The structure and dynamics of Abell 1942

Aims. We present a dynamical analysis of the galaxy cluster Abell 1942 based on a set of 128 velocities obtained at the European Southern Observatory. Methods. Data on individual galaxies are presented and the accuracy of the determined velocities as some properties of the cluster are discussed. We have also made use of publicly available Chandra X-ray data. Results. We obtained an improved mean redshift value z = 0.22513 +/- 0.0008 and velocity dispersion sigma = 908(139)(+147) km s(-1). Our analysis indicates that inside a radius of similar to 1.5 h(70)(-1) Mpc (similar to 7 arcmin) the cluster is well relaxed, without any remarkable features and the X-ray emission traces the galaxy distribution fairly well. Two possible optical substructures are seen at similar to 5 arcmin from the centre in the northwest and the southwest directions, but are not confirmed by the velocity field. These clumps are, however, kinematically bound to the main structure of Abell 1942. X-ray spectroscopic analysis of Chandra data resulted in a temperature kT = 5.5+/-0.5 keV and metal abundance Z = 0.33 +/- 0.15 Z(circle dot). The velocity dispersion corresponding to this temperature using the T(X-sigma) scaling relation is in good agreement with the measured galaxy velocities. Our photometric redshift analysis suggests that the weak lensing signal observed to the south of the cluster and previously attributed to a ""dark clump"" is produced by background sources, possibly distributed as a filamentary structure.

Global properties of `ordinary` early-type galaxies: photometry and spectroscopy of stars and globular clusters in NGC 4494

We present a comprehensive analysis of the spatial, kinematic and chemical properties of stars and globular clusters (GCs) in the `ordinary` elliptical galaxy NGC 4494 using data from the Keck and Subaru telescopes. We derive galaxy surface brightness and colour profiles out to large galactocentric radii. We compare the latter to metallicities derived using the near-infrared Calcium Triplet. We obtain stellar kinematics out to similar to 3.5 effective radii. The latter appear flattened or elongated beyond similar to 1.8 effective radii in contrast to the relatively round photometric isophotes. In fact, NGC 4494 may be a flattened galaxy, possibly even an S0, seen at an inclination of similar to 45 degrees. We publish a catalogue of 431 GC candidates brighter than i(0) = 24 based on the photometry, of which 109 are confirmed spectroscopically and 54 have measured spectroscopic metallicities. We also report the discovery of three spectroscopically confirmed ultra-compact dwarfs around NGC 4494 with measured metallicities of -0.4 less than or similar to [Fe/H] less than or similar to -0.3. Based on their properties, we conclude that they are simply bright GCs. The metal-poor GCs are found to be rotating with similar amplitude as the galaxy stars, while the metal-rich GCs show marginal rotation. We supplement our analysis with available literature data and results. Using model predictions of galaxy formation, and a suite of merger simulations, we find that many of the observational properties of NGC 4494 may be explained by formation in a relatively recent gas-rich major merger. Complete studies of individual galaxies incorporating a range of observational avenues and methods such as the one presented here will be an invaluable tool for constraining the fine details of galaxy formation models, especially at large galactocentric radii.

The globular cluster kinematics and galaxy dark matter content of NGC 3923

This paper presents further results from our spectroscopic study of the globular cluster (GC) system of the group elliptical NGC 3923. From observations made with the GMOS instrument on the Gemini South Telescope, an additional 50 GC and ultra-compact dwarf (UCD) candidates have been spectroscopically confirmed as members of the NGC 3923 system. When the recessional velocities of these GCs are combined with the 29 GC velocities reported previously, a total sample of 79 GC/UCD velocities is produced. This sample extends to over 6 arcmin (>6 R-e similar to 30 kpc) from the centre of NGC 3923 and is used to study the dynamics of the GC system and the dark matter content of NGC 3923. It is found that the GC system of NGC 3923 displays no appreciable rotation, and that the projected velocity dispersion is constant with radius within the uncertainties. The velocity dispersion profiles of the integrated light and GC system of NGC 3923 are indistinguishable over the region in which they overlap. We find some evidence that the diffuse light and GCs of NGC 3923 have radially biased orbits within similar to 130 arcsec. The application of axisymmetric orbit-based models to the GC and integrated light velocity dispersion profiles demonstrates that a significant increase in the mass-to-light ratio (from M/L-V = 8 to 26) at large galactocentric radii is required to explain this observation. We therefore confirm the presence of a dark matter halo in NGC 3923. We find that dark matter comprises 17.5(-4.5)(+7.3) per cent of the mass within 1 R-e, 41.2(-10.6)(+18.2) per cent within 2 R-e and 75.6(-16.8)(+15.4) per cent within the radius of our last kinematic tracer at 6.9 R-e. The total dynamical mass within this radius is found to be 1.5(-0.25)(+0.4) x 10(12) M-circle dot. In common with other studies of large ellipticals, we find that our derived dynamical mass profile is consistently higher than that derived by X-ray observations, by a factor of around 2.

