Telescope Images Distant, Dim Dwarf Galaxies

A ground-based telescope recently helped discover seven distant dwarf galaxies that could contain clues to the evolution of galaxies and even dark matter.

The dwarf galaxies appear in the same region of the sky as galaxy M101, also known as the Pinwheel Galaxy, which is some 21 million light-years away from Earth. They have been overlooked by previous surveys because of their diffuse, low surface brightness (µ g ~ 25.5 to 27.5 mag arcsec^-2), according to astronomers at Yale University.

Yale astronomers used the Dragonfly Telephoto Array to detect the diffuse light of distant dwarf galaxies. Images courtesy of Yale University.

The telescope used to image the dwarf galaxies, called the Dragonfly Telephoto Array, incorporates eight telephoto lenses with coatings that suppress internally scattered light. It was designed by Yale professor Dr. Pieter van Dokkum and Dr. Roberto Abraham of the University of Toronto.

It remains to be seen whether the dwarf galaxies are orbiting M101, or if they are closer or farther away. Their properties are similar to those of well-studied dwarf galaxies within the Local Group of galaxies, the researchers said.

“I’m confident that some of them will turn out to be a new class of objects,” van Dokkum said. “I’d be surprised if all seven of them are satellites of M101.”

This image shows the field of view from the Dragonfly Telephoto Array, centered on galaxy M101. Inset images highlight the seven newly discovered dwarf galaxies.

If they are satellites, their absolute magnitudes are in the range of -11.6 < M_v < -9.3 and their effective radii are 350 parsecs to 1.3 kiloparsecs.

“There are predictions from galaxy formation theory about the need for a population of very diffuse, isolated galaxies in the universe,” said Yale graduate researcher Allison Merritt. “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.”

The researchers said they have been granted access to the Hubble Space Telescope to further their examination.

Their findings were published in The Astrophysical Journal Letters (doi:10.1088/2041-8205/787/2/L37).

For more information, visit www.yale.edu.