Gas in Protoplanetary DisksGas in Protoplanetary Disks
Thomas HenningMax Planck Institute for Astronomy, Heidelberg
Frontiers Science Opportunities with JWST, Baltimore, 2011
Planet Formation: StagesPlanet Formation: StagesS
tar
& c
ircu
mst
ella
r (o
r p
roto
pla
neta
ry)
dis
k
Dynamicalrestructuring
In presence of gas In absence of gas
dust
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?
The Disk Structure
Small Structures – Low Mass – Low line/continuum ratio
The Gas Disks
• Angular momentum and mass transport
• Dynamics of dust and planets (Coagulation/Migration)
• Reservoir for the formation of molecules
Water on Earth
• „Wet“ Formation (Drake 05)
• „Dry“ Formation (Morbidelli et al. 00)
3D Global Stratified MHD Simulation
Radius:1-10 AU
8 pressure scale heights
Blue Gene/P and Pluto code: Flock et al. (2011)
Ionization structure of a T Tauri disk(Semenov, Wiebe, Henning, 2004, A&A, 417, 93)
„Layered“ vertical structure
Mixed grains(dead zone)
Sedimentation
See alsoIlgner & Nelson(2006, 2007)
Disk mass and planet mass
Log(Mdisk/MMSN)
Plan
et m
ass
[Jov
ian
mas
ses]
Maximal planetmass increases with disk mass.
Mplanet=0.5 Mdisk
Mordasini et al. , submitted.
PAHs in Protoplanetary Disks
(Acke, Bouwman, Juhasz, Henning et al. 2010)
(Geers et al. 2007, RR Tau)
Dust and GasDisk Lifetimes
Haisch et al. (2001), Hernandez et al. (2008), … Fedele et al. (2010), …
FEPS Spitzer
Legacy IRS
survey20 stars
with ages 3-
100 Myr
=> No gas
rich disks
(> 0.1 MJup)
detected. Hollenbach et al. (2005),Pascucci et al. (2006)
See also: Ingleby et al. (2009)
Gas Disk Lifetimes < 10 Myr
Different stages of disk evolution~
10
Myr
~1
Myr
V(km/s) log(/ m)
H
H
H
V(km/s) log(/ m)
V(km/s) log(/ m)
Typical CTTS
Flattened, accreting disk
Non-accreting TO
A molecular disk at its edge
• CO emission at 4.7 μm• Gas in Keplerian orbit• Inner cavity (r~11 AU)• Coming closer to the star than HST
• 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)
HD 141569A
LkCa 15 – The SEEDS CollaborationLkCa 15 – The SEEDS Collaboration
What physical object is it that we see as a What physical object is it that we see as a bright crescent? Two possibilities:bright crescent? Two possibilities:
Offset between nebulosity center and star suggests eccentric outer disk; this is Offset between nebulosity center and star suggests eccentric outer disk; this is expected from dynamical influence of planets, and hard to explain otherwise.expected from dynamical influence of planets, and hard to explain otherwise.
Illuminated wall of Illuminated wall of the disk on the far the disk on the far side.side.
Forward-scattering Forward-scattering on near-side disk on near-side disk surface.surface.
Thalmann et al. 2010Thalmann et al. 2010
Espaillat et al. 2008Espaillat et al. 2008 Thalmann et al. 2010Thalmann et al. 2010
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)
Dust and gas strongly coupled …
Disk Structure
~500 AU100 AU0.03 AU
~1000 AU
0
Observable region with interferometers
photon-dominated layer hν, UV, X-rays
turbulent mixing
IS UV, cosmic rays
Snowline (T=100K)
puffed-upinner rim
accretionwarm mol. layer
cold midplane
How to produce simple hydrocarbons?
Gas-phase chemistry allows to build up simple moleculesthat can later freeze out or are ‘used’ to form larger species
radiative association
reactions with C
Spectroscopy - An Essential Tool
ISO SWS disk spectrum of the Herbig Ae star HD 100546 (Malfait et al. 1998) and comet Hale-Bopp (Crovisier et al. 1997) for comparison
(Background)
Apai et al. (2005); Flux at mJy level Pontoppidan et al. (2005)
DRM Documents, MISC Report,August 22nd, 2001
H2 is a challenging molecule to detect
Rotational lines between5.05 µm and 28.22 µm
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.