From inverted pendulum to N-link chain: inertial sensors-based assessment of movement kinematics and dynamics for functional evaluation and rehabilitation

Despite several clinical tests that have been developed to qualitatively describe complex motor tasks by functional testing, these methods often depend on clinicians' interpretation, experience and training, which make the assessment results inconsistent, without the precision required to objectively assess the effect of the rehabilitative intervention. A more detailed characterization is required to fully capture the various aspects of motor control and performance during complex movements of lower and upper limbs. The need for cost-effective and clinically applicable instrumented tests would enable quantitative assessment of performance on a subject-specific basis, overcoming the limitations due to the lack of objectiveness related to individual judgment, and possibly disclosing subtle alterations that are not clearly visible to the observer. Postural motion measurements at additional locations, such as lower and upper limbs and trunk, may be necessary in order to obtain information about the inter-segmental coordination during different functional tests involved in clinical practice. With these considerations in mind, this Thesis aims: i) to suggest a novel quantitative assessment tool for the kinematics and dynamics evaluation of a multi-link kinematic chain during several functional motor tasks (i.e. squat, sit-to-stand, postural sway), using one single-axis accelerometer per segment, ii) to present a novel quantitative technique for the upper limb joint kinematics estimation, considering a 3-link kinematic chain during the Fugl-Meyer Motor Assessment and using one inertial measurement unit per segment. The suggested methods could have several positive feedbacks from clinical practice. The use of objective biomechanical measurements, provided by inertial sensor-based technique, may help clinicians to: i) objectively track changes in motor ability, ii) provide timely feedback about the effectiveness of administered rehabilitation interventions, iii) enable intervention strategies to be modified or changed if found to be ineffective, and iv) speed up the experimental sessions when several subjects are asked to perform different functional tests.

Scaling and non-scaling of muscle activity, kinematics, and dynamics in sit-ups with different degrees of difficulty

The purpose of this study was to investigate how the CNS adjusts motor patterns for variants of a complex axial movement-the situp. Adjustments were induced by changing the support surface contact and mass distribution of the body. Healthy adults performed straight-legged sit-ups, 3 s in duration, with support added to or removed from the lumbar trunk, or with mass added to the head or to the legs. Each of these interventions either increased or decreased the difficulty of the task. The study addressed the extent to which changes in sit-up difficulty are compensated by scaling of muscle activity, kinematics, and dynamics versus the extent to which they are compensated by changing discretely the motor pattern. The analysis of muscle activity, kinematics, and dynamics focused on the first 30-40% of the sit-up-the trunk flexion phase-since this is the most critical part of the movement. Our results demonstrate that, in some respects, sit-up kinematics and dynamics scaled with difficulty, but in other respects, they did not. Muscle activity also scaled, in many respects, but in more difficult sit-ups, abdominal flexor activity decreased instead of increased. Non-scaling changes in these parameters suggest that complex movements, such as the sit-up, may require discrete changes in motor pattern in order to deal with large loads, which challenge the available leverage. (C) 2005 Elsevier Ltd. All rights reserved.

Kinematics, substructure and luminosity-weighted dynamics of six nearby galaxy groups

We have redefined group membership of six southern galaxy groups in the local universe (mean cz < 2000 km s(-1)) based on new redshift measurements from our recently acquired Anglo-Australian Telescope 2dF spectra. For each group, we investigate member galaxy kinematics, substructure, luminosity functions and luminosity-weighted dynamics. Our calculations confirm that the group sizes, virial masses and luminosities cover the range expected for galaxy groups, except that the luminosity of NGC 4038 is boosted by the central starburst merger pair. We find that a combination of kinematical, substructural and dynamical techniques can reliably distinguish loose, unvirialized groups from compact, dynamically relaxed groups. Applying these techniques, we find that Dorado, NGC 4038 and NGC 4697 are unvirialized, whereas NGC 681, NGC 1400 and NGC 5084 are dynamically relaxed.

