Subscribe free to our newsletters via your
. 24/7 Space News .

Optically Faint Radio Sources Reborn AGN
by Staff Writers
Lisbon, Portugal (SPX) Dec 13, 2011

File image.

A team of researchers, mainly from Centro de Astrofisica da Universidade do Porto (CAUP), has detected a rare type of active galactic nuclei (AGNs), which have simultaneously characteristics of young and old AGNs. This apparent discrepancy is thought to be due to a recent re-ignition of the central black hole.

The team cross-correlated a catalogue of over 13 thousand clusters with a catalogue at radio frequencies, searching for a link between AGNs and the clusters in which they reside. CAUP astronomer and principal investigator, Mercedes Filho, commented on this chance discovery: "Our initial project aimed to study radio galaxies in clusters. By chance, we found eight radio sources with extended structure (radio jets and lobes) that didn't show up in the optical images, which we found strange. So we decided to drop the initial project and pursue these strange radio galaxies."

In order to get more information about these eight objects, further observations in the infrared were made with the VLT (ESO). This allowed the team to detect the host galaxies, where the extended radio structures originated from.

While comparing the obtained spectra with known galaxy models, the team was able to conclude that these eight sources are rare objects - galaxies with characteristics common to active AGNs (that still have jet emission) and inactive AGNs (where the jet emission has turned off).

This (apparent) discrepancy can be explained with a relatively recent reactivation of the AGN, due to new material being accreted by the central black hole.

In general, when a black hole is active, it produces a jet along the galaxy's rotation axis. This jet can travel great distances, creating lobes visible at radio frequencies. When the black hole is not active, the jet shuts down, but the lobes can persist for a very long time (a minimum of 1 million years).

The original jet emission must have been interrupted sometime in the past, while the lobes, though fading, remain visible in the radio. According to Mercedes Filho, "Our objects have radio lobes, a sign of past activity, but the spectra tell us that the central black hole and the jet have recently been reactivated."

The black hole must have recently been replenished of new material (either through internal disk instabilities or interactions with other galaxies), which instigated a new jet emission, that started before the original radio lobes faded completely.

The team will now carry out a new set of observations, both in radio and gamma rays, to try and detect direct hints of young jets associated with the re-ignited central black hole.

The team members are Mercedes Filho (CAUP), Jarle Brinchmann (Leiden Observatory/CAUP), Catarina Lobo (CAUP/DFA-FCUP), and Sonia Anton (CICGE/FCUP and SIM/FCUL).. The article "Optically Faint Radio Sources: Reborn AGN?" was published in this month's issue of Astronomy and Astrophysics.


Related Links
Centro de Astrofisica da Universidade do Porto (CAUP)
Stellar Chemistry, The Universe And All Within It

Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks DiggDigg RedditReddit GoogleGoogle

Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News

Cosmic Explosion Explained Just in Time for Christmas
Fort Davis TX (SPX) Dec 07, 2011
An explosion far across the universe rattled astronomers last year on Christmas Day. Called a gamma-ray burst (GRB), it incited a flurry of activity from telescopes in space and on the ground, including the 2.1-meter Otto Struve Telescope at The University of Texas at Austin's McDonald Observatory. This year, just in time for Christmas, astronomers say they now know what happened - and it requir ... read more

Peres promotes Israeli moon probe

Hundreds of NASA's moon rocks missing: audit

Schafer Corp Signs Licensing Agreement with MoonDust Technologies

Russia wants to focus on Moon if Mars mission fails

System could be 'brain' for Mars rovers

Life possible on 'large parts' of Mars: study

Opportunity to Stop and Study Rocks

Russia could join ExoMars as full partner

TASC Wins $133.9 Million NASA Contract

US mulls tax break for space 'burials'

Ball Aerospace Delivers Orion Phased Array Antenna EDUs

Voyager Hits New Region at Solar System Edge

Two and a Half Men for Shenzhou

China honors its 'father' of space efforts

Philatelic Cover Reveals the secret names of second Taikonaut team

First Crew for Tiangong

ESA astronaut Andre Kuipers Ready For Launch To ISS

Astronaut TJ Creamer Learns Space Station Science From the Ground Up

FLEX-ible Insight Into Flame Behavior

Growing Knowledge in Space

AMOS-5 Communications Satellite Successfully Launched

Second Arianespace Soyuz rolled out for launch at Spaceport Kourou

O3b signs agreement with Arianespace for third Soyuz launch

NASA Announces Launch Date and Milestones for Spacex Flight

Giant Super-Earths Made Of Diamond Are Possible

New Planet Kepler-21b discovery a partnership of both space and ground-based observations

Astronomers Find Goldilocks Planet and Others

The Habitable Exoplanets Catalog, a new online database of habitable worlds

Researchers find best routes to self-assembling 3D shapes

Avatars develop real world skills

Tablets, e=readers closing book on ink-and-paper era

New insights into how the brain reconstructs the third dimension

The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement