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Rashba spin-orbit coupling (RSOC) facilitates spin manipulation without relying on an external magnetic field, opening up exciting possibilities for advanced spintronic devices. In this work, we examine the effects of crystal momentum ($k$) nonlinearity and anisotropy on the conventional Rashba effect, with a particular focus on their impact on the spin Hall conductivity (SHC) in a newly predicted family of 2D Janus materials, W$_2$COX (X = S, Se, Te). Using first-principles density functional theory calculations, we confirm the dynamical and mechanical stability of the studied 2D materials. Strikingly, this materials family exhibits pronounced nonlinear Rashba spin splitting at the $\Gamma$ point of Brillouin zone near the Fermi level, which cannot be adequately described by the linear-$k$ Rashba model. Therefore, third-order momentum contributions ({$k^3$}) must be incorporated into the Rashba Hamiltonian. Our analysis reveals that among the studied systems, W$_2$COS exhibits the highest {$k^3$} contribution of $-45.9$\,eV\,{\AA$^3$}, despite having the lowest linear Rashba constant. A detailed analysis of electronic structure reveals topological nontrivial behaviour in these 2D materials, yielding sizable SHC that is primarily governed by the nonlinear Rashba effect. Notably, these materials also exhibit large spin Hall angle (0.018 -- 2.5), which is comparable to that of in bulk topological insulators like Bi$_2$Se$_3$ and Bi$_2$Te$_3$, and surpassing those in narrow bandgap bulk semiconductors GeTe and SnTe, as well as heavy metals such as Pt. Sizable SHC, large spin Hall angles, and the ability to tune SHC via electric fields without altering the topological properties, rooted in the crystal field splitting, underscore the potential of these materials for spintronic applications., Comment: 11 pages, 9 figures

Kagome metals are a unique class of quantum materials characterized by their distinct atomic lattice arrangement, featuring interlocking triangles and expansive hexagonal voids. These lattice structures impart exotic properties, including superconductivity, interaction-driven topological many-body phenomena, and magnetism, among others. The kagome metal CsM3Te5 (where M = Ti, Zr, or Hf) exhibits both superconductivity and nontrivial topological electronic properties, offering a promising platform for exploring topological superconductivity. This study employs first-principles density functional theory calculations to systematically analyze the elastic, mechanical, vibrational, thermodynamic, and electronic properties of CsM3Te5 (M = Ti, Zr, Hf). Our calculations reveal that the studied compounds - CsTi3Te5, CsZr3Te5, and CsHf3Te5 - are ductile metals with elastic properties akin to the hexagonal Bi and Sb, with average elastic constants, including a bulk modulus of 27 GPa, a shear modulus of 11 GPa, and Young's modulus of 29 GPa. We observe peculiar dispersionless, flat, phonon branches in the vibrational spectra of these metals. Additionally, we thoroughly analyze the symmetries of the zone-center phonon eigenvectors and predict vibrational fingerprints of the Raman- and infrared-active phonon modes. The analysis of thermodynamic properties reveals the Einstein temperature for CsTi3Te5, CsZr3Te5, and CsHf3Te5 to be 66, 54, and 53 K, respectively. Our orbital-decomposed electronic structure calculations reveal significant in-plane steric interactions and multiple Dirac band crossings near the Fermi level. We further investigate the role of spin-orbit coupling effect on the studied properties. This theoretical investigation sheds light on the intriguing quantum behaviour of kagome metals and provides valuable insights for their potential applications in future technologies., Comment: 10 pages, 8 figures

