3,333 research outputs found
A large scale extinction map of the Galactic Anticenter from 2MASS
We present a 127deg x 63deg extinction map of the Anticenter of the Galaxy,
based on and colour excess maps from 2MASS. This 8001 square degree
map with a resolution of 4 arcminutes is provided as online material. The
colour excess ratio / is used to determine the power law index of
the reddening law (\beta) for individual regions contained in the area (e.g.
Orion, Perseus, Taurus, Auriga, Monoceros, Camelopardalis, Cassiopeia). On
average we find a dominant value of \beta=1.8+-0.2 for the individual clouds,
in agreement with the canonical value for the interstellar medium. We also show
that there is an internal scatter of \beta values in these regions, and that in
some areas more than one dominant \beta value is present. This indicates large
scale variations in the dust properties. The analysis of the A_V values within
individual regions shows a change in the slope of the column density
distribution with distance. This can either be attributed to a change in the
governing physical processes in molecular clouds on spatial scales of about 1pc
or an A_V dilution with distance in our map.Comment: 18 pages, 29 Figures, 1 Table, Accepted for publication by MNRAS, A
version with higher resolution figures can be found at
http://astro.kent.ac.uk/~df
A detailed two-dimensional stellar population study of M32
We present Two-Dimensional Spectroscopy of the 9x12 arcsec^2 central region
of M32 obtained with the 2D_FIS fibre spectrograph installed at the William
Herschel Telescope. From these spectra line strength maps have been
reconstructed for about 20 absorption lines, mostly belonging to the Lick
system. We find good agreement with long-slit line strength profiles in the
literature. In contrast with previous studies, indices were azimuthally
averaged along continuum isophotes of M32. A remarkable result is that no
gradients are presented in the spectral indices. So, we have fitted the mean
values of each spectral index and central colours to the models of Vazdekis et
al. (1996) and Worthey (1994), finding that an intermediate age (~4 Gyr) and
metallicity similar to solar (Z=0.02) are the best fitted values for the
innermost region of M32.Comment: accepted in MNRA
Extinction techniques and impact on dust property determination
The near infrared extinction powerlaw index () and its uncertainty is
derived from three different techniques based on star counts, colour excess and
a combination of them. We have applied these methods to 2MASS data to determine
maps of and near infrared extinction of the small cloud IC 1396 W. The
combination of star counts and colour excess results in the most reliable
method to determine . It is found that the use of the correct
-map to transform colour excess values into extinction is fundamental
for column density profile analysis of clouds. We describe how artificial
photometric data, based on the model of stellar population synthesis of the
Galaxy (Robin et al. 2003), can be used to estimate uncertainties and derive
systematic effects of the extinction methods presented here. We find that all
colour excess based extinction determination methods are subject to small but
systematic offsets, which do not affect the star counting technique. These
offsets occur since stars seen through a cloud do not represent the same
population as stars in an extinction free control field.Comment: 10 pages, 9 figures, 1 table, accepted for publication in MNRA
Optimization of optical data transmitters for 40-Gb/s lightwave systems using frequency resolved optical gating
The measurement technique of frequency resolved optical gating has been used to optimize the phase of a 40-GHz train of optical pulses generated using a continuous-wave laser gated with an external modulator. This technique will be vital for optimization of optical transmitters to be used in systems operating at 40 Gb/s and beyond, as standard measurement techniques will not suffice to optimize such high-speed systems
Factores de riesgo relacionados con la salud sexual en los jóvenes europeos
En Europa, seguimos asistiendo a un aumento de la transmisión sexual del virus de la inmunodeficiencia humana (VIH) y otras infecciones de transmisión sexual (ITS).
Para priorizar estrategias de salud sexual, resulta importante identificar los factores sexuales de riesgo presentes en los jóvenes europeos.
Se realizó una revisión sistemática de artículos científicos y estudios de instituciones oficiales europeas. En total, fueron identificados 21 artículos y 10 estudios. Los datos sugieren un aumento de la
iniciación sexual juvenil y del número de parejas sexuales. El 15-20% de los jóvenes usan de forma inconstante el preservativo. Entre los conocimientos y actitudes de riesgo detectadas encontramos: desconocer otras ITS distintas al VIH, tener una actitud favorable a las relaciones sexuales casuales, creer erróneamente que algunas medidas son eficaces para prevenir el VIH, desconocer los riesgos de tener múltiples parejas sexuales y desconocer la transmisión sexual del VIH. Los datos subrayan la necesidad de mejorar los mensajes transmitidos a los jóvenes
Analysis of contents about sexuality and human reproduction in school textbooks in Spain
Objectives:
The spread of sexually transmitted infections (STI) in adolescents and teenage pregnancy rates are increasing. A decrease in the average age of youth’s first sexual experience is also being noted. Sexual education programs in schools have an important role to play in addressing these issues. The objective of this study is to analyze the content of textbooks in the area of sexuality and human reproduction in order to evaluate the extent to which these textbooks promote healthy reproductive life styles, as well as risk behavior avoidance among the adolescent students.
