3,635 research outputs found
Spectral Characterization of a Prototype SFA Camera for Joint Visible and NIR Acquisition
International audienceMultispectral acquisition improves machine vision since it permits capturing more information on object surface properties than color imaging. The concept of spectral filter arrays has been developed recently and allows multispectral single shot acquisition with a compact camera design. Due to filter manufacturing difficulties, there was, up to recently, no system available for a large span of spectrum, i.e., visible and Near Infra-Red acquisition. This article presents the achievement of a prototype of camera that captures seven visible and one near infra-red bands on the same sensor chip. A calibration is proposed to characterize the sensor, and images are captured. Data are provided as supplementary material for further analysis and simulations. This opens a new range of applications in security, robotics, automotive and medical fields
Physical Investigation of the Potentially Hazardous Asteroid (144898) 2004 VD17
In this paper we present the observational campaign carried out at ESO NTT
and VLT in April and May 2006 to investigate the nature and the structure of
the Near Earth Object (144898) 2004 VD17. In spite of a great quantity of
dynamical information, according to which it will have a close approach with
the Earth in the next century, the physical properties of this asteroid are
largely unknown. We performed visible and near--infrared photometry and
spectroscopy, as well as polarimetric observations. Polarimetric and
spectroscopic data allowed us to classify 2004 VD17 as an E-type asteroid. A
good agreement was also found with the spectrum of the aubrite meteorite Mayo
Belwa. On the basis of the polarimetric albedo (p_v=0.45) and of photometric
data, we estimated a diameter of about 320 m and a rotational period of about 2
hours. The analysis of the results obtained by our complete survey have shown
that (144898) 2004 VD17 is a peculiar NEO, since it is close to the breakup
limits for fast rotator asteroids, as defined by Pravec and Harris (2000).
These results suggest that a more robust structure must be expected, as a
fractured monolith or a rubble pile in a "strength regime" (Holsapple 2002).Comment: 32 pages, 7 figure, paper accepted for publication in Icaru
SPHERE: the exoplanet imager for the Very Large Telescope
Observations of circumstellar environments to look for the direct signal of
exoplanets and the scattered light from disks has significant instrumental
implications. In the past 15 years, major developments in adaptive optics,
coronagraphy, optical manufacturing, wavefront sensing and data processing,
together with a consistent global system analysis have enabled a new generation
of high-contrast imagers and spectrographs on large ground-based telescopes
with much better performance. One of the most productive is the
Spectro-Polarimetic High contrast imager for Exoplanets REsearch (SPHERE)
designed and built for the ESO Very Large Telescope (VLT) in Chile. SPHERE
includes an extreme adaptive optics system, a highly stable common path
interface, several types of coronagraphs and three science instruments. Two of
them, the Integral Field Spectrograph (IFS) and the Infra-Red Dual-band Imager
and Spectrograph (IRDIS), are designed to efficiently cover the near-infrared
(NIR) range in a single observation for efficient young planet search. The
third one, ZIMPOL, is designed for visible (VIR) polarimetric observation to
look for the reflected light of exoplanets and the light scattered by debris
disks. This suite of three science instruments enables to study circumstellar
environments at unprecedented angular resolution both in the visible and the
near-infrared. In this work, we present the complete instrument and its on-sky
performance after 4 years of operations at the VLT.Comment: Final version accepted for publication in A&
Minimizing Strong Telluric Absorption in Near Infra-red Stellar Spectra
We have obtained high resolution spectra (R = 25000) of an A star over
varying airmass to determine the effectiveness of telluric removal in the limit
of high signal to noise. The near infra-red line HeI at 2.058 microns, which is
a sensitive indicator of physical conditions in massive stars, supergiants, HII
regions and YSOs, resides among pressure broadened telluric absorption from
carbon dioxide and water vapor that varies both in time and with observed
airmass.
Our study shows that in the limit of bright stars at high resolution,
accuracies of 5% are typical for high airmass observations (greater than 1.9),
improving to a photon-limited accuracy of 2% at smaller airmasses (less than
1.15). We find that by using the continuum between telluric absorption lines of
a ro-vibrational fan a photon-limited 1% accuracy is achievable.Comment: 14 pages, 7 figures. Accepted for publication in PAS
The Dark UNiverse Explorer (DUNE): Proposal to ESA's Cosmic Vision
The Dark UNiverse Explorer (DUNE) is a wide-field space imager whose primary
goal is the study of dark energy and dark matter with unprecedented precision.
