79 research outputs found
Observations of spatial and velocity structure in the Orion Molecular Cloud
Observations are reported of H2 IR emission in the S(1) v=1-0 line at 2.121
microns in the Orion Molecular Cloud, OMC1, using the GriF instrument on the
Canada-France-Hawaii Telescope. GriF is a combination of adaptive optics and
Fabry-Perot interferometry, yielding a spatial resolution of 0.15" to 0.18" and
a velocity discrimination as high as 1 km/s. Thanks to the high spatial and
velocity resolution of the GriF data, 193 bright H2 emission regions can be
identified in OMC1. The general characteristics of these features are described
in terms of radial velocities, brightness and spatial displacement of maxima of
velocity and brightness, the latter to yield the orientation of flows in the
plane of the sky. Strong spatial correlation between velocity and bright H2
emission is found and serves to identify many features as shocks. Important
results are: (i) velocities of the excited gas illustrate the presence of a
zone to the south of BN-IRc2 and Peak 1, and the west of Peak 2, where there is
a powerful blue-shifted outflow with an average velocity of -18 km/s. This is
shown to be the NIR counterpart of an outflow identified in the radio from
source I, a very young O-star. (ii) There is a band of weak velocity features
(<5 km/s) in Peak 1 which may share a common origin through an explosive event,
in the BN-IRc2 region, with the fast-moving fingers (or bullets) to the NW of
OMC1. (iii) A proportion of the flows are likely to represent sites of low mass
star formation and several regions show multiple outflows, probably indicative
of multiple star formation within OMC1. The high spatial and velocity
resolution of the GriF data show these and other features in more detail than
has previously been possible.Comment: 27 pages, 19 figures, submitted to A&A Version 2: Several additions,
including a section on protostellar candidates in OMC1, have been made based
on the referee's suggestions v3: corrected typograph
Reaching micro-arcsecond astrometry with long baseline optical interferometry; application to the GRAVITY instrument
A basic principle of long baseline interferometry is that an optical path
difference (OPD) directly translates into an astrometric measurement. In the
simplest case, the OPD is equal to the scalar product between the vector
linking the two telescopes and the normalized vector pointing toward the star.
However, a too simple interpretation of this scalar product leads to seemingly
conflicting results, called here "the baseline paradox". For micro-arcsecond
accuracy astrometry, we have to model in full the metrology measurement. It
involves a complex system subject to many optical effects: from pure baseline
errors to static, quasi-static and high order optical aberrations. The goal of
this paper is to present the strategy used by the "General Relativity Analysis
via VLT InTerferometrY" instrument (GRAVITY) to minimize the biases introduced
by these defects. It is possible to give an analytical formula on how the
baselines and tip-tilt errors affect the astrometric measurement. This formula
depends on the limit-points of three type of baselines: the wide-angle
baseline, the narrow-angle baseline, and the imaging baseline. We also,
numerically, include non-common path higher-order aberrations, whose amplitude
were measured during technical time at the Very Large Telescope Interferometer.
