1. Gas in Protoplanetary Disks
Thomas Henning
Max Planck Institute for Astronomy, Heidelberg
What is what
Frontiers Science Opportunities with JWST, Baltimore, 2011

2. Planet Formation: Stages
In presence of gas
In absence of gas
dust
Dynamical
restructuring
Star & circumstellar (or protoplanetary) disk

3. This Talk __________ How much time do we have to form planets?
Can we find water and organic molecules in disks?
What can we do with JWST?

4. The Disk Structure __________
Small Structures – Low Mass – Low line/continuum ratio

5. The Gas Disks __________ Angular momentum and mass transport
Dynamics of dust and planets (Coagulation/Migration)
Reservoir for the formation of molecules
Wet Formation: Accretion of hydrated
Silicates
Dry Formation: Water delivery later by
Asteroids an comets
Water on Earth
„Wet“ Formation
(Drake 05)
„Dry“ Formation
(Morbidelli et al. 00)

6. 3D Global Stratified MHD Simulation
__________
Radius:1-10 AU
8 pressure
scale heights
Blue Gene/P and Pluto code: Flock et al. (2011)

7. Ionization structure of a T Tauri disk
(Semenov, Wiebe, Henning, 2004, A&A, 417, 93)
__________
Mixed grains
(dead zone)
Sedimentation
See also
Ilgner & Nelson
(2006, 2007)
„Layered“ vertical structure

8. Disk mass and planet mass
Mplanet=0.5 Mdisk
Planet mass [Jovian masses]
Maximal planet
mass increases
with disk mass.
Log(Mdisk/MMSN)
Mordasini et al. , submitted.

9. __________ PAHs in Protoplanetary Disks (Geers et al. 2007, RR Tau)
(Acke, Bouwman, Juhasz,
Henning et al. 2010)

10. Dust and Gas Disk Lifetimes
__________
Haisch et al. (2001), Hernandez et al. (2008), …
Fedele et al. (2010), …

11. Gas Disk Lifetimes < 10 Myr
__________
FEPS Spitzer Legacy IRS survey
20 stars with ages Myr
=> No gas rich disks
(> 0.1 MJup) detected.
In recent UV observations they get 10-6 as a limit (Ingleby et al. 2009)
Hollenbach et al. (2005),
Pascucci et al. (2006)
See also: Ingleby
et al. (2009)

12. Different stages of disk evolutionH
V(km/s) log(/ m)
Typical CTTS H
~ 10 Myr ~1 Myr
V(km/s) log(/ m)
Flattened, accreting disk H
V(km/s) log(/ m)
Non-accreting TO

13. A molecular disk at its edge
HD A
This is a spectrum of a young star HD A at CO fundamental band at 4.7 um.
The star is known to have a circumstellar disk, and for the first time, the inner most part is one dimensionally
Imaged by the CO line emission. The CO emission lines are spatially extended as much as 50 AU at both sides of the star. And after subtracting the stellar continuum, the presence of inner cavity is uncovered. The size of the cavity is matched to the gravitational radius of the star, which strongly indicates that viscous accretion has evacuated the cavity together with photoevaporation.
CO emission at 4.7 μm
Gas in Keplerian orbit
Inner cavity (r~11 AU)
Coming closer to the star than HST
Goto et al. (2006)

14. LkCa 15 – The SEEDS Collaboration
Offset between nebulosity center and star suggests eccentric outer disk; this is expected from dynamical influence of planets, and hard to explain otherwise.
What physical object is it that we see as a bright crescent? Two possibilities:
Illuminated wall of the disk on the far side.
Forward-scattering on near-side disk surface.
Thalmann et al. 2010
Inner truncation radius at 46 AU
Espaillat et al. 2008
Thalmann et al. 2010 14

15. Disk Chemistry __________ __________
Large range of temperatures and densities
Importance of stellar and interstellar radiation fields
Ionization and heating sources:
Cosmic rays, UV radiation, X-rays, extinct radionuclides
Strong coupling between chemistry and dynamics
(ionization, temperature structure, cooling)
__________
Chem and Dyn are connected such that Dyn is related to ionization state of a disk, which in turn depends on Chem
Dust and gas strongly coupled …
__________

