scholarly journals The shape of the dark matter halo revealed from a hypervelocity star

2019 ◽  
Vol 14 (S353) ◽  
pp. 96-100
Author(s):  
Kohei Hattori ◽  
Monica Valluri
Keyword(s):  
Dark Matter ◽  
Posterior Distribution ◽  
Galactic Center ◽  
Dark Matter Halo ◽  
Velocity Data ◽  
Broad Distribution ◽  
Giant Star ◽  
Circular Velocity ◽  
Galactic Dark Matter ◽  
Radial Orbit

AbstractA recently discovered young, high-velocity giant star J01020100-7122208 is a good candidate of hypervelocity star ejected from the Galactic center, although it has a bound orbit. If we assume that this star was ejected from the Galactic center, it can be used to constrain the Galactic potential, because the deviation of its orbit from a purely radial orbit informs us of the torque that this star has received. Based on this assumption, we estimate the flattening of the Galactic dark matter halo by using the Gaia DR2 data and the circular velocity data. Our Bayesian analysis shows that the orbit of J01020100-7122208 favors a prolate halo within ~ 10 kpc from the Galactic center. The posterior distribution of the density flattening q shows a broad distribution at q ≳ 1 and peaks at q ≃ 1.5. Also, 98.5% of the posterior distribution is located at q > 1, highly disfavoring an oblate halo.

scholarly journals On measuring the Galactic dark matter halo with hypervelocity stars

2019 ◽  
Vol 487 (3) ◽  
pp. 4025-4036 ◽  
Author(s):  
O Contigiani ◽  
E M Rossi ◽  
T Marchetti
Keyword(s):  
Dark Matter ◽  
Dark Matter Halo ◽  
Galactic Dark Matter

The Role of the Radial Orbit Instability in Dark Matter Halo Formation and Structure

2006 ◽  
Vol 2 (S235) ◽  
pp. 124-124
Author(s):  
J. M. Meyer ◽  
J. J. Dalcanton ◽  
T. R. Quinn ◽  
L. L. R. Williams ◽  
E. I. Barnes ◽  
...  
Keyword(s):  
Dark Matter ◽  
Density Profile ◽  
Dark Matter Halo ◽  
Dark Matter Halos ◽  
Radial Orbit ◽  
Profile Changes ◽  
Analytic Models ◽  
The Universe ◽  
Scale Length

AbstractFor nearly a decade, N-body simulations have revealed a nearly universal dark matter density profile. This density profile appears to be robust to changes in the overall density of the universe and the underlying power spectrum. Despite its universality, however, the physical origin of this profile has not yet been well understood. Semi-analytic models have suggested that scale lengths in dark matter halos may be determined by the onset of the radial orbit instability. We have tested this theory using N-body simulations of collapsing dark matter halos. The resulting halo structures are prolate in shape, due to the mild aspect of the instability. We find that the radial orbit instability sets a scale length at which the velocity dispersion changes rapidly from isotropic to radially anisotropic. Preliminary analysis suggests that this scale length is proportional to the radius at which the density profile changes shape, as is the case in the semi-analytic models; however, the coefficient of proportionality is different by a factor of ~2. We conclude that the radial orbit instability may be a key physical mechanism responsible for the nearly universal profiles of simulated dark matter halos.

scholarly journals Bosonic gas as a galactic dark matter halo

2010 ◽  
Vol 82 (12) ◽  
Author(s):  
L. Arturo Ureña-López ◽  
Argelia Bernal
Keyword(s):  
Dark Matter ◽  
Dark Matter Halo ◽  
Galactic Dark Matter

scholarly journals WEIGHING THE GALACTIC DARK MATTER HALO: A LOWER MASS LIMIT FROM THE FASTEST HALO STAR KNOWN

2010 ◽  
Vol 718 (1) ◽  
pp. 37-42 ◽  
Author(s):  
Norbert Przybilla ◽  
Alfred Tillich ◽  
Ulrich Heber ◽  
Ralf-Dieter Scholz
Keyword(s):  
Dark Matter ◽  
Dark Matter Halo ◽  
Mass Limit ◽  
Lower Mass ◽  
Halo Star ◽  
Galactic Dark Matter ◽  
Lower Mass Limit

scholarly journals On the Shape of the Galactic Dark Matter Halo

2004 ◽  
Vol 21 (2) ◽  
pp. 212-215 ◽  
Author(s):  
Amina Helmi
Keyword(s):  
Dark Matter ◽  
Numerical Simulations ◽  
Cold Dark Matter ◽  
Milky Way ◽  
Dark Matter Halo ◽  
Dark Halo ◽  
Galactic Dark Matter ◽  
Galactic Potentials ◽  
Strong Contrast

