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SCUBA Secondary Calibrators: 2003-2003
Secondary Calibrators for SCUBA: 2002-2003
THIS AN OLD VERSION OF THIS DOCUMENT. The updated version can be found here.
The
primary flux calibration of SCUBA data is based on the planets Mars, Uranus and Neptune, but at some times of the year these may be unavailable.
A (very) small set of 'secondary' calibators was extracted from those used
by Sandell (1994, MNRAS, 271, 75) that were
considered at the time to be compact, non-variable,
and located in regions free from confusing background emission.
HL Tau was added because it is also
unresolved and isolated - i.e. it has no surrounding cloud emission,
although there
is low-lying extended emission - and
IRC+10216 and
16293-2422 were added to cover
the RA range 09 - 17 hours, although
IRC+10216 is variable, and
both have peculiarities that
need specific chopping arrangements to overcome. (Click on the
individual links for further details.) The results below are otherwise
obtained using azimuth chop throws of 60" for the photometry and
120" for the maps.
Table
SCUBA Secondary Calibrators
(Fluxes in Jy/beam or Jy/aperture1)
Calibrator
RA
(J2000)
Dec |
Photometry &
64-point jiggle maps |
|
Pointing
maps |
Photometry |
| 850um |
450um |
Method 1 |
|
850um |
1350um |
|
|
|
|
|
|
|
HL Tau
04h 31m 38.4s
+18o 13 59.
| 2.32
± 0.11(8) |
10.4
± 1.4(6) |
Phot |
|
|
0.84
± 0.04 (3)* |
2.34
± 0.15(13) |
9.7
± 1.1(13) |
Maps |
|
2.28
± 0.15 (25)* |
|
2.36
± 0.24(287) |
9.9
± 2.0(83) |
INT |
|
|
|
|
|
|
|
|
|
|
CRL618
04h 42m 53.597s
+36o 06 53.65 |
4.57
± 0.21(24) |
11.9
± 1.9(22) |
Phot |
|
|
2.49
± 0.11 (7) |
4.56
± 0.17(25) |
11.2
± 1.4(18) |
Maps |
|
4.67
± 0.32(28) |
|
4.69
± 0.37(1445) |
12.1
± 2.2(398) |
INT |
|
|
|
|
|
|
|
|
|
|
OH231.8
2
07h 42m 16.939s
-14o 42 49.05 |
2.52
± 0.07 (6) |
10.53
± 1.14 (4) |
Phot |
|
|
0.80
± 0.03 (3)* |
2.43
± 0.03 (6) |
10.70
± 1.14 (4) |
Maps |
|
2.46
± 0.17 (10) |
|
2.75
± 0.44(272) |
12.7
± 2.2(59) |
INT |
|
|
|
|
|
|
|
|
|
|
IRC+10216
2
09h 47m 57.382s
+13o 16 43.66 |
6.12
± 0.19(15) |
13.1
± 1.8(13) |
Phot |
|
|
2.0
± 0.1 (4)** |
| 6.07 (1) |
12.9 (1) |
Map |
|
6.12
± 0.32 (12) |
|
8.8
± 1.1(736) |
17.5
± 4.5(169) |
INT |
|
|
|
|
|
|
|
|
|
|
16293-2422
16h 32m 22.909s
-24o 28 35.60 |
16.3
± 10% |
78.1
± 20% |
Maps |
|
|
|
| |
|
|
|
|
|
| |
|
|
|
|
|
|
|
|
|
|
|
|
CRL2688
21h 02m 18.805s
+36o 41 37.70 |
5.88
± 0.22(6) |
24.8
± 2.4(6) |
Phot |
|
|
1.84
± 0.04 (11) |
5.93
± 0.39(12) |
23.2
± 1.9(12) |
Maps |
|
6.14
± 0.25(7) |
|
6.39
± 0.51(223) |
30.9
± 3.8(57) |
INT |
|
|
|
* - all 850 map data added to pointing set
* - avg. of data from Mar-Apr 1998
* - more data are needed
The table includes the results presented in
"Towards the automated reduction and calibration of SCUBA data from the
JCMT"
by
T.Jenness, J.A.Stevens, E.N.Archibald,
F.Economou, N.E.Jessop & E.I.Robson.
In particular, the red indices in the table indicate :
brightnesses are also now quoted
using 'integrated' flux conversion factors for jiggle maps and a 40
arcsec (software) aperture. These are labelled INT in the
table. This INT method of reducing mapping data is valid for
observations of objects that are slightly extended.
The older measures by Sandell (2001,
ESA SP Ser. Vol 481, pE93) are based on 'peak' FCFs and are valid for
point-sources. The older measures will therefore underestimate the
total flux if the source is extended, as is most noticeable in the cases
of IRC+10216
and CRL2688.
variability : in
IRC+10216
and OH231.8.
Plots of 2-4 years' worth of data and, where appropriate, fitted light
curves, now are available. Click on the the object names for more
information.
Further notes to the table :
-
To repeat 1 above : flux densities are given
in Jy/beam for the photometry and mapping results, and in
Jy/40-arcsecond-aperture for INT.
-
The number of data points used is given in parentheses.
-
For the small data sets the quoted errors are probably too optimistic,
and should perhaps be doubled.
-
Photometry and mapping results have been kept separate,
but for these secondary calibrators the results should be - and are - the
same.
-
The column headed `Pointing
maps' refers to calibrated pointing observations (16-point jiggle maps),
which are expected to yield results identical to other calibrated maps.
-
Calibration has not been attempted at 350/750 micron, and
very few 1350um data were available before the
filter drum broke in 1999.
Fluxes of these sources and others at ~1.2mm have been published by
IRAM.
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