Context. Lyman alpha blobs (LABs) are large-scale radio-quiet Lyman; (Ly;) nebula at high-z that occur predominantly in overdense proto-cluster regions. In particular, there is the prototypical SSA22a-LAB1 at z=3.1, which has become an observational reference for LABs across the electromagnetic spectrum.

Aims. We want to understand the powering mechanisms that drive the LAB so that we may gain empirical insights into the galaxy-formation processes within a rare dense environment at high-z. Thus, we need to infer the distribution, the dynamics, and the ionisation state of LAB 1's Ly; emitting gas.

Methods. LAB 1 was observed for 17.2 h with the VLT/MUSE integral-field spectrograph. We produced optimally extracted narrow band images, in Ly ; lambda 1216, HeII lambda 1640, and we tried to detect CIV lambda 1549 emission. By utilising a moment-based analysis, we mapped the kinematics and the line profile characteristics of the blob. We also linked the inferences from the line profile analysis to previous results from imaging polarimetry.

Results. We map Ly ; emission from the blob down to surface-brightness limits of approximate to 6x10(-19) erg s(-1) cm(-2) arcsec(-2). At this depth, we reveal a bridge between LAB 1 and its northern neighbour LAB 8, as well as a shell-like filament towards the south of LAB 1. The complexity and morphology of the Ly alpha profile vary strongly throughout the blob. Despite the complexity, we find a coherent large-scale east-west velocity gradient of similar to 1000 km s(-1) that is aligned perpendicular to the major axis of the blob. Moreover, we observe a negative correlation of Ly alpha polarisation fraction with Ly alpha line width and a positive correlation with absolute line-of-sight velocity. Finally, we reveal HeII emission in three distinct regions within the blob, however, we can only provide upper limits for CIV.

Conclusions. Various gas excitation mechanisms are at play in LAB 1: ionising radiation and feedback effects dominate near the embedded galaxies, while Ly alpha scattering contributes at larger distances. However, HeII/Ly alpha ratios combined with upper limits on CIV/Ly alpha are not able to discriminate between active galactic nucleus ionisation and feedback- driven shocks. The alignment of the angular momentum vector parallel to the morphological principal axis appears to be at odds with the predicted norm for high-mass halos, but this most likely reflects that LAB 1 resides at a node of multiple intersecting filaments of the cosmic web. LAB 1 can thus be thought of as a progenitor of a present-day massive elliptical within a galaxy cluster.

Contact. This paper presents the results obtained with the Multi-Unit Spectroscopic Explorer (MUSE) at the ESOVery Large Telescope on the faint end of the Lyman-alpha luminosity function (LF) based on deep observations of four lensing clusters. The goal of our project is to set strong constraints on the relative contribution of the Lyman-alpha emitter (LAE) population to cosmic reionization.

Aims. The precise aim of the present study is to further constrain the abundance of LAEs by taking advantage of the magnification provided by lensing clusters to build a blindly selected sample of galaxies which is less biased than current blank field samples in redshift and luminosity. By construction, this sample of LAEs is complementary to those built from deep blank fields, whether observed by MUSE or by other facilities, and makes it possible to determine the shape of the LF at fainter levels, as well as its evolution with redshift.

Methods. We selected a sample of 156 LAEs with redshifts between 2.9 <= z <= 6.7 and magnification-corrected luminosities in the range 39 less than or similar to log L-Ly alpha [erg s(-1)] less than or similar to 43. To properly take into account the individual differences in detection conditions between the LAEs when computing the LF, including lensing configurations, and spatial and spectral morphologies, the non-parametric 1/V-max method was adopted. The price to pay to benefit from magnification is a reduction of the effective volume of the survey, together with a more complex analysis procedure to properly determine the effective volume V-max for each galaxy. In this paper we present a complete procedure for the determination of the LF based on IFU detections in lensing clusters. This procedure, including some new methods for masking, effective volume integration and (individual) completeness determinations, has been fully automated when possible, and it can be easily generalized to the analysis of IFU observations in blank fields.

Results. As a result of this analysis, the Lyman-alpha LF has been obtained in four different redshift bins: 2.9 < z < 6; 7, 2.9 < z < 4.0, 4 : 0 < z < 5.0; and 5 : 0 < z < 6.7 with constraints down to log L-Ly alpha = 40.5. From our data only, no significant evolution of LF mean slope can be found. When performing a Schechter analysis also including data from the literature to complete the present sample towards the brightest luminosities, a steep faint end slope was measured varying from alpha = -1.69(-0.08)(+0.08) to alpha = -1.87(-0 .12)(+0.12) between the lowest and the highest redshift bins.

