No 73 April 1995
Image of SN 1987A eight years (!!) after explosion obtained in H band with IRIS. The scale is 0.25 arcseconds per pixel and the seeing was 0.6 arcseconds. Stars 2 and 3 are very prominent as is star 4 which is very red (cf the HST images in the optical). The supernova magnitude is approximately 17.5. Spectra obtained on the same night using the H grism show strong emission by [FeI] and [SiI] in the near-infrared. Jason Spyromilio & Bruno Leibundgut (ESO)
The Future of the AAO
The most important outcome of the 50th meeting of the AAT Board, held at Siding Spring, Sydney and Canberra at the end of March, was the declaration that both parties to the AAT Agreement intend to maintain the operation of the AAO at about its present level for at least another decade. This is a very significant statement and opens up the discussion of the future of the AAO in a very positive way, removing much of the uncertainty of the last few years. I want to take this opportunity to initiate the discussion, based on the report which I gave at the AAO Symposium at Mount Stromlo on 31 March; this is therefore a much longer ``Director's message'' than usual.
The original bi-national AAT Agreement was for 25 years up to February 1996, after which either side could give five years notice of intent to withdraw or renegotiate. Until last month there was therefore the possibility that one side or the other would announce its intention to change its level of support for the AAO radically after 2000. Although such changes are still legally possible, and of course both funding agencies are at pains to point out that there can be no guarantee of the precise level of government funding in any future year (as has always been the case, technically), the new decision represents a remarkable turn-around from the position of just a couple of years ago. Then, the UK side in particular was arguing that it would probably have to make severe cuts to its contributions to the AAO, in order to fund other parts of its astronomy programme which were seen as having higher priority. The AAO was thus faced with the possibility of operating on a much lower budget and with fewer staff by the start of the next century, or of moving away from the fundamental principle of equal funding and use by the two partner countries, or perhaps even seeking new international partners. The apparent divergence in the requirements and aspirations of the UK and Australian communities made it particularly difficult to plan ahead.
What has changed recently is not the AAO itself, although the unique 2dF instrument has undoubtedly played its part in raising the priority of the AAT compared with other telescopes, but rather the perception of the Observatory, which is recognised as a very productive and cost-effective national research facility. It is worth looking briefly at the reasons for this, to try to ensure that it remains true in the future and as a guide for running other facilities. Now is an appropriate time to take stock and draw up long term plans for the development of the AAT and the Schmidt Telescope.
The Significance of the AAT
The AAT began to come under threat about five years ago, especially on the UK side. Some people assumed that the AAT, being the oldest of the UK's major optical/IR facilities, was likely to be the least effective and one of the first to be cut if resources had to be moved into new enterprises such as the Gemini 8m telescopes. This seems a very reasonable assumption; in other quite closely related fields such as space astronomy and high energy physics, most capital facilities have very limited lifetimes at the forefront of research. However, the AAT remains a very productive telescope and other optical telescopes have shown remarkable longevity, so the situation has to be more carefully examined.
The UK has recently completed a major review of all its ground-based optical, infrared and millimetre-wave facilities. The resulting OIM Report (or `Hough Report', since the review was chaired by Prof. Jim Hough at the University of Hertfordshire) not only ranked the AAT near the top of its list but also held up the AAO as a model for how an off-shore national astronomy facility should be operated, with an independent Director answerable only and directly to a Board. On the Australian side, a similarly comprehensive review of astronomical facilities has just been completed by the National Committee for Astronomy on behalf of the Academy of Science and the Australian Research Council, under the chairmanship of Prof. Harry Hyland. This review also rated the AAO very highly. An important input to both these national reviews was the AAT Board's own assessment of the future of the AAO, in its April 1994 report Options for the AAO into the 21st Century.
The real strengths of the AAO
While it is gratifying to be recognised as a successful operation and flattering to think that this is in part due to our own efforts, it must be recognised that the AAO's reputation rests also on a mixture of natural advantages and fortunate circumstances. These factors include: a site which is one of the darkest in the world and likely to remain so; location in a technologically advanced country with easy access to the resources of a major city in Sydney; and living conditions near the telescopes which are attractive to skilled staff. This last factor also implies that the climate, being good for humans, is not the very best for astronomy, but experience has shown that for many purposes the benefits outweigh the disadvantages; the overall scientific productivity of the AAT has been as high as that of any 4m class telescope.
