CO in a HiZ StarburstMinutes for meeting Mon, 26 October 1998 at 11am ET.
Date: Monday, 26 October, 1998
Time: 11:00 am EST (9:00 am Socorro, 9:00 am Tucson)
Phone: (804)296-7082 (CV SoundStation Premier Conference phone).
Past minutes, etc on MMA Imaging and Calibration Division Page
Agenda
--------
Experience from the BIMA Key Project on Galaxies: SD/interferometer addition, relative pointing calibration, relative amplitude calibration, and miscellaneous deconvolution issues (Helfer)
The project specifically includes combination of 12m OTF maps and BIMA maps of galaxies. Sault's mosmem and related routines in miriad are used. A number of problems were discussed involving: * use of gaussian to approximate 12m beam, and problems associated with that; weighting of SD data; * dealing with decorrelation in the BIMA data (using SD model for M51 selfcal didn't work); * reported renewed interest in getting more accurate BIMA autocorrelation data which is currently limited by: bad and temporally variable data, not OTF mode, non-nutating secondary, variation of total power with 3s refrigerator power cycle, etc.
Query from Webber: How much aliasing from out of band lines in a digitally filtered band can we tolerate scientifically? Is 25db acceptable?
Rejection was 23 db on the non-digitally-filtered HySpec, and is about 20db or larger for the other sideband in current receivers. After the meeting, Turner reasoned that he would like to be able to observe 10 mK lines near OMC1, whose strongest line (CO) is 70K or so. This suggests 40db of rejection would certainly be best.
New image in Image Gallery:
We discussed how best to attach captions to images. There seemed to be general agreement that the pictures should lead one to a separate WWW page with the picture and caption on one page.
MAC meeting: Plans
This was deferred pending the second generation of a meeting plan.
Report from the JCMT/CSO interferometer 183 GHz radiometer phase correcting experiment (Yun)
FIRST FRINGES AT 690 GHz! Yun reported that the interferometer had successfully obtained fringes at this highest frequency yet. He stayed for 5 or the ten days in the run to watch the operation of the 183 GHz phase correction radiometer system, working with Martina Wiedner and others. He described numerous instrumental and weather problems which have prevented this system from working as planned in the past.
One problem emphasized by Wiedner was that one had to have a good atmospheric model to interpret the data--the temperature and pressure of the water layer must be well known. In fact, they are not. One approach might be to use more channels to sample the atmospheric line than the three currently employed. This will ameliorate the problem but not solve it completely. This problem exists, less seriously perhaps, at 22 GHz also.
These devices are about 40 x 30 x 30 cm and could be made smaller. On the MMA, some of the systems present in the JCMT/CSO devices may not be needed. For example, the Welch/Bock calibration system could alleviate some of the calibration bits.
The Chajnantor system has a single instrument working. There is no phase lock loop, which is not serious if the LO is stable enough compared to the bandwidth of the sampling spectral channels.
Since the JCMT/CSO goal of obtaining fringes at 690 GHz appears to have been reached, and demand for a single baseline interferometer may not be sufficient to keep it operational, the future of this system is unassured. Reportedly the SMA (which also reported first fringes this week, at Haystack) has no plans for a similar instrument. While both Woody and Staguhn have expressed interest in such a system, operation at the low altitudes of BIMA or OVRO is not practical. This is viewed as a problem for the MMA project. However, in the larger LMA context, the Europeans (the UK built and operates the JCMT/CSO system; OSO the Chajnantor system) will pursue this project. At the Division Heads meeting, Napier reported that the current baseline antenna design has a Cassegrain hole big enough for a 22 GHz beam waist, should such a system be needed on the MMA. It would not, however, fit in the current baseline dewar.
At the University of Virginia, Alan Boss gave a lecture Tuesday on Extrasolar
Planets. He pointed out the problem with the Pollack/Bodenheimer accretion
scenario timescale for the formation of giant planets. He noted that the
collapse model which he proposed will produce giant planets on shorter
(10
Action Items 26Oct98
------
URSI Meeting (Radford)
Radford reported that one presentation slot is open.
Travel
------
T. Helfer:07Oct-17Oct (Green Bank/UMD), 20-22 Nov (Chi) 26Nov-09Dec (Tenerife)
A. Wootten: 13Oct-15Oct (U. Md.) 20-22 Nov (Chi)
J. Mangum: 20-22 Nov (Chi)
S. Radford: 20-22 Nov (Chi)