Markarian 231 Galaxy is a galaxy located approximately 581 million light-years away in the direction of the Virgo constellation, and it possesses an active galactic nucleus (AGN). This celestial object is a critical target in astrophysical research due to its classification as both one of the nearest quasar-like objects and an ultraluminous infrared galaxy (ULIRG). The galaxy is named after astronomer Benjamin Markarian, who cataloged active galactic nuclei in the 1960s.
Markarian 231 Galaxy (NASA)
General Characteristics
Markarian 231 (Mrk 231, UGC 8058) is a galaxy located in the direction of the Virgo constellation, approximately 581 million light-years (about 178 megaparsecs) away. This celestial object was formed as a result of the merger of two galaxies and structurally exhibits the characteristics of an elliptical galaxy with an active nucleus. With a redshift value of z = 0.04217, Markarian 231 has an apparent magnitude of about 13.85 in the V-band.
This galaxy is rich in interstellar dust and is also classified as a weak radio source. From an observational standpoint, it is one of the rare examples that draws attention in both optical and infrared wavelengths due to its post-merger active galactic nucleus (AGN) structure.
Structure and Morphology
Markarian 231 likely formed from the merger of two gas-rich spiral galaxies. Observations show that the galaxy has an irregular outer structure and tail-like morphological extensions. This suggests that the galaxy is still dynamically undergoing a merger process and is experiencing significant star formation and gas inflow.
At the galaxy’s center lies a supermassive black hole (SMBH), and due to the intense matter inflow around this black hole, the galaxy exhibits characteristics of an active galactic nucleus. Multi-wavelength observations in optical, X-ray, radio, and infrared wavelengths have revealed that high-energy processes are ongoing in the nucleus.
Quasar Characteristics and ULIRG Classification
Mrk 231 is one of the nearest quasar-like galaxies with a low redshift value. Its quasar characteristics arise from the intense electromagnetic radiation emitted due to the large amount of matter flowing toward the supermassive black hole at the galaxy’s core.
The spectrum of Markarian 231 contains broad emission lines, indicating that the ionized gas clouds are moving at high velocities. This reveals that strong radiation pressure is active around the core, consistent with the classical quasar model.
Markarian 231 has been classified as a ULIRG (Ultraluminous Infrared Galaxy) due to its high brightness in the infrared wavelengths. According to data from the IRAS (Infrared Astronomical Satellite), the galaxy’s total infrared luminosity exceeds 10¹² solar luminosities. This indicates intense ongoing star formation (starburst) within the galaxy. However, it is also believed that a large portion of the infrared radiation is due to emission absorbed and re-emitted by dust surrounding the active core.
Supermassive Black Hole and AGN Winds
Based on spectral analyses and gas dynamics studies, the mass of the black hole at the galaxy’s center is estimated to be around 1.5 × 10⁸ solar masses. The accretion disk surrounding the black hole is a powerful source of X-ray and ultraviolet radiation. Additionally, AGN winds and high-velocity matter outflows have been observed in various wavelengths.
Extremely strong AGN winds have been observed in the core of Markarian 231. These winds are formed when some of the matter falling into the black hole is ejected at high velocities. Observations show that these winds can reach speeds of about 10,000 km/s. Such high-energy outflows can suppress star formation within the galaxy and expel gas out of the galaxy.
Therefore, Markarian 231 serves as an important laboratory for studying matter cycling in galaxies, star formation feedback, and black hole-galaxy interactions.
Binary Nucleus Claims and Spectral Features
Observations made in 2015 presented evidence suggesting the presence of a possible binary supermassive black hole system at the core of Markarian 231. X-ray and polarimetry analyses showed unusually weak X-ray emissions in the galaxy’s core. This has been interpreted as either a smaller black hole being in the process of being consumed by a larger one, or the system being in a dynamic interaction. Such binary black hole systems are theoretically significant for understanding post-merger evolutionary processes and gravitational wave sources.
The spectrum of Markarian 231 includes both broad and narrow emission lines. Among these lines are classical AGN spectral lines such as Hα, Hβ, [O III], and [N II]. A high abundance of molecular gas (CO, HCN) has also been detected in the galaxy. This molecular gas has been observed using radio telescopes like ALMA and IRAM, enabling the monitoring of intense star formation and gas flows.
With its quasar-like structure, high infrared luminosity, strong AGN winds, and possible binary nucleus, Markarian 231 is a significant example among active galaxies. It is considered a model system for observational studies of astrophysical processes such as black hole feeding, star formation feedback, galaxy mergers, and evolution. The data obtained through multi-wavelength observations contribute to testing current theories regarding galaxy-AGN interaction.