Other strengths are specific to the telescopes. In the case of the AAT, these mostly stem from its having been built to extremely high engineering standards in the first place. Essentially, it was built to meet a specification rather than to fit a pre-determined or capped budget. Thus it provides an extremely strong and stable platform for all types of instrumentation, as demonstrated most recently by the way in which it has been possible to add the 2dF facility. Probably no more modern telescope could have coped with the unforeseen additional weight or provided the necessary handling and access space. The 2dF itself depends on the basic Ritchey-Chrétien design of the telescope, originally adopted for totally different reasons in that it offered the best scope for wide-field photography; doing multi-object spectroscopy with optical fibres and CCD spectrographs was certainly not one of the design goals in the early 1970s. Although the equatorial mounting of the AAT is now seen as old fashioned, given the move to alt-azimuth systems with their mechanical engineering and cost advantages, there are few if any practical disadvantages in having an equatorial mounting. In particular, all the benefits of computer control of the telescope and instruments apply equally well to the AAT, while the very large and stable coudé rooms provide an ideal environment for advanced experimental work in areas such as interferometry.
The Schmidt Telescope too was built to extremely high standards and has proved itself both very reliable and capable of adapting to technological change, for example with the innovative fibre-fed multi-object spectroscopy system, FLAIR.
The third feature of the AAO operation which seems to have been a factor in its success is the management and staffing policies which were established early on by far-sighted AAT Boards; as well as having an independent Board and Director, the stable engineering, technical and administrative teams at the telescopes and in Epping have been key ingredients. On the other hand, having most of the research staff on fixed term appointments has meant a steady evolution of scientific capabilities and priorities which has kept up with, and in some cases led, the international development of astronomy. Perhaps the most important factor is the simple fact that the AAO has always had one clear, dominant objective, which is to operate the AAT (and, since 1988, the UK Schmidt Telescope) as effectively as possible.
Exploiting the AAO's advantages
The factors listed above mean that the AAO has been able to move quickly and effectively to take advantage of technological innovations, and to respond rapidly to astronomical developments. For example, when SN1987A erupted in February 1987, Peter Gillingham was able to put together a temporary ultra-high dispersion spectrograph in time to get unrepeatable data, and this subsequently led to the construction of the UHRF by the UCL team, an instrument of unparalleled performance which is now yielding new fundamental physical data. The steady evolution of multi-object optical fibre systems, from Peter Gray's first prototype through Autofib to the new 2dF with 400 fibres covering a two-degree field, is another example of technical development going hand in hand with astronomy, involving close liaison between astronomers and engineers working directly at the telescope. Most recently, there has been the development of the MAPPIT optical interferometer and a prototype adaptive optics system, both led by teams from the University of Sydney and both exploiting the AAT west coudé room as an experimental laboratory.
What is the scope for further development? Advances such as the replacement of photographic emulsions by CCD detectors and the use of fibres for multi-object spectroscopy have produced gains of much more than an order of magnitude in observing efficiency. For applications which can utilise both of these advances, such as obtaining redshifts for large samples of faint galaxies, the AAT is now more than a thousand times more powerful than it was just ten years ago. It is difficult to foresee further gains coming on such a scale for optical spectroscopy. However, similar advances could now be attained in the near infrared, while there are many other areas where substantial gains should be realised within the next few years.
Purely on the instrumental side, these include still better CCDs; although peak quantum efficiencies are already 80% or greater, there is scope to extend such efficiencies to the UV and near-IR ends of the range, while the number of pixels per device is expected to increase by at least one more order of magnitude in the near future. Faster controllers and more clever ways of using CCDs are being developed. The efficiency of instruments can be enhanced by techniques such as adaptive optics, image slicing and greater use of optimised coatings on optics.
There is also room for improvement in overall observing efficiency, probably amounting to more than a factor of two. The AAT still suffers from seeing degradation within the dome or due to the telescope mirror and structure in some circumstances; regular monitoring of the internal and external seeing is pointing to ways in which this can be minimised by better control of the thermal environment, and shows that the seeing at the AAT can be sub-arcsecond for a substantial fraction of the time. To exploit this properly will require new modes of observing so that the best seeing is utilised for those observations which most need it; a mixture of service observing, remote eavesdropping and `queue scheduling' should be appropriate.
Plans for the future
The current, short-term and longer-term instrumentation plans of the AAO have been described previously in this Newsletter, in ACIAAT reports and elsewhere (most recently in my report to the ASA in 1994, now available as an AAO preprint) so I will not repeat the details here. Similarly, the Schmidt Telescope is not considered in detail here because the future of that facility has just been examined by the new Schmidt Telescope Panel; a summary of that body's first report to the AAT Board is given separately in this issue of the Newsletter. For the immediate future, the top priority task must be to commission the 2dF fully and to make sure that the complete system, including on-line data reduction, works reliably and at peak efficiency for a wide variety of programmes; this is likely to absorb a fair fraction of the Observatory's effort for more than another year. Other obvious developments, such as the introduction of larger format CCDs, are already in hand.
