1. Early Continuum Science with ASKAP
- Early Science is an exciting stage for any new facility.
We can't know the exact timescales or roll-out of various capabilities, but we have to plan for all eventualities, including lots of time for early science with a well working telescope. We want the opportunity to conduct ground-breaking science to make the highest impact on the community.
To that end we propose a large area, full stokes, range survey which enable a great progress in many EMU science areas, but particularly the original key goal of galaxy evolution
However, we propose a observing across the full 1100MHz bandwidth which would provide a truly unique data set (different to that which the final ASKAP would produce).
Early Continuum Science with ASKAP
CSIRO Astronomy & space Science
Ray Norris, Nick Seymour (CASS) , Andrew Hopkins (AAO)

2. 30uJy/beam rms in a 12hour integration Confusion noise ~<20uJy/beam
ASKAP12+ will be one of the most powerful survey radio telescopes in the world
30uJy/beam rms in a 12hour integration
Confusion noise ~<20uJy/beam
The full ASKAP will be able to survey the same area to the same depth as the JVLA but about 8x quicker. ASKAP12 will be around 3x quicker, plus there is the possibility of larger amounts of observing time during early science phase.
If you consider a full synthesis scan of one ASKAP footprint over 12hours, which is required for the uv-coverage and dynamic range for even medium depth continuum observations, then you can reach 30uJy rms. This depth is interesting as we will be detecting over 10^4 sources per tile with a 50/50 mix of powerful AGN and SFGs.
Even with the larger synthesis beam of ASKAP12 compared to ASKAP36 we would still be well above the estimated confusion noise.

3. Stripe 82/SPT
So what area of survey parameter space would be truly ground-breaking? Here we have a plot of all the major radio continuum surveys showing depth v area. In the bottom left you have all the deep, pencil-beam surveys consisting of a pointing or two on the various famous deep fields. In the top right you have the large area, all-sky surveys. This diagonal line basically represents the amount of time any TAC would give you on a radio telescope.
We see here the virgin parameter space which EMU, and the comensuate surveys, will probe. But what could we do with ASKAP12 that would really make strides into this parameter space.
Blurb B2

4. ASKAP12+ Stripe 82/SPT Blurb B2
- To make a significant dent beyond this imaginary solid line we would want to cover at least 1,000 deg^2. We'd still be a long way from EMU, but we would have made a large step into this top-left wedge.
10^3 deg^2 in 33nights of 12hours = 300k sources
Blurb B2

5. Main Science Goals Double the total number of radio sources known
Constrain evolution of radio-loud AGN population
- Why do we want to probe this wedge? To put it crudely it's about numbers.
10^4 deg^2 in 330 nights = 3M sources, thereby more than doubling the total number of radio sources known
Trace the knee of the radio-loud population to z~2
- Surface brightness temperature of ~1K, better than NVSS or SUMSS
- This would mean we would not miss radio emission from radio galaxy relics/halos as well as face-on spirals

6. Main Science Goals Double the total number of radio sources known
Constrain evolution of radio-loud AGN population
- Why do we want to probe this wedge? To put it crudely it's about numbers.
10^4 deg^2 in 330 nights = 3M sources, thereby more than doubling the total number of radio sources known
Trace the knee of the radio-loud population to z~2
- Surface brightness temperature of ~1K, better than NVSS or SUMSS
- This would mean we would not miss radio emission from radio galaxy relics/halos as well as face-on spirals
Mao et al. 2012

7. Main Science Goals Double the total number of radio sources known
Constrain evolution of radio-loud AGN population
Increase the total number of sub-mJy radio sources by two orders of magnitude
Constrain star formation to z~0.5
So when we look at the source counts we no that bright AGN dominate the bright end
But at fainter fluxes regular star forming galaxies gradually contribute.
Until they make a contribution by number around 200uJy, just above the 5sgima detection limit of the proposed survey.

8. Main Science Goals Double the total number of radio sources known
Constrain evolution of radio-loud AGN population
Increase the total number of sub-mJy radio sources by an order of magnitude
Constrain star formation to z~0.5
- The proposed sensitivity limit would reach well below the knee of the SFG LF at z~0.5. With a mix of spec-z and photo-z we could trace this with unprecedented precision.

9. Main Science Goals Double the total number of radio sources known
Constrain evolution of radio-loud AGN population
Increase the total number of sub-mJy radio sources by an order of magnitude
Constrain star formation to z~0.5
We can then, for example, reproduce the comoving SFRD out to this redshift. This plot is what we has been possible with just a very small albeit deeper survey. With the large area we would obtain far-greater accuracy and fidelity

10. Compliment full EMU Cover full 700-1800MHz frequency range
Switch between 3 bands every 20mins
Obtain spectral index and spectral curvature information
In order to compliment and not be superseded by EMU we plan to cover most or all of the 1100MHz frequency range.
To achieve these we imagine that the frequency band would switch between 3 settings every 20mins approximately.
Such observations would provide spectral indices and curvatures with delta(nu)/nu~1

11. Compliment full EMU Cover full 700-1800MHz frequency range
Switch between 3 bands every 20mins
Obtain spectral index and spectral curvature information
Characterise faint population
Obtain unique samples of rare sources: USS, GPS
Allow spectral index and curvature to be compared to full EMU determined over narrower range
Obtain polarisation and RM measurements which are very important in diagnosis of faint populations
This information could be used to: [list]

12. Additional EMU Science Additional ASKAP Science
Cosmology
Galactic Astronomy
Local Galaxies
Serendipitous discoveries
Additional ASKAP Science
The polarised sky
HI absorption
Transients
Legacy value to astronomical community

13. Discussion points
Can the correlator be adapted to 384MHz (or =>366MHz) ?
Angular resolution is key: confusion and cross-identification
Can the full bandwidth be imaged simultaneously?
Which areas of sky would be prioritised?
Deep survey expected by combining regular observations of standard field (as part of science verification).
Several issues for discussion.

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