The dynamics of S0 galaxies

Anne Mathieu & Michael Merrifield University of Nottingham anne.mathieu@nottingham.ac.uk ()

A correlation between supermassive black hole mass and galaxy light concentration in bulges

Alister W. Graham IAC agraham@ll.iac.es () The global distribution of stars within elliptical galaxies and spiral galaxy bulges is shown to be intimately related to the mass of their central supermassive black holes. More massive galaxies are not simply bigger versions of less massive galaxies, as had been frequently assumed in the past. Their entire structure is different, such that more massive galaxies are more centrally concentrated. The precise degree of concentration has now been shown to correlate tightly with the mass of the central supermassive black hole. This relation is at least as good, if not better than, the relation between the mass of a supermassive black hole and that of it's host galaxy announced last year (2000). Moreover, it provides what should be useful insight into the formation of both galaxies and their central black holes

The distribution of disks in the $\mu_0$--$\log h$ plane and the inclination correction

Alister W. Graham IAC agraham@ll.iac.es () This presentation reveals that a further fundamental modification needs to be made to the Freeman law, such that not only do LSB galaxies possess fainter central surface brightnesses than the canonical Freeman value, but the upper limit is in fact an upper (bright) `envelope' of points in the central disk surface-brightness - log(scale-length) diagram. A morphological-type dependence in this $\mu_0$--$\log h$ plane of spiral galaxy disks is shown, such that the upper bright envelope is defined by early-type (~$<$Sc) spirals while the late-type spirals have smaller and fainter disks. This realisation has enabled a novel new approach to determining disk opacity.

Gas morphology and dynamics in the central kpc: embedded bars and nuclear spirals

Witold Maciejewski Osservatorio Astrofisico di Arcetri, Italy, and Jagiellonian University Observatory, Poland witold@thphys.ox.ac.uk () High-resolution observations of galactic centers unveiled complex structures residing there: inner bars and spirals are very common. Hydrodynamical simulations and arguments based on the density-wave theory imply that the nuclear spiral is a common response of the gas to a large-scale non-axisymmetric potential. Nevertheless, various distinct fundamental modes of gas flow can exist in galactic nuclei. Gas inflow to the center, enabled by the nuclear spiral, can in other modes be prohibited, with gas accumulating on the nuclear ring. Stellar nuclear bars modify the flow in a way that shows a fine balance between the strength of the bar and the morphology of the inflowing gas. Recent detection of $m=1$ modes in gas flow may indicate that self-gravity plays an important role in the dynamics of the nuclear gas.

hliszt@nrao.edu ()

Morphology of 3D bars

P.A. Patsis Research Center for Astronomy, Academy of Athens ppatsis@cc.uoa.gr () We analyze the orbital structure in a class of 3D models for galactic bars. We examine the changes introduced in the system as the pattern speed, the strength of the bar, and the properties of the central bulge vary. We investigate the building blocks of the 3D bars and in particular those that could give boxy and peanut-shaped edge-on profiles. We find the parameters that favor the formation of secondary 3D bars along the minor axis, as well as disks embedded in the bulge and inclined in respect with the equatorial plane. The boxy isophotes in the face-on views of barred galaxies are also discussed.

Star Formation along the Hubble Sequence: Results from a new Halpha Galaxy Survey

Shane, Neville; James, Phil ASTROPHYSICS RESEARCH INSTITUTE, LIVERPOOL JOHN MOORES UNIVERSITY, UK nss@astro.livjm.ac.uk () We are conducting a large survey of star formation within ~400 nearby (v<3000km/s) spiral and irregular galaxies through imaging of the H-alpha emission. H-alpha emission is produced by high mass, short lived stars and is thus a near instantaneous measure of the current star formation rate. We will present here some of our first results, investigating the variation of star formation rate and luminosity normalised star formation rate along the Hubble Sequence for disk galaxies. Our survey sample has been selected from the Uppsala Galaxy Catalogue to include all observable galaxies out to 3000km/s. Previous studies have concentrated on large, bright galaxies, whereas ours also includes many smaller and less luminous specimens. We are utilizing 14 weeks of time on the 1m Jacobus Kapteyn Telescope on La Palma.

Kinematics of Galaxy Disks

M. Kregel P.C. van der Kruit W.J.G. de Blok K.C. Freeman Kapteyn Astronomical Institute, Groningen, The Netherlands Kapteyn Astronomical Institute, Groningen, The Netherlands ATNF, Sydney, Australia MSSSO, Canberra, Australia kregel@astro.rug.nl () We present observations of the disk kinematics in a sample of edge-on spiral galaxies. For these galaxies we obtained HI synthesis maps using the ATCA and optical absorption line spectra using the SSO 2.3m, the WHT and the VLT. We use the HI data to derive the rotation curves by applying a new least-squares fitting algorithm to the major axis position-velocity maps. The stellar rotation and velocity dispersion are determined from the optical spectra using a cross correlation technique.

Dynamics of Stellar Orbits in Disk Galaxies

Taihei Yano, Kan-ya Yukitoshi, and Naoteru Gouda NAO, Japan yano@pluto.mtk.nao.ac.jp () We have investigated the dynamics of stellar motions in galactic potentials with bar like perturbed potential in order to clarify whether the structures such as 2-armed spiral structures or bared structures are constructed in galaxies. In this investigation, we verify whether the axis of oval orbit align with that of the perturbed potential. When the axis is aligned with the bar the structures will be constructed, and when axis is aligned perpendicular to the bar no structures are constructed. Earn \& Lynden-Bell(1996) introduce the condition that orbits align with the bar around the Lindblad resonance. We consider the more general case, i.e., we discuss how the orbit behaves in all regions of a galaxy. Our results are as follows; When $r/r_{ILR} > 1$, the axis of the oval orbit is aligned with that of the perturbed potential. On the other hand, when $r/r_{ILR} < 1$, the axis of the oval orbit is aligned perpendicular to that of the perturbed potential. Therefore the structures in galaxies appear in the outer region of inner Llindblad resonance. These results are consistent with the linear analysis of eauations of motion.

deborah@astroscu.unam.mx ()

High spectral resolution kinematics of galaxies: the figure of eight effect close to the galaxy's center.

Emanuela Pompei Ezio Pignatelli ESO, Chile Dip. di Astronomia, Univ. di Padova, Italy epompei@eso.org () We present here high spectral resolution observations of stellar and gaseous kinematics of three nearby galaxies. Each of these objects is a clear example of the different kinematical conditions that can be found in galaxies: stars moving faster than gas, gas and stars moving in the same way, gas rotating faster than the stars. The data were then used to investigate the figure of eight effect, which is a clear signature of a bar in an edge-on galaxy, very close to the galaxy's center, successfully identifying a (nuclear?) bar in one the objects observed. Mass models were applied to the data to derive the global gaseous and stellar potential.

The Gasesous Properties of Seyfert Host Galaxies

C.G. Mundell A.R.I. cgm@astro.livjm.ac.uk () Neutral hydrogen (HI) is a key tracer of galactic structure and dynamics and responds most readily to perturbations caused by tidal disturbance and non-axisymetric gravitational potentials. Such perturbations have also been mooted as possible triggers of nuclear activity in galaxies although no conclusive links have yet been established. I present here an HI imaging study of a heterogeneous sample of nine nearby Seyfert galaxies and describe plans for a new HI survey which aims to investigate the role of the host gas in triggering and fuelling of nuclear activity on a statistical basis.

rromano@inaoep.mx ()

Galactic Warps and Bars in Axisymmetric Halos

Makoto Ideta Department of Astronomy, Kyoto University ideta@kusastro.kyoto-u.ac.jp () Dynamical evolution of galactic warps and bars embedded in oblate and prolate halos is examined by using $N$-body simulations. In particular, a configuration such that the symmetry axis of disks is aligned to the short axis of halos is considered. Then, it is found that the warpings in oblate halos disappeared at the end of simulations, while in prolate halos, they can survive for a long time. On the other hands, the bars in oblate halos can last for a long time, while in prolate halos, they dissolved eventually within a Hubble time. This finding suggests that galactic bars would not coexist with galactic warps, and so, there may exist a difference of the frequency of warpings in barred and non-barred galaxies.

Dynamical Modeling of Stellar Nucleus of M31

Niranjan Sambhus S. Sridhar IUCAA, India nbs@iucaa.ernet.in () The peculiar twin peaked nucleus of M31 hosts a supermassive black hole. We present stellar dynamical models of this double-peaked nucleus, based on HST photometry, and Tremaine's model of an eccentric stellar disk in orbit round the supermassive black hole. Using a Schwarzschild-type method, we derive the disk potential from the photometry. We construct stellar orbits in the combined potential of the disk and the supermassive black hole, allowing for the possibility of a non-zero pattern speed for the stellar disk. Model disks are generated by populating these orbits with stars. Comparisions with the available two dimensional photmetric and kinematic maps are presented. Our results support Tremaine's model, extended to include a more massive disk and a non-zero pattern speed.

Density waves in the central kpc of galaxies: the role of nuclear spirals, bars and m=1 modes.

Eric Emsellem CRA-Lyon, France emsellem@obs.univ-lyon1.fr () Density waves in the central kpc of galaxies, taking the form of spirals, bars and/or lopsided density distributions are potential actors of the redistribution of angular momentum. They may thus play an important role in the overall evolution of the central structures, not mentioning the possible link with the active/non-active central mass concentration. I will present kinematical evidences for the presence of such structures using new sets of observations, including two-dimensional (OASIS/CFHT) and long-slit (ISAAC/VLT) spectrography of nuclear bars and spirals. I will also discuss the importance of m=1 modes in the nuclear regions of galaxies, illustrating this with newly revealed cases and original N body simulations. The implications of these observations/models will be discussed in the context of AGN, starburst and dynamical evolution.

