A radio galaxy is a galaxy that emits an unusually big amount of energy
at radio wavelengths. In a thousand of galaxies there is just one radio
galaxy (Fig.1). Between them there are very rare (one in a million radio
galaxies) superpowerful objects, emitting at radio wavelengths the amounts
of energy many times greater than all the stars in our Galaxy.
For contacts - O.Zhelenkova.
Inside of each galaxy with an active nucleus (radio galaxies are among
them) there must be a system of a "central machine" responsible for
the colossal amount of the emitted energy from radio to gamma ranges.
As most of the astronomers believe, the main energy source in the
galactic nucleus is the accretion of matter into a deep relativistic
potential (possibly, into a massive black hole). Considering that in
this process the gravitation energy reprocessing coefficient is about 10%,
to be able to explain the power output of 1046erg/s we have
to have the rate of accretion of a bit more than one solar mass a year.
In a close proximity of the galaxy nucleus the conditions that trigger
relativistic beaming (jet) are possible (Fig.2). It is these very jets
that generate the glow in the gas cloud that surrounds the galaxy, which
we observe as a radio galaxy. Making a firing by the beams of high-energy
particles, the "central machine" may stop pumping the components into
the jets, which would then fly apart and flicker out with time. The radio
source in the galaxy lives quite a short, on the cosmic timescales,
life - about tens of millions years. The older the source, the farther
the radio components from the galaxy nucleus. The sizes of some radio
galaxies are millions of times larger than the sizes of the host galaxies
that are powering them. Sometimes a radio source in an active galaxy may
flare again if the needed conditions appear (a new portion of matter would
fall into the furnace of the "central machine").
Thanks to their intensive luminosity at radio wavelengths, the powerful
radio galaxies can be studied nearly at the borders of the observed Universe.
In the Special Astrophysical Observatory, under the direction of the member
of the Russian Academy of Sciences Yu.N.Parijskiy, the project is running
for the search of distant radio galaxies. The project uses both the
RATAN-600 radio telescope and the 6-m BTA optical telescope. As a result
of longstanding work, one of the most powerful distant radio galaxies,
RC J0311+0507, was found (arXiv:0705.2971). In the radio range at the
frequency of 500MHz it has the luminosity of L~3*1029W/Hz.
The light from this galaxy travels to Earth for 11 milliard years, and
its age is considered to be 1 milliard years.
New observations using the MERLIN interferometer (JBO, UK) at the
frequencies of 1.7 and 5GHz with high angular resolution (~150mas)
allowed estimating the mass of the galaxy nucleus. It appeared to be
close to the limiting mass for such objects, - more than a million
masses of the Sun. According to the new data, this radio galaxy may
be put into the Fanaroff-Riley type II (FRII) with highly asymmetric
external components and relatively intense emission of the
nucleus (Fig.3). One of the models explains the origin of such objects
in the early Universe via the merger of supermassive black holes,
resulting in high speed rotation of the black hole and high luminosity
of the source at radio wavelengths. However, to confirm this hypothesis
we need extensive and detailed observations of this object at the entire
range of frequencies, from radio to X-ray.
New optical observations on BTA and SCORPIO in several filters added new
strokes to the "portrait" of this object. In a narrow filter SED655,
the size of the object is greater (Fig.4) compared to other filters.
This is conditioned by an intense radiation of the hydrogen Lyman alpha
line of the gas surrounding the radio galaxy. It is ionized by nucleus
of the galaxy.
A paper is currently in preparation for print based on the above data:
"MERLIN Data on Z=4.51 Radio Galaxy RC~J0311+0507 and a Problem of SMBHs
in Early Universe",
Yu.Parijskij, P.Thomasson, T.Maxlow, O.Zhelenkova, A.Kopylov, N.Soboleva,
A.Temirova, O.Verkhodanov,T. Fatkhullin.
Fig.1. A double radio galaxy 3C219. A blue object
in the middle is an optical radio galaxy. Red shows the radio source
Model image of the radio galaxy with symmetrical
jets coming from the central region close to a supermassive black hole.
Fig.3. Image of RCJ0311+0507 (BTA+SCORPIO) in the
R filter, an image at 4.8GHz (a red contour, VLA, resolution 0.15"х0.15"),
an image at 1.7GHz (pink contours, MERLIN, resolution of 0.264"х0.132"),
an image at 5GHz (violet contours, MERLIN, resolution 0.11"х0.039").
Fig.4. Isophots (blue lines) of RCJ0311+0507 images,
obtained on BTA+SCORPIO in two wide band (R, I) and two narrow (SED655,
SED707) filters with radio images superimposed (pink lines).