Séminaire/Seminar Galaxies |
| « A top-down take on (AGN) energy feedback in galaxy clusters » |
|
Subhabrata Majumder |
| The many approaches to estimating energy feedback in galaxy clusters, in simulations and semi-analytical modeling, are typically bottom-up where a prescription for feedback is laid down and results compared with observations. We, instead, take a top-down approach, which starts from observations and then tries to estimate the energy feedback they imply. Using X-ray and SZ data of clusters, we estimate the thermodynamic entropy of the intra-cluster medium and, then in comparison to simulations, we find the excess 'non-gravitational' entropy/energy for the sample spanning a large radial range from inside the cluster cores to cluster boundaries. Using this method, we present the first energy-feedback profile from observations, to the best of our knowledge. A number of interesting results follow: for example (i) the canonical value of excess energy of 1 Kev/particle is not found, (ii) pre-heating or any significant feedback in the ambient medium forming clusters is conclusively ruled out, (iii) the central peakiness of the excess energy profiles point at central in-situ (AGN) heating, (iv) integrating the feedback profiles, the excess energy is found to be correlated with central AGN power (from NVSS/GMRT), (v) a ratio of feedback energy to gravitational energy clearly shows that active galactic nucleus is more effective in transferring feedback energy to the ICM in less massive clusters, etc. Finally, we show how to constrain the underlying physics of AGN feedback with our top-down approach. |
|
jeudi 7 novembre 2019 - 11:30 Salle 281 Institut d'Astrophysique de Paris |
| Page web du séminaire / Seminar's webpage |