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"Representative" spectra for the JCMT
"Representative" Spectra for the JCMT Heterodyne Receivers

To view available spectra, pick a receiver/frequency:

  • A3 (211-276 GHz)
  • B3 (315-369 GHz)
  • W/C-band (430-510 GHz)
  • W/D-band (625-710 GHz)

    Notes  

    The JCMT's current suite of receivers for spectral line observing, locally named A3, B3, and W, have been around a while now. A3 replaced the receiver A2 for the 211--276-GHz window, in 1997 B3 replaced B3i (whose predecessors were B2 and B1) and W replaced C2 for the 430-505 GHz region ("C-band"), and also gave the JCMT capability in the "D-band", from 630 to 710 GHz. Over a period of time "standard spectra" will become available, against which the performance and calibration of the receivers can be judged on any given day. So far, however, insufficient spectra have been obtained to make such tabulations for the less common lines. For the time being, "representative" spectra are offered in the tables below. As time goes by, it is hoped to fill in a reasonable number of the empty spaces.

    Seeing the data

    Where such spectra exist the fact is indicated by a tick here. Clicking on this symbol shows the corresponding spectrum. Lines that are rather weak for use as eventual standards are indicated as "weak", or "v. weak" or "no line" if not useful as such under any circumstances, although the data can be seen by clicking on the descriptor. "no data" means that no data exist in our database for this particular frequency/source combination. "emb'd" (i.e. embargoed) means the data have been taken in a PATT program, but are currently not released for general use. I have tried to avoid having any empty spaces, although I have not completely succeeded.

    Spectra are color-coded:

    • For receiver A3 plots in green are obtained in upper sideband, while those plotted in red are taken in lower sideband. Please note that an LO fault can lead to an incorrect tuning for the C18O 2-1 line at 219.56 GHz in the normally preferred lower sideband; upper sideband is indicated in this case. All data taken with A3 are double-sideband; sometimes other lines are present depending on the sideband used. There are usually slight differences in the strengths of lines in the two sidebands; with the present mixer this effect is acute near the "hump" around 250-260 GHz. In particular one should use USB for CS 5-4 and LSB for HCN and HCO+ 3-2 to obtain reasonable calibration.
    • For receivers B3 and W plots in green are obtained using channel A, while those plotted in red are obtained with channel B. Only one channel may be represented. All spectra taken with B3 and W are single-sideband.

    In addition A3 spectra may be compared with those for A2, and W/C-band spectra with those for C2. There are no comparable data for W/D-band.


    Back to top of page or to A3, B3, W/C-band, or W/D-band

    Receiver A3 -- Representative Spectra
    Note - A3 is a double-sideband receiver; i.e. in any given spectrum it will detect lines from the signal sideband and also those which happen to lie in the image sideband centered 8 GHz away. Where possible, spectra in this table show the results of observing with the receiver tuned to place the line in the Upper sideband (plotted in green) and in the Lower sideband (in red). Line strengths may be different in the two sidebands.
    Species H2CO C18O 13CO CO CH3OH CS HCN HCO+ HNC H13CO+
    Transition 303-202 2-1 2-1 2-1 50-40A 5-4 3-2 3-2 3-2 3-2
    Frequency 218.222 219.560 220.398 230.538 241.791 244.935 265.886 267.557 271.981 260.255
    W3(OH) spectrum always use USB spectrum spectrum spectrum spectrum spectrum spectrum spectrum spectrum
    L1551-IRS spectrum use USB spectrum spectrum no line weak spectrum spectrum HNC 3-2
    CRL618 v.weak v.weak spectrum spectrum no line v.weak spectrum spectrum spectrum
    OMC1 spectrum Always use USB; LSB suspect spectrum spectrum spectrum spectrum spectrum spectrum spectrum
    N2071IR spectrum use USB spectrum spectrum spectrum spectrum spectrum spectrum spectrum spectrum
    OH231.8 no line no line spectrum spectrum no line weak spectrum line is probably SO2, not HCO+ spectrum
    IRC10216 no line weak; always use USB spectrum spectrum no line spectrum spectrum no line spectrum
    16293-2422 spectrum use USB spectrum spectrum weak spectrum use LSB use LSB spectrum spectrum
    NGC6334I LSB data only A2 LSB spectrum; no useful A3 spectra; must use USB for A3 USB; no LSB comparison LSB/USB data from different epochs this is LSB and therefore suspect; use USB to avoid hump use USB to avoid hump use LSB use LSB use USB
    G34.3 spectrum use USB spectrum spectrum spectrum spectrum spectrum spectrum spectrum spectrum
    W75N spectrum use USB spectrum spectrum spectrum spectrum spectrum spectrum spectrum spectrum
    CRL2688 no line v.weak spectrum spectrum no line spectrum spectrum no line spectrum
    NGC7027 no line v.weak spectrum a little lower than expected no line no line use LSB use LSB no line
    N7538IRS1 spectrum use USB spectrum spectrum spectrum spectrum spectrum spectrum
    		spectrum spectrum


