分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： In this work, we propose new statistical tools that are capable of characterizing the simultaneous dependence of dark matter and gas clustering on the scale and the density environment, and these are the environment-dependent wavelet power spectrum (env-WPS), the environment-dependent bias function (env-bias), and the environment-dependent wavelet cross-correlation function (env-WCC). These statistics are applied to the dark matter and baryonic gas density fields of the \texttt{TNG100-1} simulation at redshifts of $z=3.0$-$0.0$, and to \texttt{Illustris-1} and \texttt{SIMBA} at $z=0$. The measurements of the env-WPSs suggest that the clustering strengths of both the dark matter and the gas increase with increasing density, while that of a Gaussian field shows no density dependence. By measuring the env-bias and env-WCC, we find that they vary significantly with the environment, scale, and redshift. A noteworthy feature is that at $z=0.0$, the gas is less biased in denser environments of $\Delta \gtrsim 10$ around $3 \ h\mathrm{Mpc}^{-1}$, due to the gas reaccretion caused by the decreased AGN feedback strength at lower redshifts. We also find that the gas correlates more tightly with the dark matter in both the most dense and underdense environments than in other environments at all epochs. Even at $z=0$, the env-WCC is greater than $0.9$ in $\Delta \gtrsim 200$ and $\Delta \lesssim 0.1$ at scales of $k \lesssim 10 h\mathrm{Mpc}^{-1}$. In summary, our results support the local density environment having a non-negligible impact on the deviations between dark matter and gas distributions up to large scales.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The continuous wavelet transform (CWT) is very useful for processing signals with intricate and irregular structures in astrophysics and cosmology. It is crucial to propose precise and fast algorithms for the CWT. In this work, we review and compare four different fast CWT algorithms for the 1D signals, including the FFTCWT, the V97CWT, the M02CWT, and the A19CWT. The FFTCWT algorithm implements the CWT using the Fast Fourier Transform (FFT) with a computational complexity of $\mathcal{O}(N\log_2N)$ per scale. The rest algorithms achieve the complexity of $\mathcal{O}(N)$ per scale by simplifying the CWT into some smaller convolutions. We illustrate explicitly how to set the parameters as well as the boundary conditions for them. To examine the actual performance of these algorithms, we use them to perform the CWT of signals with different wavelets. From the aspect of accuracy, we find that the FFTCWT is the most accurate algorithm, though its accuracy degrades a lot when processing the non-periodic signal with zero boundaries. The accuracy of $\mathcal{O}(N)$ algorithms is robust to signals with different boundaries, and the M02CWT is more accurate than the V97CWT and A19CWT. From the aspect of speed, the $\mathcal{O}(N)$ algorithms do not show an overall speed superiority over the FFTCWT at sampling numbers of $N\lesssim10^6$, which is due to their large leading constants. Only the speed of the V97CWT with real wavelets is comparable to that of the FFTCWT. However, both the FFTCWT and V97CWT are substantially less efficient in processing the non-periodic signal because of zero padding. Finally, we conduct wavelet analysis of the 1D density fields, which demonstrate the convenience and power of techniques based on the CWT. We publicly release our CWT codes as resources for the community.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The continuous wavelet transform (CWT) is very useful for processing signals with intricate and irregular structures in astrophysics and cosmology. It is crucial to propose precise and fast algorithms for the CWT. In this work, we review and compare four different fast CWT algorithms for the 1D signals, including the FFTCWT, the V97CWT, the M02CWT, and the A19CWT. The FFTCWT algorithm implements the CWT using the Fast Fourier Transform (FFT) with a computational complexity of $\mathcal{O}(N\log_2N)$ per scale. The rest algorithms achieve the complexity of $\mathcal{O}(N)$ per scale by simplifying the CWT into some smaller convolutions. We illustrate explicitly how to set the parameters as well as the boundary conditions for them. To examine the actual performance of these algorithms, we use them to perform the CWT of signals with different wavelets. From the aspect of accuracy, we find that the FFTCWT is the most accurate algorithm, though its accuracy degrades a lot when processing the non-periodic signal with zero boundaries. The accuracy of $\mathcal{O}(N)$ algorithms is robust to signals with different boundaries, and the M02CWT is more accurate than the V97CWT and A19CWT. From the aspect of speed, the $\mathcal{O}(N)$ algorithms do not show an overall speed superiority over the FFTCWT at sampling numbers of $N\lesssim10^6$, which is due to their large leading constants. Only the speed of the V97CWT with real wavelets is comparable to that of the FFTCWT. However, both the FFTCWT and V97CWT are substantially less efficient in processing the non-periodic signal because of zero padding. Finally, we conduct wavelet analysis of the 1D density fields, which demonstrate the convenience and power of techniques based on the CWT. We publicly release our CWT codes as resources for the community.