Kinematics of galaxies in compact groups Studying the B-band Tully-Fischer relation

We obtained new Fabry-Perot data cubes and derived velocity fields, monochromatic, and velocity dispersion maps for 28 galaxies in the Hickson compact groups 37, 40, 47, 49, 54, 56, 68, 79, and 93. We also derived rotation curves for 9 of the studied galaxies, 6 of which are strongly asymmetric. Combining these new data with previously published 2D kinematic maps of compact group galaxies, we investigated the differences between the kinematic and morphological position angles for a sample of 46 galaxies. We find that one third of the unbarred compact group galaxies have position angle misalignments between the stellar and gaseous components. This and the asymmetric rotation curves are clear signatures of kinematic perturbations, probably because of interactions among compact group galaxies. A comparison between the B-band Tully-Fisher relation for compact group galaxies and for the GHASP field-galaxy sample shows that, despite the high fraction of compact group galaxies with asymmetric rotation curves, these lay on the TF relation defined by galaxies in less dense environments, although with more scatter. This agrees with previous results, but now confirmed for a larger sample of 41 galaxies. We confirm the tendency for compact group galaxies at the low-mass end of the Tully-Fisher relation (HCG 49b, 89d, 96c, 96d, and 100c) to have either a magnitude that is too bright for its mass (suggesting brightening by star formation) and/or a low maximum rotational velocity for its luminosity (suggesting tidal stripping). These galaxies are outside the Tully Fisher relation at the 1 sigma level, even when the minimum acceptable values of inclinations are used to compute their maximum velocities. Including such galaxies with nu < 100 km s(-1) in the determination of the zero point and slope of the compact group B-band Tully-Fisher relation would strongly change the fit, making it different from the relation for field galaxies, which has to be kept in mind when studying scaling relations of interacting galaxies, especially at high redshifts.

Insights on the Milky Way bulge formation from the correlations between kinematics and metallicity

Context. Two main scenarios for the formation of the Galactic bulge are invoked, the first one through gravitational collapse or hierarchical merging of subclumps, the second through secular evolution of the Galactic disc. Aims. We aim to constrain the formation of the Galactic bulge through studies of the correlation between kinematics and metallicities in Baade's Window (l = 1 degrees, b = -4 degrees) and two other fields along the bulge minor axis (l = 0 degrees, b = -6 degrees and b = -12 degrees). Methods. We combine the radial velocity and the [Fe/H] measurements obtained with FLAMES/GIRAFFE at the VLT with a spectral resolution of R = 20 000, plus for the Baade's Window field the OGLE-II proper motions, and compare these with published N-body simulations of the Galactic bulge. Results. We confirm the presence of two distinct populations in Baade's Window found in Hill et al. (2010, A&A, submitted): the metal-rich population presents bar-like kinematics while the metal-poor population shows kinematics corresponding to an old spheroid or a thick disc. In this context the metallicity gradient along the bulge minor axis observed by Zoccali et al. (2008, A&A, 486, 177), visible also in the kinematics, can be related to a varying mix of these two populations as one moves away from the Galactic plane, alleviating the apparent contradiction between the kinematic evidence of a bar and the existence of a metallicity gradient. Conclusions. We show evidence that the two main scenarios for the bulge formation co-exist within the Milky Way bulge.

Star formation in the intragroup medium and other diagnostics of the evolutionary stages of compact groups of galaxies

Context. Compact groups of galaxies are entities that have high densities of galaxies and serve as laboratories to study galaxy interactions, intergalactic star formation and galaxy evolution. Aims. The main goal of this study is to search for young objects in the intragroup medium of seven compact groups of galaxies: HCG 2, 7, 22, 23, 92, 100 and NGC 92 as well as to evaluate the stage of interaction of each group. Methods. We used Fabry-Perot velocity fields and rotation curves together with GALEX NUV and FUV images and optical R-band and HI maps. Results. (i) HCG 7 and HCG 23 are in early stages of interaction; (ii) HCG 2 and HCG 22 are mildly interacting; and (iii) HCG 92, HCG 100 and NGC 92 are in late stages of evolution. We find that all three evolved groups contain populations of young blue objects in the intragroup medium, consistent with ages < 100 Myr, of which several are younger than < 10 Myr. We also report the discovery of a tidal dwarf galaxy candidate in the tail of NGC 92. These three groups, besides containing galaxies that have peculiar velocity fields, also show extended HI tails. Conclusions. Our results indicate that the advanced stage of evolution of a group, together with the presence of intragroup HI clouds, may lead to star formation in the intragroup medium. A table containing all intergalactic HII regions and tidal dwarf galaxies confirmed to date is appended.

