The Bakerian Lecture, 1982: Galaxies and their nuclei

1985 ◽  
Vol 400 (1819) ◽  
pp. 183-218 ◽  
Keyword(s):  
Black Holes ◽  
Galactic Nuclei ◽  
High Energy ◽  
Big Bang ◽  
Stellar Structure ◽  
Kerr Metric ◽  
Galactic Centre ◽  
The Galaxy ◽  
Nearby Galaxies ◽  
The Big Bang

This lecture briefly reviews current ideas on some key problems in extragalactic physics. Our understanding of galaxies and how they evolve is still tentative and fragmentary – perhaps at the same level as the study of stellar structure several decades ago. The ‘seeds’ from which galaxies formed were small-amplitude fluctuations imprinted during the initial high-energy phases of the Big Bang; but it is conventional physics - gas dynamics, atomic physics and Newtonian gravity - that determines their characteristic sizes and shapes. Quantitative modelling of galactic evolution is impeded by our poor understanding of how stars form from protogalactic gas. Another stumbling block has been the realization that 90% of the gravitating material in galaxies is in some ‘hidden’ form: the conspicuous stars and gas are merely ‘sediment’ in a potential well ten times larger contributed by material of unknown nature. The hidden mass could be small faint stars or the collapsed remnants of massive stars; alternatively, it could be some species of particle surviving from the Big Bang. Some galaxies harbour, in their centres, ‘engines’ more powerful than the entire integrated output of their ca 10 11 constituent stars. Extreme instances of this phenomenon are the quasars – galactic nuclei that flare up to outshine the rest of the galaxy. Galaxies sometimes eject wellcollimated jets of (possibly electron-positron) plasma, flowing at almost the speed of light. These jets, transporting an energy flux that may amount to an entire galactic luminosity, propagate for up to 10 6 light years; their interaction with the external medium is manifested in the intense synchrotron radiation from strong radio sources. Active galactic nuclei probably involve spinning black holes of 10 8 M ⊙ (described in Einstein’s theory by the Kerr metric) created by a runaway gravitational collapse. The luminosity and the plasma outflow could be energized by infall of surrounding material, or by the rotational energy of the holes, which can be extracted via electromagnetic torques. Massive black holes may lurk quiescent in the centres of several nearby galaxies, and even at our own Galactic Centre.

High energy neutrino sources

1994 ◽  
Vol 346 (1678) ◽  
pp. 93-98 ◽  
Keyword(s):  
Active Galactic Nuclei ◽  
Galaxy Evolution ◽  
Cosmic Strings ◽  
Galactic Nuclei ◽  
High Energy ◽  
Big Bang ◽  
The Past ◽  
The Earth ◽  
The Big Bang ◽  
Bright Phase

High energy cosmic neutrinos can be produced by protons and nuclei accelerated in cosmic sources (‘acceleration neutrinos) as well as by relic Big Bang particles, cosmic strings, etc. (neutrinos of non-acceleration origin). The most promising ‘acceleration’ sources of neutrinos are supernovae in our Galaxy and active galactic nuclei (AGN). Detectable diffuse fluxes of ‘ acceleration ’ neutrinos can be produced by AGN and during the ‘bright phase’ of galaxy evolution. During the past few years it has been realized that the detectable flux of high energy neutrinos can be also produced by the relic Big Bang particles. The possible sources are annihilation of the neutralinos accumulated inside the Earth and the Sun, decay of neutralinos (due to the weak breaking of R-parity), and the decay of exotic long-lived particles from the Big Bang.

scholarly journals КВАЗАРИ І РЕГЕНЕРАЦІЯ ВОДНЮ. ЧАСТИНА 2.

