Revisiting the angular momentum growth of protostructures evolved from non-Gaussian initial conditions

Pease and Shapley (1917) first remarked on the apparent flattening of several Galactic globular clusters, a view that has been confirmed by many subsequent studies. Tidal stresses, internal rotation, and velocity anisotropies can cause deviations from sphericity in stellar systems. In general, we might expect globular clusters to have some angular momentum at the time of formation and, if they collapsed from flattened initial conditions, to have anisotropic pressure support. Since the velocity distributions within the clusters can be altered by a variety of internal and external processes, their shapes are expected to evolve. In this article, we review the methods for measuring ellipticities and the results that have emerged from such studies. Our main purpose, however, is to discuss the processes that determine the shapes of globular clusters and the ways in which they change with time.

Download Full-text

Scale dependence of halo bispectrum from non-Gaussian initial conditions in cosmological N-body simulations

Journal of Cosmology and Astroparticle Physics ◽

10.1088/1475-7516/2010/07/002 ◽

2010 ◽

Vol 2010 (07) ◽

pp. 002-002 ◽

Cited By ~ 33

Author(s):

Takahiro Nishimichi ◽

Atsushi Taruya ◽

Kazuya Koyama ◽

Cristiano Sabiu

Keyword(s):

Initial Conditions ◽

Scale Dependence ◽

Non Gaussian

Download Full-text

Results on the filtering problem for linear systems with non-Gaussian initial conditions

10.1109/cdc.1982.268427 ◽

1982 ◽

Cited By ~ 7

Author(s):

Armand Makowski

Keyword(s):

Linear Systems ◽

Initial Conditions ◽

Non Gaussian ◽

Filtering Problem

Download Full-text

SEARCHING FOR QUANTUM GRAVITY EFFECTS IN COSMOLOGICAL DATA

International Journal of Modern Physics D ◽

10.1142/s0218271894000411 ◽

1994 ◽

Vol 03 (01) ◽

pp. 257-263 ◽

Cited By ~ 3

Author(s):

D.S. SALOPEK

Keyword(s):

Quantum Gravity ◽

Initial Conditions ◽

Microwave Background ◽

Nonlinear Quantum ◽

Gravity Effects ◽

Cosmological Data ◽

Clustering Data ◽

Non Gaussian ◽

Excess Power ◽

The Universe

If the inflationary scenario describes our Universe, then it is possible that quantum gravity phenomena could be observed in anisotropy experiments of the microwave background as well as in galaxy clustering data. Primordial gravitational radiation arising from inflation is a consequence of quantum gravity. Moreover, the wavefunction of the Universe is currently being measured by the COBE satellite. A non-Gaussian distribution could be a signature of nonlinear quantum gravity. In fact, the excess power power seen in the APM survey of galaxies can arise from non-Gaussian initial conditions generated during inflation.

Download Full-text

The surprisingly small impact of magnetic fields on the inner accretion flow of Sagittarius A* fueled by stellar winds

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz3605 ◽

2019 ◽

Vol 492 (3) ◽

pp. 3272-3293 ◽

Cited By ~ 3

Author(s):

S M Ressler ◽

E Quataert ◽

J M Stone

Keyword(s):

Angular Momentum ◽

Magnetic Fields ◽

Event Horizon ◽

Initial Conditions ◽

Rotational Instability ◽

Stellar Winds ◽

Accretion Flow ◽

Sagittarius A ◽

Mhd Simulations ◽

Sgr A

ABSTRACT We study the flow structure in 3D magnetohydrodynamic (MHD) simulations of accretion on to Sagittarius A* via the magnetized winds of the orbiting Wolf–Rayet stars. These simulations cover over 3 orders of magnitude in radius to reach ≈300 gravitational radii, with only one poorly constrained parameter (the magnetic field in the stellar winds). Even for winds with relatively weak magnetic fields (e.g. plasma β ∼ 106), flux freezing/compression in the inflowing gas amplifies the field to β ∼ few well before it reaches the event horizon. Overall, the dynamics, accretion rate, and spherically averaged flow profiles (e.g. density, velocity) in our MHD simulations are remarkably similar to analogous hydrodynamic simulations. We attribute this to the broad distribution of angular momentum provided by the stellar winds, which sources accretion even absent much angular momentum transport. We find that the magneto-rotational instability is not important because of (i) strong magnetic fields that are amplified by flux freezing/compression, and (ii) the rapid inflow/outflow times of the gas and inefficient radiative cooling preclude circularization. The primary effect of magnetic fields is that they drive a polar outflow that is absent in hydrodynamics. The dynamical state of the accretion flow found in our simulations is unlike the rotationally supported tori used as initial conditions in horizon scale simulations, which could have implications for models being used to interpret Event Horizon Telescope and GRAVITY observations of Sgr A*.

Download Full-text