Max Planck Institute for Astronomy - Annual Report 2007

74 III. Selected Research Areas
a b c
masses per year while the quasar emission is primarily
fed through accretion.
These data, together with information relating to CO
emission, show that both the quasar and also the companion
galaxy possess a ul i r g type luminosity: The
quasar is surrounded by some dust and a rather masspoor
host galaxy and its direct environment emits reprocessed
quasar light at the ul i r g level. For its part,
the companion galaxy is rather dust-rich and produces
roughly 300 solar masses in new stars per year. The luminosity
emitted hereby and the large amount of dust
also provide for ul i r g strength infrared emission. In
such a system, the interaction of the quasar with the
companion galaxy plays an important role, both in triggering
the massive star formation as well as in its core
activity. Only the combination of the highest level of
spatial resolution by HST and VLT and multi-wavelength
data allowed for an analysis of these most diverse
physical processes.
HST and CO S m O S
d e
After the MPIA ge m S project led by Hans-Walter Rix,
co S m o S (Cosmic Evolution Survey) is the next and largest
HST project with, among other things, the goal of
tracking down the nature of quasars and their host galaxies.
More than one hundred scientists from the USA,
Italy, France, Germany, Switzerland, and other coun-
Fig. III.2.4: The quasar HE 0450–2958 spatially resolved at
three wavelengths a) in the visual (V-band, taken with the HST
ACS-HRC camera), c) in the near infrared (H-band, taken with
the HST ni c m o S-NIC2 camera), e) in the mid-infrared (N-Band,
taken with viSir on the eSo VLT). The HE 0450–2958 system
at z 0.285 consists of a quasar in the middle, a neighboring
galaxy interacting with the quasar on the left, and a foreground
star belonging to our milky way on the right. The b) and c) images
were derived from a) and c) respectively after subtraction
of a modeled point source for quasar core and fore-ground star
(Jahnke et al. 2008).
tries are a part of co S m o S. With the HST, an image of a
two square degree sized area of the sky was taken in the
I-Band with the highest possible angular resolution (0.04
arc seconds per pixel). This core data set is flanked by
X-ray images of the XMM / Newton and ch a n d r a satellites,
infrared images from Sp i t z e r, earth-bound images
in more than 30 optical and near-infrared filter bands up
to the millimeter and radio range, the latter again with
the Very Large Array under MPIA direction (led by Eva
Shinnerer), and spectroscopy with the VLT and with
Magellan.
One of numerous aspects of the co S m o S project, the
examination of quasar host galaxies is carried out principally
through X-ray and HST images of a large sample
of several hundred AGN and quasars. Fig. III.2.5 shows
several examples at redshifts between z 0.35 and
z 2. At these highest redshifts, the images reach their