scholarly journals Presence and Absence of Outer Rings in Barred Galaxies

2000 ◽  
Vol 174 ◽  
pp. 330-333
Author(s):  
P. Rautiainen ◽  
H. Salo
Keyword(s):  
Major Axis ◽  
Spiral Arms ◽  
Barred Galaxies ◽  
Near Ir ◽  
Closed Orbits ◽  
Detailed Classification ◽  
Different Types ◽  
Particle Simulations ◽  
Barred Spiral Galaxies ◽  
Lindblad Resonance

Many barred spiral galaxies have an outer ring (R) or a pseudoring (R') in their outer disk. R. Buta (e.g. Buta 1995) has developed a detailed classification for different types of outer rings. Two main families of outer rings are recognized. In R1 family the major axis of the ring is perpendicular to the bar and the spiral arms wind 180° before meeting the other arm. In R2 family the major axis of the ring is parallel to the bar and the spiral arms wind 270°.The outer rings are usually considered to be related to the outer Lindblad resonance (OLR) of a rotating stellar bar. The ring shapes correspond to families of closed orbits in the vicinity of this resonance (e.g. Contopoulos & Grosbøl 1989), and also the sizes of the outer rings relative to the bar component fit to this suggestion. Furthermore, test-particle simulations which use analytical bar potentials can produce different types of outer rings near the OLR (Schwarz 1981; Byrd et al. 1994). We have obtained similar results when we modelled ringed galaxy IC 4214 by constructing the gravitational potential from near-IR observations (Buta et al. 1999; Salo et al. 1999).

scholarly journals Dynamical effects of the spiral arms on the velocity distribution of disc stars

2017 ◽  
Vol 12 (S330) ◽  
pp. 164-167
Author(s):  
Kohei Hattori ◽  
Naoteru Gouda ◽  
Taihei Yano ◽  
Nobuyuki Sakai ◽  
Hiromichi Tagawa
Keyword(s):  
Velocity Distribution ◽  
Test Particle ◽  
Young Stars ◽  
Local Velocity ◽  
Rich Region ◽  
Spiral Arms ◽  
Poor Region ◽  
Particle Simulations ◽  
Lindblad Resonance ◽  
Fast Rotating

AbstractNearby disc stars in Gaia DR1 (TGAS) and RAVE DR5 show a bimodal velocity distribution in the metal-rich region (characterized by the Hercules stream) and mono-modal velocity distribution in the metal-poor region. We investigate the origin of this [Fe/H] dependence of the local velocity distribution by using 2D test particle simulations. We found that this [Fe/H] dependence can be well reproduced if we assume fast rotating bar models with Ωbar ≃ 52 km s−1 kpc−1. A possible explanation for this result is that the metal-rich, relatively young stars are more likely to be affected by bar's outer Lindblad resonance due to their relatively cold kinematics. We also found that slowly rotating bar models with Ωbar ≃ 39 km s−1 kpc−1 can not reproduce the observed data. Interestingly, when we additionally consider spiral arms, some models can reproduce the observed velocity distribution even when the bar is slowly rotating.

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 Identifying resonances of the Galactic bar in Gaia DR2: I. Clues from action space

2020 ◽  
Vol 500 (2) ◽  
pp. 2645-2665
Author(s):  
Wilma H Trick ◽  
Francesca Fragkoudi ◽  
Jason A S Hunt ◽  
J Ted Mackereth ◽  
Simon D M White
Keyword(s):  
Action Space ◽  
Galactic Disc ◽  
Resonant Orbits ◽  
Particle Simulations ◽  
Pattern Speed ◽  
The Rich ◽  
First Time ◽  
Gaia Dr2 ◽  
Vertical Action ◽  
Lindblad Resonance

ABSTRACT Action space synthesizes the orbital information of stars and is well suited to analyse the rich kinematic substructure of the disc in the second Gaia data release's radial velocity sample. We revisit the strong perturbation induced in the Milky Way disc by an m = 2 bar, using test particle simulations and the actions (JR, Lz, Jz) estimated in an axisymmetric potential. These make three useful diagnostics cleanly visible. (1) We use the well-known characteristic flip from outward to inward motion at the outer Lindblad resonance (OLR; l = +1, m = 2), which occurs along the axisymmetric resonance line (ARL) in (Lz, JR), to identify in the Gaia action data three candidates for the bar’s OLR and pattern speed Ωbar: 1.85Ω0, 1.20Ω0, and 1.63Ω0 (with ∼0.1Ω0 systematic uncertainty). The Gaia data is therefore consistent with both slow and fast bar models in the literature, but disagrees with recent measurements of ∼1.45Ω0. (2) For the first time, we demonstrate that bar resonances – especially the OLR – cause a gradient in vertical action 〈Jz〉 with Lz around the ARL via ‘Jz-sorting’ of stars. This could contribute to the observed coupling of 〈vR〉 and 〈|vz|〉 in the Galactic disc. (3) We confirm prior results that the behaviour of resonant orbits is well approximated by scattering and oscillation in (Lz, JR) along a slope ΔJR/ΔLz = l/m centred on the l:m ARL. Overall, we demonstrate that axisymmetrically estimated actions are a powerful diagnostic tool even in non-axisymmetric systems.

