Galactic WG Summary so far (comments please!)

c.c.lang
Posts: 6
Joined: Fri Mar 07, 2014 2:30 pm

Galactic WG Summary so far (comments please!)

Postby c.c.lang » Sat Mar 22, 2014 3:36 pm

Hi all,

We will be submitting a possible template tomorrow (Sunday morning) for VLASS from the Galactic WG perspective. From reading the white papers and the comments on the forum here, it appears that there are two 'tiers' of Galactic survey interest emerging:

(1) Tier 1:
a full coverage (l=-20 to 260 degrees; b= -5 to 5 degrees) survey of the Galaxy at a lower frequency (L, S or C band) with high spatial resolution (1-5") and multi configurations to focus on deep imaging, spectral index across the band and polarization/RM science in the Galaxy. Because of the lower frequencies, GBT observations are probably not necessary to recover large scale structures.

(2) Tier 2:
deep survey at higher frequency of a more restricted region (i.e., inner Galaxy and specific targets: GC, M31, Taurus/Orion, Spurs) at high resolution (1-5") to focus on thermal science (continuum plus spectral lines) and also match existing multi-wavelength surveys. This survey may need to be supplemented with GBT observations.

Comments welcome please!

samao
Posts: 1
Joined: Tue Feb 07, 2012 9:43 pm

Re: Galactic WG Summary so far (comments please!)

Postby samao » Sun Mar 23, 2014 9:20 am

Sorry for joining the discussion late. If the Tier 1 design allows for the detection of extended polarized emission, one additional exciting science would be to carry out polarization gradient works (Gaensler+2011) to characterize turbulence in the magnetized medium.
Ann

lsjouwerman
Posts: 21
Joined: Mon Jul 18, 2011 3:49 pm

Re: Galactic WG Summary so far (comments please!)

Postby lsjouwerman » Sun Mar 23, 2014 12:30 pm

Hi Cornelia,

I think you are not right about the tiers, there was no discussion in this forum about a full plane low freq survey. There is discussion about a full plane HIGH freq at low sensitivity versus a restricted area high sensitivity, mainly targeted for the central region and both are for compact sources (not extended - and complementary Ku band GBT already exists).

rosten
Posts: 19
Joined: Fri Feb 14, 2014 3:40 pm

Re: Galactic WG Summary so far (comments please!)

Postby rosten » Sun Mar 23, 2014 9:06 pm

Hi Laurent,

Yes I made this comment to Cornelia already. No worries.

c.c.lang
Posts: 6
Joined: Fri Mar 07, 2014 2:30 pm

Re: Galactic WG Summary so far (comments please!)

Postby c.c.lang » Sun Mar 23, 2014 10:16 pm

Hi all,

I thought that Sanjay had proposed for a lower frequency wide-band survey of the Galactic plane in order to do non-thermal imaging and also to do RM/polarization work?

elisabethmills
Posts: 13
Joined: Tue Mar 11, 2014 3:58 pm

Re: Galactic WG Summary so far (comments please!)

Postby elisabethmills » Mon Mar 24, 2014 12:27 am

From what I understand, Sanjay is no longer strongly pushing for this (but please correct me if I am wrong).

The survey proposed in his white paper was low-frequency (S or L), but in C+D+GBT configurations, so as to be optimized for extended emission and ISM tracers.

Note that I am similarly making no push to do a deep Galactic center component: I think that is something better treated as PI science.

c.c.lang
Posts: 6
Joined: Fri Mar 07, 2014 2:30 pm

Re: Galactic WG Summary so far (comments please!)

Postby c.c.lang » Mon Mar 24, 2014 12:36 am

OK, sounds like we will propose for a Ku band survey as outlined in the GUTS white paper then. There will be more discussion in the coming days and we will post here.

Thanks for feedback!

lsjouwerman
Posts: 21
Joined: Mon Jul 18, 2011 3:49 pm

Re: Galactic WG Summary so far (comments please!)

Postby lsjouwerman » Mon Mar 24, 2014 1:18 am

Note that if the GUTS WP sensitivity trade-off (~130 uJy/bm) is generally considered too shallow, one could suggest to increase the observing time per position to get a better sensitivity. Then trade-offs become larger total observing request (and thus larger impact on PI driven science), and/or less coverage of the Galactic plane. Personally I prefer to do the originally WP proposed full 2800 square degrees at a slightly shallower sensitivity and not pre-select/bias to a specific region of the plane. If one really wants to go deep, and keep the orignal 3200 hours observing request constant, then the 2800 has to be cut considerably, to e.g. 150 sq deg for 30 uJy/bm (and a much larger pressure on that particular LST range). A factor 2 in sensitivity cuts the area by a factor 4 thus I prefer to cover area first and identify regions of interest to observe deeper later, as the 130 uJy/bm (detecting compact sources down to ~1 mJy/bm) should be sufficient for a legacy survey and this purpose. The regions selected for more sensitive observations (or default sensitivity extentions into Orion/Taurus/Oph) could be a second (and/or third) tier to the full plane survey.

c.c.lang
Posts: 6
Joined: Fri Mar 07, 2014 2:30 pm

Re: Galactic WG Summary so far (comments please!)

Postby c.c.lang » Mon Mar 24, 2014 1:27 am

I think we'll start in our discussion tomorrow by proposing the ~1 mJy detection threshold (i.e., ~130 muJy sensitivity; 3200 hours; whole plane) and discussing a second and/or third tier that would be more sensitive and focus on particular regions. The proposed whole plane survey parameters are taken right from the GUTS White Paper.

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

Re: Galactic WG Summary so far (comments please!)

Postby shami » Mon Mar 24, 2014 5:14 pm

Hi Cornelia and others,
I didn't realize that the Galactic discussion started de novo on this discussion board, but some of use would certainly prefer a lower frequency, high resolution imaging survey of the Galactic plane. I'd agree that there's not much point going down to 1-2 GHz at the Galactic center, but for the rest of the plane, 1-2 GHz A-array and 2-4 GHz B-array would be very useful and complementary data sets.
-Shami


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