Properties of the cool molecular filaments in Perseus A
Date Issued
2009
Date
2009
Author(s)
Ho, I-Ting
Abstract
The first Sub-millimeter Array (SMA) observation of Perseus A (Lim et al. 2008), the central elliptical galaxy in the Perseus cluster at a resolution of ~3" (~1 kpc) revealed that its molecular gas is concentrated primarily in three radial filaments extending out to ~10 kpc in the east-west direction. The two outer filaments, the Eastern and Western filament, have kinematics that can be reproduced by free-fall in the gravitational potential of Perseus A, indicating that they originate from an X-ray cooling flow in the cluster. Results from two follow-up observations are presented in this thesis. otivated by the single-dish observation (Salome et al. 2006) that shows molecular gas extending out to ~14 kpc east-west, the second observation imaged the entire east-west extension of the molecular gas at the same resolution (Ho et al. 2009). No new features were found outside the previous field of view, and two of the previous features to the north and south were found to be sidelobes artifacts. A total of six genuine features is shown to comprise radially aligned filaments, which are most naturally explained by the infall motion proposed by (Lim et al. 2008). All the detected filaments coincide with locally bright H-alpha features, and have nearly constant ratio of CO(2-1) to H-alpha luminosity of ~10^-3, suggesting a common heating mechanism to the ionize gas and molecular gas. These filaments are found to be gravitationally bound, and should collapse on timescales <10^6 yr, much shorter than the dynamical ages of the two longest filaments of ~10^7 yr. Tidal shear may help delay their collapse, but more likely turbulent velocity of at least tens of km/s or magnetic field with strength of at least several ~10 uG are required to support these filaments. o study the spatial kinematics of the three short filaments as well as the complex Inner filament, the third observation was conducted with the SMA in its extended configuration, providing images at resolution of ~1.5" (~500 pc). Our images to the eastern region first reveal velocity gradients in the two short filaments E1 and E2. The Eastern filament that radially aligned to E1 motivated us to model their kinematics as a single radial filament. By considering a pressure wave, produced by the central jet-inflated X-ray bubbles, passes through the infalling filament and therefore retards it, we can successfully reproduce the kinematics of not only the Eastern filament and E1, but also E2, suggesting that all observed molecular filaments in the eastern region originate from an X-ray cooling flow. Our images to the inner region reveal that the Inner filament comprise a compact central condensation and other four features aligned to the filaments in the eastern or western regions. The central condensation exhibits a north-south velocity gradient consistent, in both direction and sense, with the behavior of jet-entrained gas, indicating that the molecular gas genuinely accumulated in the nucleus, and therefore may be responsible for fueling the AGN.
Subjects
galaxy
cooling flow
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