From AAS NOVA: “A Young Population of Hidden Jets”



1 July 2020
Susanna Kohler

Artist’s impression of a galaxy forming stars, as powerful jets that are flung from its central black hole collide with the surrounding matter. [ESO/M. Kornmesser]

Looking for a fireworks show this 4th of July? Try checking out the distant universe, where powerful jets flung from supermassive black holes slam into their surroundings, lighting up the sky. Though these jets are hidden behind shrouds of gas and dust, a new study has now revealed some of these young powerhouses.

A Galaxy–Black-Hole Connection

This composite image of Centaurus A shows an example of large-scale jets launched from an AGN, which can eventually extend far beyond the galaxy, as seen here. [ESO/WFI (Optical); MPIfR/ESO/APEX/A.Weiss et al. (Submillimetre); NASA/CXC/CfA/R.Kraft et al. (X-ray)]

Wide Field Imager on the 2.2 meter MPG/ESO telescope at Cerro LaSilla

MPG/ESO 2.2 meter telescope at Cerro La Silla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres

ESO/MPIfR APEX high on the Chajnantor plateau in Chile’s Atacama region, at an altitude of over 4,800 m (15,700 ft)

NASA/Chandra X-ray Telescope

In the turbulent centers of active galaxies (active galactic nuclei, or AGN), gas and dust rains onto supermassive black holes of millions to billions of solar masses, triggering dramatic jets that plow into the surrounding matter and light up across the electromagnetic spectrum.

The growth of a supermassive black hole is thought to be closely tied to the evolution of its host galaxy, and feedback like these jets may provide that link. As the jets collide with the gas and dust surrounding the galaxy’s nucleus, they can trigger a range of effects — from shock waves that drive star formation, to gas removal that quenches star formation.

To better understand the connections between supermassive black holes and their host galaxies, we’d especially like to observe AGN at a time known as Cosmic Noon. This period occurred around 10 billion years ago and marks a time when star formation and supermassive black hole growth was at its strongest.

The Hidden World of Cosmic Noon

But there’s a catch: around Cosmic Noon, galaxies were heavily shrouded in thick gas and dust. This obscuring material makes it difficult for us to observe these systems in short wavelengths like optical and X-ray. Instead, we have to get creative by searching for our targets at other wavelengths.

Since AGN emission is absorbed by the surrounding dust and re-radiated in infrared, we can use infrared brightness to find obscured but luminous sources. To differentiate between hidden clumps of star formation and hidden AGN, we also look for a compact radio source — a signature that points to a jet emitted from a central black hole.

A team of scientists led by Pallavi Patil (University of Virginia and the National Radio Astronomy Observatory) has now gone on the hunt for these hidden sources at Cosmic Noon.

Newly-Triggered Jets Caught in the Act

Patil and collaborators observed a sample of 155 infrared-selected sources, following up with high-resolution imaging from the Jansky Very Large Array to identify compact radio sources.

NRAO/Karl V Jansky Expanded Very Large Array, on the Plains of San Agustin fifty miles west of Socorro, NM, USA, at an elevation of 6970 ft (2124 m)

From their observations and modeling of the jets, the authors estimate these sources’ properties.

The authors find bright luminosities, small sizes, and high jet pressures — all of which suggest that we’ve caught newly-triggered jets in a short-lived, unique phase of AGN evolution where the jets are still embedded in the dense gas reservoirs of their hosts. The jets are expanding slowly because they have to work hard to push through the thick clouds of surrounding material. Over time, the jets will likely expand to larger scales and clear out the surrounding matter, causing the sources to evolve into more classical looking radio galaxies.

What’s next? The authors are currently working on a companion study to further explore the shapes of the jets and their immediate environments. These young, hidden sources will provide valuable insight into how supermassive black holes evolve alongside their host galaxies.


“High-resolution VLA Imaging of Obscured Quasars: Young Radio Jets Caught in a Dense ISM,” Pallavi Patil et al 2020 ApJ 896 18.

See the full article here .


Please help promote STEM in your local schools.

Stem Education Coalition


AAS Mission and Vision Statement

The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

Adopted June 7, 2009