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| HEA Research: Hot Gas and Outbursts from SMBH's in Galaxies | ||||
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Elliptical galaxies lack the cool gas and luminous stars at large
galactic radii which have been used so successfully to measure the
masses of spiral galaxies. However, from early Einstein observatory
X-ray observations, SAO scientists Forman, Jones and Tucker found that
luminous elliptical galaxies have a corona of hot (10e7 degrees K)
gas. Through X-ray observations which measure the gas density and
temperature of this hot interstellar medium, one can determine the
mass and distribution of the dark matter required to gravitationally
bind the hot gas to the galaxy. Hot coronae have been found around
nearly all normal luminous ellipticals as well as around some, more
distant, radio galaxies.
The centers of galaxies often produce prodigious amounts of radiation, particularly at radio, X-ray and gamma-ray energies. While all galaxies may have passed through an active phase, we know that all galaxies with large bulges harbor a giant black hole at their center. Recent outbursts from the supermassive black holes in the galaxy cores can be caused either by the cooling of gas from the hot coronae or by the merger of another galaxy. The elliptical galaxy NGC4636 (see image) shows X-ray cavities outlined by arms caused by a nuclear outburst, likely powered by cooling gas, while the jet and lobe, seen in both the X-ray and radio images of Centaurus A (see image) are likely the result of cold matter accreted onto the supermassive black hole from the merger of a gas-rich spiral. Project Links CfA scientists actively working on X-ray observations of nearly normal elliptical galaxies and their supermassive black holes and their current projects include:
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The X-ray image of the elliptical galaxy NGC4636 shows cavities
surrounded by X-ray arms east and west of the galaxy center.
 X-ray image of Cen A shows a spectacular jet extending northest from the nucleus. | ||
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