Blazars: Staring down the throats of galactic Printing: monsters.

David English – Curtin University [email protected]

Introduction Classification What we don’t know • Blazars are among the brightest, most energetic and bizarre objects in the universe! Blazars and quasars as well as radio galaxies, are all types of active • Below is a multi-wavelength image of the radio galaxy Hercules • They are a type of quasar, and are not fully understood. galaxies, and have subsequent sub-classes. They are essentially A, taken by the Hubble Space Telescope and the VLA (Very different manifestations of active galaxies. What distinguishes them, Large Array). What are quasars? is the viewing angle from Earth, as seen in the diagram below. • Clearly shown is the relativistic jets radiating from the active galactic nuclei, forming huge radio lobes due to interactions • Quasars are extremely energetic and violent regions formed in Viewing down one of the relativistic jets is what is with the interstellar medium. the nuclei of most, if not all active galaxies. observed as a blazar. • Astrophysicists are working to understand how the relativistic • They are the result of material spiraling into a supermassive jets are formed, how they create such extreme broad spectrum black hole, as seen in the illustration below. radiation, and how they propagate over such vast distances. • This material forms an accretion disc, and emits massive • It is currently unknown as to why most galaxies, including the amounts of electromagnetic radiation across the whole Milky Way, appear to have dormant black holes that appear not spectrum. Viewing from 30˚ - 60˚ results in observing a to accrete great quantities of material. • Huge amounts of material fall into the black hole, which emits type of quasar. two powerful relativistic jets out into space. sci-techuniverse.blogspot.com/2016

Viewing at 90˚ results in observing a type of radio galaxy. astropix.ipac.caltech.edu Accretion Disc Supermassive Relativistic Jets black hole Looking down the barrel The material Along the axis of Current work The supermassive spiraling into the rotation of the When blazars are observed, we are looking down one of the powerful • Current low frequency radio astronomy offers significant black hole forms a black hole is the black hole, a relativistic jets. They appear as super bright variable objects, due to engine that drives information on sources exhibiting flat radio spectrums and high spinning accretion fraction of the the charged particles travelling towards us at near the speed of light, intensity, such as blazars. However, current surveys lack disc. The friction of the active galactic accreted particles emitting synchrotron radiation from moving through strong nuclei, pulling in sufficient sensitivity and therefore miss a substantial portion of the material are accelerated to magnetic fields in the jet. these objects. generates extreme surrounding relativistic speeds, heat and energy, material from stars and are propelled The amplification of brightness due to the close angle of observation • ICRAR (International Centre for Radio Astronomy Research) has and produces a as well as away in and relativistic speeds, is known as relativistic beaming. Unlike other recently used the MWA (Murchison Widefield Array) to conduct broad range of interstellar gas and tremendously active galactic nuclei, blazars produce a flat spectrum with no a new all sky survey called GLEAM, that will provide further electromagnetic dust. A powerful jets. These emission or absorption lines – which is unusual for active galaxies. insights into these sources, and discover new blazars. radiation. The supermassive black particles are some This makes it difficult to determine their velocities or distance. accretion disc is hole has a mass of 1 of the fastest known Summary million – 10 billion surrounded by a particles in the The unique orientation of blazars give astrophysicists an opportunity • Blazars are fascinating and powerful objects, which still hold a solar masses. large donut shape of universe, and can to research their emissions, and an insight into the workings of the lot of mystery – making them exciting for astronomers! dust and gas called travel hundreds of black holes at the heart of the galaxies. This could lead to discovering • For further information, check out; the torus. thousands of more about how energy is removed from the black hole, and how the imagine.gsfc.nasa.gov/science/objects/active_galaxies2.html. lightyears away. relativistic jets are created and accelerated.