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Astro Seminar: Time-Dependent Calculations with Cloudy: Application to Coronal Line Emission in NGC 4696

Date:
-
Location:
CP179
Speaker(s) / Presenter(s):
Marios Chatzikos (University of Kentucky)
	The nature of cooling in galaxy cluster has been puzzling since cool
core clusters were first discovered.  Even though early X-ray observations
suggested copious amount of cooling, optical observations failed to detect star
formation at the levels suggested by X-rays.  More recently, dispersed
spectroscopy with Chandra and XMM-Newton has revealed a dearth of gas below
1/3 of the mean cluster temperature.  Heating mechanisms have been invoked
to account for the temperature floor and residual star formation, but the
details remain unclear.
	Probes for the hot X-ray (~10 MK), cool optical (~10,000 K), and
intermediate temperature (~100,000 -- 1 million K) phases are necessary to
unravel the balance between heating and cooling in clusters.  Recently, coronal
line emission from gas of ~1 million K has been reported near NGC 4696, the
Brightest Cluster Galaxy in the Centaurus galaxy cluster.  By contast, gas at 2
million K was not detected.
	In this talk I build upon a new facility in Cloudy that allows for
time-dependent, non-advective simulations.  I use this capability to follow
a parcel of gas as it cools from ~80 MK to ~10,000 K.  I show that the lack
of 2 million K gas is not due to extinction.  I use the observed upper limit
to place an upper limit to the temperature of the coronal gas, and find that, if
the gas is cooling, it is cooling isochorically.  I discuss scenarios for the
origin of the coronal gas, and propose observational probes for gas at
temperatures between a million and 10,000 K, that could shed some light into
cooling processes in galaxy clusters.
Event Series: