Search

The ALADDIN project aims at detecting warm dust populations around nearby main sequence stars. In order to achieve the significantly improved sensitivity with respect to existing instruments, the architecture of the system is focused and optimised for the mission: ALADDIN implements the nulling interferometry technique at the focal plane of a 2-telescope interferometer mounted on a rotating structural beam. Concerning the beam combining nulling instrument, the ALADDIN design is inherited from a Definition Study of the VLTI/GENIE instrument. In this paper, we demonstrate how the ALADDIN instrument preliminary definition can be made simpler and more representative of a space instrument than GENIE thanks to both the outstanding atmospheric properties of Dome C and the dedicated architecture of the system. Finally, we discuss the compatibility of the instrument with the Antarctic environment and constraints, and underline the experimental and industrial know-how learnt from the MAII and PERSEE nulling breadboards in which our Team is also involved. [ABSTRACT FROM AUTHOR]

Aims. In the framework of the multi-wavelength and very long baseline interferometry (VLBI) monitoring program TANAMI (Tracking Active Nuclei with Austral Milliarcsecond Interferometry), we study the evolution of the parsec-scale radio emission in radio galaxies in the southern hemisphere and their relationship to the γ-ray properties of the sources. Our study investigates systematically, for the first time, the relationship between the two energy regimes in radio galaxies. In this first paper, we focus on Fermi-LAT-detected sources. Methods. The TANAMI program monitors a large sample of radio-loud AGN at 8.4 GHz and 22.3 GHz with the Australian long baseline array (LBA) and associated telescopes in Antarctica, Chile, New Zealand and South Africa. We performed a kinematic analysis for five γ-ray detected radio galaxies using multi-epoch 8.4 GHz VLBI images, deriving limits on intrinsic jet parameters such as speed and viewing angle. We analyzed 103 months of Fermi-LAT data in order to study possible connections between the γ-ray properties and the pc-scale jets of Fermi-LAT-detected radio galaxies, both in terms of variability and average properties. We discuss the individual source results and draw preliminary conclusions on sample properties including published VLBI results from the MOJAVE (Monitoring Of Jets in Active galactic nuclei with VLBA Experiments) survey, with a total of fifteen sources. Results. We find that the first γ-ray detection of Pictor A might be associated with the passage of a new VLBI component through the radio core, which appears to be a defining feature of high-energy emitting Fanaroff-Riley type II radio galaxies. We detect subluminal parsec-scale jet motions in the peculiar AGN PKS 0521−36, and we confirm the presence of fast γ-ray variability in the source down to timescales of six hours, which is not accompanied by variations in the VLBI jet. We robustly confirm the presence of significant superluminal motion, up to βapp ∼ 3, in the jet of the TeV radio galaxy PKS 0625−35. Our VLBI results constrain the jet viewing angle to be θ <  53°, allowing for the possibility of a closely aligned jet. Finally, by analyzing the first pc-scale multi-epoch images of the prototypical compact symmetric object (CSO) PKS 1718−649, we place an upper limit on the separation speed between the two mini-lobes. This in turn allows us to derive a lower limit on the age of the source. Conclusions. We can draw some preliminary conclusions on the relationship between pc-scale jets and γ-ray emission in radio galaxies, based on Fermi-LAT-detected sources with available multi-epoch VLBI measurements. We find that the VLBI core flux density correlates with the γ-ray flux, as seen in blazars. On the other hand, the γ-ray luminosity does not show any dependence on the core brightness temperature and core dominance, which are two common indicators of jet Doppler boosting. This seems to indicate that γ-ray emission in radio galaxies is not driven by orientation-dependent effects, as in blazars, in accordance with the unified model of jetted AGN. [ABSTRACT FROM AUTHOR]

This paper gives an overview of conceptual studies that have been realized since 2007 on 30 m towers for Dome C taking into account local available infrastructures and conditions. Some 30 m tower's concepts are presented and finite element simulations are carried to determine their dynamic behaviour including wind-induced vibrations, and to optimize their design. [ABSTRACT FROM AUTHOR]

