scholarly journals Gas Density Profile in Dark Matter Halo in Chameleon Cosmology

2012 ◽  
Vol 86 (10) ◽  
Author(s):  
Ayumu Terukina ◽  
Kazuhiro Yamamoto
Keyword(s):  
Dark Matter ◽  
Density Profile ◽  
Dark Matter Halo ◽  
Gas Density

X‐Ray Gas Density Profile of Clusters of Galaxies from the Universal Dark Matter Halo

1998 ◽  
Vol 497 (2) ◽  
pp. 555-558 ◽  
Author(s):  
Nobuyoshi Makino ◽  
Shin Sasaki ◽  
Yasushi Suto
Keyword(s):  
Dark Matter ◽  
Density Profile ◽  
Dark Matter Halo ◽  
Clusters Of Galaxies ◽  
Gas Density ◽  
X Ray

scholarly journals The Dark Matter Halo Density Profile, Spiral Arm Morphology, and Supermassive Black Hole Mass of M33

2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
Marc S. Seigar
Keyword(s):  
Black Hole ◽  
Dark Matter ◽  
Density Profile ◽  
Pitch Angle ◽  
Rotation Curve ◽  
Dark Matter Halo ◽  
Black Hole Mass ◽  
Supermassive Black Hole ◽  
Virial Mass ◽  
Spiral Arm

We investigate the dark matter halo density profile of M33. We find that the HI rotation curve of M33 is best described by an NFW dark matter halo density profile model, with a halo concentration of and a virial mass of . We go on to use the NFW concentration of M33, along with the values derived for other galaxies (as found in the literature), to show that correlates with both spiral arm pitch angle and supermassive black hole mass.

scholarly journals Globular cluster ejection, infall, and the host dark matter halo of the Pegasus dwarf galaxy

2020 ◽  
Vol 492 (4) ◽  
pp. 5102-5120
Author(s):  
Ryan Leaman ◽  
Tomás Ruiz-Lara ◽  
Andrew A Cole ◽  
Michael A Beasley ◽  
Alina Boecker ◽  
...  
Keyword(s):  
Dark Matter ◽  
Relaxation Time ◽  
Density Profile ◽  
Globular Cluster ◽  
Dwarf Galaxy ◽  
Orbital Evolution ◽  
Dark Matter Halo ◽  
Host Galaxy ◽  
Structural Constraints ◽  
The Galaxy

ABSTRACT Recent photometric observations revealed a massive, extended (MGC ≳ 105 M⊙; Rh ∼ 14 pc) globular cluster (GC) in the central region (D3D ≲ 100 pc) of the low-mass (M* ∼ 5 × 106 M⊙) dwarf irregular galaxy Pegasus. This massive GC offers a unique opportunity to study star cluster inspiral as a mechanism for building up nuclear star clusters, and the dark matter (DM) density profile of the host galaxy. Here, we present spectroscopic observations indicating that the GC has a systemic velocity of ΔV = 3 ± 8 km s−1 relative to the host galaxy, and an old, metal-poor stellar population. We run a suite of orbital evolution models for a variety of host potentials (cored to cusped) and find that the GC’s observed tidal radius (which is ∼3 times larger than the local Jacobi radius), relaxation time, and relative velocity are consistent with it surviving inspiral from a distance of Dgal ≳ 700 pc (up to the maximum tested value of Dgal = 2000 pc). In successful trials, the GC arrives to the galaxy centre only within the last ∼1.4 ± 1 Gyr. Orbits that arrive in the centre and survive are possible in DM haloes of nearly all shapes, however to satisfy the GC’s structural constraints a galaxy DM halo with mass MDM ≃ 6 ± 2 × 109 M⊙, concentration c ≃ 13.7 ± 0.6, and an inner slope to the DM density profile of −0.9 ≤ γ ≤ −0.5 is preferred. The gas densities necessary for its creation and survival suggest the GC could have formed initially near the dwarf’s centre, but then was quickly relocated to the outskirts where the weaker tidal field permitted an increased size and relaxation time – with the latter preserving the former during subsequent orbital decay.

scholarly journals Could galactic magnetic fields be generated by charged ultra-light boson dark matter?

