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Differences detected between disks with active and inactive galaxies

Spiral Galaxy

A study led by researchers at the Instituto de Astrofísica de Canarias (IAC), which compares the disks of several pairs of spiral galaxies, active and inactive, concludes that in the disks the movements of the previous rotors are of greater importance. This study, just approved for publication in Astronomy & Astrophysics Letters, is the first evidence of large dynamic differences between active and inactive galaxies in the local universe. The participating astronomers come from the Instituto de Astrofísica de Canarias (IAC) and the University of La Laguna (ULL); as well as NatiAstronomical First: Differences Detected Between Discs of Active and Non-active Galaxiesonal Autonomous University of Mexico (UNAM), Computense University of Madrid (UCM) and Instituto de Astrofísica de Andalucia (IAA).

There is now evidence that the supermassive black holes at the center of the majority of galaxies have a fundamental influence on their evolution. In some of them, black hole takes in the material that surrounds it at a very high speed and releases a large amount of energy. In these cases, we say that the galaxy has one active core (BAIT). The material that feeds AGN must initially be quite far from the core, on the galaxy̵

7;s disk, rotating around its center. This gas must somehow have “braked” to fall into the central zone, a process called loss of angular momentum.

Active coil compared to inactive twin

Image illustrating the comparison between an active spiral galaxy (orange box) and its inactive twin (blue box). Credit: Gabriel Pérez Díaz, SMM (IAC)

“Studying the mechanisms that control the relationship between the active nucleus and the rest of the galaxy -” explains Ignacio del Moral Castro, a doctoral student at the IAC and the University of La Laguna (ULL) and first author of the article – is necessary to understand how these objects form and evolving, and in order to shed light on this issue, we must compare active and inactive galaxies. To this end, the main idea of ​​my doctoral dissertation is centered on the study and comparison of galaxies that are almost twins, but with the difference is nuclear activity. “

The work has consisted of comparing the dynamics of the galactic disks of different active / inactive pairs. The researchers used data from Califa survey (Calar Alto Legacy Integral Field Area). This contains spectroscopic data on complete 2D fields for more than 600 galaxies, taken at the Calar Alto Observatory in Almería, which enables observations of virtually the entire galaxy, so that its global properties can be studied.

Roman method

Previously, in the majority of studies, the method used was the identification of a sample of active galaxies in a large study, which was then compared with the rest of the galaxies in the study with similar properties that do not show nuclear activity. But this time, the researchers used a new method: they made comparisons between one and one. First, they identified the active spiral galaxies in the CALIFA test, and for each of them they looked for an inactive galaxy that had equivalent global properties, ie with the same mass, brightness, orientation and so on and very similar appearance.

Using this method, the team presented two scenarios to explain the dynamic differences between active and inactive galaxies. First, the explanation would be that it is the trace of the angled speed transfer between the gas that has fallen into the center and the material that remains in the disc. The second attributes the difference to the incidence of gas from the outside, via the capture of small nearby satellite galaxies, in which case this capture should occur more frequently in the active galaxies. Both scenarios are compatible with this result and they are not mutually exclusive.

“The result surprised us; we really did not expect to find this type of difference on a large scale, given that the duration of the active phase is very short compared to the life of a galaxy and with the time required to produce morphological and dynamic changes, ”says Begoña García Lorenzo, and IAC researcher, and a co-author of the article.

“Until now, we thought that all galaxies go through active phases during their lifetime, but this result may mean that this is not the case, which would mean a major change in current models,” adds Cristina Ramos Almeida, also an IAC researcher and co-author of the article. .

Reference: “Major λR on the disk with isolated active spiral galaxies than in their inactive twins “ past I. del Moral-Castro, B. García-Lorenzo, C. Ramos Almeida, T. Ruiz-Lara, J. Falcón-Barroso, SF Sánchez, P. Sánchez-Blázquez, I. Márquez och J. Masegosa, 14 July 2020 , Astronomy & astrophysics Mail.
DOI: 10.1051 / 0004-6361 / 202038091
arXiv: 2006.12654

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