scholarly journals The Dark Matter Content of Barred Spiral Galaxies

2004 ◽  
Vol 220 ◽  
pp. 277-278
Author(s):  
Glen Petitpas ◽  
Mousumi Das ◽  
Peter Teuben ◽  
Stuart Vogel
Keyword(s):  
Dark Matter ◽  
Spiral Galaxies ◽  
Velocity Fields ◽  
Matter Content ◽  
Two Dimensional ◽  
Disk Model ◽  
Barred Galaxies ◽  
Preliminary Results ◽  
Nearby Galaxies ◽  
Barred Spiral Galaxies

Two-dimensional velocity fields have been used to determine the dark matter properties of a sample of barred galaxies taken from the BIMA Survey of Nearby Galaxies (SONG). Preliminary results indicate that the maximal disk model is not appropriate in several galaxies in our sample, but higher resolution results will be needed to confirm this.

scholarly journals The Central Bar in M 94

1996 ◽  
Vol 171 ◽  
pp. 422-422
Author(s):  
C. Möllenhoff ◽  
M. Matthias ◽  
O.E. Gerhard
Keyword(s):  
Major Axis ◽  
Stellar Kinematics ◽  
Semi Major Axis ◽  
Ionized Gas ◽  
Model Calculations ◽  
Gas Kinematics ◽  
Closed Orbits ◽  
Total Light ◽  
Axis Length ◽  
Global And Local

Surface photometry in I, J, K of the oval disk galaxy M 94 (NGC 4736) reveal a weak central stellar bar of 0.7 kpc semi-major axis length, comprising ≈ 14% of the total light within 20″. By stellar kinematics the existence of a small spheroidal bulge with v/à ≈ 0.8 was discovered. The ionized gas (Hα) in this region shows global and local deviations from the stellar kinematics. Model calculations of closed orbits for the cold gas in the combined potential of bar, disk, and bulge predict large non-circular motions in equilibrium flow. However, these do not fit the observed gas kinematics; obviously hydrodynamical forces play a role in the central region of M 94.

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 populations across galaxy bars in the MUSE TIMER project

2020 ◽  
Vol 637 ◽  
pp. A56 ◽  
Author(s):  
Justus Neumann ◽  
Francesca Fragkoudi ◽  
Isabel Pérez ◽  
Dimitri A. Gadotti ◽  
Jesús Falcón-Barroso ◽  
...  
Keyword(s):  
Star Formation ◽  
Major Axis ◽  
Stellar Populations ◽  
Barred Galaxies ◽  
Chemical Enrichment ◽  
Spatially Resolved ◽  
Stellar Ages ◽  
Hydrodynamical Simulations ◽  
Inner Region ◽  
Star Formation Histories

Stellar populations in barred galaxies save an imprint of the influence of the bar on the host galaxy’s evolution. We present a detailed analysis of star formation histories (SFHs) and chemical enrichment of stellar populations in nine nearby barred galaxies from the TIMER project. We used integral field observations with the MUSE instrument to derive unprecedented spatially resolved maps of stellar ages, metallicities, [Mg/Fe] abundances, and SFHs, as well as Hα as a tracer of ongoing star formation. We find a characteristic V-shaped signature in the SFH that is perpendicular to the bar major axis, which supports the scenario where intermediate-age stars (∼2 − 6 Gyr) are trapped on more elongated orbits shaping a thinner part of the bar, while older stars (> 8 Gyr) are trapped on less elongated orbits shaping a rounder and thicker part of the bar. We compare our data to state-of-the-art cosmological magneto-hydrodynamical simulations of barred galaxies and show that such V-shaped SFHs arise naturally due to the dynamical influence of the bar on stellar populations with different ages and kinematic properties. Additionally, we find an excess of very young stars (< 2 Gyr) on the edges of the bars, predominantly on the leading side, thus confirming typical star formation patterns in bars. Furthermore, mass-weighted age and metallicity gradients are slightly shallower along the bar than in the disc, which is likely due to orbital mixing in the bar. Finally, we find that bars are mostly more metal-rich and less [Mg/Fe]-enhanced than the surrounding discs. We interpret this as a signature that the bar quenches star formation in the inner region of discs, usually referred to as star formation deserts. We discuss these results and their implications on two different scenarios of bar formation and evolution.

