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EMIR Science Programs
EMIR addresses the core observing goals of
a 10-m class telescope by providing multi-object near-IR spectroscopy of faint sources. Typical
targets will be faint galaxies, low-mass stars, brown dwarfs, distant supernovae, stellar
populations in resolved external galaxies, HII regions and objects in dust obscured regions:
galactic nuclei, young stellar objects and edge-on galaxies. Some representative examples of
scientific projects that are ideally suited for
EMIR are:
EMIR is ideally suited for a wide
variety of scientific projects instellar, galactic, and extragalactic astronomy, including:
Brown dwarfs have recently been
unambiguously identified. The current data suggest that they may be a common constituent of
open clusters and also abundant in the field. Surveys of brown dwarfs will allow to
investigate the IMF at extremely low masses thus helping to understand the largely unknown
processes of star formation at the faint end of the IMF. The most massive brown dwarfs are
quite red, i.e., I-K > 3, and on the basis of evolutionary models, much redder colors are
expected for intermediate- and low-mass brown dwarfs. This implies an easier detectability in
the near-IR than at optical wavelengths. Typical spectral resolutions of 5000 are excellent
in order to disentangle a number of molecular and atomic features. Due to the intrinsic low
luminosities, large telescopes are needed.
Molecular clouds hold the key
for the process of star-formation: we believe they are the cradle of normal stars. But
molecular clouds are usually dense regions of high dust obscuration with a visual extinction
of 5-20 magnitudes. Infrared imaging can be best used to penetrate through these heavily
obscured regions and detect embedded objects such as T-Tauri stars.
EMIR is ideal for a follow-up
spectroscopic study of these objects.
Preliminary studies of the CO absorption
band at 2.3 microns indicate a great sensitivity to both stellar effective temperature and
gravity, making this feature a powerful tool to determine both the age of starburst galaxies
and the stellar population properties of elliptical galaxies (i.e., metallicities, and
giant-to-dwarf stellar ratios). A first step to use this feature is its empirical
calibration as a function of the main stellar parameters using a proper stellar library
(see Gorgas et al., 1998, in prep.). CO surveys of nearby giant ellipticals are currently
being undertaken using 4m-class telescopes (e.g., Guzmán & Mobasher 1998).
EMIR is the ideal instrument to extend
these surveys to dwarf ellipticals in nearby clusters.
EMIR will have a major impact on the field
of Active Galactic Nuclei (AGN) and the environment of AGN. In the local universe, the
fraction of AGN occurrence among galaxies (estimated to be as high as 35% according to Ho
et al., 1997, ApJ 487, 568) can be extensively explored from mostly unextincted, high-S/N
near-IR spectral features such as the coronal [Si IV] 11.962 mm and the broad
Brg emission lines. The content of young stars around the nuclei,
relevant to the starburst-AGN connection, will be evaluated through observations of
Brg emission and the photospheric Si 11.59 microns and CO 2.3
microns absorption in nearby galaxies harbouring AGN. At high redshifts, a multi-object
spectrograph like EMIR will most
efficiently determine what fraction of the observed excess of red faint galaxies in the
environments of QSOs (and Radio Galaxies) are cluster members and/or lensed objects.
This not only will allow to determine the nature of the lower-z intervening galaxies in the
line of sight of the QSO (DLA, Mg or C absorbers), but it can also be a powerful technique
to study normal galaxies at the same cosmic age as that of the highest redshift QSOs.
Finally, the search for classical rest-frame optical stellar features and scattered emission
lines off-nucleus in the near-IR will solve the controversy about the nature of the high
luminosities encountered in normal QSO hosts at high-z (Aretxaga et al., 1998, MNRAS,
296, 643).
EMIR is ideal to undertake the
spectroscopic follow-up of all-sky surveys. For instance, AXAF (Advanced X-ray Astrophysics
Facility) is expected to detect QSOs and active galaxies 100 times fainter than the
Einstein satellite did. IR spectroscopy of the most distant sources will be essential for
resolving the question of the origin of the extragalactic X-ray background and to determine
the relative contribution of QSOs, AGN and starburst galaxies. Similarly, ELAIS
(European Large Area ISO Survey) is expected to identify several thousand extra-galactic
sources in the range 2.5-240 mm, including a high redshift population of objects most likely
dominated by starburst and Seyfert galaxies which will require ground-based follow-up
spectroscopy in the near-IR.
The evolution of clusters
of galaxies remains poorly known beyond z=0.5.
EMIR will allow observations of a
large number of clusters to establish unambiguously cluster membership and study: i)
the evolution of the comoving cluster density, of fundamental importance to constrain
cosmological models; ii) the evolution of dynamical properties (i.e., the assembly of clusters
versus time); and iii) the evolution of cluster galaxies in a high density environment to
be compared with the evolution of field galaxies.
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