Black hole growth fuelled by counter-rotating gas

Project Information

CR-GAS

Grant agreement ID: 891744

DOI

10.3030/891744

Project closed

EC signature date 3 April 2020

Start date 1 October 2020

End date 30 September 2023

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 268 921,92

EU contribution

€ 268 921,92

Coordinated by

KOBENHAVNS UNIVERSITET
Denmark

Periodic Reporting for period 2 - CR-GAS (Black hole growth fuelled by counter-rotating gas)

Reporting period: 2022-10-01 to 2023-09-30

Summary of the context and overall objectives of the project

The project is focused on the physics of supermassive black hole growth. It addresses the problem of how supermassive black holes acquire the gas needed for them to grow in mass and power their activity. This is one of the most important problems in Astrophysics as it connects the co-evolution of galaxies and supermassive black holes across the age of the Universe.

The objectives of the project are to use structures that rotate in opposite directions within galaxies (counter-rotating or misaligned structures) to determine how gas is transported to the supermassive black hole. Counter-rotation is an unambiguous dynamical tracer that will be used in the project to map the distribution and velocity of the gas across the galaxy as it travels towards the black hole.

The three main objectives are:
• Determine if counter-rotating structures promote the flow of gas towards the black hole
• Determine the physical mechanisms that transport the gas
• Determine if galaxy interactions are the main mechanism to provide gas to the black holes in a specific type of galaxies: early-types/S0s.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

1) The following work tasks have been completed during the project:

• Analysis of the mechanisms for gas transport in an early-type galaxy/S0. Using high-quality data on a galaxy with counter-rotating structures, we have determined the distribution of gas and its dynamical properties as it flows to the black hole. Our analysis was the first observational evidence for a predicted theoretical scenario of gas inflow after a galaxy interaction. We determined the physical mechanism that transported the gas and discussed its relevance in the context of all galaxies that undergo the same events. The results of this work were published in Raimundo 2021, ‘External gas accretion provides a fresh gas supply to the active S0 galaxy NGC 5077’ Astronomy & Astrophysics, 650, 34.

• Analysis of a large sample of 3068 galaxies to investigate if counter-rotating structures or large misalignments promote the flow of gas towards the black hole. This detailed analysis has been completed by analysing the distribution, dynamics and excitation conditions of the entire sample of galaxies, divided according to the level of black hole activity and galaxy type. We discovered that misaligned structures (of which counter-rotating structures are a subset) and the associated galaxy interactions promote the flow of gas towards the black hole and black hole activity. The results of this work we published in Raimundo, Malkan & Vestergaard, 2023, ‘An increase in black hole activity in galaxies with kinematically misaligned gas’, Nature Astronomy, 7, 463.

• Analysis of the misalignment structures and black hole activity of a sample of 10 000 galaxies from the MaNGA survey. This much larger sample validates the results found in Raimundo, Malkan & Vestergaard (2023) for a much larger sample and even when a different selection is used to identify active black holes.

• Planned and obtained new observations using international facilities, namely with OSIRIS, an instrument on the W. M. Keck Observatory, and NIFS, an instrument on the Gemini Observatory.

2) The results were disseminated to the research community during 11 seminars at international institutes and conferences.

3) The results were disseminated to the public via 20 outreach events to students (from 8 - 17 years-old) and to the public in general. Additionally, the results were disseminated via two press releases and interviews with the media.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

During this project we have achieved major progress beyond the state of the art, in particular by 1) obtaining the first observational/experimental evidence for a theoretical prediction of gas flow after galaxy interactions and 2) for determining for the first time that misaligned structures and associated galaxy interactions promote black hole activity. We have characterised the mechanism of gas transport from the inter-galactic environment towards the supermassive black hole in galaxies with past interactions, and identified that this mechanism is likely more important for early type galaxies (ellipticals and S0s) than spirals. We have also predicted that this mechanism is more important for more distant galaxies (higher redshift) where galaxy interactions are expected to be more common.

Our findings will have impact on the study of black hole growth and activation, as it shows the first direct correlation between galaxy interactions/gas misalignment and supermassive black hole activity. Possible future investigations will use these findings to address the importance of galaxy interactions and mergers for black hole growth, in particular at the earlier age of the Universe.

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