Fornax A galaxy studied with AstroSat

Using the AstroSat spacecraft, Indian astronomers performed an imaging and spectroscopy study of the Fornax A galaxy. The results of the study, published on January 13 on the arXiv preprint server, provide more clues about the properties of the galaxy and the ultraviolet emission of this source.

Located about 62 million light years away, Fornax A (also known as NGC 1316) is a lenticular galaxy in the constellation Fornax. Observations show that it harbors numerous tidal tails, seashells and unusual dust spots. In addition, it also exhibits characteristics of filament and nebular emission, ripples, arcs and several complex filament loops from other phases of the interstellar medium (ISM).

Fornax A is also a radio galaxy and at 1400 MHz is the fourth brightest radio source in the sky. Astronomers assume that this is the result of the merger of several smaller galaxies. Such fusion events may have fueled the central supermassive black hole, making Fornax A a radio-galaxy – type of active galactic nucleus (AGN) very bright at radio wavelengths. The properties of this galaxy make it one of the suitable candidates for recent mergers to study star formation and the interaction between AGN and ISM.

Therefore, a team of astronomers led by Nilkanth D. Vagshette from Maharashtra Udayagiri Mahavidyalaya College (MUM) in Udgir, India, performed observations at high resolution, in the near ultraviolet (NUV) and in the far ultraviolet (FUV) ) of this galaxy using AstroSat. Ultraviolet Imaging Telescope (UVIT), which consists of two carbon telescopes with diameters of 38 cm in the Ritchey-Chrétien configuration. The main objective of the observation campaign was to investigate the link between nuclear activity and star formation in the central region of the galaxy.

“We present imaging and photometric studies of the radio galaxy NGC 1316 (Fornax A) using high spatial resolution near-ultraviolet (NUV) and far-ultraviolet (FUV) imaging telescopes from India’s first multi-space space observatory. AstroSat wavelengths, ”the astronomers wrote in the paper.

AstroSat observations confirmed the existence of special features in the central (nuclear) region of Fornax A. Hidden structures like the rim, clusters and their strong spatial correspondence with imagery at other wavelengths indicate that the origin of gas and dust in this galaxy is due to past mergers.

The study found that the UV-emitting sources in Fornax A were displaced by radio jets emanating from the AGN explosion. This, according to the authors of the article, confirms that the exits caused by AGN are responsible for the deactivation of star formation in the galaxy.

“The most acceptable explanation is that the AGN outlets can remove the substantial amount of gas from the host galaxy, thereby blocking star formation,” the astronomers wrote.

The results also allowed the team to calculate the star formation rate (SFR) for Fornax A. Based on the estimated FUV and NUV luminosities, they found that the SFR is at a level of 0.15 and 0.36 solar mass per year. Scientists noted that these are lower limits due to the foreground filtering effect.

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