Science Case Study
The prime driver for the ARGOS ground layer adaptive optics system is
to greatly enhance the science that can be done on existing facility
instruments, and in particular with LUCIFER. It will enable this by
improving the resolution and sensitivity for both imaging and
multi-object spectroscopy over a very wide field of view. In
particular, the combination of GLAO with a wide field MOS will be a
The direct benefits to the LBT are afforded by the
factor of 2-3
improvement in the spatial resolution. Indeed, ARGOS can be considered
as a ‘seeing enhancer’ for the existing facility
enables one to address much more of the primary science that has been
identified in their respective science cases.
This is because:
- observations can be done much faster, saving a
significant amount of observing time.
- demanding science programmes, that would normally
require the best
seeing conditions, can instead be carried out during most nights.
science case study addresses these issues in greater detail. It
describes the gains that can be achieved with GLAO; and the
requirements on the design are justified. It summarises the
spectrum of science that it enables one to address. A specific detailed
comparison is given for a highlight science case: the Dynamics and
Stellar populations in high redshift galaxies.
Questions ranked around this topic are:
- How did galaxies assemble over time, and what is the
role of mergers?
- How did galaxies grow their stellar mass?
- How did galaxies acquire their morphology and how did
the hubble sequence arise?
- How did galaxies get their angular momentum?
of NGC4945 taken with LGSAO at the VLT. This galaxy is at
a distance of about 4Mpc and yet in this image it is possible to
resolve individual stars. The data have a resolution of about
similar to that which will be achievable with LGS-GLAO on the LBT in
good conditions; but the field is much smaller, only
comparison to the 240”x240” available with LUCIFER.
In order to answer these fundamental questions, robust measures are
needed for mass, age, star formation rate, gas-phase metallicity and
ionization state, dust obscuration, sizes, and morphologies
for complete samples of z ~ 1 – 4 galaxies. This epoch is
crucial as it corresponds to the peak of (dust-enshrouded)
star formation and quasar activity, as well as the assembly of
a significant fraction of the present-day galaxies. Spectroscopic
investigations at z ~ 1 – 4 are however
still challenging since the key spectral diagnostics
(Hα, Hβ, [NII], [OIII], [OII], [SII] emission lines,
continuum emission, stellar absorption features, and
Balmer/4000Å breaks) that are emitted in the
rest-frame optical are redshifted to the near-IR, between 1 and
2.5μm. Due to the technological challenges to
build multiplexed near-IR cryogenic spectrographs there is a
lack of such capabilities on 8m-class telescopes. LUCIFER will
therefore play a very important role in answering the above
key scientific questions. This highlight science case is accomplished
by a numb er of short science cases contributed by the LBT
community illustrating the breadth of science that can be
addressed with the GLAO system. These include a mixture of cases, some
of which require specifically GLAO for the science itself; and others
which require AO over a smaller field, but still make use of the wide
field GLAO capability in order to measure the corrected PSF. In
all cases, the improved resolution enables a better scientific
analysis and interpretation, and yields gains in observing time of a
factor of 4-9.
Additionally the science case study outlines the gains in science
capability with GLAO, as:
- Increased point source sensitivity
- Increased slit coupling efficiency
- Reduced crowding noise
- Enhanced spatial resolution
The science case study as well contains a detailed comparison with the
spectroscopic capabilities of JWST and ground based facilities. While
ARGOS and LUCIFER are not expected to compete effectively with
JWST, either in terms of resolution or sensitivity, the simulation
results show that ARGOS will make the LBT spectroscopically
competitive with JWST between the OH lines and at wavelength shorter
2.2 μm. In comparison with other existing or planned facilities,
there are several strong competitors to LUCIFER and its wide
field MOS. ARGOS therefore will be a crucial enhancement to LUCIFER to
give it the edge over other instruments.
© Infrared and Submillimeter Astronomy Group at MPE
03/02/2009, editor of this page: Julian Ziegleder