Once significant technical effort becomes available following the completion of 2dF, it will be possible to embark on some new instruments and to initiate design studies for others. Three specific proposals are already being considered; in the order in which they arose historically these are:
(i) a short camera for UCLES, enabling the whole optical spectrum to be covered at high dispersion in a single exposure; such a camera was included in the original UCLES specification but was dropped because of a shortage of funds and because no suitable detector was available at the time;
(ii) a replacement for the RGO Spectrograph at the Cassegrain focus, still the workhorse instrument on the AAT but now quite inefficient compared with modern spectrographs; one intriguing possibility here is to exploit the new `SPIRAL' fibre-optic concept of Keith Taylor and Ian Parry;
(iii) a successor to the IRIS infrared camera/spectrograph, to be built around the latest 1024 square Rockwell detectors with m pixels in place of the present device with a 128 square array of m pixels; it is not feasible simply to update the existing IRIS optics.
The choice between these options should be made primarily on scientific grounds, although practical considerations such as cost, staff effort and availability of key components will have to be taken into account. ACIAAT members will be canvassing community views in the next couple of months.
Turning to the longer term future, a crucial ingredient of any vision for the future of the AAO must be to retain the ability and flexibility to exploit new technologies and to follow up the most important and exciting astronomical leads. This means having a staff which is versatile, a budget which is not almost entirely committed to basic operating costs, and open-minded management. However, we cannot today set out optimal instrumentation plans for the years beyond 2000 with any likelihood of being correct, and it would be a mistake to commit the AAO too far in advance. Almost by definition, the visionary instruments five or more years from now will depend on the right combination of someone's bright idea, the latest technology and whatever astronomical questions are then at the cutting edge of the subject.
That said, we can make a list of several projects which may well include instruments which will be under construction, if not in use, at the AAT five years from now. These include an intermediate to high dispersion near-infrared spectrograph; an infrared version of 2dF for survey work; an adaptive optics system at the Cassegrain focus, possibly involving a deformable secondary mirror, again primarily for infrared work; an array of imaging CCDs on the Schmidt Telescope, and/or an array at the AAT prime focus; and the long-standing suggestion for a coudé auxiliary telescope. In choosing between these and other options, much will depend too on the actual performance and available instrumentation of the 8m class telescopes which will be operational by then; already we are seeing the impact of the 10m Keck Telescope on high signal-to-noise ratio, high resolution spectroscopy of faint objects, where some projects are no longer worth pursuing with UCLES on the AAT. However, the 8m telescopes will not do everything and will still be few in number; they will have to concentrate on doing those kinds of astronomy which simply cannot be done on smaller telescopes, or which require the extremely high spatial resolution which they promise to deliver. That will still leave an enormous amount of front-line work for well-instrumented and efficient 4m telescopes like the AAT. Russell Cannon
Flares with FLAIR
Classical T Tauri stars are young, low mass pre-main sequence stars, with a circumstellar accretion disk. For a long time it has been a mystery how these stars can keep their low rotation rates while accreting matter from the disk. Currently, the most popular model is that a magnetic field with a strength of about 1000 Gauss couples star and disk, so that angular momentum is transported outward, while matter is flowing inward. Since direct measurements of the fields are still rather sparse, evidence that strong magnetic fields are involved comes only from indirect arguments.
One very important argument for the presence of the fields is that the X-ray emission shows occasional rapid increases. The events were interpreted as flares, like flares on the sun (or in flare stars) but of enormous size. By using the observed temperatures and decay times, and assuming that the basic structure and mechanisms are the same as on the sun, a (minimum) magnetic field strength could be derived which was in good agreement with the magnetic model. From solar observations it is known that flares not only emit X-rays but also all kinds of radiation from radio waves up to gamma rays. Although the optical emission is a secondary effect, it is a necessary ingredient of a flare, and if the interpretation of the X-ray data is correct, optical flaring has to be observed. Since the optical emission comes from the footprints of the flaring loops, and the X-ray emission from the top, the detection or non detection of optical flares would tell us how closely the flares on classical T Tauri stars resemble flares on the sun, and thus if the use of scaled up solar models is justified at all.
Since rapid increases of the optical brightness of these stars have been known for a long time, the picture seemed to be rather consistent. However, the situation changed when broad band photometry showed that the colours of these events were much redder than flares seen in flare stars and on the sun. To make things worse, it became clear that accretion shocks on T Tauri stars would radiate in the soft X-ray regime and since some of this radiation might escape the shock region before being reprocessed to optical emission, the X-ray variation could, though this is relatively unlikely, also be due to variations of the accretion rate.
