Infeld-Hoffman equations derived from Einstein's theory of general relativity.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Astrophysical processes submitted time 2023-02-19
Abstract： Presolar grains are microscopic dust grains that formed in the stellar winds or explosions of ancient stars that died before the formation of the solar system. The majority (~90% in number) of presolar silicon carbide (SiC) grains, including types mainstream (MS), Y, and Z, came from low-mass C-rich asymptotic giant branch (AGB) stars, which is supported by the ubiquitous presence of SiC dust observed in the circumstellar envelope of AGB stars and the signatures of slow neutron-capture process preserved in these grains. Here, we review the status of isotope studies of presolar AGB SiC grains with an emphasis on heavy-element isotopes and highlight the importance of presolar grain studies for nuclear astrophysics. We discuss the sensitives of different types of nuclei to varying AGB stellar parameters and how their abundances in presolar AGB SiC grains can be used to provide independent, detailed constraints on stellar parameters, including 13C formation, stellar temperature, and nuclear reaction rates.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Astrophysical processes submitted time 2023-02-19
Abstract： The exchange of a pair of neutrinos between two objects, seperated by a distance $r$, leads to a long-range effective potential proportional to $1/r_{}^5$, assuming massless neutrinos and four-fermion contact interactions. In this paper, we investigate how this known form of neutrino-mediated potentials might be altered if the distance $r$ is sufficiently short, corresponding to a sufficiently large momentum transfer which could invalidate the contact interactions. We consider two possible scenarios to open up the contact interactions by introducing a $t$-channel or an $s$-channel mediator. We derive a general formula that is valid to describe the potential in all regimes as long as the external particles remain non-relativistic. In both scenarios, the potential decreases as $1/r_{}^5$ in the long-range limit as expected. In the short-range limit, the $t$-channel potential exhibits the Coulomb-like behavior (i.e. proportional to $1/r$), while the $s$-channel potential exhibits $1/r_{}^4$ and $1/r_{}^2$ behaviors.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Astrophysical processes submitted time 2023-02-19
Abstract： Inverse mass cascade is a key feature of statistically steady state for self-gravitating collisionless dark matter flow (SG-CFD). Continuous mass transfer from small to large mass scales (inverse) is formulated. Direct effect of mass cascade on halo mass function is presented. Mass cascade is local, two-way, and asymmetric in mass space. Halos inherit/pass their mass from/to halos of similar size. Two regimes are identified: a propagation range with scale-independent rate of mass transfer and a deposition range with cascaded mass consumed to grow halos. Dimensional analysis leads to a power-law mass function in propagation range with a geometry exponent ${\lambda}$. A fundamental merging frequency $f_0{\sim}m_p^{\lambda-1}a^{-1}$ is identified, where $a$ is scale factor. Particle mass $m_p$ can be determined if that frequency is known. Rate of mass transfer ${\epsilon}_m{\sim}a^{-1}$ is independent of halo mass, a key feature of propagation range. Typical halos grow as $m_h{\sim}a^{3/2}$ and halo lifespan scales as ${\sim}m_h^{-\lambda}$. Chain reaction of mass cascade provides non-equilibrium dark matter flow a mechanism to continuously release energy and maximize entropy. Continuous injection of mass ("free radicals") at the smallest scale is required to sustain the everlasting inverse mass cascade such that total halo mass $M_h$ increases as $a^{1/2}$. These "radicals" might be directly generated at the smallest Planck scale or by a direct cascade from large to small scales. Entire mass cascade can be formulated by random walk in mass space, where halos migrate with an exponential distribution of waiting time. This results in a heterogeneous diffusion model, where Press-Schechter mass function can be fully derived without relying on any specific collapse models. A double-$\lambda$ mass function is proposed with different $\lambda$ for two ranges and agrees with N-body simulations.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Astrophysical processes submitted time 2023-02-19
