From: Andrew Blain <awb@astro.caltech.edu> To: Chris Carilli <ccarilli@aoc.nrao.edu> cc: Andrew Blain <awb@phobos.caltech.edu>, awootten@nrao.edu, Pierre Cox <Pierre.Cox@ias.u-psud.fr> Subject: Re: DRSP review Date: Thu, 17 Feb 2005 15:43:53 -0800 (PST)

I've been through the 1.X's, and couldn't see any killers. Notes attached, including some notes on my DRSPs, which I hadn't changed since the review comments were attached.

In comments.txt are also some trivial thoughts about ways to trim. I'm prefer to see operations of a smaller subset of the array than a maxed out version, which like the VLA is unlikely ever to grow.

In terms of lobbying for a more powerful array, I think the fact that the DRSPs are significantly oversubscribed must point to the desire for an array as large as possible.

I don't see an easy way to make this argument, as all that good science could still be done, just take longer. Only when the array becomes less than 5x CARMA or IRAM does a big problem develop for extragalactic science. Maybe there's a clearer breakpoint when mosaicking?

A

PS Al, please let me know if I should send these notes anywhere else. I hope Pierre and Chris can represent this area at the meeting.

On Wed, 16 Feb 2005, Chris Carilli wrote:

'> how about this:
'>
'> I'll look at DRSP 1.1.5, 1.3.1, 1.3.2, and 1.6.1 - 1.6.7
'>
'> Then you'all could divi-up the rest of 1.1, 1.2, 1.4, 1.5
'>
'> that gives us each between 9 and 10. If you can't deal,
'> let me know and I can fill-in.
'>
'> I don't think we should go into too much detail.
'> In most cases it will come down to just increasing the
'> integration time. we should focus on the few programs
'> that are fundamentally disabled by going to 50 antennas.
'> Could be we don't find any.
'>
'> cc
'>
'>Comments on status of DRSP on antenna number cut.

Andrew Blain

17 February 2005

1.X DRSP numbers are relatively lightly affected by reduction in the number of antennas. Since most targets are faint, with modest dynamic range requirements, and the imaging quality from ALMA remains much better than existing facilities, the main hit is in integration time, requiring surveyed areas and numbers of sources to be trimmed, approximately as (final #/64) squared.

I have read through all the 1.X programs, and do not believe that any would be ruled out by a smaller array. Imaging is more sensitive to individual antenna configuration changes, and antenna breakdowns. However, I don't expect this to make any program impractical.

The combination of sensitivity and resolution remains so much better than current telescopes can achieve that ALMA would remain a very valuable tool at 50 antenna. My intuition is that the gain over IRAM, CARMA and SMA ceases to be so compelling at the ~30 antenna level.

Given that receivers are not too far from the quantum limit, Atacama is an excellent site, and correlators are probably growing cheaper with time, I would prefer to see the simultaneous operation of 40 antenna out of a procured total of 55 than a fully operational array complete array of only 48 for example. Switching antenna in and out would seem to be a way to speed up the reconfiguration process, and provide the ability to maximise the working size of the array at 2nd generation correlator level.

Andrew Blain

Feb 17 2005

Comments on current state of DRSPs I submitted:

1.1.6 Ultradeep continuum survey

Section: 5.4: Agree blank-field SZ detections with ACA unlikely in these small fields. Blank field surveys should consider centering on locations where deep ALMA surveys are available. For foreground subtraction, want high-resolution ALMA coverage of any candidates to deep levels.

Cutback is reasonable: better to cutback area than depth.

1.1.7 Deep line emission search

Section: 4.1: Clarify comment about 2-hrs: GOODS-S will soak up a lot off time there. `Might want to avoid choosing additional fields near 02hr if possible.'

Section 5.4: As 1.1.6.

Comment on strategy: Desire to make unbiased catalog of line-emitting galaxies. Band-3 and 140-GHz band are likely the most efficient ALMA bands for detecting serendipitous lines. Going deeper is possible, but expect the detection rate to be higher covering a wider field to a brighter limit. Only ALMA will tell. Could be preferable to use a nested approach, and dig deeper in a subfield.

1.1.8: Submillimeter galaxy followup

A smaller survey could certainly be possible; however, certainly need several 100 examples to allow AGN content, mass distribution and range of morphology to be quantified. 500 is probably reasonable.

1.2.1: Weak lensing of disks

Section: 8.2: To make this observation must have a spatially-resolved rotation curve, and so an accurate line-of-sight velocity needed to each resolution element in the disk. Expect 10km/s velocity dispersion at each point, therefore accurate line center frequency at the 2km/s level.

1.2.2: Cluster mapping

Comment: Cutting back is possible. Need to image to maximum depth, gain in science is slower than linear with cluster number.

1.2.3: Planck Surveyor followup:

Comment: Possible to make initial detection using single-dish telescope to save ALMA's mosaicking time.

Not necessary to follow up all Planck sources, after full range quantified. Several 100 in south ecliptic pole region probably adequate to start. Long-duration program to map the remainder of the total ~10000 expected (starting with the brightest) is possible.

-- AlWootten - 21 Feb 2005

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Topic revision: 2005-02-21, AlWootten
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