分类： 天文学 >> 星系和宇宙学 提交时间： 2025-06-04
摘要： As an alternative gravitational theory to General Relativity (GR), the Conformal Gravity (CG) has recently been successfully verified by observations of Type Ia supernovae (SN Ia) and the rotation curves of spiral galaxies. The observations of galaxies only pertain to the non-relativistic form of gravity. In this context, within the framework of the Newtonian theory of gravity (the non-relativistic form of GR), dark matter is postulated to account for the observations. On the other hand, the non-relativistic form of CG predicts an additional potential: besides the Newtonian potential, there is a so-called linear potential term, characterized by the parameter \gamma^*, as an alternative to dark matter in Newtonian gravity. To test CG in its non-relativistic form, much work has been done by fitting the predictions to the observations of circular velocity (rotation curves) for spiral galaxies. In this paper, we test CG with the observations from elliptical galaxies. Instead of the circular velocities for spiral galaxies, we use the velocity dispersion for elliptical galaxies. By replacing the Newtonian potential with that predicted by non-relativistic form of CG in Hamiltonian, we directly extend the Jeans equation derived in Newtonian theory to that for CG. By comparing the results derived from the ellipticals with that from spirals, we find that the extra potential predicted by CG is not sufficient to account for the observations of ellipticals. Furthermore, we discover a strong correlation between \gamma^* and the stellar mass M^* in dwarf spheroidal galaxies. This finding implies that the variation in \gamma^* violates a fundamental prediction of Conformal Gravity (CG), which posits that \gamma^* should be a universal constant.
分类： 天文学 >> 星系和宇宙学 提交时间： 2025-06-04
摘要： As an alternative gravitational theory to General Relativity (GR), Conformal Gravity (CG) can be verified through astronomical observations. Currently, {Mannheim and Kazanas have provided vacuum solutions for cosmological and local gravitational systems, and these solutions may resolve the dark matter and dark energy issues encountered in GR, making them particularly valuable}. {For static, spherically symmetric systems,} CG predicts an additional linear potential generated by luminous matter in addition to the conventional Newtonian potential. This extra potential is expected to account for the observations of galaxies and galaxy clusters without the need of dark matter. It is characterized by the parameter \gamma^*, which {corresponds to the linear potential generated by the unit of the solar mass, and it is thus a universal constant}. The value of \gamma^* was determined by fitting the rotation curve data of spiral galaxies. These predictions of CG should also be verified by the observations of strong gravitational lensing. To date, in the existing literature, the observations of strong lensing employed to test CG have been limited to a few galaxy clusters. It has been found that the value of \gamma^* estimated from strong lensing is several orders of magnitude greater than that obtained from fitting rotation curves. In this study, building upon the previous research, we tested CG via strong lensing {statistics}. We used a well-defined sample that consisted of both galaxies and galaxy clusters. This allowed us to test CG through statistical strong lensing in a way similar to the conventional approach in GR. As anticipated, our results were consistent with previous studies, {namely that the fitted \gamma^* is much larger than that from rotation curves}. Intriguingly, we further discovered that, in order to fit the strong lensing data {of another sample}, the value of \gamma^* cannot be a constant, as is required in CG. Instead, we derived a formula for \gamma^* as a function of the stellar mass M_* of the galaxies or galaxy clusters. It was found that \gamma^* decreases as M_* increases.
分类： 天文学 >> 星系和宇宙学 分类： 天文学 >> 星系和宇宙学 提交时间： 2025-05-27
摘要： It is suggested that the formation of dark matter binaries would produce radiation in the same way that the formation of hydrogen atoms does in HII regions. A hydrogen HII region like the Orion Nebula with its Lyman alpha radiation is considered as a model for dark matter particles combining into binaries. This conjecture is considered in detail and it is found to provide a surprising fit to the Planck data isotropy and dipole. It could be regarded as an alternative explanation. A precise mass for the dark matter particle would be 10.7 ZeV (1.07 x 1013 GeV). Examination of the Plank structure of the CMB also suggests there is further physics to be revealed. Observational tests are suggested to check the role of dark matter in the Galaxy Halo.