The Phase A design study of PILOT-the Pathfinder for an International Large Optical Telescope-has demonstrated that a widefield 2.5 m optical/IR telescope can be constructed at Concordia for a reasonable cost. There are no technical "show stoppers", and the cost of logistics is also quantifiable and reasonable. A strong science case has been developed and published as three separate papers. In order to proceed further, the next step is to undertake a detailed design study and identify potential manufacturers. [ABSTRACT FROM AUTHOR]

COCHISE is a 2.6 meter millimetric telescope, mainly devoted to cosmological observations, located at Concordia. In this paper we report on the installation phases and preliminary operations performed with this instrument. At present, COCHISE is the largest telescope located at Concordia, for that reason it represents a pathfinder for future telescopes. [ABSTRACT FROM AUTHOR]

In this paper, we describe the expected performance of ALADDIN, a nulling interferometer project optimised for operation at Dome C. After reviewing the main atmospheric parameters pertaining to infrared interferometry on the high Antarctic plateau, we shortly describe the ALADDIN instrument and compute its estimated performance in terms of the smallest exozodiacal dust disc density that can be detected. Our estimations are based on a thorough end-to-end software simulator previously developed for the GENIE nulling interferometer project at VLTI. We then propose a possible mission scenario, where the southern target stars of future exo-Earth characterisation missions can be surveyed for the presence of bright exozodiacal discs (>50 zodi) within one winter-over at Concordia. [ABSTRACT FROM AUTHOR]

In a first part the paper reviews some of the major Spitzer legacy imaging surveys to show the quantity of data available, and the subsequent need for spectroscopic follow-up surveys on equivalent wide fields. They are required for many science cases, as giant star forming regions, young planetary nebulea, the Galactic Centre, nearby galaxies, distant galaxy clusters. This capability of wide, integral field spectroscopy, missing in all the existing and planned astronomical facilities, thus, appears among the most pertinent choice for the future of astronomy at Dome C. For the instrumental solution, a flexibility in the choice of spectral resolution and spectral domain on a broad infrared range is desirable to be able to undertake a large variety of study, on extragalactic and galactic fields as well. This capability can be only offered by an Imaging FTS. It fully benefits from the low thermal background emission of Dome C, particularly in the 1.8 to 5.5 μm range, and reach an optimum sensitivity by imaging emission lines. In a difficult site as Dome C, a dedicated, medium-size telescope would be the most effective way of exploiting such an instrument. [ABSTRACT FROM AUTHOR]

Preliminary site testing datasets suggest that Dome C in Antarctica is one of the best sites on Earth for astronomical observations in the 200 to 500-μm regime, i.e. for far-infrared (FIR) and submillimetre (submm) astronomy. We present an overview of potential science cases that could be addressed with a large telescope facility at Dome C. This paper also includes a presentation of the current knowledge about the site characterics in terms of atmospheric transmission, stability, sky noise and polar constraints on telescopes. Current and future site testing campaigns are finally described. [ABSTRACT FROM AUTHOR]

The construction of a small-sized panel based on anthocyanins from Erythrina crista-galli as sensitizers is reported in this work. The device, named KD12, was placed indoors at the Artigas Antarctic Scientific Base from March 2019 to December 2020. Here is released for the first time, the indoor installation of dye-sensitized solar cells based on pigments from the Uruguayan national flower at an Antarctic Base and the evaluation of their performance during nineteen months. The panel showed good stability and maintained its efficiency conversion performance over the period. The output power, voltage and conversion efficiency generated for this device mainly depended on irradiance and external factors as light reflection due to snow or artificial bulbs near the area. Additional protection was provided by the double-glass window in front of the panel, lowering lighting irradiance and changing spectral characteristics of the light incident the device. A new prospect raised here: the potential application of anthocyanins as sensitizers for indoor electricity generation in the Antarctic area with long term operability, where low temperatures are helpful considering the thermal stability of the dyes. These constitute an interesting first step of a low-cost alternative searching for clean energy generation sources, focusing on a cold region like Antarctica. [ABSTRACT FROM AUTHOR]

