The recent years have seen combined measurements of X-ray and (weak) lensing contours for colliding galaxy clusters such as, for instance, the famous "Bullet" cluster. These observations have revealed offsets in the peaks of the baryonic and (dominant) gravitational matter component of order ~(100-200) kpc. Such discrepancies are difficult to explain using modified theories for gravity other than dark matter. Or are they not? Here we use the concept of "phantom dark matter" that is based upon a Newtonian interpretation of the MONDian gravitational potential. We show that this idea is in fact capable of producing substantial offsets in idealistic density configurations, involving a uniform external field. However, when analysed in a MONDian cosmological framework we deduce that the size (and probablity) of the effect is too small to explain the observed offsets found in the most recent observations, at least in the simplest incarnation of phantom dark matter as discussed here. The lensing centers in merging galaxy clusters are likely very close to the centers of true mass even in a MONDian cosmology. This gives the support to the idea that neutrino-like non-collisional matter might be responsible for the observed offsets of lensing and X-ray peaks.
We address three genuine phantom dark energy models where each of them induces the particular future events known as Big Rip, Little Rip and Little Sibling of the Big Rip. The background models are fully determined by a given dark energy equation of state. We first observationally constrain the corresponding model parameters that characterise each paradigm using the available data of supernova type Ia, Cosmic Microwave Background and Baryonic Acoustic Oscillations by using a Markov Chain Monte Carlo method. The obtained fits are used to solve numerically the first order cosmological perturbati…
An accurate modelling of baryonic feedback effects is required to exploit the full potential of future weak-lensing surveys such as Euclid or LSST. In this second paper in a series of two, we combine Euclid-like mock data of the cosmic shear power spectrum with an eROSITA X-ray mock of the cluster gas fraction to run a combined likelihood analysis including both cosmological and baryonic parameters. Following the first paper of this series, the baryonic effects (based on the baryonic correction model of Schneider et al. 2019) are included in both the tomographic power spectrum and the covarian…
A comprehensive separation of dark matter and baryonic mass components in galaxy clusters I: Mass constraints from Abell S1063
Durham University（杜伦大学）；Ecole Polytechnique Fédérale de Lausanne (EPFL)（洛桑联邦理工学院）；Aix Marseille Univ, CNRS, CNES, LAM, Marseille, France（法国马赛艾克斯大学）；ESO Vitacura, Alonso de Córdova 3107,Vitacura, Casilla 19001, Santiago de Chile, Chile（智利圣地亚哥ESO维塔库拉天文台）；SKA Observatory, Jodrell Bank, SK11 9FT, UK（英国SKA天文台乔德尔班克）；University of KwaZulu-Natal, Westville Campus, Durban 4041, South Africa（南非夸祖鲁-纳塔尔大学）
We explore the impact of baryonic effects (namely stellar and AGN feedback) on the moments of pairwise velocity using the Illustris-TNG, EAGLE, cosmo-OWLS, and BAHAMAS suites of cosmological hydrodynamical simulations. The assumption that the mean pairwise velocity of the gas component follows that of the dark matter is studied here at small separations, and we find that even at pair separations of 10-20 $h^{-1}\mathrm{Mpc}$ there is a 4-5% velocity bias. At smaller separations, it gets larger with strength varying depending on the subgrid prescription. By isolating different physical processe…