Abstract： Measuring the Cosmic X-ray Background (CXB) is a key to understand the Active Galactic Nuclei population, their absorption distribution and their average spectra. However, hard X-ray instruments suffer from time-dependent backgrounds and cross-calibration issues. The uncertainty of the CXB normalization remain of the order of 20%. To obtain a more accurate measurement, the Monitor Vsego Neba (MVN) instrument was built in Russia but not yet launched to the ISS (arXiv:1410.3284). We follow the same ideas to develop a CXB detector made of four collimated spectrometers with a rotating obturator on top. The collimators block off-axis photons below 100 keV and the obturator modulates on-axis photons allowing to separate the CXB from the instrumental background. Our spectrometers are made of 20 mm thick CeBr$_{3}$ crystals on top of a SiPM array. One tube features a $\sim$20 cm$^2$ effective area and more energy coverage than MVN, leading to a CXB count rate improved by a factor of $\sim$10 and a statistical uncertainty $\sim$0.5% on the CXB flux. A prototype is being built and we are seeking for a launch opportunity.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Astrophysical processes submitted time 2023-02-19
Salvatore Ferrone
Paola Di Matteo
Alessandra Mastrobuono-Battisti
Misha Haywood
Owain N. Snaith
Marco Montouri
Sergey Khoperskov
David Valls-Gabaud
Abstract： We present the e-TidalGCs Project which aims at modeling and predicting the extra-tidal features surrounding all Galactic globular clusters for which 6D phase space information, masses and sizes are available (currently 159 globular clusters). We focus the analysis and presentation of the results on the distribution of extra-tidal material on the sky, and on the different structures found at different heliocentric distances. We emphasize the wide variety of morphologies found: beyond the canonical tidal tails, our models reveal that the extra-tidal features generated by globular clusters take a wide variety of shapes, from thin and elongated shapes, to thick, and complex halo-like structures. We also compare some of the most well studied stellar streams found around Galactic globular clusters to our model predictions, namely those associated to the clusters NGC 3201, NGC 4590, NGC 5466 and Pal 5. Additionally, we investigate how the distribution and extension in the sky of the simulated streams vary with the Galactic potential by making use of three different models, containing or not a central spheroid, or a stellar bar. Overall, our models predict that the mass lost by the current globular cluster population in the field from the last 5 Gyrs is between $0.3-2.1\times10^{7}M_{\odot}$, an amount comparable between 7-55 % of current mass. Most of this lost mass is found in the inner Galaxy, with the half-mass radius of this population being between 4-6 kpc. The outputs of the simulations will be publicly available, at a time when the ESA Gaia mission and complementary spectroscopic surveys are delivering exquisite data to which these models can be compared.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Astrophysical processes submitted time 2023-02-19
Abstract： Dark radiation (DR) is generally predicted in new physics scenarios that address fundamental puzzles of the Standard Model or tensions in the cosmological data. Cosmological data has the sensitivity to constrain not only the energy density of DR, but also whether it is interacting. In this paper, we present a systematic study of five types of interacting DR (free-streaming, fluid, decoupling, instantaneous decoupling, and recoupling DR) and their impact on cosmological observables. We modify the Boltzmann hierarchy to describe all these types of interacting DR under the relaxation time approximation. We, for the first time, robustly calculate the collision terms for recoupling scalar DR and provide a better estimation of the recoupling transition redshift. We demonstrate the distinct features of each type of DR on the CMB and matter power spectra. We perform MCMC scans using the Planck 2018 data and BAO data. Assuming no new physics in the SM neutrino sector, we find no statistically significant constraints on the couplings of DR, although there is a slight preference for a late transition redshift for instantaneous decoupling DR around recombination, and for the fluid-like limit of all the cases. The $\Delta N_{\rm eff}$ constraint varies marginally depending on the type of DR.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Astrophysical processes submitted time 2023-02-19
Abstract： Compact Obscured Nuclei (CONs) account for a significant fraction of the population of luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs). These galaxy nuclei are compact, with radii of 10-100~pc, with large optical depths at submm and far-infrared wavelengths, and characterized by vibrationally excited HCN emission. It is not known what powers the large luminosities of the CON host galaxies because of the extreme optical depths towards their nuclei. CONs represent an extreme phase of nuclear growth, hiding either a rapidly accreting supermassive black hole or an abnormal mode of star formation. Here we apply principal component analysis (PCA) tomography to high-resolution (0.06$^{\prime\prime}$) ALMA observations at frequencies 245 to 265~GHz of the nearby CON (59~Mpc) IC~860. PCA is a technique to unveil correlation in the data parameter space, and we apply it to explore the morphological and chemical properties of species in our dataset. The leading principal components reveal morphological features in molecular