We present some preliminary results from new Chandra and XMM-Newton X-ray observations of the nearby barred spiral galaxy NGC1672. It shows dramatic nuclear and extra-nuclear star formation activity, including starburst regions located near each end of its strong bar, both of which host ultraluminous X-ray sources (ULXs). With the new high-spatial-resolution Chandra imaging, we show for the first time that NGC1672 possesses a faint ($L(X)~10^39 erg/s), hard central X-ray source surrounded by an X-ray bright circumnuclear starburst ring that dominates the X-ray emission in the region. The central source may represent low-level AGN activity, or alternatively the emission from X-ray binaries associated with star-formation in the nucleus.
We consider a scenario of formation of the spiral structure in barred galaxies. This scenario includes the new non-resonant mechanism of elongation of spirals, due to the characteristic behaviour of the gravitational potential beyond the principal spiral arms.
We have conducted near-infrared (J- and H-band) surface photometry for two early type barred galaxies, NGC 3412 and NGC 3941. The bulges of NGC 3412 and NGC 3941 show isophotal twists which indicate that they are triaxial. NGC 3412 has a very short bar and its bulge is more centrally concentrated than that of NGC 3941. The unusually short bar and the centrally concentrated triaxial bulge of NGC 3412 might be the result of bar dissolution. The colors of the nuclear region of NGC 3941 resemble those of the blue nuclei, implying the presence of young stellar populations.
The data from a CO(1 - 0) mapping survey of 40 nearby spiral galaxies performed with the Nobeyama 45-m telescope are presented. The criteria of the sample selection were (1) RC3 morphological type in the range Sa to Scd, (2) distance less than 25 Mpc, (3) inclination angle less than 79deg (RC3), (4) flux at 100 um higher than ~ 10 Jy, (5) spiral structure is not destroyed by interaction. The maps of CO cover most of the optical disk of the galaxies. We investigated the influence of bar on the distribution of molecular gas in spiral galaxies using these data. We confirmed that the degree of cen…
We have performed for the first time in the literature a 2D structural analysis on the barred lenticular and face--on galaxies NGC 4608 and NGC 5701. The results indicate that these galaxies either have never had large disks or their disks were almost completely destroyed by their strong bars, due to secular evolution processes. We discuss these surprising conclusions checking for signs of secular evolution, considering bar forming instabilities, and suggesting, based on N-body simulations, a new mechanism to form bars in spheroids, which includes non-spherical halos. Quantitative predictions …
We have conducted a $UBVRI$ and $H_α$ CCD photometry of 5 barred galaxies, NGC 2523, NGC 2950, NGC 3412, NGC 3945 and NGC 5383, along with SPH simulations, in order to understand the origin of young stellar populations in the nuclei of barred galaxies. The $H_α$ emissions which are thought to be emitted by young stellar populations are either absent or strongly concentrated on the nuclei of early type galaxies (NGC 2950, NGC 3412, NGC 3945), while they are observed in the nuclei and circumnuclear regions of intermediate type galaxies with strong bars (NGC 2523, NGC 5383). SPH simulations of re…
An objective prism H alpha survey has shown that there is a population of early type spiral galaxies in nearby clusters with strong central bursts of star formation which could be due to galaxy--galaxy tidal interactions. Such galaxies are rarely found in the field.
A study of the distribution of barred and nonbarred disk galaxies in the Virgo cluster is presented in an attempt to use the frequency and spatial distribution of galaxies with specific morphological features to study the efficiency of various environmental effects on the evolution of disk galaxies in clusters. The velocity distribution of the barred spirals in the Virgo region is clearly different than that of the nonbarred spirals, suggesting that barred spirals are more common in the main condensation of the cluster. A sample cleansed of galaxies not belonging to the main cluster condensati…
We characterize the stellar populations in the nuclear region of the barred spiral galaxy NGC 4900 using the integral field spectrometer OASIS and the synthesis code LavalSB and the code from Mollá & Garc\'ıa-Vargas (2000) for the young ($< 10$ Myr) and the old stellar populations, respectively. The high spatial resolution of the instrument allows us to find an old population uniformely distributed and younger regions located at the end of the galaxy bar and on each side of a nuclear bar.