Conclusions. The contribution of the LAE population to the star formation rate density at z similar to 6 is less than or similar to 50% depending on the luminosity limit considered, which is of the same order as the Lyman-break galaxy (LBG) contribution. The evolution of the LAE contribution with redshift depends on the assumed escape fraction of Lyman-alpha photons, and appears to slightly increase with increasing redshift when this fraction is conservatively set to one. Depending on the intersection between the LAE/LBG populations, the contribution of the observed galaxies to the ionizing flux may suffice to keep the universe ionized at z similar to 6.

Context. Mrk 71/NGC2366 is the closest green pea (GP) analog and candidate Lyman Continuum (LyC) emitter. Recently, 11 LyC-leaking GPs have been detected through direct observations of the ionizing continuum, making this the most abundant class of confirmed LyC-emitters at any redshift. High resolution, multiwavelength studies of GPs can lead to an understanding of the method(s), through which LyC escapes from these galaxies.

Aims. The proximity of Mrk 71/NCG2366 offers unprecedented detail on the inner workings of a GP analog, and enables us to identify the mechanisms of LyC escape.

Methods. We used 5825-7650 angstrom integral field unit PMAS observations to study the kinematics and physical conditions in Mrk 71. An electron density map was obtained from the [S II] ratio. A fortuitous second order contamination by the [O II] lambda 3727 doublet enabled the construction of an electron temperature map. Resolved maps of sound speed, thermal broadening, true velocity dispersion, and Mach number were obtained and compared to the high resolution magnetohydrodynamic SImulating the LifeCycle of molecular Clouds (SILCC) simulations.

Results. Two regions of increased velocity dispersion indicative of outflows are detected to the north and south of the super star cluster, knot B, with redshifted and blueshifted velocities, respectively. We confirm the presence of a faint broad kinematical component, which is seemingly decoupled from the outflow regions, and is fainter and narrower than previously reported in the literature. Within uncertainties, the low- and high-ionization gasses move together. Outside of the core of Mrk 71, an increase in Mach numbers is detected, implying a decrease in gas density. Simulations suggest this drop in density can be as high as similar to 4 dex, down to almost optically thin levels, which would imply a nonzero LyC escape fraction along the outflows even when assuming all of the detected II I gas is located in front of Mrk 71 in the line of sight.

Conclusions. Our results strongly indicate that kinematical feedback is an important ingredient for LyC leakage in GPs.

We present an analysis of HI Lyman alpha emission in deep VLT/MUSE observations of two highly magnified and extended galaxies at z = 3.5 and 4.03, including a newly discovered, almost complete Einstein ring. While these Lyman a haloes are intrinsically similar to the ones typically seen in other MUSE deep fields, the benefits of gravitational lensing allow us to construct exceptionally detailed maps of Lyman alpha line properties at sub-kpc scales. By combining all multiple images, we are able to observe complex structures in the Lyman a emission and uncover small (similar to 120 km s(-1) in Lyman alpha peak shift), but significant at >4 sigma, systematic variations in the shape of the Lyman a line profile within each halo. Indeed, we observe a global trend for the line peak shift to become redder at large radii, together with a strong correlation between the peak wavelength and line width. This systematic intrahalo variation is markedly similar to the object-to-object variations obtained from the integrated properties of recent large samples. Regions of high surface brightness correspond to relatively small line shifts, which could indicate that Lyman alpha emission escapes preferentially from regions where the line profile has been less severely affected by scattering of Lyman alpha photons.

We have used the capability of the Multi-Unit Spectroscopic Explorer (MUSE) instrument to explore the impact of stellar feedback at large scales in Haro 11, a galaxy under extreme starburst condition and one of the first galaxies where Lyman continuum (LyC) has been detected. Using H alpha, [O III] lambda 5007, and [O I]) lambda 6300 emission lines from deep MUSE observations, we have constructed a sequence of velocity-dependent maps of the H alpha emission, the state of the ionized gas, and a tracer of fast shocks. These allowed us to investigate the ionization structure of the galaxy in 50 km s(-1) bins over a velocity range of -400 to 350 km s(-1). The ionized gas in Haro 11 is assembled by a rich arrangement of structures, such as superbubbles, filaments, arcs, and galactic ionized channels, whose appearances change drastically with velocity. The central star-forming knots and the star-forming dusty arm are the main engines that power the strong mechanical feedback in this galaxy, although with different impact on the ionization structure. Haro 11 appears to leak LyC radiation in many directions. We found evidence of a kpc-scale fragmented superbubble that may have cleared galactic scale channels in the ISM. Additionally, the Southwestern hemisphere is highly ionized in all velocities, hinting at a density hound scenario. A compact kpc-scale structure of lowly ionized gas coincides with the diffuse Ly alpha emission and the presence of fast shocks. Finally, we find evidence that a significant fraction of the ionized gas mass may escape the gravitational potential of the galaxy.

