Effect of the gas percentage on the thickness of the galactic discs during minor mergers using hydrodynamical simulations

2019 ◽  
Vol 14 (S353) ◽  
pp. 281-283
Author(s):  
Swetha Thakkalapally ◽  
Priya Hasan ◽  
S. N. Hasan
Keyword(s):  
Initial Conditions ◽  
Mass Ratio ◽  
Galactic Disc ◽  
Gaseous Component ◽  
Hydrodynamical Simulations ◽  
Minor Mergers ◽  
Disc Galaxies

AbstractWe study the minor mergers of galaxies using simulations. For this we use GADGET2 code. We present results of simulations of minor mergers of disc galaxies of mass ratio 1:10. These simulations consist of collisionless as well as hydrodynamical runs including a gaseous component in the galactic disc of primary galaxy. Our goal is to establish the characteristics of discs obtained after the merger.We observe that the primary galaxy discs are not destroyed after the merger. We take different initial conditions for the primary galaxy varying the gas percentage in disc from 0–40 percentage and study the thickness of the disc after the merger. We generally observe that the thickness of the disc increases after the merger for any gas percentage. We also observe that as the gas percentage increases in the disc of initial primary galaxy, the increase in the thickness keeps decreasing.

scholarly journals The anisotropy of the power spectrum in periodic cosmological simulations

2021 ◽  
Vol 503 (4) ◽  
pp. 5638-5645
Author(s):  
Gábor Rácz ◽  
István Szapudi ◽  
István Csabai ◽  
László Dobos
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Initial Conditions ◽  
Power Spectra ◽  
Cosmological Simulations ◽  
Spherical Collapse ◽  
Lower Amplitude ◽  
Hydrodynamical Simulations

ABSTRACT The classical gravitational force on a torus is anisotropic and always lower than Newton’s 1/r2 law. We demonstrate the effects of periodicity in dark matter only N-body simulations of spherical collapse and standard Lambda cold dark matter (ΛCDM) initial conditions. Periodic boundary conditions cause an overall negative and anisotropic bias in cosmological simulations of cosmic structure formation. The lower amplitude of power spectra of small periodic simulations is a consequence of the missing large-scale modes and the equally important smaller periodic forces. The effect is most significant when the largest mildly non-linear scales are comparable to the linear size of the simulation box, as often is the case for high-resolution hydrodynamical simulations. Spherical collapse morphs into a shape similar to an octahedron. The anisotropic growth distorts the large-scale ΛCDM dark matter structures. We introduce the direction-dependent power spectrum invariant under the octahedral group of the simulation volume and show that the results break spherical symmetry.

scholarly journals Probing gas disc physics with LISA: simulations of an intermediate mass ratio inspiral in an accretion disc

2019 ◽  
Vol 486 (2) ◽  
pp. 2754-2765 ◽  
Author(s):  
A M Derdzinski ◽  
D D’Orazio ◽  
P Duffell ◽  
Z Haiman ◽  
A MacFadyen
Keyword(s):  
Small Deviation ◽  
Compact Object ◽  
Accretion Disc ◽  
Mass Ratio ◽  
Intermediate Mass ◽  
Laser Interferometer Space Antenna ◽  
Total Phase ◽  
Accretion Rates ◽  
Hydrodynamical Simulations ◽  
And Migration

Abstract The coalescence of a compact object with a $10^{4}\hbox{--}10^{7}\, {\rm M_\odot }$ supermassive black hole (SMBH) produces mHz gravitational waves (GWs) detectable by the future Laser Interferometer Space Antenna (LISA). If such an inspiral occurs in the accretion disc of an active galactic nucleus (AGN), the gas torques imprint a small deviation in the GW waveform. Here, we present two-dimensional hydrodynamical simulations with the moving-mesh code disco of a BH inspiraling at the GW rate in a binary system with a mass ratio q = M2/M1 = 10−3, embedded in an accretion disc. We assume a locally isothermal equation of state for the gas (with Mach number $\mathcal {M}=20$) and implement a standard α-prescription for its viscosity (with α = 0.03). We find disc torques on the binary that are weaker than in previous semi-analytic toy models, and are in the opposite direction: the gas disc slows down, rather than speeds up the inspiral. We compute the resulting deviations in the GW waveform, which scale linearly with the mass of the disc. The SNR of these deviations accumulates mostly at high frequencies, and becomes detectable in a 5 yr LISA observation if the total phase shift exceeds a few radians. We find that this occurs if the disc surface density exceeds $\Sigma _0 \gtrsim 10^{2-3}\rm g\, cm^{-2}$, as may be the case in thin discs with near-Eddington accretion rates. Since the characteristic imprint on the GW signal is strongly dependent on disc parameters, a LISA detection of an intermediate mass ratio inspiral would probe the physics of AGN discs and migration.

