ROSCOSMOS & DLR - Spectrum-RG Mission patch.
August 24, 2021
In the sky survey of the eROSITA telescope aboard the Russian space observatory Spektr-RG, an X-ray observation of the very massive cluster of galaxies SRGe CL2305.2-2248 was carried out for the first time. A further observational campaign using the BTA and RTT-150 telescopes helped to clarify the distance to the cluster and to study the galaxies included in it. The article with the research results was published on the arxiv.org electronic preprint site and accepted for publication in Letters to the Astronomical Journal.
Clusters of galaxies are the most massive gravitationally bound objects in the universe. They represent a thickening of dark matter, filled with galaxies and hot intergalactic gas, visible in the X-ray range, as well as a distortion of the spectrum of the relict radiation (the Sunyaev-Zeldovich effect). The total masses of galaxy clusters can reach 1015 solar masses and more. More massive objects have not yet formed during the lifetime of the universe.
Image above: Images of the SRGe CL2305.2-2248 galaxy cluster obtained with the SRG / eROSITA telescopes (left) and PTT-150 (right, artificial colors).
The SRGe cluster CL2305.2-2248 was first discovered in the millimeter range of electromagnetic radiation by observing the Sunyaev-Zeldovich effect in the surveys of the Atakama Cosmological Telescope, as well as the South Polar Telescope in Antarctica. However, the first X-ray observations were carried out with the help of the Spectra-RG observatory, which has been conducting a survey of the entire sky at the L2 Lagrange point since December 2019.
The estimated mass of the cluster from eROSITA data is M500 = (9.0 ± 2.6) 1014 solar masses. Such massive objects (with masses of the order of 1015 solar masses) are very rare and deserve further detailed study. The SRGe cluster CL2305.2-2248 is one of several dozen of the most massive galaxy clusters in the entire observable Universe and one of only a few of the most massive galaxy clusters at redshifts z> 0.6.
A high-precision spectroscopic measurement of the cluster redshift, z = 0.7573, was obtained using observations with the 6-meter BTA telescope (Special Astrophysical Observatory of the Russian Academy of Sciences). This corresponds to a distance of 6.6 billion light years (about half the lifetime of the universe). Deep photometric measurements of galaxies were carried out at the Russian-Turkish 1.5-meter telescope in Antalya (Turkey), which made it possible to study the galaxies of the cluster.
Spectr- RG (Spectrum-RG) space Telescope
According to the eROSITA telescope, the central part of the cluster looks disturbed in the X-ray range. This may be the result of the impact of floating gas bubbles, which are "inflated" by the active nucleus of one of the central galaxies in the cluster. Another possible explanation is that this may be a consequence of large-scale gas movements, which may arise, for example, due to a recent merger with a cluster of less mass. The distribution of galaxies in the plane of the sky is shaped like an hourglass. Such a strong central asymmetry of the distribution of galaxies in the plane of the sky may indicate a complex dynamic state of the cluster.
In the X-ray survey of the whole sky by the eROSITA telescope on board the Russian observatory "Spektr-RG", about 100 thousand galaxy clusters will be discovered, including all massive clusters with masses above 3·1014 solar masses in the observable part of the Universe. Their detailed study will help in solving many cosmological problems, in particular, it will put more precise constraints on the parameters of cosmological models.
This work was supported by the Russian Science Foundation grant 21-12-00210.
Source: IKI RAN.
Related links:
Astronomical Journal: https://arxiv.org/pdf/2108.09252.pdf
Spectrum-RG: https://www.roscosmos.ru/tag/spektr-rg/
IKI RAN: https://www.roscosmos.ru/tag/iki-ran/
ROSCOSMOS Press Release: https://www.roscosmos.ru/32291/
Images, Text, Credits: ROSCOSMOS/Orbiter.ch Aerospace/Roland Berga.
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