We investigate the Lyman alpha emitter (LAE) luminosity function (LF) within the redshift range 2.9 <= z <= 6 from the first instalment of the blind integral field spectroscopic MUSE-Wide survey. This initial part of the survey probes a region of 22.2 arcmin(2) in the CANDELS/GOODS-S field (24 MUSE pointings with 1h integrations). The dataset provided us with 237 LAEs from which we construct the LAE LF in the luminosity range 42.2 <= log L-Ly alpha[erg s(-1)] <= 43.5 within a volume of 2.3 x 10(5) Mpc(3). For the LF construction we utilise three different non-parametric estimators: the classical 1/V-max method, the C- method, and an improved binned estimator for the differential LF. All three methods deliver consistent results, with the cumulative LAE LF being Phi(log L-Ly alpha[erg s(-1)] = 43.5) similar or equal to 3 x 10(-6) Mpc(-3) and Phi(log L-Ly alpha[erg s(-1)] = 42.2) similar or equal to 2 x 10(-3) Mpc(-3) towards the bright and faint end of our survey, respectively. By employing a non-parametric statistical test, and by comparing the full sample to subsamples in redshift bins, we find no supporting evidence for an evolving LAE LF over the probed redshift and luminosity range. Using a parametric maximum-likelihood technique we determine the best-fitting Schechter function parameters alpha = -1.84(-0.41)(+0.42) and log L*[erg s(-1)] = 42.2(-0.16)(+0.22) with the corresponding normalisation log phi*[Mpc(-3)] = -2.71. However, the dynamic range in Ly alpha luminosities probed by MUSE-Wide leads to a strong degeneracy between alpha and L*. Moreover, we find that a power-law parameterisation of the LF appears to be less consistent with the data compared to the Schechter function, even so when not excluding the X-Ray identified AGN from the sample. When correcting for completeness in the LAE LF determinations, we take into account that LAEs exhibit diffuse extended low surface brightness halos. We compare the resulting LF to one obtained by applying a correction assuming compact point-like emission. We find that the standard correction underestimates the LAE LF at the faint end of our survey by a factor of 2.5. Contrasting our results to the literature we find that at log L-Ly alpha[erg s(-1)] less than or similar to 42.5 previous LAE LF determinations from narrow-band surveys appear to be affected by a similar bias.

We present the MUSE-Wide survey, a blind, 3D spectroscopic survey in the CANDELS/GOODS-S and CANDELS/COSMOS regions. The final survey will cover 100 x 1 arcmin(2) MUSE fields. Each MUSE-Wide pointing has a depth of one hour and hence targets more extreme and more luminous objects over ten times the area of the MUSE-Deep fields. The legacy value of MUSE-Wide lies in providing spectroscopy of everything without photometric pre-selection. We describe the data reduction, post-processing and PSF characterization of the first 44 CANDELS /GOODS-S MUSE-Wide pointings released with this publication. Using a 3D matched filtering approach we detect 1602 emission line sources, including 479 Lyman-alpha (Ly alpha) emitting galaxies with redshifts 2.9 less than or similar to z less than or similar to 6.3. We cross-matched the emission line sources to existing photometric catalogs, finding almost complete agreement in redshifts (photometric and spectroscopic) and stellar masses for our low redshift (z < 1.5) emitters. At high redshift, we only find similar to 55% matches to photometric catalogs. We encounter a higher outlier rate and a systematic offset of Delta z similar or equal to 0.2 when comparing our MUSE redshifts with photometric redshifts from the literature. Cross-matching the emission line sources with X-ray catalogs from the Chandra Deep Field South, we find 127 matches, mostly in agreement with the literature redshifts, including ten objects with no prior spectroscopic identification. Stacking X-ray images centered on our Ly alpha emitters yields no signal; the Ly alpha population is not dominated by even low luminosity AGN. Other cross-matches of our emission-line catalog to radio and submillimeter data, yielded far lower numbers of matches, most of which already were covered by the X-ray catalog. A total of 9205 photometrically selected objects from the CANDELS survey lie in the MUSE-Wide footprint, of which we provide optimally extracted 1D spectra. We are able to determine the spectroscopic redshift of 98% of 772 photometrically selected galaxies brighter than 24th F775W magnitude. All the data in the first data release - datacubes, catalogs, extracted spectra, maps - are available on the MUSE-Wide data release webpage.