scholarly journals Forming bulges during galaxy minor mergers

2007 ◽  
Vol 3 (S245) ◽  
pp. 63-66 ◽  
Author(s):  
T. J. Cox ◽  
J. Younger ◽  
L. Hernquist ◽  
P. F. Hopkins
Keyword(s):  
Black Hole ◽  
Large Mass ◽  
Elliptical Galaxies ◽  
Equal Mass ◽  
Mass Ratio ◽  
Black Hole Growth ◽  
Major Merger ◽  
Hole Growth ◽  
Minor Mergers ◽  
Large Mass Ratio

AbstractThe hierarchical formation of structure suggests that dark halos, and the galaxies they host, are shaped by their merging history. While the idea that mergers between galaxies of equal mass, i.e., major merger, produce elliptical galaxies has received considerable attention, he galaxies that result from minor merger, i.e., mergers between galaxies with a large mass ratio, is much less understood. We have performed a large number of numerical simulations of minor mergers, including cooling, star formation, and black hole growth in order to study this process in more detail. This talk will present some preliminary results of this study, and in particular, the morphology and kinematics of minor merger remnants.

scholarly journals Kinematical signatures of disc instabilities and secular evolution in the MUSE TIMER Survey

2019 ◽  
Vol 14 (S353) ◽  
pp. 135-139
Author(s):  
Dimitri A. Gadotti ◽  
Adrian Bittner ◽  
Jesus Falcón-Barroso ◽  
Jairo Méndez-Abreu ◽  
Keyword(s):  
Spatial Resolution ◽  
High Signal ◽  
Stellar Kinematics ◽  
Secular Evolution ◽  
Integral Field Spectroscopy ◽  
Central Regions ◽  
Hydrodynamical Simulations ◽  
Cosmic History ◽  
Disc Galaxies ◽  
Integral Field

AbstractThe MUSE TIMER Survey has obtained high signal and high spatial resolution integral-field spectroscopy data of the inner ~ 6×6 kpc of 21 nearby massive disc galaxies. This allows studies of the stellar kinematics of the central regions of massive disc galaxies that are unprecedented in spatial resolution. We confirm previous predictions from numerical and hydrodynamical simulations of the effects of bars and inner bars on stellar and gaseous kinematics, and also identify box/peanuts via kinematical signatures in mildly and moderately inclined galaxies, including a box/peanut in a face-on inner bar. In 20/21 galaxies we find inner discs and show that their properties are fully consistent with the bar-driven secular evolution picture for their formation. In addition, we show that these inner discs have, in the region where they dominate, larger rotational support than the main galaxy disc, and discuss how their stellar population properties can be used to estimate when in cosmic history the main bar formed. Our results are compared with photometric studies in the context of the nature of galaxy bulges and we show that inner discs are identified in image decompositions as photometric bulges with exponential profiles (i.e., Sérsic indices near unity).

scholarly journals The distribution of metals in cosmological hydrodynamical simulations of dwarf disc galaxies

2012 ◽  
Vol 425 (2) ◽  
pp. 969-978 ◽  
Author(s):  
K. Pilkington ◽  
B. K. Gibson ◽  
C. B. Brook ◽  
F. Calura ◽  
G. S. Stinson ◽  
...  
Keyword(s):  
Hydrodynamical Simulations ◽  
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 Radiation hydrodynamics simulations of the evolution of the diffuse ionized gas in disc galaxies

2019 ◽  
Vol 488 (2) ◽  
pp. 1977-1986 ◽  
Author(s):  
Bert Vandenbroucke ◽  
Kenneth Wood
Keyword(s):  
Pressure Support ◽  
Numerical Models ◽  
Fine Tuning ◽  
Radiation Budget ◽  
Radiation Hydrodynamics ◽  
Galactic Disc ◽  
Ionized Gas ◽  
Diffuse Ionized Gas ◽  
Gas Layer ◽  
Disc Galaxies

