bluuebunny/crossref_metadata_2025 huggingface dataset:
The Many Vortexes of NGC 5236 Nucleus in The Central 80×200 Parsecs
Authors: Diaz R. , Rodrigues I. , Dottori H. , Mast D. , Agüero M. P.
Published: April 2007

GEMINI-S+CIRPASS configuration has been used to obtain 490 high quality spectra, centred in 1.3 microns of the NW-SE oriented, central 80 × 200 pc of NGC 5236 (M83), with spectral resolution of 3200. We determine the kinematics of this region with 0.36 arcsec sampling, sub-arcsec resolution. Disk-like motions are detected in Paβ at parsec scales around: a) the optical nucleus (ON), b) the dynamical centre of the CO velocity map (Sakamoto et al 2004) coincident with the K–band center (hereafter KC; Thatte et al. 2000), located 50 pc to the W of the optical nucleus, and c) the hidden condensation (hereafter HN; Mast et al. 2006), now more precisely located at 120 pc to the N-NW of the optical nucleus. The disk around ON has a radius of 10–15 pc and those around KC and HN can be traced approximately up to 40-50 pc from their kinematical centres. Rotation curve fittings using Satoh like spheroids give masses of 2–4×106M⊙, 10–15×106M⊙ and 15–20×106M⊙ respectively. N-body simulations using Gadget2 (Springel, 2005) show that ON, KC and HN will merge in 20-50 Myrs. A question that arise immediately is if this degree of dynamical activity is peculiar of M83 or it is a common behaviour, seen in this galaxy in all its dramaticity due to its small distance from us.
Seyferts in 3D: Probing the Kinematic Signatures of Gas Fueling
Authors: Dumas Gaelle , Emsellem Eric , Mundell Carole G.
Published: April 2007

We have conducted a 3D imaging spectroscopic survey of 15 nearby Seyfert and control non-active galaxies, using the SAURON Integral Field Unit on the WHT. One goal of the project is to search for dynamical triggers of nuclear activity in nearby galaxies. We present here the preliminary results of the kinematic analysis of the gaseous and stellar velocity fields.
The Jet-Cloud Interaction in 3CR Galaxies: Preliminary Results in Four Galaxies
Authors: Feinstein C. , Macchetto F. D. , Montero M. F. , Hägele G. F.
Published: April 2007

We present preliminary results of the Gemini/GMOS longslit spectra for four radiogalaxies: 3C 135, 3C 180, 3C 234 and 3C 284. These objects are a subsample of a set of galaxies with noticeable extended structure selected from the HST/WFPC2 3CR Snapshot Survey, data taken with the filters F555W, F702W and narrow-ramp. All of these objects show large regions of [Oiii]λ5007 emission (narrow ramp filter) and the broad-band filters data show similar structures indicating the presence of strong emission in several lines over these regions. The morphology observed seems to be related (e.g. same position angle, direct overlapping or similar shape) with the radio-jet. For some candidates with these properties GMOS/Gemini spectroscopy was taken. These data (both HST direct imaging and Gemini spectroscopy) can be tested with diagnostic diagrams and total UV photons budget to understand the source of energy that is ionizing the gas. This source of ionization was commonly believed to be the UV photons emitted by the powerful AGN, but several of these objects shows clearly that shocks produce by the radio jet are the main cause of the observed gas line emission.
GEMS: The destiny of Blue Spheroidal Galaxies
Authors: Häußler Boris , Bell Eric F. , Barden Marco , McIntosh Daniel H. , Rix Hans-Walter , Borch Andrea , Beckwith Steven V. W. , Caldwell John A. R. , Heymans Catherine , Jahnke Knud , Jogee Shardha , Koposov Sergey E. , Meisenheimer Klaus , Peng Chien Y. , Sánchez Sebastian F. , Somerville Rachel S. , Wisotzki Lutz , Wolf Christian
Published: April 2007

One of the key predictions of hierarchical galaxy formation models is that a significant fraction of elliptical galaxies form in late merging events. One of the most important diagnostics of such an assembly is the existence of blue spheroidal galaxies, which have spheroid-dominated morphologies and blue colors indicating recent star formation, as an intermediate step in the evolution of elliptical galaxies.
A Case-Study of Grand-Design Warps in Galactic Disks
Authors: Józsa Gyula I. G. , Kenn F. , Klein U. , Oosterloo T. A.
Published: April 2007

We present the results of a case-study of three typical galaxies with integral-shaped warps. We apply a new method to directly fit tilted-ring models to high-quality Hi data cubes obtained with the WSRT and report on the features found to be present in the models.
Dynamical Evolution of the Mass Function of the Globular Cluster System from Fokker-Planck Calculations: Preliminary Results
Authors: Shin Jihye , Kim Sungsoo S.
Published: April 2007

Using anisotropic Fokker-Planck models, we calculate the evolution of mass and luminosity functions of the Galactic globular cluster system. Our models include two-body relaxation, binary heating, tidal shocks, dynamical friction, and stellar evolution. We perform Fokker-Planck simulations for a large number of virtual globular clusters and synthesize these results to study the relation between the initial and present GCMFs.
Narrow-Line Regions in Seyfert Galaxies and Quasars: Modelling 2D Kinematics
Authors: Jungwiert Bruno , Stoklasová Ivana , Bennert Nicola
Published: April 2007

