Kinematic surveys of the dwarf spheroidal (dSph) satellites of the Milky Way are revealing tantalising hints about the structure of dark matter (DM) haloes at the low-mass end of the galaxy luminosity function. At the bright end, modelling of spiral galaxies has shown that their rotation curves are consistent with the hypothesis of a Universal Rotation Curve whose shape is supported by a cored dark matter halo. In this paper, we investigate whether the internal kinematics of the Milky Way dSphs are consistent with the particular cored DM distributions which reproduce the properties of spiral galaxies. Although the DM densities in dSphs are typically almost two orders of magnitude higher than those found in (larger) disk systems, we find consistency between dSph kinematics and Burkert DM haloes whose core radii r0 and central densities ρ0 lie on the extrapolation of the scaling law seen in spiral galaxies: log ρ0 \simeq α log r0 + const with 0.9 < α < 1.1. We similarly find that the dSph data are consistent with the relation between ρ0 and baryon scale length seen in spiral galaxies. While the origin of these scaling relations is unclear, the finding that a single DM halo profile is consistent with kinematic data in galaxies of widely varying size, luminosity and Hubble Type is important for our understanding of observed galaxies and must be accounted for in models of galaxy formation.
Dark matter (DM) halos of Sc-Im and dwarf spheroidal (dSph) galaxies satisfy scaling laws: halos in lower-luminosity galaxies have smaller core radii, higher central densities, and smaller velocity dispersions. These results are based on maximum-disk rotation curve decompositions for giant galaxies and Jeans equation analysis for dwarfs. (1) We show that spiral, Im, and Sph galaxies with absolute magnitudes M_V > -18 form a sequence of decreasing baryon-to-DM surface density with decreasing luminosity. We suggest that this is a sequence of decreasing baryon retention vs. supernova-driven losse…
We look for empirical evidence of a non-minimal coupling (NMC) between dark matter (DM) and gravity in the dynamics of local spiral galaxies. In particular, we consider a theoretically motivated NMC that may arise dynamically from the collective behavior of the coarse-grained DM field (e.g., via Bose-Einstein condensation) with averaging/coherence length $L$. In the Newtonian limit, this NMC amounts to modify the Poisson equation by a term $L^{2} \nabla^{2} ρ$ proportional to the Laplacian of the DM density itself. We show that such a term, when acting as a perturbation over the standard Navar…
We present a comparison of azimuthally averaged radial surface brightness mu(r) profiles and analytical bulge-disc decompositions (de Vaucouleurs, r^(1/4) bulge plus exponential disc) for spiral galaxies using Hubble Space Telescope/Advanced Camera for Surveys V-band imaging from the Space Telescope A901/2 Galaxy Evolution Survey (STAGES). In the established classification scheme, antitruncated mu(r) profiles (Type III) have a broken exponential disc with a shallower region beyond the break radius r_brk. The excess light at large radii (r > r_brk) can either be caused by an outer exponential d…
A low-luminosity type-1 QSO sample - A morphological study of nearby AGN hosts
越来越多的证据表明，每一个具有相当大的球状组成部分的星系在其中心都有一个超大质量黑洞。SMBH和球形组件之间的强相关性表明通过共同进化的情况下的物理连接。对于质量非常大的星系，合并驱动的方案是首选，导致椭圆星系。在附近的宇宙中，我们发现了许多盘状星系，没有显示出最近相互作用的迹象。这些星系的另一种长期演化场景涉及内部触发器，如棒和旋臂或小合并。我们分析了来自Hamburg/ESO巡天的99个邻近星系（0.02 < z < 0.06）的样本，以深入了解宿主星系的结构和动力学性质，从而追踪膨胀-SMBH关联的起源。在这项工作中，我们首先收集样本成员的图像，以获得样本中的形态分布的印象。在第二步中，我们开始分析敏感，高分辨率的近红外图像的20个星系，执行光圈测光和鼓盘分解与BUDDA代码。我们发现了一个意想不到的高比例的棒星系和许多其他结构的特点。
We study three cosmological hydrodynamical simulations of Milky Way(MW)-sized halos including a comparison with the dark matter(DM)-only counterparts. We find one of our simulated galaxies with interesting MW-like features. Thanks to a consistently tuned star formation rate and supernovae feedback we obtain an extended disk and a flat rotation curve with a satisfying circular velocity and a reasonable DM density in the solar neighbourhood. Mimicking observational methods, we re-derive the stellar mass and obtain stellar-to-halo mass ratios reduced by more than 50\%. We show the interaction bet…
Dwarf galaxies are ideal laboratories to test dark matter models and alternative theories because their dynamical mass (from observed kinematics) largely outweighs their baryonic mass (from gas and stars). In most star-forming dwarfs, cold atomic gas forms regularly rotating disks extending beyond the stellar component, thus probing the gravitational potential out to the outermost regions. Here I review several aspects of gas dynamics in dwarf galaxies, such as rotation curves, mass models, and noncircular motions. Star-forming dwarfs extend the dynamical laws of spiral galaxies to lower masse…
A review of elliptical and disc galaxy structure, and modern scaling laws
一个世纪前，在1911年和1913年，普卢默和雷诺兹提出了他们的模型来描述恒星在“星云”中的径向分布。本文回顾了自那时以来的进展，提供了一个历史的观点和当代审查的恒星结构的隆起，光盘和椭圆星系。星系核的量化，如中央质量赤字和过剩的核光，加上暗物质晕和cD星系信封的结构，进行了讨论。与旋涡星系有关的问题，包括尘埃，膨胀盘比，无球星系，酒吧和识别的pseudobulges也进行了审查。一系列现代尺度关系，涉及大小，光度，表面亮度和恒星浓度，其中许多是弯曲的。这些“红移零”关系不仅量化了今天宇宙中星系的行为和性质，而且是星系演化研究的现代基准，无论是基于观测，N体模拟还是半分析模型。例如，最近发现的一些1.5 < z < 2.5的致密椭圆星系可能是现代盘星系的凸起。
Recent high-quality observations of dwarf and low surface brightness (LSB) galaxies have shown that their dark matter (DM) halos prefer flat central density profiles. On the other hand the standard cold dark matter model simulations predict a more cuspy behavior. Feedback from star formation has been widely used to reconcile simulations with observations, this might be successful in field dwarf galaxies but its success in low mass galaxies remains uncertain. One model that have received much attention is the scalar field dark matter model. Here the dark matter is a self-interacting ultra light…
