The figures below show the results of CO(2-1) observations of the standard sources CRL2688, CRL618, and IRC+10216, which most often are used to check the performance of the JCMT. Left is the integrated intensity and right the peak antenna temperature (only for 1000 MHz because the ORAC-DR output file log.standard currently lists the highest noise peak in the recipe REDUCE_STANDARD). Observations made in good weather (tau<0.12) are indicated in blue; those made in worse conditions are indicated in red.
Clicking on any of the plots shows the results distinguishing nighttime and daytime observations (for all tau values); daytime observations are indicated in red.
During several periods (20120413 – 20121201, 20140508 – 20150605, and 20170407 – 20170810) the alignment of RxA3 and the TMU (tertiary mirror) was faulty and intensities were lower than expected. This was traced back to a missing part which caused RxA3 to move after being reinstalled in the receiver cabin following maintenance work. An additional alignment issue was corrected on 20180312.
On 20160101 the mixer of RxA3 was replaced and the receiver was renamed RxA3m. The calibration of this receiver differs from RxA3 and is sideband dependent. See here (investigation of the calibration of RxA3m is ongoing).
The table below contains the average spectra of all good quality observations obtained between April 2007 and December 2015 using RxA3 (before the change of the mixer). Good quality means line temperatures which are internally consistent and also consistent with RxA3/DAS data (if existing), and with good baselines. The spectra were added with ORACDR (using the narrowline or broadline recipe. In the narrowline (broadline) recipe a second (first) order baseline is subtracted.For the moment only 250 and 1000 MHz bandwidth spectra are shown (resolution 30 and 488 kHz).The numbers in brackets are the peak TA* of the strongest line in the spectrum (an asterisk indicates cases where this is not the line mentioned in the table) and number of observations existing for the particular combination. All spectra show identifications of lines in the band (signal sideband in blue and image sideband in red. For 13CO(2-1) the normally used ‘best’ sideband was changed from USB to LSB in 2014. Spectra obtained with USB tuning are indicated in red; those obtained with LSB tuning in blue. Because RxA3 and RxA3m showed a sideband ratio different from one, both spectra show different line intensities. We are currently determining correction factors for the sideband ratios to be applied to RxA3(m) data.
The identified lines are those which are listed in JCMTOT (and therefore in SPLAT).
The sdf files with the spectra are available on request.
