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Francesco Trotta YERAC, Manchester - 2011 Using mm observations to constrain variations of dust properties in circumstellar disks Advised by: Leonardo.

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Presentation on theme: "Francesco Trotta YERAC, Manchester - 2011 Using mm observations to constrain variations of dust properties in circumstellar disks Advised by: Leonardo."— Presentation transcript:

1 Francesco Trotta YERAC, Manchester Using mm observations to constrain variations of dust properties in circumstellar disks Advised by: Leonardo Testi

2 Planet Formation in circumstellar disks Observational evidence of dust grain growth Constrain the radial variation of dust properties with high-resolution mm-observation Future prospective with ALMA Outline

3 What are the circumstellar disks and why do we study them? Disks are presumed to be the birthplace of planetary system Forming star Rotating disk Mass accretion Central forming star accretes most of its mass throught the disk dominates the mass the dynamics of the disk dominates the opacity thermal and gemetrical structure of the disk the emission properties of the disk GAS 99% DUST 1% Angular Momentum transported outward Circumstellar disks play a fundamental role in the process of star and planet formation Turbulence Transport angular momentum Mass accretion onto the star with time: (1) M star M disk (2) Disk spreads out

4 1 m1m1m1km10 3 km Log a 1mm ISM dust grains coupled to the gasgravity coupled to the gas + gravity Early growthMid-life growthLate growth Gas sweepingGravitational interactionAereodynamic interaction Core accretion model weakwell Growth of 12 order of magn. in size in a few Myr From dust to planet

5 1 m1m1m1km10 3 km Log a 1mm ISM dust grains coupled to the gasgravity coupled to the gas + gravity Early growthMid-life growthLate growth Gas sweepingGravitational interactionAereodynamic interaction weakwell From dust to planet Directly observable Exo-Planets Growth of 12 order of magn. in size in a few Myr Core accretion model

6 Which observations do we need? The dust thermal emission (at each radius) with Optical depth Optical depth is very high (at least at short ) LIMITATION:

7 Which observations do we need? The dust thermal emission (at each radius) with Optical depth Optical depth is very high (at least at short ) LIMITATION: Probe the bulk of the dust mass in the disk mid-plane Information only on grain located in the surface layer (tiny fraction of dust mass) Limited to the outer regions of the disks V IR R Longer bigger fraction of the dust optically thin

8 How to observe dust grain size at mm- ? Small (compact) grain (a<< ) (es. ISM dust ~ 1.7) For a optically thin disk and in RJ regime the dust thermal emission at mm- =2 Solid bodies with a>> (es. Rocks) =0 mm-size particles Optically thick inner region Deviation from RJ regime + > - 2 (diagnostic of dust size,shape,composition) We are observing F ~ Draine & Lee (1984) Gray opacity Log F Log

9 Grain growth evidence from mm spectral index If < ISM ~ 1.7 DUST GRAIN GROWTH Resolved (large) disks make (2) improbable Need of Spatially Resolved Disk at mm (hi-res interferometry) Two possibility Testi & al. (2003) CQ Tau VLA 7mm res~0.8 (~100 AU) Observational evidence Shallow SED ( mesured are small ) (1) Optically thin disk & low (2) Optically thick disk & any

10 Disk models (with radial variation of the grain size distrib) High-resolution observ (at more ) How to constrain the radial variation of dust properties? Dust evolution models predict grain growth different dust properties in function the position on the disk dust (x) We are trying tho constrain the radial opacity profile

11 Surface layer Interior Surface Density Similarity Solution Grain size distribution PowerLaw approximation star surface interior total SURFACE LAYER Dominate the flux ~ 60 m (mid-IR) STAR BB emission picco a - 1 m (near-IR) INTERIOR LAYER Dominate the flux a > 100 m (sub-mm/mm) Disk models How to constrain the radial variation of dust properties?

12 Isella & al. (2010) 1.3mm 2.8mm 6.92mm res~0.5 (~70 AU) res~0.3 (~40 AU) res~0.15 (~20 AU) CARMA VLA High angular resolution observations at 3 different mm- of RY Tau new data High-res observation CARMA VLA How to constrain the radial variation of dust properties? Disk around RYTau

13 We use 2 fitting procedure (directly on visibility) Choose the grid models (n free-param with a wide range of value) Produce disk images Fourier trasform it and sampled at the (u,v) points corrisponding to the observed samples Computed the 2 value Calculate the best fitting model (minimum of the 2 hypercube_sum) Costruct the 2 hypercube (for each ) Free parameter tr R tr a 0max b max incP.A. How to constrain the disk parameters?

14 First results R tr = 30 [AU] tr = 3.4 [g/cm^2] = R tr = 34 [AU] tr = 2.3 [g/cm^2] = R tr = 36 [AU] tr = 1.8 [g/cm^2] = -0.9 The best fit values we found are ~ in agreement with the Isella result a 0max =0.03cm b max = 0 P.A. = 24° Inclination = 66° Compare with Isella & al mm 2.8mm 6.92mm But large error-bars Evidence of radial variation of dust properties BEST FIT VALUE

15 Future prospects ALMA To place more stringent constrains on the radial variation of the dust opacity we need of observations with: higher angular resolution higher sensitivity At least 50 X 12m Antennas max resolution <0.01 at 870 m Will be able to resolve structure of few AU (at near star forming region) Should be possible detect spiral structure of few AU

16 Simulated observations of massive self-graviting circumstellar disk with ALMA Should be possible detect spiral structure of few AU Cossin,Lodato,Testi (2010) Intensity maps at sub- mm from SPH simulation of disk Image maps at that sub-mm with various array conf. CASA ALMA simulator (Taurus-Auriga star-forming region)

17 Conclusions mm spectral slopes indicate presence of mm-size dust grains in the disk (dust grain growth) To study the radial variation of the dust properties we need of observations with higher angular resolution and sensitivity High angular resolution observation show us radial variation of dust property in circumstellar disk ALMA will play a crucial role in the next future However

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