We present measurements of diffuse ultraviolet emission in the dwarf irregular galaxy Holmberg II obtained with the UltraViolet Imaging Telescope (UVIT) onboard AstroSat. With a spatial resolution of 1.2 to 1.6 arcsec, these are the highest resolution UV observations of the galaxy to date. We find that diffuse emission accounts for 70.6 % (58.1 %) of the total FUV(NUV) emission, respectively. We perform a UV-IR correlation study of the diffuse emission in this galaxy using infrared observations from Spitzer Space Telescope and Herschel Space Observatory for selected locations, free of detectable bright point sources. The strongest positive correlation between FUV and IR is observed at 70 micron for high HI density locations, indicating that warm dust grains dominate the IR emission, in agreement with earlier studies, while NUV is better correlated with 160 micron emission associated with cold dust grains. Low HI density regions or cavities, do not show any significant UV-IR correlation except at 160 micron, implying either the presence of colder dust grains in cavities, being irradiated by the general radiation field, or insufficient amount of dust. The dust scattering contribution in high HI density regions, estimated using a single scattering model with foreground dust clouds with LMC reddening, gives best-fit albedo and asymmetry factor values of 0.2 and 0.5, respectively, in reasonable agreement with the theoretical predictions for LMC dust. Our model derived scattering optical depths in the FUV range from 0.02 to 0.12, implying the medium is optically thin. Therefore, in high HI density regions, dust scattering can be one the sources of the observed diffuse UV emission, apart from possible contributions from molecular hydrogen fluorescence, However, the diffuse UV component in HI cavities can only be explained via other mechanisms, such as two photon emission., Comment: 25 pages, 11 figures

The Rashba spin-orbit coupling effect, primarily arising from structural-inversion asymmetry in periodic crystals, has garnered considerable attention due to its tunability and potential applications in spintronics. Its capability to manipulate electron spin without an external magnetic field opens new avenues for spintronic device design, particularly in semiconductor technology. Within this framework, 2D Rashba materials hold special interest due to their inherent characteristics, which facilitate miniaturization and engineering capabilities. In this Perspective article, we provide an overview of recent advancements in the research of 2D Rashba materials, aiming to offer a comprehensive understanding of the diverse manifestations and multifaceted implications of the Rashba effect in material science. Rather than merely presenting a list of materials, our approach involves synthesizing various viewpoints, assessing current trends, and addressing challenges within the field. Our objective is to bridge the gap between fundamental research and practical applications by correlating each material with the necessary advancements required to translate theoretical concepts into tangible technologies. Furthermore, we highlight promising avenues for future research and development, drawing from insights gleaned from the current state of the field.

Recent observations from the EIGER JWST program have measured for the first time the quasar-galaxy cross-correlation function at $z\approx6$. The auto-correlation function of faint $z\approx6$ quasars was also recently estimated. These measurements provide key insights into the properties of quasars and galaxies at high redshift and their relation with the host dark matter halos. In this work, we interpret these data building upon an empirical quasar population model that has been applied successfully to quasar clustering and demographic measurements at $z\approx2-4$. We make use of a new, large-volume N-body simulation with more than a trillion particles, FLAMINGO-10k, to model quasars and galaxies simultaneously. We successfully reproduce observations of $z\approx6$ quasars and galaxies (i.e., their clustering properties and luminosity functions), and infer key quantities such as their luminosity-halo mass relation, the mass function of their host halos, and their duty cycle/occupation fraction. Our key findings are: (i) quasars reside on average in $\approx10^{12.4}\,{\rm M}_\odot$ halos (corresponding to $\approx5\sigma$ fluctuations in the initial conditions of the linear density field), but the distribution of host halo masses is quite broad; (ii) the duty cycle of (UV-bright) quasar activity is relatively low ($\lesssim1\%$); (iii) galaxies (that are bright in [OIII]) live in much smaller halos ($\approx10^{10.9}\,{\rm M}_\odot$) and have a larger duty cycle (occupation fraction) of $\approx20\%$. Finally, we focus on the inferred properties of quasars and present a homogeneous analysis of their evolution with redshift. The picture that emerges reveals a strong evolution of the host halo mass and duty cycle of quasars at $z\approx2-6$, and calls for new investigations of the role of quasar activity across cosmic time., Comment: Submitted to MNRAS; 15 pages, 4 figures

We introduce the spin dissymmetry factor, a measure of the spin-selectivity in the optical transition rate of quantum particles. This spin dissymmetry factor is valid locally, including at material interfaces and within optical cavities. We design and numerically demonstrate an optical cavity with three-fold rotational symmetry that maximizes spin dissymmetry, thereby minimizing the spin dephasing of a cavity-coupled quantum particle. Our approach emphasizes the difference between spin and chirality in the nearfield and reveals a classical parameter for designing more efficient quantum optical devices., Comment: 11 pages, 1 figure, 1 table