scholarly journals Formation of inner rings in 3D potentials of barred galaxies

2004 ◽  
Vol 220 ◽  
pp. 275-276
Author(s):  
Panos A. Patsis ◽  
Charalampos Skokos ◽  
E. Athanassoula
Keyword(s):  
Periodic Orbits ◽  
Major Axis ◽  
Minor Axis ◽  
Barred Galaxies ◽  
High Energies ◽  
Families Of Periodic Orbits ◽  
Two Sides ◽  
Analytic Potential

In a 3D analytic potential we find the families of periodic orbits that support the formation of inner rings. These are families at high energies, between the inner radial ultraharmonic 4:1 (iUHR) resonance and corotation, influenced by the 4:1, 6:1 and 8:1 resonances. the inner rings they support are mainly ovals and polygons with ‘corners’ on the bar minor axis, on its sides, which correspond to morphologies often seen in real galaxies like NGC 6782 and IC 4290. We also investigate the conditions under which less probable shapes of rings may be supported by orbits at the region. Such rings include pentagonal features (NGC 3367) and hexagons with cusps on the major axis of the bar and two sides parallel to it (NGC 7020).

scholarly journals Box/Peanut Galaxies in the Near-IR

1996 ◽  
Vol 157 ◽  
pp. 224-226
Author(s):  
S. M. Baggett ◽  
J. W. MacKenty
Keyword(s):  
Major Axis ◽  
Minor Axis ◽  
Disk Galaxies ◽  
Early Type ◽  
Contour Maps ◽  
Near Ir

Galaxies with box/peanut-shaped (b/p) bulges have been known for some time (e.g., NGC 128 and NGC 7332 (Sandage 1961)). Observationally, b/p features are detected in edge-on systems, and are visible in images, contour maps, and brightness profiles as isophote sections that near minor axis are relatively flat and parallel to major axis (see Figure 1). Peanut-type bulges have isophotes indented at the intersection with the minor axis.There have been several morphological surveys to date. The two most recent studies have found that about 20% of early-type galaxies and nearly 45% of all disk galaxies are b/p galaxies (see Shaw 1987, Dettmar 1989, and references therein) and that the b/p galaxy properties appear similar to normal spirals in the optical, radio, and infrared. A few kinematical studies have been done: b/p bulges are found to rotate more like disks than bulges (e.g., 150 km s−1 up to 6 kpc above the plane in NGC 128 (Jarvis 1990) and the velocities remain constant up to large z, implying cylindrical rotation (e.g., NGC 3079 has v constant out to 1.6 kpc (Shaw et al. 1993)).

STRUCTURES OUT OF CHAOS IN BARRED-SPIRAL GALAXIES

2012 ◽  
Vol 22 (09) ◽  
pp. 1230029 ◽  
Author(s):  
P. A. PATSIS
Keyword(s):  
Near Infrared ◽  
Spiral Galaxies ◽  
Morphological Features ◽  
Infrared Images ◽  
Chaotic Motions ◽  
Spiral Arms ◽  
Gravitational Fields ◽  
Pattern Speed ◽  
Barred Spiral Galaxies ◽  
Kinematical Data

We review the dynamical mechanisms we have found to support the morphological features in barred-spiral galaxies based on chaotic motions of stars in their gravitational fields. These morphological features are the spiral arms, that emerge out of the ends of the bar, but also shape the bar itself. The potentials used have been estimated directly from near-infrared images of barred-spiral galaxies. In this paper, we present the results from the study of the dynamics of the potentials of the galaxies NGC 4314, NGC 1300 and NGC 3359. The main unknown parameter in our models is the pattern speed of the system Ωp. By varying Ωp, we have investigated several cases trying to match the results of our modeling with available photometrical and kinematical data. We found realistic models with stars on spirals in chaotic motion, while their bars are built by stars usually on regular orbits. However, we also encountered cases, where a major part of trajectories of the stars even in the bar is chaotic as well. Finally, we examined the gas dynamics of barred-spiral systems, and found that the presence of gas reinforces the intensity of the "chaotic" spiral arms.

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