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Fun and Games with HeI* Absorption Lines in Quasars

Event Details

Event Dates: 

Friday, March 21, 2014 - 12:00pm

Seminar Location: 

  • CASA Conference Room C324

Speaker Name(s): 

Karen Leighly

Speaker Affiliation(s): 

University of Oklahoma
Seminar Type/Subject

Scientific Seminar Type: 

  • Astrophysics Lunch Seminar

Event Details & Abstract: 

In 2011, we presented the discovery of the first HeI*10830 broad absorption line quasar, FBQS J1151+3822. While writing that paper, we came to appreciate the tremendous diagnostic power of HeI* in low redshift BALQSOs. While helium is common in astronomical gas, metastable helium (i.e., neutral helium with an electron in the 2s state) is relatively rare. This is important because a main barrier to determining the kinetic luminosity of the outflow (and therefore its role in galaxy feedback) is constraining the column density of the UV-absorbing gas. So, while absorption lines such as CIV, commonly used to identify BALQSOs, become saturated at low column density, HeI* remains unsaturated until high column densities are attained, and the column density can be estimated in some cases. Moreover, the combination of the 2s->2p transition at 10830 Angstroms with the 2s->3p transtion at 3889 Angstroms means that we can measure the outflow covering fraction, and start to make sense of partial covering in quasar outflows. In this presentation, I will discuss results from recent and ongoing projects that use HeI* absorption to understand the astrophysics of quasar outflows.