Discoveries in the cosmic family
The intriguing object we are talking about was called NGC2276-3c and is located in one of the spiral arms of the galaxy NGC 2276, about 100 million light years from Earth. NGC2276-3c seems to have all the characteristics to be what astronomers call a “black hole of intermediate mass”.
In the universe there is a cosmic object of recent discovery that could help shed light on unresolved issues concerning the evolution of the black holes and their influence on the environment around them. According to the findings in a study conducted with Chandra, the X-ray telescope NASA, it would seem that this object should be to complete the picture of the family of the black holes.
“In paleontology, the discovery of some fossils may help scientists to bridge gaps between different evolutionary dinosaurs,” says Tues Mezcua the Harvard-Smithsonian Center for Astrophysics, who led the study. “In astronomy we do the same thing, but we need to go digging in distant galaxies millions of light years to unearth the stars we’re looking for.”
For many years, scientists have found convincing evidence for black holes of smaller size, which contain five to thirty times the mass of the sun. We also have a lot of information about the so-called supermassive black holes, who reside at the center of galaxies and contain millions or even billions of solar masses.
As the name suggests, the black holes of intermediate mass represent a class that lies somewhere between these two groups, with masses between hundreds and thousands of solar masses. One of the reasons why these black holes intermediates are important is that they might be the ancestors of supermassive black holes, formed in the early stages of the universe. “Astronomers are looking for a long time these black holes of average size,” said Tim Roberts of the University of Durham, co-author of the study. “In the past there have been indications that could exist, but have always behaved like distant relatives who have no interest to be discovered.”
The study of NGC2276-3c was based on data in the Chandra X-ray band and data of the European Very Long Baseline Interferometry (VLBI) Network for the radio band. The source was observed for about the same amount of time in the two bands, and the data obtained, together with the theoretical models for the emission in the radio and in the high energy part of black holes, allowed estimating the mass of this object. The result was an estimate of about 50,000 solar masses, putting NGC2276-3c range of black holes of intermediate mass.
Credit: Chandra, XMM-Newton
“We found that NGC2276-3c presents a similar behavior to both black holes of stellar nature,” said Andrei Lobanov of the Max Planck Institute for Radio Astronomy in Bonn, co-author of the work. “In other words, this object allows us to bring together all the great family of the black holes.”
In addition to its mass, NGC2276-3c has another surprising property: a radio jet that extends up to 2,000 light years. The region is located in front of the jet seems devoid of young stars for a radius of about 1,000 light years. This confirms that the black holes of intermediate mass have a strong influence on the surrounding environment, since it seems that the jet has cleaned up the region by the gas, suppressing the formation of new stars. Future studies of this jet could provide valuable information on the effects of the large scale of this type of black holes on the universe in its earliest stages of life.
The position of NGC2276-3c along a spiral arm of the galaxy it confronts us with new questions. The black hole has formed in the galaxy or it comes from the central region of a dwarf galaxy that collided with NGC 2276 in the past?
NGC2276-3c is one of eight sources known as ultraluminous X-ray sources (ULX, X-ray sources ultra-bright) in the galaxy NGC 2276. “The ULX sources are not nuclear X brightness much greater than that expected for a stellar mass black hole, “says Anna Wolter INAF – Osservatorio Astronomico di Brera,” due to ‘acute vision’ of the satellite Chandra we found as many as 8 ULX in the galaxy NGC 2276, a spectacular object and active in all bands, third for number of ULX hosted.” We know hundreds of ULX, discoveries over the last 30 years, but their nature is still the subject of debate, and for some the assumption is that they are black holes of intermediate mass.