scholarly journals Dynamical friction in disc galaxies with non-zero velocity dispersion

1996 ◽  
Vol 281 (4) ◽  
pp. 1165-1182 ◽  
Author(s):  
M. Wahde ◽  
K. J. Donner ◽  
B. Sundelius
Keyword(s):  
Velocity Dispersion ◽  
Dynamical Friction ◽  
Zero Velocity ◽  
Disc Galaxies

scholarly journals The mass–size plane of EAGLE galaxies

2019 ◽  
Vol 629 ◽  
pp. L3 ◽  
Author(s):  
M. S. Rosito ◽  
P. B. Tissera ◽  
S. E. Pedrosa ◽  
C. D. P. Lagos
Keyword(s):  
Velocity Dispersion ◽  
Bimodal Distribution ◽  
Early Type ◽  
Chemical Abundances ◽  
Radial Profiles ◽  
Mass Size ◽  
Hydrodynamical Simulations ◽  
Star Formation Histories ◽  
Disc Galaxies ◽  
Second Peak

Context. Current observational results show that both late- and early-type galaxies follow tight mass–size planes on which physical properties such as age, velocity dispersion, and metallicity correlate with the scatter on the plane. Aims. We study the mass–size plane of galaxies in cosmological hydrodynamical simulations, as a function of velocity dispersion, age, chemical abundances, ellipticity, and spin parameters with the aim of assessing to what extent the current cosmological paradigm can reproduce these observations and provide a physical interpretation of them. Methods. We selected a sample of well-resolved galaxies from the (100 Mpc)3 simulation of the EAGLE Project. This sample is composed of 508 spheroid-dominated galaxies and 1213 disc-dominated galaxies. The distributions of velocity dispersion, age, metallicity indicators and gradients, and spin parameters across the mass–size plane are analysed. Furthermore, we study the relation between shape and kinematic parameters. The results are compared with observations. Results. The mass-weighted ages of the EAGLE galaxies are found to vary along lines of constant velocity dispersion on the mass–size plane, except for galaxies with velocity dispersions higher than ∼150 km s−1. Negative age gradients tend to be found in extended disc galaxies in agreement with observations. However, the age distributions of early-type galaxies show a larger fraction with inverted radial profiles. The distribution of metallicity gradients does not show any clear dependence on this plane. Galaxies with similar spin parameters (λ) display larger sizes as their dynamical masses increase. Stellar-weighted ages are found to be good proxies for λ in galaxies with low ellipticity (ε). A bimodal distribution of λ is found so that the high-λ peak is dominated by discs with young stellar populations (SPs), while the second peak is mainly populated by slow rotators (λ <  0.2) with old stars. Our findings suggest that the physical processes that regulate the star formation histories in galaxies might also affect the angular moment budgets of gas and stars, and as a consequence their morphology.

scholarly journals Dynamical friction-driven orbital circularization in rotating discs: a semi-analytical description

2020 ◽  
Vol 494 (2) ◽  
pp. 3053-3059 ◽  
Author(s):  
Matteo Bonetti ◽  
Elisa Bortolas ◽  
Alessandro Lupi ◽  
Massimo Dotti ◽  
Sandra I Raimundo
Keyword(s):  
Analytical Approach ◽  
Analytical Description ◽  
Dynamical Friction ◽  
Angular Momenta ◽  
Rotating Discs ◽  
Disc Galaxies

ABSTRACT We present and validate a novel semi-analytical approach to study the effect of dynamical friction (DF) on the orbits of massive perturbers in rotating stellar discs. We find that DF efficiently circularizes the orbit of co-rotating perturbers, while it constantly increases the eccentricity of counter-rotating ones until their angular momenta reverse, then once again promoting circularization. Such ‘drag toward circular co-rotation’ could shape the distribution of orientations of kinematically decoupled cores in disc galaxies, naturally leading to the observed larger fraction of co-rotating cores.

