1,270 research outputs found
Molecule mapping of HR8799b using OSIRIS on Keck: Strong detection of water and carbon monoxide, but no methane
Context. In 2015, Barman et al. (ApJ, 804, 61) presented detections of
absorption from water, carbon monoxide, and methane in the atmosphere of the
directly imaged exoplanet HR8799b using integral field spectroscopy (IFS) with
OSIRIS on the Keck II telescope. We recently devised a new method to analyse
IFU data, called molecule mapping, searching for high-frequency signatures of
particular molecules in an IFU data cube.
Aims. The aim of this paper is to use the molecule mapping technique to
search for the previously detected spectral signatures in HR8799b using the
same data, allowing a comparison of molecule mapping with previous methods.
Methods. The medium-resolution H- and K-band pipeline-reduced archival data
were retrieved from the Keck archive facility. Telluric and stellar lines were
removed from each spectrum in the data cube, after which the residuals were
cross-correlated with model spectra of carbon monoxide, water, and methane.
Results. Both carbon monoxide and water are clearly detected at high
signal-to-noise, however, methane is not retrieved.
Conclusions. Molecule mapping works very well on the OSIRIS data of exoplanet
HR8799b. However, it is not evident why methane is detected in the original
analysis, but not with the molecule mapping technique. Possible causes could be
the presence of telluric residuals, different spectral filtering techniques, or
the use of different methane models. We do note that in the original analysis
methane was only detected in the K-band, while the H-band methane signal could
be expected to be comparably strong. More sensitive observations with the JWST
will be capable of confirming or disproving the presence of methane in this
planet at high confidence.Comment: 5 pages, 5 figures and 2 tables, accepted by A&
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Origins of the cytolytic synapse.
Cytotoxic T lymphocytes (CTLs) kill virus-infected and tumour cells with remarkable specificity. Upon recognition, CTLs form a cytolytic immune synapse with their target cell, and marked reorganization of both the actin and the microtubule cytoskeletons brings the centrosome up to the plasma membrane to the point of T cell receptor signalling. Secretory granules move towards the centrosome and are delivered to this focal point of secretion. Such centrosomal docking at the plasma membrane also occurs during ciliogenesis; indeed, striking similarities exist between the cytolytic synapse and the primary cilium that throw light on the possible origins of immune synapses.GMG is funded by Wellcome Trust Principal Research Fellowship [103930], MDR is now funded by a Sir Henry Dale Fellowship jointly funded by the Wellcome Trust and the Royal Society [107609].This is the author accepted manuscript. It is currently under an indefinite embargo pending publication by Nature Publishing Group
SAGE: A tool to constrain impacts of stellar activity on transmission spectroscopy
Transmission spectroscopy is a proven technique to study a transiting
exoplanet's atmosphere. However, stellar surface inhomogeneities, spots and
faculae, alter the observed transmission spectra: the stellar contamination
effect. The variable nature of the stellar activity also makes it difficult to
stitch together multi-epoch observations and evaluate any potential variability
in the exoplanet's atmosphere. This paper introduces SAGE, a tool to correct
for the time-dependent impact of stellar activity on transmission spectra. It
uses a pixelation approach to model the stellar surface with spots and faculae,
while fully accounting for limb-darkening and rotational line-broadening. The
current version is designed for low to medium-resolution spectra. We used SAGE
to evaluate stellar contamination for F to M-type hosts, testing various spot
sizes and locations, and quantify the impact of limb-darkening. We find that
limb-darkening enhances the importance of the spot location on the stellar
disk, with spots close to the disk center impacting the transmission spectra
more strongly than spots near the limb. Moreover, due to the chromaticity of
limb darkening, the shape of the contamination spectrum is also altered.
