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In this work, we devise a model for estimating UV and optical line emission (i.e., CIII] $1909$A, H$\beta$, [OIII] $5007$A, H$\alpha$, [NII] $6583$A) tracing HII regions in the interstellar medium (ISM) of galaxies at $z\sim4-6$ from the ALMA Large Programme ALPINE. The aim is to investigate the impact of binary stars in the stellar population along with an abrupt quenching in the Star Formation History (SFH) on line emission. This is crucial for understanding the ISM's properties in early galaxies and identifying new star formation tracers in high-$z$ galaxies. The model simulates HII+Photodissociation Region (PDR) complexes through radiative transfer in 1D slabs, characterized by gas density ($n$), ionisation parameter ($U$), and metallicity ($Z$). It considers: (a) heating from star formation (SF), simulated with Starburst99 and BPASS to quantify binary stars impact; (b) constant, exponentially declining, and quenched SFH scenarios. For each galaxy, we select theoretical ratios from CLOUDY models between [CII] line emission, tracing PDRs, and nebular lines from HII regions, using these to derive expected optical/UV lines from observed [CII]. We find binary stars strongly impact line emission post-quenching, keeping UV photon flux higher for longer, maintaining free electron temperature and ionised column density in HII regions up to 5 Myr after quenching. We constrain ISM properties of our subsample, finding a low ionisation parameter $\log U{\approx}-3.8\pm 0.2$ and moderate/high densities $\log(n/\rm cm^{-3}){\approx}2.9\pm 0.6$. Finally, we derive UV/optical line luminosities-SFR relations for different burstiness parameters ($k_s$). In the fiducial BPASS model, relations show negligible SFH dependence but depend on $k_s$, while in the SB99 case, dependence is on SFH. We propose their use for characterising the burstiness of high-$z$ galaxies., Comment: 14 pages, 8 figures. Accepted for publication in A&A

We aim at characterizing the X-ray-to-optical/near-infrared broad-band emission of luminous QSOs in the first Gyr of cosmic evolution to understand whether they exhibit differences compared to the lower-\textit{z} QSO population. Our goal is also to provide for these objects a reliable and uniform catalog of SED fitting derivable properties such as bolometric and monochromatic luminosities, Eddington ratios, dust extinction, strength of the hot dust emission. We characterize the X-ray/UV emission of each QSO using average SEDs from luminous Type 1 sources and calculate bolometric and monochromatic luminosities. Finally we construct a mean SED extending from the X-rays to the NIR bands. We find that the UV-optical emission of these QSOs can be modelled with templates of $z\sim$2 luminous QSOs. We observe that the bolometric luminosities derived adopting some bolometric corrections at 3000 \AA\ ($BC_{3000\text{\AA}}$) largely used in the literature are slightly overestimated by 0.13 dex as they also include reprocessed IR emission. We estimate a revised value, i.e. $BC_{3000\text{\AA}}=3.3 $ which can be used for deriving $L_\text{bol}$ in \textit{z} $\geq$ 6 QSOs. A sub-sample of 11 QSOs is provided with rest-frame NIR photometry, showing a broad range of hot dust emission strength, with two sources exhibiting low levels of emission. Despite potential observational biases arising from non-uniform photometric coverage and selection biases, we produce a X-ray-to-NIR mean SED for QSOs at \textit{z} $\gtrsim$ 6, revealing a good match with templates of lower-redshift, luminous QSOs up to the UV-optical range, with a slightly enhanced contribution from hot dust in the NIR.

One of the main open questions in the field of luminous ($L_{\rm bol}>10^{47}\,\rm erg\,s^{-1}$) quasars (QSOs) at $z \gtrsim 6$ is the rapid formation ($< 1\,$Gyr) of their supermassive black holes (SMBHs). For this work we analysed the relation between the X-ray properties and other properties describing the physics and growth of both the accretion disc and the SMBH in QSOs at the Epoch of Reionization (EoR). The sample consists of 21 $z>6$ QSOs, which includes 16 sources from the rapidly grown QSOs from the HYPERION sample and five other luminous QSOs with available high-quality archival X-ray data. We discovered a strong and statistically significant ($>3\sigma$) relation between the X-ray continuum photon index ($\Gamma$) and the $\rm C\,IV$ disc wind velocity ($v_{\rm C\,IV}$) in $z>6$ luminous QSOs, whereby the higher the $v_{\rm C\,IV}$, the steeper the $\Gamma$. This relation suggests a link between the disc-corona configuration and the kinematics of disc winds. Furthermore, we find evidence at $>2-3\sigma$ level that $\Gamma$ and $v_{\rm C\,IV}$ are correlated to the growth rate history of the SMBH. Although additional data are needed to confirm it, this result may suggest that, in luminous $z>6$ QSOs, the SMBH predominantly grows via fast accretion rather than via initial high seed BH mass., Comment: Accepted for publication in Astronomy & Astrophysics

