1 Introduction

The idea of the presence of large amounts of invisible matter in and around spirals, distributed differently from the stellar and gaseous disks, turned up in the 1970s (Roberts 1978; Faber and Gallagher 1979; Rubin et al. 1980; Bosma 1981a, see also Bertone and Hooper 2018). There were, in fact, published optical and 21-cm rotation curves (RCs) behaving in a strongly anomalous way. These curves were incompatible with the Keplerian fall-off we would predict from their outer distribution of luminous matter (see Fig. 1).
20 世纪 70 年代出现了大量不可见物质存在于螺旋星系内外的想法(Roberts 1978; Faber and Gallagher 1979; Rubin et al. 1980; Bosma 1981a,另请参阅 Bertone 和 Hooper 2018)。事实上,已经发表了光学和 21 厘米旋转曲线(RCs),其行为方式非常异常。这些曲线与我们从它们的外部发光物质分布预测的开普勒式衰减不兼容(见图 1)。

From there, this dark component has started to take a role always more important in cosmology, astrophysics and elementary particles physics. On the other hand, the nature and the cosmological history of such dark component has always become more mysterious and difficult to be derived from paradigms and first principles. We must remark that a dark massive component in the mass budget of the Universe is necessary to explain: the redshift dependence of the expansion of its scale factor, the relative heights of the peaks in the CMB cosmic fluctuations, the bottom-up growth of the cosmological structures to their nonlinear phases, the large-scale distribution of galaxies and the internal mass distribution of the biggest structures of the Universe. These theoretical issues and observational evidences (that will not be treated in this review) add phenomenal support to the paradigm of a massive dark particle, which, a fortiori, must lay beyond the zoo of the Standard Model of the elementary particles. This support is not able, however, to determine the kind, the nature and the mass of such a particle.
从那时起,这种黑暗成分在宇宙学、天体物理学和基本粒子物理学中开始扮演越来越重要的角色。另一方面,这种黑暗成分的性质和宇宙学历史变得越来越神秘和难以从范式和第一原则中推导出来。我们必须指出,宇宙的质量预算中存在一个黑暗的大质量成分是必要的,以解释:其尺度因子扩展的红移依赖性,CMB 宇宙波动中峰值的相对高度,宇宙结构的自底向上增长到非线性阶段,星系的大尺度分布以及宇宙最大结构的内部质量分布。这些理论问题和观测证据(本文不会讨论)为大质量暗粒子的范式提供了巨大支持,这种粒子必然超越基本粒子标准模型的动物园。然而,这种支持无法确定这种粒子的种类、性质和质量。

There is no doubt that dark matter connects, as no other issue, the different fields of study of cosmology, particle physics and astrophysics. In the current Λ cold dark matter (ΛCDM) paradigm, the DM is non-relativistic since its decoupling time and can be described by a collisionless fluid, whose particles interact only gravitationally and very weakly with the Standard Model particles (Jungman et al. 1996; Bertone 2010).
毫无疑问,暗物质连接了宇宙学、粒子物理和天体物理等不同领域的研究,暗物质在当前的冷暗物质(CDM)范式中是非相对论的,因为它的脱耦时间,可以被描述为一种无碰撞流体,其粒子仅通过引力与标准模型粒子发生非常微弱的相互作用(Jungman 等,1996 年;Bertone,2010 年)。

Fig. 1
figure 1

The image of M33 and the corresponding rotation curve (Corbelli and Salucci 2000). What exactly does this large anomaly of the gravitational field indicate? The presence of (i) a (new) non-luminous massive component around the stellar disk or (ii) new physics of a (new) dark constituent?
M33 的图像和相应的旋转曲线(Corbelli 和 Salucci 2000)。引起引力场大异常的究竟是什么?(i)恒星盘周围存在一个(新的)非发光的大质量组分,还是(ii)一个(新的)暗物质的新物理?

In the past 30 years, in the preferred ΛCDM scenario, the complementary approach of detecting messengers of the dark particle and creating it at colliders has brought over an extraordinary theoretical and experimental effort that, however, has not reached a positive result. Moreover, on the scales <50 kpc, where great part of the DM resides, there is a growing evidence of increasingly quizzical properties of the latter are, so that, a complex and surprising scenario, of very difficult understanding, is emerging.
在过去的 30 年中,在首选的 Λ CDM 方案中,探测暗粒子信使并在对撞机中创造暗粒子的互补方法带来了非凡的理论和实验努力,然而,尚未取得积极的结果。此外,在 <50 kpc 的尺度上,大部分暗物质存在的地方,越来越多的证据显示出后者具有越来越令人费解的特性,因此,一个复杂且令人惊讶的场景正在出现,非常难以理解。

