The Kinematically Measured Pattern Speeds of NGC 2523 and NGC 4245

We have applied the Tremaine-Weinberg continuity equation method to derive the bar pattern speed in the SB(r)b galaxy NGC 2523 and the SB(r)0/a galaxy NGC 4245 using the Calcium Triplet absorption lines. These galaxies were selected because they have strong inner rings which can be used as independent tracers of the pattern speed. The pattern speed of NGC 2523 is 26.4 $\pm$ 6.1 km s$^{-1}$ kpc$^{-1}$, assuming an inclination of 49.7$^{\circ}$ and a distance of 51.0 Mpc. The pattern speed of NGC 4245 is 75.5 $\pm$ 31.3 km s$^{-1}$ kpc$^{-1}$, assuming an inclination of 35.4$^{\circ}$ and a distance of 12.6 Mpc. The ratio of the corotation radius to the bar radius of NGC 2523 and NGC 4245 is 1.4 $\pm$ 0.3 and 1.1 $\pm$ 0.5, respectively. These values place the bright inner rings near and slightly inside the corotation radius, as predicted by barred galaxy theory. Within the uncertainties, both galaxies are found to have fast bars that likely indicate dark halos of low central concentration. The photometric properties, bar strengths, and disk stabilities of both galaxies are also discussed.Comment: Accepted for publication in The Astronomical Journal, 11 figures, 2 table

Comparison of bar strengths in active and non-active galaxies

Bar strengths are compared between active and non-active galaxies for a sample of 43 barred galaxies. The relative bar torques are determined using a new technique (Buta and Block 2001), where maximum tangential forces are calculated in the bar region, normalized to the axisymmetric radial force field. We use JHK images of the 2 Micron All Sky Survey. We show a first clear empirical indication that the ellipticies of bars are correlated with the non-axisymmetric forces in the bar regions. We found that nuclear activity appears preferentially in those early type galaxies in which the maximum bar torques are weak and appear at quite large distances from the galactic center. Most suprisingly the galaxies with the strongest bars are non-active. Our results imply that the bulges may be important for the onset of nuclear activity, but that the correlation between the nuclear activity and the early type galaxies is not straightforward.Comment: MNRAS macro in tex format, 9 pages, 10 figure

A Mixed-Methods Investigation of Community Attachment in Rural Romania

This article explores the intricacies of community attachment using a multidimensional construct; attachment to the social and natural environment. A central focus is to assess whether attachment to the social and natural environment are distinctively predicted by length of residence, social interaction, and sociodemographic characteristics. Furthermore, this work elaborates on current understandings of community attachment by qualitatively exploring feelings of attachment toward the place of residence. All are explored in the context of rural Romania and communities managing the natural resources available to them. The results show the effect of several independent variables on attachment to social and natural environments. Residency was a stronger predictor of attachment to the social environment, while social interaction was a stronger predictor of attachment to the natural environment. Residents’ narratives underscored the importance, and interconnection, of the social and natural environment in defining feelings of local attachment. We conclude that community attachment is grounded in different facets of the locale that each play unique roles in shaping citizen perceptions

Multiple-Notch Frequency Selective Surface for Automotive Applications

A one-layer frequency selective surface (FSS) is proposed for wide-band and multiple-notch filtering applications. The structure consists of one or two pairs of modified square rings on one side of the supporting dielectric layer. Two, three and four notches are obtained by modifying the parameters involved. A parametric analysis concerning the frequency response in function of the substrate thickness is reported, demonstrating the possibility of changing the stop bands and providing design flexibility. By duplicating the structure on both sides of the FR4 substrate, a wide band is obtained, for both TE and TM polarizations. The devised FSS can be used for filtering in the Wi-Fi, Bluetooth and X bands for Automotive applications. The analysis is realized by full-wave electromagnetic simulation

N-body simulations in reconstruction of the kinematics of young stars in the Galaxy

We try to determine the Galactic structure by comparing the observed and modeled velocities of OB-associations in the 3 kpc solar neighborhood. We made N-body simulations with a rotating stellar bar. The galactic disk in our model includes gas and stellar subsystems. The velocities of gas particles averaged over large time intervals ($\sim 8$ bar rotation periods) are compared with the observed velocities of the OB-associations. Our models reproduce the directions of the radial and azimuthal components of the observed residual velocities in the Perseus and Sagittarius regions and in the Local system. The mean difference between the model and observed velocities is $\Delta V=3.3$ km s$^{-1}$. The optimal value of the solar position angle $\theta_b$ providing the best agreement between the model and observed velocities is $\theta_b=45\pm5^\circ$, in good accordance with several recent estimates. The self-gravitating stellar subsystem forms a bar, an outer ring of subclass $R_1$, and slower spiral modes. Their combined gravitational perturbation leads to time-dependent morphology in the gas subsystem, which forms outer rings with elements of the $R_1$- and $R_2$-morphology. The success of N-body simulations in the Local System is likely due to the gravity of the stellar $R_1$-ring, which is omitted in models with analytical bars.Comment: 13 pages, 13 figures, accepted to Astronomy and Astrophysic

Density Waves Inside Inner Lindblad Resonance: Nuclear Spirals in Disk Galaxies

We analyze formation of grand-design two-arm spiral structure in the nuclear regions of disk galaxies. Such morphology has been recently detected in a number of objects using high-resolution near-infrared observations. Motivated by the observed (1) continuity between the nuclear and kpc-scale spiral structures, and by (2) low arm-interarm contrast, we apply the density wave theory to explain the basic properties of the spiral nuclear morphology. In particular, we address the mechanism for the formation, maintenance and the detailed shape of nuclear spirals. We find, that the latter depends mostly on the shape of the underlying gravitational potential and the sound speed in the gas. Detection of nuclear spiral arms provides diagnostics of mass distribution within the central kpc of disk galaxies. Our results are supported by 2D numerical simulations of gas response to the background gravitational potential of a barred stellar disk. We investigate the parameter space allowed for the formation of nuclear spirals using a new method for constructing a gravitational potential in a barred galaxy, where positions of resonances are prescribed.Comment: 18 pages, 9 figures, higher resolution available at http://www.pa.uky.edu/~ppe/papers/nucsp.ps.g

