546 research outputs found
Chandra HETGS Multiphase Spectroscopy Of The Young Magnetic O Star Theta(1) Orionis C
We report on four Chandra grating observations of the oblique magnetic rotator theta(1) Ori C (O5.5 V), covering a wide range of viewing angles with respect to the star\u27s 1060 G dipole magnetic field. We employ line-width and centroid analyses to study the dynamics of the X-ray - emitting plasma in the circumstellar environment, as well as line-ratio diagnostics to constrain the spatial location, and global spectral modeling to constrain the temperature distribution and abundances of the very hot plasma. We investigate these diagnostics as a function of viewing angle and analyze them in conjunction with new MHD simulations of the magnetically channeled wind shock mechanism on theta(1) Ori C. This model fits all the data surprisingly well, predicting the temperature, luminosity, and occultation of the X-ray - emitting plasma with rotation phase
The Large Magellanic Cloud: A power spectral analysis of Spitzer images
We present a power spectral analysis of Spitzer images of the Large
Magellanic Cloud. The power spectra of the FIR emission show two different
power laws. At larger scales (kpc) the slope is ~ -1.6, while at smaller ones
(tens to few hundreds of parsecs) the slope is steeper, with a value ~ -2.9.
The break occurs at a scale around 100-200 pc. We interpret this break as the
scale height of the dust disk of the LMC. We perform high resolution
simulations with and without stellar feedback. Our AMR hydrodynamic simulations
of model galaxies using the LMC mass and rotation curve, confirm that they have
similar two-component power-laws for projected density and that the break does
indeed occur at the disk thickness. Power spectral analysis of velocities
betrays a single power law for in-plane components. The vertical component of
the velocity shows a flat behavior for large structures and a power law similar
to the in-plane velocities at small scales. The motions are highly anisotropic
at large scales, with in-plane velocities being much more important than
vertical ones. In contrast, at small scales, the motions become more isotropic.Comment: 8 pages, 4 figures, talk presented at "Galaxies and their Masks",
celebrating Ken Freeman's 70-th birthday, Sossusvlei, Namibia, April 2010. To
be published by Springer, New York, editors D.L. Block, K.C. Freeman, & I.
Puerar
Caught in the Act: Strong, Active Ram Pressure Stripping in Virgo Cluster Spiral NGC 4330
We present a multi-wavelength study of NGC 4330, a highly-inclined spiral
galaxy in the Virgo Cluster which is a clear example of strong, ongoing ICM-ISM
ram pressure stripping. The HI has been removed from well within the
undisturbed old stellar disk, to 50% - 65% of R_25. Multi-wavelength data (WIYN
BVR and H-alpha, VLA 21-cm HI and radio continuum, and GALEX NUV and FUV)
reveal several one-sided extraplanar features likely caused by ram pressure at
an intermediate disk-wind angle. At the leading edge of the interaction, the
H-alpha and dust extinction curve sharply out of the disk in a remarkable and
distinctive "upturn" feature that may be generally useful as a diagnostic
indicator of active ram pressure. On the trailing side, the ISM is stretched
out in a long tail which contains 10% of the galaxy's total HI emission, 6 - 9%
of its NUV-FUV emission, but only 2% of the H-alpha. The centroid of the HI
tail is downwind of the UV/H-alpha tail, suggesting that the ICM wind has
shifted most of the ISM downwind over the course of the past 10 - 300 Myr.
Along the major axis, the disk is highly asymmetric in the UV, but more
symmetric in H-alpha and HI, also implying recent changes in the distributions
of gas and star formation. The UV-optical colors indicate very different star
formation histories for the leading and trailing sides of the galaxy. On the
leading side, a strong gradient in the UV-optical colors of the gas-stripped
disk suggests that it has taken 200-400 Myr to strip the gas from a radius of
>8 to 5 kpc, but on the trailing side there is no age gradient. All our data
suggest a scenario in which NGC 4330 is falling into cluster center for first
time and has experienced a significant increase in ram pressure over the last
200-400 Myr.Comment: AJ accepted; 22 pages, 25 figures, version with full-resolution
figures available at http://www.astro.yale.edu/abramso
Itch and skin rash from chocolate during fluoxetine and sertraline treatment: Case report
BACKGROUND: The skin contains a system for producing serotonin as well as serotonin receptors. Serotonin can also cause pruritus when injected into the skin. SSRI-drugs increase serotonin concentrations and are known to have pruritus and other dermal side effects. CASE PRESENTATION: A 46-year-old man consulted his doctor due to symptoms of depression. He did not suffer from any allergy but drinking red wine caused vasomotor rhinitis. Antidepressive treatment with fluoxetine 20 mg daily was initiated which was successful. After three weeks of treatment an itching rash appeared. An adverse drug reaction (ADR) induced by fluoxetine was suspected and fluoxetine treatment was discontinued. The symptoms disappeared with clemastine and betametasone treatment. Since the depressive symptoms returned sertraline medication was initiated. After approximately two weeks of sertraline treatment he noted an intense itching sensation in his scalp after eating a piece of chocolate cake. The itch spread to the arms, abdomen and legs and the patient treated himself with clemastine and the itch disappeared. He now realised that he had eaten a chocolate cake before this episode and remembered that before the first episode he had had a chocolate mousse dessert. He had never had any reaction from eating chocolate before and therefore reported this observation to his doctor. CONCLUSIONS: This case report suggests that there may be individuals that are very sensitive to increases in serotonin concentrations. Dermal side reactions to SSRI-drugs in these patients may be due to high activity in the serotonergic system at the dermal and epidermo-dermal junctional area rather than a hypersensitivity to the drug molecule itself
Ram pressure stripping of tilted galaxies
Ram pressure stripping of galaxies in clusters can yield gas deficient disks.