2019 ◽  
pp. 190-201
Author(s):  
Анатолий Николаевич Нарожный
Keyword(s):  
Active Galactic Nuclei ◽  
Indirect Evidence ◽  
Galactic Nuclei ◽  
Big Bang ◽  
Residual Hydrogen ◽  
The Galaxy ◽  
Intergalactic Space ◽  
Galactic Astronomy ◽  
The Big Bang ◽  
The Universe

Further consequences of the mechanisms of hydrogen regeneration, which are realized in large galaxies during the period of activity of their nuclei, are considered. In addition to the indirect evidence presented in the first part and related to the work of the structures forming the jets, this part of the article considers direct evidence of the existence of these processes in galaxies. The evidence given is based on emissions of regenerated hydrogen into galactic and intergalactic space, as shown by astronomical observations of the Galaxy and its closest surroundings. Evidence is also found among the general observational data of intergalactic astronomy, the origin of which is well explained in the framework of the approach presented. However, these data are traditionally viewed through the prism of the dominant concept, that is, they are interpreted as residual hydrogen, which appeared from the Big Bang. Among the results of galactic astronomy there are data showing the possible contribution of the processes under consideration to the formation of the observable structure of the Milky Way, as well as their involvement in the organization of its satellite galaxies. The criterion is given, according to which galactic gas clouds and star groups can be distinguished, organized from the galaxy's own matter during the period of activity of its nucleus. Using the example of a spiral galaxy, it is suggested that the active galactic nuclei might be involved in the formation of the morphology of the galaxy. It is concluded that the central supermassive object in the period of its activity, performs its main galactic function - carries out the processing of waste of stars in the galaxy. This inverse process closes the chain of the continuous life cycle of the galaxy, which consists of two interrelated processes. The first process is the continuous burning of hydrogen in the stars, and the second is the episodic activity of the galactic nucleus, as a result of which hydrogen is recovered from the "waste", necessary to support direct stellar processes. One more process joins these two processes - the process of returning the energy expended by baryonic matter to electromagnetic radiation. It is realized through the dark component of matter. The main conclusion is made - the Universe as a system is well organized and self-sufficient for its eternal existence, and it does not need any external motivation.

scholarly journals Spiral morphology in an intensely star-forming disk galaxy more than 12 billion years ago

Science ◽  
2021 ◽  
pp. eabe9680
Author(s):  
Takafumi Tsukui ◽  
Satoru Iguchi
Keyword(s):  
Big Bang ◽  
Compact Structure ◽  
Spiral Arms ◽  
Star Forming ◽  
Gas Kinematics ◽  
Internal Structures ◽  
The Galaxy ◽  
Galaxy Center ◽  
The Big Bang ◽  
Tidal Tails

Spiral galaxies have distinct internal structures including a stellar bulge, disk and spiral arms. It is unknown when in cosmic history these structures formed. We analyze observations of BRI 1335–0417, an intensely star-forming galaxy in the distant Universe, at redshift 4.41. The [C ii] gas kinematics show a steep velocity rise near the galaxy center and have a two-armed spiral morphology, which extends from about 2 to 5 kiloparsecs in radius. We interpret these features as due to a central compact structure, such as a bulge; a rotating gas disk; and either spiral arms or tidal tails. These features had formed within 1.4 billion years after the Big Bang, long before the peak of cosmic star formation.

scholarly journals Planck Neutrinos as Ultra High Energy Cosmic Rays

2020 ◽  
Vol 29 (1) ◽  
pp. 40-46
Author(s):  
Dmitri L. Khokhlov
Keyword(s):  
Black Holes ◽  
Cosmic Rays ◽  
Standard Model ◽  
Active Galactic Nuclei ◽  
Planck Scale ◽  
Galactic Nuclei ◽  
High Energy ◽  
Ultra High Energy ◽  
High Energy Cosmic Rays ◽  
The Standard Model

