Here are a few personnal thoughts as an introduction to the second conference of the ARENA network that will focus on the most promising astrophysical science cases at CONCORDIA/Dome C.

The first site testing campaigns started at Dome C during the summer season 2000–2001. Since then, each further summer has been exploited, as well as the first three winter seasons permitted by the opening of the Concordia station in 2005. Many of the astronomical site properties begin now to be well known, although some more still need to be adressed and more statistics is obviously required.

The Gattini-DomeC project, part of the IRAIT site testing campaign and ongoing since January 2006, consists of two cameras for the measurement of optical sky brightness, large area cloud cover, and auroral detection above the DomeC site, home of the French-Italian Concordia station. The cameras are transit in nature and are virtually identical except for the nature of the lenses. The cameras have operated throughout the past two Antarctic winter seasons and here we present the results obtained from the 2006 winter-time dataset of the wide field “All-sky camera".

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.

The search for extrasolar transiting planets requires high accuracy photometric observations over a long time basis. The method therefore favors observing sites allowing for long uninterrupted observations, or observations with space satellites. The first space mission searching for planetary transits is the French-led CoRoT mission launched in December 2006. Its longest observing sequences span 150 days, whereas Dome C can provide a ground-based site for observations over 2–3 months. Full observational coverage of at least three transit events up to about two weeks orbital period can be obtained from Dome C during one winter season when realistic conditions for cloud coverage are taken into account. The efficiency can be further optimized if Dome C is combined with other sites at low-latitudes, closing the gap of the summer break in Antarctica.


Asteroseismology requires observables registered in stringent conditions: very high sensitivity, uninterrupted time series, long duration. These specifications then allow to study the details of the stellar interior structure.
Space-borne and ground-based asteroseismic projects are presented and compared. With CoRoT as a precursor, then Kepler and maybe Plato, the roadmap in space appears to be precisely designed. In parallel, ground-based projects are necessary to provide different and unique information on bright stars with Doppler measurements.
Dome C appears to be the ideal place for ground-based asteroseismic observations. The unequalled weather conditions yield a duty cycle comparable to space. Long time series (up to 3 months) will be possible, thanks to the long duration of the polar night.

The Wide-field Infrared Survey Explorer (WISE) will map the whole sky in 6 months followingits launch and in-orbit checkout. Launch is currently scheduled for November, 2009. WISEshould cover more than 95% of sky with sensitvities of 120, 160, 650 & 2600 μJy inbands centered at 3.3, 4.7, 12 & 23 μm wavelength. The angular resolution shouldbe 6'' except at 23 μm where diffraction gives 12''.The low thermal background makes telescopes at Dome C very useful forfollow-up observations of WISE sources.

The Herschel Space Observatory is the fourth cornerstone mission in the European Space Agency (ESA) science programme, and is scheduled for launch in late 2008. It will perform imaging photometry and spectroscopy at far infrared and submillimetre wavelengths, covering approximately the 60–670 μm range. The three payload instruments are briefly described, and examples of their scientific capabilities are given from the Guaranteed Time Key Projects which have already been approved. Prospects for future far infrared/submillimetre space astronomy are briefly reviewed, and the implications for possible Antarctic facilities operating in this spectral region are discussed.

We review the investigation of Super-Earths. After defining this categoryof planets, we briefly defend the paradigm that they may be good targets forthe search of Life, since they may be abundant and all terrestrial conceptsare valid for them.We then describe the scientific benefits of their characterizationby analyzing (by spectroscopy and polarimetry) the light they reflect fromthe parent star. We finally compare the performances of space missions and Dome Capproaches.

The success of projects aiming at the detection of Earth-like planetsorbiting nearby stars and the physical-chemical characterization ofthe terrestrial planet's atmospheres requires a careful selection ofthe target stars as well as a detailed knowledge of their propertiesand of the stellar environment. Both aspects have to be fulfilled withspecific observations. The conditions of Dome C for astronomicalobservations are very much appropriate to make a significantcontribution to these preparatory observations. Some examples arepresented here, in particular related to high-precision photometry andhigh spatial resolution observations.

VISTA is the new 4-metre wide-field survey telescope nownearing completion at ESO's Paranal Observatory.It has a single instrument, a very large near-infrared camera with a 1.65 degree diameter field, 67 Mpixels and 0.6 deg2 active detector coverage. Most of VISTA's observing time will be used by six Public Surveys recently selected by ESO.Comparing to possible future surveys from Dome C,a 2.4 m class telescope at Dome C would give slightly better sensitivity than VISTA at Y, J, H bands, but would require anunrealistic number of near-IR detectors to match VISTA's field of view.In the Kdark and visible bands the comparisonis much more favourable to Dome C, so a goodstrategy for Dome C surveys is to emphasise complementarityby concentrating on the Kdark band, and i-band weak lensingsurveys.