Additionally, SAGE can be used to retrieve the properties and distribution of
active regions on the stellar surface from photometric monitoring. We
demonstrate this for WASP-69 using TESS data, finding that two spots at
mid-latitudes and a combined coverage fraction of 1% are favoured. SAGE
allows us to connect the photometric variability to the stellar contamination
of transmission spectra, enhancing our ability to jointly interpret
transmission spectra obtained at different epochs.Comment: Accepted for publication in A&
El dispositivo habitable
This paper explains the main concepts supporting the project "Habitar el Dispositivo" which was awarded a prize in the International Competition "25 Bioclimatical Houses" promoted by the "Instituto Tecnológico de Energías Renovables of Tenerife " and organized by the "Colegio de Arquitectos de Canarias" and sponsored by the "International Union of Architects". As opposed to bioclimatical houses which are the result of adding bioclimatical devices to an architectural project, the integration of bioclimatical and architectural concepts in a livable device is proposed. A digital model of the project was built to analyze sunlight and shadow behavior and computer simulations permitted to determine thermal performance. Average thermal satisfaction was 89.75 % during typical summer and winter 24 hour periods.Se presentan los conceptos fundamentales que respaldan la propuesta "Habitar el Dispositivo", premiada en el Concurso Internacional "25 Viviendas Bioclimáticas" promovido por el "Instituto Tecnológico de Energías Renovables del Cabildo de Tenerife", organizado por el "Colegio de Arquitectos de Canarias" y homologado por la "Unión Internacional de Arquitectos". Al contrario de la solución de añadir dispositivos a un proyecto de arquitectura, la propuesta integra conceptos bioclimáticos y arquitectónicos en un dispositivo habitable. Un modelo digital de la edificación permitió estudiar su volumetría y soleamiento en diferentes períodos del año, mientras que su comportamiento térmico se analizó con un programa de simulación en régimen dinámico. El promedio de personas satisfechas en días típicos de verano e invierno fue del 89,75 %
Why every observatory needs a disco ball
Commercial disco balls provide a safe, effective and instructive way of
observing the Sun. We explore the optics of solar projections with disco balls,
and find that while sunspot observations are challenging, the solar disk and
its changes during eclipses are easy and fun to observe. We explore the disco
ball's potential for observing the moon and other bright astronomical
phenomena.Comment: 6 pages, 7 figures. Submitted to Physics Education. Comments welcom
The morphologies and masses of extremely red galaxies in the Groth Strip survey
We present a new cataloge of EROs from the Groth strip and study the relation
between their morphology and mass. We find 102 EROs (F814W-K=>4, K<=21.0), over
a survey area of 155 arcmin^2. The photometric data include U,B,F606W,F814W,J,K
bands. Morphologies are based on a by eye classification and we distinguish
between 3 basic classes: compact objects, targets with a disc and/or a bulge
component and irregular or merger candidates. The majority of our targets has
either a very compact morphology (33+-6%), or show more or less distinct disc
components (41+-6%). 14+-4% are merger or irregulars and 7 objects could not be
classified. We also study the dependence of structural parameters on
morphological appearance. EROs that are either compact or show a distinct bulge
component have smaller median effective radii (1.22+-0.14 kpc and 3.31+-0.53
kpc) than disc dominated (5.50+-0.51 kpc) or possible irregular galaxies or
merger candidates (4.92+-0.14 kpc). The Sersic index changes from 2.30+-0.34
and 3.24+-0.55, to 1.03+-0.24 and 1.54+-0.40 respectively.
Most the EROs in our sample have redshifts between z=1 and z=2; however,
compact EROs in our sample are found at redshifts as low as z=0.4 and as high
as z=2.8; the latter qualify as well as DRGs. Disc-like EROs are also found up
to z=2.8; however those with a bulge-disc structure are only seen at z<1.5. For
each of these EROs we determined the stellar mass and mean population age by
fitting synthetic Bruzual (2007) spectra to the SED. Mass estimates were
obtained by assuming an exponentially declining star formation rate. Total
stellar masses are in the range 9.1<log(M/M_sun)<11.6. We cannot detect
significant differences between the stellar mass distribution of the
morphological classes. EROs with masses of log(M/M_sun)>11.0 dominantly show
compact morphologies, but also include a significant number of sources with a
disc morphology.Comment: 21 pages, 17 figures, accepted for publication in MNRA
Cerramientos bioclimáticos para climas cálidos húmedos: la cuarta vivienda
In intertropical latitudes such as Venezuela with hot humid climates, building envelopes must reduce influence of solar radiation, and in these, roofs and windows must receive special attention.
Venezuela is also the country with the highest energy consumption per capita in Iberoamérica, much of which is generated by air conditioning systems in residential buildings, and Maracaibo and the surrounding lake basin have some of the highest temperature and humidity values in Venezuela, which increase energy consumption even more.
A bioclimatical house for this climate is proposed. This building incorporates principles from traditional indigenous, colonial and oil company houses in the Maracaibo lake basin to generate a new prototype, called the Fourth House.En climas cálidos húmedos como es el caso de grandes regiones de Venezuela, las envolventes deben reducir la influencia de la radiación solar y, por lo tanto, deben recibir atención especial.
Venezuela es también el país con más alto consumo energético per capita en Iberoamérica, generado en su mayor parte por el uso de sistemas de aire acondicionado en las edificaciones residenciales. En Maracaibo y en los alrededores del Lago de Maracaibo se registran los valores más altos de temperatura y humedad en Venezuela, lo que incrementa, aún más, el consumo energético de las viviendas de estas regiones.