We attempt to provide new insights into the kinematics of narrow-line regions (NLR) in Seyfert galaxies and quasars, the understanding of which, as well as of their intrinsic 3D morphology, is still rather limited. Motivated by the rise of the integral-field spectroscopy, capable of mapping full 2D velocity fields, and by our observational projects on NLRs (see e.g. Stoklasová et al., this volume) we have developed a computer code producing 2D kinematical maps resulting from projections of various gas geometries and velocity fields.
Asymmetric Warps in Disk Galaxies: Dependence on Dark Matter Halo
Authors: Saha K. , Jog C. J.
Published: April 2007

Recent observations have shown that most of the warps in the disk galaxies are asymmetric. However there exists no generic mechanism to generate these asymmetries in warps. We have shown that a rich variety of possible asymmetries in the z-distribution of the spiral galaxies can naturally arise due to a dynamical wave interference between the first two bending modes i.e. bowl-shaped mode(m=0) and S-shaped warping mode(m = 1) in the galactic disk embedded in a dark matter halo. We show that the asymmetric warps are more pronounced when the dark matter content within the optical disk is lower as in early-type galaxies.
Simulating Disk Galaxies: First Results of a Systematical Study
Authors: Köckert Franziska , Steinmetz Matthias
Published: April 2007

Simulating disk galaxies within the current paradigm of galaxy formation has been a long standing problem. In comparison with observations, the simulated disks were too small and too centrally concentrated, due to a large loss of angular momentum during formation. This is known as the angular momentum catastrophe (Navarro & Benz (1991)). Recently, some progress has been made in reducing this effect by changing the cosmology, including various feedback mechanisms, improving numerical resolution and carefully selecting initial conditions with a quiet merging history after z≈2. Unfortunately, it remains unclear which of these effects, or which combination, has resulted in more realistic disk formation. In order to address this problem, we conduct a systematical study using the N-body code GADGET2 (Springel (2005)). We adopt a flat ΛCDM cosmology with Ωm=0.3, ΩΛ=0.7, Ωbar=0.04 and h=0.65. Using a softening of 0.5 kpc we find disks with a very compact unresolved gas clump in the center and a thin, extended disk (R≈10kpc) of very low mass around it.
Evolution Of Compact Radio-Loud AGNs
Authors: Kunert-Bajraszewska M. , Marecki A. , Thomasson P.
Published: April 2007

Multifrequency MERLIN, VLBA and VLA radio observations of Compact Steep Spectrum (CSS) radio sources are discussed. According to the theory of the evolution of CSS sources, they are the precursors of larger/older radio-loud AGNs. However, our observations reveal a small number of strong candidates for compact faders, which support an alternative idea that some small-scale, radio sources are short-lived phenomena.
Disks in Early-Type Dwarf Galaxies
Authors: Lisker T. , Grebel E. K. , Binggeli B.
Published: April 2007

We identify disk features (spiral arms, bars, or edge-on disks) in a significant fraction of Virgo cluster early-type dwarfs. These galaxies are disk-shaped and are an unrelaxed cluster population that possibly formed out of infalling progenitors. Some display spiral arms with grand design features that cannot be the mere remainders of potential late-type spiral progenitors.
Stellar Populations in the Local Group: Contribution from Planetary Nebulae
Authors: Maciel W. J. , Costa R. D. D. , Idiart T. E. P. , Escudero A. V.
Published: April 2007

Planetary nebulae (PN) are favourite objects in the study of stellar populations both in the Galaxy and in other objects as well, due to their high brightness and the considerable range in their kinematic properties and chemical composition. In this work, we take into account available data samples of PN in Local Group galaxies and compare the derived information from different objects, particularly regarding their chemical composition, space distribution, kinematics, and the PN luminosity function.
Peculiar Velocities of Nearby Galaxies
Authors: Makarov D. , Karachentsev I. , Tully B. , Makarova L. , Dolphin A. , Sakai S. , Shaya E. , Rizzi L. , Sharina M. , Karachentseva V.
Published: April 2007

Over the last five years, enormous progress in accurate distance measurements for nearby galaxies has been attained. The Hubble Space Telescope allows us to estimate distances of about 7–10% accuracy using red giant branch (RGB) up to 8 Mpc. Now we have very accurate distances for more than 200 galaxies within ~6 Mpc.
Stellar Populations of Kinematically Decoupled Cores in E/S0 Galaxies
Authors: McDermid Richard M. , Emsellem Eric , Shapiro Kristen L. , Bacon Roland , Bureau Martin , Cappellari Michele , Davies Roger L. , de Zeeuw Tim , Falcón-Barroso Jesús , Krajnović Davor , Kuntschner Harald , Peletier Reynier F. , Sarzi Marc
Published: April 2007