16. Disk Structure ~1000 AU 0.03 AU 100 AU ~500 AU
Observable region with interferometers
~1000 AU
IS UV, cosmic rays
hν, UV,
X-rays
Snowline
(T=100K)
photon-dominated layer
warm mol. layer
Only region r> AU is accessible with (sub)mm-interferometers
“Sandwich”-like 3-layered structure: cold midplane (freeze-out), warm inermediate layer (mild UV, X-ray, rich chemistry, lines!), surface (only simle species/atoms)
Accretion is thought to be driven by the so-called magnetorotational instability (next slide)
cold midplane
accretion
puffed-up
inner rim
turbulent mixing
0.03 AU
100 AU
~500 AU

17. How to produce simple hydrocarbons?
__________
radiative association
reactions with C
Atomic oxygen is a poisson
Gas-phase chemistry allows to build up simple molecules
that can later freeze out or are ‘used’ to form larger species

18. Spectroscopy - An Essential Tool
ISO SWS disk spectrum of the Herbig Ae star HD (Malfait et al. 1998) and comet Hale-Bopp (Crovisier et al. 1997) for comparison
DRM Documents, MISC Report,
August 22nd, 2001
(Background)
Apai et al. (2005); Flux at mJy level
Pontoppidan et al. (2005)

19. H2 is a challenging molecule to detect Rotational lines between
5.05 µm and µm
H2 has rotational lines between 5.05 and microns
Bitner ea. (2007, AB Aur)
Martin-Zaidi ea. (2009, HD 97048)
See also Carmona ea. (2008)
Not sensitivity, but disk structure!
We use tracers for obtaining
information about the gas.

20. The Disk Tracers
Atomic and ionic fine structure lines ([NeII], [SiII], [SI], …)
Diagnostic features of PAHs (11.3 microns) and dust grains
Molecular lines (H2, H2O, CO2, …)
(Gorti and Hollenbach 2008, Star of 1 Ms)

21. Observational constraints
UV: H2 emission from hot inner disks
Optical wavelengths: [OI] emission
IR: H2, CO, H2O, OH, … in warm inner disk (1-10 AU)
and molecular ices in outer disk, key organic species
CH4 (7.7 µm), C2H2 (13.7 µm), HCN (14.0 µm)
FIR: CO, OH, … in warm outer disk surface
(Sub)mm: CO and isotopes, HCO+, DCO+, CN, HCN,
DCN, HNC, N2H+, H2CO, CS, HDO (?), CH3OH, CCH
in cold outer disks (»10 AU)
__________
Submm observations need interferometers – Sensitivity limited (ALMA required)

22. Spectroscopy at sub-mm wavelengths
__________
Dutrey et al. 1997
PDBI:
Dutrey ea. 07, Schreyer ea.08,
Henning ea. 10, ….
Öberg ea. 10, 11
Thi et al. 2004;
Kastner et al. 1997

23. Molecular Abundances in Disks
__________
Elevated ratio of CN/HCN indicates PDR-like chemistry
Strong depletion of gas-phase species: radiation or freeze-out?

24. __________ IR Spectroscopy Reveals Complex Chemistry
700 K K K
(Lahuis et al IRS 46 in Ophiuchus; Variable)
see also Gibb et al for GV Tau)
GV Tau (Haro 6-10)
Strong absorption due to HCN, C2H2, CO (all warm) towards the primary
HCN/CO = 0.6%
C2H2/CO=1.2%
CH4/CO= 0.37%
HCN and C2H2 detected around a young low-mass star
T ≳350 K
Abundances several orders of magnitude higher than ISM dark clouds
Production in inner (< 6 AU) disk or wind

25. Organic Molecules and Water
What is what
Pascucci et al. (2009)
Carr & Najita (2008)
N atoms from
photodissociation of N2
Diversity in inner disk atmosphere chemistry
(e.g. Pontoppidan ea. 10, Carr & Najita 11, Teske ea. 11)