Bar-Halo Friction in Galaxies II: Metastability

It is well-established that strong bars rotating in dense halos generally slow down as they lose angular momentum to the halo through dynamical friction. Angular momentum exchanges between the bar and halo particles take place at resonances. While some particles gain and others lose, friction arises when there is an excess of gainers over losers. This imbalance results from the generally decreasing numbers of particles with increasing angular momentum, and friction can therefore be avoided if there is no gradient in the density of particles across the major resonances. Here we show that anomalously weak friction can occur for this reason if the pattern speed of the bar fluctuates upwards. After such an event, the density of resonant halo particles has a local inflexion created by the earlier exchanges, and bar slowdown can be delayed for a long period; we describe this as a metastable state. We show that this behavior in purely collisionless N-body simulations is far more likely to occur in methods with adaptive resolution. We also show that the phenomenon could arise in nature, since bar-driven gas inflow could easily raise the bar pattern speed enough to reach the metastable state. Finally, we demonstrate that mild external, or internal, perturbations quickly restore the usual frictional drag, and it is unlikely therefore that a strong bar in a galaxy having a dense halo could rotate for a long period without friction.Comment: 13 pages, 11 figures, to appear in Ap

The Luminous Starburst Ring in NGC 7771: Sequential Star Formation?

Only two of the twenty highly luminous starburst galaxies analyzed by Smith et al. exhibit circumnuclear rings of star formation. These galaxies provide a link between 10^11 L_sun systems and classical, less-luminous ringed systems. We report the discovery of a near-infrared counterpart to the nuclear ring of radio emission in NGC 7771. A displacement between the ~10 radio bright clumps and the ~10 near-infrared bright clumps indicates the presence of multiple generations of star formation. The estimated thermal emission from each radio source is equivalent to that of ~35000 O6 stars. Each near-infrared bright knot contains ~5000 red supergiants, on average. The stellar mass of each knot is estimated to be ~10^7 M_sun. The implied time-averaged star formation rate is \~40 M_sun per yr. Several similarities are found between the properties of this system and other ringed and non-ringed starbursts. Morphological differences between NGC 7771 and the starburst + Seyfert 1 galaxy NGC 7469 suggest that NGC 7771 may not be old enough to fuel an AGN, or may not be capable of fueling an AGN. Alternatively, the differences may be unrelated to the presence or absence of an AGN and may simply reflect the possibility that star formation in rings is episodic.Comment: accepted for publication in The Astrophysical Journal (10 January 1999); 48 pages including 13 figures; AAS LaTe

A Dust-Penetrated Classification Scheme for Bars as Inferred from their Gravitational Force Fields

The division of galaxies into ``barred'' (SB) and ``normal'' (S) spirals is a fundamental aspect of the Hubble galaxy classification system. This ``tuning fork'' view was revised by de Vaucouleurs, whose classification volume recognized apparent ``bar strength'' (SA, SAB, SB) as a continuous property of galaxies called the ``family''. However, the SA, SAB, and SB families are purely visual judgments that can have little bearing on the actual bar strength in a given galaxy. Until very recently, published bar judgments were based exclusively on blue light images, where internal extinction or star formation can either mask a bar completely or give the false impression of a bar in a nonbarred galaxy. Near-infrared camera arrays, which principally trace the old stellar populations in both normal and barred galaxies, now facilitate a quantification of bar strength in terms of their gravitational potentials and force fields. In this paper, we show that the maximum value, Qb, of the ratio of the tangential force to the mean radial force is a quantitative measure of the strength of a bar. Qb does not measure bar ellipticity or bar shape, but rather depends on the actual forcing due to the bar embedded in its disk. We show that a wide range of true bar strengths characterizes the category ``SB'', while de Vaucouleurs category ``SAB'' corresponds to a much narrower range of bar strengths. We present Qb values for 36 galaxies, and we incorporate our bar classes into a dust-penetrated classification system for spiral galaxies.Comment: Accepted for publication in the Astrophysical Journal (LaTex, 30 pages + 3 figures); Figs. 1 and 3 are in color and are also available at http://bama.ua.edu/~rbuta/bars

Kinematics of the outer pseudorings and the spiral structure of the Galaxy

The kinematics of the outer rings and pseudorings is determined by two processes: the resonance tuning and the gas outflow. The resonance kinematics is clearly observed in the pure rings, while the kinematics of the gas outflow is manifested itself in the pseudorings. The direction of systematical motions in the pure rings depends on the position angle of a point with respect to the bar major axis and on the class of the outer ring. The direction of the radial and azimuthal components of the residual velocities of young stars in the Perseus, Carina, and Sagittarius regions can be explained by the presence of the outer pseudoring of class R1R2' in the Galaxy. We present models, which reproduce the directions and values of the residual velocities of OB-associations in the Perseus and Sagittarius regions, and also model reproducing the directions of the residual velocities in the Perseus, Sagittarius, and Carina regions. The kinematics of the Sagittarius region accurately defines the solar position angle with respect to the bar elongation, theta_b=45 (+/-5) deg.Comment: 16 pages, 10 figures, accepted for publication in Astronomy Letter