    Back to top of page or to A3, W/C-band or W/D-band

    Receiver B3 -- "Representative" Spectra

    Reminder: B3 is a dual-channel receiver; i.e. it is capable of observing line radiation in orthogonal polarizations. Spectra are plotted with channel A shown in green, and channel B in red. All spectra shown have been obtained in single-sideband mode, except for those for which no B3 spectrum could be found and an earlier result is used.
    Species C18O 13CO CH3OH CS CO HCN HCO+ H2CO
    Transition 3-2 3-2 70-60A 7-6 3-2 4-3 4-3 505-404
    Frequency 329.331 330.587 338.410 342.883 345.796 354.506 356.734 362.736
    W3(OH) spectrum spectrum spectrum spectrum spectrum spectrum spectrum spectrum
    L1551-IRS spectrum spectrum no data weak spectrum weak good weak
    CRL618 v. weak spectrum no line* weak spectrum spectrum spectrum no line*
    OMC1 good no baselevel fitted baselevel subtracted baselevel subtracted spectrum OK OK OK
    N2071IR spectrum OK OK spectrum spectrum spectrum spectrum OK
    OH231.8 v. weak single channel older data no line weak spectrum spectrum spectrum no line*
    IRC10216 weak spectrum no line* spectrum spectrum spectrum no line* no line1
    16293-2422 spectrum spectrum good good spectrum good good good
    NGC6334I B3i; one channel only good no data good spectrum spectrum channels have unequal line strengths good
    G34.3 spectrum spectrum good good spectrum spectrum spectrum channel B poor
    W75N good good good a bit ratty spectrum good spectrum older AOSC data
    CRL2688 no data good no line good good good no line no line*
    NGC7027 no line B3i data no line no line in this target; should be at 26 km/s spectrum older data spectrum no data
    N7538IRS1 spectrum spectrum spectrum spectrum spectrum spectrum spectrum no line?

    * Target line not present, but other lines appear in the signal band.

    Additional Notes
    (1) Bright line near middle is HCN 4-3 in LSB (suppressed image sideband); double-peaked line is HNC 4-3 in signal band (USB).



    Back to top of page or to A3, B3, or W/D-band

    Receiver W/C-band -- Representative Spectra

    Note: W is a dual-channel receiver; i.e. it is capable of observing line radiation in orthogonal polarizations in both of its wavebands (C- and D-band; see below for D-band data). For W spectra are plotted with channel A shown in green, and channel B in red. All spectra shown have been obtained in single-sideband mode.
    Species C34S H2CO C18O 13CO H2S CO HDO CS C-atom
    Transition 9-8 606-505 4-3 4-3 111-000 4-3 101-000 10-9 3P1-3P0
    Frequency 433.751 434.493 439.089 440.765 452.390 461.041 464.924 489.751 492.161
    W3(OH) no data no data no data no data no data spectrum spectrum emb'd single channel only
    L1551-IRS no data no data no data no data no data single channel only no data no data no data
    CRL618 no data no data no data no data no data single channel only no data no data no data
    OMC1 no data no data spectrum spectrum spectrum single channel only spectrum only data are from C2/DAS CI is small line in middle
    N2071IR no data no data spectrum spectrum spectrum spectrum weak no data RxC2 only; no W/C data
    OH231.8 no data no data no data spectrum spectrum early test data no data no data no data
    IRC10216 spectrum no data no data no data no line spectrum no line weak? C2/DAS v.weak; no W/C data - C2 data only
    16293-2422 no data no data no data no data emb'd spectrum spectrum no data 28-Jul-01 OK
    NGC6334I no data no data no data no data no data spectrum C2/AOSC - old data no data 28-Jul-01 OK
    G34.3 no data no data no data no data no data spectrum only one channel working emb'd DAS having trouble
    W75N no data no data no data no data no data spectrum single channel only single channel only 22-Oct-01 OK
    CRL2688 no data no data no data no data no data C2/AOSC - no modern data no line no data v.weak
    NGC7027 no data no data no data no data no data spectrum no line no data weak
    N7538IRS1 no data no data no data very poor data no data single channel only weak line; single channel only C2/DAS; poor data one channel only


    Back to top of page or to A3, B3, or W/C-band

    Receiver W/D-band -- Representative Spectra

    Note: W is a dual-channel receiver; i.e. it is capable of observing line radiation in orthogonal polarizations in both of its wavebands (C- and D-band; see above for C-band data). For W spectra are plotted with channel A shown in green, and channel B in red. All spectra shown have been obtained in single-sideband mode.
    Species HCO+ CS H2CO C18O 13CO SO2 CO HCN HCO+
    Transition 7-6 13-12 909-808 6-5 6-5 660-551 6-5 8-7 8-7
    Frequency 624.087 636.532 647.082 658.553 661.067 676.484 691.473 708.877 713.342
    W3(OH) no data no line no data channel A was nbg no data spectrum no data no data
    L1551-IRS no data no data no data no data no data no data Aug 1998 - channel A suspect no data no data
    CRL618 no data no data no data no data no data no data no line seen no data no data
    OMC1 no data spectrum spectrum spectrum spectrum no data spectrum spectrum no data
    N2071IR no data no data no data no data poor baseline no data intensity scale uncertain no data no data
    OH231.8 no data no line no data no data no data no data weak; only one good channel no data no data
    IRC10216 no data spectrum no data spectrum spectrum no data spectrum no data no data
    16293-2422 no data no data no data no data no data no data spectrum no data no data
    NGC6334I no data no data no data no data no data no data spectrum no data no data
    G34.3 no data no data no data no data no data no data one channel only no data no data
    W75N no data one channel only; ratty no data no data no data no data one channel only one channel only no data
    CRL2688 no data no data no data no data no data no data one channel only no data no data
    NGC7027 no data no data no data no data no data no data one channel only no data no data
    N7538IRS1 no data no line no data no data no data no data channels not equal no data no data

    A3, B3, W/C-band, or W/D-band

Contact: Per Friberg. Updated: Mon Dec 31 11:58:54 HST 2007

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