We end by simulating the influence of high-order common-path aberrations due to
atmospheric residuals calculated from a Monte-Carlo simulation tool for
Adaptive optics systems. The result of this work is an error budget of the
biases caused by the multiple optical imperfections, including optical
dispersion. We show that the beam stabilization through both focal and pupil
tracking is crucial to the GRAVITY system. Assuming the instrument pupil is
stabilized at a 4 cm level on M1, and a field tracking below 0.2, we
show that GRAVITY will be able to reach its objective of 10as accuracy.Comment: 14 pages. Accepted by A&
MULTIPASS: gestion des consentements pour accéder aux données des exploitations dans une chaîne de confiance afin de favoriser l'émergence de nouveaux services pour les agriculteurs
12th EFITA International Conference, Rhode island, GRC, 27-/06/2019 - 29/06/2019International audienceWith the emergence of digital technologies, farms become a relevant source of data to meet the challenges of multi-performance agriculture. Beyond the services provided, access to farmers' data depends on a clear understanding of their use, which must be done in a transparent way. Several codes of conduct at a national or international level push for a voluntary commitment to respect some good practices in the use of agricultural data. To provide a tool and answer farmer's questions on the control of their data and the transparency of the data processing, the partners of the MULTIPASS project, have imagined an interoperable ecosystem of farmer consents management, protecting farmers from no consented uses of their data.Farmers' expectations of such an ecosystem have been expressed during workshops. They want to better identify existing data flows, including actors, data processes, and data clusters. Based on the farmers' expectations, the MULTIPASS project stakeholders have proposed the architecture of an ecosystem integrating two consent management tools as "pilots". This ecosystem should take in charge the interoperability between each consent management tools or with future tools. This solution is based on a shared typology of data and data processes as well as on the specifications of the consent message content. All these elements should be easily accessible to meet the interoperability need of the ecosystem. It is also based on a router, which provides unified access to consent management tools (using API). In particular, it provides the farmer (beneficiary) with an exhaustive view of his/her consents (which can be distributed on several consent management systems), meeting farmers' expectations for transparency. It is also the point where a data provider can check whether the consent required to provide data exists, without needing to know which consent management system is concerned. In this project, the stakeholders want to demonstrate to agricultural professional organizations the benefits and feasibility of a consent management ecosystem. By strengthening the confidence of farmers to share data, the project will allow the emergence of new knowledge and new services
Unveiling the central parsec region of an AGN: the Circinus nucleus in the near infrared with the VLT
VLT J- to M\p-band adaptive optics observations of the Circinus Galaxy on
parsec scales resolve a central bright Ks-band source with a FWHM size of 1.9
0.6 pc. This source is only visible at wavelengths longward of 1.6 m
and coincides in position with the peak of the [Si VII]~2.48 m coronal
line emission. With respect to the peak of the central optical emission, the
source is shifted by 0.15\arcsec (2.8 pc) to the south-east. Indeed, it
defines the vertex of a fairly collimated beam which extends for 10 pc,
and which is seen in both continuum light shortward of 1.6 m and in
H line emission. The source also lies at the center of a 19 pc
size [Si VII] ionization {\it bicone}.
Identifying this source as the nucleus of Circinus, its size is compatible
with a putative parsec-scale torus. Its spectral energy distribution,
characterized by a prominent narrow peak, is compatible with a dust temperature
of 300 K. Hotter dust within a 1 pc radius of the center is not detected. The
AGN luminosity required to heat this dust is in the range of X-ray luminosities
that have been measured toward the central source. This in turn supports the
existence of highly obscuring material, with column densities of
cm, that must be located within 1 pc of the core.Comment: 15 pages, 4 figures; To appear in The Astrophysical Journa
GRAVITY: getting to the event horizon of Sgr A*
We present the second-generation VLTI instrument GRAVITY, which currently is
in the preliminary design phase. GRAVITY is specifically designed to observe
highly relativistic motions of matter close to the event horizon of Sgr A*, the
massive black hole at center of the Milky Way. We have identified the key
design features needed to achieve this goal and present the resulting
instrument concept. It includes an integrated optics, 4-telescope, dual feed
beam combiner operated in a cryogenic vessel; near infrared wavefront sensing