Previous numerical simulations based on various approaches suggested that,
except for near edge-on disk orientations, the amount of stripping depends very
little on the inclination angle. Following our previous study of face-on
stripping, we extend the set of parameters with the disk tilt angle and explore
in detail the effects of the ram pressure on the interstellar content (ISM) of
tilted galaxies that orbit in various environments of clusters, with compact or
extended distributions of the intra-cluster medium (ICM). We further study how
results of numerical simulations could be estimated analytically. A grid of
numerical simulations with varying parameters is produced using the tree/SPH
code GADGET with a modified method for calculating the ISM-ICM interaction.
These SPH calculations extend the set of existing results obtained from
different codes using various numerical techniques. The simulations confirm the
general trend of less stripping at orientations close to edge-on. The
dependence on the disk tilt angle is more pronounced for compact ICM
distributions, however it almost vanishes for strong ram pressure pulses.
Although various hydrodynamical effects are present in the ISM-ICM interaction,
the main quantitative stripping results appear to be roughly consistent with a
simple scenario of momentum transfer from the encountered ICM. This behavior
can also be found in previous simulations. To reproduce the numerical results
we propose a fitting formula depending on the disk tilt angle and on the column
density of the encountered ICM. Such a dependence is superior to that on the
peak ram pressure used in previous simple estimates
Ram pressure feeding super-massive black holes
When supermassive black holes at the center of galaxies accrete matter
(usually gas), they give rise to highly energetic phenomena named Active
Galactic Nuclei (AGN). A number of physical processes have been proposed to
account for the funneling of gas towards the galaxy centers to feed the AGN.
There are also several physical processes that can strip gas from a galaxy, and
one of them is ram pressure stripping in galaxy clusters due to the hot and
dense gas filling the space between galaxies. We report the discovery of a
strong connection between severe ram pressure stripping and the presence of AGN
activity. Searching in galaxy clusters at low redshift, we have selected the
most extreme examples of jellyfish galaxies, which are galaxies with long
tentacles of material extending for dozens of kpc beyond the galaxy disk. Using
the MUSE spectrograph on the ESO Very Large Telescope, we find that 6 out of
the 7 galaxies of this sample host a central AGN, and two of them also have
galactic-scale AGN ionization cones. The high incidence of AGN among the most
striking jellyfishes may be due to ram pressure causing gas to flow towards the
center and triggering the AGN activity, or to an enhancement of the stripping
caused by AGN energy injection, or both. Our analysis of the galaxy position
and velocity relative to the cluster strongly supports the first hypothesis,
and puts forward ram pressure as another, yet unforeseen, possible mechanism
for feeding the central supermassive black hole with gas.Comment: published in Nature, Vol.548, Number 7667, pag.30
X-Ray Emission Line Profile Modeling Of Hot Stars
The launch of high-spectral-resolution x-ray telescopes (Chandra, XMM) has provided a host of new spectralline diagnostics for the astrophysics community. In this paper we discuss Doppler-broadened emission line profiles from highly supersonic outflows of massive stars. These outflows, or winds, are driven by radiation pressure and carry a tremendous amount of kinetic energy, which can be converted to x rays by shock-heating even a small fraction of the wind plasma. The unshocked, cold wind is a source of continuum opacity to the x rays generated in the shock-heated portion of the wind. Thus the emergent line profiles are affected by transport through a two-component, moving, optically thick medium. While complicated, the interactions among these physical effects can provide quantitative information about the spatial distribution and velocity of the x-ray-emitting and absorbing plasma in stellar winds. We present quantitative models of both a spherically symmetric wind and a wind with hot plasma confined in an equatorial disk by a dipole magnetic field
Constraining the ages of the fireballs in the wake of the dIrr galaxy VCC1217 / IC3418
A complex of Halpha emitting blobs with strong FUV excess is associated to
the dIrr galaxy VCC1217 / IC3418 (Hester et al. 2010), and extends up to 17 Kpc
in the South-East direction. These outstanding features can be morphologically
divided into diffuse filaments and compact knots, where most of the star
formation activity traced by Halpha takes place. We investigate the properties
of the galaxy and the blobs using a multiwavelength approach in order to
constrain their origin. We collect publicly available data in UV and Halpha and
observe the scene in the optical U,g,r,i bands with LBT. The photometric data
allows to evaluate the star formation rate and to perform a SED fitting
separately of the galaxy and the blobs in order to constrain their stellar
population age. Moreover we analyze the color and luminosity profile of the
galaxy and its spectrum to investigate its recent interaction with the Virgo
cluster. Our analysis confirms that the most plausible mechanism for the
formation of the blobs is ram pressure stripping by the Virgo cluster IGM. The
galaxy colors, luminosity profile and SED are consistent with a sudden gas
depletion in the last few hundred Myr. The SED fitting of the blobs constrains
their ages in < 400 Myr.Comment: 10 pages, 11 figures, accepted for publication in Astronomy and
Astrophysic
Nicotine inhaler for smoking cessation [4]
To the Editor. In a recent article, Tonnesen et al suggest that a nicotine inhaler in smoking cessation could be implemented in general practitioner offices with high success rates and that it would be "acceptable" to patients. In addition, the program is described as "low intervention." Results from their study do not support such statements
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