2,532 research outputs found
Towards a new classification of early-type galaxies: an integral-field view
In this proceeding we make use of the two-dimensional stellar kinematics of a
representative sample of E and S0 galaxies obtained with the SAURON
integral-field spectrograph to reveal that early-type galaxies appear in two
broad flavours, depending on whether they exhibit clear large-scale rotation or
not. We measure the level of rotation via a new parameter LambdaR and use it as
a basis for a new kinematic classification that separates early-type galaxies
into slow and fast rotators. With the aid of broad-band imaging we will
reinforce this finding by comparing our kinematic results to the photometric
properties of these two classes.Comment: 4 pages, 2 figures, to appear in "Pathways Through an Eclectic
Universe", J. H. Knappen, T. J. Mahoney, and A. Vazedekis (Eds.), ASP Conf.
Ser., 200
Analytical and experimental characterization of a miniature calorimetric sensor in pulsatile flow
The behaviour of a miniature calorimetric sensor, which is under
consideration for catheter-based coronary artery flow assessment, is
investigated in both steady and pulsatile tube flow. The sensor is composed of
a heating element operated at constant power, and two thermopiles that measure
flow-induced temperature differences over the sensor surface.
An analytical sensor model is developed, which includes axial heat conduction
in the fluid and a simple representation of the solid wall, assuming a
quasi-steady sensor response to the pulsatile flow. To reduce the mathematical
problem, described by a two-dimensional advection-diffusion equation, a
spectral method is applied. A Fourier transform is then used to solve the
resulting set of ordinary differential equations and an analytical expression
for the fluid temperature is found. To validate the analytical model,
experiments with the sensor mounted in a tube have been performed in steady and
pulsatile water flow with various amplitudes and Strouhal numbers. Experimental
results are generally in good agreement with theory and show a quasi-steady
sensor response in the coronary flow regime. The model can therefore be used to
optimize the sensor design for coronary flow assessment
Dark Matter Fraction in Disk-Like Galaxies Over the Past 10 Gyr
We present an observational study of the dark matter fraction in star-forming
disk-like galaxies up to redshift , selected from publicly
available integral field spectroscropic surveys, namely KMOS3D}, KGES, and
KROSS. We provide novel observational evidence, showing that at a fixed
redshift, the dark matter fraction gradually increases with radius, indicating
that the outskirts of galaxies are dark matter dominated, similarly to local
star-forming disk galaxies. This observed dark matter fraction exhibits a
decreasing trend with increasing redshift. However, on average, the fraction
within the effective radius (upto outskirts) remains above 50\%, similar to
locals. Furthermore, we investigated the relationships between the dark matter,
baryon surface density, and circular velocity of galaxies. We observe a
decreasing trend in the dark matter fraction as baryon surface densities
increase, which is consistent across all stellar masses, redshift ranges, and
radii, with a scatter of 0.13 dex. On the other hand, the correlation between
the circular velocity at the outermost radius and the dark matter fraction
within this radius has a relatively low scatter (0.11 dex), but its slope
varies with stellar mass and with redshift, providing observational evidence of
the dynamical evolution of the interplay between the baryonic and dark matter
distributions with cosmic time. We observe that low stellar mass galaxies
() undergo a higher degree of
evolution, which may be attributed to the hierarchical merging of galaxies.Comment: Comments are welcom
Time transients in the quantum corrected Newtonian potential induced by a massless nonminimally coupled scalar field
We calculate the one loop graviton vacuum polarization induced by a massless,
nonminimally coupled scalar field on Minkowski background. We make use of the
Schwinger-Keldysh formalism, which allows us to study time dependent phenomena.
As an application we compute the leading quantum correction to the Newtonian
potential of a point particle. The novel aspect of the calculation is the use
of the Schwinger-Keldysh formalism, within which we calculate the time
transients induced by switching on of the graviton-scalar coupling.Comment: 22 pages, 5 figures; detailed calculation of the graviton vacuum
polarization moved to the new Appendix; matches published versio
A study of rotating globular clusters - the case of the old, metal-poor globular cluster NGC 4372
Aims: We present the first in-depth study of the kinematic properties and
derive the structural parameters of NGC 4372 based on the fit of a Plummer
profile and a rotating, physical model. We explore the link between internal
rotation to different cluster properties and together with similar studies of
more GCs, we put these in the context of globular cluster formation and
evolution. Methods: We present radial velocities for 131 cluster member stars
measured from high-resolution FLAMES/GIRAFFE observations. Their membership to
the GC is additionally confirmed from precise metallicity estimates. Using this
kinematic data set we build a velocity dispersion profile and a systemic
rotation curve. Additionally, we obtain an elliptical number density profile of
NGC 4372 based on optical images using a MCMC fitting algorithm. From this we
derive the cluster's half-light radius and ellipticity as r_h=3.4'+/-0.04' and
e=0.08+/-0.01. Finally, we give a physical interpretation of the observed
morphological and kinematic properties of this GC by fitting an axisymmetric,
differentially rotating, dynamical model. Results: Our results show that NGC
