分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: With Gaia EDR3 data, velocity dispersion of Milky Way field stars around satellite galaxies have been investigated. We have fitted velocity dispersion against distance to satellite galaxy and found the gradient of velocity dispersion is related to the mass of satellite galaxy. With order-of-magnitude approximations, a linear correlation has been fitted between the mass of satellite galaxy and gradient of velocity dispersion caused by its gravitational drag. Though our result is an observational qualitative result, it shows better relation could be obtained with more observations in the future.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: Recent studies illustrate the correlation between the angular momenta of cosmic structures and their Lagrangian properties. However, only baryons are observable and it is unclear whether they reliably trace the cosmic angular momenta. We study the Lagrangian mass distribution, spin correlation, and predictability of dark matter, gas, and stellar components of galaxy-halo systems using IllustrisTNG, and show that the primordial segregations between components are typically small. Their protoshapes are also similar in terms of the statistics of moment of inertia tensors. Under the common gravitational potential they are expected to exert the same tidal torque and the strong spin correlations are not destroyed by the nonlinear evolution and complicated baryonic effects, as confirmed by the high-resolution hydrodynamic simulations. We further show that their late-time angular momenta traced by total gas, stars, or the central galaxies, can be reliably reconstructed by the initial perturbations. These results suggest that baryonic angular momenta can potentially be used in reconstructing the parameters and models related to the initial perturbations.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We present a novel method to accurately measure the galaxy stellar mass function (GSMF) based upon the Photometric objects Around Cosmic webs (PAC) method developed in our first paper (Paper I) of the series. The method allows us to measure the GSMF to a lower mass end that is not accessible to the spectroscopic sample used in the PAC. Compared with Paper I, the current measurement of GSMF is direct and model independent. We measure the GSMFs in the redshift ranges of $z_s10^{10.6} M_{\odot}$, and that there is a clear up-turn at $M_*\approx 10^{9.5} M_{\odot}$ towards smaller galaxies in the local GMSF at $z_s=0.1$. We provide an accurate double Schechter fit to the local GSMF for the entire range of $M_*$ and a table of our measurements at the three redshifts, which can used to test theories of galaxy formation. Our method can achieve an accurate measurement of GSMF to the stellar mass limit where the spectroscopic sample is already highly incomplete (e.g. $\sim 10^{-3}$) for its target selection.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: Taking advantage of the Photometric objects Around Cosmic webs (PAC) method
developed in Paper I, we measure the excess surface density
$\bar{n}_2w_{{\rm{p}}}$ of photometric objects around spectroscopic objects
down to stellar mass $10^{8.0}M_{\odot}$, $10^{9.2}M_{\odot}$ and
$10^{9.8}M_{\odot}$ in the redshift ranges of $z_s<0.2$, $0.2
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: Some repeating fast radio burst (FRB) sources show high burst rates, and the physical origin is still unknown. Outstandingly, the first repeater FRB 121102 appears extremely high burst rate with the maximum value reaching $122\,\mathrm{h^{-1}}$ or even higher. In this work, we propose that the high burst rate of an FRB repeater may be due to plate collisions in the crust of young neutron stars (NSs). In the crust of an NS, vortex lines are pinned to the lattice nuclei. When the relative angular velocity between the superfluid neutrons and the NS lattices is nonzero, a pinned force will act on the vortex lines, which will cause the lattice displacement and the strain on the NS crust growing. With the spin evolution, the crustal strain reaches a critical value, then the crust may crack into plates, and each of plates will collide with its adjacent ones. The Aflv\'en wave could be launched by the plate collisions and further produce FRBs. In this scenario, the predicted burst rate can reach $\sim 770\,\mathrm{h}^{-1}$ for an NS with the magnetic field of $10^{13}\,\rm{G}$ and the spin period of $0.01\,\rm{s}$. We further apply this model to FRB 121102, and predict the waiting time and energy distribution to be $P(t_{\mathrm{w}}) \propto t_{\text{w}}^{\alpha_{t_{\text{w}}}}$ with $\alpha_{t_{\text{w}}} \simeq -1.75$ and $N(E)\text{d}E \propto E^{\alpha_{E}}\text{d}E$ with $\alpha_{E} \simeq -1.67$, respectively. These properties are consistent with the observations of FRB 121102.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: In this paper, we report a robust measurement of the morphology, color and galaxy size dependences of the stellar-halo mass relation (SHMR) at the high mass end ($10^{11.3}{\rm M_{\odot}}6$) have the halo mass around 5.5 times larger than the disk galaxies ($n<2$). Similarly, using the effective radius $R_e$ and the rest-frame $u-r$ color, we find that red (large) galaxies reside in halos that are in average $2.6$ ($2.3$) times more massive than those hosting blue (small) galaxies.