Molecular Surveys of the Disks Encircling T Tauri/Herbig Ae Stars

Geoffrey A. BlakeCalTech

Chemistry as a Diagnostic of Star Formation Waterloo, Canada 23Aug2002

People Really Doing the Work!

Caltech: -Jacqueline Kessler, Chunhua Qi (now at the SMA/CfA) -Adwin Boogert

Leiden w/Ewine van Dishoeck: -Klaus Pontoppidan, Gerd Jan van Zadelhoff, Wing-Fai Thi (now at UCL)

Arizona: -Michiel Hogerheijde

SFCHEM 2002

23Aug02

Study Isolated Disks (Weak/No Outflow)

SFCHEM 2002 23Aug02

Beckwith & Sargent 1996

Spectroscopy of “Disk Atmospheres”

SFCHEM 2002 23Aug02

IR disk surface within several tens of AU(sub)mm disk surface at large radii, disk interior

G.J. vanZadelhoff2002

MM-Wave CO Traces Dynamics, Others?

SFCHEM 2002 23Aug02

Dutrey et al. 1997, IRAM 30m

Kastner et al. 1997, TW Hya, JCMT

M. Simon et al. 2001, PdBI

Measure:R_diskM_starInclination

w/resolvedimages.

The Sample (drawn from larger single dish survey)

Star Sp Type d(pc) Teff(K) R(Rsun) L(Lsun) M(Msun) Age(Myr) LkCa 15 K5:V 140 4365 1.64 0.72 0.81 11.7 GM Aur K5V:e 140 4060 1.78 0.8 0.84 1.8HD 163296 A0 120 9550 2.2 30.2 2.3 6.0 MWC 480 A3 130 8710 2.1 32.4 2.0 4.6

Mannings, Koerner & Sargent 1997Mannings, Koerner & Sargent 1997

MWC 480

LkCa 15

Koerner & Sargent 1995

OVRO+CSO/JCMT MM-Wave Disk Survey

SFCHEM 2002 23Aug02See also poster #67 (SMA maps)

Combine 3/1.3 mm array images w/higher J spectra to

constrain OUTER disk properties, chemical networks.

van Zadelhoff et al. 2001

OVRO+CSO/JCMT MM-Wave Disk Survey II

SFCHEM 2002 23Aug02

Disk properties vary widelywith radius, height; and depend on accretion rate,etc. (Aikawa et al. 2002, w/D’Alessio et al. disk models, poster #21).

Currently sensitive only to R>100 AU in gas tracers, R<100 AU dust.

CO clearly optically thick, other species likely to be as well.

Model via 2D Monte Carlo using disk structure and chemical models as input, vary to fit observations (Kessler talk).

Disk Ionization Structure: CO and Ions

Source L* (L ) CN/HCN H

dust/h

gas

LkCa 15 0.72 ~ 10 1.0GM Aur 0.80 << 1 4.0 MWC 480 30.2 ~ 4 1.7 HD 163293 35.2 >> 50 -

[CN]/[HCN] traces enhanced UV fields (Fuente et al. 1993,

Chiang et al. 2001)

Molecular distribution ring-like?

Photochemistry or desorption?

Qi et al., in prep

UV Fields: HCN and CN

LkCa 15

SFCHEM 2002 23Aug02

NT(CS) = 1013-1014 cm-2

Upper limits only for H2S,SO,SO2 CS dominant Reminiscent of “early time”

chemistry.

LkCa 15 CS 2-1 LkCa 15 C34S 5-4

Sulfur Species

SFCHEM 2002 23Aug02

CH3OH, H2CO - grain surface production SiO - grain sputtering + gas phase rxn

CH3OHH2CO

Si

Si + O2 SiO + O hh

H2CO

CH3OH

Grain chemistry: CH3OH, SiO, H2CO

SFCHEM 2002 23Aug02

Are Even Larger Molecules Present?

•Observations can test gas/grain models, HIFI and arrays can uniquely access small, dense cores & disks.

•Laboratory spectra urgently needed, work underway (posters #11,84).

SFCHEM 200223Aug02

Grain Chemistry Model(Charnley 2001)

Glycine

MM-continuum surveys do not reveal such large, massive disks in similarly aged clusters (IC348) and clouds (NGC 2024, MBM12). Environment?

Need better (sub)mm-wave imaging capabilities.

CO, HCO+ (and NNH+) chemistry well predicted by disk models.

Other species, esp. CS, CN, HCN, much more intense, with unusual emission patterns in some cases (LkCa 15).

Are these large disks unusual?

SFCHEM 2002 23Aug02

Future of the U.S. University Arrays – CARMA

Juniper Flat

CARMA = BIMA (9 6.1m) + OVRO (6 10.4m) + SZ Array (8 3.5m) telescopes.