The Atacama Large Millimeter/submillimeter Array (ALMA) is currently being constructed at the 5000 m Chajnantor plateau in the Chilean Andes. ALMA has been designed and is being built to deliver transformational science in the millimeter and submillimeterregime for many years to come.We briefly describe the project status and timeline.The Atacama Pathfinder Experiment (APEX), built at the same site, is already operational and proves to be an effective survey instrument. We discuss which niches in millimeter/submillimeter astronomy will remain open for a possible facility in Antarctica.

Solar magnetic fields evolve on many time-scales, e.g., thegeneration, migration, and dissipation of magnetic flux during the 22-yearmagnetic cycle of the Sun. Active regions develop and decay over periods ofweeks. The build-up of magnetic shear in active regions can occur within lessthan a day. At the shortest time-scales, the magnetic field topology can changerapidly within a few minutes as the result of eruptive events such as flares,filament eruptions, and coronal mass ejections. The unique daytime seeingcharacteristics at Dome C, i.e., continuous periods of verygood to excellent seeing during almost the entire Antarctic summer, allow us toaddress many of the top science cases related to the evolution of solarmagnetic fields. We introduce the Advanced Solar Photometric Imager andRadiation Experiment and present the science cases for synoptic solarobservations at Dome C. Furthermore, common science cases concerningthe solar-stellar connection are discussed in the context of the proposedInternational Concordia Explorer Telescope.

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 4 m (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 4 m diameter telescope: A-FOURMI (Antarctica 4 m Interferometer). Finally, 30 m tower designs and their logistics using standard containers and elementary elements of 6 m 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).

In a first part the paper reviews some of the major Spitzer legacy imagingsurveys to show the quantity of data available, and the subsequent need forspectroscopic follow-up surveys on equivalent wide fields. They arerequired for many science cases, as giant star forming regions, youngplanetary nebulea, the Galactic Centre, nearby galaxies, distant galaxyclusters. This capability of wide, integral field spectroscopy, missing inall the existing and planned astronomical facilities, thus, appears amongthe most pertinent choice for the future of astronomy at Dome C. For theinstrumental solution, aflexibility in the choice of spectral resolution and spectral domain on abroad infrared range is desirable to be able to undertake a large variety of study, onextragalactic and galactic fields as well. This capability can be only offered byan Imaging FTS. It fully benefits from the low thermal backgroundemission of Dome C, particularly in the 1.8 to 5.5 μm range, and reachan optimum sensitivity by imaging emission lines. In a difficult site asDome C, a dedicated, medium-size telescope would be the most effective wayof exploiting such an instrument.

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 1 m apertures a capability that outperforms a pair of 8 m telescopes on a temperate site.

We present a near-infrared (JHKs) photometric catalogincluding 14 822 341 point sourcesfor a 40 deg2 area of the Large Magellanic Cloud,2 769 682 sources for an 11 deg2 area of the Small Magellanic Cloud,and 434 145 sources for a 4 deg2 area of the Magellanic Bridge.The 10σ limiting magnitudes are 18.8, 17.8, and 16.6 magat J, H, and Ks, respectively.The photometric and astrometric accuracies for bright sourcesare 0.03–0.04 mag and 0$\farcs$1.Based on the catalog, we also presentcolor-color and color-magnitude diagramsfor point sources toward the LMCthat show features characteristic of MS stars, giants, AGB stars,and Herbig Ae/Be stars in the LMC and background galaxies.We also present the results of analysisfor two active star-forming regions, N159/N160 and N11 in the LMC, thatdemonstrate the usefulness of our data for studies of star formation.Catalog data are available athttp://pasj.asj.or.jp/v59/n3/590315/and ftp://dbc.nao.ac.jp/DBC/ADACnew/.

The Wide-field High-resolution Infrared TElescope (WHITE) that we propose for Dome Cwill 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.

We have identified over 1000 candidate Young StellarObjects (YSOs) in the Large Magellanic Cloud as part of the Spitzer Space Telescope Surveying the Agents of a Galaxy's Evolution (SAGE) Legacy program. The YSOs, detected by their excess infrared emission above a stellar photosphere, representearly stages of evolution, still surrounded by disks and/or infalling envelopes.The candidate YSOs were selected from regions of color-magnitude space least confused with other IR-bright populations.Our YSO list is therefore biased towards intermediate- to high-mass and young evolutionarystages, because these overlap less with galaxies and evolved starsin color-magnitude space.We derived masses of the YSOs from SED-fitting, and extrapolated the mass function usinga standard IMF to compute a current star formation rate of ~0.06 M๏/yr, which is at the low-end ofestimates based on total ultraviolet and infrared flux from the galaxy (~0.05-0.25 M๏/yr); and consistent with the expectation that our current YSO list is incomplete.High spatial resolution K_dark- and L-band observations at Dome C could distinguish the lower-mass YSOs from galaxies, based on their morphologies(diffuse vs. point sources).This will add thousands more YSOs to our census and improve our estimates of star formationrate, molecular cloud lifetimes, and hierarchical star formation.In addition, the high spatial resolution Dome C observations can detect multiplicity in the SAGE-identified YSOs which can be incorporated into our YSO SED models.