680 research outputs found
Injunction Against Prosecution of Divorce Actions in Other States
Aims: The formation scenario of extended counter-rotating stellar disks in galaxies is still debated. In this paper, we study the S0 galaxy IC 719 known to host two large-scale counter-rotating stellar disks in order to investigate their formation mechanism.
Methods: We exploit the large field of view and wavelength coverage of the Multi Unit Spectroscopic Explorer (MUSE) spectrograph to derive two-dimensional (2D) maps of the various properties of the counter-rotating stellar disks, such as age, metallicity, kinematics, spatial distribution, the kinematical and chemical properties of the ionized gas, and the dust map.
Results: Due to the large wavelength range, and in particular to the presence of the Calcium Triplet \u3bb\u3bb8498, 8542, 8662 \uc5 (CaT hereafter), the spectroscopic analysis allows us to separate the two stellar components in great detail. This permits precise measurement of both the velocity and velocity dispersion of the two components as well as their spatial distribution. We derived a 2D map of the age and metallicity of the two stellar components, as well as the star formation rate and gas-phase metallicity from the ionized gas emission maps.
Conclusions: The main stellar disk of the galaxy is kinematically hotter, older, thicker and with larger scale-length than the secondary disk. There is no doubt that the latter is strongly linked to the ionized gas component: they have the same kinematics and similar vertical and radial spatial distribution. This result is in favor of a gas accretion scenario over a binary merger scenario to explain the origin of counter-rotation in IC 719. One source of gas that may have contributed to the accretion process is the cloud that surrounds IC 719
Metallicity of the polar disk in NGC4650A: constraints for cold accretion scenario
We used high resolution spectra in the optical and near-infrared wavelength
range to study the abundance ratios and metallicities of the HII regions
associated with the polar disk in NGC4650A, in order to put constraints on the
formation of the polar disk through cold gas accretion along a filament; this
might be the most realistic way by which galaxies get their gas. We have
compared the measured metallicities for the polar structure in NGC4650A with
those of different morphological types and we have found that they are similar
to those of late-type galaxies: such results is consistent with a polar disk
formed by accretion from cosmic web filaments of external cold gas.Comment: Proceeding of the conference "Hunting for the Dark: The Hidden Side
of Galaxy Formation", Malta, 19-23 Oct. 200
The pseudobulge of NGC 1292
The photometric and kinematic properties of Sb NGC 1292 suggest it hosts a
pseudobulge. The properties of the stellar population of such a pseudobulge are
consistent with a slow buildup within a scenario of secular evolution.Comment: 2 pages, 1 figure to appear in the proceedings of "Formation and
Evolution of Galaxy Disks", Rome, October 2007, Eds. J. Funes and E. M.
Corsin
Dynamical modelling of luminous and dark matter in 17 Coma early-type galaxies
Dynamical models for 17 Coma early-type galaxies are presented. The galaxy
sample consists of flattened, rotating as well as non-rotating early-types
including cD and S0 galaxies with luminosities between M=-18.79 and M=-22.56.
Kinematical long-slit observations cover at least the major and minor axis and
extend to 1-4 effective radii. Axisymmetric Schwarzschild models are used to
derive stellar mass-to-light ratios and dark halo parameters. In every galaxy
models with a dark matter halo match the data better than models without. The
statistical significance is over 95 percent for 8 galaxies, around 90 percent
for 5 galaxies and for four galaxies it is not significant. For the highly
significant cases systematic deviations between observed and modelled
kinematics are clearly seen; for the remaining galaxies differences are more
statistical in nature. Best-fit models contain 10-50 percent dark matter inside
the half-light radius. The central dark matter density is at least one order of
magnitude lower than the luminous mass density. The central phase-space density
of dark matter is often orders of magnitude lower than in the luminous
component, especially when the halo core radius is large. The orbital system of
the stars along the major-axis is slightly dominated by radial motions. Some
galaxies show tangential anisotropy along the minor-axis, which is correlated
with the minor-axis Gauss-Hermite coefficient H4. Changing the balance between
data-fit and regularisation constraints does not change the reconstructed mass
structure significantly. Model anisotropies tend to strengthen if the weight on
regularisation is reduced, but the general property of a galaxy to be radially
or tangentially anisotropic, respectively, does not change. (abridged)Comment: 31 pages, 34 figures; accepted for publication in MNRA
Using 3D Spectroscopy to Probe the Orbital Structure of Composite Bulges
Detailed imaging and spectroscopic analysis of the centers of nearby S0 and
spiral galaxies shows the existence of "composite bulges", where both classical
bulges and disky pseudobulges coexist in the same galaxy. As part of a search
for supermassive black holes in nearby galaxy nuclei, we obtained VLT-SINFONI
observations in adaptive-optics mode of several of these galaxies.
Schwarzschild dynamical modeling enables us to disentangle the stellar orbital
structure of the different central components, and to distinguish the differing
contributions of kinematically hot (classical bulge) and kinematically cool
(pseudobulge) components in the same galaxy.Comment: LaTeX, 2 pages, 1 PDF figure. To appear in "Proceedings of IAU
Symposium 309: Galaxies in 3D across the Universe", eds. B. L. Ziegler, F.
Combes, H. Dannerbauer, and M. Verdug
Spatially Resolved Spectroscopy of Coma Cluster Early-Type Galaxies - II. The Minor Axis Dataset
We present minor axis, offset major axis and one diagonal long slit spectra for 10 E and S0 galaxies of the Coma cluster drawn from a magnitude-limited sample studied before. We derive rotation curves, velocity dispersion profiles and the H3 and H4 coefficients of the Hermite decomposition of the line of sight velocity distribution. Moreover, we derive the line index profiles of Mg, Fe and Hβ line indices and assess their errors. The data will be used to construct dynamical models of the galaxies and study their stellar populations
Spatially Resolved Spectroscopy of Coma Cluster Early‐Type Galaxies. IV. Completing the Data Set
The long-slit spectra obtained along the minor axis, offset major axis, and diagonal axis are presented for 12 E and S0 galaxies of the Coma Cluster drawn from a magnitude-limited sample studied before. The rotation curves, velocity dispersion profiles, and the H3 and H4 coefficients of the Hermite decomposition of the line-of-sight velocity distribution are derived. The radial profiles of the Hβ, Mg, and Fe line strength indices are measured too. In addition, the surface photometry of the central regions of a subsample of four galaxies recently obtained with the Hubble Space Telescope is presented. The data will be used to construct dynamical models of the galaxies and study their stellar populations
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