Astronomers using the Multi Unit Spectroscopic Explorer (MUSE) instrument on ESO’s Very Large Telescope have observed the Hubble Ultra Deep Field (HUDF), a much-studied patch of the southern constellation of Fornax. The scientists measured distances and properties of almost 1,600 very faint galaxies. The results appear in a special issue of the journal Astronomy & Astrophysics.
This color image shows the Hubble Ultra Deep Field region, as observed with the MUSE instrument on ESO’s Very Large Telescope. Image credit: ESO / MUSE HUDF Collaboration.
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, ALMA, and other telescopes, resulting in the deepest view of the Universe to date.
Now, despite the depth of the Hubble observations, MUSE has revealed 72 galaxies never seen before in this very tiny area of the sky.
“MUSE can do something that Hubble can’t — it splits up the light from every point in the image into its component colors to create a spectrum,” said MUSE HUDF Survey team leader Dr. Roland Bacon, from the Lyon Centre for Astrophysics Research in France.
“This allows us to measure the distance, colors and other properties of all the galaxies we can see — including some that are invisible to Hubble itself.”
The newly-discovered candidate galaxies, known as Lyman-alpha emitters, shine only in Lyman-alpha light.
Current understanding of star formation cannot fully explain these galaxies, which just seem to shine brightly in this one color.
Because MUSE disperses the light into its component colors 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,” said team member Dr. Jarle Brinchmann, from the University of Leiden in the Netherlands and the Institute of Astrophysics and Space Sciences at CAUP in 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.
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Roland Bacon et al. 2017. The MUSE Hubble Ultra Deep Field Survey – I. Survey description, data reduction, and source detection. A&A 608, A1; doi: 10.1051/0004-6361/201730833
H. Inami et al. 2017. The MUSE Hubble Ultra Deep Field Survey – II. Spectroscopic redshifts and comparisons to color selections of high-redshift galaxies. A&A 608, A2; doi: 10.1051/0004-6361/201731195
J. Brinchmann et al. 2017. The MUSE Hubble Ultra Deep Field Survey – III. Testing photometric redshifts to 30th magnitude. A&A 608, A3; doi: 10.1051/0004-6361/201731351
Michael V. Maseda et al. 2017. The MUSE Hubble Ultra Deep Field Survey – IV. Global properties of C III] emitters. A&A 608, A4; doi: 10.1051/0004-6361/201730985
Adrien Guérou et al. 2017. The MUSE Hubble Ultra Deep Field Survey – V. Spatially resolved stellar kinematics of galaxies at redshift 0.2 ≲ z ≲ 0.8. A&A 608, A5; doi: 10.1051/0004-6361/201730905
A.B. Drake et al. 2017. 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. A&A 608, A6; doi: 10.1051/0004-6361/201731431
Hayley Finley et al. 2017. The MUSE Hubble Ultra Deep Field Survey – VII. Fe ii* emission in star-forming galaxies. A&A 608, A7; doi: 10.1051/0004-6361/201731499
Floriane Leclercq et al. 2017. The MUSE Hubble Ultra Deep Field Survey – VIII. Extended Lyman-α haloes around high-z star-forming galaxies. A&A 608, A8; doi: 10.1051/0004-6361/201731480
E. Ventou et al. 2017. The MUSE Hubble Ultra Deep Field Survey – IX. Evolution of galaxy merger fraction since z ≈ 6. A&A 608, A9; doi: 10.1051/0004-6361/201731586
T. Hashimoto et al. 2017. The MUSE Hubble Ultra Deep Field Survey – X. Lyα equivalent widths at 2.9 < z < 6.6. A&A 608, A10; doi: 10.1051/0004-6361/201731579