26. Water in Protoplanetary Disks
Dominant line-cooling of inner disk surfaces (~10-4 Lsun)
(Pontoppidan et al. 2010)
No H2O, but OH detection in Herbig Ae/Be disks –
Photodissociation of water by FUV photons
(Pontoppidan et al. 2010, Fedele et al. 2011)
Mid-infrared lines come from ~1 AU
with rotional temperatures between
500 and 600 K
No detection of colder water vapor in
outer disk regions with Herschel
(Bergin et al. 2010)
What is what
VLT/VISIR: Pontoppidan ea. (10)

27. Water Formation: T < 100 K
Appropriate for outer disk (r ≳ 10 AU)
Dominated by photodesorption on disk surface (Dominik et al. /Hollenbach et al.)
Less than 1% of cosmic oxygen placed in H2O
UV photon has to find a grain - water vapor abundance depends on <ngrσgr> O
H2O OH γ
ion-molecule reactions Og gr
OHg
H2Og Hg γ

28. Dust Evolution and Water Abundance
Vasyunin, Henning et al. (2011)
Abundance of water is getting higher in mid-plane and in intermediate warm disk layer. Maximum of abundance shifts deeper into the disk which may prevent water vapor from being observed.

29. HD 100456 with Herschel CO, [OI], [CII], CO, H2O, CH+, …
What is what
Sturm, Bouwman, Henning et al. (2010; see also Thi et al. 2011)

30. Key Science Questions for JWST
Inner Gaps and Radial Structure of Outer Disks
Vertical Disk Structure (Gas-Dust Physics and Chemistry)
Content of Water and Organic Molecules in Disks
Fukagawa et al. 2004

31. Disk structure
Spectroscopy
Imaging

32. Dust settling revealed by imaging
PAH
Image in PAH and dust continuum bands

33. Imaging gaps in transitional disks
VLT VISIR image
8.6 PAH
11.3 PAH
19.8 mm large grains
IRS48
SR 21
Geers et al. 2007
Ratzka et al. 2007
Brown et al
Pontoppidan et al. 2008
Eisner et al. 2009
Thalmann et al. 2010
Examples of disks known to have big enough gaps (~40 AU) to resolve with MIRI imaging and IFU

34. Vertical Protoplanetary Disk Structure
Mid-IR gas lines trace various depths in the disk
(temperature and density profiling)
Gas-dust physics (e.g. sedimentation) and thermal structure
Key factors:
Stellar irradiation characteristics, grain/PAH evolution, chemistry
Surface density and disk mass kept constant; Dashed lines:
AV=1, 10 mag contours

35. Uniqueness of MIRI/MRS
[Fred Lahuis]
High spectral resolution, high sensitivity, continuous  coverage:
line-to-continuum ratio sufficient to detect minor species (res: )
extend studies to faint brown dwarf disks 10m)

36. Inventory of Organic Molecules in Disks of Various Evolutionary Stages
Key organic molecules such as CH4, C2H2, HCN, …
Sample can be based on previous characterization with
Spitzer/IRS, Herschel/PACS and Herschel/HIFI
HNC, CH4, CH3,
C2H6, CH3OH, …
to be detected
with MIRI

37. The Water Reservoir MIRI water lines come from an inner dense region
Woitke et al. (2009)
The Power of the MIRI IFU
F. Lahuis

38. Conclusions __________ __________ Rapid dust and gas evolution
Rich molecular chemistry in planet-forming disks
Diversity in abundance of organic species
Transition disks and exoplanets
Bright future: ALMA, 30-40m class telescopes, JWST
__________
__________

39. MIRI Science Disk Team Imaging and Spectroscopy of PP Disks
M. Barlow, D. Barrado, W. Benz, J. Blommaert, A. Boccaletti, J. Bouwman, L. Decin, A. Glauser, M. Güdel, Th. Henning, I. Kamp, P.-O. Lagage, F. Lahuis, G. Olofsson, E. Pantin, J. Surdej, T. Tikkanen, E. van Dishoeck, H. Walker, R. Waters, B. Vandenbussche ISO+Spitzer+HST+Chandra+Herschel+VLT/VLTI+IRAM/JCMT/SMA/VLA+Modeling