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Using ionized flows in Orion to study the evolution of interstellar dust

Event Details

Event Dates: 

Friday, November 14, 2014 - 12:00pm

Seminar Location: 

  • CASA Conference Room C324

Speaker Name(s): 

Bram Ochsendorf

Speaker Affiliation(s): 

Seminar Type/Subject

Scientific Seminar Type: 

  • Astrophysics Lunch Seminar

Event Details & Abstract: 

Massive stars drive the evolution of the interstellar medium through their radiative and mechanical energy input. After their birth, they form "bubbles" of hot gas surrounded by a dense shell. Traditionally, the formation of interstellar bubbles is explained through the input of a powerful stellar wind, even though direct evidence supporting this scenario is lacking. Analysis of infrared data has revealed that a vast amount of interstellar bubbles show dust arcs or dust waves near the ionizing star which, as I will argue, demonstrates the importance of radiation pressure acting on an ionized gas flow through the bubble into the general interstellar medium. Dust waves provide a natural explanation for the long-standing problem on the presence of dust inside H II bubbles, offer a novel method to study dust in H II regions, and provide direct evidence that bubbles are relieving their pressure into the interstellar medium through a champagne flow.

During this talk I will briefly review the formation mechanism of interstellar bubbles, discuss signatures of dust waves and where to find them, and how we can exploit them to study the evolution of interstellar dust and its coupling to the gas. I will show that dust in the Orion IC434 HII region is very much different from that observed in the diffuse ISM. Indeed, the Orion region, due to its proximity and wealth of available data, provides an ideal benchmark case where all of the aforementioned phenomena are observed that allows us to pursue our research questions.