Dr. Ignacio Mendigutia

CAB, INTA-CSIC, Spain

Accretion rates as a link between different astronomical scales

Abstract:

The mass accretion rate is a fundamental parameter as it determines the growth and evolution of the astrophysical objects under analysis. During the first part of the talk I will focus on the smallest -planetary- scales. Despite of the fact that the number of known exoplanets around stars different than the Sun has increased exponentially during the last decades, the detection of forming -accreting- planets in protoplanetary disks around young stars remains merely anecdotal, with only a few candidates proposed to date. The pre-main sequence stars HD 100546 and LkCa 15 are two of the most representative, given that their circumstellar disks may host (proto-) planetary systems with several planets each. I will show some of the main properties of HD 100546 as we inferred from different instrumentation and observational techniques. I will also discuss the potential of spectro-astrometry to detect planets in formation based on recently obtained ISIS/WHT data of LkCa 15. The intermediate -stellar- scales will be the topic of the second part of the talk. I will summarize some of our related work, focusing on the observational evidence that suggests that the accretion mechanism could change from “magnetospheric accretion” in young, low-mass T-Tauri and Herbig Ae stars to direct disk-to-star “boundary layer” accretion in Herbig Be and more massive young stellar objects. Finally, the third part of the talk will be devoted to link individual young stars with larger scales. We have recently found a statistically significant, roughly linear correlation between the rate of gas transformed into stars and the mass of dense gas directly involved on star formation, ranging 16 orders of magnitude and encompassing au-size circumstellar disks, pc-size protostellar-hosting clouds within our Galaxy, and kpc-size cloud-hosting galaxies. I will describe the “bottom-up” hypothesis we propose to explain this finding, according to which the protostellar accreting population drives the correlation for all scales.

Location:To be confirmed (31 Fitzwilliam Place/ Burlington Road)

Upcoming seminars:
https://www.dias.ie/2018/03/07/astronomy-and-astrophysics-seminar-schedule-2018/