Weak Bar Research Articles

Destructible Bars in Disk Galaxies under the Dynamical Influence of a Massive Central Black Hole

Abstract The characteristics of the galactic bars that are prone to suffer a damaging impact from a massive central black hole are examined using flat stellar disks. We construct three disk model groups that consist of exponential disks with one type of velocity distribution and Kuzmin–Toomre disks with two different types of exact equilibrium distribution functions. For each disk model group, three disks that have different typical Toomre’s $Q$ values are evolved to form bars through dynamical instability. Once a bar is fully developed, a black hole (BH), whose mass is 1% of the disk mass, is adiabatically added at the center of the disk. Our results show that lower-amplitude bars, that is weaker bars, are dissolved more easily by that BH. We have found that this destructibility is rooted in the characteristic feature that the bar formed spontaneously becomes shorter in length and rounder in shape with decreasing bar amplitude. Since such weaker bars are found to originate from colder disks in each disk model group, it follows that for a given form of velocity structure, the coldness of an initial disk determines whether the bar produced in that disk is favorable to dissolution induced by a massive central BH. In addition, the existence of bar-dissolved galaxies of the kind studied here is also discussed.

DEPENDENCE OF BARRED GALAXY FRACTION ON GALAXY PROPERTIES AND ENVIRONMENT

We investigate the dependence of occurrence of bars in galaxies on galaxy properties and environment. We use a volume-limited sample of 33,391 galaxies brighter than $M_{r}=-19.5+5$log$h$ at $0.02\le z\le0.05489$, drawn from the SDSS DR 7. We classify the galaxies into early and late types, and identify bars by visual inspection. Among 10,674 late-type galaxies with axis ratio $b/a>0.60$, we find 3,240 barred galaxies ($f_{bar}=30.4%$) which divide into 2,542 strong bars ($f_{SB1}=23.8%$) and 698 weak bars ($f_{SB2}=6.5%$). We find that $f_{SB1}$ increases as $u-r$ color becomes redder, and that it has a maximum value at intermediate velocity dispersion ($\sigma\simeq$150 km s$^{-1}$). This trend suggests that strong bars are dominantly hosted by intermediate-mass systems. Weak bars prefer bluer galaxies with lower mass and lower concentration. In the case of strong bars, their dependence on the concentration index appears only for massive galaxies with $\sigma>150$ km s$^{-1}$. We also find that $f_{bar}$ does not directly depend on the large-scale background density when other physical parameters ($u-r$ color or $\sigma$) are fixed. We discover that $f_{SB1}$ decreases as the separation to the nearest neighbor galaxy becomes smaller than 0.1 times the virial radius of the neighbor regardless of neighbor's morphology. These results imply that strong bars are likely to be destroyed during strong tidal interactions, and that the mechanism for this phenomenon is gravitational and not hydrodynamical. The fraction of weak bars has no correlation with environmental parameters. We do not find any direct evidence for environmental stimulation of bar formation.

TESTING THEORIES IN BARRED-SPIRAL GALAXIES

According to one version of the recently proposed "manifold" theory that explains the origin of spirals and rings in relation to chaotic orbits, galaxies with stronger bars should have a higher spiral arms pitch angle when compared to galaxies with weaker bars. A sub-sample of barred-spiral galaxies in the Ohio State University Bright Galaxy Survey, was used to analyze the spiral arms pitch angle. These were compared with bar strengths taken from the literature. It was found that the galaxies in which the spiral arms maintain a logarithmic shape for more than 70$\degr$ seem to corroborate the predicted trend.

Molecular gas in the inner 0.7 kpc-radius ring of M 31

The study of the gas kinematic in the central 1.5kpc x 1.5kpc region of M31 has revealed several surprises. The starting point of this investigation was the detection at the IRAM-30m telescope of molecular gas with very large line splittings up to 260km/s within the beam (40 pc). In this region, which is known for its low gas content, we also detect an ionised gas outflow in the circumnuclear region (within 75pc from the centre) extending to the whole area in X-ray. Relying on atomic, ionised, and molecular gas, we account for most observables with a scenario that assumes that a few hundreds Myr ago, M31 underwent a frontal collision with M32, which triggered some star-formation activity in the centre, and this collision explains the special configuration of M31 with two rings observed at 0.7kpc and 10kpc. The inner disc (whose rotation is detected in HI and ionised gas ([NII])) has thus been tilted (inclination: 43deg, PA: 70deg) with respect to the main disc (inclination: 77deg, PA: 35deg). One of the CO velocity components is compatible with this inner disc, while the second one comes from a tilted ring-like material with 40deg inclination and PA=-35deg. The relic star formation estimated by previous works to have occurred more than 100Myr ago could have been triggered by the collision and could be linked to the outflow detected in the ionised gas. Last, we demonstrate that the amplitude of the line splittings detected in CO centred on the systemic velocity with a relatively high spatial resolution (40pc) cannot be accounted for by a possible weak bar that is roughly aligned along the minor axis. Although M31 has a triaxial bulge, there are no bar indicators in the gas component (photometry, no strong skewness of the isovelocities, etc.).