The properties of the dense interstellar medium in the central regions of starburst and normal galaxies

S. Huettemeister AIRUB Bochum, Germany huette@astro.ruhr-uni-bochum.de () The physical properties of the dense component of the Interstellar Medium (ISM), i. e. molecular gas, in the centers of galaxies are significantly different from what is found in more quiescent disk regions like spiral arms. The dense ISM in the central part of a galaxy is, on average, both warmer and denser than in the disk, but in detail shows a complex multi-component structure. This may include diffuse, unbound gas, and dense, warm star-forming cores, as well as cool dense cores, depending on whether the central region in question is engaged in a starburst or (relatively) less active. Even among starburst regions, there are very significant differences in the structure and dominating component of the gas, depending on the degree of central concentration, the evolutionary state of the burst and - possibly - the presence of an AGN. Multilevel, multispecies studies of molecular lines, preferably at high resolution, are a powerful diagnostic to derive the structure and physical properties of the gas. A special role falls to the ratio of the CO isotopomers $^{12}$CO and $^{13}$CO, but high-density tracers like HCN, HNC and CN are crucial in showing that not all starburst regions are identical. Using these diagnostics, the changes in gas properties, and therefore the conditions governing star formation, can be traced from the disk through the bar (a frequent ingredient when gas is being concentrated to the center) to the nuclear region. The conditions dominating the gas reflect - and feed back on - kinamatical and secular evolutionary processes in both the disk and the center of a galaxy, making a closer connection of studies of physical and dynamic properties of disk galaxies a worthwhile goal.

Molecular gas in the barred spiral galaxy M83

A. Andersson (1), T. Wiklind (2), H. Olofsson (1), G. Rydbeck (2) (1) Stockholm Observatory, (2) Onsala Space Observatory andreas@astro.su.se () We have mapped the barred spiral galaxy M83 in the CO(1-0) and CO(2-1) lines using the Swedish-ESO Submillimetre Telescope (SEST). The coverage is in both transitions complete out to a radius of 4\farcmin 5 (rougly the extent of the optical disk) and the spacing is 1/3 of the beam width, a basic condition for improving the resolution by use of deconvolution techniques. The CO emission is concentrated to the nucleus, the bar and the arms. The velocity field is regular, with deviations in conneciton with the bar and the arms. After subtracting the axi- symmetric part we find that the residual velocites is spiral shaped and we see indications that the spiral arms are a result of a spiral density wave. We have also observed M83 in infrared (J and K) and we are preparing to model the velocity field and compare the results to the findings above.

Characteristics of the Galaxy's Thick Disk

W.J. Schuster, A. Moitinho, L. Parrao, E. Covarrubias 1-2. - Observatorio Astronomico Nac., UNAM, Mexico 3. - Instituto de Astronomia, UNAM, Mexico 4. - UDLA, Puebla, Mexico schuster@astrosen.unam.mx () $uvby-\beta$ photometry has been obtained for more than 2100 high-velocity and metal-poor stars. Although our original intent was the study of the Milky Way's halo, many of these program stars are from the Galaxy's old-thin and thick disks, permitting us to study and compare these different stellar populations. Many of these stars are also found in the Hipparcos catalogue, and a new photometric calibration for the absolute visual magnitudes of metal-poor stars is being developed. This new calibration plus kinematic data gleaned from many data bases is allowing us to study the kinematic characteristics of the thick disk in comparison with the halo and old thin-disk stellar populations. Here are shown the characteristics of our new photometric absolute-magnitude calibration plus various kinematic diagrams comparing the thick disk of the Galaxy. In the future the $uvby-\beta$ photometry will be compared to stellar isochrones to derive, study, and compare the ages of thick-disk stars.

Three dimensional HI gas distribuiton in Milkyway Galaxy

Hiroyuki Nakanishi, Yoshiaki Sofue Institute of Astronomy, University of Tokyo hnakanis@ioa.s.u-tokyo.ac.jp () We derived a new three dimensional map of neutral hydrogen gas (H {\sc i}) in our Galaxy using the latest H {\sc i} survey data cubes and rotation curve. The H {\sc i} disk extends as far as 23 kpc, and its size is 1.6 times larger than that of the stellar disk. H {\sc i} mass is $5.5 \times 10^9 M_\odot$, which is 3\% of the dynamical mass. Though it is believed that the Galaxy has some spiral H {\sc i} arms, we found the Galaxy has three H {\sc i} rings rather than spiral arms. The most noticeable feature is a very large H {\sc i} ring at 17 kpc. It has very high column density and has 64 \% of the total H {\sc i} mass. It strongly warps from $z \simeq -1$ kpc to $\simeq +1.5$ kpc. The middle ring locates at around $R = 13$ kpc and has 27 \% of total H {\sc i} mass. This ring corresponds to so-called Outer arm. The smallest ring locates at around $R=8$ kpc and has 11 \% of the total H {\sc i} mass. This ring corresponds to a complex of Sagittarius arm and Perseus arm. One possible interpretation of 17 kpc ring is that the spatial mass density is not high enough for star formation in it, and the primordial H {\sc i} gas remains. In addition we found that the H {\sc i} gas is lacking at $R=10$ kpc. This radius coincident with the corotation radius if the pattern speed of about 20 km s$^{-1}$ pc$^{-1}$is assumed.

Instabilities and Modes of Collisionless Disks

Christopher Hunter Florida State U. hunter@math.fsu.edu () \documentstyle{article} \begin{document} \title{Instabilities and modes of collisionless stellar disks} \author{C. Hunter \\ Florida State University, Tallahassee, Florida 32306-4510, USA} \maketitle \begin{abstract} Oscillations of flat collisionless stellar disks are described by a linearized perturbational analysis of the collisionless Boltzmann equation. The orbits in a circularly symmetric disk are regular, and have well-defined action and angle variables. Kalnajs (1971,1976) showed how their responses to perturbations can be determined, and gave a compact matrix method for solving self-consistently for the oscillations of a disk which is composed of a population of orbits. There have been few implementations of this method for stellar disks since then. The most successful have been to singular scalefree disks (Zang 1976, Evans \& Read 1998). This talk will discuss some new approaches to the implementation, and describe some numerical results for disks with a simple non-singular rotation curve. This work has been supported by NSF through grants DMS-9704615 and DMS-0104751. \end{abstract} \end{document}

Magnetic fields in spiral arms and bars

Rainer Beck MPIfR Bonn, Germany rbeck@mpifr-bonn.mpg.de () Linearly polarized radio continuum emission is a powerful tool to study the strength and structure of interstellar magnetic fields in galaxies. Interstellar magnetic fields with a well ordered spiral structure exist in grand-design, flocculent and even irregular galaxies. In grand-design galaxies the fields are aligned parallel to the optical spiral arms, but the strongest regular fields are found in interarm regions, sometimes forming ``magnetic spiral arms'' between the optical ones. Within the optical spiral arms, processes related to star formation tangle the fields so that very little polarization is observed. Faraday rotation of the polarization vectors reveals patterns which support the existence of coherent large-scale fields in galactic disks generated by dynamos. The majority of field structures in galaxies cannot be described by one single dominating dynamo mode, but requires a superposition of modes. In a few galaxies an axisymmetric spiral field (the ground mode of dynamo action) dominates. As the inward direction is favoured, some special symmetry of the seed field is needed. The first radio polarization survey of barred galaxies is presented, observed with the VLA and the ATCA. The magnetic field is mostly aligned with the gas flow around the bar, except for the upstream region where the magnetic field structure deviates from that expected from hydrodynamical models. Within (and interior to) the circumnuclear ring the field is again of spiral shape, indicating dynamo action, which leads to magnetic stresses, possibly driving an inflow of gas towards the active nucleus. Present-day radio polarization observations are limited by sensitivity. Next-generation radio telescopes (e.g. the Square Kilometer Array) will be able to reveal the full wealth of magnetic structures in galaxies.

Bar dynamical friction and disk galaxy dark matter content

Victor P. Debattista Astronomiches Institut, Universitat Basel, Switzerland debattis@astro.unibas.ch () I discuss recent results, both theoretical and observational, on the pattern speeds of bars and what they tell us on the dark matter content of their galaxies.

High Resolution Radio Continumm Observatins of the Barred Spiral Galaxy NGC 3367

J.Antonio Garcia-Barreto J. Franco L. Rudnick IA-UNAM, INAOE, Mexico IA-UNAM, Mexico U. Minnesota tony@inaoep.mx, tony@astroscu.unam.mx () New observations of the radio continuum emission from the barred spiral galaxy NGC 3367 at 1.4 GHz, with an angular resolution of 2$''.1$ and at 8.4 GHz with an angular resolution of $0''.28$ are presented. In the map at 1.4 GHz, the triple source: a central radio source in addition to two lobes straddling the center, was primarily detected as in previous $4''$ observations. The central radio source connects with the south-west lobe with a projected structure of approximately 2.5 kpc long by approximately 850 pc wide, forming a jet. The map at 8.4 GHz shows a circumnuclear structure located within a radius of about 300 pc, most likely associated with regions of recent star formation, a compact unresolved source (smaller than 65 pc in diameter) from the center of the galaxy. The compact core, jet and lobes form a small, low power counter part to radio galaxies with a flow axis which is out of the plane of the galaxy. The circumnuclear structure is believed to be in the plane of the galaxy and it is most likely the result of galactic dynamics under a non- axisymmetric gravitational potential.

Dynamical evolution of M92 Globular Cluster - Proving the Milk-Way disk-shocking

M.R. de Oliveira, A. Fausti, H. Dottori, R.R. de Carvalho OBSPM, France UFRGS, Brasil ON, Brasil marcio.oliveira@obspm.fr () Treecode N-body numerical simulations are used to study the dynamical evolution of the globular cluster M92 in the Galaxy gravitational field during the last two Gyr, which corresponds to aproximately 16 perigalactic transits. We obtained the dynamical initial conditions two Gyr ago, by letting a particle evolve in the galactic potential from its present position and inverting the observed spatial velocity vector of the cluster. The cluster was modelled with 16384 particles covering a mass spectrum from 0.1-1.2 M$_{\odot}$, initially distributed in a Plummer model with a half mass radius of 1.5\,pc and a equivalent King tidal radius of 10\,pc. During the simulation we observe the appearance of several hundreds of parsecs of long tidal tails, which tend to align with the cluster orbit. The model reproduces quite well the observed density profile and surface density map recently obtained, including the isodensities orientation. The model points to a cluster upper limit mass loss r ate of $\simeq 6\%$ per Gyr. Over the 2 Gyr covered by this simulation the cluster halo tends to swell and the core to shrink.

sellwood@physics.rutgers.edu ()

Spiral Structure observed in Near-Infrared

P.Grosbol ESO, Germany pgrosbol@eso.org () Near-infrared observations of the spiral pattern in galaxies reveal the underlying density perturbations in the disks much better than maps in visual bands although some population effects are still present. A preliminary analysis of the spiral structure in 50 nearby spiral galaxies observed in the K band with SOFI/NTT is presented including the distribution of arm amplitudes and pitch angles. Synthetic rotation curves were derived using the K surface photometry and HI velocity width data. The extent of the main, symmetric spiral pattern was compared to radial separations between resonances derived from the rotation curves in order to find possible pattern speeds for an underlying density wave. The dynamic implications of this comparison are discussed.