However, the question of whether the events seen in the optical are flares, or changes of the accretion rate, can in principle be easily solved. There is another class of T Tauri stars, the so called Weak-Line T Tauri stars, that closely resemble the Classical T Tauri stars, except that they lack accretion and a massive disk. Thus, any event seen in these stars has to be a flare. Additionally, any increases in the accretion rate can be easily distinguished from flares by their light curve, since flares have rapid increases and slow decreases, whereas changes of the accretion rate will lead to more symmetrical light curves. For further observations of such events it would be much better to take spectra, instead of broad band photometry, because flares have a prominent emission line spectrum (notably the Balmer lines). Progress in this field was severely hindered by the rarity of the events. On average, there is only one such event every 100 hours of monitoring, and a typical event last only about an hour. However, the multi-object spectrograph FLAIR on the UK Schmidt telescope allows one to take spectra of about 50 stars simultaneously. By placing some fibres onto non-variable stars in the field it is thus possible to even obtain a (rough) flux calibration of the spectra, making FLAIR nearly ideal for such a program.
Using FLAIR we were thus able to observe simultaneously 17 classical T Tauri stars , and 18 Weak-Line T Tauri stars in the Chamaeleon cluster. We chose the region, because this line is very prominent in flares. In just 3 nights, we obtained 548 hours of flare monitoring. Due to the relatively large brightness of these stars, the integration times were only 200s, which resulted in 5040 spectra of classical and Weak-Line T Tauri stars in total. We detected three clear events in the spectra of the Weak-Line T Tauri stars . Since these stars lack accretion these events have to be real flares, and indeed they showed the typical characteristics of flares: the rise times were of the order of 10 minutes, the decay times were of the order of an hour, and the increase in flux of was much stronger than that of the continuum. The left figure shows four spectra taken within 15 minutes of the rise times of flare. Although the continuum flux increased by 25%, the flux of increased by an impressive 320%! The figure on the right shows the lightcurve of the same event. As can easily be seen, the increase in equivalent width of is much faster than the decrease. Although a number of events were seen in the classical T Tauri stars as well, none of these shows the characteristic strong increase within minutes and decrease in an hour. It thus seems very plausible that the events in the classical T Tauri stars are due to accretion, not due to flares.
Figure: Left:Part of the spectrum during the rise time
of the flare. The spectra are flux calibrated
relative to standard star that were observed
simultaneously. The spectra are arbitrarily
shifted in the Y direction. Intensities above
500 counts are shaded to show the increase
in continuum flux by about 24%. However the
flux of increased by 320%.
Right: Equivalent width of of the Weak Line T Tauri star J1149.8-7850. The equivalent width changes within 15 minutes from about 0.5 Å to 5.5 Å and decreases slowly in about an hour.
Our first observing run with FLAIR thus clearly demonstrated that flares can be found with this instrument, and we actually obtained some of the very few spectra of such events that have ever been recorded. However, the results of this run somewhat deepens the mystery in that there are no, or at least very few, optical flares in classical T Tauri stars. Since we now know that flares can efficiently be detected in this way, the next logical step would be to investigate the properties of the flares and the accretion events, which are interesting by themselves. For example, observation of the higher Balmer lines including the Balmer jump would allow us to derive temperatures and optical densities for both types of events. We would, of course, also like to enhance the statistical basis of the data. Eike Guenther, Dept. of Physics, Queen Mary & Westfield College
Visitors to the AAO during this quarter included Adrian Fish, from UCL, who divided his time between the Epping Laboratory and the AAT. Ian Parry called by for a brief period to catch up with 2dF fibre progress, and Ishbel (not necessarily in that order). Adaptive optics experts Richard Myers, from the University of Durham, and Martyn Wells, from the University of Edinburgh, were hosted by the AAO and others on a two week visit. AO notes were discussed and compared. And Angela Cotera, from NASA, has returned for a two month visit until mid-June. Angela is working with Mike Burton on star formation in the galactic centre and analysing IRIS data.
Gary Da Costa was properly farewelled in March, BBQ-style, and presented with two of his favourite David Malin photographs, nicely framed. These will grace his office at MSSSO. Barry Croke ended a six week visit by giving a ``snapshot of Crete'' in an entertaining slide show. Barry is currently working with Despina Hatzidimitriou at the University of Crete, and continues to collaborate with Russell Cannon. A few days later Jeremy Bailey was persuaded to share his travels through several South African National Parks ``on safari'', and staff enjoyed another exciting lunchtime slide show. As usual the AAO put on good weather for the AAT Board BBQ at Epping which traditionally marks the culmination of Board meetings.
Finally, it was good to see Ann Savage at the Epping Laboratory albeit briefly, during a recent visit to Sydney. Ann has been working from home as she is on extended sick leave. Annette Callow
Letter From Coonabarabran
Heigh ho -- here we go with the drought again. It would seem the rain of January was just a aberration -- el nino is in full stride again and there has been nothing since. Once again the farming-types wear long faces and observers bounce along on jubilant feet but being generally good-mannered they try not to gloat too much. There have been the odd nights of cloud, but none of them actually did anything -- the feeling is, if it is going to be cloudy it might as well do something useful, like rain. But, oh the seeing..... It has been wonderful -- that is, when it hasn't been awful!
The Board of course made their annual pilgramage during more superb weather and mixed with the staff at the usual luncheon.
