Observations with the FMOS instrument and OH suppression at near-infrared (NIR) wavelengths is expected to explore many scientific frontiers from nearby substellar objects to large scale structure of the high redshift universe. Major scientific targets to be tackled by spectroscopic surveys with FMOS are briefly described as follows:
Brown DwarfsSpatial and mass distribution of the lowest mass stars and brown dwarfs will give clues for the understanding of initial mass function (IMF) and dark matter in the Galaxy. Nelson et al. (1993) predicted that there are more than 200 field brown dwarfs per square degree to a limiting magnitude of H = 22.5 mag. NIR spectra of these objects at high resolution (R=1500~3000) can be used for detailed spectral classification and for accurate determinations of metallicity and temperature.
Protostars and Young Stellar Objects (YSOs)In order to investigate processes and physical mechanisms of star formation, infrared observations of highly obscured objects in molecular clouds are essential. Even without intracloud absorption, a majority of YSO's spectra intrinsically peaks in the H band, and has large Pa-beta Br-gamma line ratios, so that physical information can be recovered through J and H band spectroscopy. Studies of initial mass function (IMF) in star forming regions is also an important scientific objective with FMOS.
Galactic Center RegionThe NIR coverage of FMOS allows the study of the kinematics and metallicity of stellar populations in the vicinity of the Galactic center, and the wide field of view allows current studies of the Milky Way's halo to be extended to more distant components at fainter limiting magnitudes. These data should yield powerful insights for star formation histories and formation process of the Milky Way galaxy as well as the Local Group galaxies.
Evolution of Galaxies and Large-Scale Structure at High RedshiftsA next step for studying galaxy evolution and formation with 8-m class telescopes is to probe activities of star formation in a quantitative way at redshifts z>1. At the epoch of such large redshifts, many optical lines serving as vital indicators of star formation history would be redshifted to NIR bands. In this context, multi-object spectroscopic observations with enhanced sensitivity through the OH suppression would play an important role, together with capabilities of medium resolution (a resolving power of about 400) and of a wide wavelength coverage. The spectroscopy of extremely red objects (EROs) aiming at revealing their intriguing nature is also suitable for FMOS. A systematic work of large scale structure as well as the clustering property of galaxies at higher redshift regions (z>1) could be conducted by exploiting the expected FMOS performance as described so far. The wide field of view of FMOS (30arcmin corresponds to about 10 Mpc at z=2) will allow us to study large volume (> 10^7 Mpc^3) at early epochs.
Cosmological Evolution of AGN/QSO PopulationX-ray surveys for AGNs/QSOs have just started with Chandra and XMM-Newton and will provide unbiased samples of AGNs/QSOs out to a redshift of about 5 or even larger. Multicolor surveys of high-z QSOs are also in progress or under planning. Spectroscopic follow-up observations in optical to NIR bands of these samples are indispensable in studying the nature of them, which in turn may give clues of understandings towards an obscured population of AGN/QSO and their evolution in the cosmological timescale. Large fraction of the hard X-ray selected objects is optically-faint and has red optical to near-infrared color, thus near-infrared spectroscopy is crucial to reveal the nature of them. An expected surface number density of these sources matches well with the number of fibers of the FMOS. (Mushotzky et al. 2000)
The table below summarizes the various target objects for FMOS.
|Scientific Area||Spectral Resolution||N / field||Magnitude range|
|Brown Dwarfs||High||> 200||H < 22|
|Young Stellar Objects||High||~100||H < 19.5|
|Galactic Center Region||High||> 300||H = 18|
|LSS / Galaxy Evolution||Low||>> 400||H < 22|
|AGNs / QSOs surveys||Low||~200||H < 22|
You may find further information from the FMOS Science Workshop meeting.