scholarly journals The angular momentum of disc galaxies: implications for gas accretion, outflows, and dynamical friction

2012 ◽  
pp. no-no ◽  
Author(s):  
Aaron A. Dutton ◽  
Frank C. van den Bosch
Keyword(s):  
Angular Momentum ◽  
Dynamical Friction ◽  
Gas Accretion ◽  
Disc Galaxies

scholarly journals Angular Momentum Accretion onto Disc Galaxies

2018 ◽  
Vol 14 (A30) ◽  
pp. 228-232
Author(s):  
Filippo Fraternali ◽  
Gabriele Pezzulli
Keyword(s):  
Angular Momentum ◽  
Star Formation ◽  
Momentum Distribution ◽  
Intergalactic Medium ◽  
Star Forming ◽  
Gas Accretion ◽  
Hot Corona ◽  
Inside Out ◽  
Disc Galaxies ◽  
Hubble Time

AbstractThroughout the Hubble time, gas makes its way from the intergalactic medium into galaxies fuelling their star formation and promoting their growth. One of the key properties of the accreting gas is its angular momentum, which has profound implications for the evolution of, in particular, disc galaxies. Here, we discuss how to infer the angular momentum of the accreting gas using observations of present-day galaxy discs. We first summarize evidence for ongoing inside-out growth of star forming discs. We then focus on the chemistry of the discs and show how the observed metallicity gradients can be explained if gas accretes onto a disc rotating with a velocity 20 – 30% lower than the local circular speed. We also show that these gradients are incompatible with accretion occurring at the edge of the discs and flowing radially inward. Finally, we investigate gas accretion from a hot corona with a cosmological angular momentum distribution and describe how simple models of rotating coronae guarantee the inside-out growth of disc galaxies.

scholarly journals Effects of initial density profiles on massive star cluster formation in giant molecular clouds

2021 ◽  
Author(s):  
Yingtian Chen ◽  
Hui Li ◽  
Mark Vogelsberger
Keyword(s):  
Angular Momentum ◽  
Star Formation ◽  
Molecular Clouds ◽  
Globular Clusters ◽  
Cluster Formation ◽  
Initial Density ◽  
Giant Molecular Clouds ◽  
Density Profiles ◽  
Stellar Feedback ◽  
Gas Accretion

Abstract We perform a suite of hydrodynamic simulations to investigate how initial density profiles of giant molecular clouds (GMCs) affect their subsequent evolution. We find that the star formation duration and integrated star formation efficiency of the whole clouds are not sensitive to the choice of different profiles but are mainly controlled by the interplay between gravitational collapse and stellar feedback. Despite this similarity, GMCs with different profiles show dramatically different modes of star formation. For shallower profiles, GMCs first fragment into many self-gravitation cores and form sub-clusters that distributed throughout the entire clouds. These sub-clusters are later assembled ‘hierarchically’ to central clusters. In contrast, for steeper profiles, a massive cluster is quickly formed at the center of the cloud and then gradually grows its mass via gas accretion. Consequently, central clusters that emerged from clouds with shallower profiles are less massive and show less rotation than those with the steeper profiles. This is because 1) a significant fraction of mass and angular momentum in shallower profiles is stored in the orbital motion of the sub-clusters that are not able to merge into the central clusters 2) frequent hierarchical mergers in the shallower profiles lead to further losses of mass and angular momentum via violent relaxation and tidal disruption. Encouragingly, the degree of cluster rotations in steeper profiles is consistent with recent observations of young and intermediate-age clusters. We speculate that rotating globular clusters are likely formed via an ‘accretion’ mode from centrally-concentrated clouds in the early Universe.

scholarly journals Galaxy Dynamics: Secular Evolution and Accretion

2010 ◽  
Vol 6 (S271) ◽  
pp. 119-126 ◽  
Author(s):  
Francoise Combes
Keyword(s):  
Angular Momentum ◽  
Galaxy Evolution ◽  
Resonant Scattering ◽  
Relative Role ◽  
Radial Migration ◽  
Galaxy Dynamics ◽  
Secular Evolution ◽  
Minor Mergers ◽  
Gas Accretion