Chris McCowage has left the balmy clime of La Palma and is with us again. The hair is a little greyer than when he left -- probably due to the altitude -- but otherwise he is just the same. Welcome back Chris.
The 2dF spectrographs are coming along nicely as evidenced by odd metallic shapes lying all over the place, looking oddly like a Dalek battlefield. Things are coming together and these pieces, which we still expect to start screaming ``Exterminate! Exterminate!'', are the results of a great deal of hard work.
Another exciting event is the work being done by the Sydney University team of John O'Byrne, Julia Bryant and Robert Minard on adaptive optics for IRIS. I am sure that eventually the bewildering array of optical elements, beam splitters and other bits and pieces will eventually come together in another wonderful success.
One unusual happening was the visit by an Army pipe band to the Telescope. Although in fatigues and not kilts, they gave a short concert in the dome which was interesting, given the acoustics, but a lot of fun. They were also interested in the telescope which was good.
Sir John Maddox of ``Nature'' magazine was also a very welcome visitor. Rhonda Martin
The Report of the Schmidt Telescope Panel (STP)
The newly established STP met for the first time during the week beginning 6 February 1995, at Siding Spring. The Panel's primary task was to generate a report to the AAT Board, exploring options for the future scientific use of the UKST and making recommendations on their relative priorities. The bi-national Panel consisted of Chris Collins, Paul Hewett and David Morgan on the UK side; Malc Hartley, Dick Hunstead and John Norris on the Australian side; and Russell Cannon as Chair, with David Malin as an additional co-opted member.
The three main photographic sky surveys currently being carried out on the UKST (Equatorial R-band, Southern Second Epoch R-band and all-sky I-band) should all be substantially complete in about two years. This opens up an opportunity for a major change in the utilisation of the UKST from 1997 onwards. The principal recommendation of the STP is that the UKST should then start to undertake relatively large projects which require substantial numbers of photographic exposures in very good observing conditions. Such projects, for example multi-colour surveys of selected regions or deep mini-surveys involving addition of many exposures, have always taken second priority to the main sky surveys since the UKST was commissioned in 1973; few large non-survey programmes have been satisfactorily completed and the full astronomical potential of the Schmidt has not been fully realised. However, operating the UKST is an expensive and labour-intensive task. Thus all projects carried out on the telescope will have to be of the highest scientific priority; there is no question of `looking for projects to do'. Rather, if the proposals received are not judged to be of high enough calibre, it will be better to operate the UKST on fewer nights per year and to deploy the AAO's resources on other more important projects. The STP will be rigorous in its assessment of all proposals received.
It may seem surprising that the Panel's main recommendation is a continuation of photographic work. The option of fitting the UKST with an array of CCDs was also considered very seriously; this will be studied further and may yet be the best option at a later stage. However, at present the very large format and high spatial resolution of photographic emulsions, especially the Kodak Tech Pan film whose merits have been extolled in previous issues of this Newsletter, still outstrip the greater quantum efficiency of CCDs for wide field work. Taken together with the fast measuring machines in the UK, APM and the new SuperCOSMOS, the UKST represents the world's most powerful facility for deep, large area sky surveys; the UK and Australian astronomical communities should endeavour to build on the lead they have established in this type of astronomy. The Panel has asked the AAO to play a greater role in liaising between astronomers and the measuring machine teams, to ensure smooth access to the machines for new users and the efficient exploitation of existing digitised sky survey databases. A major specific use of the UKST in the next few years will be to support 2dF spectroscopic survey projects, both in the selection of targets and in the generation of astrometric input positions.
The STP envisages that FLAIR multi-object spectroscopy will continue to take up about a quarter to a third of the observing time on the UKST, as at present. Interestingly, this facility has recently found increasing use internationally, as much as from Australian and British astronomers. FLAIR was designed so that it is easy to switch between fibre spectroscopy and standard direct photographic work during the course of each night. This means that the UKST can be used very efficiently, switching between photography in good seeing and spectroscopy in poorer seeing, given that the standard FLAIR fibres are nearly seven arcseconds in diameter. It has sometimes been suggested that FLAIR will be superseded when 2dF enters service on the AAT, but equally it can be argued that the two facilities will be complementary, since FLAIR is ideally matched to objects brighter than about magnitude 18 occurring at the rate of a few per square degree, while 2dF is aimed at fainter targets at around a hundred per square degree. One possible project for FLAIR could be to undertake a systematic redshift survey for all southern galaxies down to B = 17.5; the Panel would welcome a full scientific case for carrying out such a survey.
