Transcript 11Oct2004 - Division of Geological and Planetary Sciences

Gas & Ice in Protoplanetary
and Debris Disks
HD 141569A
(HST ACS)
Geoffrey A. Blake
Div. Geological & Planetary Sciences
15th UMd Symposium
11Oct2004
Study Isolated Disks (Weak/No Outflow)
Planet
building
phase
Beckwith & Sargent 1996, Nature 383, 139-144.
11Oct2004
Why do we care about gas & ice in disks?
Disk-star- and
protoplanet
interactions lead
to migration
while the gas is
present. Coreaccretion & ice?
Theory
1 AU at 140 pc
subtends 0.’’007.
Jupiter (5 AU):
V_doppler = 13 m/s
V_orbit = 13 km/s
Simulation G. Bryden
Observation?
Spectroscopy of “Disk Atmospheres”
G.J. van
Zadelhoff
2002
Chiang &
Goldreich
1997
IR
disk surface within several – several tens of AU
(sub)mm
disk surface at large radii, disk interior
11Oct2004
The 1-Baseline Heterodyne Interferometer:
Geometrical delay
•HST resolution at 1mm
D=10 km! Use array.
•Can’t directly process 100 –
1000 GHz signals.
•Heterodyne receivers detect
|V| and f, noise defined by
the quantum limit of hn/k.
•Positional information is
carried by the PHASE.
•Spectral coverage depends
on the receivers, while the
kinematic resolution is
determined by correlator.
11Oct2004
The n-Element Heterodyne Interferometer:
•n(n-1)/2 baselines,
imaging performance
depends on the array
geometry, but
•For small to moderate
n, the (u,v) plane is
sparsely filled.
•For a given array, the
minimum detectable
temperature varies as
(resolution = qS)-2 :
qP = primary telescope beam
11Oct2004
CO traces disk geometry, velocity field:
CO 3-2
TW Hya w/SMA
Qi et al. 2004,
ApJL, in press.
Disk Ionization Structure: CO and Ions
Disk properties vary widely
with radius, height; and
depend on accretion rate,
etc. (Aikawa et al. 2002, w/
D’Alessio et al. disk models).
Currently sensitive only to R>80 AU
in gas tracers, R<80 AU dust.
CO clearly optically thick, isotopes reveal
extensive depletion, poor mass tracer!
The fractional ionization is ≥10-9, easily
sufficient for MRI transport.
Are there gas probes of the disk midplane?
If depletion is extensive, what
species might be able to probe
the disk midplane? One possible
route involves deuterated ions
such as H2D+:
Van Dishoeck et al. 2003, A&A 400, L1
The abundances of
these ions may be
difficult to quantify,
however, and so
SOFIA/Herschel
studies of HD J=1-0
at 112 mm are
eagerly awaited!
Ceccarelli et al. 2004,
ApJ 607, L51
TW Hya
TMB (K)
vLSR (km/s)
Chemical Imaging of Outer Disk?
Qi et al. 2004
& in prep
HDO formed via H2D+,
possible tracer of H3+?
Kessler et al.
2004, in prep
(6 transits)
CO well mixed, while
Photodesorption?
[CN]/[HCN] traces
enhanced UV fields, esp.
Ly a. Is LkCa 15 unusual?
Transitional/Debris Disks?
HD141569 & Vega w/PdBI:
Vega, Wilner et al. 2002 (dust)
CO 2-1 from HD141569
J.-C. Augereau & A. Dutrey
astro-ph/0404191
Future of the University Arrays – CARMA
01Oct2004
CARMA = OVRO (6 10.4m) + BIMA (9 6.1m) + SZA (8 3.5m) arrays
SUP approved!
2004 SZA at OVRO
2004 move 6.1m
2004 move 10.4m
2005 full operations
March 27th , 2004
Cedar Flat 7300 ft.
Disk Observations w/CARMA+ALMA
CARMA
ALMA
Md=0.01Msun Rout=120AU Ro=20AU
HDO:
rms (3sigma) = 0.05-0.1 K
(CARMA w/D config. in 4 hrs)
Dust simulation (L.G. Mundy), realistic
phase errors, but no CLEAN/MEM.
How can we probe the planet-forming region?
Theory
(pre-ALMA) The
size scales are too
small even for the
largest current &
near-term arrays.