Nested Bars, Inner Disks, and Nuclear Rings in Barred Galaxies

Peter Erwin IAC, Spain erwin@ll.iac.es () I present results of a high-resolution imaging survey of barred S0--Sa galaxies which show the central regions of these galaxies are surprisingly complex, and often dominated by dynamically cool components. In particular, inner bars -- secondary, small-scale bars (typically less than a kiloparsec in radius) located inside of, and probably rotating faster than, the large-scale primary bars -- are present in about one quarter to one third of all such galaxies. A third of SB0's appear to host kiloparsec-scale \textit{disks} within their large-scale bars; but the frequency of such inner disks appears to be much lower for later Hubble types. In addition, there are three examples of purely \textit{stellar} nuclear rings --- possibly the fossil remnants of past circumnuclear starbursts. I also comment on results from an ongoing analysis of about 45 known double-barred systems (extending to Hubble types as late as Sbc), and discuss their characteristic sizes, orientations, and implications for the formation and evolution of these structures.

Fitting a Galactic Model to an All-Sky Survey

Jeffrey A. Larsen and Roberta M. Humphreys Larsen - Lunar and Planetary Laboratory, Univ. of Arizona Humphreys - University of Minnesota roberta@aps.umn.edu () We use star counts from the APS Catalog of the POSS I to develop a galactic model optimized for large, statistically significant datasets uniformly distributed over the sky. We have selected an 88 field subset, 16 square degrees each, from the catalog for a program of magnitude limited star counts. We have developed a simple three component (disk, halo, thick disk) model optimized for efficiently and objectively analyzing the star count data. Our model not only produces model counts for our multi-directional data but also returns a ``goodness of fit" statistic. We use a genetic algorithm, a robust optimization technique well-suited for this large multi-directional and multiple parameter study, to optimize the fit and derive a self consistent set of global parameters to model the galaxy. The results from 12 independent executions or trials yielded consistent results. All of the model fits produced a flattened inner halo with c/a of 0.5 to 0.6. The radial scale length of the disk and the density normalization to the plane for the thick disk and halo are consistent with previous work. Our model results all yielded a scale height for the thick disk of 900 pc. The most surprising results from these global fits, are relatively high values ( greater than 4 kpc) for the de Vaucouleurs radius for the halo and the radial scale length of the thick disk. The radial scale length for the thick disk is significantly larger than that for the old/thin disk and if confirmed with additional work, may imply an independent origin for the thick disk. We also present evidence that the scale height and normalization of the thick disk may be variable with direction.

A Large Asymmetry in the Distribution of Faint Stars in the Inner Galaxy

Jennifer E. Parker, Dr. Roberta M. Humphreys, Dr. Jeffrey A. Larsen Parker & Humphreys - University of Minnesota, USA Larsen - Lunar Planetary Lab, University of Arizona, USA parker@astro.umn.edu () Larsen and Humphreys [1996] reported evidence for a significant asymmetry in the number of faint blue stars on either side of the line to the Galactic center from l = �20� to �45� at b = +30�, with significantly more stars observed in the first quadrant. We present a more complete survey of the faint stars on either side of the Sun-Center line, analyzing star counts from 40 paired POSS I fields from l = � 20� to � 75� and b = +20� to +50�. Using a galactic model, GALMOD [Larsen and Humphreys, 2001], we sampled color ranges to distinguish between halo/thick disk and disk stellar populations. Our analysis shows that the observed stellar excess increases with fainter magnitudes and is comprised of mainly halo/thick disk stars. It is possible the excess in star counts could be due to a bar-induced "wake", a disk interaction from a merger or that the asymmetry is an indication that the thick disk/inner halo is triaxial. A "wake" would suggest that the asymmetry is also present below the plane, so we are investigating 40 additional fields below the galactic plane. Spectroscopic observations have also been made using both the CTIO 4meter and the KPNO WYIN 3.5 meter telescopes with HYDRA a multiobject spectrograph. Over 1000 spectra are currently being analyzed to determine the nature and kinematics of the stars responsible.

The Connection Between Star Formation and Resonant Dynamics in Early-Type Disk Galaxies

R. Buta University of Alabama buta@sarah.astr.ua.edu () Resonance rings are remarkable for the idiosyncrasies of their shapes, relative bar orientations, and star formation characteristics. However, there has been little investigation of the full meaning of these idiosyncrasies. In this presentation, I would like to resurrect some earlier observations of the distribution of HII regions in early-type barred galaxies and highlight how the distribution of star formation in resonance rings likely connects to periodic orbit shapes but, surprisingly, not to bar strength. If an inner ring has an intrinsic axis ratio of 0.7 or less, it will show HII regions "bunched up" near the ring major axis, while a round ring will show a more uniform azimuthal distribution of H-alpha flux. However, two galaxies with widely different intrinsic ring shape can have the same bar strength. I will discuss possible interpretations of these effects. I will also discuss recent HST observations of two dissimilar resonance ring galaxies, NGC 3081 and NGC 4622. NGC 3081 is a classic, well-studied resonance ring barred galaxy with an intense inner ring of star formation. The new HST observations resolve the ring into many point or near-point sources. The distribution of these sources is tied directly to the bar in that most are located around the ends of the bar. The luminosity function of the sources depends on azimuth in the sense that the brightest sources are 1 mag brighter near the ends of the bar than near the bar minor axis. Star formation is intimately connected with resonant dynamics in this galaxy. NGC 4622 is a nonbarred resonance ring galaxy with leading spiral structure and whose inner ring is probably tidally-driven. The galaxy is well-known for showing two sets of spiral arms, a pair of outer arms opening outward in the clockwise direction, and a single inner arm opening in the opposite sense. In my presentation, I will reveal the surprising conclusion that the HST data lead us to when we ask which set of arm(s) is leading in NGC 4622. The issue has been an open question for years due to the low inclination of the galaxy, and the interpretation depends also on a on a groundbased velocity field which I will show. I will also discuss the star formation in the peculiar tidal resonance ring. Evidence for an interaction will also be presented.

The de Vaucouleurs Atlas of Galaxies

R. Buta (1), H. G. Corwin, Jr. (2), S. C. Odewahn (3) (1) University of Alabama, (2) IPAC, (3) Arizona State University buta@sarah.astr.ua.edu () In 1959, Gerard de Vaucouleurs published a galaxy classification system (Handbuch der Physik, 53, 275) that is still widely used by modern astronomers. His system was a revision of an earlier one by Hubble (1926, ApJ, 64, 321), but his point of view had a number of advantages over Hubble. De Vaucouleurs' classification system provided a better description of what a galaxy looks like without being too unwieldy. His approach gave greater emphasis and more accurate recognition to specific details that have a bearing on the way galaxies evolve. He published large catalogues summarizing classifications and other basic information for tens of thousands of bright galaxies. These advantages have made de Vaucouleurs' system the most-used galaxy classification system today. However, a major disadvantage of his system is that no galaxy atlas has ever been prepared that illustrates his notation and point of view. This means that most astronomers use the de Vaucouleurs system without really understanding it. We are preparing a new galaxy atlas that will document the de Vaucouleurs revised Hubble galaxy classification system with modern digital images. The principal goals are to make the de Vaucouleurs revised Hubble system more accessible and more understandable to modern astronomy researchers, students, and amateurs, and to summarize what has been learned about the features defining galaxy morphology since the 1950s. The atlas will also address other aspects of morphology that have come to the forefront since de Vaucouleurs published his system and will be up-to-date on our understanding of the physical processes that underly galaxy morphology. Finally, by exclusively using images from electronic detectors, it will be the first major galaxy atlas geared to illustrating classical galaxy types using today's standard imaging methods, as opposed to photographic plates. The need for the atlas is becoming increasingly felt as modern technology provides more and more high quality images of galaxies seen from a vast range of distances and times. It is expected that the morphology of galaxies would undergo significant changes during their formative period, and it is likely that very distant galaxies are showing the structures they had before a steady state had been achieved. The great value of the proposed atlas will be in the description it will provide of normal galaxies in equilibrium, where gravity has run its course and things have for the most part settled down. This poster will summarize the scope and needs of the atlas, and will be used to seek input from the astronomical community as to what will be most useful and, most importantly, to locate as many high quality images as we can find. More details on the project can be found at http://bama.ua.edu/~rbuta/gvatlas/.

The Molecular Gas Distribution in Polar Ring Galaxies

E.Schinnerer, N.Z. Scoville CalTech, USA CalTech, USA es@astro.caltech.edu () Polar ring galaxies are peculiar objects with rings of $\sim$ 10 to 25~kpc diameter which are oriented almost perpendicular to the main stellar disk. In the generally accepted picture, a pre-existing S0 galaxy captures a satellite galaxy, or accretes material located between interacting galaxies. Recently a much more violent formation process was suggested: a galaxy merger between two disk galaxies. In order to distinguish between these scenarios, we mapped the molecular gas distribution in two representative polar ring galaxies (NGC~660 and NGC~2685) using the Owens Valley Radio Observatory (OVRO) millimeter array. NGC~660 is the only late-type galaxy among the known polar ring galaxies. Our recent observations of the molecular gas content suggest the presence of a molecular gas spiral out to 5.5~kpc in the disk. Within the central gas concentration at radius $\leq$ $330~pc$ strong streaming motions are seen, suggesting the presence of a stellar bar. NGC~2685 which is one of the few kinematically confirmed polar ring galaxies shows CO line emission associated with the HII regions in the polar ring but no line emission is detected in the host S0 disk.