分类： 天文学 >> 星系和宇宙学 提交时间： 2025-05-18
摘要： There is a clear indication that dark matter in the Milky Way absorbs a tiny amount of light in the visible parts of the spectrum, (Baruch 2025a, and 2025b) . In Baruch (2025c) it is conjectured that this is caused by dark matter forming binary pairs which are destroyed (ionised) by the momentum of photons in the visible parts of the spectrum. This paper examines whether the dark matter binaries will also radiate photons. Can a binary form of dark matter with two spin half fermions produce spin flip radiation in the same way that hydrogen does with the 21cm line? It is shown that any such spin flip radiation would be very faint due to the excessively long half life of the suggested binary form of dark matter.
分类： 天文学 >> 星系和宇宙学 提交时间： 2025-02-21
摘要： The paper Baruch (2025a) shows that there is an apparent wavelength-independent extinction coefficient of 0.06 magnitudes per kiloparsec across the Milky Way. Baruch 2025b) shows that the Hubble constant values of Riess et al (2016, 2018a and 2018b), Freedman et al (2019) and the Planck satellite (Ade et al 2014) coincide if the extinction coefficient is a function of the density of dark matter. This wavelength-independent extinction has a frequency threshold between 160Ghz and 300 Thz. This paper seeks a possible process by which dark matter can absorb light.The current data on dark matter is reviewed to determine how dark matter could act as a wavelength-independent absorber of light in the visible frequencies. The discussion of the role of inertia and momentum in general relativity and its relationship with the other forces since the Einstein paper on General Relativity of 1915 is reviewed. It is conjectured that for a pair of gravitationally bound dark matter particles a photon with sufficient momentum would effectively “ionise” the pair, releasing the two dark matter particles, and absorbing the photon. The approximate mass of the dark matter particle is derived. It is suggested that this dark matter extinction provides real data to help settle the role of inertia and momentum in General Relativity. A test for the “ionisation” process is suggested.
分类： 天文学 >> 星系和宇宙学 提交时间： 2025-02-06
摘要： The Hubble constant H0 defines the rate of expansion of the Universe. Currently there are three conflicting values of the Hubble constant. The Planck team (Ade et al 2014), the Carnegie-Chicago team (Freedman et al 2019), and the SHoES team (Riess et al 2016) have all produced values that disagree beyond their errors. The SHoES team has shown that the Hubble constant is increasing in recent times (Riess et al 1998) reflecting an increase or acceleration in the rate of expansion of the Universe. Baruch (2024a) “Are Stellar Distance Measurements Opening a Window into New Physics?” has reviewed recent data of the SHoES team (Riess et al 2021) where Hubble telescope photometric data for two groups of Cepheids at different distances was linked to Gaia parallax measurements of the same stars. It is shown “beyond reasonable doubt” how for this unique set of precise data the zero-point correction can be eliminated and a wavelength independent (colourless) extinction of light across the Milky Way galaxy revealed. This current paper seeks out the cause of this extinction and shows that the data of Freedman et al 2019 neatly fits a wavelength independent extinction when the cause of the extinction is attributed to dark matter. The extinction coefficients are derived. All the Riess and the Freedman values of the Hubble constant are shown to agree with the Planck Satellite (Ade et al 2014) value within the error bars when the differences are attributed to dark matter extinction. The recent time acceleration in the expansion of the Universe also is shown to be a function of intergalactic dark matter extinction. The key properties required of the dark matter are defined.