AbstractRecent results are reviewed on galaxy dynamics, bar evolution, destruction and re-formation, cold gas accretion, gas radial flows and AGN fueling, minor mergers. Some problems of galaxy evolution are discussed in particular, exchange of angular momentum, radial migration through resonant scattering, and consequences on abundance gradients, the frequency of bulgeless galaxies, and the relative role of secular evolution and hierarchical formation.

scholarly journals Structural diversity of disc galaxies originating in the cold gas inflow from cosmic webs

2020 ◽  
Vol 494 (1) ◽  
pp. L37-L41
Author(s):  
Masafumi Noguchi
Keyword(s):  
High Redshift ◽  
Morphological Diversity ◽  
Structural Diversity ◽  
High Mass ◽  
Cold Flow ◽  
Hubble Sequence ◽  
The Galaxy ◽  
Gas Accretion ◽  
Disc Galaxies ◽  
Cold Gas

ABSTRACT Disc galaxies show a large morphological diversity with varying contribution of three major structural components: thin discs, thick discs, and central bulges. Dominance of bulges increases with the galaxy mass (Hubble sequence), whereas thick discs are more prominent in lower mass galaxies. Because galaxies grow with the accretion of matter, this observed variety should reflect diversity in accretion history. On the basis of the prediction by the cold-flow theory for galactic gas accretion and inspired by the results of previous studies, we put a hypothesis that associates different accretion modes with different components. Namely, thin discs form as the shock-heated hot gas in high-mass haloes gradually accretes to the central part, thick discs grow by the direct accretion of cold gas from cosmic webs when the halo mass is low, and finally bulges form by the inflow of cold gas through the shock-heated gas in high-redshift massive haloes. We show that this simple hypothesis reproduces the mean observed variation of galaxy morphology with the galaxy mass. This scenario also predicts that thick discs are older and poorer in metals than thin discs, in agreement with the currently available observations.

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 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 Stellar bars in counter-rotating dark matter haloes: the role of halo orbit reversals

2019 ◽  
Vol 489 (3) ◽  
pp. 3102-3115 ◽  
Author(s):  
Angela Collier ◽  
Isaac Shlosman ◽  
Clayton Heller
Keyword(s):  
Dark Matter ◽  
Angular Momentum ◽  
Galaxy Evolution ◽  
Secular Evolution ◽  
Resonant Interactions ◽  
Disc Galaxies ◽  
Simulation Time ◽  
Lindblad Resonance ◽  
Inner Lindblad Resonance

Abstract Disc galaxies can exchange angular momentum and baryons with their host dark matter (DM) haloes. These haloes possess internal spin, λ, which is insignificant rotationally but does affect interactions between the baryonic and DM components. While statistics of prograde and retrograde spinning haloes in galaxies is not available at present, the existence of such haloes is important for galaxy evolution. In the previous works, we analysed dynamical and secular evolution of stellar bars in prograde spinning haloes and the DM response to the bar perturbation, and found that it is modified by the resonant interactions between the bar and the DM halo orbits. In this work, we follow the evolution of stellar bars in retrograde haloes. We find that this evolution differs substantially from evolution in rigid unresponsive haloes, discussed in the literature. First, we confirm that the bar instability is delayed progressively along the retrograde λ sequence. Secondly, the bar evolution in the retrograde haloes differs also from that in the prograde haloes, in that the bars continue to grow substantially over the simulation time of 10 Gyr. The DM response is also substantially weaker compared to this response in the prograde haloes. Thirdly, using orbital spectral analysis of the DM orbital structure, we find a phenomenon we call the orbit reversal – when retrograde DM orbits interact with the stellar bar, reverse their streaming and precession, and become prograde. This process dominates the inner halo region adjacent to the bar and allows these orbits to be trapped by the bar, thus increasing efficiency of angular momentum transfer by the inner Lindblad resonance. We demonstrate this reversal process explicitly in a number of examples.

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