12,706 research outputs found
Uncertainties in gas kinematics arising from stellar continuum modelling in integral field spectroscopy data: the case of NGC2906 observed with MUSE/VLT
We study how the use of several stellar subtraction methods and line fitting
approaches can affect the derivation of the main kinematic parameters (velocity
and velocity dispersion fields) of the ionized gas component. The target of
this work is the nearby galaxy NGC 2906, observed with the MUSE instrument at
Very Large Telescope. A sample of twelve spectra is selected from the inner
(nucleus) and outer (spiral arms) regions, characterized by different
ionization mechanisms. We compare three different methods to subtract the
stellar continuum (FIT3D, STARLIGHT and pPXF), combined with one of the
following stellar libraries: MILES, STELIB and GRANADA+MILES. The choice of the
stellar subtraction method is the most important ingredient affecting the
derivation of the gas kinematics, followed by the choice of the stellar library
and by the line fitting approach. In our data, typical uncertainties in the
observed wavelength and width of the H\alpha and [NII] lines are of the order
of _rms \sim 0.1\AA\ and _rms \sim 0.2\AA\ (\sim 5
and 10km/s, respectively). The results obtained from the [NII] line seem to be
slightly more robust, as it is less affected by stellar absorption than
H\alpha. All methods considered yield statistically consistent measurements
once a mean systemic contribution
\Delta\bar\lambda=\Delta\bar\sigma=0.2xDelta_{MUSE} is added in quadrature to
the line fitting errors, where \Delta_{MUSE} = 1.1\AA\ \sim 50 km/s denotes the
instrumental resolution of the MUSE spectra. Although the subtraction of the
stellar continuum is critical in order to recover line fluxes, any method
(including none) can be used in order to measure the gas kinematics, as long as
an additional component of 0.2 x Delta_MUSE is added to the error budget.Comment: 20 pages, 14 figure
PPAK Wide-field Integral Field Spectroscopy of NGC 628: I. The largest spectroscopic mosaic on a single galaxy
We present a wide-field IFS survey on the nearby face-on Sbc galaxy NGC 628,
comprising 11094 individual spectra, covering a nearly circular field-of-view
of ~6 arcmin in diameter, with a sampling of ~2.7 arcsec per spectrum in the
optical wavelength range (3700--7000 AA). This galaxy is part of the PPAK IFS
Nearby Galaxies Survey, (PINGS, Rosales-Ortega et al. 2009). To our knowledge,
this is the widest spectroscopic survey ever made in a single nearby galaxy. A
detailed flux calibration was applied, granting a spectrophotometric accuracy
of \,0.2 mag.
The age of the stellar populations shows a negative gradient from the inner
(older) to the outer (younger) regions. We found an inversion of this gradient
in the central ~1 kpc region, where a somewhat younger stellar population is
present within a ring at this radius. This structure is associated with a
circumnuclear star-forming region at ~ 500 pc, also found in similar spiral
galaxies. From the study of the integrated and spatially resolved ionized gas
we found a moderate SFR of ~ 2.4 Msun yr. The oxygen abundance shows a a
clear gradient of higher metallicity values from the inner part to the outer
part of the galaxy, with a mean value of 12~+~log(O/H) ~ 8.7. At some specific
regions of the galaxy, the spatially resolved distribution of the physical
properties show some level of structure, suggesting real point-to-point
variations within an individual \hh region. Our results are consistent with an
inside-out growth scheme, with stronger star formation at the outer regions,
and with evolved stellar populations in the inner ones.Comment: 31 pages, 22 Figuras, Accepted for Publishing in MNRAS (corrected
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High spatial resolution and high contrast optical speckle imaging with FASTCAM at the ORM
In this paper, we present an original observational approach, which combines,
for the first time, traditional speckle imaging with image post-processing to
obtain in the optical domain diffraction-limited images with high contrast
(1e-5) within 0.5 to 2 arcseconds around a bright star. The post-processing
step is based on wavelet filtering an has analogy with edge enhancement and
high-pass filtering. Our I-band on-sky results with the 2.5-m Nordic Telescope
(NOT) and the lucky imaging instrument FASTCAM show that we are able to detect
L-type brown dwarf companions around a solar-type star with a contrast DI~12 at
2" and with no use of any coronographic capability, which greatly simplifies
the instrumental and hardware approach. This object has been detected from the
ground in J and H bands so far only with AO-assisted 8-10 m class telescopes
(Gemini, Keck), although more recently detected with small-class telescopes in
the K band. Discussing the advantage and disadvantage of the optical regime for
the detection of faint intrinsic fluxes close to bright stars, we develop some
perspectives for other fields, including the study of dense cores in globular
clusters. To the best of our knowledge this is the first time that high
contrast considerations are included in optical speckle imaging approach.Comment: Proceedings of SPIE conference - Ground-based and Airborne
Instrumentation for Astronomy III (Conference 7735), San Diego 201
