|
As previous ADAPs
have illustrated, ASKAP is an excellent instrument for surveying the sky. We
had previously surveyed the sky four times with RACS (Rapid ASKAP
Continuum Survey), three times in different frequency bands
(RACS-low,
RACS-mid
and
RACS-high)
and a fourth time to revisit the sky in the lowest frequency band
(RACS-low2).
Observing in different frequency bands allows us to understand the
physics behind any specific object we are studying, i.e., is it a
galaxy, a star or something more exotic? Observing multiple times
allows us to find things that change over time, e.g., supernovae,
pulsars, planets. It also allows us to visualise improvements in our
observing and processing strategies. Over the 2023--2024 summer
shutdown period (when the facilities are minimally staffed) we decided
to put ASKAP to work to survey the entire sky again with minimal
intervention
(mostly automated using SAURON - the ASKAP autonomous scheduler).
Our approach used some of the
learnings from previous RACS observations -- we used a similar
observing style to RACS-mid and RACS-high to improve response of the
telescope (this is achieved by increasing the overlap in the 36 ASKAP
beams) and a slightly higher frequency compared to RACS-low and
RACS-low2 to avoid known radio frequency interference (RFI). The
result was a 9% improvement in sensitivity and a slight increase in
the amount of sky observed (we could edge slightly higher towards the
northern sky). RACS-low3 was complete in 54 days and only used a total
of 16.8 days of telescope time. The observations have already been
processed (with one tantalising discovery already - stay tuned for
news on that) and over the coming months we plan to release this data
to the astronomical community.
|
