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Small-JASMINE will provide astrometric data with high precisions in a near infrared band for stars in the Galactic nuclear bulge and other specific targets. The primary scientific objective is to carry out the Galactic Center Archeology by exploring the Galactic nuclear bulge that leads to the elucidation of the Galactic structures and the evolution of the supermassive black hole at the center. Small-JASMINE has been selected as the unique candidate for the competitive 3rd M-class science satellite mission by ISAS/JAXA. The launch date is mid-2020s.

Galaxy mergers produce pairs of supermassive black holes (SMBHs), which may be witnessed as dual quasars if both SMBHs are rapidly accreting. The kiloparsec (kpc)-scale separation represents a physical regime sufficiently close for merger-induced effects to be important 1 yet wide enough to be directly resolvable with the facilities currently available. Whereas many kpc-scale, dual active galactic nuclei—the low-luminosity counterparts of quasars—have been observed in low-redshift mergers 2 , no unambiguous dual quasar is known at cosmic noon ( z  ≈ 2), the peak of global star formation and quasar activity 3 , 4 . Here we report multiwavelength observations of Sloan Digital Sky Survey (SDSS) J0749 + 2255 as a kpc-scale, dual-quasar system hosted by a galaxy merger at cosmic noon ( z  = 2.17). We discover extended host galaxies associated with the much brighter compact quasar nuclei (separated by 0.46″ or 3.8 kpc) and low-surface-brightness tidal features as evidence for galactic interactions. Unlike its low-redshift and low-luminosity counterparts, SDSS J0749 + 2255 is hosted by massive compact disk-dominated galaxies. The apparent lack of stellar bulges and the fact that SDSS J0749 + 2255 already follows the local SMBH mass–host stellar mass relation, suggest that at least some SMBHs may have formed before their host stellar bulges. While still at kpc-scale separations where the host-galaxy gravitational potential dominates, the two SMBHs may evolve into a gravitationally bound binary system in around 0.22 Gyr. The authors report multiwavelength observations of SDSS J0749 + 2255, hosted by massive compact disk-dominated galaxies, as a kpc-scale, dual-quasar system hosted by a galaxy merger at cosmic noon.

Lonely planets guide Gravitational microlensing observations in the direction of the Galactic Bulge have come up with a surprising result: the discovery of ten previously unknown extrasolar planets that are not bound to host stars. These seemingly free-ranging Jupiter-mass objects could be in very distant orbits around host stars, but no hosts could be detected within a distance of 10 astronomical units from the free-floating planets. It seems possible, therefore, that planet scattering is a routine part of the planet formation process. Since 1995, more than 500 exoplanets have been detected using different techniques 1 , 2 , of which 12 were detected with gravitational microlensing 3 , 4 . Most of these are gravitationally bound to their host stars. There is some evidence of free-floating planetary-mass objects in young star-forming regions 5 , 6 , 7 , 8 , but these objects are limited to massive objects of 3 to 15 Jupiter masses with large uncertainties in photometric mass estimates and their abundance. Here, we report the discovery of a population of unbound or distant Jupiter-mass objects, which are almost twice ( ) as common as main-sequence stars, based on two years of gravitational microlensing survey observations towards the Galactic Bulge. These planetary-mass objects have no host stars that can be detected within about ten astronomical units by gravitational microlensing. However, a comparison with constraints from direct imaging 9 suggests that most of these planetary-mass objects are not bound to any host star. An abrupt change in the mass function at about one Jupiter mass favours the idea that their formation process is different from that of stars and brown dwarfs. They may have formed in proto-planetary disks and subsequently scattered into unbound or very distant orbits.

We address the galaxy rotation curves through the Yukawa gravitational potential emerging as a correction of the Newtonian potential in extended theories of gravity. On the one hand, we consider the contribution of the galactic bulge, galactic disk, and the dark matter halo of the Navarro–Frenk–White profile, in the framework of the standard Λ CDM model. On the other hand, we use modified Yukawa gravity to show that the rotational velocity of galaxies can be addressed successfully without the need for dark matter. In Yukawa gravity, we recover MOND and show that dark matter might be seen as an apparent effect due to the modification of the law of gravitation in terms of two parameters: the coupling constant α and the characteristic length λ . We thus test our theoretical scenario using the Milky Way and M31 rotation velocity curves. In particular, we place observational constraints on the free parameters of Yukawa cosmology through the Monte Carlo method and then compare our results with the predictions of the Λ CDM paradigm by making use of Bayesian information criteria. Specifically, we find that λ is constrained to be of the order of kpc, while cosmological data suggest λ of the order of Gpc. To explain this discrepancy, we argue that there is a fundamental limitation in measuring λ due to the role of quantum mechanics on cosmological scales.

