Hot and cold bubbles in M 87
نویسنده
چکیده
The X-ray data obtained with XMM-Newton is used to investigate the complex structure of the gas in the atmosphere of the Virgo cluster around M87. We construct a simple model for the temperature and density distribution. This model implies that the cumulative mass of the cluster gas is a power-law of its entropy index, kT n−2/3, similar to the Hydra cluster. This supports the idea that such power-laws are a direct consequence of gas cooling in a gravitational potential. In the cluster atmosphere hot bubbles of gas injected by the AGN are rising buoyantly. We estimate the age of these structures from the synchrotron radio data and find that this ‘radiative age’ is consistent with the estimated dynamical timescale. However, this requires a spatial separation of the relativistic particles from the magnetic field. The age estimates suggest an activity cycle of the AGN in M87 of roughly 108 years. We show that the largest radio structures are consistent with being the remnants of buoyant bubbles injected by the AGN during an even earlier activity cycle. The wakes behind the currently rising hot bubbles uplift cold gas from the cluster centre. Using a simple model for the trajectory of the cold gas, we demonstrate that the observations by XMM-Newton of a mix of hot and cold gas in the cluster atmosphere in the vicinity of the radio structure can be explained in this scenario. This may also explain the ridges of enhanced X-ray emission from cold gas observed with CHANDRA.
منابع مشابه
Bubbles and Superbubbles
An isolated massive star can blow a bubble, while a group of massive stars can blow superbubbles. In this paper, we examine three intriguing questions regarding bubbles and superbubbles: (1) why don’t we see interstellar bubbles around every O star? (2) how hot are the bubble interiors? and (3) what is going on at the hot/cold gas interface in a bubble?
متن کاملIs the Plasma within Bubbles and Superbubbles Hot or Cold?
I review what is known about the temperature of the plasma within stellar wind bubbles and superbubbles. Classical theory suggests that it should be hot, with characteristic temperatures of order a million degrees. This temperature should be set by the balance between heating by the internal termination shocks of the central stellar winds and supernovae, which expand at thousands of km s, and c...
متن کاملEvaluation of anti-melanogenic activity of Ziziphus jujuba fruits obtained by two different extraction methods
Background and objectives: Dried pulps and peels of Ziziphus jujuba fruits are commonly applied as food because of their high nutritional value. It has been widely used in traditional medicine as laxative, tonic, wound healing agent and appetizer. The aim of this study was to evaluate the anti-melanogenic effects of Z. jujuba fruit. Methods: </st...
متن کاملAn Inside-out View of Bubbles
Fast stellar winds can sweep up ambient media and form bubbles. The evolution of a bubble is largely controlled by the content and physical conditions of the shocked fast wind in its interior. This hot gas was not clearly observed until the recent advent of Chandra and XMM-Newton X-ray observatories. To date, diffuse X-ray emission has been unambiguously detected from two circumstellar bubbles ...
متن کامل