The multi-object spectrograph (MOSAIC) for the extremely large telescope: spectroscopy of stellar populations in the milky way and external galaxies

Abstract

The project aims at the participation on the design, construction and scientific use of the MOSAIC spectrograph, to be installed at the Extremely Large Telescope (ELT), the largest optical telescope ever planned, with a mirror of 39m in diameter, being installed in Chile. The excellent quality and future impact in the brazilian astronomical instrumentation and science is at a low cost as compared with the cost of the international project. The light-gathering power of the 39m mirror of the ELT, and its spatial resolution, combined with MOSAIC, will enable to observe the large samples that will be required to follow-up targets revealed by the new even deeper imaging surveys telescopes to be available in the near-future LSST (Large Synoptic Survey Telescope), JWST (James Webb Space Telescope) and Euclid, in particular in the search and study of the first galaxies at the edge of the Universe. The follow-up will require complementary spectroscopy with high sensitivity and good spatial resolution to identify the objects and to measure their astrophysical parameters. The proposal includes our participation in a) the building of the MOSAIC spectrograph, planned to be installed at the Extremely Large Telescope (ELT) of the European Southern Observatory (ESO), and b) the science carried out by our group of spectroscopists with the present facilities, and projection of use of the MOSAIC spectrograph with in the interests of the brazilian group. MOSAIC is a fiber-fed spectrograph, covering the telescope's full field of view with several hundred fibers and a dozen integral field units with adaptive optics capability delivering milli-arcsec spatial resolution, providing spectra ranging from the blue to the near infrared (450 -- 1800 nm) at low and intermediate spectral resolution (R = 5.000, 10.000 e 20.000). The MOSAIC spectrograph will be the fastest way to spectroscopically follow-up the faintest sources, including Galactic archaeology, probing the reionisation epoch, and the first galaxies. Our group of spectroscopists expertise and interests include resolved stellar populations including the Galactic bulge, halo and disk, and Local Group dwarf galaxies, studies of extragalactic globular clusters, composite stellar populations of bulges of Local Group and Virgo cluster galaxies, HII galaxies, and high-redshift galaxies and clusters of galaxies. Finally it also includes search and studies of exoplanets. In terms of astronomical instrumentation, the participation of our group in the international project is planned to be carried out in four fronts: a) engineering of the sub-systems of positioners of optical fibers; b) specialized work on the optical fibers; c) characterization of diffraction gratings VPH, with the acquisition of two high-resolution VPH gratings; and d) design (and possible future construction) of the support structure or platform for the spectrograph, given the abilities already demonstrated by our industry and astronomical institutes. (AU)