Secondary Bar Research Articles

Dynamical influence of a central massive object on double-barred galaxies: self-destruction mechanism of secondary bars

Abstract Double-barred galaxies exhibit sub-kiloparsec secondary stellar bars that are crucial for channeling gases towards a central massive object (CMO) such as a supermassive black hole or a nuclear star cluster. Recent N-body simulations have uncovered a novel galaxy evolution scenario wherein the mass of the CMO increases owing to the secondary bar, resulting in the eventual destruction of the latter. Consequently, the CMO mass growth halts, thus suggesting a maximum CMO mass of ≈10−3 of the stellar mass of the galaxy. This study focuses on backbone orbit families, particularly double-frequency orbits, within double-barred galaxies. Consequently, the dynamic influence of a CMO on these orbits is investigated. The results of the study reveal the emergence of a new orbital resonance within the central region of the galaxy upon the introduction of a CMO. Orbits subjected to this resonance become chaotic and fail to support the secondary bar, ultimately resulting in the destruction of the entire structure. This is partly because of the inability of the secondary bar to obtain support from the newly generated orbit families following the appearance of resonance. Through the estimation of the condition of secondary bar destruction in realistic double-bar galaxies with varying pattern speeds, the results of the study establish that such destruction occurred when the CMO mass reached ≈10−3 of the galaxy mass. Furthermore, a physical explanation of the galaxy evolution scenario is provided, thereby elucidating the interaction between the CMO and the secondary bar. The understanding of the co-evolution of the secondary bar and the CMO, based on stellar orbital motion, is a crucial step towards future observational studies of stars within the bulge of the Milky Way.

Immediate Implants, Immediate Loading, and Milled Double Bar Prosthesis (Titanium, Biohpp): A Case Report

Abstract To rehabilitate lower arch by placing immediate implants and immediate milled provisionals and provide double bar prosthesis for the long-term survival of implants. Full-mouth rehabilitation by integrating cone-beam computed tomography data three-dimensional printing technology helps in precise placement and predictable outcomes to the longevity of implants. Six immediate implants were placed in the lower arch using digitally guided surgery. Computer-aided design-computer-aided manufacture milled temporary prosthesis was also given within 24 h of the surgery. After allowing for osseointegration, the final prosthesis was made up of materials such as titanium (primary bar), PEEK (secondary bar), and high-impact polymer composite crowns. Splinting all the implants together with such framework designs reduces the loads on implants and addition of two bars produces a dampening effect and helps long-term survival of the same. Strategies used to preserve alveolar bone and soft tissue by immediate implant placement in fresh extraction sockets shorten the treatment span. Immediate loading of implants using temporary prosthesis can be done after attaining adequate primary stability. This case has a follow-up of 6 years. The milled double bars made out of titanium and BioHPP h provide dampening effect and thus long-term survival of the implant.

To Cross or Not to Cross: The Cross-Bar Technique to Correct Pectus Excavatum With “Costal Flaring”

BackgroundThe minimally invasive repair of pectus excavatum (PE), introduced by Nuss in 1998, represents the worldwide “gold standard” procedure for surgical repair. Modifications over years included routine use of unilateral or bilateral thoracoscopy as well as sternal elevation before starting the substernal dissection. In patients with a severe PE deformity, such as Grand Canyon type, use of a second bar or, in selected patients, even a third or fourth bar has to be considered. However, not only the number of bars but also positioning may vary. Park established the so-called cross-bar technique to correct a wider range of PE deformities, especially at the lower part of the depression. MethodsWe report our experience applying the cross-bar technique in 5 PE patients presenting with severe bilateral costal flaring. ResultsWith unilateral thoracoscopy and sternal elevation using the vacuum bell, surgical repair went well in all patients. Fortunately, we noticed no secondary bar displacement or any other serious postoperative complication; 1 of the 5 patients completed treatment with elective pectus bar removal. Optimal correction of the deformity was achieved in all patients; the outcome was excellent. ConclusionsIndividualized surgical repair is mandatory in PE patients presenting with complex deformities. In PE patients presenting with concomitant bilateral costal flaring or depression of the lower part of the chest wall, we recommend the cross-bar insertion technique for surgical repair to achieve excellent cosmetic results.

