Abstract Details
| Name: Joydeep Bagchi Affiliation: IUCAA Conference ID: ASI2015_1052 Title : Spiral galaxy radio jets: The secret sits in the middle and knows Abstract Type : Invited Abstract : All galaxies may contain a central massive black hole, but presently the majority are quiet and inactive. A fraction of these black holes however accrete so much matter that they outshine the combined light from all their stars. These active galaxies occasionally also launch radio jets, which shoot out from the active nucleus upto Mpc distances, earning themselves the title of 'radio galaxies'. However, powerful radio jets on >100 kpc scales are nearly always launched from the nuclei of elliptical galaxies and not spirals, and the typical radio luminosity of spiral galaxies is about 10^3-10^4 times feebler than ellipticals, making them comparatively radio-quiet. The physical origin of this dichotomy and the mechanism by which relativistic jets are launched from accretion disks have long been the subject of intense investigations, yet the issue still remains unresolved despite a wealth of observations. Recently observations of a few rare spiral galaxies with >100 kpc jets have generated an intense renewed interest in this field. I discuss our recent discovery of an extraordinary spiral galaxy J2345-0449, ejecting record 1.6 Mpc scale jets, that challenges the conventional wisdom and provides a rare opportunity for probing the physics of dichotomous dependence of relativistic jet formation on the galaxy morphology and its central black hole properties - like its mass and spin. We show that these huge radio jets are probably triggered via the so-called "Blandford-Znajek" mechanism, resulting from a high mass and fast spin acquired by the central black hole. The estimated mass of this black hole is unusually high for a spiral galaxy which is extremely massive too. Our ground breaking results point towards an unusual formation route which has assembled coevally, both the massive, spinning black hole and the fast-rotating galactic disk over a cosmological time scale. Our findings provide new insights into the formation process of super massive black holes and the origin of relativistic jets in the galactic nuclei, and this remarkable galactic system also serves as a uniquely powerful laboratory for many future studies. |