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We present a two-dimensional (2D) Particle-Particle-Particle-Mesh (P$^3$M) algorithm with an optimized Green function and adaptive softening length for gravitational lensing studies in N-Body simulations. The analytical form of the optimized Green function $\hat{G}(\rm{k})$ is given. The softening schemes ($S$) are studied for both the PM and the PP calculations in order for accurate force calculation and suppression of the particle discreteness effect. Our method is two orders of magnitude more accurate than the simple PM algorithm with the {\it poor man's} Green function ($\propto1/k^2$) at a scale of a few mesh cells or smaller. The force anisotropy is also much smaller than the conventional PM calculation. We can achieve a force accuracy better than 0.1 percent at all scales with our algorithm, which makes it an ideal (accurate and fast) algorithm for {\textit{micro}} lensing studies . When we apply the algorithm to computing {\textit{weak}} and {\textit{strong}} lensing quantities in N-Body simulations, the errors are dominated by the Poisson noise caused by particle discreteness. The Poisson noise can be suppressed by smoothing out the particle distribution, which can be achieved by simply choosing an adaptive softening length in the PP calculation. We have presented a criterion to set the adaptive softening length. Our algorithm is also applicable to cosmological simulations. We provide a \textsc{python} implementation \texttt{P3Mlens} for this algorithm.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We present a novel method to accurately measure the galaxy stellar mass function (GSMF) based upon the Photometric objects Around Cosmic webs (PAC) method developed in our first paper (Paper I) of the series. The method allows us to measure the GSMF to a lower mass end that is not accessible to the spectroscopic sample used in the PAC. Compared with Paper I, the current measurement of GSMF is direct and model independent. We measure the GSMFs in the redshift ranges of $z_s10^{10.6} M_{\odot}$, and that there is a clear up-turn at $M_*\approx 10^{9.5} M_{\odot}$ towards smaller galaxies in the local GMSF at $z_s=0.1$. We provide an accurate double Schechter fit to the local GSMF for the entire range of $M_*$ and a table of our measurements at the three redshifts, which can used to test theories of galaxy formation. Our method can achieve an accurate measurement of GSMF to the stellar mass limit where the spectroscopic sample is already highly incomplete (e.g. $\sim 10^{-3}$) for its target selection.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: The frequency-dependent periodic active window of the fast radio burst FRB 180916.J0158+65 (FRB 180916B) was observed recently. In this Letter, we propose that a Be/X-ray binary (BeXRB) system, which is composed of a neutron star (NS) and a Be star with a circumstellar disk, might be the source of a repeating FRB with periodic activities, and apply this model to explain the activity window of FRB 180916B. The interaction between the NS magnetosphere and the accreted material results in evolution of the spin period and the centrifugal force of the NS, leading to the change of the stress in the NS crust. When the stress of the crust reaches the critical value, a starquake occurs and further produces FRBs. The interval between starquakes is estimated to be a few days that is smaller than the active window of FRB 180916B. When the NS moves out of the disk of the Be star, the interval between starquakes becomes much longer than the orbital period, which corresponds to the non-active phase. In this model, due to the absorption of the disk of the Be star, a frequency-dependent active window would appear for the FRBs, which is consistent with the observed properties of FRB 180916B. And the contribution of dispersion measure (DM) from the disk of the Be star is small. In addition, the location of FRB 180916B in the host galaxy is consistent with a BeXRB system.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We measure the galaxy-ellipticity (GI) correlations for the Slogan Digital Sky Survey DR12 LOWZ and CMASS samples with the shape measurements from the DESI Legacy Imaging Surveys. We model the GI correlations in an N-body simulation with our recent accurate stellar-halo mass relation from the Photometric object Around Cosmic webs (PAC) method. The large data set and our accurate modeling turns out an accurate measurement of the alignment angle between central galaxies and their host halos. We find that the alignment of central elliptical galaxies with their host halos increases monotonically with galaxy stellar mass or host halo mass, which can be well described by a power law for the massive galaxies. We also find that central elliptical galaxies are more aligned with their host halos when they evolve to a lower redshift. In contrast, central disk galaxies are aligned with their host halos about 10 times more weakly in the GI correlation. These results have important implications for intrinsic alignment (IA) correction in weak lensing studies, IA cosmology, and theory of massive galaxy formation.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: Taking advantage of the Photometric objects Around Cosmic webs (PAC) method