Description of a new species of Characidium Reinhardt, 1867 (Characiformes: Crenuchidae) from the Chapada Diamantina, Bahia, and redescription of Characidium bimaculatum Fowler, 1941.

A new species of Characidium Reinhardt, 1867 endemic to tributaries of the upper rio Paraguaçu in the Chapada Diamantina, Bahia, Brazil, is described. The new species can be distinguished from its congeners except C. bahiense,C. bimaculatum, C. laterale, C. nana, C. nupelia, and C. xavante, by having a conspicuous peduncular blotch in addition to the basicaudal spot on the base of the middle caudal-fin rays. Among other features, the new species differs from C. bahiense, C. laterale, C. nana, C. nupelia, and C. xavante by having a complete lateral line with 32-36 perforated scales (vs. lateral line short, with 9-11 perforated scales), and from C. bimaculatum by the body pigmentation pattern, with secondary bars present (vs. absent), total bars 11-16 (vs. 10-12), peduncular blotch rounded (vs. horizontally elongated), and mature males not having a darker dorsal fin (vs. proximal third of dorsal fin darker in mature males). Characidium bimaculatum, a poorly known species from Northeastern Brazil, is redescribed.

Improved designs of disk induction motors of block-module type for extreme environments

The construction of new disk induction motors of block-module type, which are a part of motor-transformer units (MTUs), are considered. The induction motors are intended for operation in hermetic objects under extreme conditions: a gas, steam-to-gas, and liquid environment at high pressures (up to 150MPa) and temperature (up to +600°C). The primary winding of the transformer part of the unit is connected to a three-phase network, and the secondary z-phase bar winding is located in Z grooves of the magnetic conductor of a transformer closed on one side by a short-circuited ring. The motor part of the unit contains an induction motor with a short-circuited rotor and stator with bar uninsulated winding connected to the transformer secondary winding; on the opposite side, it is closed by a short-circuited ring. The induction motor can be implemented with a disk short-circuited rotor located between two disk stators with bar windings. The bars of the transformer secondary winding are connected with Z bar-shaped hermetic lead-ins installed in a hermetic partition. Each bar-shaped hermetic lead-in is connected at the other end with n bars of the stator winding through intermediate conductive arc-shaped segments adjoining the stator. The operating principle and operation features of new disk induction motors of block-module type are considered.

The individualized correction of the secondary deformities post-traumatic physeal bar of distal tibia

The individualized correction of the secondary deformities post-traumatic physeal bar of distal tibia

FORMING DOUBLE-BARRED GALAXIES FROM DYNAMICALLY COOL INNER DISKS

About one third of early-type barred galaxies host small-scale secondary bars. The formation and evolution of such double-barred galaxies remain far from being well understood. In order to understand the formation of such systems, we explore a large parameter space of isolated pure-disk simulations. We show that a dynamically cool inner disk embedded in a hotter outer disk can naturally generate a steady secondary bar while the outer disk forms a large-scale primary bar. The independent bar instabilities of inner and outer disks result in long-lived double-barred structures whose dynamical properties are comparable with observations. This formation scenario indicates that the secondary bar might form from the general bar instability, the same as the primary bar. Under some circumstances, the interaction of the bars and the disk leads to the two bars aligning or single, nuclear, bars only. Simulations that are cool enough of the center to experience clump instabilities may also generate steady double-barred galaxies. In this case, the secondary bars are "fast", i.e., the bar length is close to the co-rotation radius. This is the first time that double-barred galaxies containing a fast secondary bar are reported. Previous orbit-based studies had suggested that fast secondary bars are not dynamically possible.

How can double-barred galaxies be long-lived?

