CO Emission in the Millimeter Array Deep Field -- Wootten and the folks at MAMAImCal
NB MAMA=Mother of All Millimeter Arrays, Fred Schwab's proposed name.
MMA/LSA 350 GHz continuum simulation plotted in pseudo-color
with a linear stretch. The background rms is 0.01 mJy, the image
resolution (beam) is 1.1 arcseconds, and the field
size is 2.56 arcminutes square. The assumed cosmology
and evolution match the model Peak-5 of Blain et al. (1999)
(astro-ph /
9806062). For illustration, the galaxies were simulated by 20 kpc
diameter uniform disks. Three specific galaxies are starred and discussed
below. |
The same simulation, except that galaxies in redshift bins have been
assigned different color channels: red: z > 3; green: 1.5 < z
< 3; and blue: z < 1.5. The image stretch is linear, and the
simulated noise appears as grey. In this Universe, Ho=75, qo=0.5.
|
Earlier simulations. Follow this link
to Jack Gallimore's previous work.
To do list:
- More extensive testing of the algorithms wouldn't hurt.
- Check the math on the cosmology.
- Need to consider realistic source sizes and possible evolution with redshift?
- Possibly allow the morphology of the sources to vary?
- Vary the cosmology & evolution parameters.
- Predict CO intensities, using fluxes=>Mdust=>MH2=>Mgal=>dV + inclination => linewidth
|
The latest source code:
| cosmo3.f
|
Performs all of the source counts as a function of
redshift. Inputs are through the file cosmo3.par. The output file, cosmo3.dat,
can be used as input for cosmoplot3.
|
| cosmoplot3.f
|
Generates FITS images based on the output of cosmo3. Inputs are
through the file cosmoplot3.par. This version of the
code allows convolution with a circular Gaussian beam and the addition
of Gaussian noise. Compilation requires the fitsio
library for FORTRAN and the Numerical Recipes subroutines ran1,
gasdev, rlft3, and
fourn . |
| nsvs.f
|
This code simply checks the source counts, N(>S) as a function
of S, based on output from cosmo3. Requires the Numerical Recipes
subroutine indexx. |
|
Jack's program produced the image above; I added some output statements
in order to produce a list of the galaxies in that image and their
characteristics--position, inclination, size, z and flux density, which is
where my statements below come from.
Using the luminosity distance, and these parameters I derived a dust mass
for the emitting 'galaxy' using the recipe in Downes et al. 1992 (ApJ398 L25).
This checks with the F10214 parameters. It appears that a good estimator of
the total H2 mass is MH2 ~ 500 - 700 Md (Downes, Solomon and Radford 1995 (ApJ 453
L65) for F10214 at least. The dynamical mass of stars plus gas is perhaps
50% larger. Boldly assuming that these parameters apply to all galaxies,
we have the numbers which we need for calculating detectability of various
lines.
For CO I calculated L'(CO) using the formulation in Solomon, Downes and
Radford (1992). This directly gives the CO flux at some transition
simply by multiplying by the intrinsic brightness temperature ratio of the
lines; I'll take Simon's gross assumption that all lines of interest have
the same brightness temperature for now but I may employ Harvey's
calculations to improve this estimate.
For 64 x 12m antennas at 850 GHz I estimate that one hour one sigma in
250 km/s will be 15 mJy km/s so that 5 sigma will be 75 mJy km/s. I can
then confront this sensitivity with the galaxies in the image.
It appears to me that a sizable fraction (~75%) of the galaxies detectable in
our paradigm image would be detectable in CO also. About 16% of the galaxies
might have lines which are detectable and actually fall within the passband
of the image formed by a 64 x 12m array. I am working on the corrections for
surface brightness (1"=5kpc at 12 Gpc (z=2.3) so this may not be a large
correction) and inclination (assuming random orientations).
Jack used a 20 kpc disk for the galaxies. Looking over the literature
it seems to me that 5kpc or smaller might be more appropriate for the
CO-bright parts of galaxies. Simon or Min what do you think? We have a 1.1"
beam so in this case the corrections will be minimal. I used the estimate
of the dynamical mass of a galaxy as guesstimated above to arrive at its
intrinsic linewidth; I know the inclination so this will allow me to
estimate linewidth and the actual detectability of a galaxy.
