NaCo Imaging Survey for Planets around Young Stars (NaCo-ISPY)

• Applicants: Dr. André Müller; Professor Dr. Andreas Quirrenbach
• Subject Area: Astrophysics and Astronomy
• Term: from 2017 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 362583816

We are currently undertaking a direct imaging survey (NaCo-ISPY) of young stars, using 120 nights of guaranteed observing time at the ESO VLT. The main goal of ISPY is understanding the formation and subsequent evolution of giant planets at large separations (> 5-10 au) from their parent stars. Our survey targets about 200 stars that have been carefully selected to form two samples of stars with disks: young (<10 Myr) stars with protoplanetary disks, and older (up to a few 100 Myr) stars with debris disks. ISPY is complementary to other current coronagraphic surveys in using the L wavelength band and the angular groove phase mask (AGPM) coronagraph. This ensures that we achieve the smallest possible inner working angle, and makes the survey more sensitive to very young planets, which are still embedded in their natal disks, and to older, cooler planets in debris disk systems. The main objective of the present proposal is realizing the full scientific potential of ISPY, by addressing the two most challenging aspects of coronagraphic surveys: optimizing the data reduction pipeline to achieve the highest possible contrast, and connecting the observational results to the underlying astrophysical questions.Building on our current data reduction tools, we intend to create a robust, reliable, and versatile data reduction pipeline that handles imperfections in the data correctly and implements a suite of sophisticated data reduction algorithms. At the limit of detectability against noise from stellar speckles, reliable planet discoveries hinge on cross-validation with independent methods. The goal of this work package is thus a uniform and comprehensive reduction of all data from ISPY, with the best detection limits achievable with state-of-the-art algorithms.We intend to perform end-to-end simulations of the ISPY survey in a Bayesian framework that connects these detections and detection limits to the underlying astrophysical quantities of interest, such as the planet mass function and its dependence on the orbital semi-major axis and the age of the parent star. Since the conversion of the observed number and brightness of planetary companions to an underlying planet mass function is strongly model dependent, our simulation package (dubbed ISPY-Sim) will include families of models capturing a wide range of assumptions on the initial conditions of the planet formation process, the subsequent dynamical and physical evolution, and on atmospheric properties. We will thus be able to look for correlations between these assumptions, to test their viability, and to quantify the uncertainties.By creating a catalog of optimally reduced high-contrast observations of stars with disks, and by implementing a systematic process of astrophysical inference from these data, we will thus be able to make a major contribution to answering the open questions about the number, formation process, and evolution of giant planets orbiting far from their parent stars.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1992: Exploring the diversity of extrasolar planets
• Co-Investigators: Dr. Ralf Launhardt; Privatdozentin Dr. Sabine Reffert