Researchers from Johns Hopkins have discovered that massive black holes are keeping new stars from forming in aging galaxies.
Tobias Marriage, a physics and astronomy assistant professor, and Megan Gralla, a post-doctoral fellow, both from Johns Hopkins, led a study that showed how particles spewed out by the black holes were preventing hot free gas from essentially cooling and collapsing as they pass. Because hot gas cannot cool and collapse, new stars cannot be formed.
The study was carried out by adapting the Sunyaev-Zel'dovich (SZ) effect signature, a well-known research method for studying large clusters of galaxies characterized by interactions between hot gas high-energy electrons and faint light with cosmic microwave backgrounds.
Although the method was primarily geared toward exploring larger galaxy clusters, Gralla saw that it can also be utilized for learning about smaller formations.
"What we're doing is asking a different question than what has been previously asked. We're using a technique that's been around for some time and that researchers have been very successful with, and we're using it to answer a totally different question in a totally different subfield of astronomy," explained Gralla.
Eiichiro Komatsu, director of the Max Planck Institute for Astrophysics, said he was stunned by the study because it never occurred to him that spotting the SZ effect in active galactic nuclei was even possible. He adds that research involving the SZ effect has now begun a new era.
Stars are formed when hot gas is drawn, cooled, and condensed. The gas sometimes finds its way back into black holes, which then grow alongside the population of stars. The process never stops but it has been observed that gas in mature galaxies no longer cools down, meaning new stars are no longer formed.
Marriage, Gralla, and colleagues found that mature galaxies radiating radio frequencies all have hot gas and all the right ingredients to give birth to new stars. This supports their hypothesis then that the radio frequencies are acting as "off switches" for the star-making process in mature galaxies. However, it is still not certain why black holes found in mature galaxies start to emit radio frequencies in the first place.
Published in the Monthly Notices of the Royal Astronomical Society, the study also lists Wenli Mo and David Crichton as co-lead authors. Data was sourced from Chile's Atacama Cosmology Telescope, the Very Large Array and the Green Bank Telescope from the National Radio Astronomy Observatory and the Herschel Space Observatory.