In this poster contribution, we present results from high spatial resolution integral-field spectroscopy of elliptical (E) and lenticular (S0) galaxies from the SAURON representative survey, obtained with the OASIS and GMOS spectrographs. These seeing-limited observations explore the central ∼10''10″ (typically one kiloparsec diameter) regions of these galaxies using a spatial sampling four times higher than SAURON (0″27 vs. 0″94 spatial elements), resulting in almost a factor of two improvement in the median PSF. These data allow accurate study of the central regions to complement the large-scale view provided by SAURON. We derive the stellar and gas kinematics, stellar absorption-line strengths and nebular emission-line strengths for our sample, and derive maps of the luminosity-weighted stellar age, metallicity and abundance ratio via stellar population models. From these data we find a wealth of structures either not seen or poorly resolved in the SAURON data, including a number of kinematically-decoupled cores (KDCs) in the centres of some galaxies. We compare the intrinsic size and luminosity-weighted stellar age of all the visible KDCs in the full SAURON sample, and find two types of components: kiloparsec-scale KDCs, which are older than 8 Gyr, and are found in galaxies with little net rotation; and compact KDCs, which have intrinsic diameters of less than a few hundred parsec, show a range of stellar ages from 0.5 - 15 Gyr (with 5/6 younger than 5 Gyr), are found exclusively in fast-rotating galaxies, and are close to counter-rotating around the same axis as their host. Of the 7 galaxies in the SAURON sample with integrated luminosity-weighted ages less than 5 Gyr, 5 show such compact KDCs, suggesting a link between counter-rotation and recent star-formation. We show that this may be partly due to a combination of small sample size at young ages, and an observational bias, since young KDCs are easier to detect than their older and/or co-rot ating counterparts.
Intrinsic Shape of Bulges in Disk Galaxies
Authors: Mendez-Abreu J. , Aguerri J. A. L. , Corsini E. M. , Simonneau E.
Published: April 2007

We analyzed the 2MASS images of a sample of 148 bright, nearby and unbarred galaxies to derive the photometric parameters of their bulge and disk by applying an accurate 2D decomposition algorithm. As a model for the bulge we have considered a system where the surfaces of equal density of light are coaxial and concentric ellipsoids with independent values of the principal axes A > B > C. If the emitting surfaces are concentric, coaxial but non-homologous ellipsoids, their projection on the plane of the sky will be concentric, non-homologous and non-coaxial ellipses (Stark 1977). Therefore if we identify the projected ellipses with the isophotal contours of a bulge, the observed twist between the position angle of the bulge and disk components can be understood as a hint for triaxiality.

Following the procedure described by Simonneau et al. (1998), we are able to express the intrinsic semi-axis values (A, B, C) of the triaxial ellipsoid as a function of the semi-axis measured on to its projected ellipse (a, b), position angle of the ellipse (δ), and angles which define the line of sight with respect to the ellipsoid (θ, φ).

However, since the φ angle is observationally undetermined, the intrinsic shape of bulges is still an ambiguous problem. Thus, it is customary to resort to a statistical approach for deducing the probability distribution function (PDF) of the intrinsic axis ratio of bulges. Since we have already inverted the problem, putting the intrinsic variables as a function of the measured variables (E, δ) and the variables (θ, φ) which are defined in a probabilistic way, and we have assumed that they are independent, the PDF can be determined simply by the multiplication of the integrated single probabilities of these variables.

We have found that integrating the derived PDF over the different ellipsoid regions (prolate, triaxial and oblate), ~45% of bulges have a triaxial structure, about 26% are oblate ellipsoids, 23% are prolate ellipsoids and the remaining 5% are spherical.

A typical bulge from our PDF, calculated as the mean value of the axis ratios of the ellipsoids weighted with the PDF, have axis ratios =1.66 and =1.34. This means that the axis ratio in the equatorial plane of the galaxy is B/A=0.81, the ratio between the major and the polar axis is C/A=0.60 and the triaxiality parameter is T=0.55, which is in good agreement with the previous results by Bertola et al. (1991).

We also found a correlation between the Sérsic index and the intrinsic flattening of the bulges. We observed that bulges tend to be less flattened (C/A=0.64) in more-concentrated galaxies (n > 2) and more flattened (C/A=0.54) in less-concentrated galaxies.
The Role of the Radial Orbit Instability in Dark Matter Halo Formation and Structure
Authors: Meyer J. M. , Dalcanton J. J. , Quinn T. R. , Williams L. L. R. , Barnes E. I. , Babul A. , Austin C. G. , Maas R.
Published: April 2007

For nearly a decade, N-body simulations have revealed a nearly universal dark matter density profile. This density profile appears to be robust to changes in the overall density of the universe and the underlying power spectrum. Despite its universality, however, the physical origin of this profile has not yet been well understood. Semi-analytic models have suggested that scale lengths in dark matter halos may be determined by the onset of the radial orbit instability. We have tested this theory using N-body simulations of collapsing dark matter halos. The resulting halo structures are prolate in shape, due to the mild aspect of the instability. We find that the radial orbit instability sets a scale length at which the velocity dispersion changes rapidly from isotropic to radially anisotropic. Preliminary analysis suggests that this scale length is proportional to the radius at which the density profile changes shape, as is the case in the semi-analytic models; however, the coefficient of proportionality is different by a factor of ~2. We conclude that the radial orbit instability may be a key physical mechanism responsible for the nearly universal profiles of simulated dark matter halos.
Fuelling of Circumnuclear Regions: 3D Spectroscopy View.
Authors: Moiseev A. V. , Smirnova A. A.
Published: April 2007

We review the results recently obtained by means of panoramic (3D) spectroscopy on the 6-m telescope BTA (SAO RAS). This research is devoted to observational evidences of gas inflow into the centers of galaxies, which must ensure the fueling of an active nucleus. 3D spectroscopy allows us to trace the behavior of gas and stars in the one-kiloparsec size vicinity of an AGN and also far from the center.
Evolution of the Galactic Disk from a Local Sample
Authors: Nordström B. , Andersen J. , Holmberg J.
Published: April 2007

