Tracey Hill (CEA/Saclay)

Filaments, ridges and mini-starbusts, Herschel's insight into high-mass star formation.-- Tracey Hill Colloquium

Marsfield Lecture Theatre

Abstract

With its unprecedented spatial resolution and high sensitivity, Herschel is revolutionising our understanding of high-mass star formation and the interstellar medium (ISM). In particular, Herschel is unveiling the filamentary structure and molecular cloud constituents of the ISM where
star formation takes place. The Herschel Imaging Survey of OB Young Stellar objects key program targets burgeoning young stellar objects with the aim of characterising them and the environments in which they form. HOBYS has already proven fruitful with many clear examples of high-mass star formation in nearby molecular cloud complexes.

Through multi-wavelength Herschel observations I will introduce some of the regions of the HOBYS program, including Vela C, M16, W48, Rosette and DR21. These works draw together a comprehensive data set with which to study the initial conditions of star formation. For example, these
data are rich with filamentary structures and a wealth of sources which span a large mass range from low to high-mass objects in the pre-collapse of protostellar phase of formation.

In Vela C, high-mass star formation proceeds preferentially in high column density supercritical filaments, called ridges, which may result from the constructive convergence of flows. I will also
present the latest Herschel results from the Eagle Nebula (M16), which trace the cold, dense early prestellar phase of star formation, and their natal filaments in this star-forming complex. The nearby OB cluster NGC6611 serves to heat the local stellar neighbourhood, which is
clearly seen in the dust temperature gradient running away from the centre of the cavity carved out by this cluster. Two prominent filaments are heated by the NGC 6611 cluster to a depth of 10-15pc. I will discuss the implications that this has on the future sites of star formation, modifying the initial conditions for collapse and casting doubt on the
evolutionary criteria as drawn from spectral energy distributions .