67 research outputs found
Probing the stellar populations of early-type galaxies: the SAURON survey
The SAURON project will deliver two-dimensional spectroscopic data of a
sample of nearby early-type galaxies with unprecedented quality. In this paper,
we focus on the mapping of their stellar populations using the SAURON data, and
present some preliminary results on a few prototypical cases.Comment: 12 pages, 6 figures. ASP Conference, Galaxies: the Third Dimension,
Cozumel. Version with higher resolution figures available at
http://www-obs.univ-lyon1.fr/eric.emsellem/papers/cozumel_emsellem.ps.g
SAURON Observations of Disks in Early-Type Galaxies
We briefly describe the SAURON project, aimed at determining the intrinsic
shape and internal dynamics of spheroids. We focus here on the ability of
SAURON to identify gaseous and stellar disks and to measure their morphology
and kinematics. We illustrate some of our results with complete maps of
NGC3377, NGC3623, and NGC4365.Comment: 4 pages, 4 figures (newpasp.sty). To appear in ASP Conf. Series
"Galaxy Disks and Disk Galaxies", eds. J.G. Funes S.J. & E.M. Corsini.
Version with full resolution images available at
http://www.strw.leidenuniv.nl/~bureau/pub_list.htm
The Tilt of the Fundamental Plane: Three-quarters Structural Nonhomology, One-quarter Stellar Population
The variation of the mass-to-light ratios M/L of early type galaxies as
function of their luminosities L is investigated. It is shown that the tilt
beta=0.27 (in the B--band) of the fundamental plane relation M/L ~ L^{beta} can
be understood as a combination of two effects: about one-quarter (i.e. dbeta
=0.07) is a result of systematic variations of the stellar population
properties with increasing luminosity. The remaining three-quarters (i.e. dbeta
=0.2) can be completely attributed to nonhomology effects that lead to a
systematic change of the surface brightness profiles with increasing
luminosity. Consequently, the observed tilt in the K-band (beta=0.17) where
stellar population effects are negligible, is explained by nonhomology effects
alone. After correcting for nonhomology, the mean value of the mass-to-light
ratio of elliptical galaxies (M/L_B) is 7.1+-2.8 (1 sigma scatter).Comment: 8 pages, 3 figures, ApJL, 600, 39, minor changes made to match the
published versio
A Bar Signature and Central Disk in the Gaseous and Stellar Velocity Fields of NGC5448
We analyse SAURON kinematic maps of the inner kpc of the early-type (Sa)
barred spiral galaxy NGC5448. 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 disk-like system embedded in a large-scale rotating structure. We
focus on the [OIII] 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 which are consistent with the
large-scale bar detected via imaging. We also study optical and near infra-red
images to reveal the asymmetric extinction in NGC5448, and we recognise 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.Comment: 11 pages, 8 figures. Accepted for publication in MNRAS. Please find
high resolution version on http://www.astro.uu.se/~kambiz/DOC/paper-N5448.pd
Supermassive black holes from OASIS and SAURON integral-field kinematics
Supermassive black holes are a key element in our understanding of how
galaxies form. Most of the progress in this very active field of research is
based on just ~30 determinations of black hole mass, accumulated over the past
decade. We illustrate how integral-field spectroscopy, and in particular our
OASIS modeling effort, can help improve the current situation.Comment: 4 pages, 2 figures, LaTeX. To appear in the proceedings of IAU
Symposium 245 "Formation and Evolution of Galaxy Bulges", M. Bureau, E.
Athanassoula, and B. Barbuy, ed
Fast and Slow Rotators: The build-up of the Red Sequence
Using the unique dataset obtained within the course of the SAURON project, a
radically new view of the structure, dynamics and stellar populations of
early-type galaxies has emerged. We show that galaxies come in two broad
flavours (slow and fast rotators), depending on whether or not they exhibit
clear large-scale rotation, as indicated via a robust measure of the specific
angular momentum of baryons. This property is also linked with other physical
characteristics of early-type galaxies, such as: the presence of dynamically
decoupled cores, orbital structure and anisotropy, stellar populations and dark
matter content. I here report on the observed link between this baryonic
angular momentum and a mass sequence, and how this uniquely relates to the
building of the red sequence via dissipative/dissipationless mergers and
secular evolution.Comment: 4 pages, 1 figure. To appear in the Proceedings of IAU Symposium 245
"Formation and Evolution of Galaxy Bulges", Eds M. Bureau, E. Athanassoula,
and B. Barbu
Formation and evolution of S0 galaxies: a SAURON case study of NGC7332
We present SAURON integral-field observations of the S0 galaxy NGC7332.
