We analyze the stellar kinematics of 39 dwarf early-type galaxies (dEs) in the Virgo Cluster. Based on the specific stellar angular momentum lambda sub(Re) and the ellipticity, we find 11 slow ...rotators and 28 fast rotators. The fast rotators in the outer parts of the Virgo Cluster rotate significantly faster than fast rotators in the inner parts of the cluster. Moreover, 10 out of the 11 slow rotators are located in the inner 3degrees (D < 1 Mpc) of the cluster. The fast rotators contain subtle disk-like structures that are visible in high-pass filtered optical images, while the slow rotators do not exhibit these structures. In addition, two of the dEs have kinematically decoupled cores and four more have emission partially filling in the Balmer absorption lines. These properties suggest that Virgo Cluster dEs may have originated from late-type star-forming galaxies that were transformed by the environment after their infall into the cluster. The correlation between lambda sub(Re) and the clustercentric distance can be explained by a scenario where low luminosity star-forming galaxies fall into the cluster, their gas is rapidly removed by ram-pressure stripping, although some of it can be retained in their core, their star formation is quenched but their stellar kinematics are preserved. After a long time in the cluster and several passes through its center, the galaxies are heated up and transformed into slow rotating dEs.
We analyse Spectrographic Areal Unit for Research on Optical Nebulae (SAURON) kinematic maps of the inner kiloparsec of the early-type (Sa) barred spiral galaxy NGC 5448. The observed morphology and ...kinematics of the emission-line gas is patchy and perturbed, indicating clear departures from circular motion. The kinematics of the stars is more regular, and display a small inner disc-like system embedded in a large-scale rotating structure. We focus on the O iii gas, and use a harmonic decomposition formalism to analyse the gas velocity field. The higher order harmonic terms and the main kinematic features of the observed data are consistent with an analytically constructed simple bar model. The bar model is derived using linear theory, considering an m= 2 perturbation mode, and with bar parameters that are consistent with the large-scale bar detected via imaging. We also study optical and near infrared images to reveal the asymmetric extinction in NGC 5448, and we recognize that some of the deviations between the data and the analytical bar model may be due to these complex dust features. Our study illustrates how the harmonic decomposition formalism can be used as a powerful tool to quantify non-circular motions in observed gas velocity fields.
We present MUSE integral field spectroscopic data of the S0 galaxy NGC 3115 obtained during the instrument commissioning at the ESO Very Large Telescope (VLT). We analyse the galaxy stellar ...kinematics and stellar populations and present two-dimensional maps of their associated quantities. We thus illustrate the capacity of MUSE to map extra-galactic sources to large radii in an efficient manner, i.e. ~4 Re, and provide relevant constraints on its mass assembly. We probe the well-known set of substructures of NGC 3115 (nuclear disc, stellar rings, outer kpc-scale stellar disc, and spheroid) and show their individual associated signatures in the MUSE stellar kinematics and stellar populations maps. In particular, we confirm that NGC 3115 has a thin fast-rotating stellar disc embedded in a fast-rotating spheroid, and that these two structures show clear differences in their stellar age and metallicity properties. We emphasise an observed correlation between the radial stellar velocity, V, and the Gauss-Hermite moment, h3, which creates a butterfly shape in the central 15′′ of the h3 map. We further detect the previously reported weak spiral- and ring-like structures, and find evidence that these features can be associated with regions of younger mean stellar ages. We provide tentative evidence for the presence of a bar, although the V-h3 correlation can be reproduced by a simple axisymmetric dynamical model. Finally, we present a reconstruction of the two-dimensional star formation history of NGC 3115 and find that most of its current stellar mass was formed at early epochs (>12 Gyr ago), while star formation continued in the outer (kpc-scale) stellar disc until recently. Since z ~2 and within ~4 Re, we suggest that NGC 3115 has been mainly shaped by secular processes.
Dynamical models of NGC 3115 Emsellem, Eric; Dejonghe, Herwig; Bacon, Roland
Monthly notices of the Royal Astronomical Society,
03/1999, Letnik:
303, Številka:
3
Journal Article
Recenzirano
Odprti dostop
We present new dynamical models of the S0 galaxy N3115, making use of the available published photometry and kinematics as well as two-dimensional TIGER spectrography. The models are based on a ...detailed model of the luminosity distribution built using an MGE fit on HST/WFPC2 and ground-based photometric data. We first examined the kinematics in the central 40 arcsec in the light of two-integral f(E,J) models. Jeans equations were used to constrain the mass-to-light ratio, and the central dark mass, the existence of which was suggested by previous studies. The even part of the distribution function was then retrieved via the Hunter & Qian formalism. We thus confirmed that the velocity and dispersion profiles in the central region could be well-fitted with a two-integral model, given the presence of a central dark mass of ∼109 M⊙. However, no two-integral model could fit the h3 profile around a radius of about 25 arcsec where the outer disc dominates the surface brightness distribution. Three-integral analytical models were therefore built using a quadratic programming technique. These models showed that three-integral components do indeed provide a reasonable fit to the kinematics, including the higher Gauss—Hermite moments. Again, models without a central dark mass failed to reproduce the observed kinematics in the central arcsec. This clearly supports the presence of a nuclear black hole of at least 6.5×108 M⊙ in the centre of NGC 3115. These models were finally used to estimate the importance of the dark matter in the outer part of NGC 3115, suggested by the flat stellar rotation curve observed by Capaccioli et al. This study finally points out the difficulty of integrating independently published data in a coherent and consistent way, thus demonstrating the importance of taking into account the details of the instrumental setup and the reduction processes.