Spectroscopy to
the rescue!
Jupiter (5 AU):
V_doppler = 13 m/s
V_orbit = 13 km/s
Observation?
High Resolution IR Spectroscopy & Disks
R=10,000-100,000 (30-3 km/s) echelles
(ISAAC,NIRSPEC, PHOENIX,TEXES)
on 8-10 m telescopes can now probe
“typical” T Tauri/Herbig Ae stars:
Keck
CO
M-band
TW Hya
NIRSPEC
R=25,000
L1489
IRS
Spitzer can study edge-on disks!
VLT
The small molecules in ices are
similar in protostellar envelopes
and disks.
11Oct2004
Flux (Jy)
VLT
ISAACS
What about other gaseous species w/echelles?
NGC 7538 IRS9
Boogert et al. 2004, ApJ, in press
11Oct2004
In older/inclined systems, CO disk emission:
Herbig Ae stars, from
~face-on (AB Aur) to highly
inclined (HD 163296).
CO lines correlated with
inclination and much narrower
than those of H I
Disk!
CO lines give distances slightly larger
than K-band interferometry, broad H I
traces gas much closer to star (see also
Brittain & Rettig 2002, ApJ, 588, 535;
Najita et al. 2003, ApJ, 589, 931).
Can do ~20-30 objects/night.
Pf b
Systematic Line Width Trends:
•Objects thought to be ~face
on have the narrowest line
widths, highly inclined
systems the largest.
•As the excitation energy
increases, so does the line
width (small effect).
•Consistent with disk
emission, radii range from
0.5-5 AU at high J.
•Low J lines also resonantly
scatter 5 mm photons to
much larger distances.
•Asymmetries (VV Ser)?
Blake & Boogert 2004, ApJL 606, L73.
11Oct2004
How is the CO excited in these disks?
CO
13
CO
CO and 13CO rotation diagrams
show curvature as a result of
t>1. Still, small amounts of gas
since N(H2)~5 x 1022 leads to
dust opacities near unity.
Collisional excitation important,
but cannot explain line widths
at low J values (too broad).
Resonant IR scattering
at larger radii!
The vibrational excitation is
highly variable, likely due to
variations in the UV field.
Disk shadowing?
11Oct2004
Where does the CO emission come from?
Flared disk models often possess
2-5 micron deficiency in model
SEDs, where a “bump” is often
observed for Herbig Ae stars.
Dullemond et al. 2002
Explanation:
Dust sublimation near
the star exposes the
inner disk to direct
stellar radiation,
heating the dust and
“puffing up” the disk.
11Oct2004
CO Emission from Transitional Disks?
For dust sublimation
alone, the lines from T
Tauri disks should be
broader than those from
Herbig Ae stars+disks.
Often observed, but…
Calvet et al. 2002
The TW Hya lines are extremely
narrow, with i~7°
R≥0.4 AU.
Similar for SR 9 and DoAr 44, but
gas radius << dust radius (SED)?
Recall hnCO ≥ 11.09 eV to dissociate.
Gas Tracers in Debris Disks? What about H2?
Controversial ISO SWS
studies were in LARGE
beams, truly disk emission?
TEXES,
Richter et al.
(2004), in
preparation.
Spitzer IRS?
TEXES/IRTF ground based follow
up has now detected H2 in cTTs,
narrow & point-source like. Debris
disks studies need 8-10m! (2005B)
Calvet et al. 2002
Disk Spectroscopy - Conclusions
AB Aur
(Sub)mm-wave instruments can only study the
outer reaches of large disks at present in lines;
even at these wavelengths the disk mid-plane is
largely inaccessible due to molecular depletion.
Expanded arrays (CARMA, eSMA, ALMA)
will provide access to much smaller scales,
lines may selectively highlight regions of
planet formation. Midplane w/H2D+ and HD?
HD 163296
High resolution IR spectroscopy just starting,
is immensely powerful, and provides unique
access to the 0.5-50 AU disk surface before
advent of ALMA, large IR interferometers.
Spectra are esp. sensitive to disk geometry.
Spitzer is providing beautiful spectrophotometric
SEDs and many new targets!