Existing broad-band ground-based and HST photometry reveals a double disk
structure and a boxy bulge interpreted as a bar viewed close to edge-on. The
SAURON two-dimensional stellar kinematic maps confirm the existence of the bar
and inner disk but also uncover the presence of a cold counter-rotating stellar
component within the central 250 pc. The Hbeta and [OIII] emission line maps
show that the ionised gas has a complex morphology and kinematics, including
both a component counter-rotating with respect to the stars and a fainter
co-rotating one. Analysis of the absorption line-strength maps show that
NGC7332 is young everywhere. The presence of a large-scale bar can explain most
of those properties, but the fact that we see a significant amount of unsettled
gas, together with a few peculiar features in the maps, suggest that NGC7332 is
still evolving. Interactions as well as bar-driven processes must thus have
played an important role in the formation and evolution of NGC7332, and
presumably of S0 galaxies in general.Comment: 12 pages, 12 figures, accepted for publication in MNRA
Testing Mass Determinations of Supermassive Black Holes via Stellar Kinematics
We investigate the accuracy of mass determinations M_BH of supermassive black
holes in galaxies using dynamical models of the stellar kinematics. We compare
10 of our M_BH measurements, using integral-field OASIS kinematics, to
published values. For a sample of 25 galaxies we confront our new M_BH derived
using two modeling methods on the same OASIS data.Comment: 4 pages, 4 figures, LaTeX. To appear in "Hunting for the Dark: The
Hidden Side of Galaxy Formation", Malta, 19-23 Oct. 2009, eds. V.P.
Debattista and C.C. Popescu, AIP Conf. Ser., in pres
Late-type galaxies observed with SAURON: two-dimensional stellar and emission-line kinematics of 18 spirals
We present the stellar and gas kinematics of a sample of 18 nearby late-type spiral galaxies (Hubble types ranging from Sb to Sd), observed with the integral-field spectrograph SAURON at the 4.2-m William Herschel Telescope. SAURON covers the spectral range 4800-5380 Å, allowing us to measure the Hβ, Fe, Mgb absorption features and the emission in the Hβ line and the [O iii]λλ4959, 5007 Å and [N i]λλ5198, 5200 Å doublets over a 33 × 41-arcsec2 field of view. The maps cover the nuclear region of these late-type galaxies and in all cases include the entire bulge. In many cases the stellar kinematics suggests the presence of a cold inner region, as visible from a central drop in the stellar velocity dispersion. The ionized gas is almost ubiquitous and behaves in a complicated fashion: the gas velocity fields often display more features than the stellar ones, including wiggles in the zero-velocity lines, irregular distributions, ring-like structures. The line ratio [O iii]/Hβ often takes on low values over most of the field, probably indicating a wide-spread star formatio
The SAURON project - XXI : The spatially resolved UV-line strength relations of early-type galaxies
The unexpected rising flux of early-type galaxies at decreasing ultraviolet (UV) wavelengths is a long-standing mystery. One important observational constraint is the correlation between UVoptical colours and Mg2 line strengths found by Burstein et al. The simplest interpretation of this phenomenon is that the UV strength is related to the Mg line strength. Under this assumption, we expect galaxies with larger Mg gradients to have larger UV colour gradients. By combining UV imaging from GALEX, optical imaging from MDM and SAURON integral-field spectroscopy, we investigate the spatially resolved relationships between UV colours and stellar population properties of 34 early-type galaxies from the SAURON survey sample. We find that galaxies with old stellar populations show tight correlations between the far-UV (FUV) colours (FUV -V and FUV - NUV) and the Mg b index, H beta index and metallicity [Z/H]. The equivalent correlations for the Fe5015 index, a-enhancement [a/Fe] and age are present but weaker. We have also derived logarithmic internal radial colour, measured line strength and derived stellar population gradients for each galaxy and again found a strong dependence of the FUV -V and FUV - NUV colour gradients on both the Mg b line strength and the metallicity gradients for galaxies with old stellar populations. In particular, global gradients of Mg b and [Z/H] with respect to the UV colour [e.g. ?(Mg b)/(FUV - NUV) and ?[Z/H]/?(FUV - NUV)] across galaxies are consistent with their local gradients within galaxies, suggesting that the global correlations also hold locally. From a simple model based on multiband colour fits of UV upturn and UV-weak galaxies, we have identified a plausible range of parameters that reproduces the observed radial colour profiles. In these models, the centres of elliptical galaxies, where the UV flux is strong, are enhanced in metals by roughly 60 per cent compared to UV-weak regions.Peer reviewe
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