developed in Paper I, we measure the excess surface density
$\bar{n}_2w_{{\rm{p}}}$ of photometric objects around spectroscopic objects
down to stellar mass $10^{8.0}M_{\odot}$, $10^{9.2}M_{\odot}$ and
$10^{9.8}M_{\odot}$ in the redshift ranges of $z_s<0.2$, $0.2
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We investigate the [O\,II] emission line galaxy (ELG)-host halo connection via auto and cross correlations, and propose a concise and effective method to populate ELGs in dark matter halos without assuming a parameterized halo occupation distribution (HOD) model. Using the observational data from VIMOS Public Extragalactic Redshift Survey (VIPERS), we measure the auto and cross correlation functions between ELGs selected by [O\,II] luminosity and normal galaxies selected by stellar mass. Combining the stellar-halo mass relation (SHMR) derived for the normal galaxies and the fraction of ELGs observed in the normal galaxy population, we demonstrate that we can establish an accurate ELG-halo connection. With the ELG-halo connection, we can accurately reproduce the auto and cross correlation functions of ELGs and normal galaxies both in real-space and in redshift-space, once the satellite fraction is properly reduced. Our method provides a novel strategy to generate ELG mock catalogs for ongoing and upcoming galaxy redshift surveys. We also provide a simple description for the HOD of ELGs.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We measure the galaxy-ellipticity (GI) correlations for the Slogan Digital Sky Survey DR12 LOWZ and CMASS samples with the shape measurements from the DESI Legacy Imaging Surveys. We model the GI correlations in an N-body simulation with our recent accurate stellar-halo mass relation from the Photometric object Around Cosmic webs (PAC) method. The large data set and our accurate modeling turns out an accurate measurement of the alignment angle between central galaxies and their host halos. We find that the alignment of central elliptical galaxies with their host halos increases monotonically with galaxy stellar mass or host halo mass, which can be well described by a power law for the massive galaxies. We also find that central elliptical galaxies are more aligned with their host halos when they evolve to a lower redshift. In contrast, central disk galaxies are aligned with their host halos about 10 times more weakly in the GI correlation. These results have important implications for intrinsic alignment (IA) correction in weak lensing studies, IA cosmology, and theory of massive galaxy formation.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: We provide a method for estimating the projected density distribution $\bar{n}_2w_p(r_p)$ of photometric objects around spectroscopic objects in a redshift survey. This quantity describes the distribution of Photometric sources with certain physical properties (e.g. luminosity, mass, color etc) Around Cosmic webs (PAC) traced by the spectroscopic objects. The method can make full use of current and future deep and wide photometric surveys to explore the formation of galaxies up to medium redshift ($z_s < 2$), with the aid of cosmological redshift surveys that sample only a fairly limited species of objects (e.g. Emission Line Galaxies). As an example, we apply the PAC method to the CMASS spectroscopic and HSC-SSP PDR2 photometric samples to explore the distribution of galaxies for a wide range of stellar mass from $10^{9.0}{\rm M_\odot}$ to $10^{12.0}{\rm M_\odot}$ around massive ones at $z_s\approx 0.6$. Using the abundance matching method, we model $\bar{n}_2w_p(r_p)$ in N-body simulation using MCMC sampling, and accurately measure the stellar-halo mass relation (SHMR) and stellar mass function (SMF) for the whole mass range. We can also measure the conditional stellar mass function (CSMF) of satellites for central galaxies of different mass. The PAC method has many potential applications for studying the evolution of galaxies.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: Recent studies illustrate the correlation between the angular momenta of cosmic structures and their Lagrangian properties. However, only baryons are observable and it is unclear whether they reliably trace the cosmic angular momenta. We study the Lagrangian mass distribution, spin correlation, and predictability of dark matter, gas, and stellar components of galaxy-halo systems using IllustrisTNG, and show that the primordial segregations between components are typically small. Their protoshapes are also similar in terms of the statistics of moment of inertia tensors. Under the common gravitational potential they are expected to exert the same tidal torque and the strong spin correlations are not destroyed by the nonlinear evolution and complicated baryonic effects, as confirmed by the high-resolution hydrodynamic simulations. We further show that their late-time angular momenta traced by total gas, stars, or the central galaxies, can be reliably reconstructed by the initial perturbations. These results suggest that baryonic angular momenta can potentially be used in reconstructing the parameters and models related to the initial perturbations.
