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We demonstrate that in N-body simulations of isolated disc galaxies there is numerical vertical heating which slowly increases the vertical velocity dispersion and the disc thickness. Even for models with over a million particles in a disc,…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-16 S. A. Rodionov , N. Ya. Sotnikova

Cosmological simulations of disc galaxy formation, when compared to the observed Tully-Fisher relation, suggest a low Mass-to-Light (M/L) ratio for the stellar component in spirals. We show that a number of "bottom-light" Initial Mass…

Astrophysics · Physics 2007-05-23 L. Portinari , J. Sommer-Larsen , R. Tantalo

Observational data on rotation of Ap stars suggest that the bulk of their rotation rates form a separate Maxwellian distribution with an average value 3-4 times lower than the normal star distribution. No evidences for a significant angular…

Astrophysics · Physics 2007-05-23 K. Stepien

Rapidly rotating neutron stars in Low Mass X-ray Binaries have been proposed as an interesting source of gravitational waves. In this chapter we present estimates of the gravitational wave emission for various scenarios, given the…

From the masses of planets orbiting our Sun, and relative elemental abundances, it is estimated that at birth our Solar System required a minimum disk mass of ~0.01 solar masses within ~100 AU of the star. The main constituent, gaseous…

We show that $\varsigma$, the radial location of the minimum in the differential radial mass profile $M^\prime(r)$ of a galaxy cluster, can probe the theory of gravity. We derived $M^\prime(r)$ of the dark matter halos of galaxy clusters…

Cosmology and Nongalactic Astrophysics · Physics 2024-01-29 Michele Pizzardo , Antonaldo Diaferio , Kenneth J. Rines

We study the ejection of winds from thin accretion discs around stellar mass black holes and the time evolution of these winds in presence of radiation field generated by the accretion disc. Winds are produced by radiation, thermal pressure…

High Energy Astrophysical Phenomena · Physics 2021-01-06 Sananda Raychaudhuri , Mukesh K. Vyas , Indranil Chattopadhyay

The paper proposes an acceleration effect that a local short-time acceleration produces an additional broadening to spectral line, while the central value of the line remains unaffected. The effect can be considered as a local and…

General Relativity and Quantum Cosmology · Physics 2024-12-30 M. J. Luo

We used fully cosmological, high resolution N-body + SPH simulations to follow the formation of disk galaxies with a rotational velocity between 140 and 280 Km/sec in a Lambda CDM universe. The simulations include gas cooling, star…

Astrophysics · Physics 2007-05-23 Fabio Governato , Beth Willman , Lucio Mayer

This note attempts to interpret some of the recent findings about a downtrend in the mean azimuthal velocity of low [alpha/Fe] thin disc stars with increasing metallicity. The presence of such a trend was predicted in the model of…

Astrophysics of Galaxies · Physics 2015-06-03 Ralph Schoenrich

Angular momentum is transported outwards through an accretion disc by magnetohydrodynamical (MHD) turbulence thus allowing material to accrete on to the central object. The magneto-rotational instability (MRI) requires a minimum ionisation…

Solar and Stellar Astrophysics · Physics 2015-06-03 Rebecca G. Martin , Stephen H. Lubow , Mario Livio , J. E. Pringle

The Unruh effect states that a uniformly linearly accelerated observer with proper acceleration $a$ experiences Minkowski vacuum as a thermal state in the temperature $T_{\text{lin}} = a/(2\pi)$, operationally measurable via the detailed…

General Relativity and Quantum Cosmology · Physics 2023-03-28 Steffen Biermann , Sebastian Erne , Cisco Gooding , Jorma Louko , Jörg Schmiedmayer , William G. Unruh , Silke Weinfurtner

We present 2-D hydrodynamic simulation of rotating galactic winds driven by radiation. We study the structure and dynamics of the cool and/or warm component($T \simeq 10^4$ K) which is mixed with dust. We have taken into account the total…

Astrophysics of Galaxies · Physics 2015-06-04 Indranil Chattopadhyay , Mahavir Sharma , Biman B. Nath , Dongsu Ryu

Surveys of distant galaxies with the Hubble Space Telescope and from the ground have shown that there is only mild evolution in the relationship between radial size and stellar mass for galactic disks from z~1 to the present day. Using a…

We have investigated whether the lack of X-ray pulsations from most neutron star (NS) low-mass X-ray binaries (LMXBs) could be due to the extension of their inner disc to the NS surface. To estimate the inner disc radii, we have employed…

High Energy Astrophysical Phenomena · Physics 2024-06-27 Ndiogou Niang , Unal Ertan , Ali Arda Gencali , Ozan Toyran , Ayse Ulubay , Ebru Devlen , M. Ali Alpar , Erbil Gugercinoglu

A linear but global numerical model for the magnetorotational instability (MRI) in disk geometry is considered to estimate the instability parameters for galaxies. Similarity rules suggested by a local analysis are applied to reveal a…

Astrophysics · Physics 2016-08-16 L. L. Kitchatinov , G. Rüdiger

The rotational properties of the visible and dark components of low-mass disk galaxies (vrot<=100 km/s) are investigated using the Swaters sample. The rotational parameter lambda'=lambda_DM*(j_d/m_d) is determined, where lambda_DM is the…

Astrophysics · Physics 2007-05-23 Andreas Burkert

Utilizing a kinematic decomposition of simulated galaxies, we focus on galaxies with tiny kinematically inferred stellar halos, indicative of weak external influences. We investigate the intricate interplay between internal (natural) and…

Astrophysics of Galaxies · Physics 2024-06-12 Min Du , Hong-Chuan Ma , Wen-Yu Zhong , Luis C. Ho , Shihong Liao , Yingjie Peng

We have considered a cosmological model with a phenomenological model for the cosmological constant of the form $\Lambda=\bt\fr{\ddot R}{R}$, $ \bt$ is a constant. For age parameter consistent with observational data the Universe must be…

General Relativity and Quantum Cosmology · Physics 2017-08-23 Arbab I. Arbab

The rotation curves of low surface brightness galaxies provide a unique data set with which to test alternative theories of gravitation over a large dynamic range in size, mass, surface density, and acceleration. Many clearly fail,…

Astrophysics · Physics 2015-06-24 Stacy McGaugh , Erwin de Blok