ORIGIN OF RADIO EMISSION IN RADIO-QUIET QUASARS

Image Credit: NASA/Goddard Space Flight Center

Radio emission of radio-quiet quasars may be due to stars formation in the quasar host galaxy, to a jet launched by the supermassive black hole, or to relativistic particles accelerated in a wide-angle radiatively-driven outflow.

Recently some authors (Zakamska et al 2016) examine whether radio emission from radio-quiet quasars is a byproduct of stair formation in their hosts. They find that even the most generously computed star formation rates are insufficient to explain the observed radio emission, by about an order of magnitude. They cannot distinguish between radio emission due to compact weak jets and radio emission due to wide angle winds. The problem of distinguishing radio emission from compact jets from radio emission as a bi-product of radiatively driven has proven espexially difficult because the two mechanisms are similar in terms of energetics.

Read more>>
http://arxiv.org/pdf/1511.00013v2.pdf
http://mnras.oxfordjournals.org/content/455/4/4191.abstract

Comments

THE HITCHCHIKER'S GUIDE TO THE LOCAL SUPERCLUSTER

Image: Virgo Supercluster. Credit: Andrew Z. Colvin The Virgo Supercluster is a region with a diameter of 33 megaparsecs (~1000 times larger the Milky Way's diameter) containing at least 100 galaxy groups and clusters.

ORBITAL PERIODS OF THE PLANETS

For orbital period generally we refer to the sidereal period, that is the temporal cycle that it takes an object to make a full orbit, relative to the stars. This is the orbital period in an inertial (non-rotating) frame of reference (365,25 days for the earth).

Understanding neutron-star evolution from magnetar flares

Image: A rupture in the crust of a highly magnetized neutron star, shown here in an artist's rendering, can trigger high-energy eruptions. Fermi observations of these blasts include information on how the star's surface twists and vibrates, providing new insights into what lies beneath. Credits: NASA's Goddard Space Flight Center/S. Wiessinger Some of the most intriguing neutron stars are the magnetars: highly magnetised objects whose surface fields are inferred to be in excess of 10 14 G in some cases, and whose interior fields may reach 10 16 G. In contrast with many older, more predictable neutron stars, magnetars are volatile, alternating between quiescent states and highly energetic bursts and flares. Their most spectacular events are the giant flares, releasing over ~ 10 45 erg of energy in a very brief flash and decaying X-ray tail. The giant flares of magnetars are believed to be powered by colossal magnetic energy reservoirs. In a recent paper (Lan...

SpaceTime

Search This Blog