We present the latest results of our on-going closed-loop "end-to-end" numerical adaptive optics (AO) simulations concerning both a standard-AO and a three-star ground-layer AO system for a near-infrared 2-m class telescope at Dome C, Antarctica. We demonstrate that Dome C is an ideal site for wide-field AO-aided astronomy, define in details the AO system(s) optimized for the median turbulence profile considered, and finally show that a ~0.3 Strehl ratio and 200- mas-wide stable point-spread function is reached in band J on at least a 15′ -diameter field. [ABSTRACT FROM AUTHOR]

Muon telescopes are instruments devoted to the observation of muons. They are produced in the atmosphere by means of the interaction of cosmic ray and solar energetic particles with atmospheric nuclei. Muons, as cosmic rays that produce them, present non uniform arrival directions and temporal variations at ground level and, along certain observation directions, could forecast the arrival of interplanetary coronal mass ejections (ICMEs) at the Earth, even earlier than neutron monitors. However, multidirectional muon telescopes are not easily affordable because of their complexity, size and cost. In this work, we present the muon impact tracer and observer (MITO) design concept. It is composed of only two stacked scintillators (1 m[2]) with an optional lead layer that allows the filtering of unwanted particles depending on the type of application. In the case presented here, a 10 cm lead layer corresponding to the lead of a 3NM64 neutron monitor around which MITO has been built. Eight photomultipliers (PMTs) gather the light emerging from the four lateral sides of the scintillators. MITO has been conceived not only to achieve muon flux registering, but also to register muon arrival directions through the capture and analysis of multiple PMT pulse height data. The number of scintillators and electronic components is reduced, simplifying its design and construction and reducing complexity, volume, weight, power consumption and cost, and thus, achieving a reasonable performance-cost ratio in comparison to other directional telescopes based on two-layer matrices. The first prototype was shipped from Spain to Antarctica where it is now recording data. Some preliminary results are also presented. [ABSTRACT FROM AUTHOR]

Context. Dome C in Antarctica is a promising site for photometric observations thanks to the continuous night during the Antarctic winter and favorable weather conditions. Aims.We developed instruments to assess the quality of this site for photometry in the visible and to detect and characterize variable objects through the Antarctic Search for Transiting ExoPlanets (ASTEP) project. Methods. Here, we present the full analysis of four winters of data collected with ASTEP South, a 10 cm refractor pointing continuously toward the celestial south pole. We improved the instrument over the years and developed specific data reduction methods. Results. We achieved nearly continuous observations over the winters. We measure an average sky background of 20 mag arcsec−2 in the 579–642 nm bandpass. We built the lightcurves of 6000 stars and developed a model to infer the photometric quality of Dome C from the lightcurves themselves. The weather is photometric 67.1 ± 4.2% of the time and veiled 21.8 ± 2.0% of the time. The remaining time corresponds to poor quality data or winter storms. We analyzed the lightcurves of σ Oct and HD 184465 and find that the amplitude of their main frequency varies by a factor of 3.5 and 6.7 over the four years, respectively. We also identify 34 new variable stars and eight new eclipsing binaries with periods ranging from 0.17 to 81 days. Conclusion. The phase coverage that we achieved with ASTEP South is exceptional for a ground-based instrument and the data quality enables the detection and study of variable objects. These results demonstrate the high quality of Dome C for photometry in the visible and for time series observations in general. [ABSTRACT FROM AUTHOR]

