Press Release

MUSE Probes Uncharted Depths of Hubble Ultra Deep Field

Deepest ever spectroscopic survey completed

29 November 2017

Astronomers using the MUSE instrument on ESO’s Very Large Telescope in Chile have conducted the deepest spectroscopic survey ever. They focused on the Hubble Ultra Deep Field, measuring distances and properties of 1600 very faint galaxies including 72 galaxies that have never been detected before, even by Hubble itself. This groundbreaking dataset has already resulted in 10 science papers that are being published in a special issue of Astronomy & Astrophysics. This wealth of new information is giving astronomers insight into star formation in the early Universe, and allows them to study the motions and other properties of early galaxies — made possible by MUSE’s unique spectroscopic capabilities.

The MUSE HUDF Survey team, led by Roland Bacon of the Centre de recherche astrophysique de Lyon (CNRS/Université Claude Bernard Lyon 1/ENS de Lyon), France, used MUSE (Multi Unit Spectroscopic Explorer) to observe the Hubble Ultra Deep Field (heic0406), a much-studied patch of the southern constellation of Fornax (The Furnace). This resulted in the deepest spectroscopic observations ever made; precise spectroscopic information was measured for 1600 galaxies, ten times as many galaxies as has been painstakingly obtained in this field over the last decade by ground-based telescopes.

The original HUDF images were pioneering deep-field observations with the NASA/ESA Hubble Space Telescope published in 2004. They probed more deeply than ever before and revealed a menagerie of galaxies dating back to less than a billion years after the Big Bang. The area was subsequently observed many times by Hubble and other telescopes, resulting in the deepest view of the Universe to date [1]. Now, despite the depth of the Hubble observations, MUSE has — among many other results — revealed 72 galaxies never seen before in this very tiny area of the sky.

Roland Bacon takes up the story: “MUSE can do something that Hubble can’t — it splits up the light from every point in the image into its component colours to create a spectrum. This allows us to measure the distance, colours and other properties of all the galaxies we can see — including some that are invisible to Hubble itself.”

The MUSE data provides a new view of dim, very distant galaxies, seen near the beginning of the Universe about 13 billion years ago. It has detected galaxies 100 times fainter than in previous surveys, adding to an already richly observed field and deepening our understanding of galaxies across the ages.

The survey unearthed 72 candidate galaxies known as Lyman-alpha emitters that shine only in Lyman-alpha light [2]. Current understanding of star formation cannot fully explain these galaxies, which just seem to shine brightly in this one colour. Because MUSE disperses the light into its component colours these objects become apparent, but they remain invisible in deep direct images such as those from Hubble.

“MUSE has the unique ability to extract information about some of the earliest galaxies in the Universe — even in a part of the sky that is already very well studied,” explains Jarle Brinchmann, lead author of one of the papers describing results from this survey, from the University of Leiden in the Netherlands and the Institute of Astrophysics and Space Sciences at CAUP in Porto, Portugal. “We learn things about these galaxies that is only possible with spectroscopy, such as chemical content and internal motions — not galaxy by galaxy but all at once for all the galaxies!”

Another major finding of this study was the systematic detection of luminous hydrogen halos around galaxies in the early Universe, giving astronomers a new and promising way to study how material flows in and out of early galaxies.

Many other potential applications of this dataset are explored in the series of papers, and they include studying the role of faint galaxies during cosmic reionisation, measuring galaxy merger rates when the Universe was young, galactic winds, star formation as well as mapping the motions of stars in the early Universe.

“Remarkably, these data were all taken without the use of MUSE’s recent Adaptive Optics Facility upgrade. The activation of the AOF after a decade of intensive work by ESO’s astronomers and engineers promises yet more revolutionary data in the future,” concludes Roland Bacon [3].

Notes

[1] The Hubble Ultra Deep Field is one of the most extensively studied areas of space. To date, 13 instruments on eight telescopes, including the ESO-partnered ALMA (eso1633), have observed the field from X-ray to radio wavelengths.

[2] The negatively-charged electrons that orbit the positively-charged nucleus in an atom have quantised energy levels. That is, they can only exist in specific energy states, and they can only transition between them by gaining or losing precise amounts of energy. Lyman-alpha radiation is produced when electrons in hydrogen atoms drop from the second-lowest to the lowest energy level. The precise amount of energy lost is released as light with a particular wavelength in the ultraviolet part of the spectrum, which astronomers can detect with space telescopes or on Earth in the case of redshifted objects. For this data, at redshift of z ~ 3–6.6, the Lyman-alpha light is seen as visible or near-infrared light.

