here - Institute for Astronomy Umleitung

Title: Science Case
Reference: MUSE-MEM-SCI-052
Issue: 1.3
Date: 04/02/2004
Page: 42/100
lower metallicities, for truly primordial objects, the HeII 1640 line is favoured relative to Ly α
(see Figure 2-21); for some assumed IMF, the HeII 1640 line luminosity could reach 4.10 41
erg.s -1 at zero metallicity, corresponding to a flux of 3.10 -18 erg.s -1 .cm -2 , at z=5. Such a line
would be easily detectable in the MUSE deep field. Finally, the MUSE ultra deep field
described in section 6 (using gravitational amplification by a factor 3 in average), with its
enhanced detection limit of 8.10 -20 erg.s -1 .cm -2 , should be able to detect simultaneously Ly α
and HeII lines in the 2.8-4.7 redshift range for a metallicity lower than 10 -5 solar.
Based on the models of Scanapieco et al (2003), the fraction of Ly α emitters that are Pop III
objects could under certain scenarios be as high as 10% at z ~ 5 and L Lyα ~ 10 43 erg s -1 cm -2 .
The point is that this is highly model dependent, and the detection of such objects (which is
quite plausible) would greatly add to our understanding of the early chemical enrichment of
the Universe.
References
Scanapieco, E., Schneider, R., Ferrara, A., astro-ph/0301628.
Schaerer, D., 2002, A&A, 382, 28
Schaerer, D., 2003, A&A, 397, 527
Tumlinson, J., Giroux, M.L., Shull, J.M., 2001, ApJ, 550, L1
Tumlinson, J., Shull, J. M., Venkatesan, A.: 2003, ApJ, 584, 608
2.10. Active galactic nuclei at intermediate and high redshifts
In a dramatic change of paradigm over the last years, active galactic nuclei (AGN) have
altered their status from interesting but somewhat exotic objects into fundamental components
of galaxy formation and evolution. This change was mainly triggered by the recognition that
supermassive black hole (SMBHs) are ubiquitous in massive galaxies (Magorrian et al 1998).
The striking near-equality between the local black hole mass density and the total density of
matter accumulated through accretion in AGN (Yu & Tremaine 2002) suggests that periods of
nuclear activity may in fact be common phases within galaxy evolution. An intricate link
exists between black hole growth, the formation of galaxy bulges, and nuclear activity cycles;
but most details are still missing from this picture.
This is a challenge to theory and observers alike. In particular, the host galaxy and
environmental properties of AGN at redshifts around and beyond z~1 will allow one to set
strong constraints on formation scenarios. This is an area where MUSE will provide
significant progress, because of its capability to reach very faint flux levels at good spectral
resolution, combined with a high multiplex factor over an astrophysically relevant field size
of ~ 250 kpc. A fundamental advantage of MUSE over existing or other planned instruments
is the integration of the traditional multi-stepped approach of imaging, low-resolution and
high-resolution spectroscopy into a single observation.