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The compact Hickson Group 98 consists of two "spots" in the center of the image. Each is a galaxy very similar to our own milky way. The point between them is a star in the foreground, as well as other circular elements in the image. The tadpole structure covers the pair of central galaxies and formed when the pair demolished a much smaller galaxy. The image was processed from the Stripe 82 project collection of the Instituto de Astrofisica de Canarias. Credit: N. Brosch / Tel Aviv University
A team of astronomers from Israel, the United States and Russia identified a disturbed galaxy resembling a giant tadpole, with an elliptical head and a long straight tail about 300 million light years away. Earth. The galaxy is a million light-years long, ten times larger than the Milky Way. The research is published today in the journal Monthly Notices from the Royal Astronomical Society.
"We have found an exceptional and exceptional relic of a disturbed galaxy," said Dr. Noah Brosch, of the Florence Observatory and George Wise of the School of Physics and Astronomy from Tel Aviv University, who led the research.
When galaxies are disturbed and disappear, their stars are either incorporated into more massive galaxies or ejected into an intergalactic space. "What makes this object extraordinary is that its tail alone measures nearly 500,000 light-years," says Professor R. Michael Rich of the University of California at Los Angeles. "If it was at the distance from the Andromeda galaxy, which lies about 2.5 million light years from Earth, it would reach one-fifth of the way to our own milky way." . "
Drs. Brosch and Rich collaborated on the study with Dr. Alexandr Mosenkov of the University of St. Petersburg and Dr. Shuki Koriski of the Florence Observatory and George Wise of the TAU and the University of St. Petersburg. 39, School of Physics and Astronomy.
According to the study, the giant "tadpole" was created by the disruption of a small, previously invisible, dwarf galaxy, containing mostly stars. When the gravitational force of two visible galaxies attracted stars into this vulnerable galaxy, the closest stars of the pair formed the "head" of the tadpole. The stars trailing in the victim galaxy formed the "tail".
"The extragalactic tadpole contains a system of two very close" normal "galaxy discs, each about 40,000 light-years in diameter," says Dr. Brosch. "Together with other nearby galaxies, galaxies form a compact group." The galaxy is part of a small group of galaxies called HCG098, which will merge into a single galaxy over the next billion years.
These groups of compact galaxies were identified for the first time in 1982 by astronomer Paul Hickson, who published a catalog of 100 such groups. The Hickson compact groups are looking at environments with high galaxy densities that are not at the core of a "group" of galaxies (the clusters contain thousands of galaxies themselves). The "tadpole galaxy" is listed in the Hickson Group catalog under number 98.
"In compact group environments, we believe we can study" net "examples of galaxy interactions, learn how material is transferred between members, and how newly accumulated material can modify and influence the growth and development of galaxies, "says Dr. Brosch.
For research, scientists have collected dozens of target images, each exposed through a wide filter that selects red light while virtually eliminating any light pollution. "We used a relatively small 70 cm telescope at the Wise Observatory and a similar telescope in California, both equipped with state-of-the-art CCD cameras," says Dr. Brosch. The two telescopes are collaborating on a project called Survey of Halos and Surrounding Galaxy Environments (HERON).
The new study is part of a long-term project led by Florence's TAU observatory and George Wise, which explores the low-light sky to detect the smallest details of the galaxies studied.
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More information:
Noah Brosch et al. Hickson Compact Group 98: a complex merged group with a giant tide and a gigantic envelope, Monthly Notices from the Royal Astronomical Society (2018). DOI: 10.1093 / mnras / sty2717
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