adaptive optics; fringe tracking on secondary sources within the field of view
of the VLTI and a novel metrology concept. Simulations show that the planned
design matches the scientific needs; in particular that 10 microarcsecond
astrometry is feasible for a source with a magnitude of K=15 like Sgr A*, given
the availability of suitable phase reference sources.Comment: 13 pages, 11 figures, to appear in the conference proceedings of SPIE
Astronomical Instrumentation, 23-28 June 2008, Marseille, Franc
Near-infrared proper motions and spectroscopy of infrared excess sources at the Galactic Center
There are a number of faint compact infrared excess sources in the central
stellar cluster of the Milky Way. Their nature and origin is unclear. In
addition to several isolated objects of this kind we find a small but dense
cluster of co-moving sources (IRS13N) about 3" west of SgrA* just 0.5" north of
the bright IRS13E cluster of WR and O-type stars. Based on their color and
brightness, there are two main possibilities: (1) they may be dust embedded
stars older than few Myr, or (2) extremely young, dusty stars with ages less
than 1Myr. We present fist H- and Ks-band identifications or proper motions of
the IRS13N members, the high velocity dusty S-cluster object (DSO), and other
infrared excess sources in the central field. We also present results of NIR H-
and Ks-band ESO-SINFONI integral field spectroscopy of ISR13N. We show that
within the uncertainties, the proper motions of the IRS13N sources in Ks- and
L'-band are identical. This indicates that the bright L'-band IRS13N sources
are indeed dust enshrouded stars rather than core-less dust clouds. The proper
motions show that the IRS13N sources are not strongly gravitationally bound to
each other implying that they have been formed recently. We also present a
first H- and Ks-band identification as well as proper motions and HKsL'-colors
of a fast moving DSO which was recently found in the cluster of high speed
S-stars that surround the super-massive black hole Sagittarius A* (SgrA*). Most
of the compact L'-band excess emission sources have a compact H- or Ks-band
counterpart and therefore are likely stars with dust shells or disks. Our new
results and orbital analysis from our previous work favor the hypothesis that
the infrared excess IRS13N members and other dusty sources close to SgrA* are
very young dusty stars and that star formation at the GC is a continuously
ongoing process.Comment: 20 pages, 18 figures, 4 tables plus appendix with 16 figures and 3
tables accepted by A&
Future mmVLBI Research with ALMA: a European vision
Very long baseline interferometry at millimetre/submillimetre wavelengths (mmVLBI) offers the highest achievable spatial resolution at any wavelength in astronomy. The anticipated inclusion of ALMA as a phased array into a global VLBI network will bring unprecedented sensitivity and a transformational leap in capabilities for mmVLBI. Building on years of pioneering efforts in the US and Europe the ongoing ALMA Phasing Project (APP), a US-led international collaboration with MPIfR-led European contributions, is expected to deliver a beamformer and VLBI capability to ALMA by the end of 2014 (APP: Fish et al. 2013, arXiv:1309.3519). This report focuses on the future use of mmVLBI by the international users community from a European viewpoint. Firstly, it highlights the intense science interest in Europe in future mmVLBI observations as compiled from the responses to a general call to the European community for future research projects. A wide range of research is presented that includes, amongst others: - Imaging the event horizon of the black hole at the centre of the Galaxy - Testing the theory of General Relativity an/or searching for alternative theories - Studying the origin of AGN jets and jet formation - Cosmological evolution of galaxies and BHs, AGN feedback - Masers in the Milky Way (in stars and star-forming regions) - Extragalactic emission lines and astro-chemistry - Redshifted absorption lines in distant galaxies and study of the ISM and circumnuclear gas - Pulsars, neutron stars, X-ray binaries - Testing cosmology - Testing fundamental physical constant
Commentary on the article “Postpartum women’s use of medicines and breastfeeding practices: a systematic review”
Inward Bound: Studying the Galactic Centre with NAOS/CONICA
We report on the first results obtained using adaptive optics measurements of
the Galactic Centre done with NAOS/CONICA.Comment: 19 pages, 7 figure
Compact mid-IR sources east of galactic center source IRS5
There are four less prominent compact sources east of IRS5, the natures of
which were unclear until now. We present near-infrared K-band long slit
spectroscopy of the four sources east of IRS5 obtained with the ISAAC
spectrograph at the ESO VLT in July 2005. We interpret the data in combination
with high angular resolution NIR and MIR images obtained with ISAAC and NACO at
the ESO VLT.Comment: 9 pages, 8 figures. accepted by A&
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