Astronomers using a new telescope called the Dragonfly Telephoto Array have discovered seven new dwarf galaxies the field of a nearby spiral galaxy known as Messier 101 (M101).
This image shows the nearby spiral galaxy Messier 101 and the seven newly discovered dwarf galaxies. Image credit: Allison Merritt et al.
“We got an exciting result in our first images. It was very exciting. It speaks to the quality of the telescope,” said Allison Merritt, a graduate student at Yale University and the lead author of a paper published in the Astrophysical Journal Letters (arXiv.org pre-print).
The telescope got its name – Dragonfly – because its lenses resemble the compound eye of an insect. It uses eight telephoto lenses with special coatings that suppress internally scattered light. This makes the telescope uniquely adept at detecting the very diffuse, low surface brightness of the newly discovered galaxies.
Allison Merritt and her colleagues used the Dragonfly Telephoto Array to search for dwarf galaxies in the field of the massive spiral galaxy M101.
They identified seven large, low surface brightness galaxies around M101.
“Given their large apparent sizes and low surface brightnesses, these objects would likely be missed by standard galaxy searches in deep fields,” the astronomers said.
They said that the galaxies are similar to those of well-studied dwarf galaxies in the Local Group, such as Sextans I and Phoenix.
The team will tackle a key question next: are these seven newly found galaxies dwarf satellites of M101, or are they located much closer or farther away, and just by chance are visible in the same direction as M101?
“If it’s the latter, these objects represent something entirely different. There are predictions from galaxy formation theory about the need for a population of very diffuse, isolated galaxies in the Universe. It may be that these seven galaxies are the tip of the iceberg, and there are thousands of them in the sky that we haven’t detected yet,” Allison Merritt said.
“I’m confident that some of them will turn out to be a new class of objects. I’d be surprised if all seven of them are satellites of M101,” said Dr Pieter van Dokkum of Yale University, who is a co-author of the discovery.
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Allison Merritt et al. 2014. The Discovery of Seven Extremely Low Surface Brightness Galaxies in the Field of the Nearby Spiral Galaxy M101. ApJ 787, L37; doi: 10.1088/2041-8205/787/2/L37
