[mmaimcal] distant Milky Way?

[Al Wootten]

Bryan Butler writes:
 > 
 > 
 > 
 > simon & all,
 > 
 > i like simon's treatment of CO lines, so i went through the calculation 
 > myself, since i have no experience with this sort of thing.  i went 
 > through it fairly carefully, since i wanted to incorporate a similar 
 > calculation in the antenna size report...
 > 
 > comments are not only welcome, but solicited, since i want to 
 > incorporate a calculation of this sort in the antenna size report 
 > before i release it, and this is about as far away from my realm of
 > science as it gets :)...
 > so, it appears to me that (depending on q_o) we may still be able to do 
 > the higher transitions of CO even out to z=3 or so.  but, as z 
 > increases, you lose the ability to observe the lower transitions.  is 
 > this a critical loss?  i don't know for sure, but if we want to do 
 > "milky way's", then it probably is, since most of the galactic CO is 
 > relatively cold (< 20 K or so?) i think.  bob implicitly points out in 
 > his analysis that as you go to higher z, you just pick different 
 > molecules (CI, CII, NII, e.g.) rather than sticking to CO.  however, it 
 > seems to me that you start to probe different types of material in the 
 > galaxies, so you don't get the same thing...
I'll go over this.  I think you are right that 1-0 will always be hard
to see.  We'll let Leo and his SKA friends have that one.  I don't think it is
what we want anyway.  There can be no Milky Ways so cold as our own at high z 
since the background temperature goes as (1+z)Tbgd(now) I think.  Also, I 
wouldn't worry  about having too many velocity channels for detection as 
there is also the spatial dimension in which one will have adjacent pixels 
offering up the line; there are the projection effects which Min mentioned.
There was the neat trick Scoville et al did with--was it Arp 220--where 
they were able to use the change of velocity from pixel to pixel to
super-resolve the galaxy, extracting much more info than was available
from the dust spectrum, which had no kinematic content.

Onward....I understand that Sue Terebey's 'planet' has a pretty
featureless spectrum.  At a presentation at CfA, I am told, the 
featurelessness was
attributed to veiling by dust (not clear where).  Are there model
atmospheres for hot protoplanets?  This thing should, I think, be
0.1 mJy in the submm.  Beyond existing instruments, but seconds for the
MMA.  Then might not we have a good chance at pressure broadened warm
water, perhaps ammonia or other molecules?  Which ones?  Who would know?

Clear skies,
Al