10 - the Protoplanetary Disk Phase

10 - The protoplanetary disk phase

Molecular deuteration, water abundance, dust coagulation and mixing processes.

C.Ceccarelli : Water in circumstellar disks and interstellar medium 1 Astrobiology Winter School , Hawaii 2005 10- Protoplanetary disks

THE COLLAPSING PROTOSTAR PHASE

C.Ceccarelli : Water in circumstellar disks and interstellar medium 2 Astrobiology Winter School , Hawaii 2005 10-Protoplanetary disks THE CHEMICAL COMPOSITION AND MOLECULAR COMPLEXITY DURING THE LOW STAR FORMATION

C.Ceccarelli : Water in circumstellar disks and interstellar medium 3 Astrobiology Winter School , Hawaii 2005 10- Protoplanetary disks THE PROTOPLANETARY DISKS : the pictures

C.Ceccarelli : Water in circumstellar disks and interstellar medium 4 Astrobiology Winter School , Hawaii 2005 10- Protoplanetary disks THE PROTOPLANETARY DISKS : the numbers

DISK MASS ~ 0.01 MO

STAR LUMINOSITY ~ 1 LO DISK RADIUS ~ 200-800 AU

DISK ANGULAR DIAMETERS (@140pc) ~3”-12”

C.Ceccarelli : Water in circumstellar disks and interstellar medium 5 Astrobiology Winter School , Hawaii 2005 10- Protoplanetary disks THE PROTOPLANETARY DISK STRUCTURE Atmosphere T>100K,n<10cm-3 partially ionized gas: H, O, C+…. H O UV photons 2 Deuterated Warm layer molecules T~25-100K, n~103-106 cm-3 molecular gas:

H2, CO, H2CO ….

Midplane T<25 K, n>106cm-3 CO depleted gas: + + H2, HD, H2D , HD2 C.Ceccarelli : Water in circumstellar disks and interstellar medium 6 Astrobiology Winter School , Hawaii 2005 10- Protoplanetary disks WATER IN PROTOPLANETARY DISKS NO DETECTIONS SO FAR ! But we do not have enough sensitive instruments yet. ISO : 1.5 arcmin (filling factor= 103 -60), first transition at 110K SWAS : 4.5 arcmin (filling factor=104-600), first transition at 60 K ODIN : 1.8 arcmin (filling factor=103-102), first transition at 60 K

…WAITING FOR THE NEXT SATELLITE : HSO…. (likely the next next satellite !…..0

C.Ceccarelli : Water in circumstellar disks and interstellar medium 7 Astrobiology Winter School , Hawaii 2005 10- Protostellar disks MOLECULAR DEUTERATION NOT MUCH SO FAR !

Detection of only two deuterated species (each time in one disk source only):

1- DCO+ (van Dishoeck et al. 2003)

+ 2- H2D (Ceccarelli et al. 2004)

But we did not have enough sensitive instruments until recently. New observations are in progress…

C.Ceccarelli : Water in circumstellar disks and interstellar medium 8 Astrobiology Winter School , Hawaii 2005 10- Protostellar disks MOLECULAR DEUTERATION : DCO+ DCO+ (van Dishoeck et al. 2003) Detected DCO+ in TW Hya Region DCO+/HCO+ DCO+/HCO+=0.035 Molecular clouds 0.02-0.07 -> A clear measure of the Pre-stellar cores 0.04-0.2 importance of low- Class 0 sources 0.01-0.05 temperature gas-phase deuteration in disks. TW Hya Disk 0.035 HB Comet (DCN) 0.002-0.09

C.Ceccarelli : Water in circumstellar disks and interstellar medium 9 Astrobiology Winter School , Hawaii 2005 10- Protostellar disks + MOLECULAR DEUTERATION : H2D

T=10 K MIDPLANE

WARM LAYER (Ceccarelli, Dominik, Lefloch et al. 2004)

C.Ceccarelli : Water in circumstellar disks and interstellar medium 10 Astrobiology Winter School , Hawaii 2005 10- Protostellar disks

+ MOLECULAR DEUTERATION : H2D

104

103

(Ceccarelli et al. 2004) (Ceccarelli & Dominik 2005) C.Ceccarelli : Water in circumstellar disks and interstellar medium 11 Astrobiology Winter School , Hawaii 2005 10- Protostellar disks + H2D : WHY IS IT IMPORTANT ? Circumstellar disks around young stars are expected to be the sites of planet formation. When, and exactly how planets form depends on the evolution of the disks: the accretion properties, the dispersal of gas from the disk, and when and how dust coagulation proceeds. Unfortunately, direct observations of the bulk of the disk (=midplane) gas are difﬁcult to achieve.The main element, hydrogen, is present in H2 molecules, but the rotational lines of H2 only probe the warm (~100K) gas in the disk. The second most abundant molecule, CO, probes colder gas, but, unfortunately, not the disk midplane gas, where it is frozen out onto the grain mantles. The only available probes are the ground + + transitions of HD, H2D and HD2 . DERIVED PARAMETERS: GAS-TO-DUST RATIO (gas dispersion/dust coagulation) & IONIZATION DEGREE (viscous accretion) IN THE MIDPLANE, THE MASS RESERVOIR.

C.Ceccarelli : Water in circumstellar disks and interstellar medium 12 Astrobiology Winter School , Hawaii 2005 10- Protostellar disks + - THE H2D AND e ABUNDANCE

RESULTS:

1) The estimate of the ionization degree in the disk midplane implies that magnetorotional instability (the mechanism claimed for the accretion viscosity from the disk to the star) across the disk canC.C eoperateccarelli : Water .in circumstellar disks and interstellar medium 13 Astrobiology Winter School , Hawaii 2005 10- Protostellar disks + - THE H2D AND e ABUNDANCE

RESULTS: DM Tau 2) If the cosmic rays ionization degree is the standard one, the dust- to-gas ratio is ten times smaller in DM Tau than that in the ISM. In other words, there is ten times more gas than in « normal » ISM, which suggests that the dust started to coagulated in the midplane. Are we seeing the first step towards planet formation ?

