John W. V. Storey

Polar research: Six priorities for Antarctic science

Antarctica. The word conjures up images of mountains draped with glaciers, ferocious seas dotted with icebergs and iconic species found nowhere else. The continent includes about one-tenth of the planets land surface, nearly 90% of Earths ice and about 70% of its fresh water. Its encircling ocean supports Patagonian toothfish and krill fisheries, and is crucial for regulating climate and the uptake of carbon dioxide by sea water.

An analysis of temperatures and wind speeds above Dome C, Antarctica

Department of Geography, University of Idaho, Moscow, Idaho, USA-Abstract. A good astronomical site must fulflll several criteria including low atmospheric turbulence and lowwind speeds. It is therefore important to have a detailed knowledge of the temperature and wind conditions ofa location considered for future astronomical research. Antarctica has unique atmospheric conditions that havealready been exploited at the South Pole station. Dome C, a site located on a local maximum of the Antarcticplateau, is likely to have even better conditions. In this paper we present the analysis of two decades of windspeed measurements taken at Dome C by an automated weather station (AWS). We also present temperature andwind speed proflles taken over four Antarctic summers using balloon-borne weather sondes. We will show that aswell as having one of the lowest average wind speed ever recorded at an existing or potential observatory, DomeC also has an extremely stable upper atmosphere and a very low inversion layer.Key words. Site Testing { Atmospheric afiects { Balloons

Atmospheric turbulence at the South Pole and its implications for astronomy

To investigate the low-atmosphere turbulence at the South Pole, we have measured, using a SODAR, the temperature fluctuation constant (C 2 ) during winter, as a function of altitude up to 890 m. We found that the turbulence was on average concentrated inside a boundary layer sitting below 270 m. While at the peak of winter the turbulence was stable and clearly bounded, during other seasons there was a more complex turbulence profile which extended to higher altitudes. We found that this behaviour could be explained by the horizontal wind speed conditions whose altitude profile closely matched the turbulence profile. We also observed the presence of a vertical wind velocity change of direction at an altitude range corresponding to the turbulent region. The turbulence gives rise to an average seeing of 1:73 00 , which compares poorly with the best astronomy sites. The location of the turbulence, however, means that the seeing quickly decreases above the boundary layer (dropping to 0:37 00 above 300 m). We also have recorded the largest isoplanatic angle (AO= 3:3 00 ) and the longest coherence time (AO= 2: 9m s)

A roadmap for Antarctic and Southern Ocean science for the next two decades and beyond

Abstract Antarctic and Southern Ocean science is vital to understanding natural variability, the processes that govern global change and the role of humans in the Earth and climate system. The potential for new knowledge to be gained from future Antarctic science is substantial. Therefore, the international Antarctic community came together to ‘scan the horizon’ to identify the highest priority scientific questions that researchers should aspire to answer in the next two decades and beyond. Wide consultation was a fundamental principle for the development of a collective, international view of the most important future directions in Antarctic science. From the many possibilities, the horizon scan identified 80 key scientific questions through structured debate, discussion, revision and voting. Questions were clustered into seven topics: i) Antarctic atmosphere and global connections, ii) Southern Ocean and sea ice in a warming world, iii) ice sheet and sea level, iv) the dynamic Earth, v) life on the precipice, vi) near-Earth space and beyond, and vii) human presence in Antarctica. Answering the questions identified by the horizon scan will require innovative experimental designs, novel applications of technology, invention of next-generation field and laboratory approaches, and expanded observing systems and networks. Unbiased, non-contaminating procedures will be required to retrieve the requisite air, biota, sediment, rock, ice and water samples. Sustained year-round access to Antarctica and the Southern Ocean will be essential to increase winter-time measurements. Improved models are needed that represent Antarctica and the Southern Ocean in the Earth System, and provide predictions at spatial and temporal resolutions useful for decision making. A co-ordinated portfolio of cross-disciplinary science, based on new models of international collaboration, will be essential as no scientist, programme or nation can realize these aspirations alone.

