1. 9-10 Aprile 2015 - Osservatorio Astronomico di Capodimonte
JEDI Meeting
9-10 Aprile Osservatorio Astronomico di Capodimonte
ALMA/JVLA observations of the dust properties across the
CO snowline in HD
G.Guidi, L.Testi, M.Tazzari
Greta Guidi
PhD student at INAF Arcetri/Università degli Studi di Firenze
Supv. L. Testi

2. Dust grains: the first step toward planet formation
Continuum emission from IR to millimeter comes from the dust:
[van Dishoeck+ 2014]
Grains larger than a few cm cannot be detected!

3. Resolving the CO snowline in a disk with ALMA: HD 163296
Herbig Ae star
Age ~ 5 Myr
M*=2,3 M☉
T*= 9500 K
L=36 L☉
d=122 pc
Mdisk~ 0,1 M☉
[Qi et al. 2013]
ALMA 835 μm
[TWHyd, Qi et al. 2013]
[Mathews et al. 2013]
Maybe DCO+ not the better tracer: N2H+ gives a CO snowline for HD at
100 AU ~ 0.8’’
[Qi 2015 in preparation]
H3+ + HD ⇔ H2D+ + H2+ ΔE
H2D+ + CO → DCO+
Emission ring of DCO+ : AU
CO condensation temperature:
19 K → 155 AU ~ 1,3’’

4. Grain growth across the snowline
[van Dishoeck 2014]

5. More compact emission at longer wavelengths
Observations
Beam 0.57’’x0.37’’
~ 60AU
Beam 0.74’’x0.60’’
~ 85AU
Beam 0.13’’x0.08’’
~ 15AU
Free-free electron emission becomes a non-negligible contribution at wavelengths ≳ 7 mm
More compact emission at longer wavelengths

6. Radial profiles of spectral index in the disk mid plane
850 μm mm
850 μm - 9 mm
Hypothesis:
Rayleigh-Jeans regime + optically thin emission

7. Radial profiles of spectral index in the disk mid plane
850 μm mm
850 μm - 9 mm

8. Dust emission reveals non-homogeneous features in the disk
Flux density radial profile
Residuals observations-model
[Contours at 3,6,12,24,48 σ]
Excess emission near the CO Snowline

9. Dust emission reveals non-homogeneous features in the disk
Major axis
[Polarized light contrast from Garufi et al. 2014]
[Garufi et al. 2014]
Polarized light shows a ring structure at ~0.6” -1”( AU)

10. The excess emission is not resolved at 1.3 mm?
ALMA Band 6 (1.3 mm)
ALMA Band 7 (0.85 mm)
Beam 0.74”x0.60”
Beam 0.74”x0.60”

11. Further developments
ALMA Cycle 3: high angular resolution/high signal to noise in Band 3
Measurement of the spectral index β(850 μm-3 mm)
JVLA K, X, C Bands (1.3 cm, 3 cm, 6 cm)
Resolve electrons free free emission
In the future… ALMA Band 2 (80GHz) and Band 1 (40GHz)
β(850 μm-7 mm)
New facilities with high signal to noise and high angular resolution in the range 35 GHz - 350GHz +
Improvement of disk models with radial dependent parameters
More detailed study of the radial properties of dust and grain growth

12. Thank you!