scholarly journals Gas accretion from the cosmic web feeding disk galaxies

2016 ◽  
Vol 11 (S321) ◽  
pp. 208-210
Author(s):  
J. Sánchez Almeida ◽  
A. Olmo-García ◽  
B. G. Elmegreen ◽  
C. Muñoz-Tuñón ◽  
D. M. Elmegreen ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Host Galaxy ◽  
Disk Galaxies ◽  
Preliminary Results ◽  
Tidal Forces ◽  
Accretion Process ◽  
Gas Accretion

AbstractDisk galaxies in cosmological numerical simulations grow by accreting gas from the cosmic web. This gas reaches the external disk, and then spirals in dragged along by tidal forces and/or disk instabilities. The importance of gas infall is as clear from numerical simulations as it is obscure to observations. Extremely metal poor (XMP) galaxies seem to be the best example we have of the gas accretion process at work. They have large off-center starbursts which show significant metallicity drop compared with the host galaxy. This observation is naturally explained as a gas accretion event caught in the act. We present preliminary results of the kinematical properties of the metal poor starbursts in XMPs, which suggest that the starbursts are kinematically decoupled entities within the host galaxy.

scholarly journals LIPAD Simulations of Giant Planet Core Formation

2013 ◽  
Vol 8 (S299) ◽  
pp. 171-172
Author(s):  
Henry Ngo ◽  
Martin J. Duncan ◽  
Harold F. Levison
Keyword(s):  
Numerical Simulations ◽  
Giant Planet ◽  
Giant Planets ◽  
Core Formation ◽  
Preliminary Results ◽  
Gas Giant ◽  
Gas Accretion ◽  
Collisional Evolution

AbstractWe present some preliminary results from our investigation of giant planetary core formation using numerical simulations with the Lagrangian Integrator for Planetary Accretion and Dynamics (LIPAD) by Levison et al. (2012). LIPAD couples dynamics with collisional evolution, including fragmentation. We start with a cold planetesimal disk using particles of a few kilometres in size. Our simulations show growth from kilometre-sized planetesimals to several Earth-mass sized embryos (tens of thousands of kilometers) can occur. However, these embryos may not be large enough to start runaway gas accretion necessary to build the envelopes of gas giant planets.

scholarly journals Detecting the halo heating from AGN feedback with ALMA

2019 ◽  
Vol 490 (4) ◽  
pp. 5134-5146 ◽  
Author(s):  
S Brownson ◽  
R Maiolino ◽  
M Tazzari ◽  
S Carniani ◽  
N Henden
Keyword(s):  
Star Formation ◽  
Correction Factor ◽  
Spatial Scales ◽  
Complex Structure ◽  
Host Galaxy ◽  
Cosmological Simulations ◽  
Beam Attenuation ◽  
Gas Accretion ◽  
Marginal Detection ◽  
Compact Sources

ABSTRACT The Sunyaev–Zel’dovich (SZ) effect can potentially be used to investigate the heating of the circumgalactic medium and subsequent suppression of cold gas accretion on to the host galaxy caused by quasar feedback. We use a deep ALMA observation of HE0515-4414 in band 4, the most luminous quasar known at the peak of cosmic star formation (z = 1.7), to search for the SZ signal tracing the heating of the galaxy’s halo. ALMA’s sensitivity to a broad range of spatial scales enables us to disentangle emitting compact sources from the negative, extended SZ signal. We obtain a marginal SZ detection (∼3.3σ) on scales of about 300 kpc (30–40 arcsec), at the 0.2 mJy level, 0.5 mJy after applying a correction factor for primary beam attenuation and flux that is resolved out by the array. We show that our result is consistent with a simulated ALMA observation of a similar quasar in the fable cosmological simulations. We emphasize that detecting an SZ signal is more easily achieved in the visibility plane than in the (inferred) images. We also confirm a marginal detection (3.2σ) of a potential SZ dip on smaller scales (<100 kpc) already claimed by other authors, possibly highlighting the complex structure of the halo heating. Finally, we use SZ maps from the fable cosmological simulations, convolved with ALMA simulations, to illustrate that band 3 observations are much more effective in detecting the SZ signal with higher significance, and discuss the optimal observing strategy.