Ignoring linewidth for the moment, let us see a pie diagram--z as the
radial coordinate with RA as the angular coordinate, with declination
collapsed--showing the galaxies that will be detected in a line. Included
here are all CO lines from J=3->2 (none) to J=17->16. I also include
CII and NII with the assumption that they will be no brighter than the CO
lines, a fairly safe assumption I believe.
|
|
|
Ignoring linewidth for the moment, let us see a pie diagram--z as the
radial coordinate with RA as the angular coordinate, with declination
collapsed--showing the galaxies that will be detected in a line. Included
here are all CO lines from J=3->2 (none) to J=17->16. I also include
CII and NII with the assumption that they will be no brighter than the CO
lines, a fairly safe assumption I believe. 352 galaxies are bright enough
to be detected in some line or combination of lines in several hours
integration.
|
Four 'galaxies' are starred above. Three are relatively bright, while
one is at the limit of detection for CO in two hours.
Galaxy 'A' is near the top to the right. It lies at z=1.94 (Dl=9.8 Gpc)
at an inclination of 90 degrees with phi=35 degrees and is blended
with a galaxy about 30 times weaker at z=1.78. A emits 1.06 mJy at
345 GHz, and so has a dust mass of
1.3 x 10(7) solar masses. We estimate that L'(CO)= 1.6 x 10(9) K km/s pc^2.
The CO line intensity is therefore 1.6 Jy km/s, which can easily be detected
in very little time. The J=9-8 line lies within the bandpass of the
image. The galaxy is barely resolved, with a size of 1.219 x 1.201
arcsec; peak flux is .9 mJy.
Galaxy 'B', on the western edge, lies at z=3.25 (Dl=17.5 Gpc) at an
inclination of 17 degrees and phi=-11 degrees, hence is nearly face on.
It is blended at 1" with a galaxy 20 times weaker than its 5.5 mJy flux
which is at z=4.59. The dust masses of the two galaxies are 4 x 10(7) solar
masses for B and 1.4 x 10(6) solar masses for its blend.
We estimate that L'(CO)= 5 x 10(9) K km/s pc^2.
The CO line intensity is therefore 4.6 Jy km/s, which can easily be detected
in very little time. It is resolved, with a size of 3.382 x 3.048
arcsec; peak flux is .6 mJy owing to the extension. For its companion
the CO line intensity is 0.17 Jy km/s; this will also be detected should the
placement of the channels in the spectrum be appropriate for one of the
CO lines. The 205 micron NII line lies just outside of the bandpass, which
covers z ranges of 3.077 - 3.17 and 3.27 - 3.36 in the two sidebands.
Galaxy 'C' lies near the center of the image at z=2.98 at an inclination
of 75 degrees and phi of -30 degrees, hence is less face-on than either of
the preceding galaxies. It is unblended, emitting 1.75 mJy for a dust mass
of 1.4 x 10(7) solar masses. We estimate that L'(CO)= 1.7 x 10(9) K km/s pc^2.
The CO line intensity is therefore 1.6 Jy km/s, which can easily be detected
in very little time. It is resolved, with a size of 3.005 x 1.390 arcsec;
peak flux is .47 mJy.
Galaxy 'D' was chosen to lie at the limit of detectability. In fact, it is
very hard to pick out in the image. It lies at z=1.94 with an inclination
of 22 degrees and phi=0 degrees, unblended with nearby galaxies. In the
continuum it emits .037 mJy for a dust mass
of 4.5 x 10(5) solar masses. We estimate that L'(CO)= 5.6 x 10(7) K km/s pc^2.
The CO line intensity is therefore 0.055 Jy km/s, which might barely be detected
in two hours. The J=9-8 line lies within the bandpass of the
image. The galaxy is unresolved.
Ways out:
NRAO Charlottesville Homepage
Al's MMAImCal Homepage
Jack's Homepage
Changed by: Al Wootten 11-Mar-1999