The unstable invariant manifolds of the short-period family of periodic orbits around the unstable Lagrangian points $L_1$ and $L_2$ of a barred galaxy define loci in the configuration space which take the form of a trailing spiral pattern. In the present paper we investigate this association in the case of the self-consistent models of Kaufmann & Contopoulos (1996) which provide an approximation of real barred-spiral galaxies. We also examine the relation of `response' models of barred-spiral galaxies with the theory of the invariant manifolds. Our main results are the following: The invarian…
We present sensitive, high angular resolution (6" x 5") 21-cm observations of the neutral hydrogen in the nearby barred Seyfert galaxy, NGC4151. These HI observations, obtained using the VLA in B-configuration, are the highest resolution to date of this galaxy, and reveal hitherto unprecedented detail in the distribution and kinematics of the HI on sub-kiloparsec scales. A complete analysis and discussion of the HI data are presented and the global properties of the galaxy are related to the bar dynamics presented in Paper I.
We propose a theory to explain the formation of both spirals and rings in barred galaxies using a common dynamical framework. It is based on the orbital motion driven by the unstable equilibrium points of the rotating bar potential. Thus, spirals, rings and pseudo-rings are related to the invariant manifolds associated to the periodic orbits around these equilibrium points. We examine the parameter space of three barred galaxy models and discuss the formation of the different morphological structures according to the properties of the bar model. We also study the influence of the shape of the …
The frequency of barred spiral galaxies as a function of redshift contains important information on the gravitational influence of stellar disks in their dark matter halos and also may distinguish between contemporary theories for the origin of galactic bulges. In this paper we present a new quantitative method for determining the strength of barred spiral structure, and verify its robustness to redshift-dependent effects. By combining galaxy samples from the Hubble Deep Field North with newly available data from the Hubble Deep Field South, we are able to define a statistical sample of 18 obj…
We show observations obtained with the integral field spectrometer OASIS for the central regions of a sample of barred galaxies. The high spatial resolution of the instrument allows to distinguish various structures within these regions as defined by stellar populations of different ages and metallicities. From these data we obtain important clues about the star formation history. But we advise that, in order to obtain adequately the evolutionary sequence, a combination of chemical and synthesis models may be necessary.
The central region of the barred spiral galaxy M83 reveals a polar-nucleus dust lane, wh ich extends from the NE molecular bar and crosses the central bulge. Its SW counterpart is not visible, being hidden behind the bulge. This asymmetry, in spite of the galaxy's face-on orientation and the symmetric bar struct ure in the CO-line emission, indicates that the dark lane is an off-plane structure. Such a ``polar-nucleus'' structure can be formed by a non-coplanar, three-dimensional acc retion in a warped disk.
New CO(1-0) and CO(2-1) profiles complemented by data from the literature are used to obtain CO linewidths for 29 barred spiral galaxies with young nuclear starbursts. The ages of the starbursts were estimated from optical spectroscopy and recent evolutionary synthesis models. The CO linewidths and the starburst ages are correlated : galaxies with young (4-6 Myr) starbursts display narrow (< 100 km/s) CO line while those with older starbursts show broader CO lines. We discuss several scenarios of the gas dynamics during the nuclear starbursts' evolution to interpret the correlation.