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The wavelet analysis technique is a powerful tool and is widely used in broad disciplines of engineering, technology, and sciences. In this work, we present a novel scheme of constructing continuous wavelet functions, in which the wavelet functions are obtained by taking the first derivative of smoothing functions with respect to the scale parameter. Due to this wavelet constructing scheme, the inverse transforms are only one-dimensional integrations with respect to the scale parameter, and hence the continuous wavelet transforms constructed in this way are more ready to use than the usual scheme. We then apply the Gaussian-derived wavelet constructed by our scheme to computations of the density power spectrum for dark matter, the velocity power spectrum and the kinetic energy spectrum for baryonic fluid. These computations exhibit the convenience and strength of the continuous wavelet transforms. The transforms are very easy to perform, and we believe that the simplicity of our wavelet scheme will make continuous wavelet transforms very useful in practice.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The High Latitude Spectroscopic Survey (HLSS) is the reference baseline spectroscopic survey for NASA's Nancy Grace Roman space telescope, measuring redshifts of $\sim 10$M H$\alpha$ emission line galaxies over a $2000$ deg$^2$ footprint at $z=1-2$. In this work, we use a realistic Roman galaxy mock catalogue to explore optimal modeling of the measured power spectrum. We consider two methods for modelling the redshift-space distortions (one with the canonical Kaiser squashing term $M_A$, and another with a window function on $\beta$ that selects out the coherent radial infall pairwise velocities $M_B$), two models for the nonlinear impact of baryons that smears the BAO signal (one with a fixed ratio between the smearing scales in the perpendicular $k_*^\perp$ and parallel $k_*^\parallel$ and another where these smearing scales are kept as a free parameters, P$_{dw}(k|k_*)$ and P$_{dw}(k|\Sigma_\perp,\Sigma_\parallel)$), and two analytical nonlinear growth corrections (one employing the halo model $F_{HM}$ and another formulated from simulated galaxy clustering of a semi-analytical model $F_{SAM}$). We find that the best model is P$_{dw}(k|\Sigma_\perp,\Sigma_\parallel)*M_B$, which leads to unbiased measurements of cosmological parameters. We expect the tools that we have developed to be useful in probing dark energy and testing gravity using Roman in an accurate and robust manner.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Continuous wavelet analysis has been increasingly employed in various fields of science and engineering due to its remarkable ability to maintain optimal resolution in both space and scale. Here, we introduce wavelet-based statistics, including the wavelet power spectrum, wavelet cross-correlation and wavelet bicoherence, to analyze the large-scale clustering of matter. For this purpose, we perform wavelet transforms on the density distribution obtained from the one-dimensional Zel'dovich approximation and then measure the wavelet power spectra and wavelet bicoherences of this density distribution. Our results suggest that the wavelet power spectrum and wavelet bicoherence can identify the effects of local environments on the clustering at different scales. Moreover, we apply the statistics based on the three-dimensional isotropic wavelet to the IllustrisTNG simulation at z = 0, and investigate the environmental dependence of the matter clustering. We find that the clustering strength of the total matter increases with increasing local density except on the largest scales. Besides, we notice that the gas traces the dark matter better than stars on large scales in all environments. On small scales, the cross-correlation between the dark matter and gas first decreases and then increases with increasing density. This is related to the impacts of the AGN feedback on the matter distribution, which also varies with the density environment in a similar trend to the cross-correlation between the dark matter and gas. Our findings are qualitatively consistent with previous studies about the matter clustering.