The amount of integral field spectrograph (IFS) data has grown considerably over the last few decades. The demand for tools to analyze such data is therefore bigger now than ever. We present a flexible Python tool for Three-Dimensional Optimal Spectral Extraction (TDOSE) from IFS data cubes. TDOSE works on any three-dimensional data cube and bases the spectral extractions on morphological reference image models. By default, these models are generated and composed of multiple multivariate Gaussian components, but can also be constructed with independent modeling tools and be provided as input to TDOSE. In each wavelength layer of the IFS data cube, TDOSE simultaneously optimizes all sources in the morphological model to minimize the difference between the scaled model components and the IFS data. The flux optimization produces individual data cubes containing the scaled three-dimensional source models. This allows the efficient de-blending of flux in both the spatial and spectral dimensions of the IFS data cubes, and extraction of the corresponding one-dimensional spectra. TDOSE implicitly requires an assumption about the two-dimensional light distribution. We describe how the flexibility of TDOSE can be used to mitigate and correct for deviations from the input distribution. Furthermore, we present an example of how the three-dimensional source models generated by TDOSE can be used to improve two-dimensional maps of physical parameters like velocity, metallicity, or star formation rate when flux contamination is a problem. By extracting TDOSE spectra of similar to 150 [OII] emitters from the MUSE-Wide survey we show that the median increase in line flux is similar to 5% when using multi-component models as opposed to single-component models. However, the increase in recovered line emission in individual cases can be as much as 50%. Comparing the TDOSE model-based extractions of the MUSE-Wide [OII] emitters with aperture spectra, the TDOSE spectra provides a median flux (S/N) increase of 9% (14%). Hence, TDOSE spectra optimize the S/N while still being able to recover the total emitted flux.

We report the discovery of six spatially extended (10-100 kpc) line-emitting nebulae in the z approximate to 0.57 galaxy group hosting PKS 0405-123, one of the most luminous quasars at z < 1. The discovery is enabled by the Multi Unit Spectroscopic Explorer and provides tantalizing evidence connecting large-scale gas streams with nuclear activity on scales of <10 proper kpc (pkpc). One of the nebulae exhibits a narrow, filamentary morphology extending over 50 pkpc toward the quasar with narrow internal velocity dispersion (50 km s(-1)) and is not associated with any detected galaxies, consistent with a cool intragroup medium filament. Two of the nebulae are 10 pkpc north and south of the quasar with tidal-arm-like morphologies. These two nebulae, along with a continuum-emitting arm extending 60 pkpc from the quasar, are signatures of interactions that are expected to redistribute angular momentum in the host interstellar medium (ISM) to facilitate star formation and quasar fueling in the nucleus. The three remaining nebulae are among the largest and most luminous [O III] emitting blobs known (1400-2400 pkpc(2)) and correspond both kinematically and morphologically to interacting galaxy pairs in the quasar host group, consistent with arising from stripped ISM rather than large-scale quasar outflows. The presence of these large- and small-scale nebulae in the vicinity of a luminous quasar bears significantly on the effect of large-scale environment on galaxy and black hole fueling, providing a natural explanation for the previously known correlation between quasar luminosity and cool circumgalactic medium.

Galaxies are surrounded by large reservoirs of gas, mostly hydrogen, that are fed by inflows from the intergalactic medium and by outflows from galactic winds. Absorption-line measurements along the lines of sight to bright and rare background quasars indicate that this circumgalactic medium extends far beyond the starlight seen in galaxies, but very little is known about its spatial distribution. The Lyman-alpha transition of atomic hydrogen at a wavelength of 121.6 nanometres is an important tracer of warm (about 104 kelvin) gas in and around galaxies, especially at cosmological redshifts greater than about 1.6 at which the spectral line becomes observable from the ground. Tracing cosmic hydrogen through its Lyman-a emission has been a long-standing goal of observational astrophysics(1-3), but the extremely low surface brightness of the spatially extended emission is a formidable obstacle. A new window into circumgalactic environments was recently opened by the discovery of ubiquitous extended Lyman-alpha emission from hydrogen around high-redshift galaxies(4,5). Such measurements were previously limited to especially favourable systems(6-8) or to the use of massive statistical averaging(9,10) because of the faintness of this emission. Here we report observations of low-surface-brightness Lyman-alpha emission surrounding faint galaxies at redshifts between 3 and 6. We find that the projected sky coverage approaches 100 per cent. The corresponding rate of incidence (the mean number of Lyman-alpha emitters penetrated by any arbitrary line of sight) is well above unity and similar to the incidence rate of high-column-density absorbers frequently detected in the spectra of distant quasars(11-14). This similarity suggests that most circumgalactic atomic hydrogen at these redshifts has now been detected in emission.