Title  Probing the Dust Formation Zone around Red Giant Stars
Pi      K. M. Menten
Time   200 hrs

1. Project:  Probing the Dust Formation Zone around Red Giant Stars
===================================================================
1. Name of program:
   Probing the Dust Formation Zone around Red Giant Stars
   Authors  Karl M. Menten

2. Science goal(s)

The closest vicinity of an O-rich red giant star has roughly the following 
radial structure: 

Region                  Outer diameter       T     n    Resolved by
                         (AU)(mas@200pc) (K)  (cm^3)
Optical photosphere:      4     20        2400  2E+14 IR interferometry
chromosphere:             5     25        2000* 5E+13 ---  
molecular photosphere:    6     30        1600  1E+12 IR interferometry
  (e.g. TiO)
radio photosphere:        8     40        1500  1E+11 VLA
SiO masers:               12    60        1300  1E+10 VLA, VLBI
dust formation:         > 12    60        1200  3E+09 IR interferometry
and molecular depletion
* The chromosphere's temperature is highly inhomogeneous with shocks
creating partially much higher temperatures).
(see Fig 12 of Reid & Menten (1997, ApJ, 476, 327 ; hereafter RM97) 
----

So far the ONLY information on densities and temperatures 
in this important region in which molecules condense into dust grains 
comes from models of SiO maser emission, and is, thus, quite uncertain.

In C-rich stars, similar scales are probed by HCN masers,  as well as by
(probably) quasi-thermal vibrationally excited HCN emission. Again,
such observations are difficult to interpret.

Plateau de Interferometry of the low-lying SiO (2-1) transition from the
 vibrational ground state by Lucas et al. (1992, A&A, 262, 491)
has revealed SiO emission regions with  (brightness) temperatures  between a
few and several 100 K and sizes of  40 - 400 AU, much larger and cooler
than the SiO maser regions and definitely outside of the dust formation zone. 
The inescapable conclusion is that enough SiO survives depletion to
still produce extended, optically thick emission.  Because their emission
is optically thick, low excitation lines will do little to probe the 
inner region.   For example, the critical density of the 694.3 GHz 16-15
SiO line (which is 250 K above ground) is 1000 times higher than 
that of the 2-1  line and thus samples 10^8 - 10^9 cm-3 gas, approaching the
densities in the dust formation zone.

Observations at the highest ALMA resolution are easily possible, since
continuum emission in all frequency bands  can , as explained in sect. x.x 
of this document,  be used for self calibration and, also, will provide
the exact stellar position as a reference  point. 

3. Number of sources: 
   Numbers of stars per kpc^3 (Jura & Kleinmann 1992, ApJS, 79, 105
   All carbon                   100
   "Very dusty carbon"           30
   S-type                        30
   O-rich miras (300<P<400 d)   210
   O-rich miras (P<300 d)      35-60
   "very dusty oxygen            30

   This numbers should be regarded as strict lower limits of objects for which selfcal
   is easily possible.   

   Molecules: O-rich: SiO (maser+thermal), 29SiO, 30 SiO, H2O (maser) (others)
              C-rich: HCN, SiS, CS, others (?)


4.  Coordinates: All over the sky
    Expected fluxes (estimates extrapolated from  measured radio data):
    Example: SiO 16-15 line
      S_cont(694 GHz)                          104   mJy *
      Delta S_cont(694 GHz)(10 s)                3.2 mJy  (1 sigma)
      Delta S_cont(694 GHz)(1 h)                 0.17 mJy (1 sigma)
      Delta T_B(SiO[20-19] (1 h, 20 mas beam)   32 K   
      
    Given that the brightness temperature in the region in question it several 
    hundred K, it will be possible to image high excitation lines in envelopes 
    at 20 AU resolution even at 500 pc.
    Of course, for nearer regions, the integration time would be much reduced, e.g.
    by a factor of 25 for D = 100 pc.


      4.2. Moving target: yes/no  (e.g. comet, planet, ...)

           no

      4.3. Time critical: yes/no  (e.g. SN, GRB, ...)

           no

   5. Spatial scales:

      5.1. Angular resolution (arcsec): 
       
           0.010-0.020 for resolution of emission, any for detection/selfcal

      5.2. Range of spatial scales/FOV (arcsec):           
           (optional: indicate whether single-field, small mosaic, 
            wide-field mosaic...)

           continuum only: <1", any for simultaneous line emission

      5.3. Single dish total power data: yes/no

           no

      5.4. ACA: yes/no

           no

      5.5. Subarrays: yes/no

            no

          
   6. Frequencies:

      6.1. Receiver band: all


      6.2. Lines and Frequencies (GHz):
           (approximate; do NOT go into detail of
           correlator set-up but indicate whether multi-line or single line;
           apply redshift correction yourself; for multi-line observations
           in a single band requiring different frequency settings, 
           indicate e.g. "3 frequency settings in Band 7" without specifying
           each frequency (or give dummies: 340., 350., 360. GHz). For projects
           of high-z sources with a range of redshifts, specify e.g.
           "6 frequency settings in Band 3". Apply redshift correction 
           yourself)
 
           any

      6.3. Spectral resolution (km/s):

           4 km/s or better

      6.4. Bandwidth or spectral coverage (km/s or GHz):


   7. Continuum flux density:

      7.1. Typical value (Jy):
           0.
           (take average value of set of objects)
           (optional: provide range of fluxes for set of objects)
           
           30-50   uJy for G and M dwarfs (5-10 pc) at 100 GHz
           300-500 uJy for G and M dwarfs (5-10 pc) at `300 GHz


      7.2. Required continuum rms (Jy or K):

           e.g. 0.5 mJy at 350 GHz
                3 mJy at 680 GHz
           both in 10 s to allow selfcal

      7.3. Dynamic range within image:                  
           (from 7.1 and 7.2, but also indicate whether e.g. weak objects 
            next to bright objects)

            N/A; no nearby weaker objects expected 

   8. Line intensity:

      8.1. Typical value (K or Jy):
           (take average value of set of objects)
           (optional: provide range of values for set of objects)
           hundreds of K

      8.2. Required rms per channel (K or Jy):
           30 K
      8.3. Spectral dynamic range:              
           not too high

   9. Polarization:  no  

   10. Integration time for each observing mode/receiver setting (hr):

       Dictated by 2 h x #lines x #sources

   11. Total integration time for program (hr):

       200

   12. Comments on observing strategy (e.g. line surveys, Target of
       Opportunity, Sun, ...): (optional)


**************************************************************

Review Peter Schilke: Interesting scientifically.  It is not clear
from the proposal if selfcal on continuum can really be used (the
numbers quoted there look like they have been copied from a different
proposal and are of no relevance here).  The time estimate is somewhat
opaque, it is unclear how many lines and how many sources will be
used, and what the integration time per source/line is (here is is
assumed constant independent on source and frequency).
--------------------------------------------------
Review v2.0:
 
1. Project:  Probing the Dust Formation Zone around Red Giant Stars
===================================================================
1. Name of program:
   Probing the Dust Formation Zone around Red Giant Stars
   Authors  Karl M. Menten

DRSP 2 Review Leonardo Testi: The project is vague in the line setup
part. It would be very useful to have this section of the project
developed especially now that we are trying to use the DRSP to
understand the demand on the correlator setups.