scholarly journals Galaxy Formation and Large-Scale Structures in a Two-Component Dark Matter Scenario

1988 ◽  
Vol 130 ◽  
pp. 427-428
Author(s):  
Masayuki Umemura
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Large Scale ◽  
Dwarf Galaxies ◽  
Large Scale Structures ◽  
Two Component ◽  
Scale Structures

A universe dominated by both hot (HDM) and cold dark matter (CDM) is proposed. In this context, the new features for the formation of dwarf galaxies, Lyα clouds, galaxies, and large-scale structures are presented.

scholarly journals Large-Scale Structure in the Universe: Spatial Distribution and Peculiar Velocities

1987 ◽  
Vol 124 ◽  
pp. 335-348
Author(s):  
Neta A. Bahcall
Keyword(s):  
Dark Matter ◽  
Spatial Distribution ◽  
Large Scale ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Clusters Of Galaxies ◽  
Large Scale Structures ◽  
Peculiar Velocities ◽  
Scale Structures ◽  
The Universe

The evidence for the existence of very large scale structures, ∼ 100h−1Mpc in size, as derived from the spatial distribution of clusters of galaxies is summarized. Detection of a ∼ 2000 kms−1 elongation in the redshift direction in the distribution of the clusters is also described. Possible causes of the effect are peculiar velocities of clusters on scales of 10–100h−1Mpc and geometrical elongation of superclusters. If the effect is entirely due to the peculiar velocities of clusters, then superclusters have masses of order 1016.5M⊙ and may contain a larger amount of dark matter than previously anticipated.

scholarly journals Cosmological signatures of dark sector physics: the evolution of haloes and spin alignment

2020 ◽  
Vol 492 (2) ◽  
pp. 2369-2382 ◽  
Author(s):  
Absem W Jibrail ◽  
Pascal J Elahi ◽  
Geraint F Lewis
Keyword(s):  
Dark Matter ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Dark Sector ◽  
Large Scale Structures ◽  
Cosmic Evolution ◽  
The Standard Model ◽  
Scale Structures ◽  
And Migration ◽  
Matter Energy

ABSTRACT The standard cosmological paradigm currently lacks a detailed account of physics in the dark sector, the dark matter and energy that dominate cosmic evolution. In this paper, we consider the distinguishing factors between three alternative models – warm dark matter, quintessence, and coupled dark matter–energy – and lambda cold dark matter (ΛCDM) through numerical simulations of cosmological structure formation. Key halo statistics – halo spin/velocity alignment between large-scale structure and neighbouring haloes, halo formation time, and migration – were compared across cosmologies within the redshift range 0 ≤ z ≤ 2.98. We found the alignment of halo motion and spin to large-scale structures and neighbouring haloes to be similar in all cosmologies for a range of redshifts. The search was extended to low-density regions, avoiding non-linear disturbances of halo spins, yet very similar alignment trends were found between cosmologies, which are difficult to characterize and use as a probe of cosmology. We found that haloes in quintessence cosmologies form earlier than their ΛCDM counterparts. Relating this to the fact that such haloes originate in high-density regions, such findings could hold clues to distinguishing factors for the quintessence cosmology from the standard model. However, in general, halo statistics are not an accurate probe of the dark sector physics.

scholarly journals EZOA – a catalogue of EBHIS H i-detected galaxies in the northern Zone of Avoidance

2019 ◽  
Vol 489 (2) ◽  
pp. 2907-2922 ◽  
Author(s):  
A C Schröder ◽  
L Flöer ◽  
B Winkel ◽  
J Kerp
Keyword(s):  
Large Scale ◽  
Near Infrared ◽  
Dwarf Galaxies ◽  
High Rate ◽  
Infrared Images ◽  
Large Scale Structures ◽  
The Past ◽  
Northern Zone ◽  
Scale Structures ◽  
Zone Of Avoidance

ABSTRACT We present a catalogue of galaxies in the northern Zone of Avoidance (ZoA), extracted from the shallow version of the blind H i survey with the Effelsberg 100 m radio telescope, EBHIS, that has a sensitivity of 23 mJy beam−1 at 10.24 km s−1 velocity resolution. The catalogue comprises 170 detections in the region δ ≥ −5° and |b| < 6°. About a third of the detections (N = 67) have not been previously recorded in H i. While 29 detections have no discernible counterpart at any wavelength other than H i, 48 detections (28 per cent) have a counterpart visible on optical or near-infrared images but are not recorded as such in the literature. New H i detections were found as close as 7.5 Mpc (EZOA J2120+45), and at the edge of the Local Volume, at 10.1 Mpc, we have found two previously unknown dwarf galaxies (EZOA J0506+31 and EZOA J0301+56). Existing large-scale structures crossing the northern ZoA have been established more firmly by the new detections, with the possibility of new filaments. We conclude that the high rate of 39 per cent new H i detections in the northern ZoA, which has been extensively surveyed with targeted observations in the past, proves the power of blind H i surveys. The full EBHIS survey, which will cover the full northern sky with a sensitivity comparable to the HIPASS survey of the southern sky, is expected to add many new detections and uncover new structures in the northern ZoA.