N-body simulations of resonance rings

Rautiainen, Pertti and Salo, Heikki and Laurikainen, Eija Department of Physical Sciences, Astronomy Division, University of Oulu, Finland pertti.rautiainen@oulu.fi () We have studied formation of resonance rings in N-body simulations of barred galaxies. The gas component is modeled as inelastically colliding particles. These models often have several modes: primary and secondary bars and/or outer spiral structure, each with separate pattern speed. Even when several modes are present, the rings are usually related to resonances. However, the shapes of the rings can exhibit cyclic changes depending on the relative orientation of the modes. For example, a nuclear ring can follow the orbit loops introduced recently by Maciejewski and Sparke. Multiple modes can also explain misaligned rings found in some galaxies. We also found that some rings can be related to resonances induced by almost steadily rotating spiral arms.

Old stellar Galactic disc in near-plane regions according to 2MASS: scalelengths, cut-off, flare and warp

M Lopez-Corredoira A Cabrera-Lavers F. Garzon IAC, Spain acabrera@ll.iac.es () By using two different methods, we analyze the stellar old population in the near infrared data on the Galactic plane of the 2MASS survey. The first method is based on the isolation of the red clump giant population and the inversion of its star counts to obtain directly the density distribution along the line of sight. The second method is a fitting of the parameters of a disc model on the star counts in 820 regions. Results from both independent methods are consistent with each other. The qualitative conclusions are that the disc is well fitted by an exponential distribution along both the galactocentric distance and height. There is not an abrupt cutoff in the stellar disc (at least within $R<15$ kpc). There is a strong flare, i.e. an increase of scaleheight towards the outer Galaxy; this flare does not begin in the solar circle but it continues toward the inner Galaxy, i.e. there is a decrease of the scaleheight towards the inner Galaxy. Another remarkable fact is the existence of a warp in the old stellar population whose amplitude is coincident with the amplitude of the gas warp. All this information is quantified too.

none

edo@astro.rug.nl ()

Mass Concentration and Bar Dissolution in Spiral Galaxies

M.Das, P.J.Teuben, S.N.Vogel, M.W.Regan, K.Sheth, A.Harris Authors 1,2,3,6 : University of Maryland, USA Author 4 : STSci ,USA Author 5 : Caltech, USA mousumi@astro.umd.edu () Gas inflow in barred galaxies results in mass accumulation in the centers of these galaxies, which affects the shape of the orbits supporting the bar structure. Simulations of bars predict that the bar ellipticity decreases with the mass buildup in the center and can eventually lead to bar dissolution. We have used the near IR and CO data of the BIMA Survey of Nearby Galaxies (SONG) to investigate whether there is observational evidence that bar ellipticity decreases with the central mass concentration. We have used the CO rotation curves to determine the ratio of the dynamical mass within the bulge to that in the bar; this is a measure of the mass concentration. The bar isophotes in the near IR images were used to determine the bar axes and the ellipticity; the intensity profile was used to determine the bulge diameter. Our results show that there is a significant negative correlation between bar ellipticity and central mass concentration. This is the first observational evidence that bar ellipticity decreases with nuclear mass; it may indicate that the central mass buildup in bars results ultimately in the dissolution of the bar itself.

Midplane Stellar Orbits and Mass distribution in the Presence of 3D Spiral Arms

Barbara Pichardo, Marco Martos, Edmundo Moreno y Julia Espresate Instituto de Astronomia, UNAM barbara@astroscu.unam.mx () We have modeled galactic spiral arms as a superposition of inhomogeneous oblate spheroids, and added its contribution to an axisymmetric model of the Galactic mass distribution. The strength, angular speed, pitch angle, central density of the spiral arms, and the spatial extent of the adopted spiral density pattern, were selected within a range of possibilities suggested by observations and, mostly, theory, giving us a plausible model for the Galactic potential outside the inner Lindblad resonance. A given locus for the spiral pattern as delineated by HII regions, was assumed; this results in a pitch angle that is consistent with local measurements. With this pitch angle, self-consistent spiral arms models terminate at the 4/1 resonance, as predicted for Contopoulos and Grosb{\o}l for strong spirals. Then our Galaxy is seemingly much closer to a strong spiral than to a weak spiral and nonlinear theory applies. Orbits in the Galactic plane are analyzed in the non-inertial reference frame of the spiral arms, and also followed in the inertial frame with origin at the Galactic center. Defining in an inertial frame the sense of orbital motion around the Galactic center gives a clean separation of prograde and retrograde orbits in a Poincar\'e diagram. Orbital chaos begins to manifest in the prograde region if we increase the mass in the arms and/or its pitch angle. According to our exploration, the Sun's orbit might conceivably lie in a region of chaotic behavior. Even in the weak regime, the orbital structure is clearly modified from that obtained in models in which the spiral structure is not considered, or in which its contribution to the total potential is represented as a perturbing, simple periodic term. In general, the full integration of the force indicates that the usual local approximation for the arms perturbation is not valid.

Simulations of the Magellanic System: Internal Structure of the Clouds

irapuan@discovery.saclay.cea.fr () Much of our understanding of the nature of the interaction between the Magellanic Clouds and our own Galaxy has emerged from numerical simulations. Features like the Magellanic Stream, the inter-cloud region and the Wing are thought to be produced by the tidal interaction among the members of this triple system. Here I use a TREESPH code to simulate self-consistently the Large and Small Magellanic clouds orbiting a fixed potential representing our Galaxy. The orbital reconstruction, galaxy models models and initial conditions are based on the observational constrains (morphology and kinematics in various wavelengths, proper-motions, distribution of different stellar types and gas), however a considerable amount of free parameters remains unconstrained, and a great number of simulations is required. A large number of simulations have already been run. This is an ongoing work, whose main objective is to study the development of the internal structure of the clouds and inter-cloud region, to find the dynamical parameters responsible, for example, by the formation of the off-centered bar in the LMC or its external ring-like structure.

Comparing Molecular Gas and Star Formation Properties in the Central Regions of Barred and Unbarred Spirals

K. Sheth, S.N. Vogel,P.J. Teuben, A.I. Harris, M.W. Regan, M.D. Thornley (1)Caltech (2,3,4) U. Maryland (5) StScI (6) Bucknell University kartik@astro.caltech.edu () A comparative study of the molecular gas properties and associated star formation activity in the 44 galaxy sample from the BIMA Survey of Nearby Galaxies shows striking differences between barred and unbarred spirals. The mean nuclear molecular gas surface density of barred spirals ($\langle$$\Sigma_{nuc}$$\rangle$=309$\pm$71 \Msun\ pc$^{-2}$) is three times higher than that of unbarred spirals ($\langle$$\Sigma_{nuc}$$\rangle$=107$\pm$29 \Msun\ pc$^{-2}$). Nine out of the eleven bars with $\Sigma_{nuc} >$ 300 \Msun\ pc$^{-2}$ are early types. Thse differences mirror the differences in star formation activity noted by earlier studies. Our sample shows that above a $\Sigma_{nuc} >$ 100 \Msun\ pc$^{-2}$, the star formation rate typically scales with the gas surface density (Schmidt law), but there are notable exceptions where star formation appears to be inhibited despite overwhelmingly large $\Sigma_{nuc}$. Below 100 \Msun\ pc$^{-2}$, the estimated star formation rates are higher than expected. We will discuss plausible reasons for these results. We have also confirmed the main finding of the NRO-OVRO survey that barred spirals are more centrally concentrated than unbarred spirals. The median value of the concentration parameter for barred spirals (f$_{con}$=$\Sigma_{nuc}$/$\Sigma_{disk}$=27.7) is a factor of four higher than that for the unbarred spirals (f$_{con}$=6.2). These data further implicate the large scale bars in transporting large amounts of molecular gas to the center.

Simulations of the Magellanic System: Internal Structure of the Clouds

Irapuan Rodrigues CEA-Saclay / Fellow of the brazilian CNPq irapuan@discovery.saclay.cea.fr () Much of our understanding of the nature of the interaction between the Magellanic Clouds and our own Galaxy has emerged from numerical simulations. Features like the Magellanic Stream, the inter-cloud region and the Wing are thought to be produced by the tidal interaction among the members of this triple system. Here I use a TREESPH code to simulate self-consistently the Large and Small Magellanic clouds orbiting a fixed potential representing our Galaxy. The orbital reconstruction, galaxy models models and initial conditions are based on the observational constrains (morphology and kinematics in various wavelengths, proper-motions, distribution of different stellar types and gas), however a considerable amount of free parameters remains unconstrained, and a great number of simulations is required. A large number of simulations have already been run. This is an ongoing work, whose main objective is to study the development of the internal structure of the clouds and inter-cloud region, to find the dynamical parameters responsible, for example, by the formation of the off-centered bar in the LMC or its external ring-like structure.

Numerical Simulations of Disk Galaxy Formation

Julio F. Navarro University of Victoria Canada jfn@uvic.ca () I will present our latest results concerning simulations of galaxy formation in a hierarchically clustering universe. I will emphasize recent progress on the viability of Cold Dark Matter on the scale of individual galaxies. In particular I plan to concentrate on issues concerning dark matter halo substructure, the evolution of galaxy disks in realistic CDM halos, and the origin of disk galaxy scaling laws.

Pattern Speed of Bars

Joris Gerssen Space Telescope Science Institute gerssen@stsci.edu () The key parameter of any barred galaxy model is its pattern speed. Most determinations of this crucial parameter have relied on indirect measurements by either identifying morphological features with resonances or by modelling kinematical data sets such as velocity fields. A direct, non-model dependent, method to trace the pattern speed of a bar has been developed by Tremaine and Weinberg (1984). We present the results of an application of this method to five barred galaxies and conclude that all bars in this sample are consistent with being fast rotators. The apparent lack of bar deceleration in these five galaxies suggests that they cannot have centrally-concentrated dark matter halos.

The Intrinsic Ellipticity of Spiral Disks

Andersen, D.R.$^{1,2}$, Bershady, M.A.$^{3}$ 1. Penn State University 2. MPIA Heidelberg 3. UW-Madison andersen@astro.wisc.edu () We present estimates of the intrinsic ellipticity for a sample of 25 relatively face--on spiral disks based on H$\alpha$ velocity fields and $R$ and $I$-band imaging. We show how differences between kinematic and photometric inclination and position angles can be used to determine the intrinsic ellipticity of galaxy disks. Our findings suggest disks span a range of ellipticities from $\epsilon= 0$ (circular) to $\epsilon=0.2$. If galaxies in Tully-Fisher studies have a similar distribution of disk ellipticities, this would account for roughly 50\% of the scatter in the Tully--Fisher relation.

oyam@inaoep.mx ()

palacios@inaoep.mx ()

Velocity Fields of Disk Galaxies

Peter Teuben University of Maryland, College Park, MD, USA teuben@astro.umd.edu () In this talk an overview will be given on how velocity fields for disk galaxies are derived and interpreted. Some recently developed techniques will also be discussed, and applied to the BIMA Survey of Nearby Galaxies (SONG). Influences of bars, spiral arms, and oddly shaped halos will be contrasted and identified.