We study the molecular gas properties in the central kiloparsec of 29 barred and 15 unbarred spirals from the BIMA Survey of Nearby Galaxies (SONG). We find that the mean nuclear molecular gas surface density of barred spirals (<Sigma_{nuc}>=309 +/- 71 Msun pc^{-2}) is three times higher than that of unbarred spirals (<Sigma_{nuc}>=107 +/- 29 Msun pc^{-2}). Nine out of the eleven bars with Sigma_{nuc} > 300 Msun pc^{-2} are early types. Comparison with estimates of the star formation threshold density (Sigma_{crit}) indicates that enhanced star formation in bars may be due to a larger fraction…
We report observations at mid-infrared and sub-millimeter wavelengths of Centaurus A (CenA, NGC 5128), the giant elliptical galaxy that harbors the closest radio loud Active Galactic Nucleus (AGN) to Earth. The dust emission from the deep interior of CenA reveals a bisymmetric structure with a diameter of 5' (5 kpc), centred at the AGN. This structure is remarkably similar to that of a barred spiral galaxy, with the bar lying in a plane that is tilted ~18 degrees from the line of sight. The true nature of the distribution of dust in the inner regions of CenA is noticeably displaced from the mo…
We present surface photometry and stellar kinematics of NGC 2950, which is a nearby and undisturbed SB0 galaxy hosting two nested stellar bars. We use the Tremaine-Weinberg method to measure the pattern speed of the primary bar. This also permits us to establish directly and for the first time that the two nested bars are rotating with different pattern speeds, and in particular that the rotation frequency of the secondary bar is higher than that of the primary one.
We propose a new theory to explain the formation of spiral arms and of all types of outer rings in barred galaxies. We have extended and applied the technique used in celestial mechanics to compute transfer orbits. Thus, our theory is based on the chaotic orbital motion driven by the invariant manifolds associated to the periodic orbits around the hyperbolic equilibrium points. In particular, spiral arms and outer rings are related to the presence of heteroclinic or homoclinic orbits. Thus, R1 rings are associated to the presence of heteroclinic orbits, while R1R2 rings are associated to the p…
We report the discovery of emission from Wolf-Rayet stars in a giant HII region 4.5 arcsec South of the nucleus of the IRAS barred spiral galaxy Mrk 712. The ratio of WNL to OV stars, estimated from the luminosity of the HeII 4686 line, is 0.2. By comparison with starburst and stellar evolution models, we find that this high value is only compatible with a very young starburst episode (3 - 4 Myr) and a flat initial mass function (Gamma = -1). The presence of the [ArV] line reveals that the HII region is strongly ionized by the hot Wolf-Rayet stars. The comparison with other barred Wolf-Rayet g…
Emission-line optical spectrophotometry for 55 H II regions in the prominent southern barred spiral galaxy NGC 1365 is presented. Nebular diagnostic diagrams such as [N II]/[O II] and [S II]/[O II] versus [O II]/{O III] show that the H II regions of the barred galaxy have the same range of physical conditions as found in non-barred late-type galaxies. Extinction is moderately high across the disc and there is evidence for a slight trend of extinction with galactocentric distance; the logarithmic extinction at H-beta falls from about c = 1.2 in the centre to 0.6 -- 0.8 in the outer regions. The…
A re-analysis of the radio continuum emission from circumnuclear regions of the barred galaxies NGC 1022, 1326 & 4314 is presented. The spatial distributions of Halpha and radio continuum are similar and suggest the existence of several giant HII regions in the circumnuclear zone. The spectral indices of the HII regions, obtained with similar angular resolution and at three different wavelengths, indicate that in all three galaxies, the spectral index, alpha^6_2 >-0.1. This result suggests the existence of giant HII regions with decreasing density gradients. The average density stratifications…
In this and in a previous paper (Romero-Gomez et al. 2006) we propose a theory to explain the formation of both spirals and rings in barred galaxies using a common dynamical framework. It is based on the orbital motion driven by the unstable equilibrium points of the rotating bar potential. Thus, spirals, rings and pseudo-rings are related to the invariant manifolds associated to the periodic orbits around these equilibrium points. We examine the parameter space of three barred galaxy models and discuss the formation of the different morphological structures according to the properties of the …
