here - Institute for Astronomy Umleitung

Assuming that most of the black hole mass of
present-day galaxies was assembled around
the period of maximum AGN space densities,
between z ~ 1 and z ~ 3 (Wolf et al 2003), the
task is to establish an evolutionary link
between AGN at high z and the local galaxy
population. Such a link can be built by
studying the environments of AGN and
characterising the degree of overdensities they
live in. Luminous radio-loud quasars and radio
galaxies beyond z ~ 1 are typically located in
rather rich structures, probably progenitors of
the most massive clusters today
[REFERENCE]. The environment of lower
luminosity radio-quiet AGN at high z, on the
other hand, is not well constrained. A set of
MUSE pointings on a representative AGN
sample, of a few hours exposure time each,
would yield a complete census of the 100-200
kpc surroundings down to significant sub-L*
luminosities at z=1 and to roughly L* at z=3.
At the same time one would get the velocity
information needed to assess the degree of
virialisation in a given structure.
Title: Science Case
Reference: MUSE-MEM-SCI-052
Issue: 1.3
Date: 04/02/2004
Page: 43/100
Figure 2-24: This 1 arcmin x 1 arcmin section of
an HST image in the Chandra Deep Field South
contains 7 X-ray sources, most of which are likely
AGN at intermediate to high redshifts. Some of
these sources were already targeted
spectroscopically with the VLT, but are optically
too faint to give a meaningful spectrum. A single
deep MUSE exposure would not only clarify the
nature of these, but at the same time allow to
study their host galaxies and environments. Image
taken from the GEMS project.
Gravitational interaction and merging are believed by many to be the main drivers for driving
nuclear activity. But what exactly are the conditions needed to trigger an AGN? Until today,
the search for morphological clues has largely prevailed, but spectroscopic diagnostics can
deliver additional, possibly crucial pieces of evidence. A single MUSE data cube could reveal
also, for example, large-scale gas streamers, patterns of enhanced star formation in the AGN
host as well as in other galaxies in the field, and kinematical signatures of recent merger
events, thus provide essential clues about the physical drivers of cosmic AGN evolution.
Most of the sketched AGN studies would have to be performed in pointed mode, targeting
individual pre-selected objects. The "blind" MUSE surveys outlined elsewhere in this
document provide a chance to integrate the AGN aspect into a multi-purpose survey, by
judiciously selecting survey fields to coincide with deep X-ray pointings. Recent surveys with
Chandra and XMM have yielded surface densities of more than 3 X-ray sources per arcmin2,
a large fraction of which is presumably directly linked to some sort of AGN phenomenon.
These surveys are still largely photon-limited, and even deeper pointings are being considered
which would increase the surface density by at least another factor of 2 (Alexander et al
2003). The suggested concepts of "shallow" and "medium deep" MUSE surveys could in fact
revolutionise the traditional strategy of X-ray imaging/spectroscopic follow up. In particular,
spatially resolved information for every single X-ray AGN would become available at once,
allowing to deblend the nuclear from the host galaxy spectrum and obtain a much cleaner
spectral diagnostic. At the same time, kinematics and environmental information would
become available, with all the benefits mentioned.