NUCLEAR RINGS IN GALAXIES—A KINEMATIC PERSPECTIVE

We combine DensePak integral field unit and TAURUS Fabry-Perot observations of 13 nuclear rings to show an interconnection between the kinematic properties of the rings and their resonant origin. The nuclear rings have regular and symmetric kinematics, and lack strong non-circular motions. This symmetry, coupled with a direct relationship between the position angles and ellipticities of the rings and those of their host galaxies, indicate the rings are in the same plane as the disc and are circular. From the rotation curves derived, we have estimated the compactness (v^2/r) up to the turnover radius, which is where the nuclear rings reside. We find that there is evidence of a correlation between compactness and ring width and size. Radially wide rings are less compact, and thus have lower mass concentration. The compactness increases as the ring width decreases. We also find that the nuclear ring size is dependent on the bar strength, with weaker bars allowing rings of any size to form.

DECREASED FREQUENCY OF STRONG BARS IN S0 GALAXIES: EVIDENCE FOR SECULAR EVOLUTION?

Using data from the Near-Infrared S0 Survey (NIRS0S) of nearby, early-type galaxies, we examine the distribution of bar strengths in S0 galaxies as compared to S0/a and Sa galaxies, and as compared to previously published bar strength data for Ohio State University Bright Spiral Galaxy Survey (OSUBSGS) spiral galaxies. Bar strengths based on the gravitational torque method are derived from 2.2 micron Ks-band images for a statistical sample of 138 (98 S0, 40 S0/a,Sa) galaxies having a mean total blue magnitude <B_T> <= 12.5 and generally inclined less than 65 degrees. We find that S0 galaxies have weaker bars on average than spiral galaxies in general, even compared to their closest spiral counterparts, S0/a and Sa galaxies. The differences are significant and cannot be due entirely to uncertainties in the assumed vertical scale-heights or in the assumption of constant mass-to-light ratios. Part of the difference is likely due simply to the dilution of the bar torques by the higher mass bulges seen in S0s. If spiral galaxies accrete external gas, as advocated by Bournaud & Combes, then the fewer strong bars found among S0s imply a lack of gas accretion according to this theory. If S0s are stripped former spirals, or else are evolved from former spirals due to internal secular dynamical processes which deplete the gas as well as grow the bulges, then the weaker bars and the prevalence of lenses in S0 galaxies could further indicate that bar evolution continues to proceed during and even after gas depletion

On very weak solutions of semi-linear elliptic equations in the framework of weighted spaces with respect to the distance to the boundary

We prove the existence of an appropriate function (very weaksolution) $u$ in the Lorentz space $L^{N',\infty}(\Omega), \N'=\frac N{N-1}$ satisfying $Lu-Vu+g(x,u,\nabla u)=\mu$in $\Omega$ an open bounded set of $\R^N$, and $u=0$ on$\partial\Omega$ in the sense that$(u,L\varphi)_0-(Vu,\varphi)_0+(g(\cdot,u,\nablau),\varphi)_0=\mu(\varphi),\quad\forall\varphi\in C^2_c(\Omega).$The potential $V \le \lambda If $\mu\in L^1(\Omega,\delta)$ we only assume that for the potential $V$ is in L1loc$(\Omega)$, $V \le \lambda<\lambda_1$. If $\mu\in M^1(\Omega,\delta^\alpha),\ \alpha\in$[$0,1[$[, then we prove that the very weak solution $|\nabla u|$ is in the Lorentz space $L^{\frac N{N-1+\alpha},\infty}(\Omega)$. We apply those results to the existence of the so called large solutions with a right hand side data in $L^1(\Omega,\delta)$. Finally, we prove some rearrangement comparison results.