We propose a theory to explain the formation of spiral arms and of all types of outer rings in barred galaxies, extending and applying the technique used in celestial mechanics to compute transfer orbits. Thus, our theory is based on the chaotic orbital motion driven by the invariant manifolds associated to the periodic orbits around the hyperbolic equilibrium points. In particular, spiral arms and outer rings are related to the presence of heteroclinic or homoclinic orbits. Thus, R1 rings are associated to the presence of heteroclinic orbits, while R1R2 rings are associated to the presence of…
We have made observations of the \ion{H}{1} in the southern ringed barred spiral galaxies NGC~1433 and NGC~6300 with the Australia Telescope Compact Array (ATCA), the main goal being to test the resonance theory for the origin of these rings. NGC~1433 is the prototypical ringed barred spiral, and displays distinct \ion{H}{1}~counterparts to its nuclear ring, inner ring, outer pseudoring, and plume-like features. The $L_{4}$ and $L_{5}$ regions at corotation, as well as the bar itself, are relatively devoid of neutral atomic hydrogen. By associating the inner ring of NGC~1433 with the inner sec…
HI observations with the VLA of the late-type barred galaxy NGC 925 show clear streaming motions along four spiral arms close to the minor axis. A transition from inward streaming to outward streaming is found, presumably marking the corotation resonance. The realm of inward streaming extends to very large radii, corresponding to 1.3R25 and 1.7 bar radii deprojected. This implies that most of the visible disk is inside corotation, although the HI disk extends beyond, at least to 2R25. As a result, either the bar and the spirals are rotating separately or the bar rotates very slowly compared to…
We report the radio continuum structure of the barred galaxy NGC 3367 with an angular resolution of 4''.5. The radio structure indicates emission from the disk and from a triple source consisting of the nucleus straddled by extended sources (the lobes). The triple source shows an excess of radio continuum emission compared to the emission expected from the total radio - Halpha correlation, suggesting a non-thermal origin probably related to AGN activity and no to star formation processes. The triple source is about 12 kpc in diameter at a P.A. 40, close (but not aligned) to that of the stellar…
We report the gross properties of the velocity field of the barred spiral galaxy NGC 3367. The following values were found: inclination with respect to the plane of the sky, i=30 deg; position angle (PA) of receding semi major axis PA=51 and systemic velocity V(sys)=3032 km/s. Large velocity dispersion are observed of upt o 120 km/s in the nuclear region, of up to 70 km/s near the eastern bright sources just beyond the edge of the stellar bar where three spiral arms seem to start and in the western bright sources at about 10 kpc. Deviations from normal circular velocities are observed from all…
We have determined the fraction of barred galaxies in the H-band for a statistically well-defined sample of 186 spirals drawn from the Ohio State University Bright Spiral Galaxy survey. We find 56% of our sample to be strongly barred at H, while another 16% is weakly barred. Only 27% of our sample is unbarred in the near-infrared. The RC3 and the Carnegie Atlas of Galaxies both classify only about 30% of our sample as strongly barred. Thus strong bars are nearly twice as prevalent in the near-infrared as in the optical. The frequency of genuine optically hidden bars is significant, but lower t…
Mass inflow in barred galaxies has been invoked to account for a wide variety of phenomena, but until now direct evidence for inflow has been lacking. We present Fabry-Perot H-alpha observations of the barred spiral galaxy NGC 1530 from which we determine velocities of the ionized gas for the entire region swept by the bar. We compare the velocity field to models of gas flow in barred spirals and show that it is well reproduced by ideal gas hydrodynamic models. Inspection of the models and observations reveals that gas entering the bar dust lanes streams directly down the dust lanes toward the…