2019 ◽  
Vol 79 (10) ◽  
Author(s):  
Maribel Hernández ◽  
Ana A. Avilez ◽  
Tonatiuh Matos
Keyword(s):  
Dark Matter ◽  
Scalar Field ◽  
Magnetic Fields ◽  
Density Profile ◽  
Dark Matter Halo ◽  
Error Estimator ◽  
Rotation Curves ◽  
Complex Scalar ◽  
Virtual Photons ◽  
Klein Gordon

Abstract We study the possibility that large-scale magnetic fields observed in galaxies could be produced by a dark matter halo made of charged ultra-light bosons, that arise as excitations of a complex scalar field described by the Klein–Gordon equation with local U(1) symmetry which introduces electromagnetic fields that minimally couple to the complex scalar current and act as dark virtual photons. These virtual photons have an unknown coupling constant with real virtual photons. We constrain the final interaction using the observed magnetic fields in galaxies. We use classical solutions of the Klein–Gordon–Maxwell system to describe the density profile of dark matter and magnetic fields in galaxies. We consider two cases assuming spherical and dipolar spatial symmetries. For the LSB spherical galaxy F563-V2, we test the sensitivity of the predicted rotation curves in the charged Scalar Field Dark Matter (cSFDM) model to variations of the electromagnetic coupling and using the Fisher matrix error estimator, we set a constraint over that coupling by requiring that theoretical rotation curves lay inside the $$1\sigma $$1σ confidence region of observational data. We find that cSFDM haloes generate magnetic fields of the order of $$\mu G$$μG and reproduce the observed rotation curves of F563-V2 if the ultra-light boson has a charge $$\sim <10^{-13}e$$∼<10-13e for the monopole-like density profile and $$\sim <10^{-14}e$$∼<10-14e for the dipole-like one.

scholarly journals Explaining the density profile of self-gravitating systems by statistical mechanics

2015 ◽  
Vol 11 (A29B) ◽  
pp. 743-743
Author(s):  
Dong-Biao Kang
Keyword(s):  
Dark Matter ◽  
Angular Momentum ◽  
Radial Distribution ◽  
Density Profile ◽  
Large Scale ◽  
Rotation Curve ◽  
Dark Matter Halo ◽  
Stellar Disk ◽  
Exponential Law ◽  
Flat Rotation Curve

AbstractA self-gravitating system usually shows a quasi-universal density profile, such as the NFW profile of a simulated dark matter halo, the flat rotation curve of a spiral galaxy, the Sérsic profile of an elliptical galaxy, the King profile of a globular cluster and the exponential law of the stellar disk. It will be interesting if all of the above can be obtained from first principles. Based on the original work of White & Narayan (1987), we propose that if the self-bounded system is divided into infinite infinitesimal subsystems, the entropy of each subsystem can be maximized, but the whole system's gravity may just play the role of the wall, which may not increase the whole system's entropy St, and finally St may be the minimum among all of the locally maximized entropies (He & Kang 2010). For spherical systems with isotropic velocity dispersion, the form of the equation of state will be a hybrid of isothermal and adiabatic (Kang & He 2011). Hence this density profile can be approximated by a truncated isothermal sphere, which means that the total mass must be finite and our results can be consistent with observations (Kang & He 2011b). Our method requires that the mass and energy should be conserved, so we only compare our results with simulations of mild relaxation (i.e. the virial ratio is close to -1) of dissipationless collapse (Kang 2014), and the fitting also is well. The capacity can be calculated and is found not to be always negative as in previous works, and combining with calculations of the second order variation of the entropy, we find that the thermodynamical stability still can be true (Kang 2012) if the temperature tends to be zero. However, the cusp in the center of dark matter halos can not be explained, and more works will continue.The above work can be generalized to study the radial distribution of the disk (Kang 2015). The energy constraint automatically disappears in our variation, because angular momentum is much more important than energy for the disk-shape system. To simplify this issue, a toy model is taken: 2D gravity is adopted, then at large scale it will be consistent with a flat rotation curve; the bulge and the stellar disk are studied together. Then with constraints of mass and angular momentum, the calculated surface density can be consistent with the truncated, up-bended or standard exponential law. Therefore the radial distribution of the stellar disk may be determined by both the random and orbital motions of stars. In our fittings the central gravity is set to be nonzero to include the effect of asymmetric components.

