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

SUPERNOVAE FROM WD-WD DIRECT COLLISIONS

Image: Supernova remnant N 63A. Credit: NASA/ESA/HEIC and The Hubble Heritage Team (STScI/AURA) Models for supernovae (SNe) related to thermonuclear explosions of white dwarfs (WDs) have been extensively studied over the last few decades, mostly focusing on single degenerate (accretion of material of a WD) and double degenerate (WD-WD merger) scenarios.

Scientists detect comets outside our solar system

An artist’s conception of a view from within the Exocomet system KIC 3542116. Credit: Danielle Futselaar Team of professional and citizen scientists identifies tails of comets streaking past a distant star Jennifer Chu | MIT News Office Scientists from MIT and other institutions, working closely with amateur astronomers, have spotted the dusty tails of six exocomets — comets outside our solar system — orbiting a faint star 800 light years from Earth. These cosmic balls of ice and dust, which were about the size of Halley’s Comet and traveled about 100,000 miles per hour before they ultimately vaporized, are some of the smallest objects yet found outside our own solar system. The discovery marks the first time that an object as small as a comet has been detected using transit photometry, a technique by which astronomers observe a star’s light for telltale dips in intensity. Such dips signal potential transits, or crossings of planets or other objects in front of a star, ...

Atmospheric Beacons Guide NASA Scientists in Search for Life

Beacons of life could help researchers identify potentially habitable worlds. Credits: NASA’s Goddard Space Flight Center/Mary Pat Hrybyk Some exoplanets shine brighter than others in the search for life beyond the solar system. New NASA research proposes a novel approach to sniffing out exoplanet atmospheres. It takes advantage of frequent stellar storms — which hurl huge clouds of stellar material and radiation into space — from cool, young dwarf stars to highlight signs of habitable exoplanets. Traditionally, researchers have sought potential biosignatures as ways of identifying inhabited worlds: byproducts from life as we know it such as oxygen or methane that over time accumulate in the atmosphere to detectable amounts. But with current technology, according to Vladimir Airapetian, lead author of a Nature Scientific Reports study published on Nov. 2, 2017, identifying these gases on distant terrestrial exoplanets is time-consuming, requiring days of observation time. The ne...

SpaceTime

Search This Blog