scholarly journals Background Light from Population III Stars

1987 ◽  
Vol 117 ◽  
pp. 414-414
Author(s):  
Jonathan C. McDowell
Keyword(s):  
Dark Matter ◽  
Background Radiation ◽  
Large Fraction ◽  
Rest Mass ◽  
Critical Density ◽  
Density Parameter ◽  
Extragalactic Background Light ◽  
Background Light ◽  
Far Ultraviolet ◽  
The Universe

It has been proposed (e.g. Carr, Bond and Arnett 1984) that the first generation of stars may have been Very Massive Objects (VMOs, of mass above 200 M⊙) which existed at large redshifts and left a large fraction of the mass of the universe in black hole remnants which now provide the dynamical ‘dark matter’. The radiation from these stars would be present today as extragalactic background light. For stars with density parameter Ω* which convert a fraction ϵ of their rest-mass to radiation at a redshift of z, the energy density of background radiation in units of the critical density is ΩR = εΩ* / (1+z). The VMOs would be far-ultraviolet sources with effective temperatures of 105 K. If the radiation is not absorbed, the constraints provided by measurements of background radiation imply (for H =50 km/s/Mpc) that the stars cannot close the universe unless they formed at a redshift of 40 or more. To provide the dark matter (of one-tenth closure density) the optical limits imply that they must have existed at redshifts above 25.

scholarly journals Dark Matter and Cooling Flows

1988 ◽  
Vol 130 ◽  
pp. 429-435
Author(s):  
B. J. Carr ◽  
K. M. Ashman
Keyword(s):  
Elementary Particle ◽  
Dark Matter ◽  
Large Fraction ◽  
Critical Density ◽  
Galactic Halos ◽  
Present Epoch ◽  
Cooling Flows ◽  
The Universe ◽  
Made In

Cosmological arguments suggest that a large fraction of the baryons in the Universe are dark. Although the background dark matter required to make up the critical density would have to consist of some kind of elementary particle, the dark matter in galactic halos could be baryonic. In particular, we argue that it could consist of jupiters made in pregalactic or protogalactic cooling flows. These would be analagous to the cluster cooling flows observed at the present epoch but on a smaller scale.

Particle dark matter direct detection

2016 ◽  
Vol 25 (07) ◽  
pp. 1630018
Author(s):  
Rita Bernabei
Keyword(s):  
Dark Matter ◽  
Particle Physics ◽  
Direct Detection ◽  
Large Fraction ◽  
Future Perspectives ◽  
Poor Knowledge ◽  
The Poor ◽  
Particle Dark Matter ◽  
Interaction Types ◽  
The Universe

Nearly a century of experimental observations and theoretical arguments have pointed out that a large fraction of the Universe is composed by dark matter particles. Many possibilities are open on the nature and interaction types of such relic particles. Moreover, the poor knowledge of many fundamental astrophysical, nuclear and particle physics aspects as well as of some experimental and theoretical parameters, the different used approaches and target materials, etc. make it challenging to understand the implication of some different experimental efforts. Some general arguments are addressed here. Future perspectives are mentioned.

scholarly journals Supersonic relative velocity between dark matter and baryons: A review

2014 ◽  
Vol 23 (08) ◽  
pp. 1430017 ◽  
Author(s):  
Anastasia Fialkov
Keyword(s):  
Dark Matter ◽  
Large Scale ◽  
Background Radiation ◽  
Spectral Lines ◽  
Strong Impact ◽  
Acoustic Oscillations ◽  
Radiation Emission ◽  
Hydrogen Recombination ◽  
Intermediate Redshifts ◽  
The Universe