Discovery of a wide companion near the deuterium burning mass limit in the Upper Scorpius association
We present the discovery of a companion near the deuterium burning mass limit
located at a very wide distance, at an angular separation of 4.6+/-0.1 arcsec
(projected distance of ~ 670 AU) from UScoCTIO108, a brown dwarf of the very
young Upper Scorpius association. Optical and near-infrared photometry and
spectroscopy confirm the cool nature of both objects, with spectral types of M7
and M9.5, respectively, and that they are bona fide members of the association,
showing low gravity and features of youth. Their masses, estimated from the
comparison of their bolometric luminosities and theoretical models for the age
range of the association, are 60+/-20 and 14^{+2}_{-8} MJup, respectively. The
existence of this object around a brown dwarf at this wide orbit suggests that
the companion is unlikely to have formed in a disk based on current planet
formation models. Because this system is rather weakly bound, they did not
probably form through dynamical ejection of stellar embryos.Comment: 10 pages, including 4 figures and 2 table
On Brane Inflation Potentials and Black Hole Attractors
We propose a new potential in brane inflation theory, which is given by the
arctangent of the square of the scalar field. Then we perform an explicit
computation for inflationary quantities. This potential has many nice features.
In the small field approximation, it reproduces the chaotic and MSSM
potentials. It allows one, in the large field approximation, to implement the
attractor mechanism for bulk black holes where the geometry on the brane is de
Sitter. In particular, we show, up to some assumptions, that the Friedman
equation can be reinterpreted as a Schwarzschild black hole attractor equation
for its mass parameter.Comment: 12 pages. Reference updated and minor changes added. Version to
appear in Int. J. Mod. Phys.
Development of atopy and asthma: candidate environmental influences and important periods of exposure.
Atopy is a major risk factor for the development of asthma. Immune processes that lead to the development of antigen-specific IgE are essential to the development of atopy. This review examines the immune processes that are candidate targets for modulation by environmental agents; environmental and lifestyle factors that have been suggested as modulators of the development of atopy; and the impact of known environmental agents on atopic processes in the airway. The most important periods of immune development with regard to expression of atopy are likely during gestation and early childhood. A better understanding of which environmental agents are important, as well as the period of life during which these agents may exert an important effect, is essential to devising rational environmental avoidance strategies for at-risk populations
Directional and Polarized Lasing Action on Pb-free FASnI3 Integrated in Flexible Optical Waveguide
In this work, high-quality FASnI3 (FA, formamidinium) lead-free perovskite thin films are successfully incorporated in a flexible polyethylene terephthalate (PET) substrate to demonstrate amplified spontaneous emission (ASE) and lasing. The waveguide (WG) consists of polymethylmethacrylate(PMMA)/FASnI3 bilayer deposited on a PET substrate and is properly designed to allow single-mode propagation at the photoluminescence wavelength. This geometry optimizes the excitation of the emitting FASnI3, enhances the light−matter interaction in the semiconductor thin film, provides a preferable direction for the emitted light and allows its direct outcoupling for on-chip or fiber-optic applications. As far as the authors know, ASE and random lasing are obtained for the first time in a flexible-based WG integrating a highly efficient lead-free perovskite. The high quality of the deposited films and the optimized design of the structure result in an extremely low ASE/lasing threshold in the range of 1 µJ cm−2, which is only ten times higher than that measured in the same PMMA/FASnI3 structure deposited on a rigid substrate (Si/SiO2). More interestingly, these WGs exhibit a strong polarization anisotropy for the outcoupled ASE/lasing light with a preferable transverse electric polarization. This work is the base for the future development of ecofriendly, flexible, and efficient photonic devices.This project received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 862656 (project DROP-IT) and the European Research Council (ERC) via Consolidator Grant (724424, No-LIMIT) and by the Spanish MINECO through projects no. PID2020-120484RB-I00 and PID2019-107314RB-I00 (Stable)
SÃndrome de fatiga crónica en una adolescente de 15 años
Fatigue and lack of energy are frequent symptoms in children and adolescents. A
diagnosis of chronic fatigue syndrome should be considered in children and
adolescents who complain of chronic fatigue associated with other symptoms
without a demonstrable physical cause. Lack of knowledge about this syndrome and
late diagnosis may have a negative impact on the normal development of affected
children and adolescents. Treatment should be based on a rehabilitation program
with cognitive behavioral therapy and a gradual increase in activities
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