Decidability and Specker sequences in intuitionistic mathematics

AbstractA bounded monotone sequence of reals without a limit is called a Specker sequence. In Russian constructive analysis, Church's Thesis permits the existence of a Specker sequence. In intuitionistic mathematics, Brouwer's Continuity Principle implies it is false that every bounded monotone sequence of real numbers has a limit. We claim that the existence of Specker sequences crucially depends on the properties of intuitionistic decidable sets. We propose a schema (which we call ED) about intuitionistic decidability that asserts “there exists an intuitionistic enumerable set that is not intuitionistic decidable” and show that the existence of a Specker sequence is equivalent to ED. We show that ED is consistent with some certain well known axioms of intuitionistic analysis as Weak Continuity Principle, bar induction, and Kripke Schema. Thus, the assumption of the existence of a Specker sequence is conceivable in intuitionistic analysis. We will also introduce the notion of double Specker sequence and study the existence of them (© 2009 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

The morphology of galactic rings exterior to evolving bars: test-particle simulations

The morphology of the outer rings of early-type spiral galaxies is compared to integrations of massless collisionless particles initially in nearly circular orbits. Particles are perturbed by a quadrupolar gravitational potential corresponding to a growing and secularly evolving bar. We find that outer rings with R1R2 morphology and pseudo-rings are exhibited by the simulations even though they lack gaseous dissipation. Simulations with stronger bars form pseudo-rings earlier and more quickly than those with weaker bars. We find that the Rl ring, perpendicular to the bar, is fragile and dissolves after a few bar rotation periods if the bar pattern speed increases by more than ∼8 per cent, bar strength increases (by ≥140 per cent) after bar growth or the bar is too strong (Q T > 0.3). If the bar slows down after formation, pseudo-ring morphology persists and the R2 ring perpendicular to the bar is populated due to resonance capture. The R2 ring remains misaligned with the bar and increases in ellipticity as the bar slows down. The R2 ring becomes scalloped and does not resemble any ringed galaxies if the bar slows down more than 3.5 per cent suggesting that bars decrease in strength before they slow down this much. We compare the morphology of our simulations to B-band images of nine ringed galaxies from the Ohio State University Bright Spiral Galaxy Survey, and we find a reasonable match in morphologies to R1R2' pseudo-rings seen within a few bar rotation periods of bar formation. Some of the features previously interpreted in terms of dissipative models may be due to transient structure associated with recent bar growth and evolution.

Molecular gas in NUclei of GAlaxies (NUGA)

We present CO(1-0) and CO(2-1) observations of the SA(rs)bc Seyfert 2 galaxy NGC 3147, obtained with the IRAM interferometer at 1\farcs9 $\times$1\farcs6 and 1\farcs6 $\times$1\farcs4 resolutions, respectively. A central peak seen mainly in CO(2-1) and a ring-like structure at $r \simeq 10$\arcsec $\sim$2 kpc dominate the CO maps. In CO(1-0) an outer spiral at $r \simeq 20$\arcsec $\sim$4 kpc is also detected, not visible in CO(2-1) emission because it falls outside the field-of-view of the primary beam. The kinematics of the molecular structures are quite regular, although there is evidence for local non-circular or streaming motions. We show that the molecular gas distribution is similar but not exactly identical to those of star formation tracers. Using a NIR image obtained with adaptive optics at the CFHT Telescope, we identify a weak bar in NGC 3147, which is classified as non-barred galaxy in the optical. We then compute the gravity torques exerted by this stellar bar on the gas. We find that the gas inside the inner CO ring is subject to a net negative torque and loses angular momentum. This is expected for gas at the UHR, just inside the corotation resonance of the stellar bar. In contrast, the gas outside corotation, in the spiral arms comprising the outer spiral structure, suffers positive torques and is driven outwards. We conclude that some molecular gas is presently flowing into the central region, since we find negative torques down to the resolution limit of our images.