Global properties of disks from the Flat Galaxy Catalog

I.D.Karachentsev {1}, V.E.Karachentseva {2}, Yu.N.Kudrya {2}, S.N.Mitronova {1}, and S.L.Parnovsky {2} {1} Special Astrophysical Observatory, Russian Academy of Sciences, {2} Astronomical Observatory, Kiev State University ikar@luna.sao.ru () We discuss optical, NIR and HI properties of thin edge-on galaxies from the Revised Flat Galaxy Catalog. The RFGC covers the entire sky and contains 4236 galaxies with blue angular diameters a_25 > 0.6 arcmin and apparent axial ratios a/b > 7. About 1000 of them have been observed with the Arecibo radio telescope and the 6-m optical Russian telescope. The blue LF of the galaxies is described by Shechter's function with alpha = -1.14 and M^* = -20.1. The basic parameters of the galaxies: linear diameter, surface brightness, axial ratio, hydrogen mass-to-luminosity ratio, and total mass-to-luminosity ratio are considered as a function of their morphological type and rotation amplitude. There is a linear correlation between the HI mass of the galaxies and their angular momentum expected when the gaseous disks of dwarf and giant spirals are situated near the boundary of gravitational instability favoring star formation. The local relative number of flat galaxies with apparent axial ratios a/b > 7 is 1/17. Being compared with a fraction of flat galaxies in the Deep HST fields, it can give us information about a rate of secular evolution of disks.

Unveiling the behavior of the ionized gas in nearby irregular galaxies

Margarita Valdez-Gutierrez (1,2), Margarita Rosado (2), Leonid Georgiev (2), Ivanio Puerari (1), Jordanka Borissova (3), Radostin Kurtev (3), Lorena Arias (1) (1) INAOE, Mexico (2) IA-UNAM, Mexico (3) Sofia, Bulgaria mago@inaoep.mx () We present the first results of a long term project devoted to study the interrelationship between gas and stars in nearby irregular galaxies. In particular, our results focused on the kinematics and dynamics of the ionized gas of NGC 4449 and IC 1613 are highlighted.

The gravitational torque of bars

D.L. Block (1), I. Puerari (2), J.H. Knapen (3,4), B.G. Elmegreen (5), R. Buta (6), S. Stedman (4), D.M. Elmegreen (7) (1) Wits University, South Africa (2) INAOE, Mexico (3) INGT, Spain (4) University of Hertforshire, UK (5) IBM Research Division, USA (6) University of Alabama, USA (7) Vassar College, USA puerari@inaoep.mx () We determined the relative bar torques of 45 galaxies observed at K-band with the 4.2m William Hershel Telescope. The relative bar torque is calculated by transforming the light distributions into potentials and deriving the maximum ratios of the tangential forces relative to the radial forces. We found that the relative bar torque correlates only weakly with the optical bar type listed in the Revised Shapley-Ames and the de Vaucouleurs systems. In fact, some classically barred galaxies have weaker relative bar torques than classically unbarred galaxies. Applications to the bar torque measurement to the high-redshift universe are briefly discussed.

The Spatial Distribution of the Star Formation in (S+S) Binary Galaxies

H.M. Hernandez-Toledo (1), I. Puerari (2) and C. Conselice (3) (1) Instituto de Astronomia, UNAM, Mexico (2) INAOE, Mexico (3) Space Telescope Science Institute, USA puerari@inaoep.mx () We report some preliminary results of a photometric study of the spatial distribution of the Star Formation in (S+S) Binary Galaxies from the Catalogue of Isolated Pairs of Galaxies, Karacehntsev (1972)

The Milky Way

Walter Dehnen MPIA, Heidelberg dehnen@mpia.de () In this review talk, I am going to give an overview about our observational picture of the Milky Way as a galaxy and compare it with disk galaxies in general. The Milky Way can be observed in much greater detail than any other galaxy and hence plays a crucial role in our understanding of galaxy formation in general and the formation of luminous spiral galaxies in particular.

Bloated Dwarfs: The Thickness of the HI Disks in Irregular Galaxies

Elias Brinks Departamento de Astronomia Universidad de Guanajuato Mexico ebrinks@astro.ugto.mx () Somewhat counterintuitively, the gas disks of irregular galaxies, such as Holmberg~II, Holmberg~I, or DDO~47, are thicker than those of much larger, normal disk galaxies, both in relative as well as in absolute terms. In retrospect, this is easily understood. The velocity dispersion of the gas throughout galaxy disks is regulated by the star forming activity and is of the same order, 6--9 km\,s$^{-1}$, in dwarf galaxies as in spirals. The gravitational potential of irregulars is considerably smaller, though, with as a result a thicker or puffed--up disk, at least as far as the neutral gas as traced in HI is concerned. I will explain several methods which can be used to derive the scaleheight of the gas in irregular galaxies and discuss the consequences a puffed--up disk has on the possible escape of metals into the halo as a result of supernova explosions within OB associations. I will also comment upon how a puffed--up disk increases the cross section of irregular galaxies, increasing the probability for intercepting lines of sight towards QSOs, and how the shape of the gas disks can be used to constrain, in principle, their dark matter content.

The 3D structure of the Galactic bulge from the MACHO red clump stars

Roger Fux(1), Tim Axelrod(1), Piotr Popowski(2) (1) RSAA/ANU, Australia (2) LLNL, USA fux@mso.anu.edu.au () The MACHO experiment has collected $V$ and $R$ band stellar photometry within a roughly $8^{\circ}\times 8^{\circ}$ area of the Galactic bulge centred on $(l,b)\approx(4^{\circ},-6^{\circ})$. These data and additional new $I$ band observations are used to recover the 3D structure of the bulge/bar as mainly traced by the $\sim 3\cdot 10^6$ red clump stars enclosed in this region.

Arm vs. interarm star formation processes in disk galaxies

J.H. Knapen(1, 2) & S. Stedman(2) (1) ING, Spain (2) Univ. Hertfordshire, UK knapen@ing.iac.es () We present first results of an ambitious study aimed at determining the relative prominence of star formation in arm versus interarm regions in spiral disks and as a function of radius. We have collected $B, I$, near-IR $K'$, and H$\alpha$ imaging of a complete sample of 57 spiral galaxies of all types. We will show the characteristics of this data set and outline how parameters describing the young and old stellar populations are obtained across the different disk components, concentrating on bars and spiral arms.

Radial structures of galactic disks

M. Pohlen, R.-J. Dettmar, R. L"utticke AIRUB Bochum, Germany pohlen@astro.ruhr-uni-bochum.de () We will present the results from our new deep imaging survey on a morphologically selected sample of about 70 edge-on disk galaxies. We will address the question of the global structure of galactic stellar disks especially the radial surface brightness profiles at large galactocentric distances. We find that the radial profiles are better described by a two-slope exponential profile, characterized by an inner- ($h_{in}$) and outer- ($h_{out}$) scalelength separated at a break radius $R_{b}$, rather than a sharp truncated exponential. The position of the mean value for the break radius is at $R_{b} = 2.4\pm0.8 h_{in}$. The inner scalelength is consistently larger than the outer: $h_{in}/h_{out} = 4.5\pm1.8$. First results will be given for face-on equivalents serving as the crucial test to assure the findings for the edge-on sample without suspected geometrical line-of-sight effects. We undoubtedly confirm the deduced two-slope or smooth truncation structure in a few cases. In addition, some caveats will be given concerning the available characteristic disk parameters and their model dependence such as scalelength or scaleheight.

Dynamical simulations: waiting for VLT-GIRAFFE observations of distant galaxies

Laurent Chemin and Veronique Cayatte OBSPM, FRANCE Laurent.Chemin@obspm.fr () The VLT-GIRAFFE instrument is a soonly released optical (370 nm $ \leq \lambda_{obs} \leq$ 900 nm) multifibre spectrograph working at medium or high resolution (9000 $\leq R \leq$ 29000). Two of the three observational modes will be integral field : 15 deployable \textbf{I}ntegral \textbf{F}ield \textbf{U}nits (2.1"$\times$3.1") in the 25' field of view and 1 large array \textbf{ARGUS} (11.5" $\times$ 7.3" or 6.6" $\times$ 4.2"). \par With these modes, spectroscopy of disks at redshifts up to $z\sim$ 1 will allow to do kinematical and dynamical studies of galaxies. In particular, the \textbf{IFU} mode is well adapted to map distant galaxies because the size and the number of its arrays are consistent with those expected for objects in a redshift range in such a field of view. \par To understand the future GIRAFFE data, we need an analysis tool based on simulations which results will be directly compared to the observations. The main inputs of the simulations are the luminosity distribution of objects through high angular resolution imaging and the velocities distribution. We will be able to see which kinematical model can account for the observations and so to evaluate fundamental parameters of the objects (for instance the maximum rotational velocity useful for the Tully-Fisher relation, the mass...) or the rate of interacting galaxies. We present here the results of different simulations.

On the stellar mass density within spiral galaxy disks

Thilo Kranz*, Adrianne Slyz**, Hans-Walter Rix* * MPI Astronomie, Heidelberg, Germany ** University of Oxford, UK kranz@mpia.de () We study the mass density within spiral galaxies on the basis of NIR photometry and gas kinematics from observations and simulations. Although K-band images provide a quite reliable estimate of the stellar mass distribution within the disks of spiral galaxies, we demonstrate that correcting the color to a constant stellar M/L leads to shorter disk scale lengths and has a notable effect on the disk-halo decomposition. In most sub-maximal disk decompositions, good fits to a galaxy's measured rotation curve cannot be achieved by axisymmetric disk and halo models but require non-circular velocity components to be taken into account. We accomplish this by performing 2D hydrodynamical gas simulations. Furthermore, in comparison with the galaxy's measured kinematics, the simulated velocity fields allow us to constrain the contribution of a smooth dark matter component to the total mass in the inner few exponential disk scale lengths in spiral galaxies. We show for a sample of galaxies that the simulations overpredict the non-circular gas motions for a strictly maximal stellar disk contribution. Our data sample will be made available for public use.

