Supermassive black holes detected for the first time in low-mass galaxies at intermediate stages of the Universe

• Black holes are more massive than expected given the mass of their host galaxies
• The finding connects the local universe with the early universe, since the supermassive black holes found in this intermediate scenario are similar to those of the early universe
• Mar Mezcua, IEEC researcher at the Institute of Space Sciences, leads this study published in The Astrophysical Journal Letters

A team of astronomers has found supermassive black holes at a key epoch in the history of the Universe called ‘Cosmic Noon’, about 10 billion years ago, in which star formation and black hole activity reached their peak. The study, led by Mar Mezcua, researcher from the Institute of Space Studies of Catalonia (IEEC) at the Institute of Space Sciences (ICE-CSIC), has been published in The Astrophysical Journal Letters.

The study reports the finding of active galactic nuclei (AGN)—that is, black holes which are actively accreting—in low-mass galaxies about 10 billion years ago. The main characteristic of these AGN is that they are more massive than expected for the mass of their host galaxies. Being low-mass galaxies, the mass of their black holes are expected to be less than a million times that of the Sun. However, the mass found corresponds to that of supermassive black holes (more than a million times the mass of the Sun), typically hosted in massive galaxies and not in dwarf galaxies.

This finding links for the first time those AGN found in low-mass galaxies at the early Universe by the James Webb Space Telescope with those found in the local Universe. Surprisingly, the properties of the sources both at the early Universe and Cosmic Noon are found to be the same in terms of black hole properties, such as mass, luminosity or accretion rate, suggesting that these are the same type of sources but at different cosmic epochs.

“The supermassive black holes found in low-mass galaxies are thought to have originated from seed black holes in the early Universe. Hence finding a connection between the local and early Universe can provide a step forward in understanding how these seed black holes formed and evolved,” says Mar Mezcua, IEEC researcher at the ICE-CSIC and first author of the paper.

The origin of the first supermassive black holes

Supermassive black holes form from early Universe seed black holes, or also called intermediate-mass black holes, which have a mass between one hundred and a million solar masses. The remains of the seed black holes that did not become supermassive can be found in low-mass galaxies in the local Universe.

The low-mass galaxies detected in the study host supermassive black holes—not intermediate-mass ones—and are similar to the supermassive black holes found at the early stages of the Universe by the James Webb Space Telescope. This provides the scientific community with a great opportunity for linking the local and the early Universe and thus to better understand the formation and evolution of the seed black holes.

“Supermassive black holes reside at the centre of most massive galaxies such as the Milky Way and play a key role in galaxy evolution, hence understanding how they form and evolve is very important,” adds Mar Mezcua.

The data used come from public spectroscopic surveys, such as the Sloan Digital Sky Survey (SDSS) located at the Apache Point Observatory in New Mexico (United States), the VIMOS Public Extragalactic Redshift Survey (VIPERS) from the European Southern Observatory (ESO), as well as published data from the James Webb Space Telescope.

“The origins and the mechanisms behind the growth of supermassive black holes remain enigmatic. With cutting-edge telescopes pushing the limits of AGN observational capability we are on the cusp of obtaining more comprehensive insights into black holes and cosmic history. Thanks to synergistic studies of the samples provided by the James Webb Telescope and ground-based telescopes, like VIPERS, we can not only investigate these cosmic phenomena but also shed light on the evolution of galaxies and the formation of our Universe as we know it today,” says Malgorzata Siudek, postdoctoral researcher at ICE-CSIC.

The team will further investigate the properties of the low-mass galaxies and their black holes at cosmic noon onwards, with the aim of looking for the presence of black hole winds, as well as signatures of galaxy mergers that could shed light on why the black holes are more massive than expected.

More information

This research is presented in a paper entitled “Overmassive Black Holes at Cosmic Noon: Linking the Local and the High-redshift Universe”, by Mezcua, M. et al., which appeared in the journal The Astrophysical Journal Letters on 6 May 2024. DOI: 10.3847/2041-8213/ad3c2a

Links

•  IEEC
•  ICE-CSIC
• James Webb Space Telescope

Contacts

About the IEEC

The Institute of Space Studies of Catalonia (IEEC — Institut d’Estudis Espacials de Catalunya) promotes and coordinates space research and technology development in Catalonia for the benefit of society. IEEC fosters collaborations both locally and worldwide and is an efficient agent of knowledge, innovation and technology transfer. As a result of more than 25 years of high-quality research, done in collaboration with major international organisations, IEEC ranks among the best international research centres, focusing on areas such as: astrophysics, cosmology, planetary science, and Earth Observation. IEEC’s engineering division develops instrumentation for ground- and space-based projects, and has extensive experience in working with private or public organisations from the aerospace and other innovation sectors.

The IEEC is a non-profit public sector foundation that was established in February 1996. It has a Board of Trustees composed of the Generalitat de Catalunya, Universitat de Barcelona (UB), Universitat Autònoma de Barcelona (UAB), Universitat Politècnica de Catalunya · BarcelonaTech (UPC), and the Spanish Research Council (CSIC). The IEEC is also a CERCA centre.