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

Young Planetary Nebulae: Hubble Space Telescope Imaging and a New Morphological Classification System

Using Hubble Space Telescope images of 119 young planetary nebulae, most of which have not previously been published, we have devised a comprehensive morphological classification system for these objects. This system generalizes a recently devised system for pre-planetary nebulae, which are the immediate progenitors of planetary nebulae (PNs). Unlike previous classification studies, we have focussed primarily on young PNs rather than all PNs, because the former best show the influences or symmetries imposed on them by the dominant physical processes operating at the first and primary stage of the shaping process. Older PNs develop instabilities, interact with the ambient interstellar medium, and are subject to the passage of photoionization fronts, all of which obscure the underlying symmetries and geometries imposed early on. Our classification system is designed to suffer minimal prejudice regarding the underlying physical causes of the different shapes and structures seen in our PN sample, however, in many cases, physical causes are readily suggested by the geometry, along with the kinematics that have been measured in some systems. Secondary characteristics in our system such as ansae indicate the impact of a jet upon a slower-moving, prior wind; a waist is the signature of a strong equatorial concentration of matter, whether it be outflowing or in a bound Keplerian disk, and point symmetry indicates a secular trend, presumably precession, in the orientation of the central driver of a rapid, collimated outflow.Comment: (to appear in The Astronomical Journal, March 2011.) The quality of the figures as it appears in the arXiv pdf output is not up-to-par; the full ms with high-quality figures is available by anonymous FTP at ftp://ftp.astro.ucla.edu/pub/morris/sahai_AJ_360163.pd

HI study of the warped spiral galaxy NGC5055: a disk/dark matter halo offset?

We present a study of the HI distribution and dynamics of the nearby spiral galaxy NGC5055 based on observations with the Westerbork Synthesis Radio Telescope. The gaseous disk of NGC5055 extends out to about 40 kpc, equal to 3.5 R_25, and shows a pronounced warp that starts at the end of the bright optical disk (R_25= 11.6 kpc). This very extended warp has large-scale symmetry, which along with the rotation period of its outer parts (~1.5 Gyr at 40 kpc), suggests a long-lived phenomenon. The rotation curve rises steeply in the central parts up to the maximum velocity (v_max ~ 206 km/s). Beyond the bright stellar disk (R_25), it shows a decline of about 25 km/s and then remains flat out to the last measured point. The standard analysis with luminous and dark matter components shows the dynamical importance of the disk. The best fit to the rotation curve is obtained with a ``maximum disk''. Less satisfactory fits with lighter disks help to set a firm lower limit of 1.4 to the mass-to-light ratio in F band of the disk. Such a ``minimum disk'' contributes about 60% of the observed maximum rotational velocity. NGC5055 shows remarkable overall regularity and symmetry. A mild lopsidedness is noticeable, however, both in the distribution and kinematics of the gas. The tilted ring analysis of the velocity field led us to adopt different values for the kinematical centre and for the systemic velocity for the inner and the outer parts of the system. This has produced a remarkable result: the kinematical and geometrical asymmetries disappear, both at the same time. These results point at two different dynamical regimes: an inner region dominated by the stellar disk and an outer one, dominated by a dark matter halo offset with respect to the disk.Comment: Accepted for publication in A&A. Minor correction

Distribution and Kinematics of the Circum-nuclear Molecular Gas in the Seyfert 1 Galaxy NGC 3227

We present new interferometric observations of the 12CO(1-0), 12CO(2-1) and HCN (1-0) molecular line emission in NGC 3227 obtained with the IRAM Plateau de Bure interferometer (PdBI). We achieved an unprecedented angular resolution in the 12CO(2-1) line of about 0.6'' corresponding to only about 80pc at a distance of 17.3Mpc. The mapped 12CO emission is concentrated in the inner 8'' and accounts for 20% of the total 30m CO line flux. The 12CO emission is resolved into an asymmetric nuclear ring with a diameter of about 3''. The HCN line emission is mostly unresolved at our resolution of ~2.4'' and contains all of the single dish flux. We have decomposed the observed molecular gas motions into a circular and non-circular component revealing that about 80% of the gas in the circum-nuclear region exhibits pure circular rotation. We find evidence for bar streaming onto the nuclear ring and a redshifted emission knot on the ring perimeter. In the central arcsecond the gas shows apparent counter rotation. This behavior can be best explained by a warping of the inner molecular gas disk rather than gas motion in a nuclear bar potential. We detected molecular gas at a distance from the nucleus of only ~13pc with a velocity of about 75 km/s with respect to the systemic velocity and find that within the central arcsecond the rotation curve is rising again. This is the first time that millimetric CO-line emission has been detected interferometrically at such small distances to the nucleus of a Seyfert galaxy. These measurements indicate a lower limit on the enclosed mass of about 2x10^7 M_solar in the inner 15pc.Comment: accepted for Ap.J. April issue, 54 pages, 22 figure