[3] The Adaptive Optics Facility with MUSE has already revealed previously unseen rings around the planetary nebula IC 4406 (eso1724).

More information

This research was presented in a series of 10 papers to appear in the journal Astronomy & Astrophysics.

The teams are composed of Roland Bacon (CRAL - CNRS, Université Claude Bernard Lyon 1, ENS de Lyon, Université de Lyon, Lyon, France), Hanae Inami (CRAL - CNRS, Université Claude Bernard Lyon 1, ENS de Lyon, Université de Lyon, Lyon, France), Jarle Brinchmann (Leiden Observatory, Leiden, the Netherlands; Instituto de Astrofísica e Ciências do Espaço, Porto, Portugal), Michael Maseda (Leiden Observatory, Leiden, the Netherlands), Adrien Guerou (IRAP, CNRS, Université Toulouse III – Paul Sabatier, CNES, Université de Toulouse, France; ESO, Garching, Germany), A. B. Drake (CRAL - CNRS, Université Claude Bernard Lyon 1, ENS de Lyon, Université de Lyon, Lyon, France), H. Finley (IRAP, Université de Toulouse, Toulouse, France), F. Leclercq (University of Lyon, Lyon, France), E. Ventou (IRAP, CNRS, Université Toulouse III – Paul Sabatier, CNES Université de Toulouse, Toulouse, France), T. Hashimoto (University of Lyon, Lyon, France), Simon Conseil (CRAL - CNRS, Université Claude Bernard Lyon 1, ENS de Lyon Université de Lyon, Lyon, France), David Mary (Laboratoire Lagrange, CNRS, Observatoire de la Côte d’Azur, Université de Nice, Nice, France), Martin Shepherd (University of Lyon, Lyon, France), Mohammad Akhlaghi (CRAL - CNRS, Université Claude Bernard Lyon 1, ENS de Lyon Université de Lyon, Lyon, France), Peter M. Weilbacher (Leibniz-Institut für Astrophysik Postdam, Postdam, Germany), Laure Piqueras (CRAL - CNRS, Université Claude Bernard Lyon 1, ENS de Lyon Université de Lyon, Lyon, France), Lutz Wisotzki (Leibniz-Institut für Astrophysik Potsdam, Potsdam, Germany), David Lagattuta (CRAL - CNRS, Université Claude Bernard Lyon 1, ENS de Lyon Université de Lyon, Lyon, France), Benoit Epinat (IRAP, CNRS, Université Toulouse III – Paul Sabatier, CNES, Université de Toulouse, Toulouse, France; and LAM, CNRS / Aix Marseille Université, Marseille, France), Sebastiano Cantalupo (ETH Zurich, Zurich, Switzerland), Jean Baptiste Courbot (University of Lyon, Lyon, France; ICube, Université de Strasbourg, Strasbourg, France), Thierry Contini (IRAP, CNRS, Université Toulouse III – Paul Sabatier, CNES Université de Toulouse, Toulouse, France), Johan Richard (CRAL - CNRS, Université Claude Bernard Lyon 1, ENS de Lyon Université de Lyon, Lyon, France), Rychard Bouwens (Leiden Observatory, Leiden, the Netherlands), Nicolas Bouché (IRAP, CNRS, Université Toulouse III – Paul Sabatier, CNES Université de Toulouse, Toulouse, France), Wolfram Kollatschny (AIG, Universität Göttingen, Göttingen, Germany), Joop Schaye (Leiden Observatory, Leiden, the Netherlands), Raffaella Anna Marino (ETH Zurich, Zurich, Switzerland), Roser Pello (IRAP, CNRS, Université Toulouse III – Paul Sabatier, CNES Université de Toulouse, Toulouse, France), Bruno Guiderdoni (CRAL - CNRS, Université Claude Bernard Lyon 1, ENS de Lyon Université de Lyon, Lyon, France), Marcella Carollo (ETH Zurich, Zurich, Switzerland), S. Hamer (University of Lyon, Lyon, France), B. Clément (University of Lyon, Lyon, France), G. Desprez (University of Lyon, Lyon, France), L. Michel-Dansac (CRAL - CNRS, Université Claude Bernard Lyon 1, ENS de Lyon Université de Lyon, Lyon, France), M. Paalvast (Leiden Observatory, Leiden, the Netherlands), L. Tresse (CRAL - CNRS, Université Claude Bernard Lyon 1, ENS de Lyon Université de Lyon, Lyon, France), L. A. Boogaard (Leiden Observatory, Leiden, the Netherlands), J. Chevallard (Scientific Support Office, ESA/ESTEC, Noordwijk, the Netherlands) S. Charlot (Sorbonne University, Paris, France), J. Verhamme (University of Lyon, Lyon, France), Marijn Franx (Leiden Observatory, Leiden, the Netherlands), Kasper B. Schmidt (Leibniz-Institut für Astrophysik Potsdam, Potsdam, Germany), Anna Feltre (CRAL - CNRS, Université Claude Bernard Lyon 1, ENS de Lyon Université de Lyon, Lyon, France), Davor Krajnović (Leibniz-Institut für Astrophysik Potsdam, Potsdam, Germany), Eric Emsellem (ESO, Garching, Germany; University of Lyon, Lyon, France), Mark den Brok (ETH Zurich, Zurich, Switzerland), Santiago Erroz-Ferrer (ETH Zurich, Zurich, Switzerland), Peter Mitchell (CRAL - CNRS, Université Claude Bernard Lyon 1, ENS de Lyon Université de Lyon, Lyon, France), Thibault Garel (University of Lyon, Lyon, France), Jeremy Blaizot (CRAL - CNRS, Université Claude Bernard Lyon 1, ENS de Lyon Université de Lyon, Lyon, France), Edmund Christian Herenz (Department of Astronomy, Stockholm University, Stockholm, Sweden), D. Lam (Leiden University, Leiden, the Netherlands), M. Steinmetz (Leibniz-Institut für Astrophysik Potsdam, Potsdam, Germany) and J. Lewis (University of Lyon, Lyon, France).