Using the IMACS integral-field unit (IFU) on the 6.5 m Magellan telescope, we have designed the first statistically significant investigation of the two-dimensional distribution and kinematics of ...ionized gas and stars in the central kiloparsec regions of a well-matched sample of Seyfert and inactive control galaxies selected from the Sloan Digital Sky Survey. The goals of the project are to use the fine spatial sampling (0.2 arcsec pixel super(-1)) and large wavelength coverage (4000-7000 A) of the IMACS-IFU to search for dynamical triggers of nuclear activity in the central region where active galactic nucleus (AGN) activity and dynamical timescales become comparable, to identify and assess the impact of AGN-driven outflows on the host galaxy and to provide a definitive sample of local galaxy kinematics for comparison with future three-dimensional kinematic studies of high-redshift systems. In this paper, we provide the first detailed description of the procedure to reduce and calibrate data from the IMACS-IFU in "long mode" to obtain two-dimensional maps of the distribution and kinematics of ionized gas and stars. The sample selection criteria are presented, the observing strategy is described, and resulting maps of the sample galaxies are presented along with a description of the observed properties of each galaxy and the overall observed properties of the sample.
tiger integral-field spectrography and Hubble Space Telescope Wide Field and Planetary Camera 2 (WFPC2) imaging of the E3 galaxy NGC 2974 are used to derive the kinematics of the stellar and ionized ...gas components in its central 500 pc. We derive a numerical two-integral distribution function from a multi-Gaussian expansion (MGE) mass model using the Hunter & Qian formalism. The tiger and published long-slit stellar kinematics, including higher-order moments, are well fitted with this self-consistent model, requiring neither the addition of a significant mass contribution from a hidden disc structure nor the presence of a central dark mass (at that spatial resolution). The data reveal the presence of a striking, highly contrasted, two-arm gaseous spiral structure within a radius of ∼200 pc, corresponding to a total mass of 6.8 × 104 solar masses of ionized gas. We use a deconvolved tiger data cube to probe its kinematics at a resolution of about 0.35 arcsec FWHM. Strong departures from circular motions are observed, as well as high velocity dispersion values on the inner side of the arms. We interpret the observed gas morphology and kinematics as the signature of streaming gas flows driven by a ∼540-pc diameter bar with Ωp= 700 ± 100 km s−1 kpc−1. This hypothesis is strongly supported by the predictions of a density wave model. This model predicts that the bar should lie at about 35° from the line of nodes, and implies gas inflow towards the central ∼50 pc. The quadrupole perturbation due to this bar is estimated to represent less than 2 per cent of the underlying gravitational potential (a maximum torque of about 10 per cent), explaining the lack of a direct detection via broad-band photometry in the visible. Despite its weakness, the inner bar of NGC 2974 may be able to drive some gas within a 10-pc radius. We suggest that the presence of such inner bars might be more common among early-type disc galaxies than is generally thought, and that deep high-resolution emission-line imagery may be the best way to detect such structures.
ABSTRACT
We have used the SAURON panoramic integral field spectrograph to study the structure of the Lyα emission‐line halo, LAB1, surrounding the submillimetre galaxy SMM J221726+0013. This ...emission‐line halo was discovered during a narrow‐band imaging survey of the z= 3.1 large‐scale structure in the SSA 22 region. Our observations trace the emission halo out to almost 100 kpc from the submillimetre source and identify two distinct Lyα‘mini‐haloes’ around the nearby Lyman‐break galaxies. The main emission region has a broad line profile, with variations in the line profile seeming chaotic and lacking evidence for a coherent velocity structure. The data also suggest that Lyα emission is suppressed around the submillimetre source. Interpretation of the line structure needs care because Lyα may be resonantly scattered, leading to complex radiative transfer effects, and we suggest that the suppression in this region arises because of such effects. We compare the structure of the central emission‐line halo with local counterparts, and find that the emission‐line halo around NGC 1275 in the Perseus cluster may be a good local analogue, although the high‐redshift halo is factor of ∼100 more luminous and appears to have higher velocity broadening. Around the Lyman‐break galaxy C15, the emission line is narrower, and a clear shear in the emission wavelength is seen. A plausible explanation for the line profile is that the emission gas is expelled from C15 in a bipolar outflow, similar to that seen in M82.
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