Filling-In and Suppression of Visual Perception from Context: A Bayesian Account of Perceptual Biases by Contextual Influences

Visual object recognition and sensitivity to image features are largely influenced by contextual inputs. We study influences by contextual bars on the bias to perceive or infer the presence of a target bar, rather than on the sensitivity to image features. Human observers judged from a briefly presented stimulus whether a target bar of a known orientation and shape is present at the center of a display, given a weak or missing input contrast at the target location with or without a context of other bars. Observers are more likely to perceive a target when the context has a weaker rather than stronger contrast. When the context can perceptually group well with the would-be target, weak contrast contextual bars bias the observers to perceive a target relative to the condition without contexts, as if to fill in the target. Meanwhile, high-contrast contextual bars, regardless of whether they group well with the target, bias the observers to perceive no target. A Bayesian model of visual inference is shown to account for the data well, illustrating that the context influences the perception in two ways: (1) biasing observers' prior belief that a target should be present according to visual grouping principles, and (2) biasing observers' internal model of the likely input contrasts caused by a target bar. According to this model, our data suggest that the context does not influence the perceived target contrast despite its influence on the bias to perceive the target's presence, thereby suggesting that cortical areas beyond the primary visual cortex are responsible for the visual inferences.

Bar Imprints on the Inner Gas Kinematics of M33

We present measurements of the stellar and gaseous velocities in the central 5' of the Local Group spiral M33. The data were obtained with the ARC 3.5 m telescope. Blue and red spectra with resolutions from 2 to 4 Å covering the principal gaseous emission and stellar absorption lines were obtained along the major and minor axes and six other position angles. The observed radial velocities of the ionized gas along the photometric major axis of M33 remain flat at 22 km s-1 all the way into the center, while the stellar velocities show a gradual rise from 0 to 22 km s -1 over that same region. The central star cluster is at or very close to the dynamical center, with a velocity that is in accordance with M33's systemic velocity to within our uncertainties. Velocities on the minor axis are nonzero out to about 1' from the center in both the stars and gas. Together with the major-axis velocities, they point at significant deviations from circular rotation. The most likely explanation for the bulk of the velocity patterns are streaming motions along a weak inner bar with a position angle close to that of the minor axis, as suggested by previously published IR photometric images. The presence of bar imprints in M33 implies that all major Local Group galaxies are barred. The noncircular motions over the inner 200 pc make it difficult to constrain the shape of M33's inner dark matter halo profile. If the noncircular motions we find in this nearby Sc galaxy are present in other more distant late-type galaxies, they might be difficult to recognize.

Cross‐shore sediment transport on natural beaches and its relation to sandbar migration patterns: 2. Application of the field transport parameterization

A cross‐shore sediment transport parameterization (shape function) based on data from intensive field experiments carried out on five European beaches is incorporated into a simple time dependent model to explore its capability for reproducing sandbar generation and evolution in the medium term (O(months)). Model results are compared with bar‐crest migration patterns observed at Duck, North Carolina. The model comprises a simple wave transformation routine that accounts for linear shoaling and assumes a saturation law for wave decay inside the surf zone. Second‐order statistics derived from the cross‐shore distribution of wave heights are used to scale the sediment transport parameterizations which estimate the cross‐shore structure of the third and fourth velocity moments. Cross‐shore gradients in sediment fluxes, calculated with an energetics approach, produce bed elevation changes. The updated morphology affects the wave propagation in the next time step forming a fully coupled model for predicting sandbar evolution. Bar generation close to shore and the details of the sandbar evolution are successfully reproduced (R2 = 0.86) over the 77‐day period of the observations using default values for drag coefficients and efficiency factors. In accordance with the observations, the model shows rapid offshore sandbar migration in response to individual storms, and weak onshore bar movement for lower energy conditions. Owing to its simple nature, the model is not capable of reproducing the whole profile morphology especially in the trough (no trough generation), and it is only valid for replicating bar crest position. The results suggest that a convergence of sediment near the breakpoint (breakpoint hypothesis) combined with morphological feedback, can successfully explain the evolution of bar crest over periods of months from the details of forcing (incident waves and water levels).

The bar-halo interaction - II. Secular evolution and the religion of N-body simulations