AbstractThe studied conjecture is that ultra high energy cosmic rays (UHECRs) are hypothetical Planck neutrinos arising in the decay of the protons falling onto the gravastar. The proton is assumed to decay at the Planck scale into positron and four Planck neutrinos. The supermassive black holes inside active galactic nuclei, while interpreted as gravastars, are considered as UHECR sources. The scattering of the Planck neutrinos by the proton at the Planck scale is considered. The Planck neutrinos contribution to the CR events may explain the CR spectrum from 5 × 1018 eV to 1020 eV. The muon number in the Planck neutrinos-initiated shower is estimated to be larger by a factor of 3/2 in comparison with the standard model that is consistent with the observational data.

scholarly journals The ecology of the galactic centre: Nuclear stellar clusters and supermassive black holes

2019 ◽  
Vol 14 (S351) ◽  
pp. 80-83 ◽  
Author(s):  
Melvyn B. Davies ◽  
Abbas Askar ◽  
Ross P. Church
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Large Fraction ◽  
Galactic Nuclei ◽  
Supermassive Black Holes ◽  
Galactic Centre ◽  
Stellar Clusters ◽  
Stellar Cluster ◽  
Supermassive Black Hole ◽  
Multiple Clusters

AbstractSupermassive black holes are found in most galactic nuclei. A large fraction of these nuclei also contain a nuclear stellar cluster surrounding the black hole. Here we consider the idea that the nuclear stellar cluster formed first and that the supermassive black hole grew later. In particular we consider the merger of three stellar clusters to form a nuclear stellar cluster, where some of these clusters contain a single intermediate-mass black hole (IMBH). In the cases where multiple clusters contain IMBHs, we discuss whether the black holes are likely to merge and whether such mergers are likely to result in the ejection of the merged black hole from the nuclear stellar cluster. In some cases, no supermassive black hole will form as any merger product is not retained. This is a natural pathway to explain those galactic nuclei that contain a nuclear stellar cluster but apparently lack a supermassive black hole; M33 being a nearby example. Alternatively, if an IMBH merger product is retained within the nuclear stellar cluster, it may subsequently grow, e.g. via the tidal disruption of stars, to form a supermassive black hole.

scholarly journals Event Horizon Telescope observations of the jet launching and collimation in Centaurus A

2021 ◽  
Author(s):  
Michael Janssen ◽  
Heino Falcke ◽  
Matthias Kadler ◽  
Eduardo Ros ◽  
Maciek Wielgus ◽  
...  
Keyword(s):  
Black Holes ◽  
Event Horizon ◽  
Galactic Nuclei ◽  
Galactic Centre ◽  
Radio Jets ◽  
Long Baseline ◽  
Wide Range ◽  
Terahertz Frequencies ◽  
Source Structure ◽  
Centaurus A

AbstractVery-long-baseline interferometry (VLBI) observations of active galactic nuclei at millimetre wavelengths have the power to reveal the launching and initial collimation region of extragalactic radio jets, down to 10–100 gravitational radii (rg ≡ GM/c2) scales in nearby sources1. Centaurus A is the closest radio-loud source to Earth2. It bridges the gap in mass and accretion rate between the supermassive black holes (SMBHs) in Messier 87 and our Galactic Centre. A large southern declination of −43° has, however, prevented VLBI imaging of Centaurus A below a wavelength of 1 cm thus far. Here we show the millimetre VLBI image of the source, which we obtained with the Event Horizon Telescope at 228 GHz. Compared with previous observations3, we image the jet of Centaurus A at a tenfold higher frequency and sixteen times sharper resolution and thereby probe sub-lightday structures. We reveal a highly collimated, asymmetrically edge-brightened jet as well as the fainter counterjet. We find that the source structure of Centaurus A resembles the jet in Messier 87 on ~500 rg scales remarkably well. Furthermore, we identify the location of Centaurus A’s SMBH with respect to its resolved jet core at a wavelength of 1.3 mm and conclude that the source’s event horizon shadow4 should be visible at terahertz frequencies. This location further supports the universal scale invariance of black holes over a wide range of masses5,6.

scholarly journals Li isotopes in metal-poor halo dwarfs: a more and more complicated story