GHASP: an H alpha kinematic survey of spiral and irregular galaxies - IX. The near-infrared, stellar and baryonic Tully-Fisher relations

We studied, for the first time, the near-infrared, stellar and baryonic Tully-Fisher relations for a sample of field galaxies taken from a homogeneous Fabry-Perot sample of galaxies [the Gassendi HAlpha survey of SPirals (GHASP) survey]. The main advantage of GHASP over other samples is that the maximum rotational velocities were estimated from 2D velocity fields, avoiding assumptions about the inclination and position angle of the galaxies. By combining these data with 2MASS photometry, optical colours, HI masses and different mass-to-light ratio estimators, we found a slope of 4.48 +/- 0.38 and 3.64 +/- 0.28 for the stellar and baryonic Tully-Fisher relation, respectively. We found that these values do not change significantly when different mass-to-light ratio recipes were used. We also point out, for the first time, that the rising rotation curves as well as asymmetric rotation curves show a larger dispersion in the Tully-Fisher relation than the flat ones or the symmetric ones. Using the baryonic mass and the optical radius of galaxies, we found that the surface baryonic mass density is almost constant for all the galaxies of this sample. In this study we also emphasize the presence of a break in the NIR Tully-Fisher relation at M(H,K) similar to -20 and we confirm that late-type galaxies present higher total-to-baryonic mass ratios than early-type spirals, suggesting that supernova feedback is actually an important issue in late-type spirals. Due to the well-defined sample selection criteria and the homogeneity of the data analysis, the Tully-Fisher relation for GHASP galaxies can be used as a reference for the study of this relation in other environments and at higher redshifts.

HI aperture synthesis and optical observations of the pair of galaxies NGC 6907 and 6908

NGC 6908, an S0 galaxy situated in the direction of NGC 6907, was only recently recognized as a distinct galaxy, instead of only a part of NGC 6907. We present 21-cm radio synthesis observations obtained with the Giant Metrewave Radio Telescope (GMRT) and optical images and spectroscopy obtained with the Gemini-North telescope of this pair of interacting galaxies. From the radio observations, we obtained the velocity field and the H I column density map of the whole region containing the NGC 6907/8 pair, and by means of the Gemini multi-object spectroscopy we obtained high-quality photometric images and 5 angstrom resolution spectra sampling the two galaxies. By comparing the rotation curve of NGC 6907 obtained from the two opposite sides around the main kinematic axis, we were able to distinguish the normal rotational velocity field from the velocity components produced by the interaction between the two galaxies. Taking into account the rotational velocity of NGC 6907 and the velocity derived from the absorption lines for NGC 6908, we verified that the relative velocity between these systems is lower than 60 km s(-1). The emission lines observed in the direction of NGC 6908, not typical of S0 galaxies, have the same velocity expected for the NGC 6907 rotation curve. Some emission lines are superimposed on a broader absorption profile, which suggests that they were not formed in NGC 6908. Finally, the H I profile exhibits details of the interaction, showing three components: one for NGC 6908, another for the excited gas in the NGC 6907 disc and a last one for the gas with higher relative velocities left behind NGC 6908 by dynamical friction, used to estimate the time when the interaction started in (3.4 +/- 0.6) x 10(7) yr ago.

NGC 7097: THE ACTIVE GALACTIC NUCLEUS AND ITS MIRROR, REVEALED BY PRINCIPAL COMPONENT ANALYSIS TOMOGRAPHY

Three-dimensional spectroscopy techniques are becoming more and more popular, producing an increasing number of large data cubes. The challenge of extracting information from these cubes requires the development of new techniques for data processing and analysis. We apply the recently developed technique of principal component analysis (PCA) tomography to a data cube from the center of the elliptical galaxy NGC 7097 and show that this technique is effective in decomposing the data into physically interpretable information. We find that the first five principal components of our data are associated with distinct physical characteristics. In particular, we detect a low-ionization nuclear-emitting region (LINER) with a weak broad component in the Balmer lines. Two images of the LINER are present in our data, one seen through a disk of gas and dust, and the other after scattering by free electrons and/or dust particles in the ionization cone. Furthermore, we extract the spectrum of the LINER, decontaminated from stellar and extended nebular emission, using only the technique of PCA tomography. We anticipate that the scattered image has polarized light due to its scattered nature.