分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: Wavelength-tunable vortex fiber lasers that could generate beams carrying orbital angular momentum (OAM) hold great interest in large-capacity optical communications. The wavelength tunability of conventional vortex fiber lasers is however limited by the range of 35 nm due to narrow bandwidth and/or insertion loss of mode conversion components. Optical metasurfaces apart from being compact planar components can flexibly manipulate light with high efficiency in a broad wavelength range. Here, we propose and demonstrate for the first time, to the best of our knowledge, a metasurface-assisted vortex fiber laser that can directly generate OAM beams with changeable topological charges. Due to the designed broadband gap-surface plasmon metasurface, combined with an intracavity tunable filter, the laser enables OAM beam with center wavelength continuously tunable from 1015 nm to 1075 nm, nearly twice of other vortex fiber lasers ever reported. The metasurface can be designed at will to satisfy requirements for either low pump threshold or high slope efficiency of the laser. Furthermore, the cavity-metasurface configuration can be extended to generate higher-order OAM beams or more complex structured beams in different wavelength regions, which greatly broadens the possibilities for developing low-cost and high-quality structured-beam laser sources.
分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: Breathers are localized structures that undergo a periodic oscillation in their duration and amplitude. Optical microresonators, benefiting from their high quality factor, provide an ideal test bench for studying the breathing phenomena. In the monochromatically pumped microresonator system, intrinsic breathing instabilities are widely observed in the form of temporal dissipative Kerr solitons which only exist in the effectively red detuned regime. Here, we proposed a novel bichromatic pumping scheme to create compulsive breathing microcombs via respectively distributing two pump lasers at the effectively blue and red detuned side of a single resonance. We experimentally discover the artificial cnoidal wave breathers and molecular crystal-like breathers in a chip-based silicon nitride microresonator, and theoretically describe their intriguing temporal dynamics based on the bichromatic pumping Lugiato-Lefever equation. In particular, the corresponding breathing microcombs exhibit diverse comb line spacing ranging from 2 to 17 times of the free spectral range of the resonator. Our discovery not only provides a simple and robust method to produce microcombs with reconfigurable comb line spacing, but also reveals a new type of breathing waves in driven dissipative nonlinear systems.
分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: Optical neural networks (ONNs), or optical neuromorphic hardware accelerators, have the potential to dramatically enhance the computing power and energy efficiency of mainstream electronic processors, due to their ultralarge bandwidths of up to 10s of terahertz together with their analog architecture that avoids the need for reading and writing data back and forth. Different multiplexing techniques have been employed to demonstrate ONNs, amongst which wavelength division multiplexing (WDM) techniques make sufficient use of the unique advantages of optics in terms of broad bandwidths. Here, we review recent advances in WDM based ONNs, focusing on methods that use integrated microcombs to implement ONNs. We present results for human image processing using an optical convolution accelerator operating at 11 Tera operations per second. The open challenges and limitations of ONNs that need to be addressed for future applications are also discussed.