Far-infrared rotational emission by carbon monoxide

Accurate theoretical collisional excitation rates are used to determine the emissivities of CO rotational lines 10 to the 4th power/cu cm n(H2), 100 K T 2000 K, and J 50. An approximate analytic expression for the emissitivities which is valid over most of this region is obtained. Population inversions in the lower rotational levels occur for densities n(H2) approximately 10 (to the 3rd to 5th power)/cu cm and temperatures T approximately 50 K. Interstellar shocks observed edge on are a potential source of millimeter wave CO maser emission. The CO rotational cooling function suggested by Hollenbach and McKee (1979) is verified, and accurate numerical values given. Application of these results to other linear molecules should be straightforward.

The Near-Infrared Sky Emission at the South Pole in Winter

The Antarctic plateau provides superb sites for infrared astronomy, a result of the combination of low temperatures, low levels of precipitable water vapor, high altitude, and atmospheric stability. We have undertaken measurements of the sky background from 1 to 5 μm at the South Pole, using a single channel InSb spectrometer, the Infrared Photometer Spectrometer (IRPS), during the winter (dark) period of 1995. The IRPS records the DC level of the sky flux through a 4° beam and a variety of broadband and narrowband (1%) filters. It can be scanned in elevation from horizon to horizon through the zenith. We find a 20-100 times reduction in the background of thermal emission compared to that from mid-latitude sites such as Siding Spring and Mauna Kea, with typical background levels of 80-200 μJy arcsec-2 at 2.43 μm, 100-300 mJy arcsec-2 at 3.6 μm and ~0.5 Jy arcsec-2 at 4.8 μm. Airglow emission contributes significantly to the sky flux shortward of ~2.4 μm, which is why the Kdark (2.27-2.45 μm) band emission does not drop to the 10-20 μJy arcsec-2 levels originally predicted. The darkest window for IR observations from the South Pole is from 2.35 to 2.45 μm, where the fluxes from the atmosphere may drop to as low as ~50 μJy arcsec-2 at times. Airglow dominates the emission at J (1.25 μm) and H (1.65 μm), but the flux levels of 300-600 μJy arcsec-2 and 800-2000 μJy arcsec-2, respectively, are also one-third to one-half those at temperate sites. We find no evidence for any significant contribution from auroral emission to the Kdark band. During twilight, when the Sun is <10° below the horizon, scattered sunlight contributes to the sky background with a Rayleigh-type spectrum. Scattered moonlight is also evident in the sky emission at the J band when the Moon is up.

First Measurements of the Infrared Sky Brightness at Dome C, Antarctica

Dome C, Antarctica, (75 south, 123 east, 3250 m) is one of the coldest and driest locations on Earth, with exceptionally low winds throughout the atmosphere. It therefore has the potential to be an ideal site for astronomical observations. It is also an excellent site for the validation of satellite instruments. A Fourier transform infrared interferometer was deployed at Dome C during two austral summer seasons (2003 January and 2003 December/2004 January) for the purpose of acquiring satellite validation data. However, these data are also useful for understanding the infrared characteristics of the atmosphere for future astronomical experiments at Dome C. The Polar Atmospheric Emitted Radiance Interferometer measured the downwelling infrared radiance from the atmosphere (sky brightness) from 3 to 20 mm. Over 100 radiosondes were also launched during this time period. Typical measured values of the sky brightness in the clearest portions of the M, N, and Q bands are 0.9, 43, and 310 Jy arcsec 2 , respectively. The lowest measured values of sky brightness within these bands are 0.4, 34, and 200 Jy arcsec 2 . The spectral region of the Q band from about 18.7 to 19 mm is expected to be an excellent window for observations made from the Antarctic Plateau. The sky brightness has been measured between 10.60 and 11.30 m mi n theN band for comparisons to earlier studies at South Pole Station; the values in this band are similar to those in the 8.20-8.40 mm band. For the period of time covered by our observations, the sky brightness in the dark portions of the N band was less than about 50-60 Jy arcsec 2 for about 10% of the time, and less than about 75 Jy arcsec 2 for about 50% of the time. During a 5 day period of clear skies, the mean sky brightness was 47.7 Jy arcsec 2 , with a variation about this mean of 4.4 Jy arcsec 2 (1 j). Calculations of the summertime atmospheric transmission under clear skies over Dome C show that portions of the M, N, and Q bands have transmission greater than 95%, with some spectral regions greater than 99%.