Galaxy evolution emerges from the balance between cosmic gas accretion, fueling star formation, and supernova (SN) feedback, regulating the metal enrichment. Hence, the stellar mass ($M_*$) - gas metallicity relation (MZR) is key to understand the physics of galaxies. High-quality JWST data enable accurate measurements of the MZR up to redshift z=10. Our aims are to understand the observed MZR, its connection with the star formation rate (SFR), the role played by SFR stochasticity, and how it is regulated by SN feedback. We compare the MZR from the JADES, CEERS, and UNCOVER surveys, which comprise about 180 galaxies at $z=3-10$ with $10^6

Galaxy protoclusters are sites of rapid growth, with a high density of massive galaxies driving elevated rates of star formation and accretion onto supermassive black holes. Here, we present new JWST/NIRSpec IFU observations of the J1000+0234 group at $z=4.54$, a dense region of a protocluster hosting a massive, dusty star forming galaxy (DSFG). The new data reveal two extended, high-equivalent-width (EW$_0>1000\r{A}$) [O III] nebulae that appear at both sides of the DSFG along its minor axis (namely O3-N and O3-S). On one hand, the spectrum of O3-N shows a broad and blueshifted component with a full width at half maximum (FWHM) of 1300 km/s, suggesting an outflow origin. On the other hand, O3-S stretches over 8.6 kpc, and has a velocity gradient that spans 800 km/s, but shows no evidence of a broad component. However, both sources seem to be powered by an active galactic nucleus (AGN), so we classified them as extended emission-line regions (EELRs). The strongest evidence comes from the detection of the high-ionization [Ne V] $\lambda 3427$ line toward O3-N, which paired with the lack of hard X-rays implies an obscuring column density above the Compton-thick regime. The [Ne V] line is not detected in O3-S, but we measure a He II $\lambda 4687$/H$\beta$=0.25, which is well above the expectation for star formation. Despite the remarkable alignment of O3-N and O3-S with two radio sources, we do not find evidence of shocks from a radio jet that could be powering the EELRs. We interpret this as O3-S being externally irradiated by the AGN, akin to the famous Hanny's Voorwerp object in the local Universe. In addition, classical line ratio diagnostics (e.g., [O III]/H$\beta$ vs [N II]/H$\alpha$) put the DSFG itself in the AGN region of the diagrams, and therefore suggest it to be the most probable AGN host. These results showcase the ability of JWST to unveil obscured AGN at high redshifts., Comment: 13 pages, 10 figures, and one table. Accepted for publication in A&A on November 12th 2024

Context. Although dust in galaxies represents only a few percent of the total baryonic mass, it plays a crucial role in the physical processes occurring in galaxies. Studying the dust content of galaxies, particularly at high$-z$, is therefore crucial to understand the link between dust production, obscured star formation and the build-up of galaxy stellar mass. Aims. To study the dust properties (mass and temperature) of the largest Atacama Large Millimeter/submillimeter Array (ALMA)-selected sample of star-forming galaxies available from the archive (A$^3$COSMOS) and derive the dust mass function and dust mass density of galaxies from $z=0.5\,-\,6$. Methods. We performed spectral energy distribution (SED) fitting with the CIGALE code to constrain the dust mass and temperature of the A$^3$COSMOS galaxy sample, thanks to the UV-to-near-infrared photometric coverage of each galaxies combined with the ALMA (and Herschel when available) coverage of the Rayleigh-Jeans tail of their dust-continuum emission. We then computed and fitted the dust mass function by combining the A$^3$COSMOS and state-of-the-art {\it Herschel} samples, in order to obtain the best estimate of the integrated dust mass density up to $z \sim 6$. Results. Galaxies in \a3 have dust masses between $\sim 10^8$ and $\sim 10^{9.5}$ M$_{\odot}$. From the SED fitting, we were also able to derive a dust temperature, finding that the distribution of the dust temperature peaks at $\sim 30-35$K. The dust mass function at $z=0.5\,-\,6$ evolves with an increase of $M^*$ and decrease of the number density ($\Phi ^*$) and is in good agreement with literature estimates. The dust mass density shows a smooth decrease in its evolution from $z \sim 0.5$ to $z \sim 6$, which is steeper than what is found by models at $z \gtrsim 2$., Comment: 11 pages, 9 figures, Accepted for publication on A&A

