Imaging high redshift quasar hosts
Researchers at Tuorla Observatory have obtained images of very
distant galaxies which harbour supermassive black-holes. These
so-called quasars are thought to be a galaxy hosting a central,
super-massive black-hole. Normally the glare from the central
object of quasars is so bright that the host galaxies themselves
are very difficult to see.
Using the European Southern Observatory's Very Large
Telescope, Jari Kotilainen (Tuorla Observatory),
Renato Falomo (Osservatorio Astronomico di
Padova), Riccardo Scarpa (European Southern
Observatory) and Aldo Treves (Universita
dell'Insubria) have now obtained images of the host
galaxy of a particularly distant quasars. The galaxy is
one of the most distant host galaxies ever seen.
| Three quasars,
marked by arrows, imaged with the European Southern
Observatory's Very Large Telescope using adaptive
optics. In the right panel, the host galaxy is seen as
slight nebulosity around the central quasar. In the left
panel, a much more nearby spiral galaxy in the same field
of view as the quasar is marked G1; in the central panel,
the two nearby galaxies G1 and G2 are probably neighbours
to the quasar itself. Picture courtesy Jari
Kotilainen/ESO/VLT. |
The three quasars shown in the figure are at a redshift of
around 2.5, which is to say that the light from these quasars left
them when the Universe was only about 4 billion years old. The
Universe today is about 13.7 billion years old.
The quasars in the image appear almost as point sources but one
can just make out the dim nebulosity around them coming from the
host galaxies. Seeing these galaxies, and measuring their
properties relative to their more ordinary galactic cousins, can
reveal much about the conditions under which quasars form.
The research team used NACO/CONICA
on the VLT,
which uses adaptive optics to greatly improve the
resolution of the telescope by compensating for the
distorting effects of the atmosphere. CONICA itself
images the galaxies in the infrared region. The host
galaxy which was spotted is among the furthest ever seen.
Preprint available here
lisää suomeksi.
Posted 1st March 2005
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