The Geneva-Copenhagen Survey (Nordström et al., 2004) gives ages, metallicities, velocities, and Galactic orbits for a complete, magnitude-limited sample of 14,000 F and G dwarfs. We have verified the calibrations used in the GCS, improved those of Teff, [Fe/H], distance, and age from uvby β, and checked the effect on the resulting Galactic relations by end- to-end numerical simulations. All the main results of the GCS remain unchanged.
Mass and Spatial Distributions of Subhaloes in ΛCDM Cosmological Simulations
Authors: Nurmi P. , Heinämäki P. , Holopainen J. , Pihajoki P. , Saar E. , Einasto M. , Einasto J.
Published: April 2007

We study subhalo populations surrounding massive dark matter haloes by using three AMIGA simulations each having different mass and spatial resolutions. Our analysis shows that the slope of the subhalo mass function has a value 0.9, which agrees with previous studies. The dependence of mass functions on redshift is the same for subhaloes and main haloes. In all simulations, combined subhalo masses are about 0.1-0.2 of main halo masses and this mass fraction increases slightly with redshift and the mass of the main halo. The distribution of mass fractions for subhaloes is close to Gaussian at z = 0 and differs slightly at earlier epochs. Spatial distribution of subhaloes as measured in units of virial radius Rvir of the main halo does not depend on redshift and follows r1/3 rule. Spatial distribution of all haloes surrounding main haloes continues up to 3 times Rvir with equal slope but lower amplitude. Beyond 16 times Rvir, the average distribution of haloes becomes uniform.
A Missing Link in Galaxy Evolution: The Mysteries of Dissolving Star Clusters
Authors: Pellerin Anne , Meyer Martin , Harris Jason , Calzetti Daniela
Published: April 2007

Assuming that most stars form in clusters (Lada & Lada 2003), one might initially expect to find most massive stars in stellar clusters and to detect most of the UV emission in young compact stellar clusters. However, Meurer et al. (1995) showed that in starburst galaxies only 20% of the UV emission at 2200Å is detected in clusters while 80% is diffuse emission from sources in the inter-cluster medium. This phenomenon is also observed for normal galaxies (Hoopes et al. 2001).
Deprojecting Edge-on Disk Galaxies
Authors: Pohlen M. , Zaroubi S. , Peletier R.F.
Published: April 2007

The results of a pilot study on the intrinsic 3D distribution of stars in edge-on disk galaxies are presented. The 3D disk structure of a sample of 12 edge-on galaxies has been reconstructed through a direct deprojection of the observed two-dimensional images. The deprojection method – which utilises the so called Fourier slice theorem and assumes axial symmetry – has been tested with a large set of artificial galaxy models seen under a variety of inclinations (i = 80–90°) and with different spatial dust and optical depths distributions.
Bidimensional Fourier Analysis of a OSUBSGS Spiral Galaxies Sample
Authors: Puerari Ivânio , Valdez-Gutiérrez Margarita , Hernández-López Izbeth
Published: April 2007

By using bidimensional Fourier techniques, we have analyzed H (1.6μm) images of a sample of 48 spiral galaxies taken from the OSUBSGS. We found that two-armed spirals (m = 2) are the more important structures in the sample, but some galaxies present higher m = 1 (lopsided) or m = 3 (three armed spirals). A weak correlation between m = 2 pitch angles and Eskridge et al. (2002) classification is also evident, but there is no correlation at all between those angles and RC3 classification or Elmegreen arm class.
Analytical Galactic Models with Mild Central Cusps
Authors: Rindler-Daller Tanja
Published: April 2007

We present a new class of spherical galactic models with mild central cusps whose distribution function (DF) and intrinsic velocity dispersion (IV) can be represented analytically in a unified way in terms of hypergeometric functions for a large number of parameters. This allows an easy comparison of these quantities for models having varying degrees of central cuspiness or outer density falloff. In particular, we study the models for the innermost regions of galaxies harbouring mild cuspy centers with or without supermassive black holes (SBH). Important properties infered from the observed behaviour of the velocity dispersions can be reproduced.
A Semi-Analytic Approach to Understanding the Bimodality of GCs in the Milky Way & M31
Authors: Rothberg B. , Somerville R. , Whitmore B. , Harris W.
Published: April 2007

One of the most important results in the study of Globular Clusters (GC) has been the discovery of bimodality in the broad-band colors of many systems. Observations of the Milky Way, M31 and Centaurus A strongly suggest this is a bi-modality in metallicity. One method of constraining, and perhaps better understanding the observed bimodality of GCs is to use semi-analytic models (SAMs) to test both the galaxy and GC formation scenarios. We present the results of a study to test whether SAMs can accurately reproduce the physical characteristics of both the parent galaxy (including luminosity, mass and metallicity) and GC populations. The focus of the work is to test whether the SAMs are capable of reproducing the observed properties of spiral galaxies, in particular the Milky Way and M31, and what, if any, constraints this may place on the formation scenarios of GCs. Among the results are indications that bimodality may be directly connected with reionization at z ~ 7–8.
Sticky-Particle Simulations of Barred Galaxies
Authors: Salo Heikki , Laurikainen E. , Rautiainen P. , Buta R.
Published: April 2007

