Fornax A galaxy explored with AstroSat

Using the AstroSat spacecraft, Indian astronomers conducted an image and spectroscopic study of the Fornax A galaxy. The results of the study, published on January 13 on the arXiv preprint server, provide more clues as to the characteristics of the galaxy and the ultraviolet emission of this source.

Fornax A (also known as NGC 1316), about 62 million light-years away, is a lenticular galaxy in the constellation Fornax. Observations show that it houses numerous tails, shells and unusual dust spots. In addition, it also exhibits filament, nebula emission characteristics, ripples, arcs, and various intricate filamentary loops of other phases of interstellar medium (ISM).

Fornax A is also a radio system and is at 1400 MHz the fourth brightest radio source in the air. Astronomers assume that this is due to the fusion of several smaller galaxies. Such fusion events possibly fueled the central supermassive black hole, causing Fornax A to become a radio system – a type of active galactic nucleus (AGN) that is very bright at radio wavelengths. The characteristics of this galaxy make it one of the suitable candidates of recent mergers to investigate star formation and interaction between the AGN and ISM.

Therefore, a team of astronomers led by Nilkanth D. Vagshette of the Maharashtra Udayagiri Mahavidyalaya (MUM) College in Udgir, India, made high-resolution, near-ultraviolet (NUV) and far-ultraviolet (FUV) observations of this galaxy AstroSat’s Ultraviolet Imaging Telescope (UVIT), which consists of two 38 cm diameter carbon telescopes in Ritchey-Chretien configuration. The main purpose of the observation campaign was to find the link between nuclear activity and star formation in the central region of the galaxy.

“We present image and photometric studies of the NGC 1316 radio system (Fornax A) using high-resolution near-ultraviolet (NUV) and far-ultraviolet (FUV) image telescopes of the first Indian wavelength of longer wavelength AstroSat,” he wrote. the astronomers in the paper.

AstroSat observations confirmed the existence of peculiar features in the central (core) region of Fornax A.. The hidden structures such as edges, clusters and their strong spatial correspondence with images at other wavelengths indicate that the origin of gas and dust in this galaxy is due to mergers in the past.

The study found that UV radiation sources in Fornax A are displaced by the radio rays emanating from the AGN eruption. This confirms, according to the authors of the newspaper, that the AGN-driven effluents are responsible for extinguishing the star formation in the galaxy.

“The most acceptable explanation is that the AGN effluent can remove the significant amount of gas from the host system and thus turn off star formation,” the astronomers wrote.

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

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