Measurements of the size of dust continuum emission are an important tool for constraining the spatial extent of star formation and hence the build-up of stellar mass. Compact dust emission has generally been observed at Cosmic Noon (z~2-3). However, at earlier epochs, toward the end of the Reionization (z~4-6), only the sizes of a handful of IR-bright galaxies have been measured. In this work, we derive the dust emission sizes of main-sequence galaxies at z~5 from the ALPINE survey. We measure the dust effective radius r_e,FIR in the uv-plane in Band 7 of ALMA for seven ALPINE galaxies with resolved emission and we compare it with rest-frame UV and [CII]158$\mu$m measurements. We study the r_e,FIR-L_IR scaling relation by considering our dust size measurements and all the data in literature at z~4-6. Finally, we compare our size measurements with predictions from simulations. The dust emission in the selected ALPINE galaxies is rather extended (r_e,FIR~1.5-3 kpc), similar to [CII]158 um but a factor of ~2 larger than the rest-frame UV emission. Putting together all the measurements at z~5, spanning 2 decades in luminosity from L_IR ~ 10^11 L_sun to L_IR ~ 10^13 L_sun, the data highlight a steeply increasing trend of the r_e,FIR-L_IR relation at L_IR< 10^12 L_sun, followed by a downturn and a decreasing trend at brighter luminosities. Finally, simulations that extend up to the stellar masses of the ALPINE galaxies considered in the present work predict a sub-set of galaxies (~25% at 10^10 M_sun < M_star < 10^11 M_sun) with sizes as large as those measured., Comment: 8 pages, Accepted by A&A

The study of gas-phase metallicity and its spatial distribution at high redshift is crucial to understand the processes that shaped the growth and evolution of galaxies in the early Universe. Here we study the spatially resolved metallicity in three systems at $z\sim6-8$, namely A2744-YD4, BDF-3299, and COSMOS24108, with JWST NIRSpec IFU low-resolution ($R\sim100$) spectroscopic observations. These are among the highest-$z$ sources in which metallicity gradients have been probed so far. Each of these systems hosts several spatial components in the process of merging within a few kpc, identified from the rest-frame UV and optical stellar continuum and ionised gas emission line maps. The sources have heterogeneous properties, with stellar masses log($M_*/M_\odot) \sim 7.6-9.3$, star formation rates (SFRs) $\sim1-15$ $M_\odot$ yr$^{-1}$, and gas-phase metallicities 12+log(O/H) $\sim 7.7-8.3$, which exhibit a large scatter within each system. Their properties are generally consistent with those of the highest-$z$ samples to date ($z\sim3-10$), though the sources in A2744-YD4 and COSMOS24108 are at the high end of the mass-metallicity relation (MZR) defined by the $z\sim3-10$ sources. Moreover, the targets in this work follow the predicted slope of the MZR at $z\sim 6-8$ from most cosmological simulations. The gas-phase metallicity gradients are consistent with being flat in the main sources of each system. Flat metallicity gradients are thought to arise from gas mixing processes on galaxy scales, such as mergers or galactic outflows and SN winds driven by intense stellar feedback, which wash out any gradient formed in the galaxy. The existence of flat gradients at $z\sim6-8$ sets also important constraints on cosmological simulations and chemical evolution models, whose predictions on the cosmic evolution of metallicity gradients differ significantly, but are mostly limited to $z<3$ so far., Comment: 15 pages (+5 appendix); 7 figures (+8 in appendix); in production on A&A

Observations at UV and optical wavelengths have revealed that galaxies at z~1-4 host star-forming regions, dubbed "clumps", which are believed to form due to the fragmentation of gravitationally unstable, gas-rich disks. However, the detection of the parent molecular clouds that give birth to such clumps is still possible only in a minority of galaxies, mostly at z~1. We investigated the [CII] and dust morphology of a z~3.4 lensed galaxy hosting four clumps detected in the UV continuum. We aimed to observe the [CII] emission of individual clumps that, unlike the UV, is not affected by dust extinction, to probe their nature and cold gas content. We conducted ALMA observations probing scales down to ~300 pc and detected three [CII] clumps. One (dubbed "NE") coincides with the brightest UV clump, while the other two ("SW" and "C") are not detected in the UV continuum. We do not detect the dust continuum. We converted the [CII] luminosity of individual clumps into molecular gas mass and found Mmol~10^8 Msun. By complementing it with the star formation rate (SFR) estimate from the UV continuum, we estimated the gas depletion time (tdep) of clumps and investigated their location in the Schmidt-Kennicutt plane. While the NE clump has a short tdep=0.16 Gyr, comparable with high-redshift starbursts, the SW and C clumps instead have longer tdep>0.65 Gyr and are likely probing the initial phases of star formation. The lack of dust continuum detection is consistent with the blue UV continuum slope estimated for this galaxy (beta~-2.5) and it indicates that dust inhomogeneities do not significantly affect the detection of UV clumps in this target. We pushed the observation of the cold gas content of individual clumps up to z~3.4 and showed that the [C II] line emission is a promising tracer of molecular clouds at high redshift, allowing the detection of clumps with a large range of depletion times., Comment: Accepted for publication in A&A