scholarly journals Radial migration in barred galaxies

2012 ◽  
Vol 10 (H16) ◽  
pp. 355-355
Author(s):  
P. Di Matteo ◽  
M. Haywood ◽  
F. Combes ◽  
B. Semelin ◽  
C. Babusiaux ◽  
...  
Keyword(s):  
High Resolution ◽  
Numerical Simulations ◽  
Disk Galaxies ◽  
List Type ◽  
Stellar Content ◽  
Radial Migration ◽  
Barred Galaxies ◽  
Corotation Radius ◽  
Low Activity ◽  
Metallicity Distribution

AbstractIn this talk, I will present the result of high resolution numerical simulations of disk galaxies with various bulge/disk ratios evolving isolated, showing that: •Most of migration takes place when the bar strength is high and decreases in the phases of low activity (in agreement with the results by Brunetti et el. 2011, Minchev et al. 2011).•Most of the stars inside the corotation radius (CR) do not migrate in the outer regions, but stay confined in the inner disk, while stars outside CR can migrate either inwards or outwards, diffusing over the whole disk.•Migration is accompanied by significative azimuthal variations in the metallicity distribution, of the order of 0.1 dex for an initial gradient of ~-0.07 dex/kpc.•Boxy bulges are an example of stellar structures whose properties (stellar content, vertical metallicity, [α/Fe] and age gradients, ..) are affected by radial migration (see also Fig. 1).

scholarly journals Dynamical Friction in Disk Galaxies: The Radial Dependence

1996 ◽  
Vol 157 ◽  
pp. 372-374
Author(s):  
Mattias Wahde ◽  
Karl Johan Donner
Keyword(s):  
Numerical Simulations ◽  
Decay Time ◽  
Circular Orbit ◽  
Simple Formula ◽  
Radial Dependence ◽  
Disk Galaxies ◽  
Dynamical Friction ◽  
Satellite Galaxy ◽  
Parent Galaxy ◽  
Good Agreement

AbstractA simple formula is derived for the force of dynamical friction acting on a satellite galaxy which is moving on a nearly circular orbit around its parent galaxy. Using this formula, estimates of the decay time are computed. The results are then compared with the corresponding results from numerical simulations, and are found to be in good agreement.

scholarly journals Very high redshift quasars and the rapid emergence of super-massive black holes

2020 ◽  
Author(s):  
Pavel Kroupa ◽  
Ladislav Subr ◽  
Tereza Jerabkova ◽  
Long Wang
Keyword(s):  
Black Hole ◽  
Massive Star ◽  
High Redshift ◽  
Host Galaxy ◽  
Massive Black Hole ◽  
First Stars ◽  
Massive Black Holes ◽  
Nuclear Cluster ◽  
Gas Accretion ◽  
Very High

Abstract The observation of quasars at very high redshift such as Pōniuā’ena is a challenge for models of super-massive black hole (SMBH) formation. This work presents a study of SMBH formation via known physical processes in star-burst clusters formed at the onset of the formation of their hosting galaxy. While at the early stages hyper-massive star-burst clusters reach the luminosities of quasars, once their massive stars die, the ensuing gas accretion from the still forming host galaxy compresses its stellar black hole (BH) component to a compact state overcoming heating from the BH–BH binaries such that the cluster collapses, forming a massive SMBH-seed within about a hundred Myr. Within this scenario the SMBH–spheroid correlation emerges near-to-exactly. The highest-redshift quasars may thus be hyper-massive star-burst clusters or young ultra-compact dwarf galaxies (UCDs), being the precursors of the SMBHs that form therein within about 200 Myr of the first stars. For spheroid masses ≲ 109.6 M⊙ a SMBH cannot form and instead only the accumulated nuclear cluster remains. The number evolution of the quasar phases with redshift is calculated and the possible problem of missing quasars at very high redshift is raised. SMBH-bearing UCDs and the formation of spheroids are discussed critically in view of the high redshift observations. A possible tension is found between the high star-formation rates (SFRs) implied by downsizing and the observed SFRs, which may be alleviated within the IGIMF theory and if the downsizing times are somewhat longer.