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We investigate the dynamics and electromagnetic (EM) signatures of neutron star-neutron star (NS-NS) or neutron star-black hole (NS-BH) merger ejecta that occurs in the accretion disk of an active galactic nucleus (AGN). We find that the interaction between ejecta and disk gas leads to important effects on the dynamics and radiation. We show five stages of the ejecta dynamics: gravitational slowing down, coasting, Sedov-Taylor deceleration in the disk, re-acceleration after the breakout from the disk surface, and momentum-conserved snowplow phase. Meanwhile, the radiation from the ejecta is so bright that its typical peak luminosity reaches a few times $10^{43}-10^{44}~\rm erg~s^{-1}$. Since most of the radiation energy has converted from the kinetic energy of merger ejecta, we call such an explosive phenomenon an interacting kilonova (IKN). It should be emphasized that IKNe are very promising, bright EM counterparts to NS-NS/BH-NS merger events in AGN disks. The bright peak luminosity and long rising time (i.e., ten to twenty days in UV bands, thirty to fifty days in optical bands, and one hundred days to hundreds of days in IR bands) allow most survey telescopes to have ample time to detect an IKN. However, the peak brightness, peak time, and evolution pattern of the light curve of an IKN are similar to a superluminous supernova in a galactic nucleus and a tidal disruption event making it difficult to distinguish between them. But it also suggests that IKNe might have been present in recorded AGN transients.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We investigate the dynamics and electromagnetic (EM) signatures of neutron star-neutron star (NS-NS) or neutron star-black hole (NS-BH) merger ejecta that occurs in the accretion disk of an active galactic nucleus (AGN). We find that the interaction between ejecta and disk gas leads to important effects on the dynamics and radiation. We show five stages of the ejecta dynamics: gravitational slowing down, coasting, Sedov-Taylor deceleration in the disk, re-acceleration after the breakout from the disk surface, and momentum-conserved snowplow phase. Meanwhile, the radiation from the ejecta is so bright that its typical peak luminosity reaches a few times $10^{43}-10^{44}~\rm erg~s^{-1}$. Since most of the radiation energy has converted from the kinetic energy of merger ejecta, we call such an explosive phenomenon an interacting kilonova (IKN). It should be emphasized that IKNe are very promising, bright EM counterparts to NS-NS/BH-NS merger events in AGN disks. The bright peak luminosity and long rising time (i.e., ten to twenty days in UV bands, thirty to fifty days in optical bands, and one hundred days to hundreds of days in IR bands) allow most survey telescopes to have ample time to detect an IKN. However, the peak brightness, peak time, and evolution pattern of the light curve of an IKN are similar to a superluminous supernova in a galactic nucleus and a tidal disruption event making it difficult to distinguish between them. But it also suggests that IKNe might have been present in recorded AGN transients.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The delayed GeV$-$TeV cascade emission from extragalactic TeV$-$PeV sources are regarded as an ideal probe of the inter-galactic magnetic fields. Recently, LHAASO has detected $\sim 10$ TeV emission of the extraordinary powerful GRB 221009A within $\sim 2000$ s after the burst. Here we report the detection of a $\sim 400$ GeV photon, without accompanying prominent low-energy emission, by Fermi-LAT in the direction of GRB 221009A with the time delay of 0.4 days. Such a hard spectrum can be generated from electromagnetic cascades initiated by early primary $\sim 10$ TeV photons in the intergalactic space. An inter-galactic magnetic field strength of $B_{\rm IGMF}\sim 4 \times 10^{-17}$ G, comparable to limits from TeV blazars, can naturally account for the arrival time of the $\sim 400$ GeV photon as well as the HAWC non-detection. Such a strength will be stringently tested by the upcoming CTA.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We present measurements of the linear galaxy bias of H$\alpha$ and [OIII]
emission line galaxies (ELGs) for the High Latitude Spectroscopic Survey (HLSS)
of Nancy Grace Roman Space Telescope, using galaxy mocks constructed using
semi-analytical model for galaxy formation, {\it Galacticus}, with a large
cosmic volume and redshift coverage. We compute the two-point statistics of
galaxies in configuration space and measure linear bias within scales of
$10\sim50 h^{-1}$Mpc. We adopt different selection algorithms to investigate
the impact of the Roman line flux cut, as well as the effect of dust model used