1.1 Scope of the review

The distribution of matter in galaxies does not seem to be the final act of a simple and well-understood history which has developed itself over the whole age of the Universe. It seems, instead, to lead to one of the two following possibilities: (1) the dark particle is a WIMP; however, baryons enter, heavily and in a very tuned way, into the process of galaxy formation, modifying, rather than following, the original DM distribution (2) the dark particle is something else, likely interacting with SM particle(s) and very likely lying beyond our current ideas of physics.
星系中物质的分布似乎不是一个简单且被充分理解的历史的最终结果,这个历史在整个宇宙的年龄中发展。相反,它似乎导致以下两种可能性之一:(1)暗物质粒子是 WIMP;然而,重子以一种非常调谐的方式进入星系形成过程,修改而不是遵循原始的暗物质分布(2)暗物质粒子是其他东西,可能与标准模型粒子相互作用,并且很可能超出我们当前的物理学理念。

In both cases, investigating deeply the distribution of dark matter in galaxies is necessary and worthwhile. In the first case, the peculiar imprint that baryons leave on the original distribution of the dark particles can serve us as an indirect, but telling, investigation of the latter. In the second case, with no guidance from first principles, a most complete investigation of the dark matter distribution in galaxies is essential to grasp its nature.

In any case, it is now possible to investigate such issue in galaxies of various morphological types and luminosities. We are sure that this will help us to shed light on the unknown physics underlying the dark matter mystery.

There are no doubts that the topic of this review is related and, in some case, even entangled with other main topics of cosmology and astroparticle physics. However, this work will be kept focused on the properties of dark matter where it mostly resides. Then, a number of issues, yet linked to the dark matter in galaxies, will not be dealt here or will be dealt in a very schematic way. This, both because we sense that looking for the “naked truth” of the galactic dark matter is the best way to approach the related mystery and because there are recent excellent reviews, suitable to complete the whole picture of dark matter in galaxies. These include: “The Standard Cosmological Model: Achievements and Issues” (Ellis 2018), standard and exotic dark-matter candidate particles and their related searches and productions (Roszkowski et al. 2017; Lisanti 2017), the ΛCDM scenario and its observational challenges (Naab and Ostriker 2017; Somerville and Dave 2015; Bullock and Boylan-Kolchin 2017; Turner 2018), “The Connection Between Galaxies and Their Dark Matter Halos” (Hudson et al. 2015; Wechsler and Tinker 2018), “Status of dark matter in the universe” (Freese 2017), “Galaxy Disks” (van der Kruit and Freeman 2011) and “Chemical Evolution of Galaxies” (Matteucci 2012). In addition, in the next sections, when needed, I will indicate the readers the papers that extend and deepen the content here presented.
毫无疑问,本审查的主题与宇宙学和宇宙粒子物理学的其他主题相关,并且在某些情况下甚至纠缠在一起。然而,本文将专注于暗物质的性质,因为它主要存在于其中。因此,一些与星系中的暗物质有关的问题将不在此处讨论,或者将以非常概略的方式处理。这是因为我们感觉到寻找“银河暗物质的真相”是接近相关神秘的最佳方式,而且有最近的优秀审查文章,适合完整呈现星系中的暗物质整体图景。这些包括:“标准宇宙学模型:成就与问题”(Ellis 2018),标准和奇异暗物质候选粒子及其相关的搜索和产生(Roszkowski 等人 2017;Lisanti 2017), Λ CDM 情景及其观测挑战(Naab 和 Ostriker 2017;Somerville 和 Dave 2015;Bullock 和 Boylan-Kolchin 2017;Turner 2018),“星系与其暗物质晕之间的联系”(Hudson 等人 2015;Wechsler 和 Tinker 2018),“宇宙中暗物质的现状”(Freese 2017),“星系盘”(van der Kruit 和 Freeman 2011)和“星系的化学演化”(Matteucci 2012)。此外,在接下来的章节中,如有需要,我将指示读者查阅扩展和深化本文内容的论文。

Let us stress that, although in this review one can find several observational evidences that can be played in disfavour of the ΛCDM scenario, this review is not meant to be a collection of observational challenges to such scenario and several issues at such regard, e.g., Müller et al. (2018), will not be considered here.
让我们强调,尽管在这篇评论中可以找到几个观察证据,可以对 Λ CDM 情景不利,但这篇评论并不意味着是对这种情景的观察挑战的集合,也不会考虑在这方面的几个问题,例如,Müller 等人(2018 年)的研究。

It is worth pointing out that here we do not consider the theories alternative to the DM, that is, theories that dispose of the dark particle. The main reasons are (1) space: an honest account of them will require to add many more pages to this longish review and (2) my personal bias: no success in explaining the observations at galactic scale can compensate the intrinsic inability that these theories have in conceiving the galaxy formation process and interpreting the corpus of the cosmological observations.
值得指出的是,我们在这里不考虑与 DM 相反的理论,即那些不包含暗物质粒子的理论。主要原因是:(1)空间:对它们的诚实描述将需要在这篇冗长的评论中添加更多页面;(2)我的个人偏见:在解释星系尺度观测方面没有成功,无法弥补这些理论在构想星系形成过程和解释宇宙观测数据方面的固有无能。

1.2 The presence of dark matter in galaxies
1.2 星系中暗物质的存在

Let us introduce the “phenomenon” of dark matter in galaxies as it follows:let M(r) be the mass distribution of the gravitating matter and