Classroom Aid - Two Oldest Black Holes
Channel: David Butler
Date: 2023-11-23

Here’s a Webb infrared image of the galaxy cluster Abell 2744. There are hundreds of galaxies in the cluster, along with a few foreground stars. It’d redshift is 0.308. Light from this cluster took 3.62 billion years to get here. 
In this cluster, astronomers found a gravitationally lensed distant galaxy named UHZ1. To determine how far away this galaxy is, a technique called ‘dropout’ was used.  Here’s how it works. Hydrogen surrounding galaxies absorbs light with a wavelength around 100 nanometers. That’s blue light. The source will be easily visible with filtered viewing wavelengths longer than blue, but "drop out" with blue light filters. 
This is a standard photometric method for locating distant galaxies in deep field images. For UHZ1, Webb found the dropout with its F115W filter. The redshift needed to stretch blue light to this filter gives us the estimated distance. This galaxy’s redshift is 10.32 making its light travel distance 13.3 bly – just a bit further than CEERS 1019.
Here’s the Chandra X-ray Observatory’s overlay view of the area marked in purple. Using over two weeks of observations from Chandra, researchers were able to detect X-ray emission from the center of UHZ1. The X-rays come from a region that is much smaller than the galaxy. This is the signature of an accreting supermassive black hole at the center of the galaxy. 
The X-ray signal is extremely faint, but Chandra was able to detect it because the Abell 2744  gravitational lensing enhanced the signal by a factor of four. Based on the brightness and energy of the X-rays, it’s estimated mass falls well above 10 million suns. 
The extremely large masses of this SMBH and CEERS 1019, at such an early age of the Universe, has led to a conflict between the currently understood time it takes to form supermassive black holes, and the Lambda Cold Dark Matter Big Bang Cosmology time line.  Astronomers call this ‘tension’ between the two theories, indicating that one or both will need to change. In our final segment of this video book on Black Holes, we’ll cover a proposed change to how black holes can form that would relieve this tension.