Gas Density, Stability, and Starbursts near the Inner Lindblad Resonance of the Milky Way

2004 ◽  
Vol 614 (1) ◽  
pp. L41-L44 ◽  
Author(s):  
Antony A. Stark ◽  
Christopher L. Martin ◽  
Wilfred M. Walsh ◽  
Kecheng Xiao ◽  
Adair P. Lane ◽  
...  
Keyword(s):  
Milky Way ◽  
Gas Density ◽  
Lindblad Resonance ◽  
Inner Lindblad Resonance

scholarly journals Bar Formation in Milky Way type Galaxies

2016 ◽  
Vol 25 (4) ◽  
Author(s):  
E. V. Polyachenko ◽  
P. Berczik ◽  
A. Just
Keyword(s):  
Milky Way ◽  
Barred Galaxies ◽  
Numerical Evidence ◽  
Pattern Speed ◽  
Widespread Belief ◽  
Bar Formation ◽  
Lindblad Resonance ◽  
Inner Lindblad Resonance

AbstractMany barred galaxies, possibly including the Milky Way, have cusps in their centers. There is a widespread belief, however, that the usual bar instability, which occurs in bulgeless galaxy models, is impossible for cuspy models because of the presence of the inner Lindblad resonance for any pattern speed. At the same time, there is numerical evidence that the bar instability can form a bar. We analyze this discrepancy by performing accurate and diverse

scholarly journals Are ultra-diffuse galaxies Milky Way-sized?

2020 ◽  
Vol 633 ◽  
pp. L3 ◽  
Author(s):  
Nushkia Chamba ◽  
Ignacio Trujillo ◽  
Johan H. Knapen
Keyword(s):  
Star Formation ◽  
Milky Way ◽  
Size Range ◽  
Mass Density ◽  
Effective Radius ◽  
Density Profiles ◽  
Gas Density ◽  
Undesirable Consequence ◽  
Definition Of ◽  
Density Threshold

Now almost 70 years since its introduction, the effective or half-light radius has become a very popular choice for characterising galaxy size. However, the effective radius measures the concentration of light within galaxies and thus does not capture our intuitive definition of size which is related to the edge or boundary of objects. For this reason, we aim to demonstrate the undesirable consequence of using the effective radius to draw conclusions about the nature of faint ultra-diffuse galaxies (UDGs) when compared to dwarfs and Milky Way-like galaxies. Instead of the effective radius, we use a measure of galaxy size based on the location of the gas density threshold required for star formation. Compared to the effective radius, this physically motivated definition places the sizes much closer to the boundary of a galaxy. Therefore, considering the sizes and stellar mass density profiles of UDGs and regular dwarfs, we find that the UDGs have sizes that are within the size range of dwarfs. We also show that currently known UDGs do not have sizes comparable to Milky Way-like objects. We find that, on average, UDGs are ten times smaller in extension than Milky Way-like galaxies. These results show that the use of size estimators sensitive to the concentration of light can lead to misleading results.

scholarly journals A Nuclear Ring in the Sa(r!) Galaxy NGC 7742

1996 ◽  
Vol 157 ◽  
pp. 83-85 ◽  
Author(s):  
K. Wakamatsu ◽  
M. Hamabe ◽  
M. T. Nishida ◽  
A. Tomita
Keyword(s):  
Elliptical Galaxy ◽  
Formation Mechanisms ◽  
Main Body ◽  
Circular Symmetry ◽  
Barred Galaxies ◽  
Exclamation Mark ◽  
The Galaxy ◽  
Nuclear Ring ◽  
Lindblad Resonance ◽  
Inner Lindblad Resonance

NGC 7742 is well known for its prominent blue nuclear ring around an EO-like core, and so appears as a Hoag-type galaxy, an elliptical galaxy with an outer ring (Schweizer et al. 1987). The galaxy is classified as Sa(r!) in the Revised Shapley-Ames Catalog (Sandage and Tammann 1987) with an exclamation mark to emphasize the prominence of the ring. Its photographs are published in Laustsen et al. (1987), Wray (1988), and Sandage & Bedke (1994).The ring has a diameter of 19″ = 1.6 kpc at a distance of 17.1 Mpc (Buta & Crocker 1993), and so should be a nuclear ring of the galaxy. Nuclear rings and pseudorings are often detected in strongly barred (SB) galaxies, and interpreted to be linked to the inner Lindblad resonance (Buta & Crocker 1993). These nuclear features are, however, also found in some weakly-barred (SAB) and non-barred (SA) galaxies. NGC 7742 is a galaxy of the highest circular symmetry in its core, ring, and main body, and so the best object for a detailed study of formation mechanisms of nuclear rings in non-barred galaxies.