Double-barred galaxies account for almost one third of all barred galaxies, suggesting that secondary stellar bars, which are embedded in large-scale primary bars, are long-lived structures. However, up to now it has been hard to self-consistently simulate a disc galaxy that sustains two nested stellar bars for longer than a few rotation periods. N-body/hydrodynamical simulations including star formation recipes have been performed. Their properties have been compared with the most recent observational data in order to prove that they are representative of double-barred galaxies, even SB0. Overlaps in dynamical resonances and bar modes have been looked for using Fourier spectrograms. Double-barred galaxies have been successfully simulated with lifetimes as long as 7 Gyr. The stellar population of the secondary bar is younger on average than for the primary large-scale bar. An important feature of these simulations is the absence of any resonance overlap for several Gyr. In particular, there is no overlap between the primary bar ILR and the secondary bar corotation. Therefore, mode coupling cannot sustain the secondary bar mode. Star formation is identified here as possibly being responsible for bringing energy to the nuclear mode. Star formation is also responsible for limiting the amount of gas in the central region which prevents the orbits sustaining the secondary bar from being destroyed. Therefore, the secondary bar can dissolve but reappear after approx. 1 Gyr. When star formation is switched off the dynamical perturbation associated with the secondary bar needs several Gyr to fully vanish. Double-bars can be long-lived in numerical simulations with a gaseous component, even in the absence of overlap of resonances or mode coupling, provided that star formation remains active in the central region where the nuclear bar lies.

Monitoring of riparian vegetation response to flood disturbances using terrestrial photography

Abstract. Flood disturbance is one of the major factors impacting riparian vegetation on river floodplains. In this study we use a high-resolution ground-based camera system with near-infrared sensitivity to quantify the immediate response of riparian vegetation in an Alpine, gravel bed, braided river to flood disturbance with the use of vegetation indices. Five large floods with return periods between 1.4 and 20.1 years in the period 2008–2011 in the Maggia River were analysed to evaluate patterns of vegetation response in three distinct floodplain units (main bar, secondary bar, transitional zone) and to compare the sensitivity of seven broadband vegetation indices. The results show both a negative (damage) and positive (enhancement) response of vegetation within 1 week following the floods, with a selective impact determined by pre-flood vegetation vigour, geomorphological setting and intensity of the flood forcing. The spatial distribution of vegetation damage provides a coherent picture of floodplain response in the three floodplain units. The vegetation indices tested in a riverine environment with highly variable surface wetness, high gravel reflectance, and extensive water–soil–vegetation contact zones differ in the direction of predicted change and its spatial distribution in the range 0.7–35.8%. We conclude that vegetation response to flood disturbance may be effectively monitored by terrestrial photography with near-infrared sensitivity, with potential for long-term assessment in river management and restoration projects.

A New Species ofCharacidium(Characiformes: Crenuchidae) from Coastal Basins of Serra do Mar, Southeastern Brazil

Characidium litorale, a new species of characidiin fish, is described from coastal basins of the northeastern portion of the Serra do Mar, State of Rio de Janeiro, southeastern Brazil. The species presents thin dark secondary bars (vertical streaks not associated with dorsal marks) positioned between the primary vertical bars (bars directly associated with well-defined dorsal marks) on the side of the body. Characidium litorale is the first species described from the southeastern Brazilian coastal drainages with basicaudal black spot well defined, fully scaled isthmus, and hyaline fins. Unlike other species of Characidium from this region (predominately found associated with rocky substrate), C. litorale has psammophilous habits. An identification key to the species of Characidium occurring sympatrically with the new species is presented.Descreve-se Characidium litorale, nova espécie de peixe caracidiíneo distribuída em bacias costeiras da porção nordeste da Serra do Mar, Estado do Rio de Janeiro, sudeste do Brasil. A espécie apresenta barras secundárias finas e escuras (estrias verticais não associadas a manchas dorsais) localizadas entre as barras verticais primárias (barras diretamente associadas a manchas dorsais bem definidas) das laterais do corpo. Characidium litorale é a primeira espécie descrita das drenagens costeiras do sudeste do Brasil com ponto preto basicaudal bem definido, escamação completa no istmo, e nadadeiras hialinas. Diferentemente das outras espécies de Characidium dessa região (predominantemente encontradas associadas a substratos rochosos), C. litorale possui hábitos psamófilos. Apresenta-se uma chave de identificação para espécies de Characidium que ocorrem em simpatria com a nova espécie.

Loss Evaluation of 1-MW-Class Induction Motor at Inverter Feeding

In this study, we evaluate the losses of a 1-MW-class induction motor at the inverter feeding. We propose a loss calculation method using the resistivity of the bars based on an expression of the motor characteristic and measured results. Then, we separate the losses into no-load iron loss, stray load loss, and time-harmonic loss by the inverter feeding. The results show that the measured and corresponding calculated losses agree well. Then, it is clarified that the secondary harmonic loss is especially large. In addition, we reveal that the time-harmonic losses are caused by the magnetic flux of the carrier harmonics, which passes through the surfaces of the secondary bars by a calculation considering the carrier-harmonic currents.