分类： 天文学 >> 星系和宇宙学 提交时间： 2025-01-24
摘要： This paper derives a mathematical analysis of the apparent conflict between photometrically based and parallax distance measurements. The best photometrically based distance measurements using the Hubble telescope when compared with the algorithm corrected Gaia parallax measurements do not agree. The algorithm corrected Gaia parallax measurements are quoted by the Gaia team as correct to within a few mico arcseconds, but Riess et al (2021) subtract a further ten micro arc-seconds from each Cepheid parallax. These further corrections to the Gaia data eliminate the conflict and support the Hubble tension derived by Riess et al (2021). There is no conflict in the Hubble photometric and Gaia parallax distances in the Riess et al (2022) paper. Riess et al (2022) use earlier Gaia derived cluster distances and adopt a zero point correction derived from the photometry. The mathematical analysis shows that an alternative method of eliminating the conflict indicates a tiny attenuation of light in the Milky Way. It is argued that this attenuation of the light is completely wavelength-independent. All photometry is equally effected by this wavelength independent attenuation, which requires new physics. Photometry cannot be used to reveal any new physics due to the absorption being wavelength independent. It is shown that when the wavelength independent absorption is included in calculating the absolute magnitude of Cepheids it removes the Hubble tension.
分类： 天文学 >> 星系和宇宙学 提交时间： 2024-10-31
摘要： 无
分类： 天文学 >> 星系和宇宙学 提交时间： 2024-09-16
摘要： We analyse H(z) parameter data with some conditions by using Lagrange mean value theorem in Calculus. We find that: (1) there exists at least one decelerated phase at 1 sigma confidence level in the redshift range (0.38, 0.59); (2) the equation of motion of dark energy may be less than -1 at 1 σ confidence level at some redshifts in the redshift range (1.3, 1.53); (3) there exists at least one accelerated phase at 1 σ confidence level in the redshift range (1.037, 1.944). These results may provide possible evidences for physics beyond $ Lambd ACDM.
分类： 地球科学 >> 空间物理学 分类： 物理学 >> 地球物理学、天文学和天体物理学 分类： 天文学 >> 星系和宇宙学 提交时间： 2024-06-02
摘要： 近邻宜居行星巡天计划(Closeby Habitable Exoplanet Survey, CHES)采用空间微角秒级别的高精度天体测量技术, 普查太阳系近邻(10 pc内)约100颗FGK等类型恒星, 探测宜居带类地行星或超级地球; 详细普查宜居行星的数目、真实质量和三维轨道等信息, 这将是国际上首次近邻宜居带类地行星的空间探测任务. CHES的有效载荷是一台口径为1.2 m, 视场为0.44°×0.44°, 焦距为36 m的高像质、低畸变、高稳定光学望远镜, 采用同轴三反TMA光学成像系统. 为实现宜居带类地行星探测, CHES任务中的测量精度为1 μas, 是目前国际测量精度最高的空间探测项目. 在空间科学先导专项背景型号项目的支持下, CHES团队深入凝练和论证科学目标, 成功突破了三项关键技术难题: 实现了畸变大视场高像质空间望远镜光学系统技术的重要突破; 突破了10–5pixel级别星间距测量技术; 实现了卫星系统高稳定度姿态控制精度及热控精度的创新. CHES预计发现50颗类地行星, 引领中国空间科学探测技术的跨越式发展.
分类： 天文学 >> 星系和宇宙学 提交时间： 2023-12-08
摘要： This paper presents a morphological investigation of the early-type spiral galaxy M81 (NGC 3031) through decomposition by fitting radial profiles of surface brightness using the software GALFIT, aimed at exploring structural components of M81 and quantifying their morphology. In this work, we adopt 6 types of decompositions with different numbers of morphological components, among which the most complicated one contains 5 components such as a bulge, a disk, a pair of outer spiral arms, a pair of inner spiral arms, and a galactic nucleus. The results show that, M81 hosts a classical bulge with the Sersic index 5.0; the morphology and the luminosity for the bulge are almost constant in the different decomposition types. The disk of M81 has the Sersic index 1.2 but the morphology and the luminosity are found sensitive to the inclusion of the inner spiral arms in the decomposition or not. The results of this work indicate that the combination of individual substructures has a considerable impact on the morphology of the galaxy as a mixture. On the basis of the results, the usability of the different types of decomposition is suggested in this work. The three-component decomposition, i.e., bulge + disk + nucleus, is applicable to statistics of large samples of galaxies; more complicated decomposition with spiral arms taken into account is suitable for precise measurements of individual galaxies in small samples. This work is based on the single-band Spitzer-The Infrared Array Camera (IRAC) 4.5 m image. In the future, we will carry out multi-wavelength decomposition, for the purpose of investigating spectral energy distributions and stellar population properties for the galactic substructures, and thereby deduce their formation history and evolution processes.
