899 research outputs found
Structural properties of disk galaxies I. The intrinsic ellipticity of bulges
(Abridged) A variety of formation scenarios was proposed to explain the
diversity of properties observed in bulges. Studying their intrinsic shape can
help in constraining the dominant mechanism at the epochs of their assembly.
The structural parameters of a magnitude-limited sample of 148 unbarred S0--Sb
galaxies were derived in order to study the correlations between bulges and
disks as well as the probability distribution function (PDF) of the intrinsic
equatorial ellipticity of bulges. It is presented a new fitting algorithm
(GASP2D) to perform the two-dimensional photometric decomposition of galaxy
surface-brightness distribution. This was assumed to be the sum of the
contribution of a bulge and disk component characterized by elliptical and
concentric isophotes with constant (but possibly different) ellipticity and
position angles. Bulge and disk parameters of the sample galaxies were derived
from the J-band images which were available in the Two Micron All Sky Survey.
The PDF of the equatorial ellipticity of the bulges was derived from the
distribution of the observed ellipticities of bulges and misalignments between
bulges and disks. Strong correlations between the bulge and disk parameters
were found. About 80% of bulges in unbarred lenticular and
early-to-intermediate spiral galaxies are not oblate but triaxial ellipsoids.
Their mean axial ratio in the equatorial plane is = 0.85. There is not
significant dependence of their PDF on morphology, light concentration, and
luminosity. The interplay between bulge and disk parameters favors scenarios in
which bulges assembled from mergers and/or grew over long times through disk
secular evolution. But all these mechanisms have to be tested against the
derived distribution of bulge intrinsic ellipticities.Comment: 24 pages, 13 figures, accepted for publication in A&A, corrected
proof
Inversion of stellar statistics equation for the Galactic Bulge
A method based on Lucy (1974, AJ 79, 745) iterative algorithm is developed to
invert the equation of stellar statistics for the Galactic bulge and is then
applied to the K-band star counts from the Two-Micron Galactic Survey in a
number of off-plane regions (10 deg.>|b|>2 deg., |l|<15 deg.).
The top end of the K-band luminosity function is derived and the morphology
of the stellar density function is fitted to triaxial ellipsoids, assuming a
non-variable luminosity function within the bulge. The results, which have
already been outlined by Lopez-Corredoira et al.(1997, MNRAS 292, L15), are
shown in this paper with a full explanation of the steps of the inversion: the
luminosity function shows a sharp decrease brighter than M_K=-8.0 mag when
compared with the disc population; the bulge fits triaxial ellipsoids with the
major axis in the Galactic plane at an angle with the line of sight to the
Galactic centre of 12 deg. in the first quadrant; the axial ratios are
1:0.54:0.33, and the distance of the Sun from the centre of the triaxial
ellipsoid is 7860 pc. The major-minor axial ratio of the ellipsoids is found
not to be constant. However, the interpretation of this is controversial. An
eccentricity of the true density-ellipsoid gradient and a population gradient
are two possible explanations.
The best fit for the stellar density, for 1300 pc<t<3000 pc, are calculated
for both cases, assuming an ellipsoidal distribution with constant axial
ratios, and when K_z is allowed to vary. From these, the total number of bulge
stars is ~ 3 10^{10} or ~ 4 10^{10}, respectively.Comment: 19 pages, 23 figures, accepted in MNRA
Astrophysical inputs on the SUSY dark matter annihilation detectability
If dark matter (DM), which is considered to constitute most of the mass of
galaxies, is made of supersymmetric (SUSY) particles, the centers of galaxies
should emit gamma-rays produced by their self-annihilation. We present accurate
estimates of continuum gamma-ray fluxes due to neutralino annihilation in the
central regions of the Milky Way. We use detailed models of our Galaxy, which
satisfy available observational data, and include some important physical
processes, which were previously neglected. Our models predict that spatially
extended annihilation signal should be detected at high confidence levels by
incoming experiments assuming that neutralinos make up most of the DM in the
Universe and that they annihilate according to current SUSY models.Comment: 4 pages, submitted to Physical Review Letter
Archives lacustres de l'évolution du climat et des activités humaines récentes dans les Pyrénées ariégeoises au cours de l'Holocène (étang majeur, vallée du Haut-Vicdessos, Pyrénées, France)
International audienceDans le cadre de l'Observatoire Hommes Milieux Haut-Vicdessos, des archives lacustres sont utilisées pour distin-guer les impacts de l'Homme ou du climat dans les Pyrénées (Ariège, 42°N). Associée à la cartographie acoustique de l'Étang Majeur, les analyses des sols et des sédi-ments lacustres mettent en évidence une sédimentation Tardiglaciaire riche en ti-tane, qui contraste avec une sédimentation Holocène de type dy résultant de l'érosion diffuse des tourbes présentes en amont du lac. L'enregistrement indique des périodes plus humides, datées en 1200, 1950, 3400 et 4550 cal BP et associées aux apports d'un canyon drainant les zones d'altitude. Depuis 1907, le niveau d'eau du lac est ré-gulé par deux barrages hydroélectriques. Il en résulte un marnage de 10 m affec-tant jusqu'à 37 % du bassin. Ceci a pour conséquences de remobiliser le matériel issu des berges, et d'augmenter la produc-tivité algaire et les taux d'accumulation
Riociguat treatment in patients with pulmonary arterial hypertension: Final safety data from the EXPERT registry
Objective
The soluble guanylate cyclase stimulator riociguat is approved for the treatment of adult patients with pulmonary arterial hypertension (PAH) and inoperable or persistent/recurrent chronic thromboembolic pulmonary hypertension following Phase 3 randomized trials. The EXPosurE Registry RiociguaT in patients with pulmonary hypertension (EXPERT) study was designed to monitor the long-term safety of riociguat in clinical practice.
