New extended and faint tidal tail discovered

By analyzing the data from the Dark Energy Camera Legacy Survey (DECaLS), astronomers have discovered a new tidal tail likely associated with the galaxy NGC 3785. The newly detected tidal tail is extremely extended and faint. The finding was reported in a research paper published October 24 on the preprint server arXiv.

Tidal tails are thin, elongated regions of stars and interstellar gas extending into space. They are formed as a result of gravitational interactions between galaxies and star clusters. The observations show that some interacting objects have two distinct tails, while other systems have only one tail.

Now, a team of astronomers led by Chandan Watts of the Indian Institute of Astrophysics (IIA) in Bengaluru, India, reports the detection of a new tidal tail. The new tail was serendipitously identified in DECaLS images, in an isolated environment associated with NGC 3785—a lenticular galaxy in the constellation Leo.

“We have discovered an exceptionally long and faint tail in an isolated environment, likely originating from galaxy interactions, particularly associated with NGC 3785,” the researchers wrote in the paper.

The tidal tail was spotted in the g-band image of NGC 3785. It appears that it has a projected length of approximately 1.27 million light years, which makes it the longest tidal tail observed in an isolated environment.

Further inspection of this tidal tail found that it is not uniformly straight but comprises both a linear segment and a looping section. Therefore, the astronomers assume that a satellite galaxy has undergone a tidal interaction with NGC 3785, starting from the northeast, making a loop, and then going towards the southwest by following the same trajectory.

Moreover, the study detected 84 star-forming clumps along the tail, mostly associated with the faint part of the tail. These clumps were found to be more prominent in the g-band, which suggests that they are blue in color. The collected data also indicate an imminent emergence of an ultra diffuse galaxy (UDG) at the end of the tail.

In addition, after thoroughly examining the images, the astronomers identified the quasar SDSS J113923.47+261630.5 situated behind the tidal tail, at a redshift of 1.04.

Summing up the results, the authors of the paper made concluding remarks regarding the origin of the discovered tidal tail.

“We propose that this tail arises from the interaction of NGC 3785 with a gas-rich galaxy, which ends up as an ultra-diffuse galaxy at the end of the tail,” the scientists wrote.

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