Search

Galactic outflows are believed to play a critical role in the evolution of galaxies by regulating their mass build-up and star formation [1]. These outflows tend to form bipolar shapes above and below the galactic planes and extend well into the circumgalactic medium (CGM), up to tens of kpc perpendicular to the galaxy. They have been directly observed in the local Universe, e.g., around the Milky Way and M82 [2, 3]. At higher redshifts, cosmological simulations of galaxy formation predict an increase in the frequency and efficiency of galactic outflows due to the increasing star formation activity [4]. Outflows are responsible for removing potential fuel for star formation from the galaxy, while at the same enriching the CGM and the intergalactic medium. These feedback processes, although incorporated as key elements of cosmological simulations, are still poorly constrained on CGM scales. Here we present an ultra-deep MUSE image of the mean Mg II emission surrounding a sample of galaxies at z ≈ 1 that strongly suggests the presence of outflowing gas on physical scales of more than 10 kpc. We find a strong dependence of the detected signal on the inclination of the central galaxy, with edge-on galaxies clearly showing enhanced Mg II emission along the minor axis, while face-on galaxies display much weaker and more isotropic emission. We interpret these findings as supporting the idea that outflows typically have a bipolar cone geometry perpendicular to the galactic disk. We demonstrate that the signal is not dominated by a few outliers. After dividing the galaxy sample in subsamples by mass, the bipolar emission is only detected in galaxies with stellar mass M* >∼ 109.5 M⊙.

JWST has now made it possible to probe the rest-frame optical line emission of high-redshift galaxies extending to z~9, and potentially beyond. To aid in the interpretation of these emerging constraints, in this work we explore predictions for [OIII] emission in high-redshift galaxies using the First Light and Reionisation Epoch Simulations (FLARES). We produce predictions for the [OIII] luminosity function, its correlation with the UV luminosity, and the distribution of equivalent widths (EWs). We also explore how the [OIII] EW correlates with physical properties including specific star formation rate, metallicity, and dust attenuation. Our predictions are largely consistent with recent observational constraints on the luminosity function, average equivalent widths, and line ratios. However, they fail to reproduce the observed tail of high-EW sources and the number density of extreme line emitters. Possibilities to explain these discrepancies include an additional source of ionising photons and/or greater stochasticity in star formation in the model or photometric scatter and/or bias in the observations. With JWST now rapidly building larger samples and a wider range of emission lines the answer to this remaining discrepancy should be available imminently., Comment: 15 pages, accepted for publication in MNRAS, minor changes from original version

The physical conditions of the circumgalactic medium are probed by intervening absorption-line systems in the spectrum of background quasi-stellar objects out to the epoch of cosmic reionization. A correlation between the ionization state of the absorbing gas and the nature of the nearby galaxies has been suggested by the sources detected either in Lyalpha or [C ii] 158 m near to respectively highly-ionized and neutral absorbers. This is also likely linked to the global changes in the incidence of absorption systems of different types and the process of cosmic reionization. Here we report the detection of two [C ii]-emitting galaxies at redshift $z \sim 5.7$ that are associated with a complex high-ionization C iv absorption system. These objects are part of an overdensity of galaxies and have compact sizes (< 2.4 kpc) and narrow line widths (FWHM $\sim$ 62--64 km s-1). Hydrodynamic simulations predict that similar narrow [C ii] emission may arise from the heating of small ($\lesssim$ 3 kpc) clumps of cold neutral medium or a compact photodissociation region. The lack of counterparts in the rest-frame ultraviolet indicates severe obscuration of the sources that are exciting the [C ii] emission. These results may suggest a connection between the properties of the [C ii] emission, the rare overdensity of galaxies and the unusual high ionization state of the gas in this region., Published in Nature on 10 May 2023; authors' version; link to the paper: https://www.nature.com/articles/s41586-023-05901-3

We study the link between gas flow events and key galaxy scaling relations: the relations between star formation rate (SFR) and stellar mass (the main sequence, MS), gas metallicity and stellar mass (the mass-metallicity relation, MZR) and gas metallicity, stellar mass and SFR (the fundamental metallicity relation, FMR). Using all star-forming galaxies (SFGs) in the 22 MUSE fields of the MusE GAs FLOw and Wind (MEGAFLOW) survey, we derive the MS, MZR and FMR scaling relations for 385 SFGs with $M = 10^8 - 10^{11.5}$ $M_\odot$ at redshifts 0.35 < z < 0.85. Using the MUSE data and complementary X-Shooter spectra at 0.85 < z < 1.4, we determine the locations of 21 SFGs associated with inflowing or outflowing circumgalactic gas (i.e. with strong MgII absorption in background quasar spectra) relative to these scaling relations. Compared to a control sample of galaxies without gas flows (i.e., without MgII absorption within 70 kpc of the quasar), SFGs with inflow events (i.e., MgII absorption along the major axis) are preferentially located above the MS, while SFGs with ouflow events (i.e., MgII absorption along the minor axis) are preferentially more metal rich. Our observations support the scenario in which gas accretion increases the SFR while diluting the metal content and where circumgalactic outflows are found in more metal-rich galaxies., 13 pages, 8 figures