La minimización del impacto de la radiación solar para lograr la reducción del consumo energético con un mayor bienestar térmico ha sido precisamente uno de los objetivos perseguidos con el desarrollo de una nueva vivienda bioclimática para la región del lago de Maracaibo. Esta incorpora principios de las tres viviendas bioclimáticas previas existentes en esa región: el palafito o vivienda tradicional indígena, la vivienda colonial republicana y la vivienda petrolera. Es por ello que esta vivienda ha sido llamada la Cuarta Vivienda
Telomere lengths in human oocytes, cleavage stage embryos and blastocysts
Telomeres are repeated sequences that protect the ends of chromosomes and harbour DNA-repair proteins. Telomeres shorten during each cell division in the absence of telomerase. When telomere length becomes critically short, cell senescence occurs. Telomere length therefore reflects both cellular ageing and capacity for division. We have measured telomere length in human germinal vesicle (GV) oocytes and pre-implantation embryos, by quantitative fluorescence in-situ hybridisation (Q-FISH), providing baseline data towards our hypothesis that telomere length is a marker of embryo quality. The numbers of fluorescent foci suggest that extensive clustering of telomeres occurs in mature GV stage oocytes, and in pre-implantation embryos. When calculating average telomere length by assuming that each signal presents one telomere, the calculated telomere length decreased from the oocyte to the cleavage stages, and increased between the cleavage stages and the blastocyst (11.12 vs 8.43 vs 12.22kb respectively, p<0.001). Other methods of calculation, based upon expected maximum and minimum numbers of telomeres, confirm that telomere length in blastocysts is significantly longer than cleavage stages. Individual blastomeres within an embryo showed substantial variation in calculated average telomere length. This study implies that telomere length changes according to the stage of pre-implantation embryo development
Spectroscopic bulge-disc decomposition: a new method to study the evolution of lenticular galaxies
A new method for spectroscopic bulge-disc decomposition is presented, in
which the spatial light profile in a two-dimensional spectrum is decomposed
wavelength-by-wavelength into bulge and disc components, allowing separate
one-dimensional spectra for each component to be constructed. This method has
been applied to observations of a sample of nine S0s in the Fornax Cluster in
order to obtain clean high-quality spectra of their individual bulge and disc
components. So far this decomposition has only been fully successful when
applied to galaxies with clean light profiles, consequently limiting the number
of galaxies that could be separated into bulge and disc components. Lick index
stellar population analysis of the component spectra reveals that in those
galaxies where the bulge and disc could be distinguished, the bulges have
systematically higher metallicities and younger stellar populations than the
discs. This correlation is consistent with a picture in which S0 formation
comprises the shutting down of star formation in the disc accompanied by a
final burst of star formation in the bulge. The variation in spatial-fit
parameters with wavelength also allows us to measure approximate colour
gradients in the individual components. Such gradients were detected separately
in both bulges and discs, in the sense that redder light is systematically more
centrally concentrated in all components. However, a search for radial
variations in the absorption line strengths determined for the individual
components revealed that they are absent from the vast majority of S0 discs and
bulges. The absence of gradients in line indices for most galaxies implies that
the colour gradient cannot be attributed to age or metallicity variations, and
is therefore most likely associated with varying degrees of obscuration by
dust.Comment: 10 pages, 10 figures, 1 table, accepted for publication in MNRA
New constraints on the HR 8799 planetary system from mid-infrared direct imaging
Direct imaging is a tried and tested method of detecting exoplanets in the near-infrared (IR), but has so far not been extended to longer wavelengths. New data at mid-IR wavelengths (8-20 μm) can provide additional constraints on planetary atmospheric models. We use the VLT Imager and Spectrometer for the mid-IR (VISIR) instrument on the VLT to detect or set stringent limits on the 8.7 μm flux of the four planets surrounding HR 8799, and to search for additional companions. We use a novel circularized point spread function subtraction technique to reduce the stellar signal and obtain instrument limited background levels and obtain optimal flux limits. The BT SETTL isochrones are then used to determine the resulting mass limits. We find flux limits between 0.7 and 3.3 mJy for the J8.9 flux of the different planets at better than 5σ level and derive a new mass limit of 30 MJup for any objects beyond 40 au. While this work has not detected planets in the HR 8799 system at 8.7 μm, it has found that an instrument with the sensitivity of VISIR is sufficient to detect at least four known hot planets around close stars, including β Pictoris b (1700 K, 19 pc), with more than 5σ certainty in 10 h of observing time in the mid-IR
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