We present rest-frame Lyα equivalent widths (E W 0 ) of 417 Lyα emitters (LAEs) detected with Multi Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope (VLT) at 2.9 Ultra Deep Field. Based on the deep MUSE spectroscopy and ancillary Hubble Space Telescope (HST) photometry data, we carefully measured E W 0 values taking into account extended Lyα emission and UV continuum slopes (β ). Our LAEs reach unprecedented depths, both in Lyα luminosities and UV absolute magnitudes, from log (L Lyα /erg s-1 ) ~ 41.0 to 43.0 and from M UV ~ −16 to −21 (0.01−1.0 L * z =3 ). The E W 0 values span the range of ~ 5 to 240 A or larger, and their distribution can be well fitted by an exponential law N = N 0 exp(−E W 0 /w 0 ). Owing to the high dynamic range in M UV , we find that the scale factor, w 0 , depends on M UV in the sense that including fainter M UV objects increases w 0 , i.e., the Ando effect. The results indicate that selection functions affect the E W 0 scale factor. Taking these effects into account, we find that our w 0 values are consistent with those in the literature within 1σ uncertainties at 2.9 UV and L Lyα . Interestingly, we find 12 objects with E W 0 > 200 A above 1σ uncertainties. Two of these 12 LAEs show signatures of merger or AGN activity: the weak Civλ 1549 emission line. For the remaining 10 very large E W 0 LAEs, we find that the E W 0 values can be reproduced by young stellar ages ( ⊙ ). Otherwise, at least part of the Lyα emission in these LAEs needs to arise from anisotropic radiative transfer effects, fluorescence by hidden AGN or quasi-stellar object activity, or gravitational cooling.
We present an analysis of the spatial clustering of 695 Ly α -emitting galaxies (LAEs) in the MUSE-Wide survey. All objects have spectroscopically confirmed redshifts in the range 3.3 < z < 6. We employed the K-estimator, an alternative clustering statistic, adapted and optimized for our sample. We also explore the standard two-point correlation function approach, which is however less suited for a pencil-beam survey such as ours. The results from both approaches are consistent. We parametrize the clustering properties in two ways, (i) following the standard approach of modelling the clustering signal with a power law (PL), and (ii) adopting a halo occupation distribution (HOD) model of the two-halo term. Using the K-estimator and applying HOD modelling, we infer a large-scale bias of b HOD = 2.80 −0.38 +0.38 at a median redshift of the number of galaxy pairs ⟨ z pair ⟩ ≃ 3.82, while the best-fit power-law analysis gives b PL = 3.03 −0.52 +1.51 ( r 0 = 3.60 −0.90 +3.10 comoving h −1 Mpc and γ = 1.30 −0.45 +0.36 ). The implied typical dark matter halo (DMH) mass is log( M DMH /[ h −1 M ⊙ ]) = 11.34 −0.27 +0.23 (adopting b = b HOD and assuming σ 8 = 0.8). We study possible dependencies of the clustering signal on object properties by bisecting the sample into disjoint subsets, considering Ly α luminosity, UV absolute magnitude, Ly α equivalent width, and redshift as variables. We find no evidence for a strong dependence on the latter three variables but detect a suggestive trend of more luminous Ly α emitters clustering more strongly (thus residing in more massive DMHs) than their lower Ly α luminosity counterparts. We also compare our results to mock LAE catalogs based on a semi-analytic model of galaxy formation and find a stronger clustering signal than in our observed sample, driven by spikes in the simulated z -distributions. By adopting a galaxy-conserving model we estimate that the Ly α -bright galaxies in the MUSE-Wide survey will typically evolve into galaxies hosted by halos of log( M DMH /[ h −1 M ⊙ ]) ≈ 13.5 at redshift zero, suggesting that we observe the ancestors of present-day galaxy groups.
The physical conditions giving rise to high escape fractions of ionizing radiation (LyC $f_{\rm{esc}}$) in star-forming galaxies - most likely protagonists of cosmic reionization - are not yet fully understood. Using the VLT/MUSE observations of ~1400 Ly$\alpha$ emitters at 2.9 < z < 6.7, we compare stacked rest-frame UV spectra of candidates for LyC leakers and non-leakers selected based on their Ly$\alpha$ profiles. We find that the stacks of potential LyC leakers, i.e. galaxies with narrow, symmetric Ly$\alpha$ profiles with small peak separation, generally show (i) strong nebular OIII]1666, [SiIII]1883, and [CIII]1907+CIII]1909 emission, indicating a high-ionization state of the interstellar medium (ISM); (ii) high equivalent widths of HeII1640 (~1-3 A), suggesting the presence of hard ionizing radiation fields; (iii) SiII*1533 emission, revealing substantial amounts of neutral hydrogen off the line of sight; (iv) high CIV1548,1550 to [CIII]1907+CIII]1909 ratios (CIV/CIII] > 0.75), signalling the presence of low column density channels in the ISM. In contrast, the stacks with broad, asymmetric Ly$\alpha$ profiles with large peak separation show weak nebular emission lines, low HeII1640 equivalent widths (<1 A), and low CIV/CIII] (<0.25), implying low-ionization states and high-neutral hydrogen column densities. Our results suggest that CIV/CIII] might be sensitive to the physical conditions that govern LyC photon escape, providing a promising tool for identification of ionizing sources among star-forming galaxies in the epoch of reionization.