分类： 天文学 >> 星系和宇宙学 提交时间： 2023-02-21
Qiuhan He
Ran Li
Carlos S. Frenk
James Nightingale
Shaun Cole
Nicola C. Amorisco
Richard Massey
Andrew Robertson
Amy Etherington
Aristeidis Amvrosiadis
Xiaoyue Cao
摘要： We rederive the number density of intervening line-of-sight haloes relative to lens subhaloes in galaxy-galaxy strong lensing observations, where these perturbers can generate detectable image fluctuations. Previous studies have calculated the detection limit of a line-of-sight small-mass dark halo by comparing the lensing deflection angles it would cause, to those caused by a subhalo within the lens. However, this overly simplifies the difference in observational consequences between a subhalo and a line-of-sight halo. Furthermore, it does not take into account degeneracies between an extra subhalo and the uncertain properties of the main lens. More in keeping with analyses of real-world observations, we regard a line-of-sight halo as detectable only if adding it to a smooth model generates a statistically significant improvement in the reconstructed image. We find that the number density of detectable line-of-sight perturbers has been overestimated by as much as a factor of two in the previous literature. For typical lensing geometries and configurations, very deep imaging is sensitive to twice as many line-of-sight perturbers as subhaloes, but moderate depth imaging is sensitive to only slightly more line-of-sight perturbers than subhaloes.
分类： 天文学 >> 星系和宇宙学 提交时间： 2023-02-21
摘要： In this paper we consider the effects of adding curvature in extended cosmologies involving a free-to-vary neutrino sector and different parametrizations of Dark Energy (DE). We make use of the Planck 2018 cosmic microwave background temperature and polarization data, Baryon Acoustic Oscillations and Pantheon type Ia Supernovae data. Our main result is that a non-flat Universe cannot be discarded in light of the current astronomical data, because we find an indication for a closed Universe in most of the DE cosmologies explored in this work. On the other hand, forcing the Universe to be flat can significantly bias the constraints on the equation of state of the DE component and its dynamical nature.
分类： 天文学 >> 星系和宇宙学 提交时间： 2023-02-21
摘要： Interstellar (ISM) and circumgalactic medium (CGM) around galaxies are linked to several physical processes that drive galaxy evolution. For example, the X-ray emission from the CGM gas around ellipticals has been linked to the AGN feedback occurring in the host. Upcoming telescopes such as HUBS, with ~ 1 eV resolution, can provide us with deep insights about the hot gas properties of such galaxies thus constrain these processes. In this project, we discuss X-ray emission of the ISM and CGM of elliptical galaxies simulated using MACER code. We generate X-ray emission data from the MACER simulations with various feedback models and produce mock observations for an instrument with high spectral resolution, which is a necessary step of selecting sources for the future observations with planned mission such as HUBS. More importantly, we establish connections between the physics of AGN and stellar feedback with the emission spectra from the ISM and CGM to investigate the possibility of using observations to constrain feedback models. We fit the X-ray spectra from these simulations with standard fitting procedures and compare the retrieved physical properties with their counterparts from the simulations to understand whether the future high-resolution observations can reliably reveal the properties of the gas in the galaxies.