The status of the AMICA project is reported. Final tests are currently running at Teramo Observatory before moving the instrument to Antarctica. AMICA is a camera equipped with two array detectors to perform astronomical imaging in the 2-28 μm band. It will be mounted at the IRAIT focal plane. Its very special feature is the antarctic operability. AMICA subsystems have been tested at typical antarctic conditions, in order to adopt technological solutions that ensure the correct operation of AMICA even on the antarctic plateau. Moreover, since human operations are not possible during the antarctic "winter", AMICA has been designed to operate in a completely automatic mode. AMICA is essentially aimed to demonstrate the potential of Antarctica for Infrared Astronomy and should therefore produce significant data, both for astronomy and site-testing. In addition, the experience gained in its technological development will be useful for building future astronomical instruments for extreme environment sites. [ABSTRACT FROM AUTHOR]

The ARENA Solar Astrophysics Working Group (WG6) is reviewing the exceptional site conditions prevailing at Dome C/Concordia making it a unique place on Earth for solar observations: excellent seeing, low sky brightness, low water vapour and high duty cycle. These qualities open science programmes which can combine very high resolution, coronagraphy, infrared access, and long time series (continuity). Major objectives accessible are the chromosphere-corona interface at very high resolution, direct magnetic field measurements in the chromosphere (prominences) and in the corona, 2D imaging spectroscopy and waves. A first mid-size facility is proposed and described, AFSIIC (Antarctica Facility for Solar Interferometric Imaging and Coronagraphy), using 3×υ50 cm off-axis telescopes (1.4 m equivalent telescope) to access these objectives with the proper flux, angular resolution and coronagraphic potential. Support infrastructure and logistics have been studied and are discussed, noticeably a 30 m tower to place the observatory over the very thin surface turbulent layer of Dome C. [ABSTRACT FROM AUTHOR]

We present preliminary results of the measurements of sky transparency conducted at Dome C during the winter 2008. Using MOLIERE modeling, we estimate a low precipitable water vapour content above Concordia station, which is very promising for future submillimetre wave observations on the Antarctic Plateau. [ABSTRACT FROM AUTHOR]

Performed in November 2007, the observation of the hot Jupiter-like exoplanet Gliese 86b constituted the first attempt of exoplanet detection with MIDI, and also the first VLTI observation using AMBER and MIDI simultaneously. Fringes were obtained for both instruments with the aim to correct the interferometric phase in N-band from the wet dispersion using the fringes in K-band. In N-band, it appears that the theoretical interferometric phase would be a curved-like function with an amplitude of about 0.04?. According to the MIDI phase measurements of the calibrator HD 9362, we roughly estimate that a precision of about 0.33? is currently reached. The AMBER data, obtained in parallel, were too noisy for correcting the corresponding dispersion in N band, the correction accuracy standing at factor 10 above the detection. Dome C presents a very low absolute humidity level. In homogeneous humidity conditions, the curvature amplitude of the phase term due to water vapor, is also ten times smaller than the MIDI one, and may stand below the planetary phase signature. However differential humidity measurements would be required to completely validate the potential of this site. [ABSTRACT FROM AUTHOR]

Optical Interferometry has had an impressive 30-year run of innovation, prototyping and implementation. Some half-dozen arrays are now in operation. Publications are increasing exponentially. In a future phase of advanced facility development, interferometry could move in any of several directions: increased sensitivity, higher resolution, better imaging. What role may the Antarctic have in the future? [ABSTRACT FROM AUTHOR]

This report provides the recommendations of ARENA Working Group 1 concerning the development of and objectives for a wide-field, optical/infrared, 2.5m class telescope for Antarctica. It discusses the key science drivers for such a telescope, the performance and capabilities it should have, and the logistics and infrastructure issues relevant to its construction and operation. [ABSTRACT FROM AUTHOR]

The Antarctic Plateau is considered an ideal location for ground-based astronomy from the visible to the millimetric wavelength, thanks to both the low thermal emission and the high transparency of the atmosphere. The Microwave Limb Sounder instrument on board the AURA satellite, provides the vertical profiles of temperature, humidity and several gases present in atmosphere. These profiles can be used as input in radiative transfer model to simulate the atmospheric transmissivity at the different wavelengths. [ABSTRACT FROM AUTHOR]