ALMA observations of feeding and feedback in nearby Seyfert galaxies: an AGN-driven outflow in NGC 1433

We report ALMA observations of CO(3-2) emission in the Seyfert 2 double-barred galaxy NGC1433, at the unprecedented spatial resolution of 0.5"=24 pc. Our aim is to probe AGN feeding and feedback phenomena through the morphology and dynamics of the gas inside the central kpc. The CO map, which covers the whole nuclear region (nuclear bar and ring), reveals a nuclear gaseous spiral structure, inside the nuclear ring encircling the nuclear stellar bar. This gaseous spiral is well correlated with the dusty spiral seen in Hubble Space Telescope images. The nuclear spiral winds up in a pseudo-ring at 200 pc radius, which might correspond to the inner ILR. Continuum emission is detected at 0.87 mm only at the very centre, and its origin is more likely thermal dust emission than non-thermal emission from the AGN. It might correspond to the molecular torus expected to exist in this Seyfert 2 galaxy. The HCN(4-3) and HCO+(4-3) lines were observed simultaneously, but only upper limits are derived, with a ratio to the CO(3-2) line lower than 1/60 at 3sigma, indicating a relatively low abundance of very dense gas. The kinematics of the gas over the nuclear disk reveal rather regular rotation only slightly perturbed by streaming motions due to the spiral; the primary and secondary bars are too closely aligned with the galaxy major or minor axis to leave a signature in the projected velocities. Near the nucleus, there is an intense high-velocity CO emission feature redshifted to 200 km/s (if located in the plane), with a blue-shifted counterpart, at 2" (100 pc) from the centre. While the CO spectra are quite narrow in the centre, this wide component is interpreted as an outflow involving a molecular mass of 3.6 10^6 Mo and a flow rate 7 Mo/yr. The flow could be in part driven by the central star formation, but is mainly boosted by the AGN through its wind or radio jets.

La evolución reciente del cauce del río Ara

This paper studies the evolution of the Ara river from 1929 till now in a bench between Boltaña and Aínsa. Methods are based mainly infield work and in the use of aereal photographs corresponding to 1929, 1946, 1956, 1981, 1984 and 1988. The authors have elaborated a geomorphological cartography that allows us to establish the changes in channel morphology: progressive enlargement ofthe fluvíal bed; predominance of areas without plant cover until 1956; development of plant cover from 1956 unta now; subdivision of the main bars in small secondary bars owing to a increase of the number of channels; increasing human activities from 1974 (building of the Mediano reservoir and channelization of the river by means of lateral dykes).

Spontaneous formation of double bars in dark-matter-dominated galaxies

Abstract Although nearly one-third of barred galaxies host an inner, secondary bar, the formation and evolution of double barred galaxies remain unclear. We show here an example model of a galaxy, dominated by a live dark matter halo, in which double bars form naturally, without requiring gas, and we follow its evolution for a Hubble time. The inner bar in our model galaxy rotates almost as slowly as the outer bar, and it can reach up to half of its length. The route to the formation of a double bar may be different from that of a single strong bar. Massive dark matter halo or dynamically hot stellar disc may play an important role in the formation of double bars and their subsequent evolution.