2009 ◽  
Vol 5 (S268) ◽  
pp. 201-210
Author(s):  
Monique Spite ◽  
François Spite
Keyword(s):  
Cosmic Rays ◽  
Big Bang ◽  
The Other ◽  
Big Bang Nucleosynthesis ◽  
Lithium Abundance ◽  
The Galaxy ◽  
Li Isotope ◽  
Low Metallicity ◽  
The Big Bang ◽  
Early Galaxy

AbstractThe nuclei of the lithium isotopes are fragile, easily destroyed, so that, at variance with most of the other elements, they cannot be formed in stars through steady hydrostatic nucleosynthesis.The 7Li isotope is synthesized during primordial nucleosynthesis in the first minutes after the Big Bang and later by cosmic rays, by novae and in pulsations of AGB stars (possibly also by the ν process). 6Li is mainly formed by cosmic rays. The oldest (most metal-deficient) warm galactic stars should retain the signature of these processes if, (as it had been often expected) lithium is not depleted in these stars. The existence of a “plateau” of the abundance of 7Li (and of its slope) in the warm metal-poor stars is discussed. At very low metallicity ([Fe/H] < −2.7dex) the star to star scatter increases significantly towards low Li abundances. The highest value of the lithium abundance in the early stellar matter of the Galaxy (logϵ(Li) = A(7Li) = 2.2 dex) is much lower than the the value (logϵ(Li) = 2.72) predicted by the standard Big Bang nucleosynthesis, according to the specifications found by the satellite WMAP. After gathering a homogeneous stellar sample, and analysing its behaviour, possible explanations of the disagreement between Big Bang and stellar abundances are discussed (including early astration and diffusion). On the other hand, possibilities of lower productions of 7Li in the standard and/or non-standard Big Bang nucleosyntheses are briefly evoked.A surprisingly high value (A(6Li)=0.8 dex) of the abundance of the 6Li isotope has been found in a few warm metal-poor stars. Such a high abundance of 6Li independent of the mean metallicity in the early Galaxy cannot be easily explained. But are we really observing 6Li?

scholarly journals Unified Explanation of Big Bang, Inflation, Charged Black Hole Decay, Galaxy Formation, Proton Spin Crisis and Elementary Particle Masses

2021 ◽  
Author(s):  
Jae-Kwang Hwang
Keyword(s):  
Black Holes ◽  
Euclidean Space ◽  
Big Bang ◽  
Space Time ◽  
Proton Spin ◽  
Gravitational Forces ◽  
Normal Matter ◽  
Dark Matters ◽  
Spin Crisis ◽  
The Big Bang

Space-time evolution is briefly explained by using the 3-dimensional quantized space model (TQSM) based on the 4-dimensional (4-D) Euclidean space. The energy (E=cDtDV), charges (|q|= cDt) and absolute time (ct) are newly defined based on the 4-D Euclidean space. The big bang is understood by the space-time evolution of the 4-D Euclidean space but not by the sudden 4-D Minkowski space-time creation. The big bang process created the matter universe with the positive energy and the partner anti-matter universe with the negative energy from the CPT symmetry. Our universe is the matter universe with the negative charges of electric charge (EC), lepton charge (LC) and color charge (CC). This first universe is made of three dark matter -, lepton -, and quark - primary black holes with the huge negative charges which cause the Coulomb repulsive forces much bigger than the gravitational forces. The huge Coulomb forces induce the inflation of the primary black holes, that decay to the super-massive black holes. The dark matter super-massive black holes surrounded by the normal matters and dark matters make the galaxies and galaxy clusters. The spiral arms of galaxies are closely related to the decay of the 3-D charged normal matter black holes to the 1-D charged normal matter black holes. The elementary leptons and quarks are created by the decay of the normal matter charged black holes, that is caused by the Coulomb forces much stronger than the gravitational forces. The Coulomb forces are very weak with the very small Coulomb constants (k1(EC) = kdd(EC) ) for the dark matters and very strong with the very big Coulomb constants (k2(EC) = knn(EC)) for the normal matters because of the non-communication of the photons between the dark matters and normal matters. The photons are charge dependent and mass independent. But the dark matters and normal matters have the similar and very weak gravitational forces because of the communication of the gravitons between the dark matters and normal matters. The gravitons are charge independent and mass dependent. Note that the three kinds of charges (EC, LC and CC) and one kind of mass (m) exist in our matter universe. The dark matters, leptons and quarks have the charge configurations of (EC), (EC,LC) and (EC,LC,CC), respectively. Partial masses of elementary fermions are calculated, and the proton spin crisis is explained. The charged black holes are not the singularities.