The first few 100 Myr at z > 10 mark the last major uncharted epoch in the history of the universe, where only a single galaxy (GN-z11 at z ≈ 11) is currently spectroscopically confirmed. Here we present a search for luminous z > 10 galaxies with JWST/NIRCam photometry spanning ≈1–5 μm and covering 49 arcmin2 from the public JWST Early Release Science programs (CEERS and GLASS). Our most secure candidates are two MUV ≈ −21 systems: GLASS-z12 and GLASS-z10. These galaxies display abrupt ≳1.8 mag breaks in their spectral energy distributions (SEDs), consistent with complete absorption of flux bluewards of Lyα that is redshifted to =+z12.40.3 0.1and=+z10.40.5 0.4. Lower redshift interlopers such as quiescent galaxies with strong Balmer breaks would be comfortably detected at >5σ in multiple bands where instead we find no flux. From SED modeling we infer that these galaxies have already built up ∼109 solar masses in stars over the ≲300–400 Myr after the Big Bang. The brightness of these sources enable morphological constraints. Tantalizingly, GLASS-z10 shows a clearly extended exponential light profile, potentially consistent with a disk galaxy of r50 ≈ 0.7 kpc. These sources, if confirmed, join GN-z11 in defying number density forecasts for luminous galaxies based on Schechter UV luminosity functions, which require a survey area >10× larger than we have studied here to find such luminous sources at such high redshifts. They extend evidence from lower redshifts for little or no evolution in the bright end of the UV luminosity function into the cosmic dawn epoch, with implications for just how early these galaxies began forming. This, in turn, suggests that future deep JWST observations may identify relatively bright galaxies to much earlier epochs than might have been anticipated., R.P.N. acknowledges funding from JWST programs GO-1933 and GO-2279. Support for this work was provided by NASA through the NASA Hubble Fellowship grant HST-HF2-51515.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. We acknowledge support from: the Swiss National Science Foundation through project grant 200020_207349 (P.A.O., A.W.). The Cosmic Dawn Center (DAWN) is funded by the Danish National Research Foundation under grant No. 140. R.J.B. and M.S. acknowledge support from NWO grant TOP1.16.057

We present the first constraints on the prevalence of z>10 galaxies in the Hubble Ultra Deep Field (HUDF) leveraging new NIRCam observations from JEMS (JWST Extragalactic Medium-band Survey). These NIRCam observations probe redward of 1.6$μ$m, beyond the wavelength limit of HST, allowing us to search for galaxies to z>10. These observations indicate that the highest redshift candidate identified in the HUDF09 data with HST, UDFj-39546284, has a redshift of z>11.5, as had been suggested in analyses of the HUDF12/XDF data. This has now been confirmed with JWST NIRSpec. This source is thus the most distant galaxy discovered by HST in its >30 years of operation. Additionally, we identify nine other z~8-13 candidate galaxies over the HUDF, two of which are new discoveries that appear to lie at z~11-12. We use these results to characterize the evolution of the UV luminosity function (LF) from z~15 to z~8.7. While our LF results at z~8.7 and z~10.5 are consistent with previous findings over the HUDF, our new LF estimates at z~12.6 are higher than other results in the literature, potentially pointing to a milder evolution in the UV luminosity density from z~12.6. We emphasize that our LF results are uncertain given the small number of z~12.6 sources and limited volume probed. The new NIRCam data also indicate that the faint z~8-13 galaxies in the HUDF/XDF show blue UV-continuum slopes beta~-2.7, high specific star formation rates ~24.5 Gyr**-1, and high EW (~1300A) [OIII]+H$β$ emission, with two z~8.5 sources showing [OIII]+H$β$ EWs of ~2300 A., 21 pages, 14 figures, 7 tables, resubmitted to MNRAS, after replying to the referee report

We present the first results from the X-SHOOTER Lyman-$\alpha$ survey at $z=2$ (XLS-$z2$). XLS-$z2$ is a deep spectroscopic survey of 35 Lyman-$\alpha$ emitters (LAEs) utilising $\approx90$ hours of exposure time with VLT/X-SHOOTER and covers rest-frame Ly$\alpha$ to H$\alpha$ emission with R$\approx4000$. We present the sample selection, the observations and the data reduction. Systemic redshifts are measured from rest-frame optical lines for 33/35 sources. In the stacked spectrum, our LAEs are characterised by an interstellar medium with little dust, a low metallicity and a high ionisation state. The ionising sources are young hot stars that power strong emission-lines in the optical and high ionisation lines in the UV. The LAEs exhibit clumpy UV morphologies and have outflowing kinematics with blue-shifted SiII absorption, a broad [OIII] component and a red-skewed Ly$\alpha$ line. Typically 30 % of the Ly$\alpha$ photons escape, of which one quarter on the blue side of the systemic velocity. A fraction of Ly$\alpha$ photons escapes directly at the systemic suggesting clear channels enabling a $\approx10$ % escape of ionising photons, consistent with an inference based on MgII. A combination of a low effective HI column density, a low dust content and young star-burst determine whether a star forming galaxy is observed as a LAE. The first is possibly related to outflows and/or a fortunate viewing angle, while we find that the latter two in LAEs are typical for their stellar mass of 10$^9$ M$_{\odot}$., Comment: Main text 26 pages. Accepted for publication in MNRAS

The UV bump is a broad absorption feature centered at 2175{\AA} that is seen in the attenuation/extinction curve of some galaxies, but its origin is not well known. Here, we use a sample of 86 star-forming galaxies at z=1.7-2.7 with deep rest-frame UV spectroscopy from the MUSE HUDF Survey to study the connection between the strength of the observed UV 2175{\AA} bump and the Spitzer/MIPS 24 micron photometry, which at the redshift range of our sample probes mid-IR polycyclic aromatic hydrocarbon (PAH) emission at ~6-8 micron. The sample has robust spectroscopic redshifts and consists of typical main-sequence galaxies with a wide range in stellar mass (log(Mstar/Msun) ~ 8.5-10.7) and star formation rates (SFRs; SFR ~ 1-100 Msun/yr). Galaxies with MIPS detections have strong UV bumps, except for those with mass-weighted ages younger than ~150 Myr. We find that the UV bump amplitude does not change with SFR at fixed stellar mass but increases with mass at fixed SFR. The UV bump amplitude and the PAH strength (defined as mid-IR emission normalized by SFR) are highly correlated and both also correlate strongly with stellar mass. We interpret these correlations as the result of the mass-metallicity relationship, such that at low metallicities PAH emission is weak due to a lower abundance of PAH molecules. The weak or complete absence of the 2175{\AA} bump feature on top of the underlying smooth attenuation curve at low mass/metallicities is then expected if the PAH carriers are the main source of the additional UV absorption., Comment: 9 pages, 7 figures, accepted for publication in mnras