Multiple bars and secular evolution

AbstractBars are the most important driver of secular evolution. A significant fraction of barred galaxies also harbor small secondary bars. Secondary bars are visible even in near-infrared images, so they are not just dusty and blue, but stellar features (Erwin & Sparke 2002). Since they are quite common, secondary bars are probably long-lived stellar features. The random relative orientation of the two bars indicates that they are dynamically decoupled with different pattern speeds (Buta & Crocker 1993). Corsini et al. (2003) presented conclusive direct kinematic evidence for a decoupled secondary bar in NGC 2950. Dynamically decoupled secondary bars have long been hypothesized to be a mechanism to drive gas past the ILR of primary bars to feed active galactic nuclei (Shlosman et al. 1989). However, the dynamics of secondary bars are still not well understood, and it is still unclear what role secondary bars play in the AGN fueling process.Numerical simulations offer the best approach to understanding double-barred systems. Decoupled secondary bar in the earlier gaseous simulations only last a short time (< 1 Gyr, e.g. Friedli & Martinet 1993). Orbital studies of double-barred systems discovered a family of loop orbits that may be building blocks of long-lived nuclear stellar bars (Maciejewski & Sparke 1997, 2000). To complement orbital studies, which are not fully self-consistent, N-body simulations are preferred to further our understanding of double-barred systems. Debattista & Shen (2007) and Shen & Debattista (2009) managed to form long-lived double-barred systems with purely collisionless simulations, where a pre-existing rotating pseudo-bulge is introduced initially. The shape and size of secondary bars in the models are comparable to observed ones. They found that the rotation of the two bars is not rigid. The amplitude and pattern speed of the secondary bars oscillate as they rotate through their primary counterparts. Although the secondary bar rotates faster than the primary bar in this model, the stellar velocity field in the central region only shows a weakly twisted kinematic minor axis.Recently more simulations of double-barred galaxies with simpler initial conditions are explored (Du, Shen & Debattista 2014). We expect that the new models can be used to cross-check with the kinematic properties of double-barred galaxies from IFU observations such as SAURON and Atlas3D.

Optical Integral Field Spectroscopy of NGC 5850

Here we present the preliminary results of the analysis of VIMOS observations of the central 4.5 kpc of the double-barred galaxy NGC 5850. We use optical diagnostic diagrams to study the main ionization mecahnism across the field of view confirming the LINER nature in the continuum peak location. Also a star-forming (SF) region is found close to it (0.46kpc), a second SF region is located east of the center (1.6kpc). Further the data reveals a complex nuclear gas kinematics which is likely to be dominated by the secondary bar.

PATTERN SPEEDS OF BARS AND SPIRAL ARMS FROM Hα VELOCITY FIELDS

We have applied the Tremaine-Weinberg method to 10 late-type barred spiral galaxies using data cubes, in H-alpha emission, from the GHAFAS and FANTOMM Fabry-Perot spectrometers. We have combined the derived bar (and/or spiral) pattern speeds with angular frequency plots to measure the corotation radii for the bars in these galaxies. We base our results on a combination of this method with a morphological analysis designed to estimate the corotation radius to bar-length ratio using two independent techniques on archival near infrared images, and although we are aware of the limitation of the application of the Tremaine-Weinberg method using ionised gas observations, we find consistently excellent agreement between bar and spiral arm parameters derived using different methods. In general, the corotation radius, measured using the Tremaine-Weinberg method, is closely related to the bar length, measured independently from photometry and consistent with previous studies. Our corotation/bar-length ratios and pattern speed values are in good agreement with general results from numerical simulations of bars. In systems with identified secondary bars, we measure higher H-alpha velocity dispersion in the circumnuclear regions, whereas in all the other galaxies, we detect flat velocity dispersion profiles. The excellent agreement between the Tremaine-Weinberg method results and the morphological analysis and bar parameters in numerical simulations, suggests that although the H-alpha emitting gas does not obey the continuity equation, it can be used to derive the bar pattern speed.

