AAO Newsletter October 1996 - Page 9


motion stars should we wish to work in the magnitude range 14 < mR< 16. The colour information is available from the APM Catalogues, but the range of colours should be checked for each field because the value of the colour limit can vary.

Summary
The good news is that for recent plates (up to 5 years old, corresponding to 90 mas/y) there is no problem choosing 2dF guide stars. In the magnitude ranges of interest (11 < mR < 16) l% or less of the stars move, well below the limit discussed above.


At the 30 mas/y level (15 year old plates) the number of fainter (13 < mR < 16) stars moving ranges from 3-9% which could represent a problem (only 95% chance of success). However this can be resolved by selecting stars bluer than BJ < R = 1.0 in which case less than 5% move, satisfying the 2dF requirements.

Michael Drinkwater (UNSW), Jaideep Barot (Durham) & Mike Irwin (RGO)


[SIII]lambda9069 imaging of galaxies

In September, the TTF was used to carry out line imaging of galaxies in the R and I  bands. The conditions were mostly photometric with seeing in the range 0."6 to 0."8. We have succeeded in detecting at optical wavelengths the radio counter lobe in NGC 1068 in the [S III] line. The observations show that the disk becomes transparent in the I band, allowing us to see line emitting structures projected below.




Figure 7: TTF chargeshuffle tunable imaging of the luminous far-infrared galaxy NGC 7130 in the emission lines of Halpha (top L), [N II] lambda6583 (top R), [S II]lambda6727 (bottom L) and [S III]lambda9069 (bottom R). Exposure times were set at 7 mins, except for the I  band line where we used 10 mins. The field of view is 44" or 14.0 kpc at the redshift of the object. Regions of star formation are clearly delineated along spiral arms.






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