The ionizing photon escape fraction [Lyman continuum (LyC) fesc] of star-forming galaxies is the single greatest unknown in the reionization budget. Stochastic sightline effects prohibit the direct separation of LyC leakers from non-leakers at significant redshifts. Here we circumvent this uncertainty by inferring fesc using resolved (R > 4000) Lyman α (Lyα) profiles from the X-SHOOTER Lyα survey at z = 2 (XLS-z2). With empirically motivated criteria, we use Lyα profiles to select leakers ($f_{\mathrm{ esc}} > 20{{\ \rm per\ cent}}$) and non-leakers ($f_{\mathrm{ esc}} < 5{{\ \rm per\ cent}}$) from a representative sample of >0.2L* Lyman α emitters (LAEs). We use median stacked spectra of these subsets over λrest ≈ 1000-8000 Å to investigate the conditions for LyC fesc. Our stacks show similar mass, metallicity, MUV, and βUV. We find the following differences between leakers versus non-leakers: (i) strong nebular C IV and He II emission versus non-detections; (ii) [O III]/[O II] ≈ 8.5 versus ≈3; (iii) Hα/Hβ indicating no dust versus E(B - V) ≈ 0.3; (iv) Mg II emission close to the systemic velocity versus redshifted, optically thick Mg II; and (v) Lyα fesc of ${\approx} 50{{\ \rm per\ cent}}$ versus ${\approx} 10{{\ \rm per\ cent}}$. The extreme equivalent widths (EWs) in leakers ([O III]+$\mathrm{ H}\beta \approx 1100$ Å rest frame) constrain the characteristic time-scale of LyC escape to ≈3-10 Myr bursts when short-lived stars with the hardest ionizing spectra shine. The defining traits of leakers - extremely ionizing stellar populations, low column densities, a dust-free, high-ionization state interstellar medium (ISM) - occur simultaneously in the $f_{\rm esc} > 20{{\ \rm per\ cent}}$ stack, suggesting they are causally connected, and motivating why indicators like [O III]/[O II] may suffice to constrain fesc at z > 6 with the James Webb Space Telescope (JWST). The leakers comprise half of our sample, have a median LyC$f_{\rm esc} \approx 50{{\ \rm per\ cent}}$ (conservative range: $20\!-\!55{{\ \rm per\ cent}}$), and an ionizing production efficiency $\log ({\xi _{\rm {ion}}/\rm {Hz\ erg^{-1}}})\approx 25.9$ (conservative range: 25.7-25.9). These results show LAEs - the type of galaxies rare at z ≈ 2, but that become the norm at higher redshift - are highly efficient ionizers, with extreme ξion and prolific fesc occurring in sync.

Lyman$-\alpha$ (Ly$\alpha$) emission lines are typically found to be redshifted with respect to the systemic redshifts of galaxies, likely due to resonant scattering of Ly$\alpha$ photons. Here we measure the average velocity offset for a sample of 96 $z\approx3.3$ Ly$\alpha$ emitters (LAEs) with a median Ly$\alpha$ flux (luminosity) of $\approx 10^{-17}~\rm erg~cm^{-2}~s^{-1}$ ($\approx10^{42}~\rm erg~s^{-1}$) and a median star formation rate (SFR) of $\approx1.3 \rm M_{\odot} yr^{-1}$ (not corrected for possible dust extinction), detected by the Multi-Unit Spectroscopic Explorer as part of our MUSEQuBES circumgalactic medium (CGM) survey. By postulating that the stacked CGM absorption profiles of these LAEs, probed by 8 background quasars, must be centered on the systemic redshift, we measure an average velocity offset, V$_{\rm offset} = 171 \pm 8$ $\rm km s^{-1}$, between the Ly$\alpha$ emission peak and the systemic redshift. The observed V$_{\rm offset}$ is lower by factors of $\approx1.4$ and $\approx2.6$ compared to the velocity offsets measured for narrow-band selected LAEs and Lyman break galaxies, respectively, which probe galaxies with higher masses and SFRs. Consistent with earlier studies based on direct measurements for individual objects, we find that the V$_{\rm offset}$ is correlated with the full width at half-maximum of the red peak of the Ly$\alpha$ line, and anti-correlated with the rest-frame equivalent width. Moreover, we find that $V_{\rm offset}$ is correlated with SFR with a sub-linear scaling relation, V$_{\rm offset}\propto \rm SFR^{0.16\pm0.03}$. Adopting the mass scaling for main sequence galaxies, such a relation suggests that V$_{\rm offset}$ scales with the circular velocity of the dark matter halos hosting the LAEs., Comment: Published on 15 May, 2020 along with an erratum (Ref: MNRAS 498, 4424, 2020, doi:10.1093/mnras/staa2668), since Fig. 2 has not been updated in the published version. There are other typos in the published version, introduced by the typesetter, which cannot be revised in the erratum. We feel that the astrp-ph version is more accurate than the published one