4372 has an unusually high ratio of rotation amplitude to velocity dispersion
(1.2 vs. 4.5 km/s) for its metallicity. This, however, puts it in line with two
other exceptional, very metal-poor GCs - M 15 and NGC 4590. We also find a mild
flattening of NGC 4372 in the direction of its rotation. Given its old age,
this suggests that the flattening is indeed caused by the systemic rotation
rather than tidal interactions with the Galaxy. Additionally, we estimate the
dynamical mass of the GC M_dyn=2.0+/-0.5 x 10^5 M_Sun based on the dynamical
model, which constrains the mass-to-light ratio of NGC 4372 between 1.4 and 2.3
M_Sun/L_Sun, representative of an old, purely stellar population.Comment: Accepted for publication in A&A, 12 pages, 14 figures, 2 table
Concerted involvement of Cdx/Hox genes and Wnt signaling in morphogenesis of the caudal neural tube and cloacal derivatives from the posterior growth zone
Decrease in Cdx dosage in an allelic series of mouse Cdx mutants leads to progressively more severe posterior vertebral defects. These defects are corrected by posterior gain of function of the Wnt effector Lef1. Precocious expression of Hox paralogous 13 genes also induces vertebral axis truncation by antagonizing Cdx function. We report here that the phenotypic similarity also applies to patterning of the caudal neural tube and uro-rectal tracts in Cdx and Wnt3a mutants, and in embryos precociously expressing Hox13 genes. Cdx2 inactivation after placentation leads to posterior defects, including incomplete uro-rectal septation. Compound mutants carrying one active Cdx2 allele in the Cdx4-null background (Cdx2/4), transgenic embryos precociously expressing Hox13 genes and a novel Wnt3a hypomorph mutant all manifest a comparable phenotype with similar uro-rectal defects. Phenotype and transcriptome analysis in early Cdx mutants, genetic rescue experiments and gene expression studies lead us to propose that Cdx transcription factors act via Wnt signaling during the laying down of uro-rectal mesoderm, and that they are operative in an early phase of these events, at the site of tissue progenitors in the posterior growth zone of the embryo. Cdx and Wnt mutations and premature Hox13 expression also cause similar neural dysmorphology, including ectopic neural structures that sometimes lead to neural tube splitting at caudal axial levels. These findings involve the Cdx genes, canonical Wnt signaling and the temporal control of posterior Hox gene expression in posterior morphogenesis in the different embryonic germ layers. They shed a new light on the etiology of the caudal dysplasia or caudal regression range of human congenital defects.AICR project grant: (08-0199); Dutch Earth and Life Sciences grant: (820.02.005); 6th Framework Programme Network of Excellence `Cells into Organs'; Dutch government grant: (Bsik Program 03038); Fundação para a Ciência e Tecnologia grant: (PTDC/BIA-BCM/110638/2009); Centro de Biologia do Desenvolvimento grant: (POCTI-ISFL-4-664)
Virtual Resection: A New Tool for Preparing for Nephron-Sparing Surgery in Wilms Tumor Patients
Nephron-sparing surgery (NSS) in Wilms tumor (WT) patients is a surgically challenging procedure used in highly selective cases only. Virtual resections can be used for preoperative planning of NSS to estimate the remnant renal volume (RRV) and to virtually mimic radical tumor resection. In this single-center evaluation study, virtual resection for NSS planning and the user experience were evaluated. Virtual resection was performed in nine WT patient cases by two pediatric surgeons and one pediatric urologist. Pre- and postoperative MRI scans were used for 3D visualization. The virtual RRV was acquired after performing virtual resection and a questionnaire was used to assess the ease of use. The actual RRV was derived from the postoperative 3D visualization and compared with the derived virtual RRV. Virtual resection resulted in virtual RRVs that matched nearly perfectly with the actual RRVs. According to the questionnaire, virtual resection appeared to be straightforward and was not considered to be difficult. This study demonstrated the potential of virtual resection as a new planning tool to estimate the RRV after NSS in WT patients. Future research should further evaluate the clinical relevance of virtual resection by relating it to surgical outcome
Observational constraints to boxy/peanut bulge formation time
Boxy/peanut bulges are considered to be part of the same stellar structure as
bars and both could be linked through the buckling instability. The Milky Way
is our closest example. The goal of this letter is determining if the mass
assembly of the different components leaves an imprint in their stellar
populations allowing to estimate the time of bar formation and its evolution.
To this aim we use integral field spectroscopy to derive the stellar age
distributions, SADs, along the bar and disc of NGC 6032. The analysis shows
clearly different SADs for the different bar areas. There is an underlying old
(>=12 Gyr) stellar population for the whole galaxy. The bulge shows star
formation happening at all times. The inner bar structure shows stars of ages
older than 6 Gyrs with a deficit of younger populations. The outer bar region
presents a SAD similar to that of the disc. To interpret our results, we use a
generic numerical simulation of a barred galaxy. Thus, we constrain, for the
first time, the epoch of bar formation, the buckling instability period and the
posterior growth from disc material. We establish that the bar of NGC 6032 is
old, formed around 10 Gyr ago while the buckling phase possibly happened around
8 Gyr ago. All these results point towards bars being long-lasting even in the
presence of gas.Comment: Accepted for publication in MNRAS Letter
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