We use sticky-particle simulations to estimate the bar pattern speeds in disk galaxies over a wide range of Hubble types. For early types our results agree with the fast rotation found in previous kinematical measurements, while for later types significantly slower bars are found. Slow bars tend to be small, and favor less luminous galaxies, for a given bulge-to-total ratio.
Features of Fundamental Plane for Early-Type Galaxies by Clausius' Virial theory
Authors: Secco L.
Published: April 2007

The theory of the Fundamental Plane (FP) proposed by Secco (2005) is based on the existence of a maximum in the Clausius' Virial (CV) potential energy of a stellar component when it is completely embedded inside a dark matter (DM) halo. At the first order approximation the theory was developed by modeling the two-components with two power-law density profiles and it produces some expectations in fairly good agreement with the observations. We add other predictions of the theory at the same level of approximation about the Zone of Exclusion (ZOE) in k-space and its possible relationship with cosmological scenario. Some of the consequences of the thermodynamical properties of CV maximum are also taken into account.
A New Mass Model for M31
Authors: Seigar Marc S. , Barth Aaron J. , Bullock James S.
Published: April 2007

A new mass model for M31 is presented. The best possible baryonic mass profile for M31 is derived from the 2MASS Ks-band image and M/L ratios from Bell et al. (2003). The best fitting rotation curve is then found within the context of ΛCDM disk galaxy formation. We find that M31 is well-described by a model that includes an adiabatically contracted halo, with an initial NFW concentration, c = 20. Models without adiabatic contraction fail to reproduce the observed rotation curve at r>15 kpc. The derived halo virial mass is Mvir = (9.4 ± 0.8) × 1011M⊙, consistent with masses derived from other observational methods.
Panoramic Spectroscopy of Sy Galaxies with elongated radio structures
Authors: Smirnova A. A. , Moiseev A. V.
Published: April 2007

We have studied the ionized gas and stellar kinematics in several galaxies with active nuclei and elongated radio structures using 3D spectroscopy. The observations were performed at the SAO RAS 6-m telescope with the integral-field spectrograph MPFS (Afanasiev et al. 2001) and with a scanning Fabry-Perot interferometer (FPI) in the multimode device SCORPIO (Afanasiev & Moiseev 2005). Based on these data the intensity maps and velocity fields in the different emission lines of the ionizing gas were constructed. Using the lines-ratio diagrams we tried to search a source of the gas ionization: an active nucleus, hot young stars or shock waves.
The RAVE Survey: Constraining the Local Galactic Escape Speed
Authors: Smith Martin C. , Ruchti G. R. , Helmi A. , Wyse R. F. G. ,   the RAVE collaboration
Published: April 2007

We report new constraints on the local escape speed of our Galaxy. Our analysis is based on a sample of high velocity stars from the RAVE survey and two previously published datasets (the Geneva-Copenhagen survey and the Beers et al. catalogue of metal-poor stars). We use cosmological simulations of disk galaxy formation to motivate our assumptions on the shape of the velocity distribution, allowing for a significantly more precise measurement of the escape velocity compared to previous studies. We find that the escape velocity lies within the range 492 km s−1 < vesc <594 kms (90% confidence), with a median likelihood of 536 kms. The fact that v2esc is significantly greater than 2v2circ implies that there must be a significant amount of mass exterior to the Solar circle, i.e. this convincingly demonstrates the presence of a dark halo in the Galaxy. For a simple isothermal halo, one can calculate that the minimum radial extent is ~54 kpc. We use our constraints on vesc to determine the mass of the Milky Way halo for three halo profiles. For example, an adiabatically contracted NFW halo model results in a virial mass of 1.31+0.97−0.49 × 1012M⊙ and virial radius of 297+60−44 kpc (90% confidence). For this model the circular velocity at the virial radius is 141+27−19kms. Although our halo masses are model dependent, we find that they are in good agreement with each other.
An f(R) Gravitation for Galactic Environments
Authors: Sobouti Y.
Published: April 2007

We propose [Sobouti, arXiv:astro-ph/0603302] an f(R) modification of GR, which admits of a modified Schwarzschild metric. In the weak field limit this amounts to adding a small logarithmic correction to the newtonian potential. A test star moving in such a spacetime acquires a constant speed at large distances. From observations of the velocity curves of spirals, this speed turns out to be proportional to the fourth root of the mass of the central body, in compliance with the Tully-Fisher relation. A variance of MOND emerges as a consequence of the formalism.
The Bimodality of Galaxy Populations Revisited Through Spectral Synthesis
Authors: Sodré L. , Mateus A. , Fernandes R. Cid , Stasińska G. , Schoenell W. , Gomes J. M.
Published: April 2007

We revisit the bimodality of the galaxy population seen in the local universe. We address this issue in terms of physical properties of galaxies, such as mean stellar ages and stellar masses, derived from the application of a spectral synthesis method to galaxy spectra from the SDSS. We show that the mean light-weighted stellar age of galaxies presents the best description of the bimodality seen in the galaxy population. The stellar mass has an additional role since most of the star-forming galaxies present in the local universe are low-mass galaxies. Our results give support to the existence of a ‘downsizing’ in galaxy formation, where nowadays massive galaxies tend to have stellar populations older than those found in less massive objects.
Optical 3D Spectroscopy of Seyfert Galaxies: Kinematics and Excitation of Gas in Centers
Authors: Stoklasová I. , Ferruit P. , Jungwiert B. , Emsellem E.
Published: April 2007

