Analyzing data from the Dark Energy Camera Legacy Survey (DECaLS), astronomers at Christ University in Bangalore, India, accidentally discovered a new ring-shaped galaxy, named DES J024008.08-551047.5, which may belong to a rare class of galaxies of polar rings. . The so-called polar ring galaxies (PRG) are systems formed by a galaxy similar to S0 and a polar ring that have remained separated for billions of years. In general, these outer polar rings, composed of gas and stars, are oriented approximately perpendicular to the long axis of the central parent galaxy.

However, although more than 400 PRG candidates have been discovered to date, only a dozen of them have been confirmed as true polar ring galaxies by additional spectroscopic observations. Now, a team of astronomers led by Akhil Krishna has discovered another candidate for PRG. The discovery of DES J024008.08-551047.5 (or DJ0240) was made during visual observations using optical imaging data from DECaLS. “We discovered the galaxy DJ0240 as a potential PRG candidate with a ring component located almost perpendicular to the host galaxy,” the researchers wrote in the paper.

The study found that DJ0240 has a ring nearly perpendicular to its parent galaxy. The tilt angle of the ring is approximately 80 degrees and the tilt angle of the host is approximately 10 degrees, indicating that these two components are almost orthogonal to each other. The distance to the galaxy is estimated to be approximately 1.8 billion light years. After analyzing the image, the team discovered that the ring is three times more elongated than the parent galaxy, which consists of a bulge and a disk. Furthermore, the ring was found to be bluer than the parent galaxy, which is commonly seen in other known PRGs. The authors of the paper explained that the presence of bluer ring components in the PRG indicates a higher level of star formation activity in these structures. The researchers found that DJ0240’s ring has a relatively small Sersic index, further supporting the classification of this galaxy as a PRG. They added that the measured effective radii of the galaxy components are comparable to those of other PRGs.

Summarizing the results, the astronomers concluded that DJ0240 is most likely a PRG, ruling out the possibility that the host galaxy is lenticular. However, more research is needed to reach definitive conclusions.

source: https://arxiv.org/abs/2308.15534