[asac] Re: Three examples for ACA evaluation

[Tetsuo Hasegawa]

Dear Ewine and ASAC members,

Based on discussions with Yasuo Fukui and my colleagues in the ALMA-J 
office, I choose the following three examples as appropriate to measure the 
possible benefit from ACA out of the table I sent yesterday:

Example 1: Extended protostellar envelopes --- How accurate can ALMA images 
reproduce its radial profile?

Example 2: Multiple dense cores in a GMC at a distance of LMC --- How 
accurate can an ALMA image reproduce the extended diffuse component and the 
mass function of the cores embedded therein?

Example 3: Face-on disk galaxies at small to intermediate distances --- How 
accurate can ALMA images reproduce the extended disk component and the 
brightness of the arms and the interarm regions?

We understand that there are many other important subjects for ALMA. 
However, the above examples should serve as a good set of benchmarks for a 
single peak+envelope system (Example 1), a multiple and random peaks+common 
envelope system (Example 2), and an extended structure with quasi-periodic 
patterns (Example 3).  We will encounter similar situations in various 
observational programs with ALMA.

We may wish to ratio images taken at different frequencies to get spatial 
maps of the spectral index in the continuum or the line intensity ratios. 
In the Example 3, we may also measure the arm/interarm contrast.  For these 
purposes, we should evaluate the accuracy (or fidelity) of the reproduced 
image in reference to the in-situ brightness of the original image, i.e., 
in terms of images showing the fractional error
[(reproduced intensity) - (original intensity)]/(original intensity),
at least at two different observing frequencies for the same model source.

The actual observations will be made both in continuum and in line, but 
simulating only continuum observations should be sufficient for the current 
purpose.

With best,

Tetsuo

At 8:58 +0200 01.6.19, Ewine van Dishoeck wrote:
>Dear Tetsuo,
>
>Many thanks for the input on the ACA science examples. It is very good to see
>that the Japanese community is so actively thinking about ALMA programs!
>
>Which of the 2-3 programs would you consider as the highest priority for the
>ACA?
>
>With best regards,
>
>Ewine

-- 
_______________________________________________________________
Tetsuo HASEGAWA, D. Sc.   <tetsuo.hasegawa at nao.ac.jp>
ALMA-J Project Scientist
Professor, National Astronomical Observatory of Japan
2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
Phone +81-422-34-3780 / FAX +81-422-34-3764
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