We present a set of optical observations of excited gas emission in the central kiloparsecs of nearby Seyfert galaxies, as obtained with the integral-field (3D) spectrograph OASIS. We map the 2D emission distribution as well as the gas kinematics, derive the electron density and estimate the extinction due to dust.
Deep RATAN-600 Surveys at the Declination of SS433 Carried Out in 1987-2000 at 7.6 and 2.7 cm
Authors: Soboleva N. S. , Temirova A. V. , Bursov N. N. , Zverev Yu. K.
Published: April 2007

New interest have appeared recently in observations of radio sources at the shortest radio wavelengths in connection with planned searches CMB radiation. A high sensitivity 2.7 cm receiver was installed at RATAN-600 in 1989. We discuss the results of deep surveys (“Cold”) of a ±10' strip of the sky centered on the declination of SS 433 covering an interval of 11h in R.A. carried out with the RATAN-600 telescope at 2.7 and 7.6 cm in 1987–2000.
Structure Formation in Anisotropic Disks
Authors: Vorobyov Eduard , Theis Christian
Published: April 2007

The majority of normal disk galaxies are characterized by non-axisymmetric structures like spirals or bars. These structural elements have been widely discussed in the literature as a result of gravitational instabilities which are connected to growing density waves or global instabilities of disks. A first insight into the properties of galactic discs was provided by linear stability analysis. However, a disadvantage of linear stability analysis remained its restriction to small perturbations, both in amplitude and wavelength. Thus, numerical simulations, especially hydrodynamical and stellar-hydrodynamical simulations became a primary tool for the analysis of galactic evolution.
Evolution of Spiral Galaxies in Modified Gravity
Authors: Tiret O. , Combes F.
Published: April 2007

We present N-body simulations performed in the framework of MOND. This work is based on a numerical resolution of the modified Poisson equation derived from a Lagrangian theory of MOND. This equation is a nonlinear partial differential equation, so we first developed a code that solves this kind of equations using multigrid techniques. We compared the dynamical behaviour of a typical isolated galaxy in Newton CDM model and MOND model. In this approach, pure stellar disc are considered. For the same value of the Toomre parameter (QT), galactic discs in MOND develop a bar instability sooner than in the DM model. In a second phase the MOND bars weaken while the DM bars continue to grow by exchanging angular momentum with the halo. The bar pattern speed evolves quite differently in the two models, this affects the position of resonance like the corotation and the peanut. Then we studied the evolution of several galactic discs representing the Hubble sequence, in both models. These simulations lead to a statistical bar frequency which is closer to observations for the MOND than the DM model.
The Kinematically Measured Pattern Speeds of NGC 2523 and NGC 4245
Authors: Treuthardt P. , Buta R.
Published: April 2007

We have applied the Tremaine-Weinberg method to the SB(r)b galaxy NGC 2523 and the SB(r)0/a galaxy NGC 4245 using the Calcium Triplet in order to determine their bar pattern speeds. Assuming an inclination of 53° and a distance of 49.5 Mpc, the pattern speed of NGC 2523 is 26.2 ± 6.1 km s−1 kpc−1. The pattern speed of NGC 4245 is 75.3 ± 31.2 km s−1 kpc−1, assuming an inclination of 35.4° and a distance of 12.7 Mpc. The ratio of the corotation radius to the bar radius of NGC 2523 and NGC 4245 is 1.3 ± 0.3 and 1.1 ± 0.5, respectively.
The 3D Topology of the Clausius Virial for Two Component Dynamical Models of Elliptical Galaxies
Authors: Valentinuzzi T. , Secco L. , D'Onofrio M. , Caimmi R. , Bindoni D.
Published: April 2007

As found in Secco (2000, 2001), the presence of a (non-baryonic) dark halo in large-scale celestial objects, can induce a scale length on the luminous spheroid through the occurrence of an unexpected maximum in the virial potential energy (Clausius Virial, CV). The above mentioned investigations were grounded on two cored power law density profiles, but the same result is shown to hold for more refined and realistic models.
A New Method for Corotation Determination in Spiral and Barred Galaxies
Authors: Zhang Xiaolei , Buta Ronald J.
Published: April 2007

The approaches proposed in the past for determining the pattern speeds and corotation radii of the density waves in spiral and barred galaxies are mostly limited in their scope and accuracy. In this work, we have developed a general approach for the determination of corotation radii, which is applicable to any galaxy whose density wave modes have reached quasi-steady state – a condition empirically found to be the case for most nearby disk galaxies. The method utilizes an azimuthal phase shift between the potential and the density distributions for the density wave modes, the existence and the radial variations of which are closely related to the dynamical mechanism leading to the secular evolution of the basic state of the same disk galaxies (Zhang 1996, ApJ, 457, 125). We have used this method to derive corotation radii of over 100 galaxies using the near-infrared images of the Ohio State University Bright Galaxy Survey (OSUBGS, Eskridge et al. 2002, ApJS, 143, 73).
Galactic Kinematics from Open Clusters
Authors: Zhu Zi
Published: April 2007

On the basis of the astrophysical parameters of the Galactic open clusters published in the recent years, we have selected ~300 clusters completely with all measurements of their kinematical parameters. Almost all the clusters have a heliocentric distance less than 3.0 kpc. Inspecting the velocity field defined by the sample, we found some 30 clusters that have extremely large peculiar motions. All the clusters with large peculiar velocities are distant objects further than 2 kpc from the Sun, and some of them have large Galactic height |z|>0.35 kpc. The age ranges of the clusters are from 4 Myr to 1 Gyr with the intermediate age of 50 Myr.
Galaxy Evolution in the Virgo Cluster
Authors: Vollmer Bernd
Published: April 2007