On the spiral Structure of NGC 2915

M. Bureau and F. Masset Columbia University Saclay fmasset@cea.fr () Eulerian numerical simulation of the HI disk gas of the galaxy NGC2915 are presented, and the results are used to infer the properties of this disk and the surrounding halo (HI surface density, dark matter content, etc.)

Bar Wings

Maria Sundin Mikael Lerner Magnus Thomasson Gothenburg University, Sweden SEST, Chile Onsala Space Observatory, Sweden tfams@fy.chalmers.se () In galaxies with short bars, i.e. bars not extending out to the co-rotation radius, there may be an extra dynamical component located between the bar and a spiral arm pattern starting at the co-rotation radius. We call this component "the bar wings". The appearance of a galaxy with bar wings changes dramatically on timescales shorter than a bar rotation period. The bar wings will periodically appear as leading or trailing arm fragments. In between, it may show up as an outer envelope surrounding the bar or as a theta- galaxy. The bar wings is a bar-like component in the sense that the phase of the m=2 Fourier component of the surface is roughly constant within it. The bar and the bar wings are involved in a continous and alternating exchange of angular momentum between them. The result is that the pattern speeds of both the components show strong oscillations that are 180 degrees out of phase. A simple orbit analysis reveals that the 3:1 resonance orbits are a major constituent of the bar wings. Also 4:1 orbits and orbits around Lagrange points L4 and L5 are important.

Spiral shape and mass distribution in five grand design galaxies

Magnus Thomasson Karl Johan Donner Onsala, Sweden Helsinki Univ. Observatory, Finland magnus@oso.chalmers.se () From N-body simulations of disc galaxies, we have found that the shape of the spiral arms corresponds to Toomre's critical wavenumber (which depends on the rotation curve, through the epicyclic frequency, and on the disc surface density). For real galaxies, the disc surface density can thus be determined from observations of the rotation curve and the shape of the arms. We have applied the method to five grand design spiral galaxies with inclinations large enough that the rotations curve can be determined, but small enough for the spiral structure to be clearly visible: M51, M100, NGC1357, NGC1566, and NGC2997. Using published rotation curves and images, we first determine the disk surface density. From published disk/bulge decompositions of the observed luminosity distribution, we then calculate the mass-to-luminosity ratio for the disc. The M/L-ratios we obtain in this way are relatively low. This method of determining the disc surface denstity is independent of additional assumptions, and the results show that there cannot be large amounts of dark matter in the discs of the five studied galaxies.

Multi-Wavelength Study of NGC 1784

Douglas L. Ratay Stephen T. Gottesman University of Florida, USA doug@astro.ufl.edu () NGC 1784 is a flocculent, barred, late type spiral galaxy. We present HI, optical(narrow and broad band), and NIR images of this galaxy. NGC 1784 seems to be undergoing an interaction with a small companion galaxy. This was undiscovered before our HI observations were made. A link from this galaxy to a large sample studying the properties of barred and flocculent galaxies will also be made.

Dynamical Evolution of Central Kpc in Barred Galaxies

Isaac Shlosman JILA, University of Colorado at Boulder, USA shlosman@jila.colorado.edu () Recent progress in ground-based instruments and the availability of the Hubble Space Telescope allows for the first time a meaningful analysis of central morphology and kinematics, both stellar and gaseous, in disk galaxies. I will discuss implications for dynamics and evolution of this region and for its coupling with smaller and larger spatial scales.

3D modeling of the vertical structure of the galaxy

Gilberto C. Gomez Donald P. Cox UW - Madison, USA gomez@wisp.physics.wisc.edu () We present the results of our 3-dimensional modeling of a MHD flow into a spiral gravitational potential, extending the work done by Martos \& Cox (1998). We pay particular attention to the similarities of the resulting structures to hydraulic bores, generation of substructure, and secondary gaseous arms.

wwall@inaoep.mx ()

Eccentric Equilibria for Keplerian Fluid Disks

T. S. Statler Ohio University, Athens, OH, USA tss@coma.phy.ohiou.edu () In the idealization of a razor-thin Keplerian disk, flow along aligned, elliptical streamlines of constant eccentricity creates a density that is constant on streamlines. In such a configuration there will be no compression of the fluid, and therefore no dissipation due to bulk viscosity. For most density profiles, the pressure gradient will drive a differential precession which will destroy the alignment; however, there is a family of simple equilibria in which the precession frequency is the same at all radii. These disks could therefore be long-lived at significant eccentricities if the shear viscosity is negligible. In the limit of small eccentricity, the models can be seen as axisymmetric disks perturbed by a traveling acoustic wave similar to an ocean wave, in which the fluid rises and falls epicyclically in the gravitational field of the central mass. The expected emission line profiles from the eccentric disks are strongly asymmetric in general, and, in extreme cases, prone to misinterpretation as single narrow lines with significant velocity offsets.

A new look at the holes of dwarf galaxies (POSTER)

F. Javier Sanchez-Salcedo IA-UNAM jsanchez@astroscu.unam.mx () New stastitiscal tests are proposed to discriminate between the different scenarios proposed for the formation of HI holes in gas-rich dwarf galxies. Although conclusions are still premature, the standard scenario of expanding shells by powerful energy injection by winds and supernova explosions is favoured.

Disk Galaxy Evolution

Roberto Abraham Dept. of Astronomy & Astrophysics, University of Toronto, Canada abraham@astro.utoronto.ca () Recent progress in constraining the evolution of disk galaxies will be reviewed. I will focus in turn on evidence for evolution in the size, luminosity, morphological and dynamical characteristics of luminous disks. At least *some* of these characteristics are well constrained to z=1. Some characteristics (such as detailed morphology) change quickly with redshift, but there is little evidence that other characteristics (such as size) change at all. I will touch upon the implications of these observations for theories of galaxy formation, and conclude that the redshift range 1$<$z$<$2 is critical for testing such theories. This is also the redshift range over which we know the least about luminous disk galaxies. The severe observational selection effects inherent in studying disk evolution at z$>$1 will then be described, and a summary given of what little is known about disk galaxies at 1$<$z$<$2 in spite these selection effects. I will conclude by showing how the Advanced Camera for Surveys coupled with technical advances in ground-based spectroscopy (such as the nod and shuffle technique) will open up the 1$<$z$<$2 redshift range for study in the next couple of years.

dhuos@inaoep.mx ()

Simulations of the Eccentric Nuclear Disk in M31

Robert M. Salow Ohio University salow@helios.phy.ohiou.edu () We have constructed approximate self-consistent models of eccentric stellar disks around central black holes. These models include a finite-dispersion, weakly self-gravitating disk in a frame rotating at a constant precession speed. The disks are built by an iteration scheme in which the disk is populated by quasi-periodic orbits using a distribution function written in terms of the Kepler integrals of motion. Properties of these models will be discussed, particularly those that are relevant to the double nucleus of M31. We have also developed an n-body code which is well suited for stability studies of disk systems with high-eccentricity orbits. Preliminary results on the use of this code to study the stability of our disk models will be discussed.

omartin@fcfm.buap.mx ()

Magnetohydrodynamic Density Waves in Spiral Galaxies

Yu-Qing Lou Department of Astronomy and Astrophysics, University of Chicago, USA lou@oddjob.uchicago.edu () Relativistic cosmic-ray electrons interact with galactic magnetic fields and give rise to synchrotron radio emissions that reveal well-organized large-scale spiral patterns in good correspondence to large-scale optical structures of spiral galaxies. The system of a spiral galaxy involves a massive dark-matter halo, a thin stellar disk, a magnetized gas disk of interstellar medium (ISM) and a spheroid of cosmic-ray gas. We here describe a physical scenario for magnetized spiral galaxies on the basis of magnetohydrodynamic (MHD) density waves which involve self-gravity, differential rotation, epicyclic oscillations, Lorentz force, pressure force and velocity dispersions. The basic results of our analyses on fast and slow MHD density waves since 1996 (Fan & Lou, Nature, 383, 800) are summarized. For multiwavelength observations of spiral galaxies, we emphasize the perspective that large-scale magnetic fields of MHD density waves play the key role in organizing correlated structures of the various underlying ISM components. In particular, the magnetized neutral hydrogen disk is an integral component in the overall MHD density wave scenario (Lou et al. ApJ, 2002). Possible wave excitation mechanisms are mentioned and diagnostic features of magnetized ISM are emphasized. Applications to nearby spiral galaxies NGC6946, M51 (NGC 5194), M31 (NGC 224) and NGC2997 will be discussed. Based on recent magnetic field observations of NGC1097 and NGC2997, it becomes evident that MHD density waves also play important roles in the circumnuclear regions and may be responsible for the appearance of luminous starburst rings (Lou et al. 2001, ApJL, 553, 35). It would be extremely important to map out in details magnetic field patterns in the circumnuclear regions of spiral galaxies. With proper adaptations, the physics of spiral MHD density waves may be relevant to the dynamics of accretion disks in various astrophysical contexts, especially in terms of transporting angular momentum.

Asymmetries in the disk of the Milky Way

Drimmel, R. and Smart, R. Osservatorio Astronomico di Torino, Italy drimmel@to.astro.it () Asymmetries in the stellar disk of the Milky Way, manifested by the Galactic warp and spiral arms, are investigated using Galactic diffuse NIR emission and optical star counts from the recently released Guide Star Catalogue II. Star counts for approximately 150 lines-of-sight within 25 degrees of the Galactic poles, covering nearly 4000 square degrees of sky, are analyzed using a model independent method to assess the amplitude of a local tilt in the stellar disk. Such a tilt is consistent with a Galactic warp starting within the Solar Circle, and as seen in the diffuse NIR emission as measured by COBE (Drimmel & Spergel 2001, Freudenreich 1998). Finally, various spiral arm geometries, including one based on the dynamical model of Amaral and Lepine (1997), are incorporated in a model of the Galactic diffuse NIR emission that is then fit to observations made by the COBE satellite. The favored models have a four arm pattern, with two arms dominating.

