63 research outputs found
The X-shooter Lens Survey - II. Sample presentation and spatially resolved kinematics
We present the X-shooter Lens Survey (XLENS) data. The main goal of XLENS is
to disentangle the stellar and dark matter content of massive early-type
galaxies (ETGs), through combined strong gravitational lensing, dynamics and
spectroscopic stellar population studies. The sample consists of 11 lens
galaxies covering the redshift range from to and having stellar
velocity dispersions between and . All
galaxies have multi-band, high-quality HST imaging. We have obtained long-slit
spectra of the lens galaxies with X-shooter on the VLT. We are able to
disentangle the dark and luminous mass components by combining lensing and
extended kinematics data-sets, and we are also able to precisely constrain
stellar mass-to-light ratios and infer the value of the low-mass cut-off of the
IMF, by adding spectroscopic stellar population information. Our goal is to
correlate these IMF parameters with ETG masses and investigate the relation
between baryonic and non-baryonic matter during the mass assembly and structure
formation processes. In this paper we provide an overview of the survey,
highlighting its scientific motivations, main goals and techniques. We present
the current sample, briefly describing the data reduction and analysis process,
and we present the first results on spatially resolved kinematics.Comment: Accepted for publication in MNRA
The Structure & Dynamics of Massive Early-type Galaxies: On Homology, Isothermality and Isotropy inside one Effective Radius
Based on 58 SLACS strong-lens early-type galaxies with direct total-mass and
stellar-velocity dispersion measurements, we find that inside one effective
radius massive elliptical galaxies with M_eff >= 3x10^10 M_sun are
well-approximated by a power-law ellipsoid with an average logaritmic density
slope of = -dlog(rho_tot)/dlog(r)=2.085^{+0.025}_{-0.018} (random
error on mean) for isotropic orbits with beta_r=0, +-0.1 (syst.) and
sigma_gamma' <= 0.20^{+0.04}_{-0.02} intrinsic scatter (all errors indicate the
68 percent CL). We find no correlation of gamma'_LD with galaxy mass (M_eff),
rescaled radius (i.e. R_einst/R_eff) or redshift, despite intrinsic differences
in density-slope between galaxies. Based on scaling relations, the average
logarithmic density slope can be derived in an alternative manner, fully
independent from dynamics, yielding =1.959 +- 0.077. Agreement
between the two values is reached for =0.45 +- 0.25, consistent with
mild radial anisotropy. This agreement supports the robustness of our results,
despite the increase in mass-to-light ratio with total galaxy mass: M_eff ~
L_{V,eff}^(1.363+-0.056). We conclude that massive early-type galaxies are
structurally close-to homologous with close-to isothermal total density
profiles (<=10 percent intrinsic scatter) and have at most some mild radial
anisotropy. Our results provide new observational limits on galaxy formation
and evolution scenarios, covering four Gyr look-back time.Comment: Accepted for publication by ApJL; 4 pages, 2 figure
Hydrostatic models for the rotation of extra-planar gas in disk galaxies
We show that fluid stationary models are able to reproduce the observed,
negative vertical gradient of the rotation velocity of the extra-planar gas in
spiral galaxies. We have constructed models based on the simple condition that
the pressure of the medium does not depend on density alone (baroclinic instead
of barotropic solutions: isodensity and isothermal surfaces do not coincide).
As an illustration, we have successfully applied our method to reproduce the
observed velocity gradient of the lagging gaseous halo of NGC 891. The fluid
stationary models discussed here can describe a hot homogeneous medium as well
as a "gas" made of discrete, cold HI clouds with an isotropic velocity
dispersion distribution. Although the method presented here generates a density
and velocity field consistent with observational constraints, the stability of
these configurations remains an open question.Comment: 12 pages, 9 figures. Accepted for publication in Astronomy and
Astrophysic
Are the total mass density and the low-mass end slope of the IMF anticorrelated?
