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Abstract A bright (m_F150W,AB= 24 mag),z= 1.95 supernova (SN) candidate was discovered in JWST/NIRCam imaging acquired on 2023 November 17. The SN is quintuply imaged as a result of strong gravitational lensing by a foreground galaxy cluster, detected in three locations, and remarkably is the second lensed SN found in the same host galaxy. The previous lensed SN was called “Requiem,” and therefore the new SN is named “Encore.” This makes the MACS J0138.0−2155 cluster the first known system to produce more than one multiply imaged SN. Moreover, both SN Requiem and SN Encore are Type Ia SNe (SNe Ia), making this the most distant case of a galaxy hosting two SNe Ia. Using parametric host fitting, we determine the probability of detecting two SNe Ia in this host galaxy over a ∼10 yr window to be ≈3%. These observations have the potential to yield a Hubble constant (H₀) measurement with ∼10% precision, only the third lensed SN capable of such a result, using the three visible images of the SN. Both SN Requiem and SN Encore have a fourth image that is expected to appear within a few years of ∼2030, providing an unprecedented baseline for time-delay cosmography. 

Utilizing spectroscopic observations taken for the VIMOS Ultra-Deep Survey (VUDS), new observations from Keck/DEIMOS, and publicly available observations of large samples of star-forming galaxies, we report here on the relationship between the star-formation rate (SFR) and the local environment ( δ gal ) of galaxies in the early universe (2 <  z  < 5). Unlike what is observed at lower redshifts ( z  ≲ 2), we observe a definite, nearly monotonic increase in the average SFR with increasing galaxy overdensity over more than an order of magnitude in δ gal . The robustness of this trend is quantified by accounting for both uncertainties in our measurements and galaxy populations that are either underrepresented or not present in our sample (e.g., extremely dusty star-forming and quiescent galaxies), and we find that the trend remains significant under all circumstances. This trend appears to be primarily driven by the fractional increase of galaxies in high-density environments that are more massive in their stellar content and are forming stars at a higher rate than their less massive counterparts. We find that, even after stellar mass effects are accounted for, there remains a weak but significant SFR– δ gal trend in our sample implying that additional environmentally related processes are helping to drive this trend. We also find clear evidence that the average SFR of galaxies in the densest environments increases with increasing redshift. These results lend themselves to a picture in which massive gas-rich galaxies coalesce into proto-cluster environments at z  ≳ 3, interact with other galaxies or with a forming large-scale medium, subsequently using or losing most of their gas in the process, and begin to seed the nascent red sequence that is present in clusters at slightly lower redshifts. 

ABSTRACT We study the projected spatial offset between the ultraviolet continuum and Ly α emission for 65 lensed and unlensed galaxies in the Epoch of Reionization (5 ≤ z ≤ 7), the first such study at these redshifts, in order to understand the potential for these offsets to confuse estimates of the Ly α properties of galaxies observed in slit spectroscopy. While we find that ∼40 per cent of galaxies in our sample show significant projected spatial offsets ($$|\Delta _{\rm {Ly}\alpha -\rm {UV}}|$$), we find a relatively modest average projected offset of $$|\widetilde{\Delta }_{\rm {Ly}\alpha -\rm {UV}}|$$  = 0.61 ± 0.08 proper kpc for the entire sample. A small fraction of our sample, ∼10 per cent, exhibit offsets in excess of 2 proper kpc, with offsets seen up to ∼4 proper kpc, sizes that are considerably larger than the effective radii of typical galaxies at these redshifts. An internal comparison and a comparison to studies at lower redshift yielded no significant evidence of evolution of $$|\Delta _{\rm {Ly}\alpha -\rm {UV}}|$$ with redshift. In our sample, ultraviolet (UV)-bright galaxies ($$\widetilde{L_{\mathrm{ UV}}}/L^{\ast }_{\mathrm{ UV}}=0.67$$) showed offsets a factor of three greater than their fainter counterparts ($$\widetilde{L_{\mathrm{ UV}}}/L^{\ast }_{\mathrm{ UV}}=0.10$$), 0.89 ± 0.18 versus 0.27 ± 0.05 proper kpc, respectively. The presence of companion galaxies and early stage merging activity appeared to be unlikely causes of these offsets. Rather, these offsets appear consistent with a scenario in which internal anisotropic processes resulting from stellar feedback, which is stronger in UV-brighter galaxies, facilitate Ly α fluorescence and/or backscattering from nearby or outflowing gas. The reduction in the Ly α flux due to offsets was quantified. It was found that the differential loss of Ly α photons for galaxies with average offsets is not, if corrected for, a limiting factor for all but the narrowest slit widths (<0.4 arcsec). However, for the largest offsets, if they are mostly perpendicular to the slit major axis, slit losses were found to be extremely severe in cases where slit widths of ≤1 arcsec were employed, such as those planned for James Webb Space Telescope/NIRSpec observations. 