We expect luminous ($M_{1450}\lesssim-26.5$) high-redshift quasars to trace the highest density peaks in the early universe. Here, we present observations of four $z\gtrsim6$ quasar fields using JWST/NIRCam in imaging and widefield slitless spectroscopy mode and report a wide range in the number of detected [OIII]-emitting galaxies in the quasars' environments, ranging between a density enhancement of $\delta\approx65$ within a $2$ cMpc radius - one of the largest proto-clusters during the Epoch of Reionization discovered to date - to a density contrast consistent with zero, indicating the presence of a UV-luminous quasar in a region comparable to the average density of the universe. By measuring the two-point cross-correlation function of quasars and their surrounding galaxies, as well as the galaxy auto-correlation function, we infer a correlation length of quasars at $\langle z\rangle=6.25$ of $r_0^{\rm QQ}=22.0^{+3.0}_{-2.9}~{\rm cMpc}\,h^{-1}$, while we obtain a correlation length of the [OIII]-emitting galaxies of $r_0^{\rm GG}=4.1\pm0.3~{\rm cMpc}\,h^{-1}$. By comparing the correlation functions to dark-matter-only simulations we estimate the minimum mass of the quasars' host dark matter halos to be $\log_{10}(M_{\rm halo, min}/M_\odot)=12.43^{+0.13}_{-0.15}$ (and $\log_{10}(M_{\rm halo, min}^{\rm [OIII]}/M_\odot) = 10.56^{+0.05}_{-0.03}$ for the [OIII]-emitters), indicating that (a) luminous quasars do not necessarily reside within the most overdense regions in the early universe, and that (b) the UV-luminous duty cycle of quasar activity at these redshifts is $f_{\rm duty}\ll1$. Such short quasar activity timescales challenge our understanding of early supermassive black hole growth and provide evidence for highly dust-obscured growth phases or episodic, radiatively inefficient accretion rates., Comment: ApJ accepted

Functional linear discriminant analysis (FLDA) is a powerful tool that extends LDA-mediated multiclass classification and dimension reduction to univariate time-series functions. However, in the age of large multivariate and incomplete data, statistical dependencies between features must be estimated in a computationally tractable way, while also dealing with missing data. There is a need for a computationally tractable approach that considers the statistical dependencies between features and can handle missing values. We here develop a multivariate version of FLDA (MUDRA) to tackle this issue and describe an efficient expectation/conditional-maximization (ECM) algorithm to infer its parameters. We assess its predictive power on the "Articulary Word Recognition" data set and show its improvement over the state-of-the-art, especially in the case of missing data. MUDRA allows interpretable classification of data sets with large proportions of missing data, which will be particularly useful for medical or psychological data sets.

We report {\em JWST}/NIRCam measurements of quasar host galaxy emissions and supermassive black hole (SMBH) masses for six quasars at $5.9

Holmberg II - a dwarf galaxy in the nearby M81 group - is a very informative source of distribution of gas and dust in the interstellar discs. High-resolution observations in the infrared (IR) allows us to distinguish isolated star-forming regions, photodissociation (PDR) and HII regions, remnants of supernovae (SNe) explosions and, as such, can provide information about more relevant physical processes. In this paper we analyse dust emission in the wavelength range 4.5 to 160 micron using the data from IR space observatories at 27 different locations across the galaxy. We observe that the derived spectra can be represented by multiple dust populations with different temperatures, which are found to be independent of their locations in the galaxy. By comparing the dust temperatures with the far ultraviolet (FUV) intensities observed by the UVIT instrument onboard AstroSat, we find that for locations showing a 100 micron peak, the temperature of cold (20 to 30 K) dust grains show a dependence on the FUV intensities, while such dependence is not observed for the other locations. We believe that the approach described here can be a good tool in revealing different dust populations in other nearby galaxies with available high spatial resolution data., Comment: 7 pages, 4 figures, submitted to Letters to MNRAS