While low-luminosity galaxies dominate number counts at all redshifts, their contribution to cosmic reionization is poorly understood due to a lack of knowledge of their physical properties. We isolate a sample of 35 z ≈ 4–5 continuum-faint Lyman-α emitters from deep VLT/MUSE spectroscopy and directly measure their H α emission using stacked Spitzer/IRAC Ch. 1 photometry. Based on Hubble Space Telescope imaging, we determine that the average UV continuum magnitude is fainter than −16 (≈ 0.01 L⋆), implying a median Lyman-α equivalent width of 259 Å. By combining the H α measurement with the UV magnitude, we determine the ionizing photon production efficiency, ξion, a first for such faint galaxies. The measurement of log10 (ξion [Hz erg−1]) = 26.28 (+0.28−0.40) is in excess of literature measurements of both continuum- and emission line-selected samples, implying a more efficient production of ionizing photons in these lower luminosity, Lyman-α-selected systems. We conclude that this elevated efficiency can be explained by stellar populations with metallicities between 4 × 10−4 and 0.008, with light-weighted ages less than 3 Myr., Monthly Notices of the Royal Astronomical Society, 493 (4), ISSN:0035-8711, ISSN:1365-2966, ISSN:1365-8711

The cosmic ionizing emissivity from star-forming galaxies has long been anchored to UV luminosity functions. Here, we introduce an emissivity framework based on Lyα emitters (LAEs), which naturally hones in on the subset of galaxies responsible for the ionizing background due to the intimate connection between production and escape of Lyα and LyC photons. Using constraints on the escape fractions of bright LAEs (LLyα > 0.2L*) at z ≈ 2 obtained from resolved Lyα profiles, and arguing for their redshift-invariance, we show that: (i) quasars and LAEs together reproduce the relatively flat emissivity at z ≈ 2–6, which is non-trivial given the strong evolution in both the star formation density and quasar number density at these epochs and (ii) LAEs produce late and rapid reionization between z ≈ 6−9 under plausible assumptions. Within this framework, the >10 × rise in the UV population-averaged fesc between z ≈ 3–7 naturally arises due to the same phenomena that drive the growing LAE fraction with redshift. Generally, a LAE dominated emissivity yields a peak in the distribution of the ionizing budget with UV luminosity as reported in latest simulations. Using our adopted parameters ($f_{\rm {esc}}=50{{\ \rm per\ cent}}$, ξion = 1025.9 Hz erg−1 for half the bright LAEs), a highly ionizing minority of galaxies with MUV < −17 accounts for the entire ionizing budget from star-forming galaxies. Rapid flashes of LyC from such rare galaxies produce a ‘disco’ ionizing background. We conclude proposing tests to further develop our suggested Lyα-anchored formalism.

We measure the evolution of the rest-frame UV luminosity function (LF) and the stellar mass function (SMF) of Lyman-alpha (Lya) emitters (LAEs) from z~2 to z~6 by exploring ~4000 LAEs from the SC4K sample. We find a correlation between Lya luminosity (LLya) and rest-frame UV (M_UV), with best-fit M_UV=-1.6+-0.2 log10(LLya/erg/s)+47+-12 and a shallower relation between LLya and stellar mass (Mstar), with best-fit log10( Mstar/Msun)=0.9+-0.1 log10(LLya/erg/s)-28+-4.0. An increasing LLya cut predominantly lowers the number density of faint M_UV and low Mstar LAEs. We estimate a proxy for the full UV LFs and SMFs of LAEs with simple assumptions of the faint end slope. For the UV LF, we find a brightening of the characteristic UV luminosity (M_UV*) with increasing redshift and a decrease of the characteristic number density (Phi*). For the SMF, we measure a characteristic stellar mass (Mstar*/Msun) increase with increasing redshift, and a Phi* decline. However, if we apply a uniform luminosity cut of log10 (LLya/erg/s) >= 43.0, we find much milder to no evolution in the UV and SMF of LAEs. The UV luminosity density (rho_UV) of the full sample of LAEs shows moderate evolution and the stellar mass density (rho_M) decreases, with both being always lower than the total rho_UV and rho_M of more typical galaxies but slowly approaching them with increasing redshift. Overall, our results indicate that both rho_UV and rho_M of LAEs slowly approach the measurements of continuum-selected galaxies at z>6, which suggests a key role of LAEs in the epoch of reionisation., Accepted for publication in MNRAS. 20 pages, 13 figures, 4 tables

We investigate the clustering and halo properties of $\sim 5000$ Ly$\alpha$-selected emission line galaxies (LAEs) from the Slicing COSMOS 4K (SC4K) and from archival NB497 imaging of SA22 split in 15 discrete redshift slices between $z \sim 2.5 - 6$. We measure clustering lengths of $r_0 \sim 3 - 6\ h^{-1}$ Mpc and typical halo masses of $\sim 10^{11}$ M$_\odot$ for our narrowband-selected LAEs with typical $L_{\rm{Ly}\alpha} \sim 10^{42 - 43}$ erg s$^{-1}$. The intermediate band-selected LAEs are observed to have $r_0 \sim 3.5 - 15\ h^{-1}$ Mpc with typical halo masses of $\sim 10^{11 - 12}$ M$_\odot$ and typical $L_{\rm{Ly}\alpha} \sim 10^{43 - 43.6}$ erg s$^{-1}$. We find a strong, redshift-independent correlation between halo mass and Ly$\alpha$ luminosity normalized by the characteristic Ly$\alpha$ luminosity, $L^\star(z)$. The faintest LAEs ($L \sim 0.1\ L^\star(z)$) typically identified by deep narrowband surveys are found in $10^{10}$ M$_\odot$ halos and the brightest LAEs ($L \sim 7\ L^\star(z)$) are found in $\sim 5 \times 10^{12}$ M$_\odot$ halos. A dependency on the rest-frame 1500 \AA~UV luminosity, M$_\rm{UV}$, is also observed where the halo masses increase from $10^{11}$ to $10^{13}$ M$_\odot$ for M$_\rm{UV} \sim -19$ to $-23.5$ mag. Halo mass is also observed to increase from $10^{9.8}$ to $10^{12.3}$ M$_\odot$ for dust-corrected UV star formation rates from $\sim 0.6$ to $10$ M$_\odot$ yr$^{-1}$ and continues to increase up to $10^{13.5}$ M$_\odot$ in halo mass, where the majority of those sources are AGN. All the trends we observe are found to be redshift-independent. Our results reveal that LAEs are the likely progenitors of a wide range of galaxies depending on their luminosity, from dwarf-like, to Milky Way-type, to bright cluster galaxies. LAEs therefore provide unique insight into the early formation and evolution of the galaxies we observe in the local Universe.