scholarly journals Future searches for free and bound n → n̅ transformations

2019 ◽  
Vol 219 ◽  
pp. 07005 ◽  
Author(s):  
Albert Young ◽  
Joshua Barrow
Keyword(s):  
High Energy Physics ◽  
Complex Dynamics ◽  
Rare Event ◽  
Baryon Number ◽  
High Energy ◽  
Big Bang ◽  
Fine Tuning ◽  
Transformation Rate ◽  
Baryon Number Violation ◽  
The Big Bang

Baryon number violation, a key, non-perturbative prediction of the Standard Model (SM) via electroweak instantons (sphalerons), has never been definitively observed. However, its relationship to baryogenesis is obscure, and, within the context of the SM, seems to require fine tuning and complex dynamics to occur mere instants after the chaos of the Big Bang began. Post-sphaleron baryogenesis (PSB), a SM extension first proposed by Babu et al. in 2006, seems to compellingly quell many of these theoretical conundrums while effectively predicting the baryon abundance, and simultaneously offering a tantalizing experimental observable: neutron–antineutron transformations (n → n̅). This rare event, a phenomena similar to meson oscillations, can be thought of as a form of dinucleon decay, and is hypothesized to occur for both the free and bound neutron; what's more, within the context of PSB, there exits an upper limit on the free neutron transformation rate. The subject of the relatedness of the free and bound rates promises a wealth of exciting nuclear and high-energy physics, and the complimentary nature of both types of experimental searches argues for their mutual necessity. In this paper, we briefly discuss the physics of the transformation, and our groups' plans to search for this critically important phenomena using both the free and bound neutron.

Deuterium in the Galaxy

1977 ◽  
Vol 3 (2) ◽  
pp. 100-101 ◽  
Author(s):  
R. D. Brown
Keyword(s):  
Great Majority ◽  
Big Bang ◽  
Baryon Density ◽  
The Galaxy ◽  
Mass Fractions ◽  
Expansion Of The Universe ◽  
Sensitive Function ◽  
The Big Bang ◽  
Deuterium Production ◽  
The Universe

There have been a number of attempts made in the last decade or two to observe deuterium in parts of the universe other than here in Earth. It is of interest merely to detect deuterium elsewhere just as it is to detect the occurrence of any nuclide. However in the case of deuterium there is a special interest because in big-bang cosmologies the great majority of deuterium in the universe is considered to have been formed in the initial fireball (Wagoner, 1973). Any observation of the present abundance of deuterium thus might give information about the very early stages of the creation of the universe. Detailed studies of nucleosynthesis during the early expansion of hot big-bang universes have however indicated a particular feature of deuterium production. (Fig. 1) The mass fraction produced X(D) is a very sensitive function of the size of the universe, as measured say by the present baryon density ϱb. Other nuclides that are mainly produced in the early expansion, such as 4He, have mass fractions less dependent on ϱb. Thus if we adopt the big-bang model for our universe we can determine ϱb from observations of X(D). Apart from any intrinsic interest in the present density of the’universe, there is considerable interest in whether the value is great enough for the present expansion to halt and go over to a collapse — or so small that the expansion of the universe will go on forever.

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