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# IKI RAS # Main # Spektr-RG.07.07.2020 09:00 eROSITA explores supermassive black holes in the early Universe In the center of our Galaxy is a black hole weighing 4 million solar masses. Such black holes are in the centers of almost all galaxies. As a rule, their mass is greater: sometimes not much, and sometimes it reaches several billion solar masses. Such supermassive black holes originated many billions of years ago, when the first stars and galaxies began to appear in the Universe, and grew due to the accretion of the surrounding material. This process was accompanied by the release of colossal energy, which allows us to detect young and growing massive black holes by their electromagnetic radiation emitted many billions of years ago. Such objects are called “quasars” or QSO – Quasi-Stellar Objects (“quasi-star objects”). The study of the nucleation and growth of supermassive black holes is one of the main scientific tasks of the Russian Spectrum RG orbital observatory, which will launch exactly one year on July 13 at the Baikonur Cosmodrome. In early June 2020, the eROSITA telescope, one of two telescopes on board the observatory , completed his first (of the planned eight) review of the entire sky in x-rays. During it was discovered more than a million x-ray sources. Before starting the review, in order to search and study the farthest and weakest objects, the eROSITA telescope conducted a deep scan of the so-called “Lokman holes” – a small part of the sky in which the absorption of X-rays by interstellar gas and dust of our Galaxy minimally and least hinders the observation of extragalactic objects. Scientists from the Space Research Institute under the guidance of Corresponding Member of the Russian Academy of Sciences Marat Gilfanov and Professor of the Russian Academy of Sciences Sergey Sazonov are working on eROSITA telescope source catalog and analyze this data to find the farthest and fastest growing supermassive black holes in the early Universe. The neural network SRGz, created at IKI RAS under the supervision of a candidate Alexandra Meshcheryakova’s Sciences, selected several dozen candidates for distant quasars from more than half a million X-ray sources discovered by eROSITA in half the sky, for which Russian scientists are responsible for processing the data. The most interesting of them were investigated in detail using optical telescopes as part of the Spectra-RG ground support program for sky surveys. Already in the first optical observations, previously unknown distant quasars were discovered. Among them: a quasar at z = 4.116, opened on the 1.6-meter telescope AZT-33IK of the Sayan Observatory of the Institute of Solar-Terrestrial Physics of the Russian Academy of Sciences in Buryatia; a quasar at z = 4.237, discovered at the Russian-Turkish 1.5-meter telescope (PTT -150) in Turkey; a quasar at z = 4.576, opened with the 6-meter BTA telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences in Karachay-Cherkessia. Observations were conducted under the supervision of a candidate physical and mathematical sciences. Sciences Rodion Burenin and Ph.D. Georgy Khorunzheva from IKI RAS and Professor Ilfan Bikmaev from Kazan Federal University. In addition, observations on a 2.5-meter telescope of the Caucasian Mountain Observatory of the State Astronomical Institute. PC. Sternberg Moscow State University M.V. Lomonosov confirmed that several more candidate objects are indeed quasars. The letter z denotes the “redshift” of the object, which corresponds to the distance to it. The redshifts of quasars are measured by the positions of bright emission lines in their spectra. The main one is the Lyman-alpha line, known from the school physics course, that occurs when an electron transfers from the second to the first level in a hydrogen atom. Under normal conditions, this line falls into the ultraviolet part of the spectrum, but in the spectra of distant quasars it appears in the visible range due to the large redshift caused by the expansion of the Universe.

Оптические спектры трех ранее неизвестных квазаров на красном смещении z>4, открытых телескопом eROSITA. Эти объекты были найдены нейронной сетью SRGz среди около полумиллиона источников, обнаруженных телескопом eROSITA, и их природа была подтверждена в ходе оптической спектроскопии на телескопах БТА, РТТ-150 и АЗТ-33ИКОсобый интерес представляют квазары на красных смещениях z>6, в эпоху, когда возраст Вселенной составлял менее миллиарда лет. До сих пор неясно, как за столь короткое по космическим масштабам время некоторые черные дыры смогли вырасти до колоссальных масс в несколько миллиардов масс Солнца. Другой важный вопрос современной астрофизики — взаимодействие между процессами формирования звезд в первых галактиках и ростом черных дыр в их ядрах. Не до конца исследована и роль квазаров в повторной ионизации Вселенной (200 миллионов — 1 миллиард лет после Большого взрыва). Из наблюдений в оптическом и инфракрасном диапазонах известно более 200 квазаров на z>6, однако рентгеновское излучение пока обнаружено лишь у примерно 20 из них.В работе кандидата физ.-мат. наук Павла Медведева и его коллег из ИКИ РАН и КФУ сообщается об открытии телескопом eROSITA рентгеновского излучения от квазара CFHQS J1429+5447 на красном смещении z=6,2 (соответствует возрасту Вселенной около 900 миллионов лет). Этот квазар был известен по наблюдениям в видимом и радиодиапазонах, но рентгеновское излучение от него зарегистрировано впервые. По данным телескопа eROSITA, рентгеновская светимость квазара составляет около 3×1046 эрг в секунду, что в несколько раз превышает предыдущий рекорд для квазаров на z>6. Taking into consideration the fact that the quasar radiates in the whole range of the electromagnetic spectrum, from radio to ultraviolet and x-rays, its full luminosity can be estimated even much higher — about 3×1047 erg per second. For comparison, the total luminosity of all two hundred billion stars in our Galaxy about a thousand times less! This means that the black hole in this quasar “weighs” more than 2 billion solar masses, and she had to “eat” around the Earth every second over several tens of millions of years.Quasar CFHQS J1429 5447 entered the field of view of the telescope eROSITA was registered during scans of the sky 10-11 December 2019, at the beginning of the review of the all-sky Observatory “Spektr-RG”. Observations at the telescope RTT-150 showed that the optical brilliance of the quasar remained about the same as 10 years before that, when he opened the telescope Canada-France-Hawaii.

X-ray image of the quasar CFHQS J1429 5447 at z=6,2 according telescope eROSITA (a quasar in the center of the image)

The image of the quasar CFHQS in the visible range from the telescope RTT-150. 150 (the position of the quasar is indicated by a slash long). The photons from the quasar in these images was emitted 12.8 billion years ago by accretion of matter onto a supermassive black hole with a mass of at least 2 billion SOLNEChNYKh CFHQS J1429 5447 is “radiogram”, that is, emits powerful radio waves. It is associated with the jets — the jets of matter that are emitted from the vicinity of the black hole at nearly the speed of light. Medvedev and colleagues hypothesized that the record x-ray luminosity of this quasar is associated with the inverse Compton scattering of the background radiation of the Universe in the relativistic jets of the substance. This process is particularly important in the early Universe where the energy density of the background radiation by more than three orders of magnitude higher than around contemporary objects. IKI scientists continue to search for such objects in the eROSITA data.


EDITOR’S NOTE: This article is a translation from Russian Language to English.

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