We study the molecular gas content of 24 star-forming galaxies at $z=3-4$, with a median stellar mass of $10^{9.1}$ M$_{\odot}$, from the MUSE Hubble Ultra Deep Field (HUDF) Survey. Selected by their Lyman-alpha-emission and H-band magnitude, the galaxies show an average EW $\approx 20$ angstrom, below the typical selection threshold for Lyman Alpha Emitters (EW $> 25$ angstrom), and a rest-frame UV spectrum similar to Lyman Break Galaxies. We use rest-frame optical spectroscopy from KMOS and MOSFIRE, and the UV features observed with MUSE, to determine the systemic redshifts, which are offset from Lyman alpha by 346 km s$^{-1}$, with a 100 to 600 km s$^{-1}$ range. Stacking CO(4-3) and [CI](1-0) (and higher-$J$ CO lines) from the ALMA Spectroscopic Survey of the HUDF (ASPECS), we determine $3\sigma$ upper limits on the line luminosities of $4.0\times10^{8}$ K km s$^{-1}$pc$^{2}$ and $5.6\times10^{8}$ K km s$^{-1}$pc$^{2}$, respectively (for a 300 km s$^{-1}$ linewidth). Stacking the 1.2 mm and 3 mm dust continuum flux densities, we find a $3\sigma$ upper limits of 9 $\mu$Jy and $1.2$ $\mu$Jy, respectively. The inferred gas fractions, under the assumption of a 'Galactic' CO-to-H$_{2}$ conversion factor and gas-to-dust ratio, are in tension with previously determined scaling relations. This implies a substantially higher $\alpha_{\rm CO} \ge 10$ and $\delta_{\rm GDR} \ge 1200$, consistent with the sub-solar metallicity estimated for these galaxies ($12 + \log(O/H) \approx 7.8 \pm 0.2$). The low metallicity of $z \ge 3$ star-forming galaxies may thus make it very challenging to unveil their cold gas through CO or dust emission, warranting further exploration of alternative tracers, such as [CII]., Comment: 26 pages, 12 figures, 3 tables. Accepted for publication in ApJ

We present the results from a MUSE survey of twelve $z\simeq3.15$ quasars, which were selected to be much fainter (20, Comment: Accepted to MNRAS. 17 pages, 7 figures

[Abbreviated] Rest-frame UV emission lines probe physical parameters of the emitting star-forming galaxies and their environments. The strongest main UV line, Ly$\alpha$, has been instrumental in advancing the general knowledge of galaxy formation in the early universe. However, observing Ly$\alpha$ emission becomes increasingly challenging at $z \gtrsim 6$ when the neutral hydrogen fraction of the CGM and IGM 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 Ly$\alpha$ emission. The sample of 2052 emission line sources with $1.5 < z < 6.4$ was selected through untargeted source detection in three-dimensional MUSE data cubes. We searched optimally extracted 1D 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-Ly$\alpha$) UV emission lines increases with survey depth, and that the UV emission line strength often correlate with the strength of Ciii]. We measured the velocity offsets of resonant emission lines with respect to systemic tracers as well as the electron density and the gas-phase abundance. Lastly, using "PhotoIonization Model Probability Density Functions" we find that the UV line emitters generally have ionization parameter log10(U) $\approx$ -2.5 and metal mass fractions that scatter around Z $\approx$ 10$^{-2}$, that is Z $\approx$ 0.66Z$\odot$. 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., Comment: Accepted by A&A. Contains 54 pages, 21 figures, and appendices. Catalogs described in Tables B.1 and C.1 will be made available with published paper

Hydrogen Ly${\alpha}$ haloes (LAHs) are commonly used as a tracer of the circumgalactic medium (CGM) at high redshifts. In this work, we aim to explore the existence of Ly${\alpha}$ haloes around individual UV-selected galaxies, rather than around Ly${\alpha}$ emitters (LAEs), at high redshifts. Our sample was continuum-selected with F775W, Comment: 33 pages, 13 + 10 figures, 3 tables, published in A&A, Table 1 updated after the acceptance based on a new version of the MUSE catalog

The fate of galaxies is predominantly determined by their dark matter halo mass. However, recent simulations confirm an important role for the formation history, revealing an intricate relation between galaxies’ central supermassive black holes and the colours of their hosts.

This is a correction to: Monthly Notices of the Royal Astronomical Society, Volume 496, Issue 2, August 2020, Pages 1013–1022, https://doi.org/10.1093/mnras/staa1347

The Lya emitter (LAE) fraction, X_LAE, is a potentially powerful probe of the evolution of the intergalactic neutral hydrogen gas fraction. However, uncertainties in the measurement of X_LAE are still debated. Thanks to deep data obtained with MUSE, we can measure the evolution of X_LAE homogeneously over a wide redshift range of z~3-6 for UV-faint galaxies (down to M_1500~-17.75). This is significantly fainter than in former studies, and allows us to probe the bulk of the population of high-z star-forming galaxies. We construct a UV-complete photo-redshift sample following UV luminosity functions and measure the Lya emission with MUSE using the second data release from the MUSE HUDF Survey. We derive the redshift evolution of X_LAE for M_1500 in [-21.75;-17.75] for the first time with a equivalent width range EW(Lya)>=65 A and find low values of X_ LAE~50 A at z~3-4, in contrast with previous work. The differences in X_LAE mainly arise from selection biases for Lyman Break Galaxies (LBGs) in the literature: UV-faint LBGs are more easily selected if they have strong Lya emission, hence X_LAE is biased towards higher values. Our results suggest either a lower increase of X_LAE towards z~6 than previously suggested, or even a turnover of X_LAE at z~5.5, which may be the signature of a late or patchy reionization process. We compared our results with predictions from a cosmological galaxy evolution model. We find that a model with a bursty star formation (SF) can reproduce our observed X_LAE much better than models where SF is a smooth function of time., Comment: 25 pages, 17 figures, 5 tables, accepted for publication in A&A

