In particular, we identify a faint X-ray bridge connecting the group with the cluster, which is convincing proof that NGC 4839 has already crossed the main cluster. In this study, we discuss the rich morphology revealed by the X-ray observations (also in combination with the SZ data) and argue that the most salient features can be naturally explained by a recent (on-going) merger with the NGC 4839 group. The stability of the instrumental background and operation of the SRG Observatory in the scanning mode provided us with an excellent data set for studies of the diffuse emission up to a distance of $\sim 1.5R_$ from the Coma center. The data cover $\sim3^\circ\times 3^\circ$ area around the cluster with a typical exposure time of more than 20 ks.
Coma x ray pdf#
Churazov and 4 other authors Download PDF Abstract:This is the first paper in a series of studies of the Coma cluster using the SRG/eROSITA X-ray data obtained in course of the Calibration and Performance Verification observations. X-ray morphology, recent merger, and radio halo connection, by E. Elliptical galaxies must contain about five times as much mass in dark matter as the amount present in stars and gas.Download a PDF of the paper titled Tempestuous life beyond R_500: X-ray view on the Coma cluster with SRG/eROSITA. The conclusion: there is not enough mass in the stars and gas to provide the necessary gravity.
Chandra and other X-ray telescopes can be used to measure the hot gas pressure, and observations with optical telescopes can be used to determine the mass of the stars. The pressure of the hot gas is balanced with the gravitational pull of all the mass in a galaxy. Large elliptical galaxies have extended atmospheres of hot gas which appear to be in equilibrium. Many subsequent studies confirmed this discovery, and the general picture that has emerged is that of a disk of stars and gas embedded in a large, spherical halo of dark matter. Pioneering work by Vera Rubin and her colleagues showed that, much to their surprise, the required mass of many spiral galaxies is much larger than the observed mass of all the visible stars and gas. In a similar way, astronomers can calculate the mass of a galaxy by measuring the acceleration of clouds orbiting on the outer edges of a galaxy. * Cloud of dark matter containing most of the mass of Galaxy. Unlike the case of Uranus, where the gravity of Neptune adds a fraction of a percent to the gravitational force acting of Uranus, the extra force needed in the cases described below is several hundred percent! It is no exaggeration to say that solving the dark matter problem will require a profound change in our understanding of the universe. Today, astronomers are faced with a similar, though much more severe, problem.
The solution turned out to be Einstein's theory of general of relativity, which modified Newton's theory. In contrast, the attempt to explain the anomalies in the motion of Mercury as due to the existence of a new planet, called Vulcan, did not succeed. This procedure is still the primary method used to discover planets orbiting stars.Ī similar line of reasoning led to the detection in 1862, of the faint white dwarf Sirius B in orbit around the bright star Sirius. For example, the anomalous motion of Uranus led astronomers to suggest that an unseen planet existed, and a few years later, in 1846, Neptune was discovered.
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