Study design:
Descriptive study of school textbooks content.
Methods:
The study sample consisted of 12 textbooks (about 80% of all the textbooks) used in Spanish secondary school and edited in 2002. A content analysis evaluated the extent to which these books demonstrated reliable scientific information about: a) condom effectiveness; b) consequences, prevention, and treatment of STI; c) family planning methods; d) Assisted reproductive technologies and e) the promotion of healthy reproductive lifestyles.
Results:
All textbooks presented inaccurate information in the areas studied. Two hundred and eighty one quotes were identified that facilitated an incomplete perception of sexuality or enabled risky behavior. An average of 12.6 incorrect messages was identified in each textbook.
Conclusions:
The textbooks examined are neither appropriate nor comprehensive enough for adolescent education on issues of sexuality. Results suggest a need for alternative textbooks based on better scientific evidence. It is essential that textbooks empower adolescents to make healthy decisions through the promotion of useful life skills that provide a more integrated concept of sexuality. In any case, there is a need for approaches to sexual education to integrate values commonly held by parents of the youth that use such texts
Search for radial velocity variations in eight M-dwarfs with NIRSPEC/Keck II
Context. Radial velocity (RV) measurements from near-infrared spectra have
become a potentially powerful tool to search for planets around cool stars and
sub-stellar objects. As part of a large survey to characterize M-dwarfs using
NIRSPEC at Keck II, we obtained spectra of eight late M-dwarfs (spectral types
M5.0-M8.0) during two or more observing epochs per target. These spectra were
taken with intermediate spectral resolving powers (R \sim 20,000) in the
J-band.
Aims. We search for relative radial velocity variability in these late
M-dwarfs and test the NIRSPEC capability of detecting short period brown dwarf
and massive planetary companions around low-mass stars in the J-band (\approx
1.25 micron). Additionally, we reanalyzed the data of the M8-type star vB10
(one of our targets) presented in Zapatero Osorio et al. (2009), which were
obtained with the same instrumentation as our data.
Methods. [...]
Results. For the entire M-dwarf sample, we do not find any evidence of
relative RV variations induced by a short period brown dwarf or massive
planetary companion. The typical RV precision of the measurements is between
180 and 300 m/s, which is sufficient to detect hot Neptunes around M-dwarfs.
Also, we find that the spurious RV shift in Zapatero et al. (2009) of the star
VB10 was caused by asymmetries in the instrumental profile between different
observing epochs, which were not taken into account in their analysis.Comment: A&A, 7 pages, 5 figure
J-band variability of M dwarfs in the WFCAM Transit Survey
We present an analysis of the photometric variability of M dwarfs in the Wide Field Camera (WFCAM) Transit Survey. Although periodic light-curve variability in low mass stars is generally dominated by photospheric star spot activity, M dwarf variability in the J band has not been as thoroughly investigated as at visible wavelengths. Spectral type estimates for a sample of over 200 000 objects are made using spectral type-colour relations, and over 9600 dwarfs (J 0.2 mag flaring event from an M4V star in our sample.Peer reviewe
Incidence of debris discs around FGK stars in the solar neighbourhood
Debris discs are a consequence of the planet formation process and constitute
the fingerprints of planetesimal systems. Their solar system's counterparts are
the asteroid and Edgeworth-Kuiper belts. The aim of this paper is to provide
robust numbers for the incidence of debris discs around FGK stars in the solar
neighbourhood. The full sample of 177 FGK stars with d<20 pc proposed for the
DUNES survey is presented. Herschel/PACS observations at 100 and 160 micron
complemented with data at 70 micron, and at 250, 350 and 500 micron SPIRE
photometry, were obtained. The 123 objects observed by the DUNES collaboration
were presented in a previous paper. The remaining 54 stars, shared with the
DEBRIS consortium and observed by them, and the combined full sample are
studied in this paper. The incidence of debris discs per spectral type is
analysed and put into context together with other parameters of the sample,
like metallicity, rotation and activity, and age.
The subsample of 105 stars with d<15 pc containing 23 F, 33 G and 49 K stars,
is complete for F stars, almost complete for G stars and contains a substantial
number of K stars to draw solid conclusions on objects of this spectral type.
The incidence rates of debris discs per spectral type 0.26 (6 objects with
excesses out of 23 F stars), 0.21 (7 out of 33 G stars) and 0.20 (10 out of 49
K stars), the fraction for all three spectral types together being 0.22 (23 out
of 105 stars). Uncertainties corresponding to a 95% confidence level are given
in the text for all these numbers. The medians of the upper limits of
L_dust/L_* for each spectral type are 7.8E-7 (F), 1.4E-6 (G) and 2.2E-6 (K);
the lowest values being around 4.0E-7. The incidence of debris discs is similar
for active (young) and inactive (old) stars. The fractional luminosity tends to
drop with increasing age, as expected from collisional erosion of the debris
belts.Comment: 31 pages, 15 figures, 10 tables, 2 appendice
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