A prediction of the classic active galactic nuclei (AGN) unification model is the presence of ionisation cones with different orientations depending on the AGN type. Confirmations of this model exist for present times, but it is less clear in the early Universe. Here, we use the morphology of giant Ly$\alpha$ nebulae around AGNs at redshift z$\sim$3 to probe AGN emission and therefore the validity of the AGN unification model at this redshift. We compare the spatial morphology of 19 nebulae previously found around type I AGNs with a new sample of 4 Ly$\alpha$ nebulae detected around type II AGNs. Using two independent techniques, we find that nebulae around type II AGNs are more asymmetric than around type I, at least at radial distances $r>30$~physical kpc (pkpc) from the ionizing source. We conclude that the type I and type II AGNs in our sample show evidence of different surrounding ionising geometries. This suggests that the classical AGN unification model is also valid for high-redshift sources. Finally, we discuss how the lack of asymmetry in the inner parts (r$\lesssim$30 pkpc) and the associated high values of the HeII to Ly$\alpha$ ratios in these regions could indicate additional sources of (hard) ionizing radiation originating within or in proximity of the AGN host galaxies. This work demonstrates that the morphologies of giant Ly$\alpha$ nebulae can be used to understand and study the geometry of high redshift AGNs on circum-nuclear scales and it lays the foundation for future studies using much larger statistical samples., Comment: 15 pages, 13 figures, accepted for publication in MNRAS

We report the spectroscopic confirmation of a new protocluster in the COSMOS field at $z$ $\sim$ 2.2, COSMOS Cluster 2.2 (CC2.2), originally identified as an overdensity of narrowband selected H$\alpha$ emitting candidates. With only two masks of Keck/MOSFIRE near-IR spectroscopy in both $H$ ($\sim$ 1.47-1.81 $\mu$m) and $K$ ($\sim$ 1.92-2.40 $\mu$m) bands ($\sim$ 1.5 hour each), we confirm 35 unique protocluster members with at least two emission lines detected with S/N $>$ 3. Combined with 12 extra members from the zCOSMOS-deep spectroscopic survey (47 in total), we estimate a mean redshift and a line-of-sight velocity dispersion of $z_{mean}$=2.23224 $\pm$ 0.00101 and $\sigma_{los}$=645 $\pm$ 69 km s$^{-1}$ for this protocluster, respectively. Assuming virialization and spherical symmetry for the system, we estimate a total mass of $M_{vir}$ $\sim$ $(1-2) \times$10$^{14}$ $M_{\odot}$ for the structure. We evaluate a number density enhancement of $\delta_{g}$ $\sim$ 7 for this system and we argue that the structure is likely not fully virialized at $z$ $\sim$ 2.2. However, in a spherical collapse model, $\delta_{g}$ is expected to grow to a linear matter enhancement of $\sim$ 1.9 by $z$=0, exceeding the collapse threshold of 1.69, and leading to a fully collapsed and virialized Coma-type structure with a total mass of $M_{dyn}$($z$=0) $\sim$ 9.2$\times$10$^{14}$ $M_{\odot}$ by now. This observationally efficient confirmation suggests that large narrowband emission-line galaxy surveys, when combined with ancillary photometric data, can be used to effectively trace the large-scale structure and protoclusters at a time when they are mostly dominated by star-forming galaxies.

The observed properties of the Lyman-$\alpha$ (Ly$\alpha$) emission line are a powerful probe of neutral gas in and around galaxies. We present spatially resolved Ly$\alpha$ spectroscopy with VLT/MUSE targeting VR7, a UV-luminous galaxy at $z=6.532$ with moderate Ly$\alpha$ equivalent width (EW$_0\approx38$ {\AA}). These data are combined with deep resolved [CII]$_{\rm 158 \mu m}$ spectroscopy obtained with ALMA and UV imaging from {\it HST} and we also detect UV continuum with MUSE. Ly$\alpha$ emission is clearly detected with S/N $\approx40$ and FWHM of 374 km s$^{-1}$. Ly$\alpha$ and [CII] are similarly extended beyond the UV, with effective radius r$_{\rm eff} = 2.1\pm0.2$ kpc for a single exponential model or r$_{\rm eff, Ly\alpha, halo} = 3.45^{+1.08}_{-0.87}$ kpc when measured jointly with the UV continuum. The Ly$\alpha$ profile is broader and redshifted with respect to the [CII] line (by 213 km s$^{-1}$), but there are spatial variations that are qualitatively similar in both lines and coincide with resolved UV components. This suggests that the emission originates from two components with plausibly different HI column densities. We place VR7 in the context of other galaxies at similar and lower redshift. The Ly$\alpha$ halo scale length is similar at different redshifts and velocity shifts with respect to the systemic are typically smaller. Overall, we find little indications of a more neutral vicinity at higher redshift. This means that the local ($\sim 10$ kpc) neutral gas conditions that determine the observed Ly$\alpha$ properties in VR7 resemble the conditions in post-re-ionisation galaxies., Comment: 13 pages, 10 figures. Accepted for publication in MNRAS

