It is known that the appearance and structure of galaxies – or their morphology – evolves over time. This field of studies still attracts a lot of attention from astrophysicists, who are trying to explain star formation mechanisms in different galactic regions.

The so-called star-formation rate (SFR) is one of the most important parameters acting as an indicator of stellar activity in different regions of any galaxy. A typical value of SFR varies in the range of 0-20 solar masses (equivalent) per year (where 20 represents the most massive galaxies), although significantly more luminous disk regions exist where new stars are being born tens of times more intensely. One of such regions has been recently observed in the barred spiral galaxy NGC 613 just before the main starburst event.

The observations of NGC 613 were performed using integral field spectrograph SINFONI on the Very Large Telescope. Data from Hubble Space Telescope was also incorporated into this research in order to get the highest spatial resolution view of the inner regions of NGC 613. An international team of scientists from Spain, Netherlands, Germany, France and Australia published results of the study at arXiv.org.

Seven distinct stellar clusters were identified inside NGC 613 forming a distinct ring-like morphological structure residing around the active galactic nucleus. The estimated star formation rates in the individual ring spots reach 0.1 M solar per year. This may seem as nothing special, but the authors note that, according to the results of spectral analysis, the nucleus of NGC 613 contains a substantial amount of hot hydrogen gas. In contrast to the observed ring-like structure, there is no evidence for active star formation in the nucleus; this, in turn, raises an interesting question – what exactly is the mechanism responsible for the hydrogen heating, and what is the likely fate of this gas?

The team suggests that currently observed dynamics of NGC 613 point to energetic outflow emanating from the nucleus. The authors also speculate that NGC 613 could be currently in a state right before imminent starburst episode, considering the lack of star formation in this region, the large amount of molecular gas and confirmed presence of nuclear activity. The next starbust could happen approximately in the next 0.5 million years – that’s pretty soon on an astronomical scale.