Korea Astronomy and Space Science Institute（韩国天体物理与空间科学研究所）；University of Science and Technology（科学技术大学）；Inter-University Centre for Astronomy and Astrophysics（大学间天文与天体物理中心）；Bogolyubov Institute for Theoretical Physics（博戈留波夫理论物理研究所）
Observational cosmology in the next decade will rely on probes of the distribution of matter in the redshift range between $0<z<3$ to elucidate the nature of dark matter and dark energy. In this redshift range, galaxy formation is known to have a significant impact on observables such as two-point correlations of galaxy shapes and positions, altering their amplitude and scale dependence beyond the expected statistical uncertainty of upcoming experiments at separations under 10 Mpc. Successful extraction of information in such a regime thus requires, at the very least, unbiased models for the i…
Context. Accurate model predictions including the physics of baryons are required to make the most of the upcoming large cosmological surveys devoted to gravitational lensing. The advent of hydrodynamical cosmological simulations enables such predictions on sufficiently sizeable volumes. Aims. Lensing quantities (deflection, shear, convergence) and their statistics (convergence power spectrum, shear correlation functions, galaxy-galaxy lensing) are computed in the past lightcone built in the Horizon-AGN hydrodynamical cosmological simulation, which implements our best knowledge on baryonic phy…
暗物质的独特性质在星系团之间的碰撞中被揭示出来，比如子弹星系团（1 E 0657-56）和婴儿子弹星系团（MACSJ 0025 -12）。这些系统提供了一个额外的证据，不可见的质量在其总质量分布之间的分离，通过引力透镜测量，和他们的普通“重子”物质，通过其X射线发射测量。不幸的是，从这些系统中获得的信息因其稀少而受到限制。因此，对暗物质性质的限制，如其相互作用截面，受到各个系统的撞击速度、碰撞参量和视线方向的不确定性的限制。在这里，我们开发了一个互补的统计测量，其中落入每个大规模集群的每一块子结构都被视为子弹。我们将“子弹性”定义为暗物质和普通物质之间的平均间隔，并在流体动力学模拟中测量信号。子结构轨道的相空间也表现出对称性，提供了一个等效的控制测试。任何在真实数据中检测到的子弹性都将表明重子和暗物质相互作用截面的差异，这可能会排除非颗粒暗物质的假设，否则这些假设能够模拟单个系统。随后对子弹性的测量可以限制暗物质的横截面。即使保守估计，现有的HST档案应该产生一个独立的约束比子弹集群更严格。然后，这种技术可以很容易地扩展到未来更大的调查中，并从中受益匪浅。
$f(T)$理论是远平行或扭转标量$T$引力理论的推广，最近被提出来解释目前宇宙的加速膨胀，而不需要暗能量。在这封信中，我们首先对两个具体的$f(T)$模型进行了状态查找器分析和$Om(z)$诊断，即，$f(T)=α(-T)^n$和$f(T)=-αT(1-e^{p {T_0}/T})$模型的仿真结果表明，两种模型都不可能出现虚拟分界线的交叉。这与现有的结果相反，在现有的结果中，第二种模型被要求交叉。然后，我们研究了最新的联盟2 Ia型超新星（Sne Ia）集，重子声振荡（BAO）和宇宙微波背景辐射（CMB）对它们的约束。我们的结果表明，在95%置信水平下，模型1的$Ω_{m0}=0.272_{-0.032}^{+0.036}$、$n=0.04_{-0.33}^{+0.22}$和模型2的$Ω_{m0}=0.272_{-0.034}^{+0.036}$、$p=-0.02_{-0.20}^{+0.31}$。通过$χ^2_{Min}/dof$（dof：degree of freedom）准则将这两个模型与$Λ$ CDM进行比较，表明$Λ$ CDM仍然受到观测的青睐。我们还研究了该理论中有效暗能量状态方程的演化，发现Sne Ia倾向于幻影状暗能量，而Sne Ia + BAO + CMB倾向于精粹状暗能量.
Detection of warm and diffuse baryons in large scale structure from the cross-correlation of gravitational lensing and the thermal Sunyaev-Zeldovich effect
Indications of a Late-Time Transition to a Strongly Interacting Dark Sector
Durban University of Technology（德班理工大学）；North-West University（西北大学）；Universidad Catòlica del Norte（北方天主教大学）；National Institute for Theoretical and Computational Sciences (NITheCS)（国家理论与计算科学研究所）
In a recent work [Phys. Rev. D 98, 043521 (2018)], we have investigated a dark matter (DM)-photon coupling model in which the DM decays into photons in the presence of dark energy (DE) with the constant equation of state (EoS) parameter. Here, we study an extension of the DM-photon coupling model by considering a time-varying EoS of DE via Chevalier-Polarski-Linder (CPL) parametrization. We derive observational constraints on the model parameters by using the data from cosmic microwave background (CMB), baryonic acoustic oscillations (BAO), the local value of Hubble constant from Hubble Space …
Neutrino mass limits and decaying dark matter: background evolution versus perturbations
Laboratoire Univers et Particules de Montpellier (LUPM)（蒙彼利埃宇宙与粒子实验室）；Institut für Astroteilchenphysik, Karlsruher Institut für Technologie (KIT)（卡尔斯鲁厄理工学院天体粒子物理研究所）
