Dr Amitesh Omar and his former student Dr Sumit Jaiswal from the Department of Science and Technology’s Aryabhatta Research Institute of Observational Sciences (ARIES) undertook the study of several such galaxies.
Dwarf galaxies: ARIES astronomers trace the mystery behind aberration in formation of stars in dwarf galaxies! Among the billions of galaxies in the universe, some are dwarf ones, which are about 100 times less massive than the Milky Way. While the rate of formation of most of these galaxies is also slower than the rate of the massive galaxies, there have been instances where dwarf galaxies have formed stars at a rate that is 10 to 100 times more than the Milky Way. However, it has been found that such activities do not last more than a few tens of millions of years, which is a short time as compared to the average age of such galaxies — a few billion years.
Now, Indian scientists observing dozens of such galaxies have found a clue behind this abnormal star formation rate among dwarf galaxies. In a statement, the Union Ministry of Science and Technology said that distubed distribution of hydrogen among such galaxies and recent collisions between galaxies is the reason behind such an aberration.
Dr Amitesh Omar and his former student Dr Sumit Jaiswal from the Department of Science and Technology’s Aryabhatta Research Institute of Observational Sciences (ARIES) undertook the study of several of such galaxies using two telescopes — the 1.3-metre Devasthal Fast Optical Telescope (DFOT), which is based near Nainital, and the Giant Meter wave Radio Telescope (GMRT). The DFOT operated at optical wavelengths which were sensitive to detect the optical line radiation that was emanating from the ionized Hydrogen. On the other hand, the GMRT consisted of 30 dishes of 45-metre diameter, all of which worked in tandem to produce interferometric images through spectral line radiation at 1420.40 MHz coming from the neutral Hydrogen in these galaxies.
A very high density of Hydrogen in the galaxies is required to form stars at such a high rate. The team at ARIES, analyzing the 1420.40 MHz images, found that these galaxies had very disturbed hydrogen. The release added that while a nearly symmetric hydrogen distribution can be expected in well-defined orbits in galaxies, it was found that in these dwarf galaxies, the hydrogen was irregular and sometimes not moving in well-defined orbits.
It was also found that around these galaxies, some hydrogen was detected in isolated clouds, plumes and tails, like the other galaxy recently collided or brushed away with these galaxies. The gas was scattered around the debris around these galaxies. Sometimes, multiple nuclei and high concentration of ionized hydrogen in the central region was also observed, the statement said. While the collision of galaxies was not directly detected, various signatures of it were revealed, and these help in building up a story. Therefore, the research suggests that recent collisions between two galaxies trigger intense star formation.