WIYN Integral-Field Kinematics of Disk Galaxies

Matthew A. Bershady U. of Wisconsin, USA mab@astro.wisc.edu () We present results on medium spectral resolution, 2D kinematic studies of disks with DensePak and the newly-commissioned SparsePak fiber array on the WIYN telescope: A Tully-Fisher relation for nearly face-on galaxies; H-alpha velocity fields of low-surface-brightness disks; and the stellar velocity fields and dispersions of normal disks. These data permit us to explore the detailed mass distributions, mass-to-light ratios, and asymmetries of a wide range of spiral galaxies. We discuss the implications of these studies in the context of comparable measurements at higher redshift.

pochoas@inaoep.mx ()

ahtramop@inaoep.mx ()

yamil@inaoep.mx ()

1. Neutral Hydrogen Observations in Isolated Triple Systems of Galaxies. 2. BVRIJHK Surface Photometry and Halpha Fabry-Perot Interferometry in Mixed Morphology (E+S) Pairs of Galaxies.

1.H.M.Hernandez-Toledo, W.K. Huchtmeier, V.Karachentseva and E. Brinks. 2. H.M. Hernandez-Toledo, M. Rosado, I.Cruz-Gonzalez, and A. Franco 1. Instituto de Astronomia, UNAM, Mexico. Max-Planck-Institute fur Radioastronomie, Bonn, Germany. Astronomical Observatory of Kiev. Departameno de Astronomia, Universidad de Guanajuato, Mexico. 2. Instituto de Astronomia, UNAM, Mexico hector@astroscu.unam.mx () 1. We report single-dish HI (Effelsberg 100m Telescope) observations of a sample of 26 Isolated Triple Systems of Galaxies in the Northern Hemisphere , Karachentseva (1979;1988). 2. We report some preliminary results of an Optical/NIR photometric and Interferometric study in a sample of Mixed Morphology (E+S) Pairs of Galaxies from the Catalogue of Isolated Pairs of Galaxies, Karachentsev (1972).

Kinematic response of the outer stellar disk to a central bar

Gerhard M\"uhlbauer, Walter Dehnen Gerhard M\"uhlbauer: MPIA Heidelberg, Germany Walter Dehnen: MPIA Heidelberg, Germany muehlbau@mpia-hd.mpg.de () We performed numerical 2D simulations in order to estimate the influence of a central bar-like perturbation on the velocity distribution in the outer parts of a disk galaxy. To get reasonable statistics, priority was not on a self-consistent calculation but rather on a high particle number of $10^7$. Therefore a fixed potential for the galaxy together with a rotating perturbation with m=2-symmetry was assumed. After completion of adiabatic growth of the perturbation and some further rotation periods for the disk to re-settle into equilibrium, the first and second moments of the resulting velocity distribution have been analysed, giving information on assymetric drift, vertex deviation and Oort constants. Results are presented best as azimuthal Fourier components with focus on the m=2-components corresponding to the perturbation symmetry. Several resonance patterns are discernible.

Secular evolution of barred galaxies : theory

E. Athanassoula Observatoire de Marseille lia@paxi.cnrs-mrs.fr ()

Dark matter in spiral galaxies

A. Bosma Observatoire de Marseille bosma@batis.cnrs-mrs.fr () I will explain why we still do not have a "standard" model for the mass distribution of spiral galaxies, and describe various methods which might help to get us there. I will also describe ongoing work on declining rotation curves and other topics based on HI observations.

toa@inaoep.mx ()

pepe@astroscu.unam.mx ()

Formation of Galaxy Discs by merger of sub-galaxies

Williams, P.R. & Nelson, A.H. Tohoku University (Japan) and Cardiff University (UK) nelsona@cf.ac.uk () Computer Simulations of galaxy formation show that an important mechanism for the formation of galaxy discs is the tidal disruption of smaller satellite galaxies which are an integral part of the formation process. A star-forming Tree SPH simulation of this process will be analysed.

Warped galaxies and the dark matter connection

Yves Revaz Geneva Observatory, SWITZERLAND yves.revaz@obs.unige.ch () 50 years have passed since the first HI observation of the Milky Way warp. If during this time, numerous hypothesis have been proposed to explain this galactic common phenomenon, none of them was able to clearly satisfying all the constraints provided by the observations. Most of the works on the topic are based on the assumption of a spherical or triaxial dark matter halo as predicted by the CDM theory. In this poster, we point out some problems arising with a dynamically hot dark matter halo and explore the hypothesis of a heavy self-gravitating warped disk. For such a model, periodic orbits which form the backbone of the galaxy are described and are confronted with N-body simulations.

Interaction of HVCs with Galactic Disk.

Alfredo Santillan(1) & Jose Franco(2) (1) CA-DGSCA, UNAM, Mexico. (2) IA, UNAM, Mexico alfredo@astroscu.unam.mx ()

The role of the magnetic field in the lopsided structures in the Galactic Center region

Michel Tagger Service d'Astrophysique, CEA Saclay (France) tagger@cea.fr () I will describe how recent results on a spiral instability of magnetized accretion disks could shed light on the structures observed in the Galactic Center region. There, on a scale of $\sim 100$ pc, the distribution and velocity field of the gas is strongly lopsided, while the magnetic field is highly anomalous: it is vertical (rather than mostly horizontal in the Glactic disk), and measured in milligauss (rather than microgauss). The magnetized structures observed above the disk provide a natural diagnostic of the complex dynamics in this region.

Off-plane gas and galaxy discs

Linda Sparke Astronomy Deaprtment, University of Wisconsin-Madison sparke@astro.wisc.edu () Gas that orbits a disk galaxy, but does not lie in the plane of the disk, has probably been perturbed or excited out of that plane, or has fallen in from outside. Recent work shows no easy path to exciting galactic warps of the amplitude that we observe; in polar ring galaxies, the outer, mainly gaseous, ring appears to be 'younger' than the inner stellar body. This talk reviews the idea that both warps and polar rings represent the relics of earlier infall or interaction.

yjuarez@inaoep.mx ()

Disk Formation in CDM: Crises and Resolutions

Avishai Dekel Hebrew University of Jerusalem dekel@phys.huji.ac.il () The spin problem and the cusp problem of galaxy formation in CDM cosmology are addressed in terms of tidal effects during halo buidup by mergers. It is argued that feedback processes provide possible resolution to these problems.

The coupling between the baryonic and dark matter components in galaxies

Amr El-Zant, Isaac Shlosman University of Kentucky and CASA, University of Colorado at Boulder, USA elzant@origins.colorado.edu () We examine the effect of dark matter distribution on the evolution of baryonic component in galaxies and vice versa. In particular we study the effect of halo central concentration and (a)symmetry on disk formation and oribital stability.

Circumnuclear structures in the interacting active galaxy NGC 1241: kinematics and optical/IR morphology

Diaz R.J. (1), Dottori H. (2), Villamizar N. (2), Carranza G. (1) (1) Observatorio Astronomico de Cordoba, UNC, Argentina (2) Instituto de Fisica, UFRGS, Brasil diaz@oac.uncor.edu () We have studied the central regions of NGC 1241, an interacting galaxy with an active nucleus. We used high resolution Gemini North Telescope K, J images (~ 0.3" resolution), HST Pa alpha and (V+R) images (~ 0.2" and ~ 0.1") to analyze the spiral pattern in the inner 7" (1" = 257 pc). The complete set of data allowed us to unveil the presence of peculiar features in the nuclear region of this galaxy: a trailing spiral structure inside a star formation ring with dimensions 2.8" x 1.7", a mini-bar (1.4") and what appears to be a pair of leading nuclear spiral arms. The circumnuclear ring appears clumpy in Pa alpha emission, it has a mean diameter ~ 1400 pc and harbours a N-S aligned ~ 500 pc long, central bar. The morphological scenario is complex and the structural parameters are different in each band. Gemini-Hokupa'a images show a smooth, inclined disk, with approximately elliptical isodensities of varying position angle. Ellipses fits indicate that the disk inclination is similar to that of the star forming ring. The overall reddening to the southwest of the nucleus is stronger, implying that this is the near side of the galaxy. The Pa alpha nuclear bar, almost perpendicular to the global one, was not detected in a previously published HST color map. We have applied 2D and 1D Fourier analysis for the first time at circumnuclear scales in the optical and IR bands simultaneously. Fast Fourier Transform shows that a barred m=2 mode is dominant in K and J bands. The bar in K and J bands is counterclockwise rotated by 30� with regard to the Pa alpha one. (V+R) band presents a more complex structure with a strong m=1 mode. The position of the m=2 mode corotation is clearly defined by our analysis and approximately coincides with the extreme of the Pa alpha bar. The leading spiral pattern ends in the Pa alpha ring. Our kinematical data yield a trailing pattern angular speed Omega_p = 230+-20 km/sec/kpc. Published numerically modelled galactic disks indicate a pattern age of the order of tens of millions years. Nevertheless, considering its high angular speed, the pattern has done several revolutions since the perturbation origin. The study of the rotation curve, with a lower angular resolution, indicates that the circumnuclear ring would be just inside the Inner Lindblad Resonance (r ~ 1 kpc) of the global pattern.

Magnetic Fields in Southern Barred Spiral Galaxies

J.I. Harnett, R. Beck, M. Thierbach, M. Ehle, R.F. Haynes & R. Wielebinski UTS Max-Planck_Institut fuer Radioastronomie Max-Planck_Institut fuer Radioastronomie University of Tasmania Max-Planck_Institut fuer Radioastronomie jules@eng.uts.edu.au () Polarized radio emission from southern barred spiral galaxies. Magnetic fields in normal spiral galaxies follow, in the main, optical spiral arm patterns, but are often of maximum intensity between the arms. In barred galaxies however, the conditions are somewhat different; the gas and dust move in highly non-circular orbits and streamlines are strongly deflected in the bar region along shock fronts, behind which the gas is compressed in a fast-shearing flow. The gas in the bar region rotates faster than the bar so compression regions traced by massive dust lanes develop along the edge of the bar that is leading with respect to the galaxy's rotation. Gas inflow along the compression region may fuel starburst activity in a dense circum-nuclear ring although this inflow is difficult to measure observationally and the dynamics are not understood. In order to investigate the role of the magnetic field in the bar with respect to the gas flow and star formation, we have observed 19 nearby barred galaxies. We present our results for some southern galaxies here.

