Protoplanetary and debris disks in the η Chamaeleontis Association

A submillimeter survey obtained with APEX/LABOCA observations^★

¹ INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
e-mail: veronica.roccatagliata@inaf.it
² Department of Physics “E. Fermi”, University of Pisa, Largo Bruno Pontecorvo 3, 56127 Pisa, Italy
³ INFN, Sezione di Pisa, Largo Bruno Pontecorvo 3, 56127 Pisa, Italy
⁴ SUPA, School of Science and Engineering, University of Dundee, Nethergate, DD1 4HN, Dundee, UK
⁵ Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
⁶ Centre for Exoplanets and Habitability, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
⁷ European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany
⁸ Purple Mountain Observatory, Chinese Academy of Sciences, 10 Yuanhua Road, Nanjing 210023, PR China
⁹ School of Science, University of New South Wales, Canberra, ACT 2600, Australia
¹⁰ Institute of Theoretical Physics and Astrophysics, University of Kiel, Leibnizstraße 15, 24118 Kiel, Germany
¹¹ Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany

Received: 14 April 2023
Accepted: 30 September 2023

Abstract

Context. Nearby associations are ideal regions to study coeval samples of protoplanetary and debris disks down to late M-type stars. Those aged 5–10 Myr, where most of the disk should have already dissipated forming planets, are of particular interest.

Aims. We present the first complete study of both protoplanetary and debris disks in a young region, using the η Chamaeleontis (η Cha) association as a test bench to study the cold disk content. We obtained submillimeter data for the entire core population down to late M-type stars, plus a few halo members.

Methods. We performed a continuum submillimeter survey with APEX/LABOCA of all the core populations of the η Cha association. These data were combined with archival multiwavelength photometry to compile a complete spectral energy distribution. The disk properties were derived by modeling protoplanetary and debris disks using RADMC 2D and DMS, respectively. We compute a lower limit of the disk millimeter fraction, which is then compared to the corresponding disk fraction in the infrared for η Cha. We also revisit and refine the age estimate for the region, using the Gaia eDR3 astrometry and photometry for the core sources.

Results. We find that protoplanetary disks in η Cha typically have holes with radii on the order of 0.01–0.03 AU, while ring-like emission from the debris disks is located between 20 and 650 au from the central star. The parallaxes and Gaia eDR3 photometry, in combination with the PARSEC and COLIBRI isochrones, enable us to confirm an age of η Cha between 7 and 9 Myr. In general, the disk mass seems insufficient to support accretion over a long time, even for the lowest mass accretors, a clear difference with other regions and also a sign that the mass budget is further underestimated. We do not find a correlation between the stellar masses, accretion rates, and disk masses, although this could be due to sample issues (very few, mostly low-mass objects). We confirm that the presence of inner holes is not enough to stop accretion unless accompanied by dramatic changes to the total disk mass content. Comparing η Cha with other regions at different ages, we find that the physical processes responsible for debris disks (e.g., dust growth, dust trapping) efficiently act in less than 5 Myr.