The decline in abundance of Lyman-$\alpha$ (Ly$\alpha$) emitting galaxies at $z \gtrsim 6$ is a powerful and commonly used probe to constrain the progress of cosmic reionization. We use the CoDaII simulation, which is a radiation hydrodynamic simulation featuring a box of $\sim 94$ comoving Mpc side length, to compute the Ly$\alpha$ transmission properties of the intergalactic medium (IGM) at $z\sim 5.8$ to $7$. Our results mainly confirm previous studies, i.e., we find a declining Ly$\alpha$ transmission with redshift and a large sightline-to-sightline variation. However, motivated by the recent discovery of blue Ly$\alpha$ peaks at high redshift, we also analyze the IGM transmission on the blue side, which shows a rapid decline at $z\gtrsim 6$ of the blue transmission. This low transmission can be attributed not only to the presence of neutral regions but also to the residual neutral hydrogen within ionized regions, for which a density even as low as $n_{\rm HI}\sim 10^{-9}\,\mathrm{cm}^{-3}$ (sometimes combined with kinematic effects) leads to a significantly reduced visibility. Still, we find that $\sim 1\%$ of sightlines towards $M_{\mathrm{1600AB}}\sim -21$ galaxies at $z\sim 7$ are transparent enough to allow a transmission of a blue Ly$\alpha$ peak. We discuss our results in the context of the interpretation of observations., Comment: 13 pages, 12 figures. Published version

Galaxy evolution is driven by a variety of physical processes that are predicted to proceed at different rates for different dark matter haloes and environments across cosmic times. A record of this evolution is preserved in galaxy stellar populations, which we can access using absorption-line spectroscopy. Here we explore the large LEGA-C survey (DR3) to investigate the role of the environment and stellar mass on stellar populations at z ∼ 0.6–1 in the COSMOS field. Leveraging the statistical power and depth of LEGA-C, we reveal significant gradients in D n 4000 and Hδ equivalent widths (EWs) distributions over the stellar mass versus environment 2D spaces for the massive galaxy population (M > 1010 M ⊙) at z ∼ 0.6–1.0. D n 4000 and Hδ EWs primarily depend on stellar mass, but they also depend on environment at fixed stellar mass. By splitting the sample into centrals and satellites, and in terms of star-forming galaxies and quiescent galaxies, we reveal that the significant environmental trends of D n 4000 and Hδ EW, when controlling for stellar mass, are driven by quiescent galaxies. Regardless of being centrals or satellites, star-forming galaxies reveal D n 4000 and Hδ EWs, which depend strongly on their stellar mass and are completely independent of the environment at 0.6 < z < 1.0. The environmental trends seen for satellite galaxies are fully driven by the trends that hold only for quiescent galaxies, combined with the strong environmental dependency of the quiescent fraction at fixed stellar mass. Our results are consistent with recent predictions from simulations that point toward massive galaxies forming first in overdensities or the most compact dark matter haloes.

We present Keck/LRIS follow-up spectroscopy for 13 photometric candidates of extremely metal-poor galaxies (EMPGs) selected by a machine-learning technique applied to the deep (∼26 AB mag) optical and wide-area (∼500 deg2) Subaru imaging data in the EMPRESS survey. Nine out of the 13 candidates are EMPGs with an oxygen abundance (O/H) less than ∼10% solar value (O/H)⊙, and four sources are contaminants of moderately metal-rich galaxies or no emission-line objects. Notably, two out of the nine EMPGs have extremely low stellar masses and oxygen abundances of 5 × 104–7 × 105 M ⊙ and 2%–3% (O/H)⊙, respectively. With a sample of five EMPGs with (Fe/O) measurements, two (three) of which are taken from this study (the literature), we confirm that two EMPGs with the lowest (O/H) ratios of ∼2% (O/H)⊙ show high (Fe/O) ratios of ∼0.1, close to the solar abundance ratio. Comparing galaxy chemical enrichment models, we find that the two EMPGs cannot be explained by a scenario of metal-poor gas accretion/episodic star formation history due to their low (N/O) ratios. We conclude that the two EMPGs can be reproduced by the inclusion of bright hypernovae and/or hypothetical pair-instability supernovae (SNe) preferentially produced in a metal-poor environment. This conclusion implies that primordial galaxies at z ∼ 10 could have a high abundance of Fe that did not originate from Type Ia SNe with delays and that Fe may not serve as a cosmic clock for primordial galaxies.

While traditionally associated with active galactic nuclei (AGN), the properties of the CII], CIII] and CIV emission lines are still uncertain as large, unbiased samples of sources are scarce. We present the first blind, statistical study of CII], CIII] and CIV emitters at $z\sim0.68,1.05,1.53$, respectively, uniformly selected down to a flux limit of $\sim4\times10^{-17}$ erg s$^{-1}$ cm$^{-1}$ through a narrow band survey covering an area of $\sim1.4$ deg$^2$ over COSMOS and UDS. We detect 16 CII], 35 CIII] and 17 CIV emitters, whose nature we investigate using optical colours as well as HST, X-ray, radio and far infra-red data. We find that $z\sim0.7$ CII] emitters are consistent with a mixture of blue (UV slope $\beta=-2.0\pm0.4$) star forming galaxies with disky HST structure and AGN with Seyfert-like morphologies. Bright CII] emitters have individual X-ray detections as well as high average black hole accretion rates (BHAR) of $\sim0.1$ $M_{\odot}$ yr$^{-1}$. CIII] emitters at $z\sim1.05$ trace a general population of SF galaxies, with $\beta=-0.8\pm1.1$, a variety of optical morphologies, including isolated and interacting galaxies and low BHAR ($

