Chandra Deep Field South
Credit: X-ray: NASA/CXC/Penn State/B.Luo et al.
Credit: X-ray: NASA/CXC/Penn State/B.Luo et al.
This is the deepest X-ray image ever obtained, made with over 7 million seconds of observing time with NASA's Chandra X-ray Observatory.
These data give astronomers the best look yet at the growth of black
holes over billions of years beginning soon after the Big Bang, as
described in our latest press release.
The image is from the Chandra Deep Field-South, or CDF-S. The full
CDF-S field covers an approximately circular region on the sky with an
area about two-thirds that of the full Moon. However, the outer regions
of the image, where the sensitivity to X-ray emission is lower, are not
shown here. The colors in this image represent different levels of X-ray energy
detected by Chandra.
Here the lowest-energy X-rays are red, the medium
band is green, and the highest-energy X-rays observed by Chandra are
blue.
The central region of this image contains the highest concentration of supermassive black holes
ever seen, equivalent to about 5,000 objects that would fit into the
area of the full Moon and about a billion over the entire sky.
Researchers used the CDF-S data in combination with data from the
Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey (CANDELS)
and the Great Observatories Origins Deep Survey (GOODS), both including
data from NASA's Hubble Space Telescope to study galaxies and black
holes between one and two billion years after the Big Bang.
In one part of the study, the team looked at the X-ray emission from
galaxies detected in the Hubble images, at distances between 11.9 and
12.9 billion light years
from Earth. About 50 of these distant galaxies were individually
detected with Chandra. The team then used a technique called X-ray
stacking to investigate X-ray emission from the 2,076 distant galaxies
that were not individually detected. They added up all the X-ray counts
near the positions of these galaxies, enabling much greater sensitivity
to be obtained. Through stacking the team were able to achieve
equivalent exposure times up to about 8 billion seconds, equivalent to
about 260 years.
Using these data, the team found evidence that black holes in the
early Universe grow mostly in bursts, rather than via the slow
accumulation of matter. The team may have also found hints about the
types of seeds that form supermassive black holes. If supermassive black
holes are born as "light" seeds weighing about 100 times the Sun's
mass, the growth rate required to reach a mass of about a billion times
the Sun in the early Universe may be so high that it challenges current
models for such growth. If supermassive black holes are born with more
mass, the required growth rate is not as high.
The data in the CDF-S
suggest that the seeds for supermassive black holes may be "heavy" with
masses about 10,000 to 100,000 times that of the Sun.
Such deep X-ray data like those in the CDF-S provide useful insights
for understanding the physical properties of the first supermassive
black holes. The relative number of luminous and faint objects — in what
astronomers call the shape of the "luminosity function" — depends on
the mixture of the several physical quantities involved in black hole
growth, including the mass of the black hole seeds and the rate at which
they are pulling in material. The CDF-S data show a rather "flat"
luminosity function (i.e., a relative large number of bright objects)
that can be used to infer possible combinations of these physical
quantities. However, definitive results can only come from further
observations.
The paper on black hole growth in the early Universe was led by Fabio
Vito of Pennsylvania State University in University Park, Penn and was
published in an August 10th, 2016 issue of the Monthly Notices of the
Royal Astronomical Society. It is available online [https://arxiv.org/abs/1608.02614].
The survey paper was led by Bin Luo, also of Penn State and was
recently accepted for publication in The Astrophysical Journal
Supplement Series. It is also available online [https://arxiv.org/abs/1611.03501]
Fast Facts for Chandra Deep Field South :
Scale: Image is 16 arcmin across (about 8.15 light years)
Category: Cosmology/Deep Fields/X-ray Background, Black Holes
Coordinates (J2000): RA 03h 32m 28s | Dec -27° 48' 30.00
Constellation: Fornax
Observation Date: 102 pointings between 1999 and 2016
Observation Time: 1944 hours 27 min
Obs. ID: 1431, 441, 582, 1672, 2239, 2312, 2313, 2405, 2406, 2409, 8591-8597, 9575, 9578, 9593, 9596, 9718, 12043-12055, 12123, 12128, 12129, 12135, 12137, 12138, 12213, 12218-12220, 12222, 12223, 12227, 12230-12234, 16175-16191, 16450-16463, 16620, 16641, 16644, 17416, 17417, 17535, 17542, 17546, 17552, 17556, 17573, 17633, 17634, 17677, 18709, 18719, 18730
Instrument: ACISReferences: Luo, B. et al, 2016, ApJS (in press); arXiv:1611.03501; Vito, F. et al, 2016, MNRAS, 463, 348; arXiv:1608.02614
Color Code: X-ray (Red, Green, Blue)
Distance Estimate: About 9 to 11 billion light years
Source: NASA’s Chandra X-ray Observatory