scholarly journals A longslit spectroscopic survey of bulges in disc galaxies

2012 ◽  
Vol 10 (H16) ◽  
pp. 345-345
Author(s):  
Maximilian Fabricius ◽  
Roberto Saglia ◽  
David Fisher ◽  
Niv Drory ◽  
Ralf Bender ◽  
...  
Keyword(s):  
High Resolution ◽  
Velocity Dispersion ◽  
Low Resolution ◽  
Present Evidence ◽  
Counter Rotation ◽  
Two Systems ◽  
Velocity Dispersions ◽  
First Time ◽  
Disc Galaxies

AbstractWe use the Marcario Low Resolution Spectrograph (LRS) at the Hobby-Eberly-Telescope (HET) to study the kinematics of pseudobulges and classical bulges in 45 S0-Sc type galaxies in the nearby universe. Our high-resolution (instrumental σ ≈ 39 km s−1) spectra allo only to resolve the typical velocity dispersions of our targets but also to derive the h3 and h4 Gauss-Hermite moments. We demonstrate for the first time that purely kinematic diagnostics of the bulge dichotomy agree systematically with those based on Sérsic index. Low Sérsic index bulges have both increased rotational support (higher v/σ values) and on average lower central velocity dispersions. Pseudobulges have systematically shallower velocity dispersion profiles. The same correlation also holds when visual morphologies are used to diagnose bulge type. Finally, we present evidence for formerly undetected counter rotation in the two systems NGC 3945 and NGC 4736. With these, a total of 16% of the systems in or sample show signs for stellar counter rotation.

scholarly journals Numerical simulations of central stellar velocity dispersion drops in disc galaxies

2003 ◽  
Vol 409 (2) ◽  
pp. 469-477 ◽  
Author(s):  
H. Wozniak ◽  
F. Combes ◽  
E. Emsellem ◽  
D. Friedli
Keyword(s):  
Numerical Simulations ◽  
Velocity Dispersion ◽  
Stellar Velocity ◽  
Disc Galaxies

scholarly journals Fast galaxy bars continue to challenge standard cosmology

2021 ◽  
Vol 508 (1) ◽  
pp. 926-939
Author(s):  
Mahmood Roshan ◽  
Neda Ghafourian ◽  
Tahere Kashfi ◽  
Indranil Banik ◽  
Moritz Haslbauer ◽  
...  
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Dark Matter Halo ◽  
Dynamical Friction ◽  
Statistical Population ◽  
Barred Galaxies ◽  
Corotation Radius ◽  
Pattern Speeds ◽  
Hydrodynamical Simulations ◽  
Disc Galaxies

ABSTRACT Many observed disc galaxies harbour a central bar. In the standard cosmological paradigm, galactic bars should be slowed down by dynamical friction from the dark matter halo. This friction depends on the galaxy’s physical properties in a complex way, making it impossible to formulate analytically. Fortunately, cosmological hydrodynamical simulations provide an excellent statistical population of galaxies, letting us quantify how simulated galactic bars evolve within dark matter haloes. We measure bar strengths, lengths, and pattern speeds in barred galaxies in state-of-the-art cosmological hydrodynamical simulations of the IllustrisTNG and EAGLE projects, using techniques similar to those used observationally. We then compare our results with the largest available observational sample at redshift z = 0. We show that the tension between these simulations and observations in the ratio of corotation radius to bar length is 12.62σ (TNG50), 13.56σ (TNG100), 2.94σ (EAGLE50), and 9.69σ (EAGLE100), revealing for the first time that the significant tension reported previously persists in the recently released TNG50. The lower statistical tension in EAGLE50 is actually caused by it only having five galaxies suitable for our analysis, but all four simulations give similar statistics for the bar pattern speed distribution. In addition, the fraction of disc galaxies with bars is similar between TNG50 and TNG100, though somewhat above EAGLE100. The simulated bar fraction and its trend with stellar mass both differ greatly from observations. These dramatic disagreements cast serious doubt on whether galaxies actually have massive cold dark matter haloes, with their associated dynamical friction acting on galactic bars.

