scholarly journals Tidal Dwarf Galaxies and Missing Baryons

2010 ◽  
Vol 2010 ◽  
pp. 1-7 ◽  
Author(s):  
Frederic Bournaud
Keyword(s):  
Dark Matter ◽  
Spiral Galaxies ◽  
Dwarf Galaxies ◽  
High Redshift ◽  
Rotation Curves ◽  
Cosmological Problem ◽  
Flat Rotation Curves ◽  
Mass Size ◽  
Merger Rate ◽  
The Universe

Tidal dwarf galaxies form during the interaction, collision, or merger of massive spiral galaxies. They can resemble “normal” dwarf galaxies in terms of mass, size, and become dwarf satellites orbiting around their massive progenitor. They nevertheless keep some signatures from their origin, making them interesting targets for cosmological studies. In particular, they should be free from dark matter from a spheroidal halo. Flat rotation curves and high dynamical masses may then indicate the presence of an unseen component, and constrain the properties of the “missing baryons,” known to exist but not directly observed. The number of dwarf galaxies in the Universe is another cosmological problem for which it is important to ascertain if tidal dwarf galaxies formed frequently at high redshift, when the merger rate was high, and many of them survived until today. In this paper, “dark matter” is used to refer to the nonbaryonic matter, mostly located in large dark halos, that is, CDM in the standard paradigm, and “missing baryons” or “dark baryons” is used to refer to the baryons known to exist but hardly observed at redshift zero, and are a baryonic dark component that is additional to “dark matter”.

scholarly journals Do All Spiral Galaxies Have a Massive Dark Halo?

1999 ◽  
Vol 183 ◽  
pp. 157-157 ◽  
Author(s):  
M. Honma ◽  
Y. Sofue
Keyword(s):  
Dark Matter ◽  
Spiral Galaxies ◽  
The Other ◽  
Dark Halo ◽  
Rotation Curves ◽  
Other Hand ◽  
Flat Rotation Curves ◽  
The Masses ◽  
Scale Length

We have investigated the masses and extents of dark halos of spiral galaxies by two methods. First, we have reanalyzed HI outer rotation curves so far obtained considering the velocity uncertainties. We confirmed that many HI rotation curves indicate the existence of dark matter to some extent. However, we also found that only few rotation curves provide direct evidences for halos extended beyond 10 disk scale length. On the other hand, recent HI observations revealed that several galaxies have declining rotation curves that are approximated by Keplerian in the outermost regions. Considering the velocity uncertainties in the outer rotation curves, we found that these declining rotation curves are not rare compared to flat rotation curves. If these declining rotation curves indeed trace the mass truncation, these results indicate that some dark halos have moderate masses that are comparable or slightly larger than disk masses.

Dark matter particles and the flat rotation curves of spiral galaxies

1995 ◽  
Vol 234 (1) ◽  
pp. 69-83 ◽  
Author(s):  
H. Dehnen ◽  
B. Rose ◽  
K. Amer
Keyword(s):  
Dark Matter ◽  
Spiral Galaxies ◽  
Rotation Curves ◽  
Flat Rotation Curves

scholarly journals ROTATION CURVES OF SPIRAL GALAXIES AND LARGE-SCALE STRUCTURE OF THE UNIVERSE UNDER GENERALIZED EINSTEIN ACTION

1993 ◽  
Vol 02 (01) ◽  
pp. 123-133 ◽  
Author(s):  
M. KENMOKU ◽  
E. KITAJIMA ◽  
Y. OKAMOTO ◽  
K. SHIGEMOTO
Keyword(s):  
Large Scale ◽  
Spiral Galaxies ◽  
Microwave Background ◽  
Rotation Curves ◽  
Mass Distributions ◽  
Flat Rotation Curves ◽  
Number Counts ◽  
The Universe ◽  
Great Wall ◽  
Hilbert Action

We consider an addition of the term which is a square of the scalar curvature to the Einstein-Hilbert action. Under this generalized action, we attempt to explain (i) the flat rotation curves observed in spiral galaxies, which is usually attributed to the existence of dark matter, and (ii) the contradicting observations of the uniform cosmic microwave background and the nonuniform galaxy distributions against redshift. For the former, we attain the flatness of velocities, although the magnitudes remain about half that of the observations. For the latter, we obtain a solution with the oscillating Hubble parameter under uniform mass distributions. This solution leads to several peaks of galaxy number counts as a function of redshift with the first peak corresponding to the Great Wall.

