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  • MOSAIC : THE CONSORTIUM

  • MOSAIC : THE INSTRUMENT

  • MOSAIC : THE SCIENCE

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On March 18, 2016, during the MOSAIC kick-off meeting at the Paris Observatory in the presence of the team(*) led by François Hammer, The European Southern Observatory has signed a phase A study contract with the MOSAIC consortium. The multi-object spectrograph will be the workhorse instrument for the ELT, being the biggest telescope in the world with its 39m diameter primary mirror.

MOSAIC will be the world-leading MOS facility, contributing to all fields of contemporary astronomy, from extra-solar planets, to the study of the halo of the Milky Way and its satellites, and from resolved stellar populations in nearby galaxies out to observations of the earliest ‘first-light’ structures in the Universe.

The ESO contract has been signed by the CNRS-INSU (Leading Institute of the MOSAIC Consortium). The Consortium includes five Leading Countries

  • France,
  • United Kingdom,
  • The Netherlands,
  • Brazil,
  • Germany,

and six Associated Partners

  • Austria,
  • Finland,
  • Italy,
  • Portugal,
  • Spain,
  • Sweden

 

   At blue wavelengths, MOSAIC will be able to get a spectrum of a V = 25 mag galaxy with S/N ~ 5 (resolution R=5000) in a ~ 4 hour exposure with the HMM-VIS mode.

 

Simulations

Detailed simulations have been performed to assess the performance of the blue part of the visible spectrograph. To this end, we used the WEBSIM-COMPASS simulator. Our study aimed to understand the behavior of noise, the effects of sky variability, and the scaling between signal-to-noise (S/N) and several other observational (exposure time) and instrumental (resolution R, throughput T%) characteristics. Briefly, an astrophysical target was modeled as a high-resolution data cube, which was subsequently convolved with the point-spread function (PSF) that represented the optical path through the atmosphere and the telescope, including the adaptive optics system. Realistic sky background, photon noise, and detector noise were added. The simulator produced a data cube which we analyzed as if it were real data.

in and beyond the Local Group


Observations of resolved stellar populations with MOSAIC will enable us to trace and explore the star-formation and chemical-enrichment histories of large samples of galaxies. With current facilities, detailed spectroscopic observations of individual stars are limited to the Milky Way and its nearest neighbours, but reaching beyond the Local Group is essential in order to advance our understanding of how galaxies form and evolve under very different environmental conditions. MOSAIC will allow us, for the first time, to move to a broader range of galaxies in the Local Volume, from the edge of the Local Group out to Mpc distances, and to reach the faintest populations within the Milky Way.  

The intergalactic medium (IGM) of the modern Universe is fully ionized, and maintained in this state by the integrated ultraviolet (UV) emission from stars and Active Galactic Nuclei (AGN). The epoch of reionization (EoR; z>6) marks the point at which this phase transition occurred, and is a key period in cosmic history. Exactly how reionisation occurred is still a debated topic in modern astrophysics.
MOSAIC will allow unique massive scale spectroscopic surveys of thousands of galaxies at z>6, efficiently extending the spectroscopic frontier to fainter, ‘ordinary’ galaxies. MOSAIC will perform critical rest UV observations of the earliest galaxies, providing measurements to complete panchromatic spectral surveys together with JWST, Euclid, and Roman. MOSAIC’s high-resolution gratings and large multiplexing+multi-IFU modes make it the only instrument solution able to efficiently characterize the EoR galaxy population in the UV.

Mosaic will combine both visible and near-IR observations to conduct the first direct inventory of matter in distant galaxies at z~3, including characterising the dark matter profiles in disk galaxies, the distribution of neutral gas in the IGM, and probing all gas phases in the CGM.

  1. Mapping the intergalactic medium

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