to calibrate Galacticus, on the bias measurements. We consider galaxies with
H$\alpha$ and [OIII] emissions over the redshift range $1
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The delayed GeV$-$TeV cascade emission from extragalactic TeV$-$PeV sources are regarded as an ideal probe of the inter-galactic magnetic fields. Recently, LHAASO has detected $\sim 10$ TeV emission of the extraordinary powerful GRB 221009A within $\sim 2000$ s after the burst. Here we report the detection of a $\sim 400$ GeV photon, without accompanying prominent low-energy emission, by Fermi-LAT in the direction of GRB 221009A with the time delay of 0.4 days. Such a hard spectrum can be generated from electromagnetic cascades initiated by early primary $\sim 10$ TeV photons in the intergalactic space. An inter-galactic magnetic field strength of $B_{\rm IGMF}\sim 4 \times 10^{-17}$ G, comparable to limits from TeV blazars, can naturally account for the arrival time of the $\sim 400$ GeV photon as well as the HAWC non-detection. Such a strength will be stringently tested by the upcoming CTA.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The spatial distribution between dark matter and baryonic matter of the Universe is biased or deviates from each other. In this work, by comparing the results derived from IllustrisTNG and WIGEON simulations, we find that many results obtained from TNG are similar to those from WIGEON data, but differences between the two simulations do exist. For the ratio of density power spectrum between dark matter and baryonic matter, as scales become smaller and smaller, the power spectra for baryons are increasingly suppressed for WIGEON simulations; while for TNG simulations, the suppression stops at $k=15-20h{\rm Mpc}^{-1}$, and the power spectrum ratios increase when $k>20h{\rm Mpc}^{-1}$. The suppression of power ratio for WIGEON is also redshift-dependent. From $z=1$ to $z=0$, the power ratio decreases from about 70% to less than 50% at $k=8h{\rm Mpc}^{-1}$. For TNG simulation, the suppression of power ratio is enhanced with decreasing redshifts in the scale range $k>4h{\rm Mpc}^{-1}$, but is nearly unchanged with redshifts in $k<4h{\rm Mpc}^{-1}$ These results indicate that turbulent heating can also have the consequence to suppress the power ratio between baryons and dark matter. Regarding the power suppression for TNG simulations as the norm, the power suppression by turbulence for WIGEON simulations is roughly estimated to be 45% at $k=2h{\rm Mpc}^{-1}$, and gradually increases to 69% at $k=8h{\rm Mpc}^{-1}$, indicating the impact of turbulence on the cosmic baryons are more significant on small scales.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We simulate the emission line galaxy properties for the Nancy Grace Roman Space Telescope by creating a 4 deg$^{2}$ galaxy mock catalog using Galacticus, a semi-analytic model (SAM) for galaxy formation and evolution. The simulated galaxy properties include emission line luminosity, equivalent width (EW), broad band photometry, and spectral energy distribution (SED). We compare this mock catalog with the latest observational data from WISP and MOSDEF. We find that our Galacticus model makes predictions consistent with observational data, over a wide redshift range for multiple emission lines. We use this validated galaxy mock catalog to forecast the photometric completeness of H$\alpha$ and [OIII] emission lines as a function of line flux cut and H band magnitdue cut, for both Roman and Euclid-like surveys. Our prediction for the photometric completeness of a Euclid-like survey is in good agreement with previous work based on WISP data. Our predictions for the photometric completeness of possible implementations of the Roman High Latitude Wide Area Spectroscopic Survey (HLWASS) provides key input for the planning of such a survey. We find that at H = 24, a Euclid-like survey to the line flux limit of 2$\times 10^{-16}\,$erg/s/cm$^2$ is 97\% complete, while a Roman HLWASS to the line flux limit of $10^{-16}\,$erg/s/cm$^2$ is only 94.6\% complete (it becomes 98\% complete at H = 25).
分类： 物理学 >> 核物理学 提交时间： 2016-09-14
摘要： We investigate the neutral hidden charm pentaquark states P0c(4380) and P0c(4450) in π−p→J/ψnreaction within an effective Lagrangian approach. The background contributions for the process mainly come from t-channel π and ρ meson exchanges. The contributions of P0c(4380) and P0c(4450) states give clear peak structures in the magnitude of 1 μb at center of mass energy 4.38 GeV and 4.45 GeV in the total cross sections. Hence, this reaction may provide a new good platform to search for neutral Pc states. It is expected that our estimated total cross sections together with the angular distributions can be tested by future experiments at J-PARC.
