📰 A supermassive black hole expelled from its galaxy

When two galaxies merge, the supermassive black holes that hide in their cores quickly merge. Their relative orbital energy will be radiated by gravitational waves. If this last emission is strongly anisotropic, it will produce a recoil of the black hole (In astrophysics, a black hole is a massive object whose gravitational field is so intense…) resulting from the merger (In physics and metallurgy, fusion is the transition of a body from a solid state to a …) who will be expelled. The event is difficult to detect and only candidates have been observed.

In recent work, an international team including researchers from theParis Observatory (The Paris Observatory was born from the project, in 1667, to create an astronomical observatory…) – PSL, detected the gas (A gas is a set of atoms or molecules very weakly bound and…) molecular galaxy (Galaxies is a quarterly French magazine devoted to science fiction. With…) remnant of candidate 3C186, which confirms that the black hole (The Black Hole is a science fiction film directed by Gary Nelson,…) massive (The word massive can be used as:) was ejected from his galaxy (A galaxy is, in cosmology, an assembly of stars, gas, dust and…) at 2000km/s, and at a projected distance of 24,000 years light (Light is the set of electromagnetic waves visible to the eye…).

Galaxy mergers are fundamental mechanisms regulating the growth of galaxies and the evolution of supermassive black holes (SMBH) at their centers. When the SMBH merges, a fraction of theenergy (In common sense, energy designates everything that allows you to do work, make energy, etc.) binding of the SMBH is converted into gravitational waves (GW). In case of’anisotropy (Anisotropy (opposite of isotropy) is the property of being direction dependent….) from this GW emission, the SMBH resulting from the fusion can receive a recoil pulse. Measurable displacements of SMBHs relative to the center of their host galaxy have been theoretically predicted, resulting from GW recoils. However, so far there has been no unambiguous detection of such displacements. Such a detection would have a huge impact on our understanding of the evolution of galaxies and structures at large scale (The large ladder, also called aerial ladder or auto ladder, is a…).

In order to meet this challenge, an international team of researchers studied 3C 186, a powerful extra-galactic radio source, at a distance of 8 billion light years from the earth (Earth is the third planet in the Solar System in order of distance…), which has emerged as a plausible GW rollback candidate. The team studied molecular gas in the galaxy 3C 186, using the Northern Extended Millimeter Array (NOEMA) at Plateau de Bure in the French Alps.

In Astronomy and Astrophysics Letter which has just been published, they report new observations (Observation is the action of attentive follow-up of phenomena, without the will to see them…) from 3C 186 to lengths ofwave (A wave is the propagation of a disturbance producing a variation in its path…) millimeters, at unprecedented resolution and sensitivity. They were able to detect the galaxy’s CO emission, and discover a disk (The word disc is used, both in geometry and in everyday life, to designate a…) 8×10 molecular¹⁰ Msun, turning around (Autour is the name that the avian nomenclature in the French language (update) gives…) from the center of the galaxy. This record is clearly off by 8kpc in projection (Cartographic projection is a set of techniques for representing the surface of…) of the radio source/quasar, revealed by the regions of very high speeds around the massive black hole (see illustration). Moreover, the CO line reveals that the speed (We distinguish 🙂 of the galaxy and quasar (A « quasi-stellar radiation source » (quasar), (quasi-stellar radio…) are shifted by 2000 km/s, along the line of sight. The study thus reports the first confirmation of a GW retreat via high-resolution millimetric observations. These interferometric observations were indeed vital (The Vitales are an order of dicotyledonous plants. This order has been reintroduced…) to test the GW recoil scenario, as they probe both the molecular gas reservoir which is the fuel (A fuel is a fuel that powers a heat engine. This transforms…) of star formation in the host galaxy as well as the continuous emission associated with the radio source, which is ultimately powered by theaccretion (Accretion designates in astrophysics, geology and meteorology the increase by…) on the SMBH.

the shift (In geometry, a displacement is a similarity that preserves distances and angles…) observed is in remarkable agreement with theoretical predictions of GW recoil pulses. This is interpreted by the team as the result of strong gravitational wave recoil when two SMBHs merged after their host galaxies merged. It would be the most energetic event ever observed: a major SMBH merger of mass (The term mass is used to designate two quantities attached to one…) comparable.

This work opens new perspectives for next-generation radio telescopes, such as the Square Kilometer Array (SKA) and the pulsar-timing array (PTA), a network (A computer network is a set of equipment linked together to exchange information…) giant of radio telescopes, overseer (A supervisor or educational adviser or educational assistant, is a…) hundreds of pulsars. They will be directly sensitive to GWs emitted by coalescing SMBHs of masses similar to those expected to be found in radio sources such as 3C 186.

Reference:
Castignani, G., Meyer, E., Chiaberge, M., Combes F. et al: 2022, NOEMA observations support a recoiling black hole in 3C186, Astronomy & Astrophysics Letters, 661, L2 www.aanda.org