scholarly journals MODIFIED GRAVITY AS A COMMON CAUSE FOR COSMIC ACCELERATION AND FLAT GALAXY ROTATION CURVES

2012 ◽  
Vol 21 (11) ◽  
pp. 1242002 ◽  
Author(s):  
PRITI MISHRA ◽  
TEJINDER P. SINGH
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Cosmic Acceleration ◽  
Accelerating Universe ◽  
Rotation Curves ◽  
Common Cause ◽  
Order Of Magnitude ◽  
Flat Rotation Curves ◽  
Acceleration Of The Universe ◽  
Galaxy Rotation Curves

Flat galaxy rotation curves and the accelerating Universe both imply the existence of a critical acceleration, which is of the same order of magnitude in both the cases, in spite of the galactic and cosmic length scales being vastly different. Yet, it is customary to explain galactic acceleration by invoking gravitationally bound dark matter, and cosmic acceleration by invoking a "repulsive" dark energy. Instead, might it not be the case that the flatness of rotation curves and the acceleration of the Universe have a common cause? In this essay we propose a modified theory of gravity. By applying the theory on galactic scales we demonstrate flat rotation curves without dark matter, and by applying it on cosmological scales we demonstrate cosmic acceleration without dark energy.

Can a tensorial analogue of gravitational force explain away the galactic rotation curves without dark matter?

2021 ◽  
Author(s):  
Ram Gopal Vishwakarma
Keyword(s):  
Dark Matter ◽  
Tensor Field ◽  
Gravitational Force ◽  
Direct Detection ◽  
Alternative Theory ◽  
Galactic Rotation ◽  
Rotation Curves ◽  
Modern Physics ◽  
Flat Rotation Curves ◽  
Relativistic Analogue

The dark matter problem is one of the most pressing problems in modern physics. As there is no well-established claim from a direct detection experiment supporting the existence of the illusive dark matter that has been postulated to explain the flat rotation curves of galaxies, and since the whole issue of an alternative theory of gravity remains controversial, it may be worth to reconsider the familiar ground of general relativity (GR) itself for a possible way out. It has recently been discovered that a skew-symmetric rank-three tensor field — the Lanczos tensor field — that generates the Weyl tensor differentially, provides a proper relativistic analogue of the Newtonian gravitational force. By taking account of its conformal invariance, the Lanczos tensor leads to a modified acceleration law which can explain, within the framework of GR itself, the flat rotation curves of galaxies without the need for any dark matter whatsoever.

scholarly journals NIKA: a mm camera for Sunyaev-Zel’dovich science in clusters of galaxies

2020 ◽  
Vol 228 ◽  
pp. 00016
Author(s):  
J.F. Macías-Pérez ◽  
R. Adam ◽  
P. Ade ◽  
P. André ◽  
A. Andrianasolo ◽  
...  
Keyword(s):  
Dark Matter ◽  
Angular Resolution ◽  
High Redshift ◽  
Radial Pressure ◽  
Pressure Profile ◽  
Field Of View ◽  
Dual Band ◽  
Clusters Of Galaxies ◽  
The Universe

Clusters of galaxies, the largest bound objects in the Universe, constitute a cosmological probe of choice, which is sensitive to both dark matter and dark energy. Within this framework, the Sunyaev-Zel’dovich (SZ) effect has opened a new window for the detection of clusters of galaxies and for the characterization of their physical properties such as mass, pressure and temperature. NIKA, a KID-based dual band camera installed at the IRAM 30-m telescope, was particularly well adapted in terms of frequency, angular resolution, field-of-view and sensitivity, for the mapping of the thermal and kinetic SZ effect in high-redshift clusters. In this paper, we present the NIKA cluster sample and a review of the main results obtained via the measurement of the SZ effect on those clusters: reconstruction of the cluster radial pressure profile, mass, temperature and velocity.

scholarly journals Rotation Curves in the Outer Parts of Galaxies from HI Observations

1978 ◽  
Vol 77 ◽  
pp. 23-31 ◽  
Author(s):  
Edwin E. Salpeter
Keyword(s):  
Spiral Galaxies ◽  
Rotation Curves ◽  
Flat Rotation Curves ◽  
Arecibo Observatory

21cm observations at the Arecibo Observatory for 9 edge-on spiral galaxies are described. Flat rotation curves are found in most cases.

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