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Recovery and analysis of rest-frame UV emission lines in 2052 galaxies observed with MUSE at 1.5 < z < 6.4

Schmidt, K.B.; Kerutt, J.; Wisotzki, L.; Urrutia, T.; Feltre, A.; Maseda, M.V.; Nanayakkara, T.; Bacon, R.; Boogaard, L.A.; Conseil, S.; Contini, T.; Herenz, E.C.; Kollatschny, W.; Krumpe, M.; Leclercq, F.; Mahler, G.; Matthee, J.; Mauerhofer, V.; Richard, J.; Schaye, J.

Recovery and analysis of rest-frame UV emission lines in 2052 galaxies observed with MUSE at 1.5 < z < 6.4 Thumbnail


K.B. Schmidt

J. Kerutt

L. Wisotzki

T. Urrutia

A. Feltre

M.V. Maseda

T. Nanayakkara

R. Bacon

L.A. Boogaard

S. Conseil

T. Contini

E.C. Herenz

W. Kollatschny

M. Krumpe

F. Leclercq

J. Matthee

V. Mauerhofer

J. Richard

J. Schaye


Rest-frame ultraviolet (UV) emission lines probe electron densities, gas-phase abundances, metallicities, and ionization parameters of the emitting star-forming galaxies and their environments. The strongest main UV emission line, Lyα, has been instrumental in advancing the general knowledge of galaxy formation in the early universe. However, observing Lyα emission becomes increasingly challenging at z ≳ 6 when the neutral hydrogen fraction of the circumgalactic and intergalactic media increases. Secondary weaker UV emission lines provide important alternative methods for studying galaxy properties at high redshift. We present a large sample of rest-frame UV emission line sources at intermediate redshift for calibrating and exploring the connection between secondary UV lines and the emitting galaxies’ physical properties and their Lyα emission. The sample of 2052 emission line sources with 1.5 < z < 6.4 was collected from integral field data from the MUSE-Wide and MUSE-Deep surveys taken as part of Guaranteed Time Observations. The objects were selected through untargeted source detection (i.e., no preselection of sources as in dedicated spectroscopic campaigns) in the three-dimensional MUSE data cubes. We searched optimally extracted one-dimensional spectra of the full sample for UV emission features via emission line template matching, resulting in a sample of more than 100 rest-frame UV emission line detections. We show that the detection efficiency of (non-Lyα) UV emission lines increases with survey depth, and that the emission line strength of He IIλ1640 Å, [O III] λ1661 + O III] λ1666, and [Si III] λ1883 + Si III] λ1892 correlate with the strength of [C III] λ1907 + C III] λ1909. The rest-frame equivalent width (EW0) of [C III] λ1907 + C III] λ1909 is found to be roughly 0.22 ± 0.18 of EW0(Lyα). We measured the velocity offsets of resonant emission lines with respect to systemic tracers. For C IVλ1548 + C IVλ1551 we find that ΔvC IV ≲ 250 km s−1, whereas ΔvLyα falls in the range of 250−500 km s−1 which is in agreement with previous results from the literature. The electron density ne measured from [Si III] λ1883 + Si III] λ1892 and [C III] λ1907 + C III] λ1909 line flux ratios is generally < 105 cm−3 and the gas-phase abundance is below solar at 12 + log10(O/H)≈8. Lastly, we used “PhotoIonization Model Probability Density Functions” to infer physical parameters of the full sample and individual systems based on photoionization model parameter grids and observational constraints from our UV emission line searches. This reveals that the UV line emitters generally have ionization parameter log10(U) ≈ −2.5 and metal mass fractions that scatter around Z ≈ 10−2, that is Z ≈ 0.66 Z⊙. Value-added catalogs of the full sample of MUSE objects studied in this work and a collection of UV line emitters from the literature are provided with this paper.


Schmidt, K., Kerutt, J., Wisotzki, L., Urrutia, T., Feltre, A., Maseda, M., …Schaye, J. (2021). Recovery and analysis of rest-frame UV emission lines in 2052 galaxies observed with MUSE at 1.5 < z < 6.4. Astronomy & Astrophysics, 654, Article A80.

Journal Article Type Article
Acceptance Date Jul 8, 2021
Online Publication Date Oct 15, 2021
Publication Date 2021-10
Deposit Date Jan 14, 2022
Publicly Available Date Jan 14, 2022
Journal Astronomy and astrophysics.
Print ISSN 0004-6361
Electronic ISSN 1432-0746
Publisher EDP Sciences
Peer Reviewed Peer Reviewed
Volume 654
Article Number A80


Published Journal Article (21.6 Mb)

Copyright Statement
Schmidt et al, A&A, 654, A80, 2021, reproduced with permission, © ESO.

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