Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userA shock near the virial radius of the Perseus Cluster
118
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Previous X-ray studies of the Perseus Cluster, consisting of 85 Suzaku pointings along eight azimuthal directions, revealed a particularly steep decrease in the projected temperature profile near the virial radius (~r200) towards the northwest (NW). To further explore this shock candidate, another 4 Suzaku observations on the NW edge of the Perseus Cluster have been obtained. These deeper data were designed to provide the best possible control of systematic uncertainties in the spectral analysis. Using the combined Suzaku observations, we have carefully investigated this interesting region by analyzing the spectra of various annuli and extracting projected thermodynamic profiles. We find that the projected temperature profile shows a break near r200, indicating a shock with M = 1.9+-0.3. Corresponding discontinuities are also found in the projected emission measure and the density profiles at the same location. This evidence of a shock front so far away from the cluster center is unprecedented, and may provide a first insight into the properties of large-scale virial shocks which shape the process of galaxy cluster growth.
rate research
Read More
We investigate the galaxy population in a field of the Perseus cluster that roughly covers the virial radius of the cluster. The galaxies were selected on Schmidt CCD images in B and H alpha in combination with SDSS images. We present a catalogue of 1294 galaxies. Morphological information was obtained for 90% of the galaxies from the `eyeball inspection, partly supported by the surface brightness profile analysis. Redshifts were taken from SDSS, literature sources, and own spectroscopic observations and are available for 24% of the catalogues galaxies. The galaxy catalogue is used to derive cluster properties, such as radial profiles, indications of sub-structure, virial mass, and viral radius and to study the cluster galaxy population with regard to morphological types and peculiarities, star formation rates and active galactic nuclei. In addition to the statistical approach, we present brief individual descriptions of 18 cluster galaxies with conspicuous morphological peculiarities. (Abstract modified to match the arXiv format.)
Recent simulations have indicated that the dark matter halos of galaxy clusters should feature steep density jumps near the virial radius. Since the member galaxies are expected to follow similar collisionless dynamics as the dark matter, the galaxy density profile should show such a feature as well. We examine the potential of current datasets to test this prediction by selecting cluster members for a sample of 56 low-redshift (0.1<z<0.3) galaxy clusters, constructing their projected number density profiles, and fitting them with two profiles, one with a steep density jump and one without. Additionally, we investigate the presence of a jump using a non-parametric spline approach. We find that some of these clusters show strong evidence for a model with a density jump. We discuss avenues for further analysis of the density jump with future datasets.
Sloshing cold fronts in clusters, produced as the dense cluster core moves around in the cluster potential in response to in-falling subgroups, provide a powerful probe of the physics of the intracluster medium (ICM), and the magnetic fields permeating it. These sharp discontinuities in density and temperature rise gradually outwards with age in a characteristic spiral pattern, embedding into the intracluster medium a record of the minor merging activity of clusters: the further from the cluster centre a cold front is, the older it is. Recently it has been discovered that these cold fronts can survive out to extremely large radii in the Perseus cluster. Here we report on high spatial resolution Chandra observations of the large scale cold front in Perseus. We find that rather than broadening through diffusion, the cold front remains extremely sharp (consistent with abrupt jumps in density) but instead is split into two sharp edges. These results show that magnetic draping can suppress diffusion for vast periods of time, around ~5 Gyr, even as the cold front expands out to nearly half the cluster virial radius.
NGC1275, the central galaxy in the Perseus cluster, is the host of gigantic hot bipolar bubbles inflated by AGN jets observed in the radio as Perseus A. It presents a spectacular $H{alpha}$-emitting nebulosity surrounding NGC1275, with loops and filaments of gas extending to over 50 kpc. The origin of the filaments is still unknown, but probably correlates with the mechanism responsible for the giant buoyant bubbles. We present 2.5 and 3-dimensional MHD simulations of the central region of the cluster in which turbulent energy, possibly triggered by star formation and supernovae (SNe) explosions is introduced. The simulations reveal that the turbulence injected by massive stars could be responsible for the nearly isotropic distribution of filaments and loops that drag magnetic fields upward as indicated by recent observations. Weak shell-like shock fronts propagating into the ICM with velocities of 100-500 km/s are found, also resembling the observations. The isotropic outflow momentum of the turbulence slows the infall of the intracluster medium, thus limiting further starburst activity in NGC1275. As the turbulence is subsonic over most of the simulated volume, the turbulent kinetic energy is not efficiently converted into heat and additional heating is required to suppress the cooling flow at the core of the cluster. Simulations combining the MHD turbulence with the AGN outflow can reproduce the temperature radial profile observed around NGC1275. While the AGN mechanism is the main heating source, the supernovae are crucial to isotropize the energy distribution.
We present Suzaku observations of the galaxy cluster Abell 2029, which exploit Suzakus low particle background to probe the ICM to radii beyond those possible with previous observations (reaching out to the virial radius), and with better azimuthal coverage. We find significant anisotropies in the temperature and entropy profiles, with a region of lower temperature and entropy occurring to the south east, possibly the result of accretion activity in this direction. Away from this cold feature, the thermodynamic properties are consistent with an entropy profile which rises, but less steeply than the predictions of purely gravitational hierarchical structure formation. Excess emission in the northern direction can be explained due to the overlap of the emission from the outskirts of Abell 2029 and nearby Abell 2033 (which is at slightly higher redshift). These observations suggest that the assumptions of spherical symmetry and hydrostatic equilibrium break down in the outskirts of galaxy clusters, which poses challenges for modelling cluster masses at large radii and presents opportunities for studying the formation and accretion history of clusters.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