This paper explores resonance-driven secular evolution between a bar and dark-matter halo using N-body simulations. We make direct comparisons to our analytic theory (Weinberg & Katz 2005) to demonstrate the great difficulty that an N-body simulation has representing these dynamics for realistic astronomical interactions. In a dark-matter halo, the bar's angular momentum is coupled to the central density cusp (if present) by the Inner Lindblad Resonance. Owing to this angular momentum transfer and self-consistent re-equilibration, strong realistic bars WILL modify the cusp profile, lowering the central densities within about 30% of the bar radius in a few bar orbits. Past results to the contrary (Sellwood 2006, McMillan & Dehnen 2005) may be the result of weak bars or numerical artifacts. The magnitude depends on many factors and we illustrate the sensitivity of the response to the dark-matter profile, the bar shape and mass, and the galaxy's evolutionary history. For example, if the bar length is comparable to the size of a central dark-matter core, the bar may exchange angular momentum without changing its pattern speed significantly. We emphasise that this apparently simple example of secular evolution is remarkably subtle in detail and conclude that an N-body exploration of any astronomical scenario requires a deep investigation into the underlying dynamical mechanisms for that particular problem to set the necessary requirements for the simulation parameters and method (e.g. particle number and Poisson solver). Simply put, N-body simulations do not divinely reveal truth and hence their results are not infallible. They are unlikely to provide useful insight on their own, particularly for the study of even more complex secular processes such as the production of pseudo-bulges and disk heating.

The Connection between Bar Strength and Circumnuclear Dust Structure

We present a comparison of barstrength Qb and circumnuclear dust morphology for 75 galaxies in order to investigate how bars affect the centers of galaxies. We trace the circumnuclear dust morphology and amount of dust structure with structure maps generated from visible-wavelength HST data, finding that tightly wound nuclear dust spirals are primarily found in weakly barred galaxies. While strongly barred galaxies sometimes exhibit grand design structure within the central 10 percent of D25, this structure rarely extends to within ~10 pc of the galaxy nucleus. In some galaxies, these spiral arms terminate at a circumnuclear starburst ring. Galaxies with circumnuclear rings are generally more strongly barred than galaxies lacking rings. Within these rings, the dust structure is fairly smooth and usually in the form of a loosely wound spiral. These data demonstrate that multiple nuclear morphologies are possible in the most strongly barred galaxies: chaotic central dust structure inconsistent with a coherent nuclear spiral, a grand design spiral that loses coherence before reaching the nucleus, or a grand design spiral that ends in a circumnuclear ring. These observations may indicate that not all strong bars are equally efficient at fueling material to the centers of their host galaxies. Finally, we investigate the longstanding hypothesis that SB(s) galaxies have weak bars and SB(r) galaxies have strong bars, finding the opposite to be the case: namely, SB(r) galaxies are less strongly barred and have less dust structure than SB(s) galaxies. In general, more strongly barred galaxies tend to have higher nuclear dust contrast.

A new species of the Bokermannohyla circumdata group (Amphibia: Anura: Hylidae) from Chapada Diamantina, State of Bahia, Brazil

A new species of the Bokermannohyla circumdata group, B. diamantina sp. nov., is described from Serra dos Barbados, Municipality of Abaíra, State of Bahia, Brazil. This locality belongs to Chapada Diamantina, a semiarid region in central Bahia. This is the first record of a species of the B. circumdata group from the Brazilian semiarid. Bokermannohyla diamantina is diagnosed by the medium size (snout-vent length 47.0–51.7 mm in adult specimens); head length 2.8–2.9 times smaller than snout-vent length; tympanum medium-sized, its diameter 1.3–1.5 times smaller than eye diameter (tympanum diameter/snout-vent length 0.07); thigh and tibia lengths 0.48–0.52 and 0.49–0.51 of snout-vent length, respectively; dorsum medium to blackish brown, with weak transverse dark brown bars; flanks, anterior, and posterior surfaces of thighs with dark transverse brown stripes, lacking additional thin stripes between them; distinct vocal slits in adult males; advertisement call with 2–4 notes, and dominant frequency from 0.39–0.56 kHz.

The influence of numerical parameters on tidally triggered bar formation

The joint influence of numerical parameters such as the number of particles N, the gravitational softening length $\epsilon$ and the time-step $\Delta t$ is investigated in the context of galaxy simulations. For isolated galaxy models we have performed a convergence study and estimated the numerical parameters ranges for which the relaxed models do not deviate significantly from its initial configuration. By fixing N, we calculate the range of the mean interparticle separation $\lambda(r)$ along the disc radius. We have found that in the simulations with N=1310720 particles $\lambda$ varies by a factor of 6, and the corresponding final Toomre's parameters Q change by only about 5 per cent. By decreasing N, the $\lambda$ and Q ranges broaden. Large $\epsilon$ and small N cause an earlier bar formation. For a given set of parameters the disc heating is smaller with the Plummer softening than with the spline softening. For galaxy collision models numerical simulations indicate that the properties of the formed bars strongly depend upon the selection of N and $\epsilon$. Large values of the gravitational softening parameter and a small number of particles results in the rapid formation of a well defined, slowly rotating bar. On the other hand, small values of $\epsilon$ produce a small, rapidly rotating disc with tightly wound spiral arms, and subsequently a weak bar emerges. We have found that by increasing N, the bar properties converge and the effect of the softening parameter diminishes. Finally, in some cases short spiral arms are observed at the ends of the bar that change periodically from trailing to leading and vice-versa - the wiggle.

