Little Red Dot Abell2744-QSO1a (NIRCam Image with NIRSpec IFU Velocity Map)

An image detail from NIRCam on NASA’s James Webb Space Telescope shows the Little Red Dot Abell2744-QSO1, gravitationally lensed by Abell 2744, an enormous mega-cluster of galaxies also known as Pandora’s Cluster.

Pulled out to the right is a map showing the speed that gas is moving toward or away from the telescope (rotational velocity) in different parts of QSO1. The map was made with data collected using NIRSpec’s integral field unit (IFU), a combination of camera and spectrograph. The IFU gathers an image along with 900 spectra from a square patch of sky 3 arcseconds by 3 arcseconds, creating maps showing differences in brightness of thousands of wavelengths between 0.6-micron and 5.3-micron light across the object. The gas velocity is calculated based on Doppler shift: The colors are shifted slightly toward shorter (bluer) wavelengths where material is moving toward us, and longer (redder) wavelengths where it is moving away.

The Webb data shows that the glowing gas has Keplerian rotation: It is orbiting a central point in the same way that planets orbit a star. This means that most of the mass of QSO1 must reside in a single point in the center, i.e., a black hole. Because the velocity of the orbiting gas follows very simple laws of gravity, the data can then be used to calculate the mass of the black hole: It appears to be 50 million solar masses, or 50 million times the mass of our Sun. This is at least two-thirds of the entire mass of QSO1.

See the full NIRCam image and explore Webb’s NIRSpec IFU observation of QSO1 on Space Telescope Live.