Sky survey reveals newborn jets in distant galaxies

Astronomers using data from the ongoing VLA Sky Survey (VLASS) have found a number of distant galaxies with supermassive black holes at their cores that have launched powerful jets of radio-emitting matter over the past two decades. The scientists compared the data from VLASS with data from an earlier survey that also used the National Science Foundation’s very large Karl G. Jansky (VLA) table to reach their conclusion.

“We have found galaxies that had no trace of jets before, but now show clear indications of young and compact jets,” said Dr. Kristina Nyland, NRC postdoctoral fellow in residence at the Naval Research Laboratory.

“Jets like these can strongly affect the growth and evolution of their galaxies, but we still don’t understand all the details. Catching newborn jets with polls like VLASS provides a measure of the role of powerful jets. radio in shaping the life of galaxies over billions of years, ”said Nyland.

VLASS is a project that will study the sky visible from the VLA – about 80% of the entire sky – three times in seven years. Observations began in 2017 and the first of three analyzes is now complete. Nyland and his colleagues compared the data from this analysis with data from the FIRST survey which used the VLA to observe a smaller portion of the sky between 1993 and 2011.

They found approximately 2,000 objects that appear in the VLASS images, but were not detected in the previous FIRST investigation. From these, they selected 26 objects that were previously classified as galaxies with active nuclei – fed by supermassive black holes – by optical and infrared observations. The FIRST observations of the 26 objects were made between 1994 and 2001. The VLASS observations were made in 2019. The intervals between the observations of the objects therefore varied from 18 to 25 years.

They chose 14 of these galaxies for more detailed observations with the VLA. These observations provided higher resolution images and were also performed at multiple radio frequencies to gain a more complete understanding of the characteristics of the objects.

“The data from these detailed observations tell us that the most likely cause of the difference in radio brightness between the FIRST and VLASS observations is that the ‘engines’ at the heart of these galaxies have launched new jets since the EARLY observations,” a explained Dillon Dong, of Caltech.

Black holes in the heart of galaxies are known to interact with galaxies themselves, and the two evolve together. Jets launched from regions near black holes can affect the amount of star formation in the galaxy.

“Radio jets provide natural laboratories for learning the extreme physics of supermassive black holes, the formation and growth of which are believed to be intrinsically linked to that of the galactic centers in which they reside,” said Pallavi Patil, of the University of Virginia.

“Jets as young as those discovered in our study may provide us with a rare opportunity to gain new knowledge about how these interactions between jets and their environment work,” said Nyland.

“VLASS has proven to be a key tool in discovering such jets, and we look forward to the results of its next two epochs of observation,” said Mark Lacy, of the National Radio Astronomical Observatory.

Nyland and his colleagues are planning further galaxy studies using the Very Long Baseline Array (VLBA), the Chandra X-Ray Observatory, and visible and infrared light telescopes. The article has been accepted for publication by The astrophysical journal.