AbstractThe confined nature of the debris from the Sagittarius dwarf to a narrow trail on the sky has recently prompted the suggestion that the dark matter halo of our Galaxy should be nearly spherical (Ibata et al. 2001; Majewski et al. 2003). This would seem to be in strong contrast with predictions from cold dark matter (CDM) simulations, where dark halos are found to have typical density axis ratios of 0.6 to 0.8. Here I present numerical simulations of the evolution of a system like the Sagittarius dSph in a set of Galactic potentials with varying degrees of flattening. These simulations show that the Sagittarius streams discovered so far are too young dynamically to be sensitive to the shape of the dark halo of the Milky Way. The data presently available are entirely consistent with a Galactic dark matter halo that could either be oblate or prolate, with density axis ratios c/a that range from 0.6 to 1.6 within the region of the halo probed by the orbit of the Sagittarius dwarf.

Rotation Curve and Dark Matter Halo profile in Finsler Geometry

2020 ◽  
Author(s):  
Nupur Paul ◽  
Farook Rahaman ◽  
Nasarul Islam ◽  
S.S. De
Keyword(s):  
Dark Matter ◽  
Rotational Velocity ◽  
Finsler Geometry ◽  
Outer Region ◽  
Recent Time ◽  
Dark Matter Halo ◽  
Dark Matter Halos ◽  
Radial Profiles ◽  
Galactic Dark Matter ◽  
Specific Equation

Galactic dark matter is an active area of research in recent time. Several researchers proposed several descriptions of radial profiles of dark matter halos by using N-body simulations. Among them, Navarro, Frenk and White (NFW) dark matter profile provides the most accurate description of dark matter halos. It is believed that dark matter is smooth and distributed uniformly throughout space. Using Finslerian geometrical background and a specific equation of state, we propose a new way to estimate the rotational velocity of galaxies based on the NFW dark matter profile. On small scales the first few distances (about 30 kpc) the velocity increases whereas in the outer region of the galaxies, the rotational velocity is found to be more or less constant which supports observed rotational velocities.

scholarly journals Searching For Dark Matter With Gravitational Microlensing: A Report From The MACHO Collaboration

1996 ◽  
Vol 173 ◽  
pp. 209-214
Author(s):  
C.W. Stubbs ◽  
C. Alcock ◽  
R.A. Allsman ◽  
D. Alves ◽  
T.S. Axelrod ◽  
...  
Keyword(s):  
Dark Matter ◽  
Optical Depth ◽  
Galactic Center ◽  
Mass Range ◽  
Dark Matter Halo ◽  
Important Constraint ◽  
Gravitational Microlensing ◽  
The Galaxy ◽  
Straightforward Interpretation

Gravitational microlensing is the most straightforward interpretation of the stellar brightenings that have been observed by our team and other experiments. These data have provided some of the most stringent limits to date on the nature of the Galaxy's dark matter halo. The number of events seen towards the LMC indicate that our Galaxy is not surrounded by a “standard” halo of MACHOs in the mass range of 10–6 to 0.3 solar masses. The observed optical depth towards the Galactic Center is an important constraint on the distribution of mass in the plane of the Galaxy.

scholarly journals Neutrino propagation in the Galactic dark matter halo

2016 ◽  
Vol 94 (12) ◽  
Author(s):  
P. F. de Salas ◽  
R. A. Lineros ◽  
M. Tórtola
Keyword(s):  
Dark Matter ◽  
Dark Matter Halo ◽  
Galactic Dark Matter ◽  
Neutrino Propagation
Sign in / Sign up

Export Citation Format

Share Document