Most stars in today’s Universe reside within spheroids, which are bulges of spiral galaxies and elliptical galaxies 1 , 2 . Their formation is still an unsolved problem 3 , 4 – 5 . Infrared/submillimetre-bright galaxies at high redshifts 6 have long been suspected to be related to spheroid formation 7 , 8 , 9 , 10 , 11 – 12 . Proving this connection has been hampered so far by heavy dust obscuration when focusing on their stellar emission 13 , 14 – 15 or by methodologies and limited signal-to-noise ratios when looking at submillimetre wavelengths 16 , 17 . Here we show that spheroids are directly generated by star formation within the cores of highly luminous starburst galaxies in the distant Universe. This follows from the ALMA submillimetre surface brightness profiles, which deviate substantially from those of exponential disks, and from the skewed-high axis-ratio distribution. Most of these galaxies are fully triaxial rather than flat disks: the ratio of the shortest to the longest of their three axes is half, on average, and increases with spatial compactness. These observations, supported by simulations, reveal a cosmologically relevant pathway for in situ spheroid formation through starbursts that is probably preferentially triggered by interactions (and mergers) acting on galaxies fed by non-coplanar gas accretion streams. Deep ALMA archival observations of submillimetre-bright galaxies at high redshifts show that spheroidal bulges formed much earlier than expected and are directly generated by star formation within the cores of highly luminous starburst galaxies.

In a key contribution McGaugh et al. demonstrate that baryonic galaxies in galaxy clusters and stars in all kinds of galaxies of different size and mass lie on a universal curve, connecting the observed acceleration g obs and the parameter g bar , associated with acceleration due to baryonic matter: g obs = f ( g bar ). No physical understanding based on dark matter has been provided why this universal curve should exist. We suggest a quantum theory of gravity based on Einstein-Hilbert action and gravonons (local gravitons) in high hidden space dimensions (Einstein-Hilbert-Hidden-Dimensions EHHD), in which dark matter and dark energy terms involving gravonons emerge in the interaction Lagrangian. Entanglement of gravonons with matter fields (hydrogen atoms in deformation resonances similar to ‘micro black holes’) leads to the localization of quantum particles as experimentally observable beables in three dimensions. A law, bridging the physics at cosmological distances with the physics on atomic scale in the ‘micro black holes’ is derived for the relationship between the number of gravonons and g bar Using the Generalized Ehrenfest Theorem (GET) we get the proper result of the rate of generation of gravonons, hence of beabled matter, and the universal galaxy rotational curve. The deviation of the observed acceleration of stars g obs from the baryonic acceleration g bar in the periphery of galaxies far from the central bulge and for g bar < g † is due to the increasing number of gravonons in the deformation resonances, i.e. dark matter. Closer to the central bulge strong gravity due to Newton force destroys the ‘black holes’. Dark matter effects are suppressed, the observed acceleration g obs merges with g bar The value of g † is determined and its physical meaning is elucidated. The universality of McGaugh’s curve is explained by the fact that the processes described so far occur in enormously many similar non-interacting deformation resonances.

Globular clusters a mixed bag The globular star clusters that orbit the Milky Way are regarded as the best approximations we have of stellar populations of uniform age and identical composition, recording stellar evolution since the birth of our Galaxy. The most luminous of these clusters though, ω Centauri, has long been recognized as an exception to this trend, containing multiple stellar populations with a significant spread in iron abundance and ages. Two groups report the discovery of further global clusters with mixed populations. Lee et al . confirm the suspicion that the massive global cluster M22 contains distinct multiple populations with different calcium abundances, as do several other clusters in their sample. Ferraro et al . report that Terzan 5, a globular cluster-like system in the Galactic bulge, has two populations with different iron content and ages. These findings suggest that ω Cen, M22, Terzan 5 and other similar clusters are the relics of dwarf galaxies and other primordial bodies that merged to eventually form the Milky Way. ω Centauri is the only globular star cluster in the Galactic halo known to have multiple stellar populations with a significant spread in iron abundance and age. But now Terzan 5, a globular-cluster-like system in the Galactic bulge, is reported to have two stellar populations with different iron contents and ages. So Terzan 5 could be the surviving remnant of one of the primordial building blocks which are thought to merge and form galaxy bulges. Globular star clusters are compact and massive stellar systems old enough to have witnessed the entire history of our Galaxy, the Milky Way. Although recent results 1 , 2 , 3 suggest that their formation may have been more complex than previously thought, they still are the best approximation to a stellar population formed over a relatively short timescale (less than 1 Gyr) and with virtually no dispersion in the iron content. Indeed, only one cluster-like system (ω Centauri) in the Galactic halo is known to have multiple stellar populations with a significant spread in iron abundance and age 4 , 5 . Similar findings in the Galactic bulge have been hampered by the obscuration arising from thick and varying layers of interstellar dust. Here we report that Terzan 5, a globular-cluster-like system in the Galactic bulge, has two stellar populations with different iron contents and ages. Terzan 5 could be the surviving remnant of one of the primordial building blocks that are thought to merge and form galaxy bulges.

