resonance line scattering in the pic disk: disks in star and planet formation, cumberland lodge,...

Resonance Line Scattering in thePic Disk: Disks in Star and Planet Formation, Cumberland Lodge, July 16-19, 2001 1

Resonance Line Scattering in the Pic Disk

Göran Olofsson + René Liseau + Alexis BrandekerStockholm Observatory, Sweden


Resonance Line Scattering in the Pic Disk

Göran Olofsson + René Liseau + Alexis BrandekerStockholm Observatory, Sweden

Discovery of extended and velocity tracing atomic gas

…what disk ?


Pic: Main-Sequence Vega Excess Star

IRAS 05460-5104Neugebauer et al. 1984, ApJ 278, L1Backman & Paresce 1993, PPIII, 1253

Disk (in scattered visual light):Smith & Terrile 1984, Sci. 226, 1421

A Highlight of


Thermal radiation bycool Pic dust disk:Tave 100 K (inner 450 AU)

JCMT-SCUBA 850 mHolland et al. 1998, Nat 392, 788


Accompanying Molecular Emission ?

...mm/submm search for rotational lines

- advantage:heterodyne technique permits very high spectral resolution R >> 3105 (v << 1 km s-1) disk kinematics from line profiles

(see: Anne Dutrey’s talk @ this conference)

- disadvantage:single dish telescopes provide only low spatial resolutionx Pic U) little detail in maps/images (southern hemisphere)


There is CO in the Pic disk...

UV Absorption - Detection: Vidal-Madjar et al. 1994, AA 290, 245Jolly et al. 1998, AA 329, 1028Roberge et al. 2000, ApJ 538, 904

(CO) = 61014 cm-2, ex = 20 - 50 K

CO ul and gas-to-dust mass ratio

mm Emission - Upper Limit: Savoldini & Galletta 1994, AA 285, 467Dent et al. 1995, MNRAS 277, L25Liseau & Artymowicz 1998, AA 334, 935

…but in a confined region along the line of sight toward the star


Grains must be replenished…and so must any Gas


Is there Any Widespread Molecular Gas in the Pic Disk?

H2 in Emission: Thi et al. 2001, Nat 409, 60ISO-SWS: pure rotational lines, Eu/k > 500 K, A < 1010 s-1

M(H2) = 0.17 MJup

H2 in Absorption: Lecavelier des Etangs et al. 2001, preprintFUSE: electronic transitions, El/k 0 K, A > 108 s-1 M(H2) 3104 MJup (CO/H2 > 6 104)


Is there Any Widespread Atomic Gas in the Disk?Spectrum of bright star and faint disk


North

East

Slit length = 300Slit width = 1Position angle = 30.75deg

Kalas & Jewett 1995, AJ 110, 794


North

East

Check with slitperpendicular*

and with Pic


An Ancient Experiment

James E. Keeler 1895

A spectroscopic proof of the meteoric constitution of Saturn’s rings

ApJ 1, 416-427


Sodium D1/2 lines toward Pictoris

ESO La Silla, Chile

3.5m NTT

EMMI + long slit (R 60000)

nb filter - cross disperser, optimised blaze


Pic: Model parametersM =1.8 Mo

R = 1.9 Ro

Teff/log g/ Z/Zo = 8000 K/4.5/0.0(NEXTGEN model atmospheres, Hauschildt et al. 1999, ApJ 512, 337)

tstar = 10 - 100 Myr (Crifo et al. 1997, AA 320, L29Barrado y Navascués et al. 1999,

ApJ 520, L123)

Mdust 0.5 M

(Chini et al. 1991, AA 252, 220)

idisk = 88.7 deg


NaD lines: Velocity tracers of the Pic disk

= 10- 4 Mstar r -1/2 cos i sin ± non-grav (Å)

Optically thin line ratio, 2:1


Pic - NaI D2 (5892 Å)Normalised line profiles

0.27 pxl-1 (5 AU pxl-1)0.035 Å pxl-1 (2 km s-1)

Observations: histogramModel: smooth solid line


Atomic Gas Mass

Disk Absorption Line:@systemic/stellar velocity

EW(NaD2) = 9.4 mÅ*

M(Na) 21017 g[M(dust) 21027 g]

*cf. Vidal-Madjar et al. 1986, AA 167, 325

Disk Emission Line:

EW(NaD2) = 0.72 mÅ

(disk) = 8.8 deg[r0(NaD) = 30 AU, H0(disk) = 4.6 AU]*

*cf. Z(x) = 0.055 rmax x0.75 , x = r/ rmax

rmax = 120 AU

N(Na) = 61010 cm-2

if Na/H solar (210-6), then

N(HI) = 31016 cm-2 * *cf. Freudling et al. 1995, AA 301, 231: N(HI) 1019 cm-2


Detected/non-detected Gas in the Pic Diskin absorption against stellar continuum: Molecular gas: CO Atomic gas: Na I Molecular gas: H2

in emission from extended regions of the disk: Atomic gas: Na I Atomic gas: H I Molecular gas: CO, CS, SiO Molecular gas: H2

Needs confirmation


Pic Disk: Radial Intensity Profiles

Resonantly Scattered Lines and Dust Scattered Lightreveal similar spatial distributions

indicates coexistence? indicates common origin?

Dust profiles from Heap et al. 2000, ApJ 539, 435

…but scattering phase functions…


North

East

Sense of Disk Rotation

Toward us

Away from us


Conclusions

• Line emission from neutral sodium is detected far out in the Pic

disk, to at least 140 AU.

• This emission originates mainly from resonantly scattered stellar

photons by Na atoms throughout the disk, with central absorption.

•Mass estimates of the neutral atomic gas indicate that the gas-to-dust

mass ratio is probably very much smaller than typical ISM values.

•The observed velocities are well fit by Keplerian rotation.

• This rotation is clockwise (SW: toward us, NE: away from us).

• Potentially, these lines are optimal tracers of the velocity fields in

debris disks and open up the possibility of observational dynamical

studies.


The End ?


Future Plans Pic: Na I at higher spatial and spectral resolution spectral. mapping at different PAs spectral line survey (Mg II, Ca II, K I , O I…) Other Vega xs stars: as above (in both hemispheres)

IF resonance lines common feature, then dynamical investigations - including planetary disturbences


The Final End !

…FOR NOW

resonance line scattering in the pic disk: disks in star and planet formation, cumberland lodge,...

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