Images of 3 DOG’s. The left, middle, and right panels show optical image from HSC, near-infrared image from VIKING, and mid-infrared image from WISE, respectively. The image size is 20 square arcsecond (1 arcsecond is 1/3600 degree). It is clear that DOGs are faint in the optical, but are extremely bright in the infrared. Credit: Image courtesy of National Astronomical Observatory of Japan
As they harbor rapidly growing black holes in their centers, these results give us clues for understanding the evolution of galaxies and supermassive black holes. The research group discovered 48 DOGs, and measured how common they are using Subaru Strategic Program with Hyper Suprime-Cam (HSC), a new wide-field camera with a field of view 9X the size of the moon.
How did galaxies form and evolve during the 13.8-billion-year history of the universe? Almost all massive galaxies harbor a supermassive black hole whose mass reaches up to a 100 000 or even a billion X the sun’s mass, and their masses are tightly correlated with those of their host galaxies. This suggests supermassive black holes and their host galaxies have evolved together.
Dr. Yoshiki Toba (Ehime University) and team focused on the Dust Obscured Galaxies (DOGs) as a key population to tackle the mystery of the co-evolution of galaxies and black holes. DOGs are very faint in visible light, because of the large quantity of obscuring dust, but are bright in the infrared. The brightest infrared DOGs in particular are expected to harbor the most actively growing black hole. In addition, most DOGs are seen in the epoch when the star formation activity of galaxies reached its peak, 8-10 billion years ago. Thus both DOGs and their black holes are rapidly growing, at an early phase of their co-evolution. However, since DOGs are rare and are hidden behind significant amount of dust, previous visible light surveys have found very few such objects.
Each of these is DOGs are 10 trillion times more luminous in the infrared than the sun. The number density of these luminous DOGs is about 300/ cubic gigaparsecs. The all-sky survey data with NASA’s WISE are crucial to discover spatially rare DOG while the VIKING data are useful to identify the DOGs more precisely.
“The Subaru Strategic Program with c has just begun. In the near future, exciting results will be released not only from studies on galaxy evolution, but also from in fields such as solar systems, stars, nearby galaxies, and cosmology.” said Professor Tohru Nagao. http://subarutelescope.org/Pressrelease/2015/08/26/index.html
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