Sin t

1
Detecting the signature of planets at millimeter
wavelengths
F. Ramos-Stierle, D.H. Hughes, E. L. Chapin
(INAOE, Mexico), G.A. Blake ???
gab_at_gps.caltech.edu
The study of planet formation mechanisms is a
central part of our search for an understanding
of the origin of the Earth and Solar System. The
motivation to study the environments of planet
formation has become more intense since the
discovery of the first giant planets around
nearby solar-type stars using the Doppler
planet-detection technique. One of the most
intriguing results of searches for exoplanets
(and a challenge to the new theories of planetary
formation), is the discovery that the formation
process gives rise to considerable diversity.
Surveys of young stars at infrared and millimeter
wavelengths show that most exhibit thermal
emission from small heated particles distributed
in disks (PROPLYDs) , with properties similar to
those of the young Solar System. Models of their
spectral energy distributions (SEDs) and imaging
indicate disk sizes of tens to hundreds of AU.
These dusty and gas-rich disks are believed to
provide the material for proto-stellar sources,
as well as the reservoirs of mass for the
formation of planetary systems. Although there is
now abundant evidence for the existence of
circumstellar disks around young low-mass stars,
our understanding of the detailed properties of
disks, in particular at distances (lt 30 AU)
associated with planet formation, is still in
its early stages. With the combination of high
angular resolution and sensitivity in new
millimeter experiments (e.g. ALMA and LMT) , we
will be able to image the detailed structure of
nearby disks, and detect the gaps and
inner-holes (both spectrally and spatially)
created by the clearing of material during the
planet formation process.
Modelling the thermal emission from PROPLYDs
We know about the existence of PROPLYDs and
planets, but we are still waiting for clear proof
that both are related. We present optically thin
thermal models of the multi-wavelength emission
from PROPLYDs, to generate realistic simulated
images of the gaps and holes in disks associated
with planet formation. Disks contain a mixture of
gas and dust. Even though the dust mass is 1 (or
less) of the mass in PROPLYD environments,
virtually all the continuum radiation from the
infrared to the millimeter is due to thermal
radiation from dust. Dust warmed by the
starlight radiates as a blackbody modified by the
emissivity of the grains. The dust temperatures
depend on the distance of a grain from the star,
and since a continuous disk contains particles
over a wide range of distances from the star (out
to several hundred AU), dust temperatures range
from the sublimation temperature (approximately
1500 K) to a few Kelvin. The result is a broad
spectrum of thermal emission from 1 µm to 1000
µm.
Link1
Massive planets orbiting a star cause a change in
the radial velocity. This Doppler method
currently provides the most efficient planet
detection method.
The composite SED (black line) from a disk with
thermal emission at different radii, and
different temperatures. The contribution from the
individual annuli are shown in colour.
HST imaging of PROPLYDs (25 to 500 AU) around
YSOs in Orion (D400pc).
Gaps in disks Physical gaps in the disk can be
created by the presence of a proto-planet which
clears dusty and gaseous material. Removing this
material will also reduce the thermal
contribution from the region. The gap will
therefore produce a depression in the SED at
wavelengths that correspond to the temperature of
the missing dust .
Composite SEDs showing the impact of gaps of
different widths which are created in a
continuous disk.
A 15 35 AU gap in the PROPLYD caused by the
clearance of dust due to proto-planets. The
maximum intensity was clipped to show better the
effect.
Inner-holes in disks While only the largest
proto-planets may form gaps of sufficient width
to be imaged directly, smaller bodies can produce
detectable inner-holes once the bulk of disk
material interior to their orbits has been
accreted. After sufficient evolution, the entire
planetary system can clear all material out to
the most distant planet.
Composite SEDs calculated for different sizes of
inner-holes. The stellar contribution is shown in
yellow.
A 40 AU inner-hole caused by the clearance of
dust from the collective influence of all planets
in a young solar system.
Telescope simulations

• Individual detector signals are generated by an
  instrument and telescope simulator2 that passes
  an array of pixels across a composite of the
  "idealised" maps.
• The following effects eare included
• telescope primary aperture
• beam shape
• array geometry and sensitivity
• scan pattern and pointing errors
• atmospheric noise and attenuation
• detector time constant and 1/f drift
• Poisson noise
• integration time

True image of dust emission around e Eri at a
wavelength of 850µm, using SCUBA at the JCMT
(Greaves et al. 1998)3 .
A simulation of dust emission around e Eri at a
wavelength of 850µm, observed with the SCUBA
camera operating on the 15-m JCMT.
Background is a segment of Saturns rings.
In these simulations we tune the configuration of
the interferometer to optimize the synthesized
beam size and sensitivity to the structure of
interest. Left figure We choose a maximum
baseline of 150m (beamsize 1) in order to map
the extended structure of the dust disk, and
measure the total dust mass. Right figure ALMA
observations with longer baselines (3.5km
beamsize 0.06) in order to spatially resolve a
gap in a disk at a distance of 20pc.
A simulated 100AU PROPLYD (D20 pc) at 45
inclination with a gap between 3.2 and 11AU
(corresponding to the clearance by the orbits of
Jupiter Saturn), observed with ALMA for 3hrs
using 3.5km baselines. The lower panel shows a
slice though the disk, clearly showing the
presence of the gaps. The huge intensity peak is
caused by the hot dust located close to the star.

Simulated 100AU PROPLYD (D3pc), at an
inclination 45, with an inner-hole of 40AU,
observed with the BOLOCAM-II camera operating at
1.1mm on the LMT.
This figure shows the same PROPLYD (Mdust 5.5
MC, 5 the initial dust of the minimum
solar-nebula)4 observed at 1.1mm with ALMA using
the smallest baselines (150m).
References 1. http//astron.berkeley.edu/gmarcy/0
39marcy.html 2. Chapin et al. 2001,
astro-ph/109330 3. Greaves et al. 1998, ApJ
506L133-L137 4. Ramos-Stierle 2003, MSc thesis