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)
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)
Spectroscopy at sub-mm wavelengths
Dutrey et al. 1997
Thi et al. 2004;Kastner et al. 1997
CID @ PDBI:Dutrey ea. 07, Schreyer ea.08,Henning ea. 10, ….DISCS @SMA: Öberg ea. 10, 11
Molecular Abundances in Disks
10-9
10-8
10-7
10-6
10-5
10-4
Log
10 (
Abu
ndan
ce R
el. t
o H
2)
CO HCN HNC CN CS H2CO HCO+ C2H
DM Tau Disk Mol. Cloud
Strong depletion of gas-phase species: radiation or freeze-out?
IR Spectroscopy Reveals Complex Chemistry
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
(Lahuis et al. 2006 IRS 46 in Ophiuchus; Variable) see also Gibb et al. 2008 for GV Tau)
700 K 400 K 300 K
Organic Molecules and Water
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)
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)
VLT/VISIR: Pontoppidan ea. (10)
Abundance of water is getting higher in mid-Abundance of water is getting higher in mid-plane and in intermediate warm disk layer. plane and in intermediate warm disk layer. Maximum of abundance shifts deeper into Maximum of abundance shifts deeper into the disk which may prevent water vapor the disk which may prevent water vapor
from being observed.from being observed.
Vasyunin, Henning et al. (2011)
Dust Evolution and Water Abundance
HD 100456 with Herschel
Sturm, Bouwman, Henning et al. (2010; see also Thi et al. 2011)
CO, [OI], [CII], CO, H2O, CH+, …
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
Disk structure
Spectroscopy Imaging
Dust settling revealed by imaging
PAH
Image in PAH and dust continuum bands
Imaging gaps in transitional disks
VLT VISIR image8.6 PAH 11.3 PAH19.8 m large grains
Geers et al. 2007Ratzka et al. 2007Brown et al. 2008. 2009Pontoppidan et al. 2008Eisner et al. 2009Thalmann et al. 2010
IRS48
SR 21
Examples of disks known to have big enough gaps (~40 AU) to resolve with MIRI imaging and IFU
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
Uniqueness of MIRI/MRS
High spectral resolution, high sensitivity, continuous coverage:
• line-to-continuum ratio sufficient to detect minor species (res: 2000-3700) • extend studies to faint brown dwarf disks (mJy @ 10m)
[Fred Lahuis][Fred Lahuis]
Inventory of Organic Molecules in Disksof 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
Hydrogen rotational lines
Hydrogen deuteride rotational lines
Hydroxyl radical rotational lines entire range
Water rotational lines entire range
Carbon dioxide
Acetylene
HCN Hydrogen cyanide
HNC Hydrogen isocyanide
Sulfur dioxide
Carbon disulphide
Methane
Methyl radical
Ammonia
HNCO Isocyanic acid
Ethane
Benzene
Formyl ion
Methanol
H2 λ = 5.05 – 28.22 μmHD λ = 11.5 – 28.50 μmOH
H2O
ν2 ro-vibr. band λC = 6.27 μm
CO2 ν2 ro-vibr. band λC = 15.0 μm
C2H2 ν5 ro-vibr. band λC = 13.7 μm
ν2 ro-vibr. band λC = 14.0 μm
ν2 ro-vibr. band λC = 21.6 μm
SO2 ν3 ro-vibr. band λC = 7.34 μm
CS2 ν2 ro-vibr. band λC = 25.2 μm
CH4 ν4 ro-vibr. band λC = 7.66 μm
CH3 ν2 ro-vibr. band λC = 16.5 μm
NH3 ν2 ro-vibr. band λC = 10.5 μm
ν4 ro-vibr. band λC = 12.9 μm
C2H6 ν9 ro-vibr. band λC = 12.2 μm
C6H6 ν4 ro-vibr. band λC = 14.8 μm
HCO+ ν2 ro-vibr. band λC = 12.1 μm
CH3OH ν8 ro-vibr. band λC = 9.68 μm
HNC, CH4, CH3,C2H6, CH3OH, …to be detectedwith MIRI
The Water Reservoir
MIRI water lines come from an inner dense region
Woitke et al. (2009)
The Power of the MIRI IFU
F. Lahuis
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
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
MIRI Science Disk TeamImaging and Spectroscopy of PP Disks