We have obtained ground-based I, J and K band images of the spiral galaxy, Messier 74 (NGC 628). This galaxy has been shown to possess a circumnuclear ring of star formation from both near-infrared spectroscopy of CO absorption and sub-millimetre imaging of CO emission. Circumnuclear rings of star formation are believed to exist only as a result of a bar potential. In this paper we show evidence for a weak oval distortion in the centre of M74. We use the results of Combes & Gerin (1985) to suggest that this weak oval potential is responsible for the circumnuclear ring of star formation observe…
A remarkable structure is observed in the innermost regions of the barred galaxy NGC 1415 : a small stellar bar, bright circumnuclear ionized gas seen in Halpha, two bright ionized gas sources, seen in Halpha, just beyond the ends of the small bar and a boxy distribution of optical continuum. We have developed a mass distribution model consisting in disk, a bulge, and a bar to approximate t he observed central morphology and its surface brightness. In order to reproduce the observed optical brightness distribution a two-component bar was used, with one component to model the elongated isophote…
We present high resolution (3" - 5") observations of CO(1-0) and HCN(1-0) emission from the circumnuclear star forming ring in the barred spiral galaxy NGC 6951, a host of a type-2 Seyfert, using the Nobeyama Millimeter Array and 45 m telescope. We find that most of the HCN emission is associated with the circumnuclear ring, where vigorous star formation occurs. The HCN to CO integrated intensity ratio is also enhanced in the star forming ring; the peak value of HCN/CO ratio is 0.18, which is comparable to the ratio in the starbursts NGC 253 and M82. The formation mechanism of dense molecular …
Using the IRAM interferometer we have mapped at high resolution (2"x1") the 12CO(1-0) emission in the nucleus of the doubled barred SABbc spiral M100. Molecular gas is distributed in a two spiral arm structure starting from the end points of the nuclear bar (r=600 pc) and a central source. The kinematics of the gas indicates the existence of a steep rotation curve (180 km/s at 100 pc) and strong streaming motions characteristic of a trailing spiral wave inside corotation. Gas flow simulations analyse the gas response to a gravitational potential derived from the K-band plate, including the two…
Aperture synthesis observations of CO(J=1-0) emission and near-infrared broad-band photometry of the non-barred Seyfert galaxy NGC 5033 (D = 18.7 Mpc) were performed. Our 3".9 x 3".6 resolution CO observations reveal a perturbed distribution and the kinematics of molecular gas in the center of NGC 5033; we find the characteristic gaseous features that are widely observed in barred spiral galaxies, such as two bright CO peaks near the center (separated by ~ 3'' or 270 pc from the nucleus), two offset ridges of CO emission emanating from the CO peaks, and a CO ring (with a radius of ~ 14'' or 1.…
Detailed neutral hydrogen observations have been obtained of the large barred spiral galaxy NGC 3992 and its three small companion galaxies, UGC 6923, UGC 6940, and UGC 6969. For the main galaxy, the HI distribution is regular with a low level radial extension outside the stellar disc. However, at exactly the region of the bar, there is a pronounced central HI hole in the gas distribution. Likely gas has been transported inwards by the bar and because of the emptyness of the hole no large accretion events can have happened in recent galactic times. The gas kinematics is very regular and it is …
We present the results of the CO mapping observations of the barred spiral galaxy NGC3504 with the Nobeyama 45-m telescope. The distribution of the molecular gas shows offset ridges which correspond to the distribution of HII regions along the bar. The velocity perpendicular to the bar decreases abruptly at the ridge. The velocity change implies that the molecular gas changes the direction of its motion to parallel to the bar at the ridge. Since the position angle of the major axis of the bar and the line of nodes are almost the same in NGC 3504, an upper limit to the pattern speed of the bar …
NGC 6782 is an early-type barred spiral galaxy exhibiting a rich and complex morphology with multiple ring patterns. To provide a physical understanding of its structure and kinematical properties, two-dimensional hydrodynamical simulations have been carried out. Numerical calculations reveal that the striking features in NGC 6782 can be reproduced provided that the gas flow is governed by the gravitational potential associated with a slowly rotating strong bar. In particular, the response of the gaseous disk to the bar potential leads to the excitation of spiral density waves at the inner Lin…