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Links

• MUSE HUDF Special Issue in A&A
• “The MUSE Hubble Ultra Deep Field Survey: I. Survey description, data reduction and source detection” by R. Bacon et al.
• “The MUSE Hubble Ultra Deep Field Survey: II. Spectroscopic Redshift and Line Flux Catalog, and Comparisons to Color Selections of Galaxies at 3 < z < 7” by H. Inami et al.
• “The MUSE Hubble Ultra Deep Field Survey: III. Testing photometric redshifts to 30th magnitude” by J. Brinchmann et al.
• “The MUSE Hubble Ultra Deep Field Survey: IV. An Overview of C III] Emitters” by M. V. Maseda et al.
• “The MUSE Hubble Ultra Deep Field Survey: V. Spatially resolved stellar kinematics of galaxies at redshift 0.2 ≲ z ≲ 0.8” b A. Guérou
• “The MUSE Hubble Ultra Deep Field Survey: VI. The Faint-End of the Lyα Luminosity Function at 2.91 < z < 6.64 and Implications for Reionisation” by A. B. Drake et al.
• “The MUSE Hubble Ultra Deep Field Survey:VII. Fe II* Emission in Star-Forming Galaxies” by H. Finley et al.
• “The MUSE Hubble Ultra Deep Field Survey: VIII. Extended Lyman α haloes” by F. Leclercq et al.
• “The MUSE Hubble Ultra Deep Field Survey: IX. evolution of galaxy merger fraction up to z ≈ 6” by E. Ventou et al.
• “The MUSE Hubble Ultra Deep Field Survey: X. Lyα Equivalent Widths at 2.9 < z < 6.6” by T. Hashimoto et al.
• MUSE
• MUSE and the Adaptive Optics Facility (eso1724)

Contacts

Roland Bacon
Lyon Centre for Astrophysics Research (CRAL)
France
Cell: +33 6 08 9 14 27
Email: roland.bacon@univ-lyon1.fr

Jarle Brinchmann
University of Leiden
Netherlands
Cell: +31 6 50 92 51 89
Email: jarle@strw.leidenuniv.nl

Davor Krajnovic
Leibniz Institute for Astrophysics Potsdam
Germany
Cell: +49 160 24 34 574
Email: dkrajnovic@aip.de

Thierry Contini
Institut de Recherche en Astrophysique et Planétologie
France
Cell: +33 6 62 64 12 68
Email: thierry.contini@irap.omp.eu

Richard Hook
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org

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