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**Note unusual day and time** HST/COS FUV spectroscopy of an Ha-emitting filament in M87, and a physical model for the structure of the filament

Event Details

Event Dates: 

Thursday, February 22, 2018 - 3:00pm

Seminar Location: 

  • JILA 10th Floor - Foothills Room

Speaker Name(s): 

Mike Anderson

Speaker Affiliation(s): 

Max Planck Institute for Astrophysics
Seminar Type/Subject

Scientific Seminar Type: 

  • Astrophysics Lunch Seminar

Event Details & Abstract: 

The Ha-emitting filaments in the cores of galaxy clusters are a surprising and mysterious phenomenon which seems to be connected to the cooling of the intracluster medium. We present new HST/COS G130M spectroscopy which we have obtained for a sightline towards one such filament projected 1.9 kpc from the nucleus of M87, near the edge of the inner radio lobe to the east of the nucleus. The combination of the sensitivity of COS and the proximity of M87 allow us to study the structure of this filament in unparalleled detail. We propose a new physical model for the filament. In our model, the filament is composed of many cold clumps, each surrounded by an FUV-emitting boundary layer, with the filament having a radius r ~ 10 pc and the clumps filling the cylinder with a low volume filling factor. The observed velocity dispersion in emission lines from the filament results from the random motions of these clumps within the filament. 

We also detect [Fe XXI] 1354A in emission at 4-5 sigma. Unlike the typical permitted FUV lines, this line is emitted from 1 keV (T ~ 10^7 K) plasma, and we use it to measure the bulk radial velocity and velocity dispersion of the plasma at this temperature. In contrast to the filament, [Fe XXI] is also blueshifted relative to M87 and matches the bulk velocity of a nearby filament to the S. We hypothesize that this line arises from the approaching face of the radio bubble expanding through this sightline, while the filament lies on the receding side of the bubbl