emission that suggest a rotating, infalling disk or envelope, and an outflow analogous to those seen in Galactic protostars. One particular molecule of astrochemical interest is methanimine (CH$_2$NH), a precursor to glycine, three transitions of which have been detected towards IC 860. We estimate the average CH$_2$NH column density towards the nucleus of IC~860 to be $\sim10^{17}$cm$^{-2}$, with an abundance exceeding $10^{-8}$ relative to molecular hydrogen, using the rotation diagram method and non-LTE radiative transfer models. This CH$_2$NH abundance is consistent with those found in hot cores of molecular clouds in the Milky Way. Our analysis suggests that CONs are an important stage of chemical evolution in galaxies, that are chemically and morphologically similar to Milky Way hot cores.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Astrophysical processes submitted time 2023-02-19
Christopher J. White
Patrick D. Mullen
Yan-Fei Jiang
Shane W. Davis
James M. Stone
Viktoriya Morozova
Lizhong Zhang
Abstract： We extend the general-relativistic magnetohydrodynamics (GRMHD) capabilities of Athena++ to incorporate radiation. The intensity field in each finite-volume cell is discretized in angle, with explicit transport in both space and angle properly accounting for the effects of gravity on null geodesics, and with matter and radiation coupled in a locally implicit fashion. Here we describe the numerical procedure in detail, verifying its correctness with a suite of tests. Motivated in particular by black hole accretion in the high-accretion-rate, thin-disk regime, we demonstrate the application of the method to this problem. With excellent scaling on flagship computing clusters, the port of the algorithm to the GPU-enabled AthenaK code now allows the simulation of many previously intractable radiation-GRMHD systems.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Astrophysical processes submitted time 2023-02-19
Abstract： Supernova (SN) cosmology is based on the assumption that the width-luminosity relation (WLR) and the color-luminosity relation (CLR) in the type Ia SN luminosity standardization would not show {absolute magnitude differences} with progenitor age. Unlike this expectation, recent age datings of stellar populations in host galaxies have shown significant correlations between progenitor age and Hubble residual (HR). Here we show that this correlation originates from a strong progenitor age dependence of the zero-points of the WLR and the CLR, in the sense that SNe from younger progenitors are fainter each at given light-curve parameters $x_1$ and $c$. This $4.6\sigma$ result is reminiscent of Baade's discovery of the zero-point variation of the Cepheid period-luminosity relation with age, and, as such, causes a serious systematic bias with redshift in SN cosmology. Other host properties show substantially smaller and insignificant offsets in the WLR and CLR for the same dataset. We illustrate that the differences between the high-$z$ and low-$z$ SNe in the WLR and CLR, and in HR after the standardization, are fully comparable to those between the correspondingly young and old SNe at intermediate redshift, indicating that the observed dimming of SNe with redshift may well be an artifact of over-correction in the luminosity standardization. When this systematic bias with redshift is properly taken into account, there is little evidence left for an accelerating universe, in discordance with other probes, urging the follow-up investigations with larger samples at different redshift bins.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Astrophysical processes submitted time 2023-02-19
Abstract： We develop a framework for using clustering-based redshift inference (cluster-$z$) to measure the evolving galaxy luminosity function (GLF) and galaxy stellar mass function (GSMF) using WISE W1 ($3.4\mu m$) mid-infrared photometry and positions. We use multiple reference sets from the Galaxy And Mass Assembly (GAMA) survey, Sloan Digital Sky Survey (SDSS) and Baryon Oscillation Spectroscopic Survey (BOSS). Combining the resulting cluster-$z$s allows us to enlarge the study area, and by accounting for the specific properties of each reference set, making best use of each reference set to produce the best overall result. Thus we are able to measure the GLF and GSMF over $\sim 7500\, \mathrm{deg}^2 $ of the Northern Galactic Cap (NGC) up to $z<0.6$. Our method can easily be adapted for new studies with fainter magnitudes, which pose difficulties for the derivation of photo-$z$s. The measurement of the GSMF is currently limited by the models for k-corrections and mass-to-light ratios, rather than more complicated effects tied to the evolution of the differential galaxy bias. With better statistics in future surveys this technique is a strong candidate for studies with new emerging data from, e.g. the Vera C. Rubin Observatory, the Euclid mission or the Nancy Grace Roman Space Telescope.
Peer Review Status:Awaiting Review
Hits
Date
Hits
Downloads
Comment