Previous optical studies found an unexpected deficit of bars at z > 0.7. To investigate the effects of bandshifting, we have studied the fraction of barred spirals in the NICMOS Deep Field North. At z > 0.7 we find at least four barred spirals, doubling the number previously detected. The number of barred galaxies is small because these (and previous) data lack adequate spatial resolution. A typical 5 kpc bar at z > 0.7 is only marginally detectable for WFPC2 at 0.8microns; the NICMOS data have even lower resolution and can only find the largest bars. The average size of the four bars seen at …
The Halpha gas kinematics of twenty-one representative barred spiral galaxies belonging to the BHaBAR sample is presented. The galaxies were observed with FaNTOmM, a Fabry-Perot integral-field spectrometer, on three different telescopes. The 3D data cubes were processed through a robust pipeline with the aim of providing the most homogeneous and accurate dataset possible useful for further analysis. The data cubes were spatially binned to a constant signal-to-noise ratio, typically around 7. Maps of the monochromatic Halpha emission line and of the velocity field were generated and the kinemat…
The late-type galaxy NGC 4303 (M61) is one of the most intensively studied barred galaxies in the Virgo Cluster. Its prominent enhanced star formation throughout large areas of the disk can be nicely studied due to its low inclination of about 27 \degr. We present observations of NGC 4303 with the ROSAT PSPC and HRI in the soft X-ray (0.1-2.4 keV). The bulk of the X-ray emission is located at the nuclear region. It contributes more than 80% to the total observed soft X-ray flux. The extension of the central X-ray source and the L_X/L_Halpha ratio point to a low luminous AGN (LINER) with a circ…
The Seyfert galaxy NGC 1097 has an extended neutral hydrogen disk, a companion, a prominent bar and a luminous circumnuclear starburst "ring". Magnetic fields as revealed by nonthermal radio-continuum emissions correlate well with the optical barred spiral structure on large scales, have a gross enhancement overlapping with the optical/infrared "ring", and show a trailing swirl around and within the "ring". We propose a scenario of bar-excited long-trailing fast magnetohydrodynamic (MHD) density waves at the modified inner Lindblad resonance (mILR), physically identified with the outer rim of …
We have performed smoothed particle hydrodynamics (SPH) simulations to study the response of the central kiloparsec region of a gaseous disk to the imposition of nonaxisymmetric bar potentials. The model galaxies are composed of the three axisymmetric components (halo, disk, and bulge) and a non-axisymmetric bar. These components are assumed to be invariant in time in the frame corotating with the bar. The potential of spherical $γ$-models of Dehnen is adopted for the bulge component whose density varies as $r^{-γ}$ near the center and $r^{-4}$ at larger radiiand hence, possesses a central den…
We have found four barred S0 galaxies -- NGC 936, NGC 3945, NGC 4340, and NGC 4371 -- which contain smooth, luminous, purely stellar nuclear rings within their bars. These rings have little or no dust, no evidence for recent star formation, and are approximately the same color as surrounding bar and bulge. Thus, they are probably the aged remnants of bar-driven circumnuclear starburst episodes similar to those seen in barred galaxies today. Using kinematic data from long-slit spectroscopy, we construct rotation and resonance curves for two of the galaxies. In both cases, the nuclear rings appe…
We present 3.5cm and 6.2cm radio continuum maps in total and polarized intensity of the barred galaxies NGC 1097 and NGC 1365. Both galaxies exhibit radio ridges roughly overlapping with the massive dust lanes in the bar region. The contrast in total intensity across the radio ridges is compatible with compression and shear of an isotropic random magnetic field. The contrast in polarized intensity is significantly smaller than that expected from compression and shearing of the regular magnetic field; this could be the result of decoupling of the regular field from the dense molecular clouds. T…
