SANTA CRUZ DE TENERIFE, Feb. 18 (EUROPA PRESS) –
The researcher at the Institute of Astrophysics of the Canary Islands (IAC) Cristina Ramos Almeida is leading a study that has used data from the ALMA telescope in Chile to understand how supermassive black holes affect the galaxies that host them, the results of which are being published today in the journal ‘Astronomy & Astrophysics’.
Supermassive black holes, which are found in the center of galaxies, play a fundamental role in regulating their growth, but it is not yet known exactly how this happens or under what circumstances. What is known is that it occurs during a phase in which the black hole is consuming material from the galaxy where it resides at a very high rate, becoming increasingly heavier. During this phase, the galaxy is said to contain an active nucleus (or AGN).
These periods of nuclear activity can be recurrent as long as gas is available to fuel the black hole. And one of its effects are the winds: gas from the center of the galaxy that is pushed out by the energy released by the active nucleus or other related phenomena. These winds can reach speeds of up to thousands of km/s for low-density gas, and up to hundreds of km/s for denser gas. In the case of the most energetic AGN, such as some quasars, they could ’empty’ the center of galaxies of gas, thus preventing the formation of new stars.
To study the winds of dense and cold gas (at temperatures below -170º C) it is necessary to use telescopes such as the Atacama Large Millimeter/submillimeter Array (ALMA), which allow the study of millimeter or submillimeter radiation, which has frequencies between infrared and radio waves. ALMA is an interferometer made up of 66 high-precision mobile antennas, which can be spaced up to 16 kilometers apart. This allows galaxies to be studied with an unprecedented level of detail in this range.
Making use of data from active galaxies obtained with ALMA, an article prepared by an international team, led by the IAC researcher Cristina Ramos Almeida, is published today in the journal ‘Astronomy & Astrophysics’. In it they analyze the data of a sample of seven very energetic quasars found in the Local Universe. This work is part of the ‘QSOFEED’ project, whose objective is to understand how supermassive black holes affect the galaxies that host them.
“ALMA has allowed us to study the cold molecular gas winds of these quasars through the emission of a carbon monoxide molecule,” explains Ramos Almeida. “This analysis is important because this cold and dense gas is the material from which new stars are formed and, to date, there was no data of this quality and resolution for a set of obscured quasars in the Local Universe”, he adds.
This type of quasar is relevant because it can constitute an important phase for the evolution of galaxies in which the active nucleus is evacuating and consuming gas at a very high rate and which would give way to a non-obscured phase. Studying these nearby objects is key to understanding what was happening to these galaxies when the universe was only a quarter of its current age.
Based on the new data obtained with ALMA, the team has found that molecular winds are mostly coplanar with the disk where most of the molecular gas is distributed, relatively compact and slow, reaching maximum speeds of only 200-350 km/h. yes However, these winds, together with the action of jets or radio jets in some cases, would be responsible for modifying the content and distribution of molecular gas in the central region of galaxies (the central kiloparsec, which corresponds to about 3,300 light years).
“Although the total molecular gas content of the host galaxies is not significantly modified, the innermost regions are altered by the action of these winds”, says Anelise Audibert, IAC researcher and co-author of the work.
The next step is to observe a larger sample of obscured quasars with the MEGARA instrument, installed on the Gran Telescopio CANARIAS (GTC), and with ALMA, to characterize their ionized and molecular winds. “We also want to investigate the stellar populations of the host galaxies, with the aim of seeing if the most extreme winds are the ones that are most significantly affecting the formation of new stars. This would allow us to directly quantify the effect of the AGN feedback. “, concludes Patricia Bessiere, a researcher at the IAC and another of the authors of the article, whose research focuses on this aspect of the project.
