Optical image (blue) of the galaxy 4C12.50. The inset shows a zoom in of
the plasma jet and the cold gas (orange). The gas is distributed in a
compact cloud (dark orange) and filaments (light orange) as result of
the strong impact with the plasma jet. Credit: optical:
HST/STSci/Tadhunter et al.; radio: VLBI, Morganti et al. 2013.
The jets which are shot away into space by the supermassive black hole
in the centre of a galaxy, clear gas away from the galaxy. The first
clear evidence of this was obtained by a team led by Raffaella Morganti
(ASTRON, University of Groningen). The results will be published in
Science on the 6th of September.
Astronomers have been puzzled by the fact that many galaxies in the
Universe seem to be depleted of their gas and are therefore unable to
form any new stars. Fast outflows of gas have been observed
in the past, but the mechanism driving these outflows was not
understood. The suspicion that the powerful plasma jets that are shot
into space by the central supermassive black hole are responsible for
the expulsion of the gas has now been confirmed.
The nucleus of the galaxy 4C12.50 was observed with ultra-high
resolution using a global Very Long Baseline Interferometry (VLBI)
network, an array of radio telescopes across different continents which
form a telescope the size of the earth. The high-resolution images
resulting from the VLBI observations allowed the team to pin down the
location of the gas outflow and to determine the speed with which the
gas leaves the galaxy.
Morganti: "We suspected the importance of these radio jets from previous
studies using for example the Westerbork Synthesis Radio Telescope.
With these observations at much higher resolution we
were finally able to map the distribution of the gas. It could not have
been in better agreement with our expectations!"
The astronomers found that the gas is flowing out of the galaxy at a
velocity of 1000 kilometers per second. Despite the strong push received
from the jet, the temperature of the gas is low. quot;This was quite
unexpected", says coauthor Tom Oosterloo (ASTRON, University of
Groningen). "But this is exactly what is needed to make theory of galaxy
formation and observations to agree. It is in particular cold gas that
is the fundamental building block of new stars, but this gas is being
expelled by the jet".
Using a global array of radio telescopes we are able to peek into the
nucleus of 4C12.50, located two billion light years from the earth.
Zsolt Paragi, astronomer at JIVE and coauthor: "These
observations, combining telescopes from both the European VLBI Network
and the Very Long Baseline Array in the U.S., allowed us to trace gas at
the immediate proximity - just 300 light years - of the black hole of
4C12.5."
The success of the observations means that VLBI is a suitable technique
to study the effect of the super massive black hole on the gas in its
vicinity. Morganti will use this technique to study more objects where
gas outflows are suspected to exist in the project ‘Exploiting new radio
telescopes to understand the role of AGN in galaxy evolution', for
which Morganti received a ERC Advanced Grant last year.
***
More information:
About ASTRON
ASTRON is the Netherlands Institute for Radio Astronomy (www.astron.nl).
Its mission is to make discoveries in radio astronomy happen, via the
development of novel and innovative technologies, the operation of
world-class radio astronomy facilities, and the pursuit of fundamental
astronomical research.
About JIVE
The Joint Institute for VLBI in Europe (JIVE, www.jive.nl) is a scientific foundation with a mandate to support the operations of the European VLBI Network (EVN, www.evlbi.org).
For this purpose it maintains, operates and develops the EVN data
correlator, a powerful supercomputer that combines the signals from
radio telescopes located across the planet.
Contact:
Prof. dr. Raffaella Morganti, ASTRON, RuG
E-mail: morganti@astron.nl
Tel: +31(0)521-595100
Mob: +31 (0)6-11952523
Prof. dr. Tom A. Oosterloo, ASTRON, RUG
E-mail: oosterloo@astron.nl
Tel: +31(0)521-595779
Dr. Zsolt Paragi
E-mail: paragi@jive.nl
Tel: +31(0)521-596536
Article:
Radio Jets Clearing the Way Through a Galaxy: Watching Feedback in Action, R. Morganti, J. Fogasy, Z. Paragi, T. Oosterloo, M. Orienti, Science, 6 September 201.