The non-circular streaming motions in barred galaxies are sensitive to the mass of the bar and can be used to lift the degeneracy between disk and dark matter halo encountered when fitting axisymmetric rotation curves of disk galaxies. In this paper, we present photometric and kinematic observations of NGC 4123, a barred galaxy of modest size (V_rot = 130 km/sec, L = 0.7 L_*), which reveal strong non-circular motions. The bar has straight dust lanes and an inner Lindblad resonance. The disk of NGC 4123 has no sign of truncation out to 10 scale lengths, and star-forming regions are found well o…
We report new detailed surface U, B, V, R, and I photometry of 81 stellar structures in the disk of the barred galaxy NGC 3367. The images show many different structures indicating that star formation is going on in the most part of the disk. NGC 3367 is known to have a very high concentration of molecular gas distribution in the central regions of the galaxy and bipolar synchrotron emission from the nucleus with two lobes (at 6 kpc) forming a triple structure similar to a radio galaxy. We have determined the U, B, V, R, and I magnitudes and U - B, B - V, U - V, and V - I colors for the centra…
We present CO(1-0) and CO(2-1) maps of the Seyfert galaxy NGC 5728. Although a stellar nuclear bar structure is clearly identified in the near-infrared images in the central 10", inside the ring identified as the ILR of the primary bar, there is no nuclear bar structure in the molecular gas. Instead, the CO emission reveals an elongated structure, 15" in length, beginning at the nucleus (defined by the radio center) aligned with the jet/ionisation cone, at a PA of 127 degrees. This morphology, not frequently observed in Seyfert galaxies, may be interpreted in terms of enhanced CO excitation al…
We report a dynamical determination of the separate contributions of disk and dark halo masses to the rotation curve of a spiral galaxy. We use fluid-dynamical models of gas flow in the barred galaxy NGC 4123 to constrain the dynamical properties of the galaxy: disk M/L, bar pattern speed, and the central density and scale radius of the dark halo. We derive a realistic barred potential directly from the light distribution. For each model we assume a value of the stellar M/L and a bar pattern speed Omega_p and add a dark halo to fit the rotation curve. We then compute the gas flow velocities wi…
We present sub-arcsecond resolution ground-based near-infrared images of the central regions of a sample of twelve barred galaxies with circumnuclear star formation activity, which is organized in ring-like regions typically one kiloparsec in diameter. We also present Hubble Space Telescope near-infrared images of ten of our sample galaxies, and compare them with our ground-based data. Although our sample galaxies were selected for the presence of circumnuclear star formation activity, our broad-band near-infrared images are heterogeneous, showing a substantial amount of small-scale structure …
Double bars have been proposed as a means of transporting molecular gas past inner Lindblad resonances into the nuclear regions, where it can fuel active or starburst nuclei. Thus far, the existence of double bars has been determined predominantly through analysis of near infrared images, which can tell us little about the dynamics and inflow rates of these systems. We have observed two double bar galaxy candidates (NGC 2273 and NGC 5728) in CO J=1-0 with the Owens Valley Radio Observatory Millimeter Array. Despite the similarity in the near infrared images of these galaxies, we see rather dif…
ESO 566-24 is an extraordinary barred galaxy, which has four regularly spaced spiral arms in blue light images. This type of four-armed spiral structure, which is rare among the spiral population, is clearly seen also in near-infrared images, and thus is present in the old stellar population. We have constructed dynamical models of ESO 566-24 in order to understand the cause of its four-armed structure. The disk gravitational potential is determined from near-infrared photometry, and the gas dynamics is modelled as inelastically colliding particles. The resulting morphology and kinematics with…
For the intermediate-type barred galaxy NGC2336 stationary models are constructed which reproduce in a consistent manner the observed distribution of the luminous matter and the observed gas kinematics in those regions affected by the bar. We present 2D fits to the observed NIR-band luminosity distribution that consist of three components: a bulge, a bar, and a disk. The brightness distribution of each component is converted into an underlying mass distribution by means of a suitable M/L-conversion. The resulting coadded potential of NGC2336 is implemented into a numerical code for the computa…