For this purpose, DUNE is optimised for the measurement of weak gravitational
lensing but will also provide complementary measurements of baryonic accoustic
oscillations, cluster counts and the Integrated Sachs Wolfe effect. Immediate
auxiliary goals concern the evolution of galaxies, to be studied with
unequalled statistical power, the detailed structure of the Milky Way and
nearby galaxies, and the demographics of Earth-mass planets. DUNE is an
Medium-class mission which makes use of readily available components, heritage
from other missions, and synergy with ground based facilities to minimise cost
and risks. The payload consists of a 1.2m telescope with a combined visible/NIR
field-of-view of 1 deg^2. DUNE will carry out an all-sky survey, ranging from
550 to 1600nm, in one visible and three NIR bands which will form a unique
legacy for astronomy. DUNE will yield major advances in a broad range of fields
in astrophysics including fundamental cosmology, galaxy evolution, and
extrasolar planet search. DUNE was recently selected by ESA as one of the
mission concepts to be studied in its Cosmic Vision programme.Comment: Accepted in Experimental Astronom
Radio and IR study of the massive star-forming region IRAS 16353-4636
Context. With the latest infrared surveys, the number of massive protostellar
candidates has increased significantly. New studies have posed additional
questions on important issues about the formation, evolution, and other
phenomena related to them. Complementary to infrared data, radio observations
are a good tool to study the nature of these objects, and to diagnose the
formation stage. Aims. Here we study the far-infrared source IRAS 16353-4636
with the aim of understanding its nature and origin. In particular, we search
for young stellar objects (YSOs), possible outflow structure, and the presence
of non-thermal emission. Methods. Using high-resolution, multi-wavelength radio
continuum data obtained with the Australia Telescope Compact Array, we image
IRAS 16353-4636 and its environment from 1.4 to 19.6 GHz, and derive the
distribution of the spectral index at maximum angular resolution. We also
present new JHKs photometry and spectroscopy data obtained at ESO NTT. 13 CO
and archival HI line data, and infrared databases (MSX, GLIMPSE, MIPSGal) are
also inspected. Results. The radio continuum emission associated with IRAS
16353-4636 was found to be extended (~10 arcsec), with a bow-shaped morphology
above 4.8 GHz, and a strong peak persistent at all frequencies. The NIR
photometry led us to identify ten near-IR sources and classify them according
to their color. We used the HI line data to derive the source distance, and
analyzed the kinematical information from the CO and NIR lines detected.
Conclusions. We have identified the source IRAS 16353-4636 as a new
protostellar cluster. In this cluster we recognized three distinct sources: a
low-mass YSO, a high-mass YSOs, and a mildly confined region of intense and
non-thermal radio emission. We propose the latter corresponds to the terminal
part of an outflow.Comment: To appear in A&A. 10 pages, 8 figure
Unveiling the nature of IGR J16283-4838
Context. One of the most striking discoveries of the INTEGRAL observatory is
the existence of a previously unknown population of X-ray sources in the inner
arms of the Galaxy. The investigations of the optical/NIR counterparts of some
of them have provided evidence that they are highly absorbed high mass X-ray
binaries hosting supergiants. Aims. We aim to identify the optical/NIR
counterpart of one of the newly discovered INTEGRAL sources, IGR J16283-4838,
and determine the nature of this system. Methods. We present optical and NIR
observations of the field of IGR J16283-4838, and use the astrometry and
photometry of the sources within it to identify its counterpart. We obtain its
NIR spectrum, and its optical/NIR spectral energy distribution by means of
broadband photometry. We search for the intrinsic polarization of its light,
and its short and long-term photometric variability. Results. We demonstrate
that this source is a highly absorbed HMXB located beyond the Galactic center,
and that it may be surrounded by a variable circumstellar medium.Comment: 6 pages, 5 figures, accepted for publication in Astronomy &
Astrophysic
Extended mid-infrared emission from VV 114: probing the birth of a ULIRG
We present our 5-16 micron spectro-imaging observations of VV114, an infrared
luminous early-stage merger, taken with the ISOCAM camera on-board ISO. We find
that only 40% of the mid-infrared (MIR) flux is associated with a compact
nuclear region, while the rest of the emission originates from a rather diffuse
component extended over several kpc. This is in stark contrast with the very
compact MIR starbursts usually seen in luminous infrared galaxies. A secondary
peak of MIR emission is associated with an extra-nuclear star forming region
which displays the largest Halpha equivalent width in the whole system.
Comparing our data with the distribution of the molecular gas and cold dust, as
well as with radio observations, it becomes evident that the conversion of
molecular gas into stars can be triggered over large areas at the very first
stages of an interaction. The presence of a very strong continuum at 5 microns
in one of the sources indicates that an enshrouded active galactic nucleus may
contribute to 40% of its MIR flux. We finally note that the relative variations
in the UV to radio spectral properties between the merging galaxies provide
evidence that the extinction-corrected star formation rate of similar objects
at high z, such as those detected in optical deep surveys, can not be
accurately derived from their rest-frame UV properties.Comment: 14 pages, 5 figures, accepted for publication in A&
An AKARI Search for Intracluster Dust of Globular Clusters
We report the observations of 12 globular clusters with the AKARI/FIS. Our
goal is to search for emission from the cold dust within clusters. We detect
diffuse emissions toward NGC 6402 and 2808, but the IRAS 100-micron maps show
the presence of strong background radiation. They are likely emitted from the
galactic cirrus, while we cannot rule out the possible association of a bump of
emission with the cluster in the case of NGC 6402. We also detect 28 point-like
sources mainly in the WIDE-S images (90 micron). At least several of them are
not associated with the clusters but background galaxies based on some external
catalogs. We present the SEDs by combining the near-and-mid infrared data
obtained with the IRC if possible. The SEDs suggest that most of the point
sources are background galaxies. We find one candidate of the intracluster dust
which has no mid-infrared counterpart unlike the other point-like sources,
although some features such as its point-like appearance should be explained
before we conclude its intracluster origin. For most of the other clusters, we
have confirmed the lack of the intracluster dust. We evaluate upper limits of
the intracluster dust mass to be between 1.0E-05 and 1.0E-03 solar mass
depending on the dust temperature. The lifetime of the intracluster dust
inferred from the upper limits is shorter than 5 Myr (T=70K) or 50 Myr (35K).
Such short lifetime indicates some mechanism(s) are at work to remove the
intracluster dust. We also discuss its impact on the chemical evolution of
globular clusters.Comment: Accepted for publication in PASJ AKARI special issue. 14 pages, 11
figure
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