Gas Kinematics in Barred and Spiral Galaxies

Michael Regan Space Telescope Science Institute mregan@stsci.edu () The kinematics of the interstellar medium in disk galaxies influences many processes in galaxy evolution. For example, since the gas in dissipative it can lose angular momentum and thus increase the central mass concentration in the galaxy. In addition, the interstellar medium is the fuel for star formation and star formation can be influenced by a variety of kinematic processes such as spiral density waves, shocks in bars, and bar driven mass inflow. In this talk I will review the state of the art in various type of kinematic observations of the atomic, molecular and ionized interstellar medium. I will concentrate on observations that produce full two-dimensional maps of the kinematics since these provide us with the most information to compare to other observations and models.

Global Interstear Gas Masses and Gas Surface Densities in Spiral Galaxies

Judith S. Young U.Mass., Amherst, USA young@astro.umass.edu () The observations made as a part of the FCRAO Extragalactic CO Survey (Young et al. 1995) are used to examine the molecular gas distributions, the global H$_2$ masses, the star formation efficiency, the H$_2$/HI ratio, and the gas to dust ratio, within and among 300 galaxies in the local universe as a function of morphology, luminosity, and environment. Significant global trends in the gas-to-dynamical mass ratio, the molecular gas-to-warm dust mass ratio, and the H$_2$/HI ratio are found as a function of morphology for spiral galaxies along the Hubble sequence. Globally in these systems, the luminosity of high mass stars per unit mass of molecular gas (also called the star formation efficiency) does not vary in the mean as a function of morphology, while the star formation efficiency does show significant variations as a function of environment. The star formation efficiency also shows a marked tendency to be elevated in smaller spiral galaxies. All of these results are presented, and used to provide insight into the processes of star formation and galaxy evolution, as well as placing constraints on current models of galaxy evolution.

The effect of minor mergers on spiral galaxies

Rodrigo Ibata Observatoire de Strasbourg ibata@astro.u-strasbg.fr () We know that spiral galaxies are continually accreting mass even at the present day, as we observe many of them, including the Milky Way, in the process of swallowing up itheir smaller companions. I will review the recent observations and the recent numerical experiments, which suggest that repeated accetions have a significant impact on the dynamical and chemical evolution of the primary galaxy.

DYNAMICAL AND CHEMICAL EVOLUTION OF THE LMC DISK

HORACIO A. DOTTORI INSTITUTO DE F�SICA, UNIVERSIDADE FEDERAL DO RIO GRANDE DO SUL, PORTO ALEGRE, BRAZIL dottori@if.ufrgs.br, dottori@voyager.com.br () The LMC present us with a unique case to study the connection between the process of star formation and the structure and dynamics of disks. Its study is important to bridge the gap between the study of small scale structures in the Milky Way and that of global processes in distant galaxies. In this talk we revise kinematical observations at different wavelenghts as well as the kinematical implications of stars and mainly of star-clusters ages and distribution. We also discuss the possible effect of the interaction with the Milky Way and with the Small Magellanic Cloud and the imprints left by these interactions in the process of star formation as well as in the present disk structure.

Evolution of galaxy bulges

Balcells, M. Instituto de Astrofisica de Canarias, Spain balcells@ll.iac.es () I present recent results of our ongoing study of galaxy bulges. We have determined the Fundamental Plane (FP) of bulges in B and K. The FP closely follows that of ellipticals and S0 in Coma, adding to the evidence that early-to-intermediate bulges are old. I then emphasize the suitability of S\'ersic's law to model the surface brightness profiles of bulges, and use N body simulations to show that bulges may evolve by accretion of dense satellites. Such accretion explains the growth of thick disks in early-type galaxies. Last, I discuss recent HST/NICMOS imaging of bulge cores and compare bulge profiles and central densities to those of ellipticals at HST resolutions.

Formation of Galactic Disks

S. Michael Fall STScI fall@stsci.edu () This contribution will review the theory of the formation of galactic disks. The emphasis will be on understanding the origin and evolution of the angular momentum of galaxies, which determines the most basic properties of the disks. Some of the problems the theory has encountered will be reviewed, as well as some of the most likely solutions.

Pulsars Spin-Down History

Cesar Alvarez Ochoa Alberto Carrami\~nana Alonso INAOE, Mexico calvarez@inaoep.mx () Most pulsars are concentrated around (P~log -0.3,Pdot~log -14.7) in the $\dot{P}-P$ diagram. It is believed that pulsars arrive to that region of the diagram through spin-down evolution from region of short periods and large period derivatives. However, there is no clear correlation between $\dot{P}$ and $P$ in the $\dot{P}-P$ diagram. The details of the spin-down mechanisms remain unclear, despite the many models proposed to describe them. In this work, we present a multipole spin-down equation directly derived from the general model, $\dot{\nu}=-f(\nu,t)$. We test this model against the $\dot{P}-P$ diagram using four young pulsars with good timing history: the Crab, Vela, PSR B1509-58 and PSR B0540-69. We found that if pulsars do not change their parameters with time, the evolutionary model is inconsistent with observations. By assuming that magnetic fields decay significantly during the pulsar life time, we found that a decay law of the form $B(t)=1/(1+t/t_c)$ with timescales of around $10^4$ years fits the observations.

Kinematics and massive star formation in the disk of the MW.

Abraham Luna Luis Carrasco Leonardo Bronfman William Wall INAOE, Mexico INAOE, Mexico U. de Chile INAOE, Mexico aluna@inaoep.mx () We test the Schmidt`s Law in the disk of the Milky Way, using the most complete data sets of CO and massive star formation regions. We confirm that star formation is enhanced in regions with high gas density. Preliminary results show the connection between high gas density, rigid-body kinematics with small shear, and arms regions.

aleonl@inaoep.mx ()

kraan@astro.ugto.mx ()

alfred@astroscu.unam.mx ()

gergim@oac.uncor.edu ()

nelson@inaoep.mx ()

The dynamics of S0 galaxies

A correlation between supermassive black hole mass and galaxy light concentration in bulges

The distribution of disks in the $\mu_0$--$\log h$ plane and the inclination correction

Structure, Kinematics, and Dynamics of Bulges

The local star formation history of the Galaxy

The interaction of galactic disks with satellite galaxies

Spatial distribution of ionized gas and stars in ring galaxies

Intermediate-band Surface Photometry of the Edge-on Galaxy: NGC 4565

SED, Metallicity and Age of Halo Globular Clusters in M33

Optical Structure of Disks

Simulations of stellar and gaseous morphologies in spiral galaxies

NGC 1023 (Arp 135): A Prototype for the Study of S0 Galaxies?

Proto galaxies and Galaxy Morphology

Constraining the SPH Kernel Radius in Galaxy Simulations

Secular Evolution in Barred Galaxies: Observations

Tracing the disk and the halo of the Milky Way with kinematics of sdB stars

Formation and evolution of galactic disks

Dynamical influences on star formation in spiral galaxies

Conference Summary

Gas morphology and dynamics in the central kpc: embedded bars and nuclear spirals

Morphology of 3D bars

Star Formation along the Hubble Sequence: Results from a new Halpha Galaxy Survey

Kinematics of Galaxy Disks

Dynamics of Stellar Orbits in Disk Galaxies

High spectral resolution kinematics of galaxies: the figure of eight effect close to the galaxy's center.

The Gasesous Properties of Seyfert Host Galaxies

Galactic Warps and Bars in Axisymmetric Halos

Dynamical Modeling of Stellar Nucleus of M31

Density waves in the central kpc of galaxies: the role of nuclear spirals, bars and m=1 modes.

The properties of the dense interstellar medium in the central regions of starburst and normal galaxies

Molecular gas in the barred spiral galaxy M83

Characteristics of the Galaxy's Thick Disk

Three dimensional HI gas distribuiton in Milkyway Galaxy

Instabilities and Modes of Collisionless Disks

Magnetic fields in spiral arms and bars

Bar dynamical friction and disk galaxy dark matter content

High Resolution Radio Continumm Observatins of the Barred Spiral Galaxy NGC 3367

Dynamical evolution of M92 Globular Cluster - Proving the Milk-Way disk-shocking

Spiral Structure observed in Near-Infrared

Nested Bars, Inner Disks, and Nuclear Rings in Barred Galaxies

Fitting a Galactic Model to an All-Sky Survey

A Large Asymmetry in the Distribution of Faint Stars in the Inner Galaxy

The Connection Between Star Formation and Resonant Dynamics in Early-Type Disk Galaxies

The de Vaucouleurs Atlas of Galaxies

The Molecular Gas Distribution in Polar Ring Galaxies

N-body simulations of resonance rings

Old stellar Galactic disc in near-plane regions according to 2MASS: scalelengths, cut-off, flare and warp

none

Mass Concentration and Bar Dissolution in Spiral Galaxies

Midplane Stellar Orbits and Mass distribution in the Presence of 3D Spiral Arms

Simulations of the Magellanic System: Internal Structure of the Clouds

Comparing Molecular Gas and Star Formation Properties in the Central Regions of Barred and Unbarred Spirals

Simulations of the Magellanic System: Internal Structure of the Clouds

Numerical Simulations of Disk Galaxy Formation

Pattern Speed of Bars

The Intrinsic Ellipticity of Spiral Disks

Velocity Fields of Disk Galaxies

Global properties of disks from the Flat Galaxy Catalog

Unveiling the behavior of the ionized gas in nearby irregular galaxies

The gravitational torque of bars

The Spatial Distribution of the Star Formation in (S+S) Binary Galaxies

The Milky Way

Bloated Dwarfs: The Thickness of the HI Disks in Irregular Galaxies

The 3D structure of the Galactic bulge from the MACHO red clump stars

Arm vs. interarm star formation processes in disk galaxies

Radial structures of galactic disks

Dynamical simulations: waiting for VLT-GIRAFFE observations of distant galaxies

On the stellar mass density within spiral galaxy disks

On the spiral Structure of NGC 2915

Bar Wings

Spiral shape and mass distribution in five grand design galaxies

Multi-Wavelength Study of NGC 1784

Dynamical Evolution of Central Kpc in Barred Galaxies

3D modeling of the vertical structure of the galaxy

Eccentric Equilibria for Keplerian Fluid Disks

A new look at the holes of dwarf galaxies (POSTER)

Disk Galaxy Evolution

Simulations of the Eccentric Nuclear Disk in M31

Magnetohydrodynamic Density Waves in Spiral Galaxies

Asymmetries in the disk of the Milky Way