ABSTRACT There is strong evidence that the diffuse ionized gas (DIG) in disc galaxies is photoionized by radiation from UV luminous O and B stars in the galactic disc, both from observations and detailed numerical models. However, it is still not clear what mechanism is responsible for providing the necessary pressure support for a diffuse gas layer at kpc-scale above the disc. In this work, we investigate if the pressure increase caused by photoionization can provide this support. We run self-consistent radiation hydrodynamics (RHD) models of a gaseous disc in an external potential. We find that photoionization feedback can drive low levels of turbulence in the dense galactic disc, and that it provides pressure support for an extended diffuse gas layer. Our results show that there is a natural fine-tuning between the total ionizing radiation budget of the sources in the galaxy and the amount of gas in the different ionization phases of the interstellar medium, and provide the first fully consistent RHD model of the DIG.

scholarly journals Mapping the Galactic disc with the LAMOST and Gaia red clump sample: II. 3D asymmetrical kinematics of mono-age populations in the disc between 6–14  kpc

2019 ◽  
Vol 491 (2) ◽  
pp. 2104-2118 ◽  
Author(s):  
H-F Wang ◽  
M López-Corredoira ◽  
Y Huang ◽  
J L Carlin ◽  
B-Q Chen ◽  
...  
Keyword(s):  
Milky Way ◽  
Galactic Disc ◽  
Giant Stars ◽  
Bending Mode ◽  
Red Clump ◽  
Minor Mergers ◽  
Gaia Dr2 ◽  
South Asymmetry ◽  
Spiral Arm ◽  
Fast Rotating

ABSTRACT We perform analysis of the 3D kinematics of Milky Way disc stars in mono-age populations. We focus on stars between Galactocentric distances of R = 6 and 14  kpc, selected from the combined LAMOST Data Release 4 (DR4) red clump giant stars and Gaia DR2 proper motion catalogue. We confirm the 3D asymmetrical motions of recent works and provide time tagging of the Galactic outer disc asymmetrical motions near the anticentre direction out to Galactocentric distances of 14 kpc. Radial Galactocentric motions reach values up to 10 km s−1, depending on the age of the population, and present a north–south asymmetry in the region corresponding to density and velocity substructures that were sensitive to the perturbations in the early 6  Gyr. After that time, the disc stars in this asymmetrical structure have become kinematically hotter, and are thus not sensitive to perturbations, and we find the structure is a relatively younger population. With quantitative analysis, we find stars both above and below the plane at R ≳ 9 kpc that exhibit bending mode motions of which the sensitive duration is around 8  Gyr. We speculate that the in-plane asymmetries might not be mainly caused by a fast rotating bar, intrinsically elliptical outer disc, secular expansion of the disc, or streams. Spiral arm dynamics, out-of-equilibrium models, minor mergers or others are important contributors. Vertical motions might be dominated by bending and breathing modes induced by complicated inner or external perturbers. It is likely that many of these mechanisms are coupled together.

scholarly journals Origin of structures in disc galaxies: internal or external processes?

2012 ◽  
Vol 10 (H16) ◽  
pp. 322-322
Author(s):  
E. Athanassoula
Keyword(s):  
Internal Process ◽  
Minor Mergers ◽  
Different Origins ◽  
Disc Galaxies ◽  
Do So

AbstractDisc galaxies have a number of structures, such as bars, spirals, rings, discy bulges, m = 1 asymmetries, thick discs, warps etc. I will summarise what is known about their origin and in particular whether it is due to an external or an internal process. The former include interactions, major or minor mergers etc, while the latter include instabilities, or driving by another component of the same galaxy, as e.g. the bar or the halo. In cases where more than one process is eligible, I will analyse whether it is possible to distinguish between different origins, and what it would take to do so. This discussion will show that, at least in some cases, it is difficult to distinguish between an internal and an external origin.

scholarly journals Galaxies that shine: radiation-hydrodynamical simulations of disc galaxies

2015 ◽  
Vol 451 (1) ◽  
pp. 34-58 ◽  
Author(s):  
Joakim Rosdahl ◽  
Joop Schaye ◽  
Romain Teyssier ◽  
Oscar Agertz
Keyword(s):  
Hydrodynamical Simulations ◽  
Disc Galaxies
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