Using archival and new data from the Atacama Large Millimeter/submillimeter Array (ALMA), astronomers have imaged 3C 273, a radio-loud quasar located some 2.4 billion light-years away in the constellation of Virgo.
“A quasar is the nucleus of a galaxy believed to host a massive black hole at its center, which swallows its surrounding material, giving off enormous radiation,” said Kogakuin University astronomer Shinya Komugi and colleagues.
“Contrary to its bland name, 3C 273 is the first quasar ever discovered, the brightest, and the best studied.”
“It is one of the most frequently observed sources with telescopes because it can be used as a standard of position in the sky. In other words, 3C 273 is a radio lighthouse.”
3C 273 has been known for decades as the most famous quasar, but knowledge has been concentrated on its bright central nuclei, where most radio waves come from.
However, much less has been known about its host galaxy itself because the combination of the faint and diffuse galaxy with the 3C 273 nucleus required such high dynamic ranges to detect.
Dr. Komugi and co-authors used a technique called self-calibration to reduce the leakage of radio waves from 3C 273 to the galaxy, which used the quasar itself to correct for the effects of Earth’s atmospheric fluctuations on the telescope system.
They reached an imaging dynamic range of 85,000, an ALMA record for extragalactic objects.
As a result of achieving high imaging dynamic range, they discovered the faint radio emission extending for tens of thousands of light-years over the host galaxy of 3C 273.
“Radio emission around quasars typically suggests synchrotron emission, which comes from highly energetic events like bursts of star formation or ultrafast jets emanating from the central nucleus. A synchrotron jet exists in 3C 273 as well,” the researchers explained.
They found that this faint and extended radio emission came from hydrogen gas in the galaxy energized directly by the nucleus.
This is the first time that radio waves from such a mechanism are found to extend for tens of thousands of light-years in the host galaxy of a quasar.
“This discovery provides a new avenue to studying problems previously tackled using observations by optical light,” Dr. Komugi said.
“By applying the same technique to other quasars, we expect to understand how a galaxy evolves through its interaction with the central nucleus.”
A paper on the findings was published in the Astrophysical Journal.
Shinya Komugi et al. 2022. Detection of Extended Millimeter Emission in the Host Galaxy of 3C 273 and Its Implications for QSO Feedback via High Dynamic Range ALMA Imaging. ApJ 930, 3; doi: 10.3847/1538-4357/ac616e
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