scholarly journals Ultra Light Axionic Dark Matter: Galactic Halos and Implications for Observations with Pulsar Timing Arrays

Galaxies ◽  
2018 ◽  
Vol 6 (1) ◽  
pp. 10 ◽  
Author(s):  
Ivan De Martino ◽  
Tom Broadhurst ◽  
S.-H. Tye ◽  
Tzihong Chiueh ◽  
Hsi-Yu Schive ◽  
...  
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Dwarf Galaxy ◽  
Massive Particle ◽  
Dark Matter Halo ◽  
Galactic Halos ◽  
Dark Matter Halos ◽  
Pulsar Timing ◽  
Pulsar Timing Array ◽  
Pulse Arrival

The cold dark matter (CDM) paradigm successfully explains the cosmic structure over an enormous span of redshifts. However, it fails when probing the innermost regions of dark matter halos and the properties of the Milky Way’s dwarf galaxy satellites. Moreover, the lack of experimental detection of Weakly Interacting Massive Particle (WIMP) favors alternative candidates such as light axionic dark matter that naturally arise in string theory. Cosmological N-body simulations have shown that axionic dark matter forms a solitonic core of size of ≃150 pc in the innermost region of the galactic halos. The oscillating scalar field associated to the axionic dark matter halo produces an oscillating gravitational potential that induces a time dilation of the pulse arrival time of ≃400 ns/(m B /10 − 22 eV) for pulsar within such a solitonic core. Over the whole galaxy, the averaged predicted signal may be detectable with current and forthcoming pulsar timing array telescopes.

scholarly journals Structure of Dark Matter Halo

1999 ◽  
Vol 183 ◽  
pp. 155-155
Author(s):  
Toshiyuki Fukushige ◽  
Junichiro Makino
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Temperature Inversion ◽  
Dark Matter Halo ◽  
Temperature Structure ◽  
Galactic Halos ◽  
Dark Matter Halos ◽  
Density Profiles ◽  
Order Of Magnitude ◽  
Special Purpose Computer

We performed N-body simulation on special-purpose computer, GRAPE-4, to investigate the structure of dark matter halos (Fukushige, T. and Makino, J. 1997, ApJL, 477, L9). Universal profile proposed by Navarro, Frenk, and White (1996, ApJ, 462, 563), which has cusp with density profiles ρ ∝r−1in density profile, cannot be reproduced in the standard Cold Dark Matter (CDM) picture of hierarchical clustering. Previous claims to the contrary were based on simulations with relatively few particles, and substantial softening. We performed simulations with particle numbers an order of magnitude higher, and essentially no softening, and found that typical central density profiles are clearly steeper than ρ ∝r−1, as shown in Figure 1. In addition, we confirm the presence of a temperature inversion in the inner 5 kpc of massive galactic halos, and give a natural explanation for formation of the temperature structure.

scholarly journals Tidal Tails and the Shape of the Dark Matter Halo

2005 ◽  
Vol 22 (3) ◽  
pp. 190-194 ◽  
Author(s):  
Geraint F. Lewis ◽  
Rodrigo A. Ibata
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Milky Way ◽  
Dwarf Galaxy ◽  
Observational Evidence ◽  
Dark Matter Halo ◽  
Dark Matter Halos ◽  
Fundamental Understanding ◽  
Tidal Tails ◽  
Precise Interpretation

AbstractCold dark matter cosmologies successfully accounts for the distribution of matter on large scales. On smaller scales, these cosmological models predict that galaxies like our own Milky Way should be enveloped in massive dark matter halos. Furthermore, these halos should be significantly flattened or even triaxial. Recent observational evidence, drawn from the demise of the Sagittarius dwarf galaxy as it is cannibalized by our own, indicates that the potential of the Milky Way must be close to spherical. While the precise interpretation of the observational evidence is under debate, an apparently spherical halo may signify a pronounced failing of dark matter models, and may even indicate a failure in our fundamental understanding of gravity.

scholarly journals Numerical Simulation of the Dwarf Companions of Giant Galaxies

2007 ◽  
Vol 3 (S244) ◽  
pp. 226-230
Author(s):  
A. H. Nelson ◽  
P. R. Williams
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Initial Conditions ◽  
Dark Matter Halo ◽  
Initial Population ◽  
Dark Matter Halos ◽  
Disc Galaxy ◽  
Standard Spectrum ◽  
The Galaxy ◽  
Secondary Population

AbstractWe report simulations of the formation of a giant disc galaxy from cosmological initial conditions. Two sets of initial conditions are used, initially smooth density for both gas and stars, representing the Warm dark Matter scenario, and an initially fluctuating density representing the standard spectrum for the Cold dark Matter scenario. For the WDM initial conditions, the galaxy has a population of long lived dwarf satellites at z = 0, with orbits close to a plane coincident with that of the giant galaxy disc. The detailed properties of these dwarfs mimic closely the observed properties of Local Group dwarfs with respect to mass, and kinematics. However they do not have individual dark matter halos, but orbit in the nearly spherical dark matter halo of the giant galaxy. The reason for this is that the initial population of dwarf dark matter haloes, which form during the initial collapse phase, all merge into the halo of the giant galaxy within a few to several Gyears, while the long lived dwarfs form as a secondary population by gravitational collapse of high angular momentum gas in the outer reaches of the giants proto-galactic disc. Due to their late formation and their more distant orbits, they survive until the present epoch as individual dwarf galaxies at radii 20-50kpc from the giants centre. For CDM initial conditions there are many more dwarf satellites at z = 0, some of which form early on as gas condensations in DM sub-halos, and survive with these individual DM halos till z = 0 due to their being sufficiently well bound to avoid merging with the main galaxy. However even in this case some second generation satellites form as initially gas only objects, just as for the smooth initial conditions of WDM.