C.Ceccarelli : Water in circumstellar disks and interstellar medium 14 Astrobiology Winter School , Hawaii 2005 10- Protostellar disks DEUTERATED WATER IN PROTOSTELLAR DISKS NO DETECTIONS SO FAR ! But we did not have enough sensitive instruments until recently. New observations are in progress… Water is expected to be depleted in the outer midplane and across most of the outer disk, because of the relatively

large binding energy (Tev~100K).

Using the HDO/H2O ratio measured in low mass protostars (Lectur #4), one would have a Cut across the disk at 100AU (from Ceccarelli & Dominik 2005) low -but observable with JCMT and CSO- HDO column density. C.Ceccarelli : Water in circumstellar disks and interstellar medium 15 Astrobiology Winter School , Hawaii 2005 10- Protostellar disks MIXING PROCESSES IN PROTOSTELLAR DISKS Other than useful for the link with the comets, the HDO abundance can be used to understand if mixing is occurring in the disk - i.e. if the matter circulates from the inner to the outer disk, and/or from the midplane to the surface.

C.Ceccarelli : Water in circumstellar disks and interstellar medium 16 Astrobiology Winter School , Hawaii 2005 CALCITE in protostars and protoplanetary disks

92µm DUST FEATURE: CALCITE

Ceccarelli et al. 2002; Chiavassa et al. 2005 (Kemper et al. 2002, Nature)

CALCITE detected in about 20 protostars and protoplanetary disks (out of 40

C.Ceccarelli : Water in circumstellar disks and interstellar medium 17 Astrobiology Winter School , Hawaii 2005 CALCITE FORMATION: « DETECTIONS » OF CALCITE IN THE UNIVERSE:

1. EARTH: 1% OF SILICATES

2. METEORITES: 1% OF SILICATES

3. ONE PLANETARY NEBULA: 0.3% OF SILICATES

4. PROTOSTARS & PROTOPLANETARAY DISKS: 1%

FORMATION OF CALCITE:

1. EARTH: ACQUEOUS ALTERATION OF SILICATES

2. METEORITES: ACQUEOUS ALTERATION IN THE PARENTAL BODY (E.G. MARTIAN METEORITES)

3. PLANETARY NEBULA: CaO2 + CO2 CONDENSATION FROM GAS PHASE (AT 1200K)

4. PROTOSTARS & DISKS : ? C.Ceccarelli : Water in circumstellar disks and interstellar medium 18 Astrobiology Winter School , Hawaii 2005 CALCITE FORMATION: CALCITE MAY FORM ON THE GRAIN SURFACES, WHERE THE LAYERS OF THE ICE MANTLES DIRECTLY ADJACENT TO THE GRAIN SURFACE COULD ACT AS LIQUID WATER.

2+ WATER ICES ENRICHED IN CO2 WOULD REACT WITH THE Ca CONTAINED IN THE SILICATE LATTICE TO FORM CALCITE. X-RAYS MAY PROVIDE A LOCAL HEATING AT THE SURFACE OF THE GRAIN MAKING THE LAYERS MOBILE. ONCE A X-RAY HITS A GRAIN IT CAN HEATS UP IT LOCALLY. E.G. Najita et al. (2002) ESTIMATED THAT SUB- UNITS OF 50A WOULD BE SPOT HEATED TO >150K WITH DEPOSIT OF 300ev OF ENERGY. AND AT >190K THE ICE MOBILITY STARTS TO BE NON NULL (Rietmeijer 1985).

CALCITE: SIGNSPOT OF THE INTERACTION OF X-RAYS WITH THE SURROUNDING DUST?…

C.Ceccarelli : Water in circumstellar disks and interstellar medium 19 Astrobiology Winter School , Hawaii 2005 CALCITE : SPECULATION YOUNG PROTOSTARS ARE POWERFUL X-RAYS SOURCES: THE INTERACTION OF THE X-RAYS WITH THEIR SURROUNDINGS IS STILL TO BE FULLY EXPLORED, BUT THERE MAY BE ALREADY OBSERVATIONAL EVIDENCES OF IT.

IF THE CALCITE FORMATION THEORY IS SUBSTANTIALLY CORRECT THE SAME MECHANISM MAY FORM COMPLEX, PRE- BIOTIC MOLECULES TRAPPED IN THE GRAINS ???

C.Ceccarelli : Water in circumstellar disks and interstellar medium 20 Astrobiology Winter School , Hawaii 2005 8- Hot Corinos

Summary

• We very badly need more sensitive instruments to observe the molecules, and particularly water, in protoplanetary disks.

• So far no water obs are available, and only two deuterated + + molecules have been observed : DCO and H2D . More sensitive observations are however in the horizon (ALMA), and they will help to understand how protoplanetary disks evolve and form planets.

C.Ceccarelli : Water in circumstellar disks and interstellar medium 21 Astrobiology Winter School , Hawaii 2005 10- Protostellar disks Concluding remarks

MANY THANKS TO THE ORGANIZERS,

BO & KAREN,

FOR INVITING ME, AND TO ALL OF YOU FOR HAVING MADE IT SUCH A STIMULATING SCHOOL !

IT HAS BEEN A GREAT FUN !

Have a nice week in Hilo !

C.Ceccarelli : Water in circumstellar disks and interstellar medium 22 Astrobiology Winter School , Hawaii 2005