From pwl@herts.ac.uk Tue Oct 31 15:39:33 2006
Date: Mon, 30 Oct 2006 13:37:55 +0000 (GMT)
From: Phil Lucas <pwl@herts.ac.uk>
To: DIANE GREENING <DIANE.GREENING@pparc.ac.uk>
Subject: Re: Report on G/07A/36

Report on G/07A/36: "Resolving the structure of debris disks
around 30-100 Myr A stars"

P.I. Mark Wyatt

N.B. This proposal should be considered at the same time as
G/07A/34 - they are effectively one proposal that has been
submitted twice in order to use both Gemini North/Michelle and
Gemini South/T-RECS

For my scientific comments please refer to my report on G/07A/34
(appended below). Note, I had not appreciated that the time was request 
was spread over 2 proposals. I still recommend that time is given
only for observations of HD181296 (i.e. proposal 34, using T-RECS)
and I still suggest giving the minimum time, which permits
observations in the N abnd and Qa band. The proposers do not
justify their rquest for Qb, which is the most time consuming
filter. The model in Figure 1 indicates that resolved emission
is more likely to be detected at N band than Q band, so why
try Qb? I do not recommend giving time for proposal 36.

Grade 4 (for proposal 36)
Referee: Phil Lucas
Self assessment: 2

On Mon, 30 Oct 2006, Phil Lucas wrote:

> Report on G/07A/34: "Resolving the structure of debris disks
> around 30-100 Myr A stars"
> 
> P.I. Mark Wyatt
> 
> Spatially resolved debris disc systems have rapidly increased
> in number in recent years. These systems are important because
> they provide perhaps the best available clues to understanding of
> the mysterious process of planet formation.
> This proposal aims to spatially resolve 2 debris disc systems
> in the mid-IR that have greater ages than any previously imaged
> in this waveband. Although debris disks have been resolved around 
> some much older systems at submm and optical wavelengths
> (eg. Kalas et al.2006, ApJLetters 637,57) the proposers argues that
> mapping of mid-IR emission in relatively old systems could tell us 
> something important. Since the reason for lack of spatially resolved
> mid-IR emission in old systems is not known it is not clear that this 
> is the case. Successful observations might provide some hint of how
> the disc size changes with age, or detect clumps attributable
> to collisions between protoplanets, as the proposers suggest.
> As far as I can tell most debris disc systems have not yet been
> imaged at high spatial reesolution in the mid-IR.
> 
> These observations are time consuming and the technical feasibility
> seems questionable to me, since there is a long time delay (1.5 
> hours) between observation of the targets and the PSF reference star, in 
> which time the image profile could change significantly. The models
> in Figure 1 do not appear to address the issue of PSF stability,
> though it is stated in the science case that problems occurred with
> the instrument during the previous Gemini run. 
> While I am not a mid-IR observing expert, and the TAC may 
> disagree, I would therefore suggest giving the minimum requested 
> allocation (or half the total maybe) in order to observe only HD181296, 
> since the predictions in Figure 1 show that the disc around this star is 
> far more likely to be resolved than that around HD1438. HD1438
> looks a bit marginal.
> 
> Grade: 3
> Referee: Phil Lucas
> Self Assessment: 2
> 
> 
> 
>