DATE: Wed, 18 Nov 2009 13:47:11 +1100
SUBJECT: EIF and NG1dF


Subject: EIF and NG1dF

Dear fellow members of the Australian astronomy community,

This is an "advocacy" email with regards to the NG1dF instrument, and  
to provide more information about the project science, and the  
possibilities for UK support. This is to follow-on from Matthew  
Colless's email last week about AAT EIF options and he has encouraged  
me to do so. However this email reflects entirely my own personal  
views not the AAO's.

NG1dF was the second ranked AAT new instrument which emerged from the  
new instrument workshop a couple of years ago. (HERMES the multi-fibre  
high-resolution stellar spectrograph which is being built was number  
1). NG1dF is a highly efficient multi-slit spectrograph, conceived by  
Durham University,  designed to sit at the AAT Prime Focus offering a   
1 deg field of view and 4000 objects at one multiplex. What it offers  
is a TEN-FOLD multiplex improvement over the current AAOmega system  
and a factor of 2-3 throughput gain. Spectra are low-medium  
resolution, so essentially this is a dark time extragalactic  
spectroscopy machine about 20-30x more powerful than AAOMega (if  
galaxy numbers is the primary metric). Quality spectra can be obtained  
in the redshift range 0<z<1. The main innovation is the field-of-view  
is achieved by replication of cheap MOS units. (The concept does scale  
to a 2 deg FOV with 16000 slits). Particularly exciting is the  
possible use of nod & shuffle with this system (which is more  
efficient than with fibres) to allow very deep exposures over wide  
fields.

The main science area which is of interest to Australians is perhaps  
follow-up of ASKAP deep fields. Let me quote from the NG1dF report:

"Optical imaging and spectroscopy reveal the stellar mass, ionized gas  
and star- formation rates of galaxies. Radio observations complement  
them by revealing the cold gas fuelling star-formation and galaxy  
assembly.

A particular NG1dF science synergy in Australia is the potential to  
follow-up and complement observations of the Australian SKA  
Pathfinder, which is being built and is scheduled to start operating  
in 2013, and further in the future the SKA itself. ASKAP will be doing  
neutral hydrogen 21cm galaxy surveys over areas of at least 30 deg2 to  
z~0.5 and SKA hemisphere surveys to z~1.5. There will also be  
associated radio continuum surveys of AGN and extreme star-forming  
galaxies over similar areas of great interest to extragalactic  
studies. ASKAP and SKA will both be built at southern hemisphere sites  
and optimal coverage of the u,v plane means that deep surveys are  
likely to be at southern declinations and not on the equator. This  
gives a great advantage to NG1dF on the AAT and would be a unique  
facility.

The high object densities of these surveys (up to 10,000 deg–2) also  
means that a very high-multiplex system is required for follow-up. The  
matching of NG1dF to both ASKAP HI and radio continuum surveys is  
uncannily perfect and it is clear that access to NG1dF will  
significantly enhance the science returns of the $100M Australian  
investment in radio astronomy hardware."

I think NG1dF offers special synergy to ASKAP science, and given the  
beam size (10-30 arcsec resolution) matching to optical galaxies will  
have to be done in 3D (RA,DEC,z) to avoid severe confusion problems.

Other science themes (briefly) are (i) cosmological redshifts surveys  
(growth of structure) where significant advances over WiggleZ are  
possible (ii) SDSS-quality surveys at z=0.5 probing galaxy  
environments and dependence of properties on halos (iii) mass mapping  
of clusters and other detailed cluster science (iv) follow-up of wide  
field imaging surveys (VISTA, PANSTARRS, Skymapper, ASKAP etc.) (v)  
low-resolution galactic archeology surveys to complement HERMES.

More details of science concepts can be found in a science summary/ 
overview document extracted from the full study report at -

   http://www.aao.gov.au/local/www/tjf/ng1df_summary.pdf

Please note especially the Table on page 6 showing the large increase  
in survey power over existing instrumentation.

A jointly funded AAO-Durham feasibility study was carried out in 2009  
and  a preliminary design was costed quite rigorously. The cost came  
to A$10M, if one adds a 30% contingency this comes to $13M. This is  
obviously bigger than the EIF budget but I envision the way this would  
go forward would be via cost-sharing with the UK. The project  
timescale is 5 years from design to commissioning.

Durham has been pursuing the concept on other telescopes, and has been  
looking at "XMS" (eXtreme Multiplex Spectrograph) on the Calo-Alto  
telescope and have formed a partnership with Edinburgh and Portsmouth  
to raise funding. However this is not definite and they are still  
seriously interested in an Australian option. The options and  
timescales for possible UK funding are described in the attached  
letter which the Dept. Heads of Durham, Edinburgh and Portsmouth have  
signed.

A possible strawman model could be $5M UK, $5M AAL with the  
contingency covered by the AAO on-going funding. (That is not to say  
the AAO has agreed to this but it IS an acknowledged possibility, it  
would likely depend on the amount of community support for the concept).

Where do we go from here? If YOU think the NG1dF concept should be the  
top priority for an AAO EIF bid then you should write to the AAO  
Director by his Nov 20th deadline or as soon as possible and tell him  
so. The concept is fundable if the community ranks it high enough.  
Right now we are at the EOI stage and the EIF money does not flow  
until 2011 so the timing is good to work out a new partnership with  
the UK.

Finally let me say that to my mind one non-quantifiable benefit of the  
NG1dF project is this gives us a new opportunity to keep a strong  
scientific partnership going with the UK post-2010 and to be able to  
form science collaborations accessing facilities like VISTA and ESO.

sincerely,

Karl Glazebrook

----------------
Prof. Karl Glazebrook
Centre for Astrophysics & Supercomputing, Swinburne University of  
Technology
Contact: +61-3-9214-4384  karl@astro.swin.edu.au