Subarcsecond mid-infrared imaging of warm dust in the narrow-line region of NGC 1068

Subarcsecond 8 and 10 μm and diffraction-limited 19 μm imaging of the inner few hundred parsecs of the Seyfert nucleus in NGC 1068 shows the emission to be extended over a region of ∼70×140 pc. In particular, 10.3 μm images with spatial resolutions of 0″.5 or better reveal that the warm dust is associated with the narrow-line clouds and is probably partially mixed with the photoionized gas. Extinction considerations, however, imply that the bulk of the warm dust is located deeper in neighboring molecular clouds, the exposed surfaces of which form the narrow-line clouds

Science programs for a 2-m class telescope at Dome C, Antarctica: PILOT, the pathfinder for an international large optical telescope

The cold, dry, and stable air above the summits of the Antarctic plateau provides the best ground-based observing conditions from optical to sub-millimetre wavelengths to be found on the Earth. Pathfinder for an International Large Optical Telescope (PILOT) is a proposed 2 m telescope, to be built at Dome C in Antarctica, able to exploit these conditions for conducting astronomy at optical and infrared wavelengths. While PILOT is intended as a pathfinder towards the construction of future grand-design facilities, it will also be able to undertake a range of fundamental science investigations in its own right. This paper provides the performance specifications for PILOT, including its instrumentation. It then describes the kinds of projects that it could best conduct. These range from planetary science to the search for other solar systems, from star formation within the Galaxy to the star formation history of the Universe, and from gravitational lensing caused by exo-planets to that produced by the cosmic web of dark matter. PILOT would be particularly powerful for wide-field imaging at infrared wavelengths, achieving near diffraction-limited performance with simple tip–tilt wavefront correction. PILOT would also be capable of near diffraction-limited performance in the optical wavebands, as well be able to open new wavebands for regular ground-based observation, in the mid-IR from 17 to 40 μm and in the sub-millimetre at 200 μm.

Photodissociation regions and star formation in the Carina nebula

We have obtained wide-field thermal infrared (IR) images of the Carina nebula, using the SPIREX/Abu telescope at the South Pole. Emission from polycyclic aromatic hydrocarbons (PAHs) at 3.29 μm, a tracer of photodissociation regions (PDRs), reveals many interesting well-defined clumps and diffuse regions throughout the complex. Near-IR images (1-2 μm), along with images from the Midcourse Space Experiment (MSX) satellite (8 - 21 μm) have been incorporated to study the interactions between the young stars and the surrounding molecular cloud in more detail. Two new PAH emission clumps have been identified in the Keyhole nebula, and have been mapped in 1 2 CO(2-1) and (1-0) using the Swedish-ESO Submillimetre Telescope (SEST). Analysis of their physical properties reveals that they are dense molecular clumps, externally heated with PDRs on their surfaces and supported by external pressure in a similar manner to the other clumps in the region. A previously identified externally heated globule containing IRAS 10430-5931 in the southern molecular cloud shows strong 3.29-, 8- and 21-μm emission, the spectral energy distribution (SED) revealing the location of an ultracompact (UC) HΙΙ region. The northern part of the nebula is complicated, with PAH emission intermixed with mid-IR dust continuum emission. Several point sources are located here, and through a two-component blackbody fit to their SEDs we have identified three possible UC HΙΙ regions as well as a young star surrounded by a circumstellar disc. This implies that star formation in this region is ongoing and not halted by the intense radiation from the surrounding young massive stars.