From NASA Chandra: “Cases of Black Hole Mistaken Identity”

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From NASA Chandra

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X-ray: NASA/CXC/Penn State/B.Luo et al; Illustration: NASA/CXC/M. Weiss

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Credit: NASA/CXC/Penn State/B.Luo et al.

Astronomers have discovered over two dozen growing supermassive black holes that had been misidentified before.

This result used data from several telescopes including NASA’s Chandra X-ray Observatory, and the Hubble and Spitzer Space Telescopes.

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NASA/Spitzer Infrared Telescope. No longer in service

The 28 supermassive black holes were found in the Chandra Deep Field-South, the deepest X-ray image ever obtained.

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Image credit: X-ray: NASA/CXC/U.Hawaii/E.Treister et al; Infrared: NASA/STScI/UC Santa Cruz/G.Illingworth et al; Optical: NASA/STScI/S.Beckwith et al.
This composite image from NASA’s Chandra X-ray Observatory and Hubble Space Telescope (HST) combines the deepest X-ray, optical and infrared views of the sky. Using these images, astronomers have obtained the first direct evidence that black holes are common in the early Universe and shown that very young black holes grew more aggressively than previously thought.
Astronomers obtained what is known as the Chandra Deep Field South (CDFS) by pointing the telescope at the same patch of sky for over six weeks of time. The composite image shows a small section of the CDFS, where the Chandra sources are blue, the optical HST data are shown in green and blue, and the infrared data from Hubble are in red and green.
The new Chandra data allowed astronomers to search for black holes in 200 distant galaxies, from when the Universe was between about 800 million and 950 million years old. These distant galaxies were detected using the HST data and the positions of a subset of them are marked with the yellow circles (roll your mouse over the image above).
The rest of the 200 galaxies were found in other deep HST observations located either elsewhere in the CDFS or the Chandra Deep Field North, a second ultra- deep Chandra field in a different part of the sky.
None of the galaxies was individually detected with Chandra, so the team used a technique that relied on Chandra’s ability to very accurately determine the direction from which the X-rays came to add up all the X-ray counts near the positions of these distant galaxies. The two “stacked” images resulting from this analysis are on the right side of the graphic, where the bottom image shows the low-energy X- rays and the top image has the high-energy X-rays. Statistically significant signals are found in both images.
These results imply that between 30% and 100% of the distant galaxies contain growing supermassive black holes. Extrapolating these results from the relatively small field of view that was observed to the full sky, there are at least 30 million supermassive black holes in the early Universe. This is a factor of 10,000 larger than the estimated number of quasars in the early Universe.
The stronger signal in high-energy X-rays implies that the black holes are nearly all enshrouded in thick clouds of gas and dust. Although copious amounts of optical light are generated by material falling onto the black holes, this light is blocked within the core of the black hole’s host galaxy and is undetectable by optical telescopes. However, the high energies of X-ray light can penetrate these veils, allowing the black holes inside to be studied.

The discovery has important implications for understanding how supermassive black holes grow and evolve over billions of years.

A team of researchers has identified a group of black holes that had previously been mistaken for a different kind of black hole, as described in our latest press release. This discovery has important implications for understanding how supermassive black holes grow and evolve over billions of years.

The misjudged black holes were found in the Chandra Deep Field-South (CDF-S), the deepest X-ray image ever taken. The main panel of the graphic shows the CDF-S, which contains over 7 million seconds of observing time from Chandra collected over many years. In this image, red, green, and blue represent the low, medium, and high-energy X-rays that Chandra can detect. Most of the points in this image are a black hole.

This latest work combines X-rays from Chandra in the CDF-S with large amounts of data at different wavelengths from other observatories, including NASA’s Hubble Space Telescope and NASA’s Spitzer Space Telescope. The team looked at black holes located 5 billion light years or more away from Earth in this patch of sky. At these distances, scientists had already found 67 heavily obscured, growing black holes with both X-ray and infrared data in the CDF-S. In this latest study, the authors identified another 28, highlighted by circles in a labeled version of the image. Optical and infrared images for four of these 28 are shown in a separate graphic.

These 28 supermassive black holes were previously categorized differently — either as slowly growing black holes with low density or nonexistent cocoons, or as distant galaxies. Supermassive black holes grow by pulling in surrounding material, which is heated and produces radiation at a wide range of wavelengths including X-rays. Many astronomers think this growth includes a phase, which happened billions of years ago, when a dense cocoon of dust and gas covers most black holes. These cocoons of material, which are the fuel source that enables the black hole to grow and generate radiation, are depicted in the artist’s illustration in the inset. The cocoon (red) surrounds a disk of material falling onto the black hole, plus a wind of material (blue) blowing away from the disk. A portion of the cocoon is cut out to show the heavily obscured black hole.

These results are important for theoretical models estimating the number of black holes in the universe and their growth rates, including those with different amounts of obscuration. Scientists design these models to explain a uniform glow in X-rays across the sky called the “X-ray background,” first discovered in the 1960s. Individual growing black holes observed in images like the CDF-S account for most of the X-ray background.

A paper reporting the results of this study is being published in The Astrophysical Journal. The other authors of the paper are Erini Lambrides (Johns Hopkins University in Baltimore, Maryland), Marco Chiaberge (Space Telescope Science Institute in Baltimore, Maryland), Roberto Gilli (National Institute of Astrophysics in Bologna, Italy), Timothy Heckman (Johns Hopkins), Fabio Vito (Pontificia Universidad Católica de Chile in Santiago), and Colin Norman (Johns Hopkins).


A Quick Look at Cases of Black Hole Mistakenly identified.

The above referenced press release is by
Media contacts:
Megan Watzke
Chandra X-ray Center, Cambridge, Mass.
617-496-7998
mwatzke@cfa.harvard.edu

See the full article here .


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NASA’s Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra’s science and flight operations from Cambridge, Mass.