Max Planck Institute for Astronomy - Annual Report 2007

48 II. Highlights
Flux [10 –23 W cm –2 nm]
15
10
5
0
J08360054
J00050006
J14111217
J13060356
J10300524
The astronomers established this edge visually in the
five quasar spectra. In this manner, they could calculate
relatively uniform Strömgren radii of around 16 million
light years. The interesting question arises as to how
long the quasars needed to create this sphere around
themselves.
R S
R S
R S
650 700 750 800 850
Observed frame wavelength [nm]
R S R S
Fig. II.6.5: Gunn-Peterson trough in the five quasar spectra
on the “blue” side of the Lyman-a line. The size of the
Strömgren spheres, R S , is marked.
The activity phase depends on several quantities,
especially the emission rate of ionizing photons and the
density of neutral hydrogen. Given certain assumptions,
these quantities permit the determination of a lower limit
for the activity period. However, the values determined
in this way are very uncertain. Depending on the method
used, the results for the five quasar activity times are
between 6 and 90 million years or, alternatively, between
one and 20 million years. In this case, the values are
small in comparison to the universe’s age (at that time)
of 900 million years. We were thus observing the quasars
in a very early activity phase, according to cosmic
standards.
With the described research, Dominik A. Riechers
completed his dissertation. In this reporting year, he graduated
and received a Hubble Postdoctoral Fellowship at
the California Institute of Technology from 2007 to 2010
for his research project “From the Epoch of Reionization
to the Peak of Galaxy Formation: Properties of Intensely
Star-Forming Galaxies in the Early Universe”.
Further steps will consist of broadening the current
data base. The MPIA team has therefore already applied
for the observation of an additional 23 quasars out of the
SDSS. In this study, particular attention will be paid to
fainter objects with less massive black holes.
Jaron D. Kurk, Fabian Walter, Dominik A. Riechers,
Hans-Walter Rix. In cooperation with:
Steward Observatory, Tucson (USA),
Osservatorio Astronomico di Roma (Italien),
Princeton University (USA),
National Radio Astronomy Observatory, Socorro (USA),
Landessternwarte Heidelberg