scholarly journals Massive Halos and the Stability of Hot Stellar Discs

1987 ◽  
Vol 117 ◽  
pp. 300-300
Author(s):  
E. Athanassoula ◽  
J. A. Sellwood
Keyword(s):  
Rotation Curve ◽  
Velocity Dispersion ◽  
Random Motion ◽  
Massive Halos ◽  
The Stability ◽  
Disc Galaxies

Bulge and halo material is often invoked to explain the absence of bars in the majority of disc galaxies, although the amount required is not known, in general, and is sensitive to the shape of the rotation curve. Here we show that the necessary fraction of spherical material is also affected by the degree of random motion amongst the disc stars. Quite moderate velocity dispersion has a strong stabilising influence and our hottest disc is stable without any halo (see also Kalnajs, this volume).

scholarly journals Tidal forces from the wake of dynamical friction: warps, lopsidedness, and kinematic misalignment

2020 ◽  
Vol 498 (1) ◽  
pp. 1080-1092
Author(s):  
Rain Kipper ◽  
María Benito ◽  
Peeter Tenjes ◽  
Elmo Tempel ◽  
Roberto de Propris
Keyword(s):  
Dark Matter ◽  
Velocity Dispersion ◽  
Position Angle ◽  
Back Reaction ◽  
Dynamical Friction ◽  
Matter Distribution ◽  
Tidal Forces ◽  
Isolated Galaxies ◽  
The Galaxy ◽  
Dark Matter Distribution

ABSTRACT A galaxy moving through a background of dark matter particles induces an overdensity of these particles or a wake behind it. The back reaction of this wake on the galaxy is a force field that can be decomposed into an effective deceleration (called dynamical friction) and a tidal field. In this paper, we determine the tidal forces, thus generated on the galaxy, and the resulting observables, which are shown to be warps, lopsidedness, and/or kinematic-photometric position angle misalignments. We estimate the magnitude of the tidal-like effects needed to reproduce the observed warp and lopsidedness on the isolated galaxy IC 2487. Within a realistic range of dark matter distribution properties, the observed, warped, and lopsided kinematical properties of IC 2487 are possible to reproduce (the background medium of dark matter particles has a velocity dispersion of $\lesssim 80\, {\rm km\, s^{-1}}$ and the density $10^4{\!-\!}10^5\, {\rm M_\odot \, kpc^{-3}}$, more likely at the lower end). We conclude that the proposed mechanism can generate warps, lopsidedness, and misalignments observed in isolated galaxies or galaxies in loose groups. The method can be used also to constrain dark matter spatial and velocity distribution properties.

scholarly journals Luminosity Segregation in Distant Galaxy Clusters

1987 ◽  
Vol 124 ◽  
pp. 519-521
Author(s):  
Guy Mathez ◽  
Olivier Le fèvre ◽  
Yannick Mellier ◽  
Genevieve Soucail ◽  
Alain Mazure
Keyword(s):  
Galaxy Clusters ◽  
Velocity Dispersion ◽  
Environmental Influence ◽  
Angular Separation ◽  
Dynamical Friction ◽  
Distant Galaxy ◽  
Show Evidence

Angular separation-magnitude plots drawn from deep photometry of galaxies in distant clusters show evidence for luminosity segregation which cannot be accounted for by field contamination. This segregation, interpreted in terms of dynamical friction, allows one to determine (M/L)g, the mass-to-light ratio of galaxies from their velocity dispersion. In A370 (z=0.37) more than 30 velocities have been measured by multi-aperture spectroscopy, leading to (M/L)g ∼70. Values greater than 100 are found in 5 other distant clusters by deriving the velocity dispersion from the richness. The luminosity segregation, observed even inside each of the clumps of 3C299, could result either from dynamical friction inside the clumps or from some early environmental influence.

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