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Physical properties of dusty protoplanetary disks in Lupus: Evidence for viscous evolution?

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Testi, L 
Natta, A 
Ansdell, M 
Carpenter, J 


Context. The formation of planets strongly depends on the total amount as well as on the spatial distribution of solids in protoplanetary disks. Thanks to the improvements in resolution and sensitivity provided by ALMA, measurements of the surface density of mm-sized grains are now possible on large samples of disks. Such measurements provide statistical constraints that can be used to inform our understanding of the initial conditions of planet formation. Aims. We aim to analyze spatially resolved observations of 36 protoplanetary disks in the Lupus star forming complex from our ALMA survey at 890 μm, aiming to determine physical properties such as the dust surface density, the disk mass and size, and to provide a constraint on the temperature profile. Methods. We fit the observations directly in the uv-plane using a two-layer disk model that computes the 890 μm emission by solving the energy balance at each disk radius. Results. For 22 out of 36 protoplanetary disks we derive robust estimates of their physical properties. The sample covers stellar masses between ∼0.1 and ∼ 2 M o , and we find no trend in the relationship between the average disk temperatures and the stellar parameters. We find, instead, a correlation between the integrated sub-mm flux (a proxy for the disk mass) and the exponential cut-off radii (a proxy of the disk size) of the Lupus disks. Comparing these results with observations at similar angular resolution of Taurus-Auriga and Ophiuchus disks found in literature and scaling them to the same distance, we observe that the Lupus disks are generally fainter and larger at a high level of statistical significance. Considering the 1-2 Myr age difference between these regions, it is possible to tentatively explain the offset in the disk mass-size relation with viscous spreading, however with the current measurements other mechanisms cannot be ruled out.



protoplanetary disks, submillimeter: general, stars: pre-main sequence

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Astronomy and Astrophysics

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EDP Sciences
European Research Council (341137)
M.T. and L.T. acknowledge support by the DFG cluster of excellence Origin and Structure of the Universe (www.universe-cluster. de). This work has been supported by the DISCSIM project, grant agreement 341137 funded by the European Research Council under ERC-2013-ADG. M.T. and L.T. thank Eva Wirström, the Gothenburg Centre for Advanced Studies in Science and Technology and the participants of the workshop Origins of Habitable Planets hosted at Chalmers (Gothenburg) in June 2016 where considerable part of this work was fruitfully discussed. M.T. is grateful to Cathie Clarke for insightful discussions. The fits have been carried out on the computing facilities of the Computational Center for Particle and Astrophysics (C2PAP) as part of the approved project “Dust evolution in protoplanetary disks”. M.T. acknowledges usage of the Max Planck Gesellschaft Hydra computing cluster for code testing, for which is grateful to Paola Caselli. Figures have been generated using the Python-based matplotlib package (Hunter 2007). Staircase plots of PDFs have been generated with a user-modified version of the Python-based triangle package (Foreman-Mackey et al. 2014). This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. This work was partly supported by the Italian Ministero dell’ Istruzione, Università e Ricerca through the grant Progetti Premiali 2012 – iALMA (CUP C52I13000140001). A.N. acknowledges funding from Science Foundation Ireland (Grant 13/ERC/I2907). C.F.M. acknowledges an ESA Research Fellowship. This paper makes use of the following ALMA data: ADS/JAO.ALMA#2013.1.00220.S, ADS/JAO.ALMA#2013.1.00226.S. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), NSC and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