scholarly journals Dynamo Action in Accretion Disks

1993 ◽  
Vol 157 ◽  
pp. 209-210
Author(s):  
Ulf Torkelsson
Keyword(s):  
Numerical Simulations ◽  
Accretion Disk ◽  
Accretion Disks ◽  
Standard Theory ◽  
Dynamo Action ◽  
Preliminary Results

Employing the standard theory for thin accretion disks I estimate the relevant parameters for a dynamo in an accretion disk. These estimates could then be compared to the results of numerical simulations. Some preliminary results of such simulations (Torkelsson & Brandenburg 1992) are presented too.

scholarly journals Numerical Simulations of 3D Metallic Auxetic Metamaterials in both Compression and Tension

2016 ◽  
Vol 846 ◽  
pp. 565-570 ◽  
Author(s):  
Xin Ren ◽  
Jian Hu Shen ◽  
Arash Ghaedizadeh ◽  
Hong Qi Tian ◽  
Mike Xie
Keyword(s):  
Mechanical Properties ◽  
Numerical Simulations ◽  
Large Deformation ◽  
Scale Factor ◽  
Research Interest ◽  
Preliminary Results ◽  
Auxetic Materials ◽  
Tension And Compression ◽  
Pattern Scale ◽  
Intense Research

Auxetic materials exhibit uncommon behaviour, i.e. they will shrink (expand) laterally under compression (tension). This novel feature has attracted intense research interest. However, most of previous works focus on auxetic behaviour in either compression or tension. Most of the auxetic materials are not symmetric in tension and compression under large deformation. Studies on the auxetic performance of metamaterials both in compression and tension are important but rare. As an extension of our previous research on compressive auxetic performance of 3D metallic auxetic metamaterials, numerical simulations were carried out to investigate the auxetic and other mechanical properties of the 3D metallic auxetic metamaterials in tension. The preliminary results indicated that the designed 3D metallic auxetic metamaterials exhibited better auxetic performance in compression than in tension. By increasing a pattern scale factor, auxetic performance of the 3D metallic auxetic metamaterials under tension can be improved. With proper adjustment of the pattern scale factor, an approximately symmetric auxetic performance could be achieved in compression and tension.

scholarly journals Probing the QSO host galaxy evolution through the gas metallicity

2012 ◽  
Vol 8 (S295) ◽  
pp. 269-269
Author(s):  
B. Husemann ◽  
L. Wisotzki ◽  
K. Jahnke ◽  
S. F. Sánchez ◽  
D. Nugroho
Keyword(s):  
Gas Phase ◽  
Galaxy Evolution ◽  
Host Galaxy ◽  
Host Galaxies ◽  
Spatially Resolved ◽  
Gas Accretion

AbstractWe use the spatially resolved gas-phase metallicity as a new diagnostic for tagging recent interactions in QSO host galaxies. With this technique we also identified a QSO with extremely low gas-phase metallicity as likely evidence for gas accretion from the environment.

scholarly journals Secular evolution in galaxies

2006 ◽  
Vol 2 (S235) ◽  
pp. 19-23 ◽  
Author(s):  
F. Combes
Keyword(s):  
Star Formation ◽  
Numerical Simulations ◽  
Significant Role ◽  
High Frequency ◽  
Central Star ◽  
Barred Galaxies ◽  
Secular Evolution ◽  
Gas Accretion ◽  
Bar Formation

AbstractNew observations in favour of a significant role of secular evolution are reviewed: central star formation boosted in pseudo-bulge barred galaxies, relations between bulge and disk, evidence for rejuvenated bulges. Numerical simulations have shown that secular evolution can occur through a cycle of bar formation and destruction, in which the gas plays a major role. Since bars are weakened or destroyed in gaseous disks, the high frequency of bars observed today requires external cold gas accretion, to replenish the disk and allow a new bar formation. The rate of gas accretion from external filaments is compatible with what is observed in cosmological simulations.

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