Enhancement of two photon processes in quantum dots embedded in subwavelength metallic gratings

We show a large enhancement of two-photon absorption processes in nanocrystal quantum dots and of light upconversion efficiency from the IR to the near-IR spectral regime, using a hybrid optical device in which near-IR emitting InAs quantum dots were embedded on top a metallic nanoslit array. The resonant enhancement of these nonlinear optical processes is due to the strong local electromagnetic field enhancements inside the nanoslit array structure at the extraordinary transmission resonances. A maximal two-photon absorption enhancement of more than 20 was inferred. Different high field regions were identified for different polarizations, which can be used for designing and optimizing efficient nonlinear processes in such hybrid structures. Combining nanocrystal quantum dots with subwavelength metallic nanostructures is therfore a promising way for a range of possible nonlinear optical devices.Comment: 14 pages, 7 figure

An Imaging Survey of Early-Type Barred Galaxies

This paper presents the results of a high-resolution imaging survey, using both ground-based and Hubble Space Telescope images, of a complete sample of nearby barred S0--Sa galaxies in the field, with a particular emphasis on identifying and measuring central structures within the bars: secondary bars, inner disks, nuclear rings and spirals, and off-plane dust. A discussion of the frequency and statistical properties of the various types of inner structures has already been published. Here, we present the data for the individual galaxies and measurements of their bars and inner structures. We set out the methods we use to find and measure these structures, and how we discriminate between them. In particular, we discuss some of the deficiencies of ellipse fitting of the isophotes, which by itself cannot always distinguish between bars, rings, spirals, and dust, and which can produce erroneous measurements of bar sizes and orientations.Comment: LaTeX, 66 pages (including 42 figures, 36 in color). To appear in The Astrophysical Journal Supplement. Full-resolution and text-only versions available at http://www.iac.es/galeria/erwin/research

Hydrodynamic Simulations for the Nuclear Morphology of NGC 4314

We performed SPH simulations to study the nuclear morphology of a barred galaxy NGC 4314. We have constructed the mass models based on the results of a profile decomposition into disk, bulge, and bar components. Our models have three different nuclear structures according to the assumption about the nuclear bar: no nuclear bar, a synchronous nuclear bar and a fast nuclear bar. Our SPH simulations show that the morphology of the nuclear region of NGC 4314 which is characterized by an elongated ring/spiral of newly formed stars and HII regions, aligned nearly parallel to the primary bar can be understood in terms of the secular evolution driven by the non-axisymmetric potential. The slightly elongated and aligned nuclear ring of NGC 4314 can be formed by the strong barred potential and the moderate central concentration of the bulge mass with and without a nuclear bar. However, the nuclear spiral pattern can not be developed without a nuclear bar. The nuclear bar of NGC 4314 seems to rotate faster than the primary bar since the nuclear morphology induced by the synchronous nuclear bar is much different from the observed one.Comment: 9 page

Worldvolume Uncertainty Relations for D-Branes

By quantizing an open string ending on a D-brane in a nontrivial supergravity background, we argue that there is a new kind of uncertainty relation on a D-brane worldvolume. Furthermore, we fix the form of the uncertainty relations and their dependence on the string coupling constant by requiring them to be consistent with various string theory and M theory dualities. In this way we find a web of uncertainties of spacetime for all kinds of brane probes, including fundamental strings, D-branes of all dimensions as well as M theory membranes and fivebranes.Comment: 19 pages, minor modification on p.