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

Abstract

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 &lt; z &lt; 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 &lt; 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.

The MUSE-Wide survey: Three-dimensional clustering analysis of Lyman-α emitters at 3.3 < z < 6

“…While the formal average accuracy of our redshifts is ∆z 0.0007 or ±41 km s −1 (limited by the accuracy of fitting the line), it is well-known that Lyα peak redshifts are typically offset by up to several hundreds of km s −1 from systemic ones (e.g. Hashimoto et al 2015;Muzahid et al 2020;Schmidt et al 2021), which would introduce a systematic error in the redshiftderived 3D positions of the LAEs along the line-of-sight (LOS) of the order of ∼3 Mpc. We mitigate this systematic uncertainty by applying a correction to the Lyα redshifts following the two recipes described in Verhamme et al (2018): When the Lyα line presents two peaks with the red peak larger than the blue peak, we apply Eq.…”

Strong Lyman continuum emitting galaxies show intense CIV 1550 emission

“…The stacked rest-UV spectrum of lensed sources with median z = 3.2 and median M 1500 = −17.1 from Vanzella et al (2021) shows strong nebular C iv λ1550, C iii] λ1909, and numerous other emission lines. The C iv line in several of these sources is strong, with EWs of up to EW(C iv) = 38 ± 16 Å in A1703-zd6 (Stark et al 2015;Schmidt et al 2021) and C43 > 0.8 in several of them. Our results suggest that these sources are strong LyC emitters, which is overall in agreement with the other observational properties they share with LyC emitters (e.g., strong Lyα emission).…”

The MUSE eXtremely deep field: first panoramic view of an Mg II emitting intragroup medium

“…The MXDF source catalog (Bacon et al, in prep.) consists of (i) sources blindly detected and extracted using the ORIGIN software (Mary et al 2020) which is designed to detect emission lines in 3D data sets and (ii) sources extracted using the ODHIN software (Bacher 2017) based on an HST catalog (Rafelski et al 2015), which performs source deblending in MUSE using high resolution HST images. The ODHIN approach is similar to TDOSE (Schmidt et al 2019) developed for the MUSE wide survey (Urrutia et al 2019;Schmidt et al 2021) with the differences that it is non-parametric, it uses multiple broadband HST images, and it implements a regularization process to avoid noise amplification for very close sources. The sources are then inspected by three experts and a final catalog of 733 sources with redshift and associated confidence is created.…”