In the last years we have gained new insights on how ram pressure acts in detail on Virgo spiral galaxies. This has been possible due to the combination of new deep HIobservations, deep polarized radio continuum observations, and detailed dynamical modelling (sticky particles and MHD). As a major result a first complete ram pressure stripping time sequence could be established for the Virgo cluster.
Galaxy Environments in DEEP2: The Birth of the Red Sequence
Authors: Cooper Michael C. , Newman Jeffrey A.
Published: April 2007

The galaxy population at z ≲ 1 is effectively described as a combination of two distinct types: red, early-type galaxies lacking much star formation and blue, late-type galaxies with active star formation. For the red galaxy population, recent work by Bell et al. (2004) has shown that the number density of ~L* galaxies on the red sequence has risen by a factor of ~2 from z ~ 1 to z ~ 0. A variety of complementary observations suggests that the build-up of galaxies on the red sequence results from 2 distinct evolutionary trends: (1) the quenching of star formation in blue galaxies and their subsequent migration onto the red sequence and (2) the dissipationless or (“dry”) merging of red-sequence galaxies.
Panoramic Views of Cluster Evolution Since z = 3
Authors: Kodama Tadayuki , Tanaka M. , Tanaka Ichi , Kajisawa M.
Published: April 2007

We have been conducting PISCES project (Panoramic Imaging and Spectroscopy of Cluster Evolution with Subaru; Kodama et al. 2005) with making use of the wide-field imaging capability of Subaru. Our motivations are first to map out large scale structures and define local envioronments of galaxies therein, and then to investigate the variation in galaxy properties as a function of environment and mass. We have completed multi-colout imaging of 8 distant clusters between 0.4 < z < 1.3 so far, and we have mapped out filamentary/clumpy structures in and around the clusters across 15–30 Mpc scales (see some examples in Fig. 1). These two clusters have secure spectroscopic confirmation of the physical association of the structures to the main body of the clusters. From the photometric and spectroscopic properties of galaxies over a wide range in environment, we have found that the truncation of galaxies is seen in the outskirts of clusters rather than in cluster cores. We have also seen a clear environmental dependence of the “down-sizing” in the sense that the stage of down-sizing is delayed in lower density environments.
The Structure of Galaxies at Faint Light Levels: Probing Galaxy Assembly
Authors: Ferguson Annette M. N.
Published: April 2007

Many clues about the galaxy assembly process lurk in the faint outer regions of galaxies. Although quantitative study of these parts has been severely limited in the past, breakthroughs are now being made thanks to the combination of wide-area star counts, deep HST imagery and 8-m class spectroscopy. I highlight here some recent progress made on deciphering the fossil record encoded in the outskirts of our nearest large neighbours, M31 and M33.
K-band Evolution of Elliptical Galaxies in the Cluster Abell 2390 at z=0.23
Authors: Alizadeh M. , Fritz A. , Da Rocha C. , Ziegler B. L.
Published: April 2007

We investigate the near-infrared K-band evolution of early-type galaxies in the cluster of galaxies Abell2390 at z = 0.23. Using the Omega-Prime camera at the 3.5-m Calar Alto telescope deep imaging (texp = 53 min) over a 6' × 6' field has been obtained. The measured K-band magnitudes of 28 galaxies are combined with the spectroscopic and morphological data of Fritz et al. (2005) to construct the Faber-Jackson and Fundamental Plane relations in the NIR. By comparing our distant galaxies to a local sample of cluster ellipticals (Pahre 1999), we find on average a mild luminosity evolution for both scaling relations (ΔMK ~ 0.6 − 0.7 mag) compatible with passive evolution of the stellar populations.
Non Adiabatic Evolution of Elliptical Galaxies by Dynamical Friction
Authors: Arena S.E. , Bertin G. , Liseikina T. , Pegoraro F.
Published: April 2007

Many astrophysical problems, ranging from structure formation in cosmology to dynamics of elliptical galaxies, refer to slow processes of evolution of essentially collisionless self-gravitating systems. To determine the relevant quasi-equilibrium configuration at time t from given initial conditions, such slow evolution is often approximated in terms of adiabatic evolution. Here we focus on the slow process of evolution induced by dynamical friction of a spherical stellar system (the host galaxy) on a minority component of “satellites” (distributed in a spherical shell), to determine to what extent an adiabatic description might be applied.
Three-Dimensional MHD Simulations of a Subcluster Plasma Moving in Turbulent ICM
Authors: Asai N. , Fukuda N. , Matsumoto R.
Published: April 2007

We carried out 3D magnetohydrodynamic simulations of a subcluster moving in turbulent ICM by including anisotropic heat conduction. Since magnetic fields stretched along the subcluster surface suppress the heat conduction across the front, cold fronts are formed and sustained.
The Substructure in the Cluster Abell85
Authors: Bravo-Alfaro H. , Islas J.-M. , Caretta C.
Published: April 2007