Distant luminous Lyman-alpha emitters are excellent targets for detailed observations of galaxies in the epoch of reionisation. Spatially resolved observations of these galaxies allow us to simultaneously probe the emission from young stars, partially ionised gas in the interstellar medium and to constrain the properties of the surrounding hydrogen in the circumgalactic medium. We review recent results from (spectroscopic) follow-up studies of the rest-frame UV, Lyman-alpha and [CII] emission in luminous galaxies observed ~500 Myr after the Big Bang with ALMA, HST/WFC3 and VLT/X-SHOOTER. These galaxies likely reside in early ionised bubbles and are complex systems, consisting of multiple well separated and resolved components where traces of metals are already present., Comment: 5 pages, 3 figures. Proceeding of IAU Symposium #352, 2019, "Uncovering early galaxy evolution in the ALMA and JWST era"

We explore deep rest-frame UV to FIR data in the COSMOS field to measure the individual spectral energy distributions (SED) of the ~4000 SC4K (Sobral et al. 2018) Lyman-alpha (Lya) emitters (LAEs) at z~2-6. We find typical stellar masses of 10$^{9.3\pm0.6}$ M$_{\odot}$ and star formation rates (SFR) of SFR$_{SED}=4.4^{+10.5}_{-2.4}$ M$_{\odot}$/yr and SFR$_{Lya}=5.9^{+6.3}_{-2.6}$ M$_{\odot}$/yr, combined with very blue UV slopes of beta=-2.1$^{+0.5}_{-0.4}$, but with significant variations within the population. M$_{UV}$ and beta are correlated in a similar way to UV-selected sources, but LAEs are consistently bluer. This suggests that LAEs are the youngest and/or most dust-poor subset of the UV-selected population. We also study the Lya rest-frame equivalent width (EW$_0$) and find 45 "extreme" LAEs with EW$_0>240$ A (3 $��$), implying a low number density of $(7\pm1)\times10^{-7}$ Mpc$^{-3}$. Overall, we measure little to no evolution of the Lya EW$_0$ and scale length parameter ($w_0$) which are consistently high (EW$_0=140^{+280}_{-70}$ A, $w_0=129^{+11}_{-11}$ A) from z~6 to z~2 and below. However, $w_0$ is anti-correlated with M$_{UV}$ and stellar mass. Our results imply that sources selected as LAEs have a high Lya escape fraction (f$_{esc, Lya}$) irrespective of cosmic time, but f$_{esc, Lya}$ is still higher for UV-fainter and lower mass LAEs. The least massive LAEs ($, Accepted for publication in MNRAS. 23 pages, 11 figures, 3 tables + appendices. The full SC4K catalogue of LAEs with PSF photometry, stellar masses, SFRs and other properties for individual LAEs, is available at https://goo.gl/q9yfKo

Despite recent progress in understanding Lyman-alpha (Lya) emitters (LAEs), relatively little is known regarding their typical black hole activity across cosmic time. Here, we study the X-ray and radio properties of ~4000 LAEs at 2.23) and find an average luminosity of 10^{44.31+-0.01} erg/s and an average black hole accretion rate (BHAR) of 0.72+-0.01 Msun/yr, consistent with moderate to high accreting AGN. We detect 120 sources in deep radio data (radio AGN fraction of 3.2%+-0.3%). The global AGN fraction (8.6%+-0.4%) rises with Lya luminosity and declines with increasing redshift. For X-ray detected LAEs, Lya luminosities correlate with the BHARs, suggesting that Lya luminosity becomes an accretion rate indicator. Most LAEs (93.1+-0.6%) at 2, Comment: Accepted for publication in MNRAS. 21 pages, 15 figures, 2 tables + appendices. The full SC4K catalogue of LAEs with X-ray, radio, FIR and Lya measurements is available with the MNRAS refereed version, along with tables presenting the full stacking results in X-rays and radio

We discuss the nature and physical properties of gas-mass selected galaxies in the ALMA spectroscopic survey (ASPECS) of the Hubble Ultra Deep Field (HUDF). We capitalize on the deep optical integral-field spectroscopy from the MUSE HUDF Survey and multi-wavelength data to uniquely associate all 16 line-emitters, detected in the ALMA data without preselection, with rotational transitions of carbon monoxide (CO). We identify ten as CO(2-1) at $1 < z < 2$, five as CO(3-2) at $2 < z < 3$ and one as CO(4-3) at $z = 3.6$. Using the MUSE data as a prior, we identify two additional CO(2-1)-emitters, increasing the total sample size to 18. We infer metallicities consistent with (super-)solar for the CO-detected galaxies at $z \le 1.5$, motivating our choice of a Galactic conversion factor between CO luminosity and molecular gas mass for these galaxies. Using deep Chandra imaging of the HUDF, we determine an X-ray AGN fraction of 20% and 60% among the CO-emitters at $z \sim 1.4$ and $z \sim 2.6$, respectively. Being a CO-flux limited survey, ASPECS-LP detects molecular gas in galaxies on, above and below the main sequence (MS) at $z \sim 1.4$. For stellar masses $\ge 10^{10} (10^{10.5})$ M$_{\odot}$, we detect about 40% (50%) of all galaxies in the HUDF at $1 < z < 2$ ($2 < z < 3$). The combination of ALMA and MUSE integral-field spectroscopy thus enables an unprecedented view on MS galaxies during the peak of galaxy formation., 31 pages, 20 figures, 5 tables. Resubmitted to ApJ after addressing the first round of comments by the referee

We present new deep ALMA and HST/WFC3 observations of MASOSA and VR7, two luminous Ly$\alpha$ emitters (LAEs) at $z=6.5$, for which the UV continuum level differ by a factor four. No IR dust continuum emission is detected in either, indicating little amounts of obscured star formation and/or high dust temperatures. MASOSA, with a UV luminosity M$_{1500}=-20.9$, compact size and very high Ly$\alpha$ EW$_{0}\approx145$ A, is undetected in [CII] to a limit of L$_{\rm [CII]}, Comment: Main text 19 pages, 16 figures. Appendix tables available in digital format on request. Accepted for publication by ApJ. v3: updated typo in appendix table