[Artist's Concept of AXAF]

A Study of ULXs

FIGURE CAPTION NGC 4485 and NGC 4490 are two of the 90 galaxies surveyed in a study of the Ultra-Luminous X-ray source (ULX) population of nearby galaxies. This image, taken with the Advanced CCD Imaging Spectrometer onboard the Chandra X-ray Observatory, shows numerous bright X-ray sources within clouds of cooler gas. Five of these point-like sources are potential ULXs --- candidates for intermediate-mass black holes. Blue colors in this image represent hotter, high-energy, emission while red colors denote cooler, low-energy, X-rays.

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Further Details: Optical (Digitized Sky Survey) image (left) and X-ray (Chandra) image (right). Large ovals represent the approximate boundaries of the galaxies (NGC 4490 is the larger of the two). Small circles indicate the brightest X-ray sources. The second source from the left, in the middle of NGC 4490, is the nucleus and thus does not qualify as a ULX but is an Active Galactic Nucleus. The galaxies are about 25 million light years away from Earth. North is up and East is to the left. The images cover approximately an 8x8 arcmin region of the sky.

The Digitized Sky Survey was produced at the Space Telescope Science Institute under U.S. Government grant NAG W-2166. The image is based on photographic data obtained using the Oschin Schmidt Telescope on Palomar Mountain and the UK Schmidt Telescope. The plates were processed into the present compressed digital form with the permission of these institutions.