Multiwavelength images of the birth of a "mini-quasar" eight million years ago in X-ray galaxy CXO-J141741.9

These views of the X-ray galaxy CXO-J141741.9 show a "mini-quasar" in the act of being created some 8 billion years ago. The four images were taken with different satellite telescopes. The Hubble image at top-left (panel a) shows several galaxy fragments plus a bright "mini-quasar," visible as the bright point source that dominates the upper-left fragment. The infrared image at bottom left (panel c) was taken with the Spitzer/MIPS camera at 24 microns. 24 microns is heat radiation, and the bright point source in this image shows hot dust that has been heated by the quasar and by a giant burst of star formation that was triggered by the merger. This new star formation is buried deep within absorbing dust clouds, however, and is largely invisible in the Hubble image. It can be seen only in the infrared, where dust absorbs less.

A second, shorter-wavelength Spitzer image from the IRAC camera is shown at the upper right (panel b). This shows light coming both from the hot dust and the quasar. Finally, the color image from the Chandra X-ray satellite at lower-right (panel d) shows a very bright X-ray source. The X-ray source is centered in the dashed circle in panel a, showing that it is coincident with the quasar. The X-rays are being emitted by a tiny but fiercely bright disk of million-degree gas that has been heated by falling in close to a massive central black hole. This gas is on its way into the hole and will soon be swallowed up by it, just as water swirls around a drain but finally falls in.

Each panel of the image has the same field of view of approximately 1 million by 1 million light years (40" x 40"). Other galaxies are visible in the field; some of these are true neighbors of CXO-J141741.9 but most are foreground and background galaxies projected along the line of sight. Spectroscopic redshifts are needed to identify the true neighbors, as they will have redshifts (and therefore distances) nearly identical to CXO-J141741.9. Close inspection shows other galaxies that appear in the multiple images besides CXO-J141741.9. The overlap is especially clear between panels a) and b). This comparison shows just how unusual CXO-J141741.9 is. Most galaxies do not radiate nearly as strongly in X-rays or at infra-red wavelengths as CXO-J141741.9. Its unique properties are due to the accreting black hole. These other galaxies may possess black holes, but they are not radiating because no gas is falling in. We believe it is the merger of galaxy fragments that has triggered the massive infall of gas in CXO-J141741.9, lighting up its black hole.

The images show how telescopes at different wavelengths are needed to tell the whole story of a galaxy. The spatial detail of the Hubble image is needed to spot the gravitational interaction that triggered the mini-quasar and starburst. Chandra X-rays are needed to measure the luminosity of the mini-quasar, while Spitzer images reveal radiation from that and from the ongoing burst of star formation. Our understanding of this object would be seriously incomplete if any of these data were missing. The ability to look at thousands of galaxies this way simultaneously in different wavebands from X-rays to radio wavelengths is what makes the AEGIS Survey so valuble. No other region of the sky has such deep and wide-ranging coverage over such a large area.