Methods
EXPERT was an international, multicenter, prospective, uncontrolled, non-interventional cohort study of patients treated with riociguat. Patients were followed for at least 1 year and up to 4 years from enrollment or until 30 days after stopping riociguat treatment. Primary safety outcomes were adverse events (AEs) and serious adverse events (SAEs) coded using Medical Dictionary for Regulatory Activities preferred terms and System Organ Classes version 21.0, collected during routine clinic visits (usually every 3–6 months) and collated via case report forms.
Results
In total, 326 patients with PAH were included in the analysis. The most common AEs in these patients were dizziness (11.7%), right ventricular (RV)/cardiac failure (10.7%), edema/peripheral edema (10.7%), diarrhea (8.6%), dyspnea (8.0%), and cough (7.7%). The most common SAEs were RV/cardiac failure (10.1%), pneumonia (6.1%), dyspnea (4.0%), and syncope (3.4%). The exposure-adjusted rate of hemoptysis/pulmonary hemorrhage was 2.5 events per 100 patient-years.
Conclusion
Final data from EXPERT show that in patients with PAH, the safety of riociguat in clinical practice was consistent with clinical trials, with no new safety concerns identified and a lower exposure-adjusted rate of hemoptysis/pulmonary hemorrhage than in the long-term extension of the Phase 3 trial in PAH
Determining the Physical Properties of the B Stars I. Methodology and First Results
We describe a new approach to fitting the UV-to-optical spectra of B stars to
model atmospheres and present initial results. Using a sample of lightly
reddened stars, we demonstrate that the Kurucz model atmospheres can produce
excellent fits to either combined low dispersion IUE and optical photometry or
HST FOS spectrophotometry, as long as the following conditions are fulfilled:
1) an extended grid of Kurucz models is employed,
2) the IUE NEWSIPS data are placed on the FOS absolute flux system using the
Massa & Fitzpatrick (1999) transformation, and
3) all of the model parameters and the effects of interstellar extinction are
solved for simultaneously.
When these steps are taken, the temperatures, gravities, abundances and
microturbulence velocities of lightly reddened B0-A0 V stars are determined to
high precision. We also demonstrate that the same procedure can be used to fit
the energy distributions of stars which are reddened by any UV extinction curve
which can be expressed by the Fitzpatrick & Massa (1990) parameterization
scheme.
We present an initial set of results and verify our approach through
comparisons with angular diameter measurements and the parameters derived for
an eclipsing B star binary. We demonstrate that the metallicity derived from
the ATLAS 9 fits to main sequence B stars is essentially the Fe abundance. We
find that a near zero microturbulence velocity provides the best-fit to all but
the hottest or most luminous stars (where it may become a surrogate for
atmospheric expansion), and that the use of white dwarfs to calibrate UV
spectrophotometry is valid.Comment: 17 pages, including 2 pages of Tables and 6 pages of Figures.
Astrophysical Jounral, in pres
Riociguat treatment in patients with chronic thromboembolic pulmonary hypertension: Final safety data from the EXPERT registry
Objective: The soluble guanylate cyclase stimulator riociguat is approved for the treatment of adult patients with
pulmonary arterial hypertension (PAH) and inoperable or persistent/recurrent chronic thromboembolic pulmonary
hypertension (CTEPH) following Phase 3 randomized trials. The EXPosurE Registry RiociguaT in patients
with pulmonary hypertension (EXPERT) study was designed to monitor the long-term safety of riociguat in
clinical practice.
Methods: EXPERT was an international, multicenter, prospective, uncontrolled, non-interventional cohort study
of patients treated with riociguat. Patients were followed for at least 1 year and up to 4 years from enrollment or
until 30 days after stopping riociguat treatment. Primary safety outcomes were adverse events (AEs) and serious
adverse events (SAEs) coded using Medical Dictionary for Regulatory Activities preferred terms and System
Organ Classes version 21.0, collected during routine clinic visits and collated via case report forms.
Results: In total, 956 patients with CTEPH were included in the analysis. The most common AEs in these patients
were peripheral edema/edema (11.7%), dizziness (7.5%), right ventricular (RV)/cardiac failure (7.7%), and
pneumonia (5.0%). The most common SAEs were RV/cardiac failure (7.4%), pneumonia (4.1%), dyspnea
(3.6%), and syncope (2.5%). Exposure-adjusted rates of hemoptysis/pulmonary hemorrhage and hypotension
were low and comparable to those in the long-term extension study of riociguat (Chronic Thromboembolic
Pulmonary Hypertension Soluble Guanylate Cyclase–Stimulator Trial [CHEST-2]).
Conclusion: Data from EXPERT show that in patients with CTEPH, the safety of riociguat in routine practice was
consistent with the known safety profile of the drug, and no new safety concerns were identified
Pulmonary arterial hypertension: from the kingdom of the near-dead to multiple clinical trial meta-analyses
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