分类： 物理学 >> 核物理学 提交时间： 2016-09-01
Xiaozhuang Wang
Yongjie Sun
Cheng Li
Yuekun Heng
Zhi Wu
Ping Cao
Hongliang Dai
Xiaolu Ji
Wenxuan Gong
Zhen Liu
Xiaolan Luo
Weijia Sun
Siyu Wang
Yun Wang
Rongxing Yang
Mei Ye
Jinzhou Zhao
摘要： The Beijing Spectrometer III (BESIII) endcap Time-Of-Filght (ETOF) was proposed to upgrade with Multigap Resistive Plate Chamber (MRPC) technology to substitute the current ETOF of scintillator+PMT for extending time resolutin better than 80 ps and enhance the particle identification capability to satisfy the higher precision requirement of physics. The ETOF system including MRPC modules, front end electronics (FEE), CLOCK module, fast control boards and time to digital modules (TDIG), has been designed, constructed and done some experimental tests seperately. Aiming at examining the quality of entire ETOF system and training the operation of all participated parts, a cosmic ray test system was built at the laboratory and underwent about three months to guarantee performance. In this paper the results will be presented indicating that the entire ETOF system works well and satisfies the requirements of the upgrade.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Yun Wang
Zhongxu Zhai
Anahita Alavi
Elena Massara
Alice Pisani
Andrew Benson
Christopher M. Hirata
Lado Samushia
David H. Weinberg
James Colbert
Olivier Doré
Tim Eifler
Chen Heinrich
Shirley Ho
Elisabeth Krause
Nikhil Padmanabhan
David Spergel
Harry I. Teplitz
摘要： The Nancy Grace Roman Space Telescope will conduct a High Latitude Spectroscopic Survey (HLSS) over a large volume at high redshift, using the near-IR grism (1.0-1.93 $\mu$m, $R=435-865$) and the 0.28 deg$^2$ wide field camera. We present a reference HLSS which maps 2000 deg$^2$ and achieves an emission line flux limit of 10$^{-16}$ erg/s/cm$^2$ at 6.5$\sigma$, requiring $\sim$0.6 yrs of observing time. We summarize the flowdown of the Roman science objectives to the science and technical requirements of the HLSS. We construct a mock redshift survey over the full HLSS volume by applying a semi-analytic galaxy formation model to a cosmological N-body simulation, and use this mock survey to create pixel-level simulations of 4 deg$^2$ of HLSS grism spectroscopy. We find that the reference HLSS would measure $\sim$ 10 million H$\alpha$ galaxy redshifts that densely map large scale structure at $z=1-2$ and 2 million [OIII] galaxy redshifts that sparsely map structures at $z=2-3$. We forecast the performance of this survey for measurements of the cosmic expansion history with baryon acoustic oscillations and the growth of large scale structure with redshift space distortions. We also study possible deviations from the reference design, and find that a deep HLSS at $f_{\rm line}>7\times10^{-17}$erg/s/cm$^2$ over 4000 deg$^2$ (requiring $\sim$1.5 yrs of observing time) provides the most compelling stand-alone constraints on dark energy from Roman alone. This provides a useful reference for future optimizations. The reference survey, simulated data sets, and forecasts presented here will inform community decisions on the final scope and design of the Roman HLSS.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Yun Wang
Lee Armus
Andrew Benson
Emanuele Daddi
Andreas Faisst
Anthony Gonzalez
Casey Papovich
Zoran Ninkov
Massimo Robberto
Randall J. Rose
Thomas
Rose
Claudia Scarlata
S. A. Stanford
Todd Veach
Zhongxu Zhai
Bradford Benson
L. E. Bleem
Michael W. Davis
George Helou
摘要： ISCEA (Infrared Satellite for Cosmic Evolution Astrophysics) is a small astrophysics mission whose Science Goal is to discover how galaxies evolved in the cosmic web of dark matter at cosmic noon. Its Science Objective is to determine the history of star formation and its quenching in galaxies as a function of local density and stellar mass when the Universe was 3-5 Gyrs old (1.2 10 Mpc in each of 50 protocluster (cluster and cosmic web) fields at 1.2 < z < 2.1. ISCEA measures the star formation quenching factor in those fields, and galaxy kinematics with a precision < 50 km/s to deduce the 3D spatial distribution in each field. ISCEA will transform our understanding of galaxy evolution at cosmic noon. ISCEA is a small satellite observatory with a 30cm equivalent diameter aperture telescope with a FoV of 0.32 deg^2, and a multi-object spectrograph with a digital micro-mirror device (DMD) as its programmable slit mask. ISCEA will obtain spectra of 1000 galaxies simultaneously at an effective resolving power of R=1000, with 2.8"x2.8" slits, over the NIR wavelength range of 1.1 to 2.0 microns, a regime not accessible from the ground without large gaps in coverage. ISCEA will achieve a pointing accuracy of <= 2" FWHM over 200s. ISCEA will be launched into a Low Earth Orbit, with a prime mission of 2.5 years. ISCEA's space-qualification of DMDs opens a new window for spectroscopy from space, enabling revolutionary advances in astrophysics.
分类： 物理学 >> 核物理学 提交时间： 2016-09-05
Zhi Wu
Shengsen Sun
Yuekun Heng
Xiaozhuang Wang
Yongjie Sun
Cheng Li
Hongliang Dai
Ping Cao
Jie Zhang
Weijia Sun
Siyu Wang
Yun Wang
Xiaolu Ji
Jinzhou Zhao
Wenxuan Gong
Mei Ye
Xiaoyan Ma
Mingming Chen
Meihang Xu
Xiaolan Luo
摘要： The upgrade of the current BESIII Endcap TOF (ETOF) is carried out with the Multi-gap Resistive Plate Chamber (MRPC) technology. The installation of the new ETOF has been finished in October 2015. The first results of the MRPCs commissioning at BESIII are reported in this paper.
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