It has already been demonstrated that a mesoscale meteorological model such as Meso-NH (Lafore et al. 1998) is highly reliable in reproducing 3D maps of optical turbulence (Masciadri et al. 1999; Masciadri & Jabouille 2001; Masciadri et al. 2004). Preliminary measurements above the Antarctic Plateau have so far indicated a pretty good value for the seeing: 0.27″ (Lawrence et al. 2004 ), 0.36″ (Agabi et al. 2008) or 0.4″ (Trinquet et al. 2008) at Dome C. However some uncertainties remain. That's why our group is focusing on a detailed study of the atmospheric flow and turbulence in the internal Antarctic Plateau. Our intention is to use the Meso-NH model to do predictions of the atmospheric flow and the corresponding optical turbulence in the internal plateau. The use of this model has another huge advantage: we have access to informations inside an entire 3D volume which is not the case with observations only. Two different configurations have been used: a low horizontal resolution (with a mesh-size of 100 km) and a high horizontal resolution with the grid-nesting interactive technique (with a mesh-size of 1 km in the innermost domain centered above the area of interest). We present here the turbulence distribution reconstructed by Meso-NH for 16 nights monitored in winter time 2005, looking at the the seeing and the surface layer thickness. [ABSTRACT FROM AUTHOR]

We compare the merits of potential observatory sites on the Antarctic Plateau, in regard to the boundary layer, cloud cover, free atmosphere seeing, aurorae, airglow, and precipitable water vapour. We find that (a) all Antarctic sites are likely compromised for optical work by airglow and aurorae; (b) Dome A is the best existing site in almost all respects; (c) there is an even better site ("Ridge A") 150 kms SW of Dome A; (d) Dome F is a remarkably good site except for aurorae; (e) Dome C probably has the least cloud cover of any of the sites, and might be able to use a predicted 'OH hole' in the Spring. [ABSTRACT FROM AUTHOR]

This is a brief summary of the 2nd ARENA conference, including statistical information and a short review of the talks. The conference ended up with the creation of 6 working groups aimed at preparing the final ARENA roadmap in the fields of astronomy and astrophysics where Antarctic atmospheric conditions at Dome C could lead to compelling scientific breakthroughs. The results of their reflections and recommendations will be presented at the third and final ARENA conference to be held in May 2009. [ABSTRACT FROM AUTHOR]

Dome A, the summit of the Antarctic plateau, is expected to have even better atmospheric conditions for ground-based astronomy than Dome C. Instruments to evaluate and exploit Dome A's astronomical potential must operate within logistical constraints, which are currently very stringent. Instrumentation now at Dome A exemplifies the techniques and solutions required by this environment. Future instrumentation and infrastructure will allow the qualities of the site to be exploited much more fully. [ABSTRACT FROM AUTHOR]

Cosmic shear offers a remarkably clean way to measure the equation of state of the Universe and its evolution. Resolution over a wide field is paramount, and Antarctica offers unique possibilities in this respect. There is an order of magnitude gain in speed over temperate sites, or a factor three in surface density. This means that PILOT outperforms much larger telescopes elsewhere, and can compete with the proposed DUNE space mission. [ABSTRACT FROM AUTHOR]

