All posts tagged: star clusters

Dark matter and star clusters work together to reshape the centers of galaxies

Dark matter and star clusters work together to reshape the centers of galaxies

Published by Jenni Sidey

A galaxy simulation shows that nuclear star clusters and nuclear stellar disks can grow together as a stellar bar funnels gas toward the galactic center. Repeated shocks from stellar feedback move gas inward and trigger new star formation, while the surrounding nuclear disk gradually expands from the inside out. The connection can become difficult to recognize as the two structures evolve at different rates, and mergers with massive star clusters can further reshape the galactic center. At the heart of a barred galaxy, two stellar structures can grow around the same central region. One is compact and pressure-supported. The other spreads outward as a rotating disk. Their apparent disconnect has obscured a shared origin. A simulation from the SMUGGLE-Ring project shows how both structures can emerge together in a Milky Way-mass galaxy. It examines nuclear star clusters, or NSCs, and nuclear stellar disks, or NSDs. Observational surveys have found no clear correlation between their masses and sizes, reinforcing the idea that they form separately. The work follows their development over four billion years. A stellar …

The biggest black holes grow by crashing into each other over and over again

The biggest black holes grow by crashing into each other over and over again

Published by Jenni Sidey

Some of the biggest black holes ever picked up through gravitational waves may not have formed in a single stellar collapse at all. Instead, they seem to be the battered products of repeated smashups inside some of the most crowded stellar environments in the universe. That is the picture emerging from a new analysis led by Cardiff University, which examined 153 confident black hole merger detections from version 4.0 of the LIGO-Virgo-KAGRA gravitational-wave catalog. The team found that the heaviest black holes in the sample do not behave like an extension of the lighter ones. They look like a separate population. “Gravitational-wave astronomy is now doing more than counting black hole mergers,” said lead author Dr. Fabio Antonini of Cardiff University’s School of Physics and Astronomy. “It is starting to reveal how black holes grow, where they grow, and what that tells us about the lives and deaths of massive stars. This is exciting because we can use the information to test our understanding of how stars and clusters evolve in the Universe.” The dividing …

Hubble and JWST reveal thousands of young star clusters emerging from their birth clouds

Hubble and JWST reveal thousands of young star clusters emerging from their birth clouds

Published by Jenni Sidey

A young star cluster does not begin life in the open. It starts buried inside thick clouds of gas and dust, hidden from ordinary view while newborn stars heat, ionize, and push against the material around them. Now, observations from the Hubble and James Webb space telescopes suggest that the biggest clusters do not stay hidden for long. In four nearby galaxies, astronomers found that more massive young star clusters clear away their birth clouds faster than smaller ones do. That means the brightest, most energetic clusters can begin flooding their host galaxies with radiation sooner, with consequences that reach from galaxy evolution to planet formation. “I was excited to see that the emerging timescale of a star cluster is related to its mass in stars. This has implications on a range of research fields, from planet formation to galaxy evolution”, said Alex Pedrini, a PhD student at Stockholm University’s Department of Astronomy and the first and corresponding author of the study. The work, published in Nature Astronomy, draws on a large census of roughly …

Astronomers spot a hot galaxy cluster that defies existing cosmic theory

Astronomers spot a hot galaxy cluster that defies existing cosmic theory

Published by Jenni Sidey

Researchers at the University of British Columbia and Dalhousie University have found a young galaxy cluster that appears far hotter than theory allows. The international team, working with the National Research Council of Canada and using the Atacama Large Millimeter/submillimeter Array, reported the discovery in the journal Nature. The study was led by Dazhi Zhou, a doctoral student in the UBC department of physics and astronomy. The work also involved Dr. Scott Chapman, a professor at Dalhousie University and an affiliate professor at UBC, who carried out much of the research while at the National Research Council of Canada. The scientists focused on a distant system called SPT2349–56. It existed just 1.4 billion years after the Big Bang, when most galaxy clusters were still forming. Yet this object already holds an atmosphere of hot gas more extreme than many clusters in the modern universe. RGB image of the protocluster SPT2349–56 with tSZ decrement contours. (CREDIT: Nature) “We did not expect to see such a hot cluster atmosphere so early in cosmic history,” Zhou said. “In …