MASS DISTRIBUTION IN HICKSON COMPACT GROUPS OF GALAXIES

This study presents the mass distribution for a sample of 18 late-type galaxies in nine Hickson compact groups. We used Ha rotation curves (RCs) from high-resolution two-dimensional velocity fields of Fabry-Perot observations and the J-band photometry from the Two Micron All Sky Survey, in order to determine the dark halo and the visible matter distributions. The study compares two halo density profiles, an isothermal core-like distribution, and a cuspy one. We also compare their visible and dark matter distributions with those of galaxies belonging to cluster and field galaxies coming from two samples: 40 cluster galaxies of Barnes et al. and 35 field galaxies of Spano et al. The central halo surface density is found to be constant with respect to the total absolute magnitude similar to what is found for the isolated galaxies. This suggests that the halo density is independent of galaxy type and environment. We have found that core-like density profiles better fit the RCs than cuspy-like ones. No major differences have been found between field, cluster, and compact group galaxies with respect to their dark halo density profiles.

REVISITING THE FOSSIL GROUP CANDIDATES UGC 842 AND NGC 6034

We present a new insight on NGC 6034 and UGC 842, two groups of galaxies previously reported in the literature as being fossil groups. The study is based on optical photometry and spectroscopy obtained with the CTIO Blanco telescope and Sloan Digital Sky Survey archival data. We find that NGC 6034 is embedded in a large structure, dominated by three rich clusters and other small groups. Its first and next four ranked galaxies have magnitude differences in the r band and projected distances which violate the optical criteria to classify it as a fossil group. We confirm that the UGC 842 group is a fossil group, but with about half the velocity dispersion that is reported in previous works. The velocity distribution of its galaxies reveals the existence of two structures in its line of sight, one with sigma(nu) similar to 223 km s(-1) and another with sigma(nu) similar to 235 km s(-1), with a difference in velocity of similar to 820 km s(-1). The main structure is dominated by passive galaxies, while these represent similar to 60% of the second structure. The X-ray temperature for the intragroup medium of a group with such a velocity dispersion is expected to be kT similar to 0.5-1 keV, against the observed value of kT similar to 1.9 keV reported in the literature. This result makes UGC 842 a special case among fossil groups because (1) it represents more likely the interaction between two small groups, which warms the intragroup medium and/or (2) it could constitute evidence that member galaxies lost energy in the process of spiraling toward the group center, and decreased the velocity dispersion of the system. As far as we know, UGC 842 is the first low-mass fossil group studied in detail.

DENSITY PROFILE, VELOCITY ANISOTROPY, AND LINE-OF-SIGHT EXTERNAL CONVERGENCE OF SLACS GRAVITATIONAL LENSES

Data from 58 strong-lensing events surveyed by the Sloan Lens ACS Survey are used to estimate the projected galaxy mass inside their Einstein radii by two independent methods: stellar dynamics and strong gravitational lensing. We perform a joint analysis of these two estimates inside models with up to three degrees of freedom with respect to the lens density profile, stellar velocity anisotropy, and line-of-sight (LOS) external convergence, which incorporates the effect of the large-scale structure on strong lensing. A Bayesian analysis is employed to estimate the model parameters, evaluate their significance, and compare models. We find that the data favor Jaffe`s light profile over Hernquist`s, but that any particular choice between these two does not change the qualitative conclusions with respect to the features of the system that we investigate. The density profile is compatible with an isothermal, being sightly steeper and having an uncertainty in the logarithmic slope of the order of 5% in models that take into account a prior ignorance on anisotropy and external convergence. We identify a considerable degeneracy between the density profile slope and the anisotropy parameter, which largely increases the uncertainties in the estimates of these parameters, but we encounter no evidence in favor of an anisotropic velocity distribution on average for the whole sample. An LOS external convergence following a prior probability distribution given by cosmology has a small effect on the estimation of the lens density profile, but can increase the dispersion of its value by nearly 40%.