Our understanding of astrophysical and cosmological phenomena in recent years has improved enormously, thanks to precision measurements of various cosmic signals such as Cosmic Microwave Background radiation, emission of galaxies and dust, spectral lines attributed to various elements, etc. Despite this, our knowledge at intermediate redshifts (10 < z < 1100) remains fragmentary and incomplete, and as a consequence, various physical processes happening between the epochs of hydrogen recombination and reionization remain still highly unconstrained. Moreover, some important fragments of the theoretical description that are less decisive for the universe today, but that had an important impact at intermediate redshifts, have been omitted in some of the studies concerning the universe at high redshifts. One such neglected phenomenon, which is the central topic of this review, is the fact that after hydrogen recombination the large-scale baryons and dark matter fluctuations had supersonic relative velocities. The relative velocities between dark matter and baryons formally introduce a second-order effect on the standard results and thus have been neglected in the framework of linear theory. However, when properly considered, the velocities yield a nonperturbative contribution to the growth of structures which is then inherited by the majority of cosmic signals coming from redshifts above z ~ 10, and in certain cases may even propagate to various low-redshift observables such as the Baryon Acoustic Oscillations measured from the distribution of galaxies. At higher redshifts, the supersonic velocities have thus strong impact affecting the abundance of M ~ 106 M⊙ halos in an inhomogeneous way, hindering the formation of first stars, leaving traces in the redshifted 21-cm signal of neutral hydrogen, as well as having other important contributions at high redshifts all of which we review in this manuscript.

scholarly journals DAMA RESULTS: DARK MATTER IN THE GALACTIC HALO

2013 ◽  
Vol 53 (A) ◽  
pp. 589-594
Author(s):  
R. Bernabei ◽  
P. Belli ◽  
F. Cappella ◽  
V. Caracciolo ◽  
R. Cerulli ◽  
...  
Keyword(s):  
Dark Matter ◽  
Confidence Level ◽  
First Generation ◽  
Galactic Halo ◽  
Large Fraction ◽  
Future Perspectives ◽  
Independent Evidence ◽  
Annual Cycles ◽  
Model Independent ◽  
The Universe

Experimental efforts and theoretical developmens support that most of the Universe is Dark and a large fraction of it should be made of relic particles; many possibilities are open on their nature and interaction types. In particular, the DAMA/LIBRA experiment at Gran Sasso Laboratory (sensitive mass: ~250 kg) is mainly devoted to the investigation of Dark Matter (DM) particles in the Galactic halo by exploiting the model independent DM annual modulation signature with higly radiopure Na I(Tl) targets. DAMA/LIBRA is the succesor of the first generation DAMA/NaI (sensitive mass: ~100 kg); cumulatively the two experiments have released so far the results obtained by analyzing an exposure of 1.17 t yr, collected over 13 annual cycles. The data show a model independent evidence of the presence of DM particles in the galactic halo at 8.9σ confidence level (C.L.). Some of the already achieved results are shortly reminded, the last upgrade occurred at fall 2010 is mentioned and future perspectives are sumarized.

scholarly journals Dragging Force on Galaxies Due to Streaming Dark Matter

1990 ◽  
Vol 124 ◽  
pp. 645-649
Author(s):  
Tetsuya Hara ◽  
Shigeru Miyoshi
Keyword(s):  
Dark Matter ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Rest Frame ◽  
Background Radiation ◽  
Clusters Of Galaxies ◽  
Microwave Background ◽  
The Galaxy ◽  
Microwave Background Radiation ◽  
The Universe

It has been reported that galaxies in large regions (~102Mpc), including some clusters of galaxies, may be streaming coherently with velocities up to 600km/sec or more with respect to the rest frame determined by the microwave background radiation.) On the other hand, it is suggested that the dominant mass component of the universe is dark matter. Because we can only speculate the motion of dark matter from the galaxy motions, much attention should be paid to the correlation of velocities between the observed galaxies and cold dark matter. So we investigate whether such coherent large-scale streaming velocities are due to dark matter or only to baryonic objects which may be formed by piling up of gases due to some explosive events.

scholarly journals Diffuse Ultraviolet Background Radiation

1999 ◽  
Vol 171 ◽  
pp. 357-364
Author(s):  
Richard C. Henry
Keyword(s):  
Dark Matter ◽  
Surface Brightness ◽  
Background Radiation ◽  
Diffuse Radiation ◽  
Upper Limit ◽  
Nasa Mission ◽  
Low Surface Brightness ◽  
Diffuse Background ◽  
The Universe

AbstractDiffuse ultraviolet background radiation may contain important information concerning the dark matter of the universe. I briefly review new Voyager observations of the diffuse background, which give a very low upper limit on the background radiation shortward of Lyman α, and I review the capabilities for detection and characterization of diffuse radiation that will be provided by a proposed new NASA mission. Low-surface-brightness radiation remains largely an unexplored frontier, particularly in the ultraviolet.

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