revised VLASS proposal

jlazio
Posts: 8
Joined: Thu Mar 20, 2014 11:13 pm

revised VLASS proposal

Postby jlazio » Thu Sep 25, 2014 10:10 am

All,

Based in part on discussions about what is the appropriate scope of the VLASS and comparisons with optical surveys, there is some thought being given to "simplifying" the VLASS. One of the suggestions that has been floated is that the entire GALACTIC component of the VLASS be simply eliminated.

If you have strong opinions, now would be the time to express them.

Thanks.

shami
Posts: 7
Joined: Wed Feb 19, 2014 2:24 pm

Re: revised VLASS proposal

Postby shami » Thu Sep 25, 2014 11:11 am

I think that would be a terrible idea, since we're sacrificing a whole lot of science. We could simply eliminate the extragalactic deep fields too, and call them PI science... Unless the idea is to just do a much deeper all-sky survey, I don't understand the logic of dumping one of the survey tiers.

So count me as a No vote for what that's worth, I guess? Or as a cautious vote in favor of a deeper uniform all-sky program with no extra tiers - that's "simple".

bgaensler
Posts: 4
Joined: Thu Feb 20, 2014 2:04 am

Re: revised VLASS proposal

Postby bgaensler » Thu Oct 30, 2014 4:26 am

Hi Joe,

Speaking as a Galactic astronomer, I don't see this as a bad idea. The last version of the VLASS draft I saw was too broad and tried to promise everything to everyone, without really making a strong case for anything. Demonstrating that we really do have specific motivations, and are thus prepared to prioritise and give up some things, would make it easier to sell the survey. Plus not asking for Galactic LSTs will greatly relieve the widespread concern that VLASS will replace too much PI science.

Overall, the extragalactic science goals for VLASS seem stronger and better defined than the Galactic ones, and the latter could be dropped without the proposal seeming weak or half-baked. The proposal talks a lot about all the great science done from NVSS and FIRST, but the equivalent Galactic survey would be MAGPIS. Has MAGPIS transformed Galactic astronomy the way NVSS and FIRST have transformed extragalactic astronomy? The answer is a clear "no", and I think there's your answer. We could comfortably live with dropping the Galactic component, especially if doing so strengthens the rest of the proposal.

regards
Bryan
Last edited by bgaensler on Thu Oct 30, 2014 4:29 am, edited 1 time in total.

bgaensler
Posts: 4
Joined: Thu Feb 20, 2014 2:04 am

Re: revised VLASS proposal

Postby bgaensler » Thu Oct 30, 2014 4:28 am

Also, all the different tiers and modes we're proposing seem like too much of a "back door", aimed at getting around the Director's mandate that there will only be one VLASS survey. By cobbling together all these different surveys, we're not entirely sticking with the spirit of that requirement.

A case can be made that the various extragalactic tiers are a single survey, but the Galactic survey sits on the side and can't really be strongly argued to be motivated by the same goals and vision as the rest of it.

To put it another way - if the Director decides there's some sidecars on the main survey and one or more of them need to be chopped, which one would we be hoping he chops? If the answer is Galactic, we should do ourselves a favour and take our destiny into our own hands here.

Bryan

shami
Posts: 7
Joined: Wed Feb 19, 2014 2:24 pm

Re: revised VLASS proposal

Postby shami » Thu Oct 30, 2014 11:16 am

Hi Bryan, others - I'm not sure whether this forum is relevant any longer, but for the record, one of the motivations for an "extra" Galactic tier was to bring the Galactic plane coverage up to a standard comparable to the rest of the all-sky survey. Given the low elevations at the GC, that requires some extra integration time; given the much higher source density, it requires some higher resolution observations. The simplest solution was to add extra A-array observations of the plane to the all-sky observations in B-array.

If we don't do something like this, the all-sky atlas will be worse (more confused, lower sensitivity) in the Galactic plane than in the rest of the sky.


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