scholarly journals On the use of the WKBJ density wave theory at the Inner Lindblad Resonance region of our galaxy

1979 ◽  
Vol 84 ◽  
pp. 191-192
Author(s):  
E. Athanassoula
Keyword(s):  
Density Wave ◽  
Wave Theory ◽  
Resonance Region ◽  
Density Wave Theory ◽  
Lindblad Resonance ◽  
Inner Lindblad Resonance

I have tested the reliability of certain approximations involved in the asymptotic WKBJ density wave description of the inner Lindblad resonance (=ILR) of our galaxy.

scholarly journals 11.15. The effect of a central massive black hole on the gas fueling

1998 ◽  
Vol 184 ◽  
pp. 485-486
Author(s):  
H. Fukuda ◽  
A. Habe ◽  
K. Wada
Keyword(s):  
Black Hole ◽  
Numerical Simulations ◽  
Gravitational Potential ◽  
Galactic Center ◽  
The Self ◽  
Massive Black Hole ◽  
Nuclear Regions ◽  
Self Gravity ◽  
Lindblad Resonance ◽  
Inner Lindblad Resonance

Nuclear activities in galaxies, such as nuclear starbursts or AGNs, are supposed to be induced by gas fueling into nuclear regions of galaxies. Non-axisymmetric gravitational potential caused by a stellar bar is a convincing mechanism for triggering gas fueling (Phinney 1994). However, numerical simulations have shown that the bar can not force the gas to accrete toward the galactic center beyond the inner Lindblad resonance (ILR). As a mechanism to overcome the ILR barrier, the double barred structure (Friedli & Martinet 1993), or the self-gravity of gas (Wada & Habe 1992, 1995; Elmegreen 1994) are proposed.

scholarly journals Compact Array Mapping of the Nuclear Starburst in NGC 7552

1994 ◽  
Vol 158 ◽  
pp. 355-357
Author(s):  
Duncan A. Forbes ◽  
Ray P. Norris ◽  
Gerry M. Williger ◽  
R. Chris Smith
Keyword(s):  
High Resolution ◽  
Near Infrared ◽  
Starburst Galaxy ◽  
Angular Momenta ◽  
Lindblad Resonance ◽  
Inner Lindblad Resonance ◽  
Compact Array

We discuss new observations of the starburst galaxy NGC 7552. From optical and near–infrared colour maps we find a red, dusty circumnuclear ring. High-resolution radio mapping from the ATCA reveals the same ring, and a number of bright blobs (probably SNRs). The ring is probably associated with gas and dust which have lost angular momenta due to torques in the bar potential and settled at the inner Lindblad resonance. These circumnuclear starburst rings may be relatively common (when mapped without the obscuring affects of dust) and may play a role in collimating material of a nuclear outflow.

scholarly journals Stellar Orbits in Barred Galaxies with Nuclear Rings

1996 ◽  
Vol 157 ◽  
pp. 467-469
Author(s):  
Clayton H. Heller ◽  
Isaac Shlosman
Keyword(s):  
Large Range ◽  
Symmetric Pair ◽  
Dynamical Response ◽  
Instability Strip ◽  
Stellar Orbits ◽  
Barred Galaxies ◽  
Jacobi Integral ◽  
Elliptical Ring ◽  
Lindblad Resonance ◽  
Inner Lindblad Resonance

AbstractWe investigate the dynamical response of stellar orbits in a rotating barred galaxy potential to the perturbation by a nuclear gaseous ring. The change in 3D periodic orbit families is examined as the gas accumulates near the inner Lindblad resonance. It is found that the x2/x3 loop extends to higher Jacobi energy and a vertical instability strip forms in each family. These strips are connected by a symmetric/anti-symmetric pair of 2:2:1 3D orbital families. A significant distortion of the x1 orbits is observed in the vicinity of the ring, which leads to the intersection between orbits over a large range of the Jacobi integral. We also find that a moderately elliptical ring oblique to the stellar bar produces significant phase shifts in the x1 orbital response.

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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