scholarly journals Origin and evolution of structure and nucleosynthesis for galaxies in the local group

2014 ◽  
Vol 29 (14) ◽  
pp. 1430012 ◽  
Author(s):  
G. J. Mathews ◽  
A. Snedden ◽  
L. A. Phillips ◽  
I.-S. Suh ◽  
J. Coughlin ◽  
...  
Keyword(s):  
Dark Matter ◽  
Local Group ◽  
Galactic Halo ◽  
Galactic Plane ◽  
Dwarf Galaxies ◽  
Gravitational Interaction ◽  
Galactic Halos ◽  
Origin And Evolution ◽  
Spiral Density Waves ◽  
Streaming Flows

The Milky Way is the product of a complex evolution of generations of mergers, collapse, star formation, supernova and collisional heating, radiative and collisional cooling, and ejected nucleosynthesis. Moreover, all of this occurs in the context of the cosmic expansion, the formation of cosmic filaments, dark matter halos, spiral density waves, and emerging dark energy. In this review we summarize observational evidence and discuss recent calculations concerning the formation, evolution nucleosynthesis in the galaxies of the Local Group (LG). In particular, we will briefly summarize observations and simulations for the dwarf galaxies and the two large spirals of the LG. We discuss how galactic halos form within the dark matter filaments that define a super-galactic plane. Gravitational interaction along this structure leads to streaming flows toward the two dominant galaxies in the cluster. These simulations and observations also suggest that a significant fraction of the Galactic halo formed as at large distances and then arrived later along these streaming flows. We also consider the insight provided by observations and simulations of nucleosynthesis both within the galactic halo and dwarf galaxies in the LG.

scholarly journals Formation of massive globular clusters with dark matter and its implication on dark matter annihilation

2020 ◽  
Vol 496 (1) ◽  
pp. L70-L74
Author(s):  
Henriette Wirth ◽  
Kenji Bekki ◽  
Kohei Hayashi
Keyword(s):  
Dark Matter ◽  
Observational Studies ◽  
Globular Clusters ◽  
Galactic Halo ◽  
Dwarf Galaxies ◽  
Large Range ◽  
Dark Matter Annihilation ◽  
Central Regions ◽  
Γ Ray ◽  
The Masses

ABSTRACT Recent observational studies of γ-ray emission from massive globular clusters (GCs) have revealed possible evidence of dark matter (DM) annihilation within GCs. It is, however, still controversial whether the emission comes from DM or from millisecond pulsars. We here present the new results of numerical simulations, which demonstrate that GCs with DM can originate from nucleated dwarfs orbiting the ancient Milky Way. The simulated stripped nuclei (i.e. GCs) have the central DM densities ranging from 0.1 to several M⊙ pc−3, depending on the orbits and the masses of the host dwarf galaxies. However, GCs born outside the central regions of their hosts can have no/little DM after their hosts are destroyed and the GCs become the Galactic halo GCs. These results suggest that only GCs originating from stellar nuclei of dwarfs can possibly have DM. We further calculate the expected γ-ray emission from these simulated GCs and compare them to observations of ω Cen. Given the large range of DM densities in the simulated GCs, we suggest that the recent possible detection of DM annihilation from GCs should be more carefully interpreted.

scholarly journals Red Halos of Galaxies – Reservoirs of Baryonic Dark Matter?

2007 ◽  
Vol 3 (S244) ◽  
pp. 17-25 ◽  
Author(s):  
E. Zackrisson ◽  
N. Bergvall ◽  
C. Flynn ◽  
G. Östlin ◽  
G. Micheva ◽  
...  
Keyword(s):  
Dark Matter ◽  
Stellar Population ◽  
Local Group ◽  
Dwarf Galaxies ◽  
Mass Function ◽  
Initial Mass Function ◽  
High Mass ◽  
Disk Galaxies ◽  
Near Ir ◽  
Baryonic Dark Matter

AbstractDeep optical/near-IR surface photometry of galaxies outside the Local Group have revealed faint and very red halos around objects as diverse as disk galaxies and starbursting dwarf galaxies. The colours of these structures are too extreme to be reconciled with stellar populations similar to those seen in the stellar halos of the Milky Way or M31, and alternative explanations like dust reddening, high metallicities or nebular emission are also disfavoured. A stellar population obeying an extremely bottom-heavy initial mass function (IMF), is on the other hand consistent with all available data. Because of its high mass-to-light ratio, such a population would effectively behave as baryonic dark matter and could account for some of the baryons still missing in the low-redshift Universe. Here, we give an overview of current red halo detections, alternative explanations for the origin of the red colours and ongoing searches for red halos around types of galaxies for which this phenomenon has not yet been reported. A number of potential tests of the bottom-heavy IMF hypothesis are also discussed.

