ALMA Timeline

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ALMA Timeline
The Atacama Large Millimeter Array
ALMA Specifications
ALMA Median Sensitivity(1 minute AM1.3 PWV
1.5mm)

• Design and Development Phase Jun 1998 - Dec 2001
• International partnership established 1999
• Prototype antenna contract Dec 99
• ALMA/NA delivered to VLA site Q2 2002
• ALMA/EU delivery Q2 2003
• Construction 2002-2010
• Production antenna contract Q4 2004
• Production antenna in Chile Q4 2005
• Interim operations fourth quarter 2007
• Construction ends 2010

Formation of Stars

• Paradigm material falls through a rotating
  circumstellar disk onto a forming star from more
  extensive envelope, fuelling a bipolar flow which
  allows loss of angular momentum (see HH30 disk,
  far right at best current resolution).
• Without sufficient resolution, separation of
  these motions is difficult
• A key observation, not currently achievable,
  would be to observe the infalling gas in
  absorption against the background protostar. As
  molecular depletion may occur in the densest
  regions (c.f. NH3 in IRAM04191 at left)
  sensitivity is critical to detection ALMA will
  easily provide the sensitivity for this.
• In the bipolar flow, shock waves process envelope
  molecules, providing a rich chemistry--ALMA will
  be able to observe the progress of these shocks
  in real time and study how their composition
  changes.

HH 30 Overlay of the integrated 13CO 2-1
emission (contours) on the HST/WFPC2 image
(color). A cross marks the position of the 1.3
mm continuum source. Stapelfeldt and Padgett
(2001) inWootten, A., ASP Conf. Ser. 235 Science
with the Atacama Large Millimeter Array, 163.
CO(2-1) contours superimposed on an HST image of
HH 30. The HST observations in false colors (from
Burrows et al. 1996) show the optical continuum
emission tracing the reflected light in the
flared circumstellar disk, together with the
emission of bright atomic lines (SII, Ha,
OI), tracing a highly collimated jet,
perpendicular to the disk. The contours represent
the CO(2-1) emission, as observed with the IRAM
Plateau de Bure interferometer with an angular
resolution of 1.20.7 by Gueth et al. in prep.
Only the channel map at a velocity of 11 km/s is
plotted (contours are 80 mJy/beam). It shows the
conical molecular outflow emanating out of the
disk and surrounding the jet. The cross indicates
the position of the peak of the 1.3 mm continuum
emission.
IRAM04191. Green NH3 (1,1) VLA Red/Blud 12CO
2-1 NRAO 12m
Debris Disks
Protoplanetary Disks

• Tdust at 1 AU 350 K
• Tdust power law index q 0.45
• Surface density power law index 1.3
• Inclination 45 degrees

Feature Amplitude Radius (AU)
Width (AU) PA (deg) Dark Ring
1.0 7
2 Dark Ring 2.0
16
4 Planet Debris 1.5
40
5 45 Planet Debris
3.0 60
9 155
The model is a simulated modestly-bright debris
disk at a distance of 12 pc located around a
Sun-like star. The observing frequency is 345
GHz, at which the total emission is 10 mJy. The
disk has an inner radius at 3 AU and an outer
radius at 125 AU, with a mass of roughly 0.4
lunar masses of dust. This is a fairly dusty
system, of which perhaps a dozen might be
available.
Modeling Lee Mundy
ALMA will be able to trace the chemical evolution
of star-forming regions over an unprecedented
scale from cloud cores to the inner circumstellar
disk. At spatial resolution of 5 AU, it will
determine the nature of dust-gas interactions the
extent of the resulting molecular complexity, and
the major reservoirs of the biogenic elements.
Angular resolution will exceed that of the HST.
On the right above, a model image on the left a
simulation of how ALMA will image the model.
ALMA Simulation of Debris Disk Image Fidelity
Simulation Structural Details

Simulations of an ALMA observation of the debris
disk using multi-scale CLEAN in the aips
package. On the left, an observation with the
compact array, stretched to show the structures
in the disk in a four hour integration. On the
right, a 4 hour observation with the 450m array,
which achieves higher resolution. Thermal noise
limits sensitivity. A combination of these two
observations would afford the best representation
of the original image. Clearly, in one transit
ALMA would be able to constrain 1) the
photospheric flux of the central star (not
resolved from inner dust in these compact
configurations), 2) the general structure of the
disksuggesting the presence of planets and 3)
the total dust mass of the disk, as all of the
flux is recovered in the image.
ALMA Memo No. 386 387
The debris disk model is spread over several
primary beamwidths of the ALMA antenna. Imaging
the disk would pose a problem for current
interferometers, which do not recover short
spacing data from the antennas operating as
single units. ALMA will incorporate this data to
provide high fidelity images. The simulation
results shown above use software developed at
IRAM with image reconstruction using a CLEAN
technique. The simulations is done for a
frequency of 230 GHz with ALMA in its most
compact configuration, so the resolution provided
is a bit over one arcsecond, insufficient to show
the fine detail in the model. Thermal noise has
not been included in this simulation. Image
fidelity is the ratio of the model to the
difference (model simulated) image, so higher
numbers reflect more accurate quality. On the
right, cumulative fidelity is plotted and
evaluated for four fidelity medians. For a wide
range of medians, the fidelity measure lies near
100, showing that ALMA images will be of quite
high quality indeed. Further improvement of the
images is possible by the addition to ALMA of a
small (12) array of smaller (7-8m) antennas,
outside the scope of the current project but a
likely enhancement should a third partner join
ALMA.