Cosmic structure

2014 ◽  
Vol 23 (10) ◽  
pp. 1430021
Author(s):  
Marc Davis
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Dwarf Galaxies ◽  
Initial Conditions ◽  
Cluster Formation ◽  
Acoustic Oscillations ◽  
Highly Nonlinear ◽  
History Of

The history of cosmic structure goes back to the time of Einstein's youth, although few scientists actually thought of the problem of galaxy and cluster formation. The data and ideas were collected slowly as astronomers slowly realized the nature of the problem of large-scale structure. This paper will review several of the key episodes in the history of the field. Starting with the discovery of dark matter in the 30s, the CMBR discovery in the 1960s to the idea of an early episode of inflation in the 1980s, the field has had an acceleration of discovery. In the 80s it was realized that the initial conditions of the universe were specified by the cold dark matter (CDM). Now initial conditions for the formation of structure could be specified for any type of dark matter. With the advent of computing resources, highly nonlinear phases of galaxy formation could be simulated and scientists could ask whether cold dark matter was the correct theory, even on the scale of dwarf spheroidal galaxies, or do the properties of the dwarfs require a different type of dark matter? In an idiosyncratic list, we review several of the key events of the history of cosmic structure, including the first measurements of ξ(r), then the remarkable success of Λ CDM explanations of the large-scale universe. We next turn to velocity fields, the large-scale flow problem, a field which was so promising 20 years ago, and to the baryon acoustic oscillations, a field of remarkable promise today. We review the problem of dwarf galaxies and Lyman-α absorption systems, asking whether the evidence is pointing toward a major switch in our understanding of the nature of dark matter. Finally, we discuss flux anomalies in multiply-lensed systems, which set constraints on the number of dwarf galaxies associated with the lensing galaxy, a topic that is now very interesting since simulations have indicated there should be hundreds of dwarfs orbiting the Milky Way, rather than the 10 that are known. It is quite remarkable that many of the today's results are dependent on techniques first used by Einstein.

scholarly journals On the Large-Scale Structures Formed by Wakes of Open Cosmic Strings

1990 ◽  
Vol 124 ◽  
pp. 677-681
Author(s):  
Tetsuya Hara ◽  
Shoji Morioka ◽  
Shigeru Miyoshi
Keyword(s):  
Galaxy Formation ◽  
Large Scale ◽  
Cosmic Strings ◽  
Large Scale Structures ◽  
Scale Structures ◽  
The Universe

Large-scale structures of the universe have been variously described as sheetlike, filamentary, cellular, bubbles or spongelike. Recently cosmic strings become one of viable candidates for galaxy formation scenario, and some of the large-scale structures seem to be simply explained by the open cosmic strings).

scholarly journals Surveying for Dwarf Galaxies Within Voids FN2 and FN8

2014 ◽  
Vol 11 (S308) ◽  
pp. 614-615
Author(s):  
Stephen McNeil ◽  
Chris Draper ◽  
J. Ward Moody
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Large Scale ◽  
Dwarf Galaxies ◽  
Low Density ◽  
Dark Matter Halos ◽  
Void Volumes ◽  
Four Square ◽  
Large Scale Structure Formation

AbstractThe presence or absence of dwarf galaxies with Mr' > -14 in low-density volumes correlates with dark matter halos and how they affect galaxy formation. We are conducting a redshifted Hα imaging survey for dwarf galaxies with Mr' > -13 in the heart of the well-defined voids FN2 and FN8 using the KPNO 4m Mayall telescope and Mosaic Imager. These data have furnished over 600 strong candidates in a four square degree area. Follow-up spectra finding none of these candidates to be within the void volumes will constrain the dwarf population there to be 2 to 8% of the cosmic mean. Conversely, finding even one Hα dwarf in the void heart will challenge several otherwise successful theories of large-scale structure formation.

scholarly journals Explosive Origins of Large-Scale Structures

1988 ◽  
Vol 130 ◽  
pp. 321-329
Author(s):  
Jeremiah P. Ostriker
Keyword(s):  
Galaxy Formation ◽  
Large Scale ◽  
Cosmic Strings ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Energy Output ◽  
Galaxy Groups ◽  
Large Scale Structures ◽  
The Galaxy ◽  
Scale Structures

Large scale structures up to 5h−1 mpc, the galaxy-galaxy correlation length and the size of typical galaxy groups and clusters, can be produced quite naturally from explosions originating in young galaxies (Ostriker and Cowie, 1981: “OC”) or quasars (Ikeuchi, 1981: “I”) with energy output of 1061 ergs. But very large-scale structure in the 25 mpc −50 mpc range possibly indicated by cluster-cluster correlations (Bahcall, 1987a), can only be produced by much more energetic events of 1065 ergs which are far beyond the output of any objects currently known. This follows simply from the dimensional arguments which give R = c(Eσ/t2)0.2 implicit in the classic Seldov-Taylor solution and cosmological analogs (cf Ostriker, 1986). Thus very large scale structure can only be produced by explosions if many small ones can coalesce suitably at early epochs (OC) or single giant events are produced by exotic objects such as superconducting cosmic strings (Ostriker, Thompson and Witten 1986: “OTW”). If however these large events do occur, then many specific properties of very large-scale structures will be produced quite naturally (cf Bahcall, 1987b, Weinberg, Ostriker and Dekel, 1987 “WOD”). Before discussing these points, it is appropriate to say a few words on the importance of hydrodynamics in general and explosions in particular, since the latter will certainly be a consequence of galaxy formation even if they are not the primary cause.

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