The STP did not think there was a strong case for embarking on any new broad-band photographic sky surveys at present. However, it did consider one proposal, for a narrow-band H survey of the Galactic Plane and Magellanic Clouds. The two essential features of this new survey are to utilise Tech Pan film, which has peak sensitivity at H and much higher spatial resolution than the emulsions used by John Meaburn and his colleagues for H work in the 1970s, and to use an `objective' filter. The latter will consist of a 1.2m diameter mosaic of interference filters, to be mounted at the top of the telescope in front of the Schmidt corrector plate. Such a filter can have a narrower bandwidth and should give better imaging quality than the more conventional near-focus filters, two features which will both lead to detection of fainter emission nebulosity. The Panel ranked the scientific aims of this survey very highly and encouraged the proposers and the AAO to press ahead with a design study for the filter. Two incidental advantages of this survey are that it will be concentrated in those parts of the sky where there is little other demand for Schmidt data, especially near the Galactic Centre in the RA range from 14 to 21 hours, and that it can be done in grey time, again resulting in high observing efficiency.
The Report of the Panel was dicussed by the AAT Board at its meeting at the end of March; all of the recommendations were accepted. Copies of the full Schmidt Telescope Panel Report are available from the AAO on request. Russell Cannon
Two new Schmidt appointments will commence soon. Dionne James starts on May 8 as a technical assistant. Dionne comes from Creswick in Victoria and has previously worked in a CSIRO laboratory. She will be working with Paul Cass for the first few months, mostly in the plate and film copying areas. Fred Watson starts on August 1 as the Astronomer in Charge. Fred was based at the Schmidt between 1981 and 1992 and during this time he built FLAIR I and II (with a little help from Durham University, the AAO and the ANU). As well as FLAIR, Fred has numerous other claims to fame ranging from his amazing capacity to remain wide awake during his observing runs, especially around 2am, to his propensity to consume substantial amounts of ginger slice, an activity with which the rest of us are keen to assist. Malc Hartley
UCLES & UHRF update
UHRF observers will notice significant improvements in the control of UHRF. It has been integrated with UCLES under VAX software, and is controlled through UCLES-like commands and configuration files. The new system is not only easier to operate and faster to execute, but also permits rapid changeover between UCLES and UHRF so that both instruments can be used in a night (with separate CCDs) with at worst a few minutes downtime. The only changes required are moving the acquisition TV and activating the correct CCD shutter. The CCD dewars can be filled remotely, so the coude room need not be disturbed for periods up to 3 days, increasing instrument stability and reducing dark counts caused by fluorescence. A new instrument manual is being finished, and should be ready for distribution by the time this Newsletter hits the press. UHRF observers should use the following data to estimate count rates. The second column gives the magnitude of the star yielding 100 e/s/0.01Å at an airmass of 1.5 in median (1.8") seeing, with the Tek CCD and image slicer.
Table 0.1: UHRF Countrates
Adrian Fish, Ed Penny, Sean Ryan, Keith Shortridge, Darren Stafford
Efficiency Estimates for the RGO
I have calculated efficiencies for a range of setups of the RGO with the Tektronix CCD, to aid preparation of observing proposals. If your setup differs greatly from those given, ask me for an estimate (email: rl).
All calculations are for the 25cm camera of the RGO, with the Tektronix 1K CCD at 170K. The observation is assumed to be on a grey night, at 30 degrees zenith distance, with a 2 arcsec slit width, 2 arcsec seeing and 4 pixel extraction in the spatial direction, with unbinned pixels. Vignetting in the 25cm camera has been included. To convert to other settings see Section 6.3 and Appendix B in the Observers' Guide. The calculations are done for low dispersion (250B or 270R grating), medium dispersion (600V or R) and high dispersion (1200B, V or R). The dispersions are approximately 0.79 Å/pix with 1200 line gratings, 1.6 Å/pix with 600 line gratings, 3.1 Å/pix with the 270R and 3.4 Å/pix with the 250B.
I have made the calculations at 4400 Å for a B=15 star, 5500 Å for a V=15 star, 6400 Å for an R=15 star and 8000 Å for an I=15 star. It is therefore easy to convert the countrates to the brightness of your object in the band nearest to your observations. Don't forget to allow for slit losses for resolved objects. For observations with AUTOFIB, multiply the object countrates by 0.37 and sky by 0.53.
Expected Countrates (photons/second/pixel)
Readout noise attained with the Tektronix varies with the choice of readout speed: XTRASLOW 2.3e; SLOW 3.6e; NORMAL 4.8e; FAST 7.2e; NONASTRO 11e. XTRASLOW takes about 3 mins to read out for the full slit, and SLOW takes about 1 min. With a narrow (60 pixels) window, readout is around 20 sec with SLOW.
