[Paper Review] BlueMUSE: Project Overview and Science Cases

Johan Richard, Roland Bacon+60 more|Open Repository and Bibliography (University of Liège)|Jun 4, 2019

Galaxies: Formation, Evolution, PhenomenaPhysics and Astronomy191 references35 citations

TL;DR

BlueMUSE is a blue-optimised, wide-field IFU for the VLT that extends MUSE into 350–600 nm at R~3600, doubling the field of view and enabling a massive expansion of Galactic, Local Group, and high-redshift science in the blue/UV.

ABSTRACT

We present the concept of BlueMUSE, a blue-optimised, medium spectral resolution, panoramic integral field spectrograph based on the MUSE concept and proposed for the Very Large Telescope. With an optimised transmission down to 350 nm, a larger FoV (1.4 x 1.4 arcmin$^2$) and a higher spectral resolution compared to MUSE, BlueMUSE will open up a new range of galactic and extragalactic science cases allowed by its specific capabilities, beyond those possible with MUSE. For example a survey of massive stars in our galaxy and the Local Group will increase the known population of massive stars by a factor $>$100, to answer key questions about their evolution. Deep field observations with BlueMUSE will also significantly increase samples of Lyman-alpha emitters, spanning the era of Cosmic Noon. This will revolutionise the study of the distant Universe: allowing the intergalactic medium to be detected unambiguously in emission, enabling the study of the exchange of baryons between galaxies and their surroundings. By 2030, at a time when the focus of most of the new large facilities (ELT, JWST) will be on the infra-red, BlueMUSE will be a unique facility, outperforming any ELT instrument in the Blue/UV. It will have a strong synergy with ELT, JWST as well as ALMA, SKA, Euclid and Athena.

Motivation & Objective

• Provide an overview of the BlueMUSE instrument concept and its place in the blue/UV astronomy landscape.
• Define the key performance metrics and technical design choices that enable its science cases.
• Outline the main scientific programs enabled by BlueMUSE across the Milky Way, Local Group, nearby galaxies, and the distant Universe.

Proposed method

• Adapt the MUSE architecture to blue-optimised performance with a similar modular design.
• Employ curved detectors as a potential upgrade to increase field of view and image quality.
• Target 350–600 nm coverage at R>3000 (average ~R=3600) with 0.3 arcsec spatial sampling and 1.4 arcmin squared field.
• Maintain end-to-end throughput comparable to MUSE (including telescope and atmosphere) with >15% minimum and >25% average across the range.
• Operate in seeing-limited, panoramic IFU mode with 24x4Kx4K CCDs and a fixed spectral/spatial format to reduce risk.

Experimental results

Research questions

• RQ1 Can BlueMUSE achieve a hundreds-fold increase in massive-star spectroscopy compared to prior surveys within accessible infrastructure constraints?
• RQ2 What new insights into globular cluster multiple populations and Ultra-Faint Dwarf galaxies can be obtained from blue 350–600 nm spectroscopy with high multiplexing?
• RQ3 How does blue-wavelength spectroscopy improve measurements of ionized nebulae abundances and the O/H diagnostic via the [O III] 4363 and [O II] 3727 lines?
• RQ4 What is the impact of BlueMUSE on studying Lyman-alpha emitters and the circumgalactic/intergalactic medium at z~2–3?
• RQ5 How will BlueMUSE synergize with ELT, JWST, ALMA, SKA, Euclid, and Athena to advance a multi-wacuum approach to galaxy evolution?

Key findings

• BlueMUSE can increase the known population of massive stars by a factor over 100 in the Milky Way and Local Group.
• BlueMUSE provides spectroscopy in 350–600 nm with R ~ 3600, roughly doubling MUSE’s spectral resolution in overlapping ranges.
• The instrument samples a 1.4′×1.4′ field of view with 0.3′′ spaxels, enabling deblended spectra in crowded regions like young clusters.
• BlueMUSE enables efficient, crowding-resolved, blue-wavelength surveys that were previously impractical with fibre-based MOS instruments.
• In the distant Universe, BlueMUSE enables clean detection of the intergalactic medium in emission and improves Lyα studies near Cosmic Noon.
• Compared to the Keck KCWI, BlueMUSE offers two orders of magnitude greater efficiency due to its larger field of view and higher throughput/stability.