Although nuclear rings of gas and star formation are common in barred spiral galaxies, current theories of why and how they form do not provide the level of detail needed to quantify the effect that these rings can have on the fueling of active galactic nuclei and on the evolution of their host galaxy. In this paper we use detailed modeling to show that existence of nuclear rings is directly related to the existence of the orbit family whose major axis is perpendicular to the major axis of the bar (x_2). We explore a large range of barred galaxy potentials and for each potential we use a two-d…
In this paper we present building blocks which can explain the formation and properties both of spirals and of inner and outer rings in barred galaxies. We first briefly summarise the main results of the full theoretical description we have given elsewhere, presenting them in a more physical way, aimed to an understanding without the requirement of extended knowledge of dynamical systems or of orbital structure. We introduce in this manner the notion of manifolds, which can be thought of as tubes guiding the orbits. The dynamics of these manifolds can govern the properties of spirals and of in…
We report on high-resolution interferometer observations of the 12CO(J=1-0) emission in the central 5 kpc region of the Seyfert 2 galaxy NGC 4501. The observations were made using the Nobeyama Millimeter Array during a long-term CO line survey of Virgo spirals. The major features are: (1) a nuclear concentration with a radius of r~5'' (390 pc), which is resolved into double peaks, and (2) spiral arms which extend out from the nuclear region. The nuclear component has a mass of 1.3x10^8 Mo, which corresponds to ~3.5% of the dynamical mass, and shows a slight non-circular motion. The double peak…
We have determined the structure and kinematics of ionised gas in the weak oval bar of the archetypal Seyfert 1 galaxy, NGC 4151, using the TAURUS Fabry-Perot interferometer to simultaneously map the distribution and kinematics of Hbeta emission. We also present broad-band ultraviolet imaging of the host galaxy, obtained with XMM-Newton, that shows the detailed distribution of star formation in the bar and in the optically-faint outer spiral arms. We compare the distribution and kinematics of ionised gas with that previously determined in neutral hydrogen by Mundell & Shone; we suggest that th…
Companion galaxy environment for a subset of 78 bright and nearby barred galaxies from the Shapley Ames Catalog is presented. Among spiral barred galaxies there are Seyfert galaxies, galaxies with circumnuclear structures, galaxies not associated with any large scale galaxy cloud structure, galaxies with peculiar disk morphology (crooked arms) and galaxies with normal disk morphology; the list includes all Hubble types. The companion galaxy list includes number of companion galaxies within 20 diameters (D25), their Hubble type and projected separation distance. Additionally, companion environm…
Although inner star-forming rings are common in optical images of barred spiral galaxies, observational evidence for the accompanying molecular gas has been scarce. In this paper we present images of molecular inner rings, traced using the CO (1-0) emission line, from the Berkeley-Illinois-Maryland-Association Survey of Nearby Galaxies (BIMA SONG). We detect inner ring CO emission from all five SONG barred galaxies classified as inner ring (type (r)). We also examine the seven SONG barred galaxies classified as inner spiral (type (s)); in one of these, NGC 3627, we find morphological and kinem…
We present 13CO(1-0) and 12CO(2-1) aperture synthesis maps of the barred spiral galaxy NGC1530. The angular resolutions are respectively 3''.1 and 1''.6. Both transitions show features similar to the 12CO(1-0) map, with a nuclear feature (a ring or unresolved spiral arms) surrounded by two curved arcs. The average line ratios are 12CO(1-0)/13CO(1-0)=9.3 and 12CO(2-1)/12CO(1-0)=0.7. The 12CO/13CO ratio is lower in the circumnuclear ring (6-8) than in the arcs (11-15). We fit the observed line ratios by escape probability models, and deduce that the gas density is probably higher in the nuclear …