scholarly journals Inner Structure of Dark Matter Halos

2004 ◽  
Vol 220 ◽  
pp. 99-100 ◽  
Author(s):  
Toshiyuki Fukushige ◽  
Atsushi Kawai ◽  
Junichiro Makino
Keyword(s):  
Dark Matter ◽  
Density Profile ◽  
Cold Dark Matter ◽  
Dark Matter Halo ◽  
Dark Matter Halos ◽  
Cluster Systems

We investigate the structure of the dark matter halo formed in the cold dark matter scenarios by N-body simulations with parallel treecode on GRAPE cluster systems (Fukushige, Kawai, Makino 2003). We simulated 8 halos with the mass of 4.4 × 1014M⊙ to 1.6 × 1015M⊙ in the SCDM and LCDM model using up to 30 million particles. With the resolution of our simulations, the density profile is reliable down to 0.2 percent of the virial radius. Our results show that the slope of inner cusp within 1 percent virial radius is shallower than −1.5, and the radius where the shallowing starts exhibits run-to-run variation, which means the innermost profile is not universal.

The Future of Dwarf Galaxy Research: What Simulations will Predict?

2018 ◽  
Vol 14 (S344) ◽  
pp. 17-26
Author(s):  
Laura V. Sales
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
Matter Content ◽  
Dark Matter Halos ◽  
Matter Distribution ◽  
The Future ◽  
Dark Matter Distribution

AbstractWe present a summary of the predictions from numerical simulations to our understanding of dwarf galaxies. It centers the discussion around the Λ Cold Dark Matter scenario (ΛCDM) but discusses also implications for alternative dark matter models. Four key predictions are identified: the abundance of dwarf galaxies, their dark matter content, their relation with environment and the existence of dwarf satellites orbiting dwarf field galaxies. We discuss tensions with observations and identify the most exciting predictions expected from simulations in the future, including i) the existence of “dark galaxies” (dark matter halos without stars), ii) the ability to resolve the structure (size, morphology, dark matter distribution) in dwarfs and iii) the number of ultra-faint satellites around dwarf galaxies. All of these predictions shall inform future observations, not only the faintest galaxies to be discovered within the Local Volume but also distant dwarfs driving galaxy formation in the early universe.

scholarly journals NIHAO – XXV. Convergence in the cusp-core transformation of cold dark matter haloes at high star formation thresholds

2020 ◽  
Vol 499 (2) ◽  
pp. 2648-2661
Author(s):  
Aaron A Dutton ◽  
Tobias Buck ◽  
Andrea V Macciò ◽  
Keri L Dixon ◽  
Marvin Blank ◽  
...  
Keyword(s):  
Dark Matter ◽  
Star Formation ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
Good Description ◽  
Good Match ◽  
Virial Mass ◽  
Density Threshold

ABSTRACT We use cosmological hydrodynamical galaxy formation simulations from the NIHAO project to investigate the response of cold dark matter (CDM) haloes to baryonic processes. Previous work has shown that the halo response is primarily a function of the ratio between galaxy stellar mass and total virial mass, and the density threshold above which gas is eligible to form stars, n[cm−3]. At low n all simulations in the literature agree that dwarf galaxy haloes are cuspy, but at high n ≳ 100 there is no consensus. We trace halo contraction in dwarf galaxies with n ≳ 100 reported in some previous simulations to insufficient spatial resolution. Provided the adopted star formation threshold is appropriate for the resolution of the simulation, we show that the halo response is remarkably stable for n ≳ 5, up to the highest star formation threshold that we test, n = 500. This free parameter can be calibrated using the observed clustering of young stars. Simulations with low thresholds n ≤ 1 predict clustering that is too weak, while simulations with high star formation thresholds n ≳ 5, are consistent with the observed clustering. Finally, we test the CDM predictions against the circular velocities of nearby dwarf galaxies. Low thresholds predict velocities that are too high, while simulations with n ∼ 10 provide a good match to the observations. We thus conclude that the CDM model provides a good description of the structure of galaxies on kpc scales provided the effects of baryons are properly captured.

scholarly journals Probing the structure of the cold dark matter halo using ancient mica

1998 ◽  
Vol 59 (2) ◽  
Author(s):  
Edward A. Baltz ◽  
Andrew J. Westphal ◽  
Daniel P. Snowden-Ifft
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Dark Matter Halo

scholarly journals Recoiling black holes in static and evolving dark matter halo potential

2015 ◽  
pp. 17-28 ◽  
Author(s):  
M. Smole
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Dark Matter ◽  
Critical Velocity ◽  
Complete Removal ◽  
Matter Density ◽  
Dark Matter Halo ◽  
Dark Matter Halos ◽  
Critical Amplitude ◽  
Density Distributions

We follow trajectories of kicked black holes in static and evolving dark matter halo potential. We explore both NFW and Einasto dark matter density distributions. Considered dark matter halos represent hosts of massive spiral and elliptical field galaxies. We study critical amplitude of kick velocity necessary for complete black hole ejection at various redshifts and find that ~40% lower kick velocities can remove black holes from their host haloes at z = 7 compared to z = 1. The greatest difference between static and evolving potential occurs near the critical velocity for black hole ejection and at high redshifts. When NFW and Einasto density distributions are compared ~30% higher kick velocities are needed for complete removal of BHs from dark matter halo described by NFW profile.

scholarly journals Crater 2: An Extremely Cold Dark Matter Halo

2017 ◽  
Vol 839 (1) ◽  
pp. 20 ◽  
Author(s):  
Nelson Caldwell ◽  
Matthew G. Walker ◽  
Mario Mateo ◽  
Edward W. Olszewski ◽  
Sergey Koposov ◽  
...  
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Dark Matter Halo
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