We conduct a detailed lensing, dynamics and stellar population analysis of
nine massive lens early-type galaxies (ETGs) from the X-Shooter Lens Survey
(XLENS). Combining gravitational lensing constraints from HST imaging with
spatially-resolved kinematics and line-indices constraints from VLT X-Shooter
(XSH) spectra, we infer the low-mass slope and the low cut-off mass of the
stellar Initial Mass Function (IMF): and
, respectively, for a
reference point with and R kpc. All the XLENS systems are consistent with an IMF slope steeper
than Milky Way-like. We find no significant correlations between IMF slope and
any other quantity, except for an anti-correlation between total dynamical mass
density and low-mass IMF slope at the 87% CL [ = ]. This anti-correlation is consistent with the low
redshift lenses found by Smith et al. (2015) that have high velocity
dispersions and high stellar mass densities but surprisingly shallow IMF
slopes.Comment: Accepted for publication in MNRAS Lette
Extracellular matrix and nuclear abnormalities in skeletal muscle of a patient with WalkerâWarburg syndrome caused by POMT1 mutation
AbstractWalkerâWarburg syndrome (WWS) is an autosomal recessive disorder characterized by congenital muscular dystrophy, structural eye abnormalities and severe brain malformations. We performed an immunohistochemical and electron microscopy study of a muscle biopsy from a patient affected by WWS carrying a homozygous frameshift mutation in O-mannosyltransferase 1 gene (POMT1). Îą-Dystroglycan glycosylated epitope was not detected in muscle fibers and intramuscular peripheral nerves. Laminin Îą2 chain and perlecan were reduced in muscle fibers and well preserved in intramuscular peripheral nerves. The basal lamina in several muscle fibers showed discontinuities and detachment from the plasmalemma. Most nuclei, including myonuclei and satellite cell nuclei, showed detachment or complete absence of peripheral heterochromatin from the nuclear envelope. Apoptotic changes were detected in 3% of muscle fibers. The particular combination of basal lamina and nuclear changes may suggest that a complex pathogenetic mechanism, affecting several subcellular compartments, underlies the degenerative process in WWS muscle
Planetary nebula kinematics in NGC 1316: a young Sombrero
Aims. We present positions and velocities for 796 planetary nebulae (PNe) in
the Fornax Brightest Cluster Galaxy NGC 1316 (Fornax A). The planetary nebulae
and existing kinematics are used to explore the rotation of this merger remnant
and constrain dynamical models. Methods. Using FORS2 on the VLT, the PN
velocities were measured using a counter-dispersed slitless-spectroscopy
technique that produced the largest-to-date sample outside of the Local Group.
Spherical, non-rotating, constant-anisotropy Jeans models were con- strained by
observations of the planetary nebulae and existing integrated light spectra.
Results. The two-dimensional velocity field indicates dynamically-important
rotation that rises in the outer parts, possibly due to the outward transfer of
angular momentum during the merger. The modeling indicates a high dark matter
content, particularly in the outer parts, that is consistent with previous
estimates from dynamical models, lensing and stellar population models.
Conclusions. The exceptionally large sample of PN velocities makes it possible
to explore the kinematics of NGC 1316 in detail. Comparing the results to other
early-type galaxies like NGC 1399 and NGC 4594 (M104, Sombrero), NGC 1316
represents a transi- tion phase from a major-merger event to a bulge-dominated
galaxy like NGC 4594
Game Based Learning on Urban Sustainability: The "Sustain" Project
SUSTAIN is an ERASMUS+ project with an innovative perspective on urban sustainability. Its target is to promote the importance of sustainability on the everyday problems of the cities among the students of higher education, which are the policy makers of tomorrow and the ones that will shape the future. In order to achieve its goals, the research team will develop a course that will be based on an interactive game with an analytical style of education. This game will allow students to learn about transportation sustainability and societal metabolism through playing. In addition, the research team will develop small and illustrative simulation models, which will make the definitions more concrete and allow students to experiment in a consequence-free environment. It is a quite innovative and hybrid perspective way of learning, in the sense that it will combine game-based learning with a cognitive and analytical style of education
Kinematics of diffuse ionized gas in the disk halo interface of NGC 891 from Fabry-P\'erot observations
The properties of the gas in halos of galaxies constrain global models of the
interstellar medium. Kinematical information is of particular interest since it
is a clue to the origin of the gas. Here we report observations of the
kinematics of the thick layer of the diffuse ionized gas in NGC 891 in order to