分类： 天文学 >> 星系和宇宙学 提交时间： 2023-02-21
Y. T. Yan
C. Henkel
K. M. Menten
Y. Gong
H. Nguyen
J. Ott
A. Ginsburg
T. L. Wilson
A. Brunthaler
A. Belloche
J. S. Zhang
N. Budaiev
D.Jeff
摘要： We report the discovery of widespread maser emission in non-metastable inversion transitions of NH_3 toward various parts of the Sagittarius B2 molecular cloud/star forming region complex: We detect masers in the J,K= (6,3), (7,4), (8,5), (9,6), and (10,7) transitions toward Sgr B2(M) and Sgr B2(N), an NH_3 (6,3) maser in Sgr B2(NS), and NH_3 (7,4), (9,6), and (10,7) masers in Sgr B2(S). With the high angular resolution data of the Karl G. Jansky Very Large Array (JVLA) in A-configuration we identify 18 maser spots. Nine maser spots arise from Sgr B2(N), one from Sgr B2(NS), five from Sgr B2(M), and three in Sgr B2(S). Compared to our Effelsberg single dish data, the JVLA data indicate no missing flux. The detected maser spots are not resolved by our JVLA observations. Lower limits to the brightness temperature are >3000~K and reach up to several 10^5~K, manifesting the lines' maser nature. In view of the masers' velocity differences with respect to adjacent hot molecular cores and/or UCH{\scriptsize II} regions, it is argued that all the measured ammonia maser lines may be associated with shocks caused either by outflows or by the expansion of UCH{\scriptsize II} regions. Overall, Sgr B2 is unique in that it allows us to measure many NH_3 masers simultaneously, which may be essential to elucidate their so far poorly understood origin and excitation.
分类： 天文学 >> 星系和宇宙学 提交时间： 2023-02-21
Guang Yang
W. N. Brandt
David M. Alexander
Médéric Boquien
Qingling Ni
Casey Papovich
Justin S. Spilker
Fabio Vito
Jonelle L. Walsh
Chengpeng Zhang
摘要： Recent studies have revealed a strong relation between sample-averaged black-hole (BH) accretion rate (BHAR) and star formation rate (SFR) among bulge-dominated galaxies, i.e., lockstep BH-bulge growth, in the distant universe. This relation might be closely related to the BH-bulge mass correlation observed in the local universe. To understand further BH-bulge coevolution, we present ALMA CO(2-1) or CO(3-2) observations of 7 star-forming bulge-dominated galaxies at z=0.5-2.5. Using the ALMA data, we detect significant (>3) CO emission from 4 objects. For our sample of 7 galaxies, we measure (or constrain with upper limits) their CO line fluxes and estimate molecular gas masses (M_{gas}). We also estimate their stellar masses (M_{star}) and SFRs by modelling their spectral energy distributions (SEDs). Using these physical properties, we derive the gas-depletion timescales (t_{dep} = M_{gas}/SFR) and compare them with the bulge/BH growth timescales (t_{grow} = M_{star}/SFR \sim M_{BH}/BHAR). Our sample generally has t_{dep} shorter than t_{grow} by a median factor of ≳4, indicating that the cold gas will be depleted before significant bulge/BH growth takes place. This result suggests that the BH-bulge lockstep growth is mainly responsible for maintaining their mass relation, not creating it. We note that our sample is small and limited to z<2.5; JWST and ALMA will be able to probe to higher redshifts in the near future.