SUP submitted2003 SZA on site2004 move OVRO2004 move BIMA2005 full operations

(pre-ALMA) The size scales are too small even for the largest current near-IR arrays… Spectroscopy to the rescue!

Simulation G. Bryden

How can we probe the planet-forming region?

Theory

Observation?

Jupiter (5 AU):V_doppler = 13 m/sV_orbit = 20 km/s

High Resolution IR Spectroscopy & Disks

CO M-band fundamental

VLT

Keck

NIRSPECR=25000

R=10,000-100,000 (30-3 km/s) echelle spectrographs (ISAAC,MICHELLE, NIRSPEC, PHOENIX,TEXES)on 8-10m telescopes can now probe“typical” T Tauri/Herbig Ae stars:

L1489:Gas/Ice~10/1, accretion.

CRBR2422.8:Gas/Ice~1/1, velocity field?

Elias 18Gas/Ice<1/10(Shuping et al.)

Edge-on absorption.

Orientation is Pivotal in the IR!

H3+ in absorption?SFCHEM 2002

23Aug02

Poster #79

Edge-on Disks & Comets?

IR studies of edge on disks could map out both gas phase & grain mantle composition, compare to that found in massive YSOs, comets.

N7538 W33A Hale-BoppWater 100 100 100CO 10 1 23CO2 16 3 6CH4 1 0.7 0.6H2CO 3 2 1CH3OH 9 10 2HCOOH 2 0.5 0.1 NH3 10 4 0.7OCS 0.1 0.05 0.4

SFCHEM 2002 23Aug02

GSS30 – Class I T Tauri star, accretion shock emission?

Broad H I from accretion/outflow,narrow CO from disk. Gap tracer(Carr et al. 2001, DQ Tau)?

More typically, emission is seen in M-band

Pontoppidan et al. 2002 (ISAAC, R~5000, poster #66)

(NIRSPEC, R~25000)

SFCHEM 2002 23Aug02

CO and 13CO rotation diagrams show two components, but even the “hot” component is <500 K.

Very small amounts of gas.

Collisional excitation unimportant at these temperatures, Resonant scattering!

Need detailed radiative transfer models (similar effects seen in massive YSOs, Mitchell et al., van der Tak et al.).

How is the CO excited in these disks?

SFCHEM 2002 23Aug02

Explanation:

Dust sublimation near the star exposes the inner disk to direct stellar radiation, heating the dust and “puffing up” the disk.

Flared disk models often possess 2-5 micron deficiency in model SEDs, where a “bump” is often observed for Herbig Ae stars.

Where does the CO emission come from?

Dullemond et al. 2002

SFCHEM 2002 23Aug02

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.

Fits to AB Aur SED yield an inner radius of ~0.5 AU (and 0.06 AU for T Tau).

SED Fits versus IR Interferometry

(Monnier & Millan-Gabet 2002, astro-ph/0207292)

Dullemond et al. 2002

Many other species and disk types (transitional, debris, etc.) should be examined in both absorption (edge on disks) and emission: H3

+, CH4, H2O, OCS...

Future “Near”-IR (1-5 um) Spectroscopy

SFCHEM 2002 23Aug02

Brittain & Rettig 2002, poster #10

Rotational H2 lines potentially provide direct measure of gas mass w/o need for abundance calibrations.

Additional studies/confirmation in optically thick, “transitional” pivotal. Difficult, but doable, from the ground.

Mid-IR Spectroscopy – Unique access to “warm” H2

Thi et al. 2001

SFCHEM 2002 23Aug02

SIRTF

- IRAC (mid-IR cameras, 3.6

4.5, 5.8, 8.0 m)

- MIPS (far-IR cameras, 24, 70

160 m, R=20 SED mode)

- IRS (5-40 m long slit,R=150,

10-38 m echelle, R=600)

09 Jan 2003 launch

- GTO observations

- Legacy program

- General observations

SFCHEM 2002 23Aug02

ISO SWS data on A stars,

SIRTF can do sun-like stars, high spectral resolution needed for gas phase features.

Evans et al., c2d~170 sources first look + follow up of mapping (poster #46).

Meyer et al.Photometry~350 sources, IRS follow up (Class III).

SIRTF – Spectroscopy of Dust and IceSIRTF – Spectroscopy of Dust and Ice

SFCHEM 2002 23Aug02

(Sub)mm-wave instruments can only study the outer reaches of large disks at present.

Expanded arrays (CARMA, eSMA, ALMA) will provide access to much smaller scales.

HIFI will enable first assault on water in the cold regions of disks, and may provide a new window on molecular complexity.

High resolution IR spectroscopy just starting, is immensely powerful, and will provide unique access to the 1-10 AU region until the advent of ALMA, large IR interferometers.

SIRTF will provide many new targets!

Disk Spectroscopy - ConclusionsDisk Spectroscopy - Conclusions

SFCHEM 2002 23Aug02