determine the rotation curve of the halo gas. We have obtained a Fabry-P\'erot
data cube in Halpha to measure the kinematics of the halo gas with angular
resolution much higher than obtained from HI 21 cm observations. The data cube
was obtained with the TAURUS II spectrograph at the WHT on La Palma. The
velocity information of the diffuse ionized gas extracted from the data cube is
compared to model distributions to constrain the distribution of the gas and in
particular the halo rotation curve. The best fit model has a central
attenuation tau_H-alpha=6, a dust scale length of 8.1 kpc, an ionized gas scale
length of 5.0 kpc. Above the plane the rotation curve lags with a vertical
gradient of -18.8 km/s/kpc. We find that the scale length of the H-alpha must
be between 2.5 and 6.5 kpc. Furthermore we find evidence that the rotation
curve above the plane rises less steeply than in the plane. This is all in
agreement with the velocities measured in the HI.Comment: A&A, in press. 13 pages, 19 figure
The Einstein Cross: constraint on dark matter from stellar dynamics and gravitational lensing
[Abridged] We present two-dimensional line-of-sight stellar kinematics of the
lens galaxy in the Einstein Cross, obtained with the GEMINI 8m telescope, using
the GMOS integral-field spectrograph. The velocity map shows regular rotation
up to ~100 km/s around the minor axis of the bulge, consistent with
axisymmetry. The velocity dispersion map shows a weak gradient increasing
towards a central (R<1") value of sigma_0=170+/-9 km/s. We deproject the
observed surface brightness from HST imaging to obtain a realistic luminosity
density of the lens galaxy, which in turn is used to build axisymmetric
dynamical models that fit the observed kinematic maps. We also construct a
gravitational lens model that accurately fits the positions and relative fluxes
of the four quasar images. We find that the resulting luminous and total mass
distribution are nearly identical around the Einstein radius R_E = 0.89", with
a slope that is close to isothermal, but which becomes shallower towards the
center if indeed mass follows light. The dynamical model fits to the observed
kinematic maps result in a total mass-to-light ratio (M/L)_dyn=3.7+/-0.5
M_sun/L_sun,I (in the I-band). This is consistent with the Einstein mass M_E =
1.54 x 10^10 M_sun divided by the (projected) luminosity within R_E, which
yields a total mass-to-light ratio of (M/L)_E=3.4 M_sun/L_sun,I, with an error
of at most a few per cent. We estimate from stellar populations model fits to
colors of the lens galaxy a stellar mass-to-light ratio (M/L)_* from 2.8 to 4.1
M_sun/L_sun,I. Although a constant dark matter fraction of 20 per cent is not
excluded, dark matter may play no significant role in the bulge of this ~L*
early-type spiral galaxy.Comment: 18 pages, 8 figures, published in ApJ, 2010, 719, 148
Dissecting the Gravitational Lens B1608+656. II. Precision Measurements of the Hubble Constant, Spatial Curvature, and the Dark Energy Equation of State
Strong gravitational lens systems with measured time delays between the
multiple images provide a method for measuring the "time-delay distance" to the
lens, and thus the Hubble constant. We present a Bayesian analysis of the
strong gravitational lens system B1608+656, incorporating (i) new, deep Hubble
Space Telescope (HST) observations, (ii) a new velocity dispersion measurement
of 260+/-15 km/s for the primary lens galaxy, and (iii) an updated study of the
lens' environment. When modeling the stellar dynamics of the primary lens
galaxy, the lensing effect, and the environment of the lens, we explicitly
include the total mass distribution profile logarithmic slope gamma' and the
external convergence kappa_ext; we marginalize over these parameters, assigning
well-motivated priors for them, and so turn the major systematic errors into
statistical ones. The HST images provide one such prior, constraining the lens
mass density profile logarithmic slope to be gamma'=2.08+/-0.03; a combination
of numerical simulations and photometric observations of the B1608+656 field
provides an estimate of the prior for kappa_ext: 0.10 +0.08/-0.05. This latter
distribution dominates the final uncertainty on H_0. Compared with previous
work on this system, the new data provide an increase in precision of more than
a factor of two. In combination with the WMAP 5-year data set, we find that the
B1608+656 data set constrains the curvature parameter to be -0.031 < Omega_k <
0.009 (95% CL), a level of precision comparable to that afforded by the current
Type Ia SNe sample. Asserting a flat spatial geometry, we find that, in
combination with WMAP, H_0 = 69.7 +4.9/-5.0 km/s/Mpc and w=-0.94 +0.17/-0.19
(68% CL), suggesting that the observations of B1608+656 constrain w as tightly
as do the current Baryon Acoustic Oscillation data. (abridged)Comment: 24 pages, 8 figures, revisions based on referee's comments, accepted
for publication in Ap
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