A TEAM OF BULGARIAN ASTRONOMERS FOUND NEW STRUCTURES
IN A NUMBER OF ACTIVE GALAXIES
December 29, 2011
A team of Bulgarian astronomers found structures not previously reported that are related to the fueling of active galactic nuclei. There were used multi-year observational data of tens of galaxies obtained at the 2-m telescope of Rozhen NAO in the course of a project on active galaxies. The structures, including nuclear features with apparent sizes, marginal for detection at this class of telescopes, have been revealed due to the advanced approach in the reduction and analysis of the images obtained. The presence of a part of the newly-detected structures was confirmed on images obtained with the Hubble Space Telescope.
Active galactic nuclei are the most energetic sources of radiation known in the Universe. The fact that supermassive black holes reside in the centres of most galaxies, both active and inactive, raises the question what makes galaxies active and which mechanisms transfer the fuel to the active galactic nuclei. To address these issues, the authors study a sample of Seyfert (low-luminosity active) galaxies and a control sample of inactive galaxies. On the basis of statistical analysis, it was found that the two types of galaxies do not differ significantly regarding morphological structure and companions. This is the first study that compares the share of galactic rings in Seyfert and inactive galaxies, based on matched samples. The authors come to the corollary that the fueling of Seyfert nuclei is not directly related to the morphology and local environment of their host galaxies. The differences found may be related to the generally larger cold gas amount reported in the Seyfert disks in the framework of gas inflow. This research is representative of the characteristics of the low-luminosity active galactic nuclei. Its significance is emphasized by the fact that the relation between the nuclear activity and host galaxies is still debatable. It was published in the research journal “Astronomy & Astrophysics“ - “Optical multiband surface photometry of a sample of Seyfert galaxies. I. Large-scale morphology and local environment analysis of matched Seyfert and inactive galaxy samples“. The study was reflected by the weekly scientific review magazine “News of Science“ under the title “New Findings in Astrophysics Described from Bulgarian Academy of Sciences“.
The Seyfert galaxy NGC 7469 and its companion IC 5283. The gravitational interaction between the galaxies, resulting in a tidal tail in IC 5283, could trigger the nuclear activity in NGC 7469. The image is obtained at the 2-m telescope of Rozhen NAO.
The fueling of active galactic nuclei can be related to the feeding of animals - the metabolic rate corresponds to the so called accretion rate. The presentation entitled “How Are the Active Nuclei Fuelled... or on the Metabolism of Black Bears“, in which subjects to the metaphoric analogy are the black holes and black bears, was awarded in the competition for an original expose of a scientific research, organized by the Bulgarian Academy of Sciences, the Hirayama Ikuo Silk Road Museum and Foundation, Japan, and the Ikuo Hirayama Centre, Bulgaria.
For more information:
Dr. Lyuba Slavcheva-Mihova
lslav@astro.bas.bg
Institute of Astronomy and NAO, Bulgarian Academy of Sciences