ABSTRACT We present 10 main-sequence ALPINE galaxies (log (M/M⊙) = 9.2−11.1 and $${\rm SFR}=23-190\, {\rm M_{\odot }\, yr^{-1}}$$) at z ∼ 4.5 with optical [O ii] measurements from Keck/MOSFIRE spectroscopy and Subaru/MOIRCS narrow-band imaging. This is the largest such multiwavelength sample at these redshifts, combining various measurements in the ultraviolet, optical, and far-infrared including [C ii]158 $$\mu$$m line emission and dust continuum from ALMA and H α emission from Spitzer photometry. For the first time, this unique sample allows us to analyse the relation between [O ii] and total star-formation rate (SFR) and the interstellar medium (ISM) properties via [O ii]/[C ii] and [O ii]/H α luminosity ratios at z ∼ 4.5. The [O ii]−SFR relation at z ∼ 4.5 cannot be described using standard local descriptions, but is consistent with a metal-dependent relation assuming metallicities around $$50{{\ \rm per\ cent}}$$ solar. To explain the measured dust-corrected luminosity ratios of $$\log (L_{\rm [OII]}/L_{\rm [CII]}) \sim 0.98^{+0.21}_{-0.22}$$ and $$\log (L_{\rm [OII]}/L_{\rm H\alpha }) \sim -0.22^{+0.13}_{-0.15}$$ for our sample, ionization parameters log (U) < −2 and electron densities $$\log (\rm n_e / {\rm [cm^{-3}]}) \sim 2.5-3$$ are required. The former is consistent with galaxies at z ∼ 2−3, however lower than at z > 6. The latter may be slightly higher than expected given the galaxies’ specific SFR. The analysis of this pilot sample suggests that typical log (M/M⊙) > 9 galaxies at z ∼ 4.5 to have broadly similar ISM properties as their descendants at z ∼ 2 and suggest a strong evolution of ISM properties since the epoch of reionization at z > 6. 

Aims. The dust content of normal galaxies and the dust mass density (DMD) at high- z ( z  > 4) are unconstrained given the source confusion and the sensitivity limitations of previous observations. The ALMA Large Program to INvestigate [CII] at Early times (ALPINE), which targeted 118 ultra-violet (UV)-selected star-forming galaxies at 4.4 <  z  < 5.9, provides a new opportunity to tackle this issue for the first time with a statistically robust dataset. Methods. We exploited the rest-frame far-infrared (FIR) fluxes of 23 galaxies individually detected in their continuum emission, as well as stacked continuum images, to measure the dust content of the 118 UV-selected ALPINE galaxies. We focused on the dust scaling relations and, by comparison with predictions from chemical evolution models, we probed the evolutionary stage of UV-selected galaxies at high- z . By using the observed correlation between the UV luminosity and the dust mass, we estimated the DMD of UV-selected galaxies at z  ∼ 5, weighting the galaxies by means of the UV luminosity function. The derived DMD is compared with the value we estimated from ten ALPINE galaxies blindly detected in the FIR continuum, at the redshift of the ALPINE targets. Results. Our ALMA survey allows the exploration for the first time of the dust content in normal star-forming galaxies at z  > 4 in a statistically robust sample of sources. The comparison of the observed dust scaling relations with chemical evolution models suggests that ALPINE galaxies are not likely progenitors of disc galaxies, but of intermediate- and low-mass proto-spheroids, resulting in present-day bulges of spiral or elliptical galaxies. Interestingly, this conclusion is in line with the independent morphological analysis that shows that the majority (∼70%) of the dust-continuum detected galaxies have a disturbed morphology. The DMD obtained at z  ∼ 5 from UV-selected sources is ∼30% of the value obtained from blind FIR-selected sources, showing that the UV selection misses the most dust-rich, UV-obscured galaxies. 