The Galactic Center (GC) is surrounded by plasma lobes that extend up to ~14 kpc above and below the plane. Until now, UV absorption studies of these lobes have only focused on high-velocity components (|v_LSR| > 100 km/s) because low- and intermediate-velocity (LIV) components (|v_LSR| <100 km/s) are blended with foreground interstellar medium. To overcome this difficulty, we present a differential experiment to compare the LIV absorption between different structures within the GC region, including the Fermi Bubbles (FBs; seen in gamma-rays), the eROSITA Bubbles (eBs; seen in X-rays), and the Loop I North Polar Spur (LNPS) association, an X-ray and radio feature within the northern eB. We use far-UV spectra from Hubble Space Telescope to measure LIV Si IV absorption in 61 AGN sight lines, of which 21 pass through the FBs, 53 pass through the eBs, and 18 pass through the LNPS. We also compare our measurements to those in the literature from sight lines covering the disk-halo interface and CGM. We find that the FBs and eBs have enhancements in measured columns of 0.22-0.29 dex in log. We also remove the contribution of a modeled disk and CGM component from the measured Si IV columns and find that the northern eB still retains a Si IV enhancement of 0.62 dex in log. A similar enhancement is not seen in the southern eB. Since the LNPS model-subtracted residuals show an enhancement compared to the rest of the northern eB of 0.69 dex, the northern eB enhancement may be caused by the LNPS., Comment: Accepted for publication in ApJ

We report new observations of the cool diffuse gas around 29, $2.3$9. MgII absorption kinematics are shifted from the systemic redshift of host galaxies with a median absolute velocity of 135 km/s and standard deviation of 85 km/s. The high kinematic offset and large radial separation ($R> 1.3 R_{200}$), suggest that five out of the seven MgII absorption systems are gravitationally not bound to the galaxies. In contrast, most cool circumgalactic media at $z<1$ are gravitationally bound. The high incidence of unbound MgII gas in this work suggests that towards the end of reionization, galaxy halos are in a state of remarkable disequilibrium, and are highly efficient in enriching the intergalactic medium. Two strongest MgII absorption systems are detected at $z\sim$ 4.22 and 4.5, the former associated with a merging galaxy system and the latter associated with three kinematically close galaxies. Both these galaxies reside in local galaxy over-densities, indicating the presence of cool MgII absorption in two "proto-groups" at $z>4$., Comment: 23 pages, 12 figures, 4 tables, Accepted for publication in ApJ

We present the spatially resolved measurements of a cool galactic outflow in the gravitationally lensed galaxy RCS0327 at $z \approx 1.703$ using VLT/MUSE IFU observations. We probe the cool outflowing gas, traced by blueshifted Mg II and Fe II absorption lines, in 15 distinct regions of the same galaxy in its image-plane. Different physical regions, 5 to 7 kpc apart within the galaxy, drive the outflows at different velocities ($V_{out} \sim $ $-161$ to $-240$ km s$^{-1}$), and mass outflow rates ($\dot{M}_{out} \sim$ 183 to 527 $M_{\odot}\ yr^{-1}$). The outflow velocities from different regions of the same galaxy vary by 80 km s$^{-1}$, which is comparable to the variation seen in a large sample of star-burst galaxies in the local Universe. Using multiply lensed images of RCS0327, we probe the same star-forming region at different spatial scales (0.5 kpc$^2$-25 kpc$^2$), we find that outflow velocities vary between $ \sim $ $-120$ to $-242$ km s$^{-1}$, and the mass outflow rates vary between $\sim$ 37 to 254 $M_{\odot}\ yr^{-1}$. The outflow momentum flux in this galaxy is $\geq$ 100% of the momentum flux provided by star-formation in individual regions, and outflow energy flux is $\approx$ 10% of the total energy flux provided by star-formation. These estimates suggest that the outflow in RCS0327 is energy driven. This work shows the importance of small scale variations of outflow properties due to the variations of local stellar properties of the host galaxy in the context of galaxy evolution., Comment: 26 pages, 15 figures, 6 tables, accepted for publication in MNRAS, the referee comments are incorporated in this version