To calculate the expected signal to noise ratio (S/N) per pixel, use:
where O = counts per pix for the object, S = counts per pix for the sky and is the square of the readout noise times the number of spatial pixels extracted (4 for the above calculation, 6 for AUTOFIB) times the number of exposures to be summed. Raylee Stathakis
Archive and Database Resources at AAO
The COSMOS/UKST Southern Sky Object Catalogue
The COSMOS catalogue lists parameters of images detected on the survey plates rather than the actual plate images and may be used to generate image lists or ``pseudo'' finding charts for selected fields. It is now available on-line via a public computer account: to use it, do ``telnet cosmos.aao.gov.au'' then give ``cosmos'' as the username, and also as the password. You must first register your institute with us: instructions and more information are available on the AAO WWW homepage under ``COSMOS'' or send an request by email to firstname.lastname@example.org. The COSMOS catalogue has the advantage that data from many different fields can be accessed in a fast and efficient way, but please note that the images have been separated and classified by automated algorithms which are not always reliable. For instance, some objects classified by COSMOS as galaxies are in fact double images. Michael Drinkwater
The Digitised Sky Survey on CD Rom
The full sky is now available on CD Rom, on the STSCI Digitised Sky Survey (DSS). The pixel scale is 1.7 arcsec square. Crowded regions such as the galactic plane and the Magellenic Clouds are included, though these fields are not as deep. There are 102 CD Roms. The first 61 (the blue box) cover --90 to +3 degrees, stored 6 per box, and the final 41 (the red box) cover the northern half of the sky, stored 4 per box. More information is available in a booklet kept with CD Rom 102. See the previous article for a discussion of the quality of the data.
We have sets at Epping in the Computer User Room, and at the AAT in the control room. The set at site is meant primarily as a resource for the current observer, though with the observer's permission it can also be used in the user room or at the Schmidt. Please make sure in this case that you return the CD Roms promptly. For help ask me or Steve Lee at the AAT.
At present we offer the default software, getimage, which is very simple to use but which does not produce a coordinate axis. To run, just type `getimage'. The input requires a label of up to 4 digits, followed by RA and Dec (J2000) in free format, and the width and height of the field required in arcminutes. Exit using ctrl--d. A useful qualifier is `getimage --b', which allows input in B1950 coordinates. A list of other qualifiers can be obtained by typing `getimage --h' or by copying the readme.txt file from /cdrom/software/getimage on CD 102. In this case you will need to `Mount' and `Umount' the CD (note the case). Options exist for entering a file of positions to run in batch mode.
The output is by default a standard FITS file which can be easily displayed using SAOimage or XV_FITS for example. The output can also be set to create a GEIS image or header (extension.hhh). Astrometric details are contained in the FITS header. Please avoid unnecessary printing of images as they are large and take typically half an hour to print out. This is the main reason for locating the site copy in the control room so that field can be accessed in real time on the screen.
Note that the data set is available on XMOSAIC in SKYVIEW, which can be accessed through the AAO home page.
The plate digitiser at the AAO has for some time been out of commission due to a hardware failure in CAMAC. This has now been fixed, so the machine is available. However note that there are continuing problems which have not been addressed as yet due to lack of time. The software is not robust, and some modes do not work, and the calibration of the PDS has not been tested since its resurrection. However if anyone has an urgent project and is willing to make the necessary calibrations, and will put up with the software limitations, the PDS is available so contact me if you are interested.
Plate and Film Material
Survey films and plates are still available at Epping in the chart room on the ground floor, on the first floor of the AAT, and at the Schmidt. If you have queries or need help with the Epping resources contact me (email rl). Raylee Stathakis
Cosmic Ray Removal
I have developed a FIGARO program called CLEAN2 to remove cosmic rays from spectroscopic data. CLEAN2 is now ready for release, and runs under both the VAX and UNIX versions of FIGARO. The program, a help file and a copy of a paper submitted to PASP are available through anonymous ftp (aaoepp.aao.gov.au). The files are in the subdirectory /bfc/cosmic--ray. See the README file in this directory for details.
CLEAN2 attempts to remove cosmic rays from a pair of images taken with long slit, echelle or fibre fed spectrographs. The program may be able to handle direct images but this has not been tested. The main advantage of this code is that it only requires 2 images, instead of the minimum 3 images required for median programs such as MEDSKY. The program is also able to match the two frames more accurately by allowing for variations such as seeing and fibre throughput. CLEAN2 can run in interactive mode, or once the parameters have been optimised the program can be run in batch. CLEAN2 will be released in standard FIGARO in due course.