11Oct2004
OVRO CO(2-1) Survey of T Tauri stars
(Koerner & Sargent 2003)
• stellar ages 1 - 10 Myrs
• stellar masses ~ 1 M
• selection by 1 mm flux, SED
characteristics
• Taurus 19/19 detections
• Ophiuchus 4/6 detections
• resolution ~ 2”
20 objects
radii  150 AU
masses  0.02 M
(from SEDs)
See also Dutrey, Guilloteau,
& Simon, Ohashi
Understanding Disk Chemistry
Molecular line survey
UV fields
grain reactions
disk ages and evolution
Chemical / Radiative Transfer Modeling
Physical model: D'Alessio et al. 2001
Chemical model: Willacy& Langer 2001
Radiative transfer: Hogerheijde & vander Tak 2000
MM-Wave CO Traces Dynamics, Others?
D. Koerner & A.
Sargent OVRO, in
Qi et al. (2004).
Measure:
R_disk
M_star
Inclination
w/resolved
images.
Dutrey et al. 1997, IRAM 30m
LkCa 15
15
LkCa
11Oct2004
OVRO+CSO/JCMT MM-Wave Disk Survey II
van Zadelhoff et al. 2001
Combine 3/1.3 mm array images w/higher J spectra to
constrain OUTER disk properties, chemical networks.
11Oct2004
UV Fields: HCN and CN
Source
L* (L)
LkCa 15
0.72
GM Aur
0.80
MWC 480
30.2
HD 163293 35.2
CN/HCN Hdust/hgas
~ 10
1.0
<< 1
4.0
~4
1.7
>> 50
LkCa 15
Molecular distribution
ring-like?
Photochemistry
or desorption?
Qi et al., in prep
11Oct2004
[CN]/[HCN] traces
enhanced UV fields
(Fuente et al. 1993,
Chiang et al. 2001)
Modeling the effects of (uv) Sampling
Model Parameters
i = 58°, Vturb= 0.1 km/s
Ro= 5 AU, Rout= 430 AU
nCO = 10-4 nH (D'Alessio 2001)
qsyn = 3.6” x 3.6”
9.5
8.9
8.2
7.6
6.9
5.6
5.0
4.3
3.7
3.0
Infinite resolution, complete UV coverage
LkCa15 ___
model - - -
CO 2-1 fit
Observed UV sampling, uniform weighting
6.3
Atmospheric Phase Correction (mm Adaptive Optics)
•Atm. fluctuations (mostly
H2O) can vary geom. delay.
•|V|eif
decorrelation
if Ef>p (each baseline).
•If the fluctuations vary
systematically across the
array, phase errors ensue.
•Problem is NOT solved.
OVRO WLM
System
Enter ALMA:
Dust simulation (L.G. Mundy), realistic
phase errors, but no CLEAN/MEM.
Superb site & large
array
exceptional
performance (64 12m
telescopes, by 2012).
Llano de
Chajnantor; 5000
m, good for
astronomy, tough
for humans!
Ices in the disk of L1489 IRS
•
Prominent band of solid CO
detected toward L1489,
originating in large, flaring disk.
• CO band consists of 3
components, explained by
laboratory simulations as
originating from CO in 3 distinct
mixtures:
1 'polar' H2O:CO
2 'apolar' CO2:CO
[NEW!]
3 'apolar' pure CO
(Boogert, Hogerheijde & Blake, ApJ 568,761, 2002)
Ices toward young low mass stars
HH 46 w/IRAC, IRS
Keck/VLT
+Spitzer
Boogert et al. 2004, ApJS 154, 359
11Oct2004
SED Fits versus IR Interferometry
Fits to AB Aur SED yield an
inner radius of ~0.5 AU (and
0.06 AU for T Tau).
(Monnier & Millan-Gabet 2002, ApJ)
Dullemond et al. 2002
This model can now be
directly tested via YSO
size determinations with
K-band interferometry.
Intense dust emission pumps
CO, rim “shadowing” can
produce moderate T_rot.
Future “Near”-IR (1-5 mm) Spectroscopy
Brittain & Rettig 2002, Nature
Many other species and disk types
(transitional, debris, etc.) should be
examined in both absorption (edge-on
disks) and emission, but extremely
high dynamic range will be needed.
Protoplanet tracers?
H2, H3+, CH4, H2O, OCS...
Line profile asymmetries?