The Positron Puzzle is a half-century old conundrum about the origin of the Galactic γ-ray emission line at photon energies of 511 keV, and the shape of its morphology, showing a bulge-to-disk luminosity ratio of ∼1 – unlike any astrophysical source distribution. Positrons (e+s) that have been cooled to the eV scale capture electrons (e−s) and form the intermediate bound state of Positronium (Ps) which decays on a nano-second timescale into two or three photons. Assuming the emission to originate from the Galactic bulge, centre, and disk, a visible annihilation rate in the Milky Way of ∼5×1043e+s−1 has to be explained, either by a quasi-steady state of production and annihilation, or by possibly multiple burst-like events that flood the Galaxy with e+s, then fading away on a Myr timescale.In this paper, I will review what the real Positron Puzzle is, where data and simulations have been used inadequately which resulted in false claims and an apparent quandary, what we really know and absolutely not know about the topic, and how this epistemic problem might be advancing.

Three three-component (bulge, disk, halo) model Galactic gravitational potentials differing by the expression for the dark matter halo are considered. The central (bulge) and disk components are described by the Miyamoto–Nagai expressions. The Allen–Santillán (I), Wilkinson–Evans (II), and Navarro–Frenk–White (III) models are used to describe the halo. A set of present-day observational data in the range of Galactocentric distances R from 0 to 200 kpc is used to refine the parameters of thesemodels. For the Allen–Santillán model, a dimensionless coefficient γ has been included as a sought-for parameter for the first time. In the traditional and modified versions, γ = 2.0 and 6.3, respectively. Both versions are considered in this paper. The model rotation curves have been fitted to the observed velocities by taking into account the constraints on the local matter density ρ ⊙ = 0.1 M ⊙ pc −3 and the force K z =1.1/2 πG = 77 M ⊙ pc −2 acting perpendicularly to the Galactic plane. The Galactic mass within a sphere of radius 50 kpc, M G ( R ≤ 50 kpc) ≈ (0.41 ± 0.12) × 10 12 M ⊙ , is shown to satisfy all three models. The differences between the models become increasingly significant with increasing radius R . In model I, the Galactic mass within a sphere of radius 200 kpc at γ = 2.0 turns out to be greatest among the models considered, M G ( R ≤ 200 kpc) = (1.45 ±0.30)× 10 12 M ⊙ , M G ( R ≤ 200 kpc) = (1.29± 0.14)× 10 12 M ⊙ at γ = 6.3, and the smallest value has been found in model II, M G ( R ≤ 200 kpc) = (0.61 ± 0.12) × 10 12 M ⊙ . In our view, model III is the best one among those considered, because it ensures the smallest residual between the data and the constructed model rotation curve provided that the constraints on the local parameters hold with a high accuracy. Here, the Galactic mass is M G ( R ≤ 200 kpc) = (0.75 ± 0.19) × 10 12 M ⊙ . A comparative analysis with the models by Irrgang et al. (2013), including those using the integration of orbits for the two globular clusters NGC 104 and NGC 1851 as an example, has been performed. The third model is shown to have subjected to a significant improvement.

Dark Matter (DM) is usually studied in connection with rotational curves in the outskirts of the galaxies. However, the role of DM might be different in the galactic bulges and centers where Supermassive Black Holes (SMBHs) dominate the gravitational interaction. Indeed, given the fact that DM is the dominant matter species in the Universe, it is natural to assume a close connection between DM and SMBHs. Here we probe into this possibility by constructing stable objects with fuzzy mass distributions based on standard DM profiles. These astrophysical objects come out in three types: a fuzzy droplet without horizon and fuzzy Black Holes (BHs) with one or two horizons. We emphasize that all objects are solutions of Einstein equations. Their effective potentials which govern the motion of a test body, can display a reasonable similarity to the effective potential of a Schwarzschild BH at the galactic center. Therefore, some of our solutions could, in principle, replace the standard BH-picture of the galactic center and, at the same time, have the advantage that they have been composed of the main matter ingredient of the Universe.