The Hα nebular emission line is an optimal tracer for recent star formation in galaxies. With the advent of JWST this line has recently become observable at z>3 for the first time. We present a catalog of $1,050$ Hα emitters at $3.7<z<6.7$ in the GOODS fields obtained from a blind search in JWST NIRCam/grism data. We made use of the FRESCO survey's 124 arcmin^2 of observations in GOODS-North and GOODS-South with the F444W filter, probing Hα at $4.9<z<6.7$, and the CONGRESS survey's 62 arcmin^2 of observations in GOODS-North with F356W, probing Hα at $3.8<z<5.1$. We found an overdensity with 98 sources at z∼4.4 in GOODS-N, and confirmed previously reported overdensities at z∼5.2 in GOODS-N and at z∼5.4 and z∼ 5.9 in GOODS-S. We computed the observed Hα luminosity functions (LFs) in three bins centered at z∼4.45, $5.30$, and $6.15$, which are the first such measurements at z>3 obtained based purely on spectroscopic data, robustly tracing galaxy star formation rates (SFRs) beyond the peak of the cosmic star formation history. We compared our results with theoretical predictions from three different simulations and found good agreement at z∼4-6. The UV LFs of this spectroscopically confirmed sample are in good agreement with pre- JWST measurements obtained with photometrically selected objects. Finally, we derived SFR functions and integrated them to compute the evolution of the cosmic SFR densities across z∼4-6, finding values in good agreement with recent UV estimates from Lyman-break galaxies, which imply a continuous decrease in SFR density by a factor of three over z∼4 to z∼6. Our work shows the power of NIRCam grism observations to efficiently provide new tests for early galaxy formation models based on emission line statistics.
We present rest-frame Ly$\alpha$ equivalent widths (EW) of 417 Ly$\alpha$ emitters (LAEs) detected with Multi Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope (VLT) at $2.9 200$ A above $1\sigma$ uncertainties. Two of these 12 LAEs show signatures of merger or AGN activity: the weak CIV $\lambda 1549$ emission line. For the remaining 10 very large EW LAEs, we find that the EW values can be reproduced by young stellar ages ($< 100$ Myr) and low metallicities ($\lesssim 0.02$ $Z_{\rm \odot}$). Otherwise, at least part of the Ly$\alpha$ emission in these LAEs needs to arise from anisotropic radiative transfer effects, fluorescence by hidden AGN or quasi-stellar object activity, or gravitational cooling.
The H{\alpha} nebular emission line is an optimal tracer for recent star formation in galaxies. With the advent of JWST, this line has recently become observable at z>3 for the first time. We present a catalog of 1013 H{\alpha} emitters at 3.73 obtained based purely on spectroscopic data, robustly tracing galaxy star formation rates (SFRs) beyond the peak of the cosmic star formation history. We compare our results with theoretical predictions from three different simulations and find good agreement at z~4-6. The UV LFs of this spectroscopically-confirmed sample are in good agreement with pre-JWST measurements obtained with photometrically-selected objects. Finally, we derive SFR functions and integrate these to compute the evolution of the cosmic star-formation rate densities across z~4-6, finding values in good agreement with recent UV estimates from Lyman-break galaxies, which imply a continuous decrease in SFR density by a factor of 3x over z~4 to z~6. Our work shows the power of NIRCam grism observations to efficiently provide new tests for early galaxy formation models based on emission line statistics.
Using the exquisite data from the MUSE eXtremely Deep Field (MXDF), we report the discovery of an Mg II emission nebula with an area above a 2 σ significance level of 1000 proper kpc 2 . This provides the first panoramic view of the spatial distribution of magnesium in the intragroup medium of a low-mass group of five star-forming galaxies at z = 1.31. The galaxy group members are separated by less than 50 physical kpc in projection and ≈120 km s −1 in velocity space. The most massive galaxy has a stellar mass of 10 9.35 M ⊙ and shows an Mg II P-Cygni line profile, indicating the presence of an outflow, which is consistent with the spatially resolved spectral analysis showing ≈+120 km s −1 shift of the Mg II emission lines with respect to the systemic redshift. The other galaxies are less massive and only show Mg II in emission. The detected Mg II nebula has a maximal projected extent of ≈70 kpc, including a low-surface-brightness (≈2 × 10 −19 erg s −1 cm −2 arcsec −2 ) gaseous bridge between two subgroups of galaxies. The presence of absorption features in the spectrum of a background galaxy located at an impact parameter of 19 kpc from the closest galaxy of the group indicates the presence of gas enriched in magnesium even beyond the detected nebula seen in emission, which suggests that we are observing the tip of a larger intragroup medium. The observed Mg II velocity gradient suggests an overall rotation of the structure along the major axis of the most massive galaxy. Our MUSE data also reveal extended Fe II * emission in the vicinity of the most massive galaxy, aligned with its minor axis and pointing towards a neighboring galaxy. Extended [O II ] emission is found around the galaxy group members and at the location of the Mg II bridge. Our results suggest that both tidal stripping effects from galaxy interactions and outflows are enriching the intragroup medium of this system.