Excellent seeing, coronal conditions, and very low IR thermal background are qualities of the Dome C/Concordia station site that will allow unique solar astrophysics science. We review the science case for inner corona observations (onset of the coronal heating mechanism still poorly understood) and the promises of high angular resolution to disentangle the possible mechanisms at work between waves, convection, and reconnection in this particularly magnetically structured solar atmosphere between the high chromosphere and inner corona. For coronagraphy, IR and high resolution possibilities, Dome C is a case by itself between classical ground-based sites and space opportunities. Telescopes from 50 cm (coronagraphy oriented) to 4m (full high resolution advantage including IR access) are proposed to benefit from these remarkable observing capabilities. Using 3 × Ø50 cm off-axis telescopes, we first propose a medium size facility (1.4 m equivalent telescope) for very high resolution access, ADSIIC (Antarctica Demonstrator of Solar Interferometric Imaging & Coronagraphy), before the ultimate 9-telescope Solar Facility equivalent to a 4m diameter telescope: A-FOURMI (Antarctica 4m Interferometer). Finally, 30m tower designs and their logistics using standard containers and elementary elements of 6m maximum length, are presented and discussed. These towers are indeed of general interest also for the other optical and IR telescopes intended for Dome C/Concordia, allowing to get over most of the turbulent ground layer and to reach the best possible permanent seeing conditions (better than half an arcsec). [ABSTRACT FROM AUTHOR]

A case for infrared interferometry at Dome C is developed. The objective is to pave the way for future space missions dedicated to the spectroscopic IR characterization of exoearth atmospheres, by investigating one of the major, and least known, noise sources (amount of exozodiacal light) in the direct detection telluric exoplanets. An antarctic nuller is the optimal answer for this purpose, providing with relatively modest 1m apertures a capability that outperforms a pair of 8m telescopes on a temperate site. [ABSTRACT FROM AUTHOR]

TheWide-field High-resolution Infrared TElescope (WHITE) that we propose for Dome C will be dedicated in the first years of its life to carry out a few legacy surveys (well-focused in terms of science objectives and time). WHITE would have an angular resolution of ∼0.3" uniform over ∼0.7 sq. deg. in the wavelength range 1 μm to 5 μm, which means that we will very efficiently use all the available observational time during night time and day time. Moreover, the deepest observations will be performed by summing up shorter individual frames. We will obtain temporal information that can be used to study variable objects. The three key science objectives of WHITE are: 1) A survey of the Magellanic Clouds to make a complete census of young stellar objects in the Clouds and in the Bridge and to study their star formation history and the link with the Milky Way. The interaction of the two Clouds with our Galaxy might be the closest example of a minor merging event that could be the main driver of galaxy evolution in the last 5 Gyrs. 2) Establishing of the first sample of dusty supernovae at z < 1.2 in the near infrared range (1.0 - 5.0 μm) to constrain the equation of state of these obscured objects, study the formation of dust in galaxies, and build the first high resolution sample of high-redshift galaxies observed in their optical frame 3) A very wide weak lensing survey that would allow to estimate the equation of state of dark energy in a way that would favourably compete with space projects. [ABSTRACT FROM AUTHOR]

Data from single and multi-frequency active acoustic surveys conducted annually in the vicinity of the South Shetland Islands, Antarctica were re-analyzed using updated procedures for delineating volume backscattering due to Antarctic krill, adjusting for signal contamination due to noise, and compensating for diel vertical migration of krill outside of the acoustic observation window. Intra-and inter-seasonal variations in krill biomass density and dispersion were derived from the re-processed data set for surveys conducted in the austral summers of 1991/1992 through 2001/2002. Estimated biomass density ranged from 1 to 60 g m–2, decreasing from mid-range levels in 1991/1992 to a minimum in 1992/1993–1993/1994, increasing to a peak in 1996/1997–1997/1998, and decreasing again through 2000/2001–2001/2002. Although this variability may be attributed to changes in the spatial distribution of krill relative to the survey area, comparisons with the proportion of juvenile krill in simultaneous net samples suggest that the changes in biomass density are consistent with apparent changes in reproductive success. A truncated Fourier series fit to the biomass density time series is dominated by an 8-year cycle and predicts an increase in krill biomass density in 2002/2003 and 2003/2004. This prediction is supported by an apparent association between cycles in the extent of sea ice cover and per-capita krill recruitment over the last 23 years and indications that ice cover in the winter of 2002 is seasonally early and extensive. [Copyright &y& Elsevier]