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  • Science Goals

    Roland BACON



    In the following we give some examples of the science enable by the new capabilities of MUSE: formation and evolution of galaxies, stellar population in nearby galaxies, supermassive black holes, young stars and planets and small bodies. It encompasses many different objects and covers the full distant scale (from the solar system up to ten billions light-years). This is far from exhaustive, but it shows that MUSE will make breakthrough in many areas of modern astrophysics.

    Formation and evolution of galaxies

    A sample of distant galaxies
    A sample of distant galaxies
    Example of distant galaxies from the Hubble Ultra Deep Field. Credits: NASA

    One of the most important driver for the instrument design is its capabilities to find and study the progenitor of normal galaxies (i.e. similar to the Milky Way, our own Galaxy). Seen at more than 10 billions light-years distance, these galaxies are extraordinary faint and tiny and their detection is thus challenging. But, as explained in the general presentation, MUSE will be able to detect and study them thanks to their strong Hydrogen emission lines. One expect to find around 15,000 of these galaxies on the planned large (and blind) survey. The complete sample will cover all type of galaxies (giant ellipticals and spirals, active and non-active galaxies, young and old galaxies, etc.). Such a unique homogeneous set of physical data will be a key element to understand the formation and evolution of galaxies.

    Stellar populations in nearby galaxies

    The spiral galaxy NGC 300
    The spiral galaxy NGC 300
    Credits: ESO

    Galaxies are composed of billions stars. At large distance, stars cannot be resolved and galaxies appear as nebula. The light received in one single pixel (image element) of the picture is then a mixure of light comig from thousands of different stars. In this process many critical information are lost since we cannot disantangle the contribution of each single stars from the integrated light. In one single exposure MUSE shall be able to resolve many stars and to obtain up to ten thousands of spectra. Using this unique capability, we aim to study the evolution of massive stars. These stars plays a key role in galaxy evolution but little in known about them. With MUSE it will be possible to study systematically a number of nearby spiral galaxies and to increase by an order of magnitude the number of known massive stars.

    Supermassive black holes in nearby galaxies

    Most galaxies harbor a supermassive black hole in their nuclei. The strong gravitational field of these supermassive black hole has a big impact on the stellar environment. The velocities of stars in the vicinity of the black hole can be inferred from their spectra (using Doppler-Fizeau shift of spectral features). The 3D characteristics of MUSE and its high spatial resolution are ideally suited to perform these studies. Some prototype studies have shown that the motion of stars around these supermassive black holes are much more complex than expected. With MUSE we aim to develop these studies on a larger number of galaxies and to answer a number of key questions about these supermassive black holes and their impact on the galaxy evolution.

    Early stage of stellar evolution

    Protostar HH-34 in Orion
    Protostar HH-34 in Orion
    Three-colour composite of the young object Herbig-Haro 34 (HH-34). Credits: ESO

    In the early stage of their evolution, stars produce powerful jets and winds. These atomic jets are at the same time the most impressive and the most enigmatic phenomenon associated with the birth of stars. These jets of high-speed gas shooting out the pole of a forming star is the visible, and spectacular, counterpart of a complex interaction between the interstellar medium composed of cold gas and dust and the star magnetic field and expelled ionized gas. MUSE, thanks to its exquisite spatial resolution and its 3D spectrographic capabilities, will open a new dimension in the analysis and modelling of these jets and winds. Major breakthroughs will results on a number of pressing questions such as the origin of jets knots and wiggles, jet launching process, etc.

    Planets and small bodies in the Solar system

    The Hyakutake comet in 1996
    The Hyakutake comet in 1996
    Credits: NASA

    Although telescopic observations of Solar system’s planets cannot compete with direct exploration by space mission, there are a number of case where MUSE capabilities will bring new invaluable informations. Atmosphere of giant planets (Jupiter, Saturn, Neptune and Uranus) display seasonal effect. MUSE will be capable to monitor their temporal evolution. Io, one of Jupiter’s satellite, display an intense volcanic activities on its surface (due to the huge gravitational field of Jupiter). The systematic monitoring of this activity will be possible with MUSE. In the case of unpredictable and sporadic event such as the apparition of a new comet and unlike space mission which need to be programmed well in advance, MUSE shall be able to observe the object without delay. Furthermore its spectrographic 3D capabilities will be crucial to study the complex chemical and physical evolution of the comets when they approach our Sun.