Chinese astronomers study NGC 7793's hot gaseous halo

Chinese astronomers have studied a nearby spiral galaxy called NGC 7793 using the Spektr-RG and Chandra space observatories. Their findings, released on March 13, shed light on the galaxy's hot gaseous halo. NGC 7793 is located about 12.2 million light years away and belongs to the Sculptor Group of galaxies. It has a diameter of roughly 30,000 light years and a stellar mass of around 3.2 billion solar masses, making it one of the brightest galaxies in that group. Despite being discovered over 200 years ago, the galactic X-ray emissions of NGC 7793 had not been thoroughly investigated, particularly regarding its halo gas. A research team led by Lin He from Nanjing University aimed to explore this area. They focused on the diffuse X-ray emissions from the galaxy using data from the Spektr-RG's eROSITA telescope and Chandra's Advanced CCD Imaging Spectrometer. The team found X-ray emissions beyond the galactic plane, indicating the presence of a hot gaseous halo. The researchers believe stellar feedback is crucial in forming and shaping this hot gas around low-mass spiral galaxies like NGC 7793. Their study revealed an unusual dip in the radial profiles of NGC 7793, which was more evident in higher energy bands. This dip might be linked to a bubble-like structure or variations in the intergroup medium, given its location in the Sculptor Group. The hot gas in NGC 7793 has a temperature of about 0.18 keV and an estimated mass of 10 million solar masses. The luminosity of this gas is approximately 130 undecillion erg/s, extending about 19,500 light years from the center of the galaxy. The findings suggest that ongoing star formation is vital for replenishing the hot gas. The researchers concluded that more studies are needed to further explore the hot circumgalactic medium of NGC 7793. They recommend using the Hot Universe Baryon Surveyor (HUBS) X-ray microcalorimeter for future research.