GG Tau A:
Morphology and kinematics, gas and dust
inside the cavity, rings and gaps
Nguyen Thi Phuong, Anne Dutrey, Pham Ngoc Diep et al.,EAYAM17, Ishigaki/Japan, November, 20171

CONTENT
1. Introduction
2. Morphology and kinematics of 13CO(3-2) emissions
across the disc
3. High resolution observations
4. Summary2

Introduction
GG TAU140 pc, 2-3 Myr
GG Tau A (a binary, 0.26’’ or 38 au - 1.3 Msun)
GG Tau A/B (10’’ or 1400 au)

GG Tau B (a binary, 1.4’’ or 180 au – 0.17 Msun)

Guilloteau+1999 typical of T Tauri binary systems
GG TAU A - a triple system itself,
cavity of 190 au, i~ 37o, PA ~8o
GG Tau Ab1~ 0.38 Msun

GG Tau Aa~ 0.6 Msun

GG Tau Ab2~ 0.3 Msun

Morphology? Kinematics? Planet formation in multiple stellar system?

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Morphology and kinematics
13CO(3-2) emission

General Features
The map of the integrated
intensity shows a clear ring ofgas surrounding the centralstars (similar to the dust
morphology).
It displays no central emission,
with an abrupt inner cut-off
at 1 arcsec and no significant
emission inside r<0.54 arcsec.

The aspect ratio
corresponds to a tilt
𝛳=cos−1(1.45/1.19)=35◦
with respect to the sky
plane of a circular ringa0=1.45, b0=1.19
𝜑0=97.8o

The velocity map displays
a clear velocity gradientalong the major axis of
the ellipse, as expectedfrom rotation of the tilted
disc about its axis.
4r-dependence of the integrated intensity in the discplane is well described by the sum of 3 Gaussians.
0. 54 < r < 2 arcsec
Hot spotSE<I>=0.39(rms=17%)

𝜑-dependence of integrated
intensity in the disc planeshow an uniform
distribution over the disccircumference.

The map in the disc plane of the difference between
the measured integrated intensity and its value atthe same value of r gives strong evidence for an
excess associated with the hot spot and for anorthern depression of similar amplitude.
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Estimate of the disc thickness
In the optically thin approximation, the effect of disc thickness essentially cancels
on the major axis (90o and 270o); on the minor axis (0o and 180o), it scales withthe product of the disc thickness by the sine of the tilt angle.
0o
We estimate the thickness of the disc by comparing the valueof the smearing of the inner edge of the disc map near themajor axis of the ellipse with its value near the minor axis.

270o

90o
180o

To 95% confidence level we obtain an
upper limit of 0.24 arcsec (34 au) for
the scale height H(r) at r=1 arcsec(140 au) where the Keplerian velocity
is ~3 kms−1; at 30 K, the soundvelocity is0.5
kms−1andhydrostatic equilibrium implies
H(r) = 0.5/3 = 0.17 arcsec comparedwith the 0.24 arcsec obtained above.
6Gas kinematics and line width
In the disc plane (x, 𝜁 )Vz = sin𝜃 (Vrotsin𝜔 − Vfallcos𝜔 )Vfall (level <~9%) can be neglected
Vrot = Vz(sin𝜃 sin𝜔)−1Vrot becomes trivially singular along the 𝜁 axis.
We need to require |sin𝜔|>0.7 when calculating Vrot which
we find of the form Vrot=3.1 r −0.51 km s-1
In each pixel we define dVz as the difference between
Vz and its mean value in the pixel. A Gaussian fit tothe measured distribution gives 𝜎Vz=0.23 km s−1.
Vrot=3.1 r−0.51|sin𝜔|>0.7

𝜎K: Keplerian shear, ~ 0.09 km s−1
𝜎I: Instrumental resolution,

0.09 km s−1
𝜎T: Thermal broadening, possibly
including a turbulence contribution,and opacity broadening, 𝜎𝜏,~0.15 km s−1 (T=18K, 𝜏 =10)𝜎Vz = 0.20 km s−1 expected, compare with 0.23 measured

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𝜎Vz= 0.26 km s−1 in 1.3<r<1.7 arcsec
𝜎Vz= 0.18 km s−1 in 2.1<r<2.3 arcsec
Suggesting an increase of the temperature and opacity (T, 𝜏) towards the stars,from (18K, 5) at r ~2.2 arcsec to (36K, 10) at r ~1.5 arcsec (meaning 0.18 and0.25 kms−1 )Significant correlation is observed between
fluctuations of the line
width and of the integrated intensity.

N. T. Phuong et al., 2017 (submitted to RAA)

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Summary
Evidence for rotating gas and concentric/coplanar dust rings is obtained
A 95% CL upper limit of 0.24 arcsec (34 au) is placed on the disc scale height at adistance of 1 arcsec (140 au) from the central stars
Evidence for Keplerian rotation of the gas disc is presented, the rotation velocity
reaching 3.1 kms−1 at 1 arcsec from the stars, and a 99% CL upper limit of 9% isplaced on a possible in-fall velocity relative contribution.
Variations of the intensity across the disc area are studied in detail and confirm
the presence of a hot spot in the south-eastern quadrant. Other significant
intensity variations, in particular a depression in the northern direction, are alsorevealed.
Contributions from temperature/opacity, Kepler shear and spectral resolution
account well for the observed line width, which is found to be independent from 𝜔and to increase as r
decreases, suggesting the presence of a radial
temperature/opacity gradient from (18K, 5) at 2.2” to (36K, 10) at 1.5” in excellent
agreement with observation.
New observations with angular resolution of 30 au show optimistic prospects toreveal detail features.

Thank you for your attention!

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