Distant Galaxies Hidden in Quasars' Glare
NASA | GSFC | STScI | JWST | 2020 Oct 14
Quasars are the brightest objects in the universe and among the most energetic. They outshine entire galaxies of billions of stars. A supermassive black hole lies at the heart of every quasar, but not every black hole is a quasar. Only the black holes that are feeding most voraciously can power a quasar. Material falling into the supermassive black hole heats up and causes a quasar to shine across the universe like a lighthouse beacon.
- These simulated images show how a quasar and its host galaxy would appear to NASA’s upcoming James Webb Space Telescope (top) and Hubble Space Telescope (bottom) at infrared wavelengths of 1.5 and 1.6 microns, respectively. Webb’s larger mirror will provide more than 4 times the resolution, enabling astronomers to separate the galaxy’s light from the overwhelming light of the central quasar. The individual images span about 2 arcseconds on the sky, which represents a distance of 36,000 light-years at a redshift of 7. Credits: M. Marshall (University of Melbourne)
Although quasars are known to reside at the centers of galaxies, it’s been difficult to tell what those galaxies are like and how they compare to galaxies without quasars. The challenge is that the quasar’s glare makes it difficult or impossible to tease out the light of the surrounding host galaxy. It’s like looking directly into a car headlight and trying to figure out what kind of automobile it is attached to.
A new study suggests that NASA’s James Webb Space Telescope, set to launch in 2021, will be able to reveal the host galaxies of some distant quasars despite their small sizes and obscuring dust.
“We want to know what kind of galaxies these quasars live in. That can help us answer questions like: How can black holes grow so big so fast? Is there a relationship between the mass of the galaxy and the mass of the black hole, like we see in the nearby universe?” said lead author Madeline Marshall ...
Answering these questions is challenging for a number of reasons. In particular, the more distant a galaxy is, the more its light has been stretched to longer wavelengths by the expansion of the universe. As a result, ultraviolet light from the black hole’s accretion disk or the galaxy’s young stars gets shifted to infrared wavelengths. ...
The Host Galaxies of z = 7 Quasars: Predictions from the BLUETIDES Simulation ~ Madeline A Marshall et al