分类： 物理学 >> 地球物理学、天文学和天体物理学 分类： 物理学 >> 电磁学、光学、声学、传热、经典力学和流体动力学 分类： 天文学 >> 星系和宇宙学 提交时间： 2022-11-03
摘要： 本文以物理学中标准钟和标准尺的定义实质和爱因斯坦的相对论物理为基础，从自然哲学层次出发讨论了物理的时空观。提出在已有的时空标度的概念基础上，应该进一步明确区分时空标度和时空背景。根据爱因斯坦相对论的实际逻辑可以作如下理解，满足相对论性变化的是时空标度，而时空标度是人为地根据物质实体中发生或存在的固有物理事件定义的，时空背景作为反映时空标度的长短或大小变化的必备基础和参考背景，应该是绝对的。空间标度的长短尺度在本质上应该理解为固有物理事件在空间的绝对背景上截取的线段的长度。最后以此时空观为基础，探讨了经典力学框架下的质点动力学方程，自然地得出了新形式的质点动力学方程。新动力学方程可以直接应用到任何实际的，（相对宇宙绝对背景）无转动的参考系中。而惯性力的本质正是作用到参考物体上的真实受力。这一经典质点动力学改造的本质是修正了牛顿第二定律传统体系中存在的一个理论缺陷。然而，可能更为重要的是，在形式上具备明显优越性的新质点动力学方程反过来强烈地暗示了时空背景的绝对性。文章最后结合广义相对论的引力几何化思想，探讨了引力对时空标度的物理效应。
分类： 物理学 >> 地球物理学、天文学和天体物理学 分类： 天文学 >> 星系和宇宙学 提交时间： 2020-09-09
摘要： Motivated by recent work on rotating black hole shadow [Phys. Rev. D101, 084029 (2020)], we investigate the shadow behaviors of rotating Hayward-de Sitter black hole for static observers at a finite distance in terms of astronomical observables. This paper uses the newly introduced distortion parameter in [arXiv:2006.00685] to describe the shadow's shape quantitatively. We show that the spin parameter would distort shadows and the magnetic monopole charge would increase the degree of deformation. At the same time, the distortion could be relieved because of the cosmological constant and the distortion would increase with the distance from the black hole. Besides, the spin parameter, magnetic monopole charge and cosmological constant increase will cause the shadow to shrink.
分类： 天文学 >> 星系和宇宙学 提交时间： 2018-04-25
摘要： 本文是[1]对冲突簇的延续和推广。我们研究冲突子群中的总、暗物质密度分布和关联。就像我们对纽曼星系团所做的那样。就像Newman星系团一样，我们发现密度分布受重子相互作用和能量的影响很大。角动量通过动态摩擦从重子转移到DM。大星系团的暗物质密度剖面的内斜率通常比纳瓦罗-弗伦克-白剖面内坡，最大值为-0.79，最小值为-0.30.如在Newman星系团的情况下，斜率α之间存在一系列的相关性。暗物质剖面，以及：A.团簇的核心半径；B.有效半径Re；C.最明亮的中央星系(BCG)的质量；D.总重子质量和恒星质量星系团。我们还发现了有效半径与病毒质量之间的关系。簇的结构，它们的总密度和密度分布，以及它们之间的相关性是：在两个阶段的情况下理解。在第一个耗散阶段，BGC形成。在第二耗散相，重子团与DM的相互作用动力摩擦(DF)使DM分布趋于平缓。这两个阶段的最终结果是不同DM分布、内部斜率及几种关联的簇的形成簇的特征量
分类： 天文学 >> 星系和宇宙学 提交时间： 2018-03-27
摘要： 在本文中，我们将展示重子物理是如何解决矮星中惊人的多样性问题的。 星系旋转曲线形状。为此，我们比较了SPARC样本的星系分布。 平面V2kpc-V最后(V2kpc是星系在2 kpc时的旋转速度，V是最外层的)。 我们模拟的星系考虑了重子效应。V2kpc-V上旋转曲线中的散射 平面上，SPARC样品的分布趋势与我们模拟星系的分布基本一致。大 解决“多样性”问题的关键在于重子过程产生非自相似光晕的能力。 只有DM的模拟。我们还发现，重子效应可以再现IC 2574等星系的自转曲线。 以半径上升缓慢为特征的。通过适当的处理，可以得到多样性问题的一个解。 考虑到重子物理效应。
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