Characterising the prevalence and properties of faint active galactic nuclei (AGN) in the early Universe is key for understanding the formation of supermassive black holes (SMBHs) and determining their role in cosmic reionization. We perform a spectroscopic search for broad H$\alpha$ emitters at $z\approx4-6$ using deep JWST/NIRCam imaging and wide field slitless spectroscopy from the EIGER and FRESCO surveys. We identify 20 H$\alpha$ lines at $z=4.2-5.5$ that have broad components with line widths from $\sim1200-3700$ km s$^{-1}$, contributing $\sim30-90$ % of the total line flux. We interpret these broad components as being powered by accretion onto SMBHs with implied masses $\sim10^{7-8}$ M$_{\odot}$. In the UV luminosity range M$_{\rm UV}=-21$ to $-18$, we measure number densities of $\approx10^{-5}$ cMpc$^{-3}$. This is an order of magnitude higher than expected from extrapolating quasar UV luminosity functions. Yet, such AGN are found in only $<1$ % of star-forming galaxies at $z\sim5$. The SMBH mass function agrees with large cosmological simulations. In two objects we detect narrow red- and blue-shifted H$\alpha$ absorption indicative, respectively, of dense gas fueling SMBH growth and outflows. We may be witnessing early AGN feedback that will clear dust-free pathways through which more massive blue quasars are seen. We uncover a strong correlation between reddening and the fraction of total galaxy luminosity arising from faint AGN. This implies that early SMBH growth is highly obscured and that faint AGN are only minor contributors to cosmic reionization., Comment: 26 pages, 20 figures. Accepted for publication in ApJ. Various improvements and updated citations. Main additions: colours (Fig 11), broad Halpha LF (Fig 18, Sect 5.2), comparisons to simulations (Sect 5.3)

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., Comment: Published in Nature on 10 May 2023; authors' version; link to the paper: https://www.nature.com/articles/s41586-023-05901-3

Within the tumor microenvironment (TME), cancer cells use mechanotransduction pathways to convert biophysical forces to biochemical signals. However, the underlying mechanisms and functional significance of these pathways remain largely unclear. The upregulation of mechanosensitive pathways from biophysical forces such as interstitial flow, leads to the activation of various cytokines, most importantly transforming growth factor-$\beta$ (TGF-$\beta$). TGF-$\beta$ is a critical inducer of epithelial-mesenchymal transition (EMT) in cancer cells that leads to increased cell motility and invasion in a Smad dependent manner. Current research models have limited ability to investigate the combined effects of biophysical forces (such as interstitial flow) and cytokines (TGF-$\beta$) in a 3D microenvironment. We used a 3D-matrix based microfluidic platform to demonstrate the potentiating effect of interstitial flow (IF) on exogenous TGF-$\beta$ induced upregulation of the Smad-signaling activity and the expression of mesenchymal marker vimentin in A549 lung cancer spheroids. To monitor this, we used stably integrated fluorescent based reporters into the A549 cancer cell genome. Our results demonstrate that interstitial flow enhances exogenous TGF-$\beta$ induced Smad-signaling activity in lung cancer spheroids embedded in a matrix microenvironment. In addition, we observed an increased cell motility for A549 spheroids when exposed to interstitial flow and TGF-$\beta$. Our 3D-microfluidic model integrated with real-time imaging provides a powerful tool for investigating cancer cell signaling and motility associated with invasion characteristics in a physiologically relevant TME.

We combine datasets from the CGM$^{2}$ and CASBaH surveys to model a transition point, $R_{\rm cross}$, between circumgalactic and intergalactic media (CGM and IGM, respectively). In total, our data consist of 7244 galaxies at z < 0.5 with precisely measured spectroscopic redshifts, all having impact parameters of 0.01 - 20 comoving Mpc from 28 QSO sightlines with high-resolution UV spectra that cover H I Ly$\alpha$. Our best-fitting model is an exclusionary two-component model that combines a 3D absorber-galaxy cross correlation function with a simple Gaussian profile at inner radii to represent the CGM. By design, this model gives rise to a determination of $R_{\rm cross}$ as a function of galaxy stellar mass, which can be interpreted as the boundary between the CGM and IGM. For galaxies with $10^8 \leq M_{\star}/M_{\odot} \leq 10^{10.5}$, we find that $R_{\rm cross}(M_{\star}) \approx 2 \pm 0.6 R_{\rm vir}$. Additionally, we find excellent agreement between $R_{\rm cross}(M_{\star})$ and the theoretically-determined splashback radius for galaxies in this mass range. Overall, our results favor models of galaxy evolution at z < 0.5 that distribute $T \approx 10^{4}$K gas to distances beyond the virial radius., Comment: Submitted to ApJ, 17 pages, 8 figures