Constraints on baryonic dark matter in the Galactic halo and Local Group

1992 ◽  
Vol 388 ◽  
pp. 354 ◽  
Author(s):  
Douglas Richstone ◽  
Andrew Gould ◽  
Puragra Guhathakurta ◽  
Chris Flynn
Keyword(s):  
Dark Matter ◽  
Local Group ◽  
Galactic Halo ◽  
Baryonic Dark Matter

scholarly journals H I IN LOCAL GROUP DWARF GALAXIES AND STRIPPING BY THE GALACTIC HALO

2009 ◽  
Vol 696 (1) ◽  
pp. 385-395 ◽  
Author(s):  
Jana Grcevich ◽  
Mary E Putman
Keyword(s):  
Local Group ◽  
Galactic Halo ◽  
Dwarf Galaxies

scholarly journals Young Stars far from the Galactic Plane: Runaways from Clusters

2004 ◽  
Vol 191 ◽  
pp. 121-127
Author(s):  
Christine Allen ◽  
T.D. Kinman
Keyword(s):  
Star Formation ◽  
Galactic Halo ◽  
Galactic Plane ◽  
Dynamical Evolution ◽  
Young Stars ◽  
Formation Mechanisms ◽  
Conventional View ◽  
Spiral Density Waves ◽  
Ejection Mechanism

AbstractQuite recently, a significant number of OB stars far from the galactic plane have been found, situated at z- distances ranging from several hundreds of pc to several kpc. The short lifetimes of these stars pose problems for their interpretation in terms of the standard picture of star formation. Different mechanisms have been put forward to explain the existence of these stars, either within the conventional view, or postulating star formation in the galactic halo itself. These mechanisms range from arguing that they are misidentified evolved or abnormal stars, to postulating powerful ejection mechanisms for young disk stars; in situ formation also admits several variants. We have collected from the literature a list of young stars far from the plane, for which the evidence of youth seems convincing. We discuss two possible formation mechanisms for these stars: ejection from the plane as the result of dynamical evolution of small clusters (Poveda et al. 1967) and in situ formation, via induced shocks created by spiral density waves (Martos et al. 1999). We compute galactic orbits for these stars, and identify the stars that could be explained by one or the other mechanism. We find that about 90 percent of the stars can be accounted for by the cluster ejection mechanism, that is, they can be regarded as runaway stars in the galactic halo.

scholarly journals Constraints on Interactions and Mergers from dSph Galaxies and Globular Clusters

1999 ◽  
Vol 186 ◽  
pp. 52-52
Author(s):  
E.K. Grebel
Keyword(s):  
Globular Clusters ◽  
Milky Way ◽  
Local Group ◽  
Galactic Halo ◽  
Dwarf Galaxies ◽  
Thick Disk ◽  
History Of

Observations at high redshifts are revealing numerous interactions and ongoing mergers. Our own Milky Way is currently merging with the Sagittarius dwarf spheroidal (dSph) galaxy. Past mergers with dwarf galaxies may have contributed significantly to the Galactic halo and possibly to the thick disk. The properties of Local Group dSphs and halo globular clusters impose constraints on the merger history of the Milky Way.

scholarly journals Large-scale Gas Dynamical Processes Affecting the Origin and Evolution of Gaseous Galactic Halos

1991 ◽  
Vol 144 ◽  
pp. 417-428
Author(s):  
Paul R. Shapiro
Keyword(s):  
Absorption Line ◽  
Large Scale ◽  
Galactic Halo ◽  
Galactic Disk ◽  
High Redshift ◽  
Cloud Formation ◽  
Galactic Halos ◽  
Origin And Evolution ◽  
Mhd Simulations ◽  
Halo Gas

Observations of galactic halo gas are consistent with an interpretation in terms of the galactic fountain model in which supernova heated gas in the galactic disk escapes into the halo, radiatively cools and forms clouds which fall back to the disk. The results of a new study of several large-scale gas dynamical effects which are expected to occur in such a model for the origin and evolution of galactic halo gas will be summarized, including the following: (1) nonequilibrium absorption line and emission spectrum diagnostics for radiatively cooling halo gas in our own galaxy, as well the implications of such absorption line diagnostics for the origin of quasar absorption lines in galactic halo clouds of high redshift galaxies; (2) numerical MHD simulations and analytical analysis of large-scale explosions and superbubbles in the galactic disk and halo; (3) numerical MHD simulations of halo cloud formation by thermal instability, with and without magnetic field; and (4) the effect of the galactic fountain on the galactic dynamo.

scholarly journals Analysis of repulsive central universal force field on solar and galactic dynamics

Open Physics ◽  
2019 ◽  
Vol 17 (1) ◽  
pp. 364-372
Author(s):  
Kamal Barghout
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Force Field ◽  
Galactic Halo ◽  
Galactic Plane ◽  
Yukawa Potential ◽  
Galactic Rotation ◽  
Gravitational Theories ◽  
Universal Force Field ◽  
Modify Gravity

AbstractRecent astrophysical observations hint toward the need for an extended theory of gravity to explain puzzles presented by the standard cosmological model such as the need for dark matter and dark energy to understand the dynamics of the cosmos. This paper investigates the effect of a repulsive central universal force field on the behavior of celestial objects. Negative tidal effect on the solar and galactic orbits, like that experienced by Pioneer spacecrafts, was derived from the central force and was shown to manifest itself as dark matter and dark energy. Vertical oscillation of the sun about the galactic plane was modeled as simple harmonic motion driven by the repulsive force. The proposed universal field was used to infer the shape of dark matter halos as generated from a planar component of the universal force and to explain galactic warp, galactic halo density, and galactic rotation curves. It was found that the repulsive field addition to Newton’s gravity mimics the Yukawa potential correction employed by many current gravitational theories that modify gravity.

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