Child pectus excavatum: Correction by minimally invasive surgery

Pectus excavatum (PE) is a congenital deformity essentially responsible for an unattractive aspect, much more rarely for compression problems. The classical treatments consist either in filling the excavation or in open thoracic reconstruction (the Ravitch technique). Alternatively, the treatment described by Nuss raises the sternum with a retrosternal metallic bar placed under thoracoscopic guidance. We present the preliminary results of a series of 25 children operated on using this technique. The minimally invasive procedure described by Nuss is a valid surgical strategy to treat PE. Twenty-five patients were operated on between February 2004 and April 2007 by the same surgeon. Nineteen of these patients presented a purely cosmetic indication. The six other patients were considered to have a more severe form of PE, with cardiorespiratory repercussions. In this group, there were two cases of Marfan syndrome and two patients presenting a history of previous cardiothoracic surgery. The technique has always consisted in placing a retrosternal bar through two lateral incisions. The surgery was always performed with right lung exclusion and was guided by thoracoscopy in 21 cases. In four particularly severe cases, a subxiphoid approach was required, making endoscopic guidance unnecessary. The severity of the lesion was evaluated by the Haller Index. All the patients had regular clinical follow-up (at three weeks, three months, and then every six months); assessment of pain, satisfaction with the cosmetic results, and perceived improvement in respiratory function were the criteria used for this follow-up. The cosmetic result was judged to be positive by 24 patients. One patient was dissatisfied (because of the asymmetrical shape resulting from the use of a single implant). Five patients presented minor complications with no repercussions on the cosmetic or functional result. One case of secondary bar displacement required revision on day 15. Following this revision evolution was uncomplicated (discharge on day 7 and activities resumed at three weeks). Finally, the hardware was removed at a delay after implantation ranging from one to two years. As of today, 13 patients have had their hardware removed with no complications or loss of the initial result. The original indication of the Nuss technique remains symmetrical PE in seven to 14-year-old children. The insubstantial scarring makes the technique valuable in the purely cosmetic forms of the condition. Based on this series, our technique has evolved toward certain adjustments depending on the severity and the etiology of the lesion. The most reported complication in the literature is secondary displacement of the bars. This problem is easily controlled by attaching the bar to a rib. Over the years, we have modified the implant design so as to improve its tolerance and stability. In asymmetrical forms of PE, implanting two bars has provided better efficacy. When a major form is present or when there is a history of cardiorespiratory problems, we recommend a short subxiphoid incision to release the pleural and pericardial adherences, precluding the need for thoracoscopic guidance. With these simple adjustments, this technique gains in reliability for cosmetic indications and its use can be extended to specific forms such as collagenosis or postoperative deformities. Level IV. Therapeutic Study.

OBSERVABLE PROPERTIES OF DOUBLE-BARRED GALAXIES INN-BODY SIMULATIONS

Although at least one quarter of early-type barred galaxies host secondary stellar bars embedded in their large-scale primary counterparts, the dynamics of such double-barred galaxies are still not well understood. Recently we reported success at simulating such systems in a repeatable way in collisionless systems. In order to further our understanding of double-barred galaxies, here we characterize the density and kinematics of the N-body simulations of these galaxies. This will facilitate comparison with observations and lead to a better understanding of the observed double-barred galaxies. We find the shape and size of our simulated secondary bars are quite reasonable compared to the observed ones. We demonstrate that an authentic decoupled secondary bar may produce only a weak twist of the kinematic minor axis in the stellar velocity field, due to the relatively large random motion of stars in the central region. We also find that the edge-on nuclear bars are probably not related to boxy peanut-shaped bulges which are most likely to be edge-on primary large-scale bars. Another kinematic feature often present in our double-barred models is a ring-like feature in the fourth-order Gauss-Hermite moment h4 maps. Finally, we demonstrate that the non-rigid rotation of the secondary bar causes its pattern speed to not be derived with great accuracy using the Tremaine-Weinberg method. We also compare with observations of NGC 2950, a prototypical double-barred early-type galaxy, which suggest that the nuclear bar may be rotating in the opposite sense as the primary.

Disk Evolution and Bar Triggering Driven by Interactions with Dark Matter Substructure

We study formation and evolution of bar-disk systems in fully self-consistent cosmological simulations of galaxy formation in the ΛCDM WMAP3 universe. In a representative model we find that the first generation of bars form in response to the asymmetric dark matter (DM) distribution (i.e., DM filament) and quickly decay. Subsequent bar generations form and are destroyed during the major merger epoch permeated by interactions with a DM substructure (subhalos). A long-lived bar is triggered by a tide from a subhalo and survives for ~10 Gyr. The evolution of this bar is followed during the subsequent numerous minor mergers and interactions with the substructure. Together with intrinsic factors, these interactions largely determine the stellar bar evolution. The bar strength and its pattern speed anticorrelate, except during interactions and the formation of a secondary (nuclear) bar. For about 5 Gyr bar pattern speed increases substantially despite the loss of angular momentum to stars and cuspy DM halo. We analyze the evolution of stellar populations in the bar-disk and relate them to the underlying dynamics. While the bar is made mainly of an intermediate age, ~5-6 Gyr, disk stars at z = 0, a secondary nuclear bar which surfaces at z ~ 0.1 is made of younger, ~1-3 Gyr stars.