We revisit the complex structure of the A85-A87 cluster, based on a volume complete VLA-HI imaging survey, as well as optical photometry and spectroscopy. HI imaging studies of a few nearby clusters have shown that most of the HI rich galaxies around clusters are located within infalling groups. The case of A 85 is a very peculiar one, with all the 11 HI-detected galaxies projected east of A 85, and all but one with much lower radial velocities (~ 15,000 km s−1 than the cluster's systemic velocity (16,500 km s−1) In order to quantify the degree of substructure in A 85 we estimate the parameter δ defined by Dressler and Schectman, and plot it in Fig. 1a: many large circles in the same area indicate a great possibility of substructuring (Bravo-Alfaro et al. 2007 in prep).
Automated Search for Gravitational Lensing Arcs and Interacting Galaxies in the Red Sequence Survey
Authors: Chiang P. S. , Chen S. Y. , Ip W. , Chen W. P.
Published: April 2007

We have developed a robust and efficient algorithm to identify gravitational lensing arcs and interacting galaxies. The algorithm has been applied to the Red Sequence Survey II (RCS II) data, and we demonstrate a few examples here.
Constraints on Elliptical Galaxy Formation from Dry Mergers
Authors: Comerford Julia M. , Quataert Eliot , Ma Chung-Pei
Published: April 2007

Recent observations suggest that dissipationless mergers of elliptical galaxies build up the population of massive early-type galaxies (Bell et al. 2004; Faber et al. 2006). This type of merger is observed in galaxy clusters (Tran et al. 2005) and predicted by semi-analytic models which find mass assembly times significantly later than star-formation times for the most massive elliptical galaxies (de Lucia & Blaizot 2006). Here, we use a semi-analytic model of minor mergers of dark matter halos to examine the role of dry minor mergers in elliptical galaxy formation.
AGES Observations of Abell1367 and its Outskirts
Authors: Cortese L. , Minchin R. F. , Auld R. R. , Davies J. I. , Catinella B. , Momjian E. , Rosenberg J. L. , O'Neil K. ,   The AGES Team
Published: April 2007

The Arecibo Galaxy Environment Survey (AGES, Auld et al. 2006) will map ~200 square degrees over the next years using the ALFA feed array at the 305-m Arecibo Telescope. AGES is specifically designed to investigate various galactic environments from local voids to interacting groups and cluster of galaxies. AGES will map 20 square degrees in the Coma-Abell1367 supercluster including the Abell cluster 1367 and its outskirts (up to ~2 virial radii). In Spring 2006 we nearly completed the observations of 5 square degrees in the range 11:34< RA< 11:54, 19:20<Dec<20:20 covering all the cluster core and part of its infalling region reaching a 5 sigma detection limit of M(HI)~4×108M⊙ (assuming a velocity width ~200 km~s−1) at the distance of Abell1367 (~92 Mpc). An HI selected sample has been extracted from the datacube obtaining a catalogue of fluxes, recessional velocities, positions and velocity widths. We present a preliminary analysis of the properties of the HI sources and report the discovery of HI diffuse features within interacting groups at the periphery of Abell1367.
Galaxy Preprocessing in a Starbrusting Group Infalling into Abell1367
Authors: Cortese L. , Gavazzi G. , Boselli A. , Franzetti P. , Kennicutt R. C. , O'Neil K. , Sakai S.
Published: April 2007

We present a multiwavelength analysis of a compact group infalling at high speed (~1700 km s−1) into the dynamically young cluster Abell 1367. Peculiar morphologies and unusually high Halpha emission are associated with two giant galaxies and at least ten dwarfs/extragalactic HII regions, making this group the region with the highest density of star formation activity ever observed in the local clusters. Moreover Halpha imaging observations reveal extraordinary complex trails of ionized gas behind the galaxies, with projected lengths exceeding 100 kpc. These unique cometary trails mark the gaseous trajectory of galaxies, witnessing their dive into the hot cluster intergalactic medium. Under the combined action of tidal forces among group members and the ram-pressure by the cluster ambient medium, the group galaxies were fragmented and the ionized gas was blown out. The properties of this group suggest that environmental effects within infalling groups may have represented a preprocessing step of the galaxy evolution during the high redshift cluster assembly phase.
Dynamical Evolution in Hickson Compact Groups using Intragroup Light
Authors: Da Rocha C. , Ziegler B. L. , de Oliveira C. Mendes
Published: April 2007

Most of the galaxies in the local universe are located in groups, in particular in small groups, and most of the transformations suffered by galaxies located in today's clusters are likely to have occurred in groups at higher redshifts. Understanding the formation and evolution of groups is essential to understand the whole picture of structures and galaxy build-up. Using multi-band photometry we studied the intragroup light component (IGL) observed in compact groups of galaxies in a subsample of Hickson's catalogue, an efficient tool for determining its stage of dynamical evolution and for mapping its gravitational potential. Applying the OV_WAV package, a wavelet based technique, we can identify the IGL independently of the main contaminating effects. The fractions of IGL detected range from 11% to 46%, with one group with no IGL detected. The colors are consistent with those for old stellar populations and the mean surface brightnesses range from 24.8 to 28.4 B mag arcsec−2. Using the IGL, along with other dynamical evolution indicators, we could establish an evolutionary sequence for our sample.
E+A Galaxies: Did They Lose The A to Become E?
Authors: De Rijcke Sven , Michielsen D. , Buyle P. , Pisano D. J. , Dejonghe H. , Freeman K.
Published: April 2007

We present deep HI observations of a sample of 9 nearby E+A galaxies (0.05 < z < 0.1). In 7 of them, we detected up to a few times 109 M⊙ of neutral gas, making the link between E+As and early-types less direct than previously thought.