Star formation rate (SFR) measurements at z  > 4 have relied mostly on the rest-frame far-ultraviolet (FUV) observations. The corrections for dust attenuation based on the IRX- β relation are highly uncertain and are still debated in the literature. Hence, rest-frame far-infrared (FIR) observations are necessary to constrain the dust-obscured component of the SFR. In this paper, we exploit the rest-frame FIR continuum observations collected by the ALMA Large Program to INvestigate [CII] at Early times (ALPINE) to directly constrain the obscured SFR in galaxies at 4.4 <  z  < 5.9. We used stacks of continuum images to measure average infrared luminosities taking both detected and undetected sources into account. Based on these measurements, we measured the position of the main sequence of star-forming galaxies and the specific SFR (sSFR) at z  ∼ 4.5 and z  ∼ 5.5. We find that the main sequence and sSFR do not significantly evolve between z  ∼ 4.5 and z  ∼ 5.5, as opposed to lower redshifts. We developed a method to derive the obscured SFR density (SFRD) using the stellar masses or FUV-magnitudes as a proxy of FIR fluxes measured on the stacks and combining them with the galaxy stellar mass functions and FUV luminosity functions from the literature. We obtain consistent results independent of the chosen proxy. We find that the obscured fraction of SFRD is decreasing with increasing redshift, but even at z  ∼ 5.5 it constitutes around 61% of the total SFRD. 

Context. The Lyman- α line in the ultraviolet (UV) and the [CII] line in the far-infrared (FIR) are widely used tools to identify galaxies in the early Universe and to obtain insights into interstellar medium (ISM) properties in high-redshift galaxies. By combining data obtained with ALMA in band 7 at ∼320 GHz as part of the ALMA Large Program to INvestigate [CII] at Early Times (ALPINE) with spectroscopic data from DEIMOS at the Keck Observatory, VIMOS and FORS2 at the Very Large Telescope, we assembled a unique sample of 53 main-sequence star-forming galaxies at 4.4 <   z  <  6 in which we detect both the Lyman- α line in the UV and the [CII] line in the FIR. Aims. The goal of this paper is to constrain the properties of the Ly α emission in these galaxies in relation to other properties of the ISM. Methods. We used [CII], observed with ALMA, as a tracer of the systemic velocity of the galaxies, and we exploited the available optical spectroscopy to obtain the Ly α -[CII] and ISM-[CII] velocity offsets. Results. We find that 90% of the selected objects have Ly α -[CII] velocity offsets in the range 0 <  Δ v Ly α  − [CII]  <  400 km s −1 , in line with the few measurements available so far in the early Universe, and significantly smaller than those observed at lower redshifts. At the same time, we observe ISM-[CII] offsets in the range −500 <  Δ v ISM−[CII]  <  0 km s −1 , in line with values at all redshifts, which we interpret as evidence for outflows in these galaxies. We find significant anticorrelations between Δ v Ly α −[CII] and the Ly α rest-frame equivalent width EW 0 (Ly α ) (or equivalently, the Ly α escape fraction f esc (Ly α )): galaxies that show smaller Δ v Ly α −[CII] have larger EW 0 (Ly α ) and f esc (Ly α ). Conclusions. We interpret these results in the framework of available models for the radiative transfer of Ly α photons. According to the models, the escape of Ly α photons would be favored in galaxies with high outflow velocities, producing large EW 0 (Ly α ) and small Δ v Ly α -[CII] , in agreement with our observations. The uniform shell model would also predict that the Ly α escape in galaxies with slow outflows (0 <   v out  <  300 km s −1 ) is mainly determined by the neutral hydrogen column density (NHI) along the line of sight, while the alternative model by Steidel et al. (2010, ApJ, 717, 289) would more highly favor a combination of NHI at the systemic velocity and covering fraction as driver of the Ly α escape. We suggest that the increase in Ly α escape that is observed in the literature between z  ∼ 2 and z  ∼ 6 is not due to a higher incidence of fast outflows at high redshift, but rather to a decrease in average NHI along the line of sight, or alternatively, a decrease in HI covering fraction.