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 Transonic galactic outflows in a dark matter halo with a central black hole

2015 ◽  
Vol 11 (A29B) ◽  
pp. 741-741
Author(s):  
Asuka Igarashi ◽  
Masao Mori ◽  
Shin-ya Nitta
Keyword(s):  
Black Hole ◽  
Dark Matter ◽  
Density Distribution ◽  
Mass Flux ◽  
Dark Matter Halo ◽  
Polytropic Model ◽  
Gas Density ◽  
Topological Features ◽  
Galactic Outflows ◽  
Distant Region

AbstractWe study fundamental properties of transonic galactic outflows in the gravitational potential of a cold dark matter halo (DMH) with a central super-massive black hole (SMBH) assuming an isothermal, steady and spherically symmetric state. Transonic solutions of galactic outflows are classified according to their topological features. As result, we find two types of transonic solutions distinguished by a magnitude relationship between the gravity of DMH and that of SMBH. The loci of transonic points for two types are different; one transonic point is formed at a central region (< 0.01kpc) and another is at a very distant region (> 100kpc). Also, mass fluxes and outflow velocities are different for two solutions. Thus, these solutions may differently influence the evolution of galaxies and the release of metals into the intergalactic space.Furthermore, we apply our model to the Sombrero galaxy. In this galaxy, the wide-spread hot gas is detected as the trace of galactic outflows while the star-formation rate is low, and the observed gas density distribution is similar to the hydrostatic state (Li et al. 2011). To solve this discrepancy, we propose a solution that this galaxy has a slowly accelerating outflow; the transonic point forms in a very distant region (~ 120 kpc) and the wide subsonic region spreads across the stellar distribution. Thus, the gas density distribution in the observed region is similar to the hydrostatic state. Such slowly accelerating outflows are different from high-velocity outflows conventionally studied (Igarashi et al. 2014).However, this isothermal model requires an unrealistically large mass flux. Then, we apply the polytropic model to this galaxy incorporating mass flux supplied by stellar components. We find that it can reproduce the observed gas density and the temperature distributions with the realistic mass flux. Thus, our polytropic model successfully demonstrates the existence of the slowly accelerating outflow in the Sombrero galaxy (Igarashi et al. 2015).

scholarly journals A new class of galaxy models with a central BH – I. The spherical case

2019 ◽  
Vol 490 (2) ◽  
pp. 2656-2667 ◽  
Author(s):  
Luca Ciotti ◽  
Antonio Mancino ◽  
Silvia Pellegrini
Keyword(s):  
Dark Matter ◽  
Density Profile ◽  
Mass Density ◽  
Dark Matter Halo ◽  
New Class ◽  
Stellar Component ◽  
Starting Point ◽  
The Galaxy ◽  
Radial Orbit ◽  
Analytical Expressions

ABSTRACTThe dynamical properties of spherically symmetric galaxy models, where a Jaffe stellar density profile is embedded in a total mass density decreasing as r−3 at large radii, are presented. The orbital structure of the stellar component is described by the Osipkov–Merritt anisotropy; the dark matter halo is isotropic, and a black hole is added at the centre of the galaxy. First, the conditions for a nowhere negative and monotonically decreasing dark matter halo density profile are derived; this profile can be made asymptotically coincident with an NFW profile at the centre and large radii. Then, the minimum value of the anisotropy radius for phase-space consistency is derived as a function of the galaxy parameters. The Jeans equations for the stellar component are solved analytically; the projected velocity dispersion at the centre and large radii is also obtained, for generic values of the anisotropy radius. Finally, analytical expressions for the terms entering the Virial Theorem are derived, and the fiducial anisotropy limit required to prevent the onset of Radial Orbit Instability is determined as a function of the galaxy parameters. The presented models, built following an approach already adopted in our previous works, can be a useful starting point for a more advanced modelling of the dynamics of elliptical galaxies, and can be easily implemented in numerical simulations requiring a realistic dynamical model of a galaxy.

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