We present the first rest-frame optical spectrum of a high-redshift quasar observed with JWST/NIRCam in Wide Field Slitless (WFSS) mode. The observed quasar, J0100+2802, is the most luminous quasar known at $z>6$. We measure the mass of the central supermassive black hole (SMBH) by means of the rest-frame optical H$\beta$ emission line, and find consistent mass measurements of the quasar's SMBH of $M_\bullet\approx10^{10}\,M_\odot$ when compared to the estimates based on the properties of rest-frame UV emission lines CIV and MgII, which are accessible from ground-based observatories. To this end, we also present a newly reduced rest-frame UV spectrum of the quasar observed with X-Shooter/VLT and FIRE/Magellan for a total of 16.8 hours. We readdress the question whether this ultra-luminous quasar could be effected by strong gravitational lensing making use of the diffraction limited NIRCam images in three different wide band filters (F115W, F200W, F356W), which improves the achieved spatial resolution compared to previous images taken with the Hubble Space Telescope by a factor of two. We do not find any evidence for a foreground deflecting galaxy, nor for multiple images of the quasar, and determine the probability for magnification due to strong gravitational lensing with image separations below the diffraction limit of $\Delta\theta\lesssim 0.05''$ to be $\lesssim 2.2\times 10^{-3}$. Our observations therefore confirm that this quasar hosts a ten billion solar mass black hole less than $1$ Gyr after the Big Bang, which is challenging to explain with current black hole formation models., Comment: Accepted for publication in ApJ

We present emission-line measurements and physical interpretations for a sample of 117 [OIII] emitting galaxies at $z=5.33-6.93$, using the first deep JWST/NIRCam wide field slitless spectroscopic observations. Our 9.7-hour integration is centered upon the $z=6.3$ quasar J0100+2802 -- the first of six fields targeted by the EIGER survey -- and covers $\lambda=3-4$ microns. We detect 133 [OIII] doublets, but merge pairs within $\approx$10 kpc and 600 km s$^{-1}$, motivated by their small scale clustering excess. We detect H$\beta$ in 68 and H$\gamma$ emission in two galaxies. The galaxies are characterised by a UV luminosity M$_{\rm UV}\sim-19.6$ ($-17.7$ to $-22.3$), stellar mass ~$10^8$ $(10^{6.8-10.1})$ M$_{\odot}$, H$\beta$ and [OIII] EWs $\approx$ 850 Angstrom (up to 3000 Angstrom), young ages (~100 Myr), a highly excited interstellar medium ([OIII]/H$\beta\approx6$) and low dust attenuations. These high EWs are very rare in the local Universe, but we show they are ubiquitous at $z\sim6$ based on the measured number densities. The stacked spectrum reveals H$\gamma$ and [OIII]$_{4364}$ which shows that the galaxies are typically dust and metal poor (E(B-V)=0.1, 12+log(O/H)=7.4) with a high electron temperature ($2\times10^4$ K) and a production efficiency of ionising photons ($\xi_{\rm ion}=10^{25.3}$ Hz erg$^{-1}$). We further show the existence of a strong mass-metallicity relation. The young highly ionising stellar populations, moderately low metallicities, low dust attenuations and high ionisation state in z~6 galaxies conspire to maximise the [OIII] output from galaxies, yielding an [OIII] luminosity density at z~6 that is significantly higher than at z~2, despite the order of magnitude decline in cosmic star formation. Thus, [OIII] emission-line surveys with JWST prove a highly efficient method to trace the galaxy density in the epoch of reionization., Comment: Accepted for publication in ApJ. Main text 22 pages, 20 figures. Main results in Figs 14 (Xi_ion), 15 (MEx diagram),17 (MZR), 19 ([OIII] luminosity density)