Any questions about using the program at Epping or Siding Spring should be directed to Keith Shortridge (email@example.com) or Raylee Stathakis (firstname.lastname@example.org). Any questions about the program itself should be sent to email@example.com Barry Croke
The second international conference of Library and Information Services in Astronomy (LISA II) will be held at the European Southern Observatory from May 10 to 12, 1995. The AAO librarian has been on the scientific organising committee for this meeting which has been in the planning stages for nearly two years. Since the first meeting held in Washington in 1988 much has changed in the provision of information. It is important that astronomy librarians meet to discuss the application of the new technology. Information is now being ``packaged'' in new and innovative ways. Access to the variety of online services available is more of a challenge than ever. Problems associated with storage, archiving and copyright of electronic information need to be solved. These and many other topics will be part of the ``hands-on'' style of workshop at the LISA II meeting. The AAO librarian has been fortunate to be awarded a grant from the Australian Department of Information, Science and Technology to enable her to attend the meeting in Germany. This grant is specifically for the promotion of the newly released multi-lingual supplement to The Astronomy Thesaurus which was published last October. The thesaurus and the new supplement are of direct relevance to librarians in the successful documentation and retrieval of information in astronomy. Many European librarians have their library databases in their own language or have to assign keywords in their own language to their library records. Librarians in other parts of the world do not have the multi-lingual skills of their European colleagues and therefore will benefit from a reference resource which will enable them to catalogue foreign literature, both historical and current.
The multi-lingual supplement in French, German, Italian and Spanish is now available as an ftp file or from the AAO Homepage on the World Wide Web. Thanks are due to all involved in the compilation of the supplement which will considerably enhance the main thesaurus and the standardisation of terminology in astronomy internationally.
For more information about the thesaurus and the supplement please contact the AAO Librarian.
Robyn Shobbrook (E-mail: LIB)
New AAO Preprints
The following AAO preprints have been distributed April 1995, and are available upon request from the AAO librarian.
Bland-Hawthorn, J., Ekers, R.D., Van Breugel, W., Koekemoer, A., Taylor, K. ``Extragalactic ionized hydrogen in the Fornax Cluster'', AAO PP 282-95. ApJ
Da Costa, G.S., Armandroff, T.E. ``Abundances and kinematics of the globular cluster systems of the Galaxy and of the Sagittarius dwarf'', AAO PP 283. AJ
Chapman, J.M., Habing, H.J., Killeen, N.E.B. ``Radio observations of Mira variables, OH-IR stars and M-Supergiants'', AAO PP 284-95. ASP Conf. Series - Invited Review
Lumsden, S.L., Puxley, P.J. ``Forbidden Fe+ emission from supernovae remnants in M33'', AAO PP 285. MNRAS
Cannon, R.D. ``Instrumentation plans at the A.A.O.: 2dF and beyond'', AAO PP 286. Proc. ASA
Ryan, S.G., Lambert, D.L. ``The Demise of the metal poor disk ?: Spectroscopic iron abundances'', AAO PP 287. AJ
Heisler, C.A., Vader, J.P. ``Galaxies with spectral energy distributions peaking near 60 m: III H Imaging'', AAO PP 288. AJ
Ryan, S.G., Deliyannis, C.P. ``Lithium in short period tidally locked binaries: A test of rotationally induced mixing'', AAP PP 289. ApJ
New Chair for the AAT Board
At its meeting in March the AAT Board appointed Professor Lawrence Cram, of University of Sydney, as Chair. He replaces Professor Michael Rowan-Robinson of Imperial College, who has chaired the Board since 1993, whose term concludes on 30 June. Professor Cram's appointment commences on 1 May 1995. Professor Richard Ellis, University of Cambridge, commences as Deputy Chair from 1 May. Sandra Harrison
AAO POST DOCTORAL RESEARCH FELLOWSHIP
The Australian Research Council and the UK Particle Physics and Astronomy Research Council jointly fund a Research Fellowship tenable for up to two years at the Anglo-Australian Observatory (AAO). Applications are now sought for a Research Fellow, to fill a position available from 1 January, 1996. The position will be based at the Epping Laboratory, in Sydney.
The recipient of the fellowship will be free to conduct their own research program, and the appointee will be expected to participate in the operation of the Observatory by performing duties such as supporting visiting astronomers. The Fellowship salary will be in the range $A37,345 to $40,087 p.a., depending on research experience. Reasonable relocation expenses including airfare to Australia (and return on completion of the appointment) will be paid. Closing date 15 June, 1995.
Further information about the Fellowship and the full text of the advertisment can be obtained from the AAO homepage, or from: David Malin, Phone +61 2 372 4867: Fax +61 2 372 4860 or e-mail: firstname.lastname@example.org.
The Anglo-Australian Observatory is an Equal Opportunity Employer. David Malin
1988mm Septmm Darkmm Grey(1)m
Dark Grey (1) Bright Grey(3) Dark
1995 Jan 1--5 6--9 10--22 23--25 27--28
Feb 1--7 9--11 12--23 24--26 27--31
Mar 1--5 6--9 10--20 21--24 25--30
Apr 1--5 6--8 9--19 20--23 24--31
Jun 1--3 4--7 8--18 19--21 22--30
Jul 1--2 3--6 7--17 18--21 22--31
Editor: Stuart Lumsden
Editorial assistant: Robyn Shobbrook
Published by Anglo--Australian Observatory, PO Box 296 Epping, NSW 2121 Australia