86,678 research outputs found
Chasing ICM cooling and AGN feedback from the macro to the meso scales in the galaxy cluster ZwCl 235
No full textAims. We aim to investigate the interplay between the intracluster medium (ICM) and the active galactic nucleus (AGN) in ZwCl 235, a galaxy cluster with high X-ray flux, an extended central radio galaxy, and evidence of multiphase gas at its center.
Methods. Using archival data from the Chandra telescope, the Very Large Array Sky Survey (VLASS), the LOFAR Two-metre Sky Survey (LOTSS), and the VLBA telescope, we performed a complete study of ZwCl 235, dissecting the dynamics of the ICM, the thermodynamic state of the central gas, and the properties of the brightest cluster galaxy (BCG). By means of radial profiles and 2D spectral maps, we measured the temperature, entropy, and cooling time of the ICM, and we compared the morphology of the central radio galaxy with the surrounding medium.
Results. We find evidence that ZwCl 235 is a sloshing cool core cluster in which the activity of the central galaxy has excavated a pair of cavities and possibly uplifted enriched gas to an altitude of ∼30 kpc. In the cluster core, the lowest entropy ICM is preferentially found in a 20 kpc-long filament tangential to the southern radio lobe of the AGN. We argue that the observed cool (∼1.3 keV) filament is likely produced by a combination of sloshing and stimulated ICM cooling, which may be fueling the central supermassive black hole. Additionally, we determined that the X-ray emission of the BCG originates from a ∼1.4 keV plasma kernel, which extends for 5 kpc in radius and has a short cooling time (∼240 Myr), and it could represent the thermal corona of the BCG.
Conclusions. Overall, we propose that several sources (the large-scale ICM, the low entropy filament, and the ∼1.4 keV kernel) of cold material are currently feeding the central AGN, and that the ICM cooling cycle expectations are met from the macro scales (between 5−100 kpc) to the meso scales (≤5 kpc) of AGN feedback
A Chandra study of Abell 795 - A sloshing cluster with an FR0 radio galaxy at its centre
No full textWe present the first X-ray dedicated study of the galaxy cluster Abell 795 (A795) and of the Fanaroff-Riley type 0 (FR0) hosted in its brightest cluster galaxy. Using an archival 30 ks Chandra observation, we study the dynamical state and cooling properties of the intracluster medium (ICM), and we investigate whether the growth of the radio galaxy is prevented by the surrounding environment. We discover that A795 is a weakly cool-core cluster, with an observed mass deposition rate ≲14 M☉ yr−1 in the cooling region (central ∼66 kpc). In the inner ∼30 kpc, we identify two putative X-ray cavities, and we unveil the presence of two prominent cold fronts at ∼60 and ∼178 kpc from the centre, located along a cold ICM spiral feature. The central galaxy, which is offset by 17.7 kpc from the X-ray peak, is surrounded by a multi-temperature gas with an average density of ne = 0.02 cm−3. We find extended radio emission at 74-227 MHz centred on the cluster, exceeding the expected flux from the radio galaxy extrapolated at low frequency. We propose that sloshing is responsible for the ICM spiral morphology and the formation of the cold fronts, and that the environment alone cannot explain the compactness of the FR0. We argue that the power of the cavities and the sloshing kinetic energy can reduce and offset cooling. Considering the spectral and morphological properties of the extended radio emission, we classify it as a candidate radio mini-halo
The central FR0 in the sloshing cluster Abell 795: Indications of mechanical feedback from Chandra data
No full textWe present a detailed study of the galaxy cluster Abell 795 and of its central Fanaroff-Riley Type 0 (FR0) radio galaxy. From an archival Chandra observation, we found a dynamically disturbed environment with evidences for sloshing of the intracluster medium. We argue that the environment alone cannot explain the compactness of the radio galaxy, as similar conditions are also found around extended sources. We identified a pair of putative X-ray cavities in the proximity of the center: These could have been created in a past outburst of the FR0, and dragged away by the large-scale gas movement. The presence of X-ray cavities associated with a FR0 could open a new window on the study of jet power and feedback properties of this recently discovered class of compact radio galaxies
Causa ed autonomia privata nella giurisprudenza di legittimità e di merito: dai contratti di viaggio ai derivati sul rischio di credito
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A first chandra view of the cool core cluster A1668: Offset cooling and AGN feedback cycle
No full textWe present a multiwavelength analysis of the cluster A1668, performed by means of new EVLA and Chandra observations and archival Hα data. The radio images exhibit a small central source (∼14 kpc at 1.4 GHz) with L1.4GHz ∼ 6 1023WHz-1. The mean spectral index between 1.4 GHz and 5 GHz is ∼-1, consistent with the usual indices found in BCGs. The cooling region extends for 40 kpc, with bolometric X-ray luminosity Lcool = 1.9 ± 0.1 1043 erg s-1. We detect an offset of ∼6 kpc between the cluster BCG and the X-ray peak, and another offset of ∼7.6 kpc between the Hα and the X-ray peaks. We discuss possible causes for these offsets, which suggest that the coolest gas is not condensing directly from the lowest-entropy gas. In particular, we argue that the cool ICM was drawn out from the core by sloshing, whereas the Hα filaments were pushed aside from the expanding radio galaxy lobes. We detect two putative X-ray cavities, spatially associated with the west radio lobe (cavity A) and the east radio lobe (cavity B). The cavity power and age of the system are Pcav ∼ 9 × 1042 erg s-1 and tage ∼ 5.2 Myr, respectively. Evaluating the position of A1668 in the cooling luminosity-cavity power parameter space, we find that the AGN energy injection is currently consistent within the scatter of the relationship, suggesting that offset cooling is likely not breaking the AGN feedback cycle
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