Protoplanetary disk evolution in nearby star-forming regions

Álvaro Ribas Gómez

Departamento de Astrofísica

Año 2015

The main aim of this work is to better understand the evolution of protoplanetary disks around young stars in the solar neighborhood. It comprises three rst authored published papers, a fourth paper about to be submitted, and additional research as participation in six other refereed papers, which I coauthored during the period of this thesis. To asses disk evolution homogeneously, we compile a large sample of more than 2 300 members of 22 young (<100 Myr) nearby (<500 pc) star-forming regions and associations. All these objects have spectroscopic con rmation of membership to their host young association and measurements of their spectral types, which is complemented with photometry from up to 35 di erent lters covering from near ultraviolet to mid-infrared wavelengths. After considering possible biases, we consistently estimate the fraction of disks as a function of age. We obtain a characteristic disk lifetime of 3 Myr, in agreement with previous studies. We also nd that disk dispersal occurs in 1 Myr and tentative evidence of this process acting from inside out, suggesting that photoevaporation plays an important role in disk evolution. The unprecedented size of this sample provides the most robust con rmation up to date of a dependence of disk evolution with stellar mass, with T Tauri stars maintaining their disks for longer periods than Herbig Ae/Be stars. This result may have an important in uence on planet formation and exoplanetary populations. It may also represent the rst direct link achieved between a statistical property of protoplanetary disks and a statistical property of the exoplanetary systems at later phases, and constitutes one of the big new results from this thesis. We also explore the population of young disks in the Chamaeleon star-forming complex with Herschel data, in particular focusing on transitional disks in Chamaeleon I. We nd that the six transitional targets in the sample detected with Herschel have 70 m excesses higher than 75% of the Class II objects in the region. Further modeling of these disks reveals that Herschel SPIRE photometry can be used to e ciently constrain the mass of dust in these sources, one of the most relevant parameters for planet formation. The modeling also shows evidence for anomalous outer regions of transitional objects when compared to full protoplanetary disks.

Datos de interés

Supervisores: Bruno Merín Martín, Hervé Bouy
Universidad: UAM. Departamento de Física Teórica; Centro de Astrobiología
Fecha de lectura: 24/07/2015