Bar instability in cosmological halos

Context. Aims.We investigate the growth of bar instability in stellar disks embedded in a dark matter halo evolving in a fully consistent cosmological framework. Methods.We perform seven cosmological simulations to emphasise the role of both the disk-to-halo mass ratio and of the Toomre parameter, Q, on the evolution of the disk.We also compare our fully cosmological cases with corresponding isolated simulations where the same halo is extracted from the cosmological scenario and evolved in physical coordinates. Results.A long living bar, lasting about 10 Gyr, appears in all our simulations. In particular, disks expected to be stable according to classical criteria form weak bars. We argue that such a result is due to the dynamical properties of our cosmological halo which is far from stability and isotropy, typical of the classical halos used in the literature; it is dynamically active, has substructures and undergoes infall. Conclusions.At least for mild self-gravitating disks, the study of the bar instability using isolated isotropic halos in gravitational equilibrium can lead to misleading results. Furthermore, the cosmological framework is needed to quantitatively investigate such an instability.

Morphology of 15 Southern Early?Type Disk Galaxies

Structural analysis has been performed for a sample of 15 southern early-type disk galaxies, mainly S0 galaxies, using high-resolution Ks-band images. The galaxies are mostly barred, and many of them show multiple structures including bars and ovals, typical for S0 galaxies. The new images are of sufficient quality to reveal new detail of the morphology of the galaxies. For example, we report a hitherto undetected nuclear ring in NGC 1387, a nuclear bar in NGC 1326, and in the residual image a weak primary bar in NGC 1317. For the galaxies we (1) measure the radial profiles of the orientation parameters derived from the elliptical isophotes, (2) apply Fourier methods for calculating tangential forces, and, in particular, (3) apply structural decomposition methods. For galaxies with multiple structures a two-dimensional method is found to be superior to a one-dimensional method but only if in addition to the bulge and the disk at least one other component is taken into account. We find strong evidence of pseudobulges in S0 galaxies: 10 of the galaxies have a shape parameter of the bulge near n = 2, indicating that the bulges are more disklike than following the R1/4 law. Also, six of the galaxies have either nuclear rings, nuclear bars, or nuclear disks. In all nonelliptical galaxies in our sample the bulge-to-total (B/T) flux ratio is less than 0.4, as is typically found in galaxies having pseudobulges. In two of the galaxies the B/T flux ratio is as small as in typical Sc-type spiral galaxies. This might be the hitherto undiscovered link in the scenario in which spiral galaxies are transformed into S0 galaxies. Also, bars in S0 systems are found to be shorter and less massive and to have smaller bar torques than bars in S0/a-type galaxies.

Virgo High-Resolution CO Survey: V. Circumnuclear Elliptical Ring in NGC 4569

Abstract We present high-resolution (${1\rlap {.}{}^{\mathrm {\prime \prime }}8}$–${4\rlap {.}{}^{\mathrm {\prime \prime }}5}$) CO data of the Virgo spiral galaxy NGC 4569, obtained using the Nobeyama Millimeter Array. We found that the molecular gas is highly concentrated in the circumnuclear region with two off-center peaks. A CO image with the highest angular resolution of $ {2\rlap {.}{}^{\mathrm {\prime \prime }}0} \times {1\rlap {.}{}^{\mathrm {\prime \prime }}8}$ shows that six blobs likely form a circumnuclear elliptical ring (CER) with a semimajor axis of 720 pc. The CER shows a strongly twisted velocity field, and the Position–velocity diagram shows significant forbidden velocity components. These kinetic features are understood as being non-circular motion due to a bar-potential. We found that the CER coincides with the $\mathrm{H}\alpha$ bright central core and that the mass ratio of the molecular gas to the dynamical mass is about 18%. These results support a gaseous inflow scenario induced by a weak bar potential and self-gravity of the gas.