The Kennicutt-Schmidt (KS) relation between the gas and the star formation rate (SFR) surface density ($\Sigma_{\rm gas}$-$\Sigma_{\rm SFR}$) is essential to understand star formation processes in galaxies. So far, it has been measured up to z~2.5 in main-sequence galaxies. In this letter, we aim to put constraints at z~4.5 using a sample of four massive main-sequence galaxies observed by ALMA at high resolution. We obtained ~0.3"-resolution [CII] and continuum maps of our objects, which we then converted into gas and obscured SFR surface density maps. In addition, we produced unobscured SFR surface density maps by convolving Hubble ancillary data in the rest-frame UV. We then derived the average $\Sigma_{\rm SFR}$ in various $\Sigma_{\rm gas}$ bins, and estimated the uncertainties using a Monte Carlo sampling. Our galaxy sample follows the KS relation measured in main-sequence galaxies at lower redshift and is slightly lower than predictions from simulations. Our data points probe the high end both in terms of $\Sigma_{\rm gas}$ and $\Sigma_{\rm gas}$, and gas depletion timescales (285-843 Myr) remain similar to z~2 objects. However, three of our objects are clearly morphologically disturbed, and we could have expected shorter gas depletion timescales (~100 Myr) similar to merger-driven starbursts at lower redshifts. This suggests that the mechanisms triggering starbursts at high redshift may be different than in the low- and intermediate-z Universe., Comment: 9 pages, 7 figures, 2 tables, accepted by A&A (letter)

The existence of luminous quasars (QSO) at the Epoch of Reionization (EoR; i.e. z>6) powered by supermassive black holes (SMBH) with masses $\gtrsim10^9~M_\odot$ challenges models of early SMBH formation. To shed light on the nature of these sources we started a multiwavelength programme based on a sample of 18 HYPerluminous quasars at the Epoch of ReionizatION (HYPERION). These are the luminous QSOs whose SMBH must have had the fastest mass growth during the Universe first Gyr. In this paper we present the HYPERION sample and report on the first of the 3 years planned observations of the 2.4 Ms XMM-Newton Multi-Year Heritage program on which HYPERION is based. The goal of this program is to accurately characterize the X-ray nuclear properties of QSOs at the EoR. Through a joint X-ray spectral analysis of 10 sources, in the rest-frame $\sim2-50$ keV range, we report a steep average photon index ($\Gamma\sim2.4\pm0.1$). Absorption is not required. The average $\Gamma$ is inconsistent at $\geq4\sigma$ level with the canonical 1.8-2 value measured in QSO at z<6. This spectral slope is also much steeper than that reported in lower-z QSOs with similar luminosity or accretion rate, thus suggesting a genuine redshift evolution. Alternatively, we can interpret this result as the presence of an unusually low-energy cutoff $E_{cut}\sim20$ keV on a standard $\Gamma=1.9$ power-law. We also report on mild indications that HYPERION QSOs show higher soft X-ray emission at 2 keV compared to the UV one at 2500A than expected by lower-z luminous AGN. We speculate that a redshift-dependent coupling between the corona and accretion disc or intrinsically different coronal properties may account for the steep spectral slopes, especially in the presence of powerful winds. The reported slopes, if confirmed at lower luminosities, may have an important impact on future X-ray AGN studies in the early Universe., Comment: 21 pages (including appendix), 12 figures, 4 tables. Accepted for pubblication in A&A

Line ratio diagnostics provide valuable clues on the source of ionizing radiation in galaxies with intense black hole accretion and starbursting events, such as local Seyfert or galaxies at the peak of the star formation history. We aim to provide a reference joint optical and mid-IR analysis for studying AGN identification via line ratios and testing predictions from photoionization models. We obtained homogenous optical spectra with the Southern Africa Large Telescope for 42 Seyfert galaxies with Spitzer/IRS spectroscopy and X-ray to mid-IR multiband data available. After confirming the power of the main optical ([OIII]) and mid-IR ([NeV], [OIV], [NeIII]) emission lines in tracing AGN activity, we explore diagrams based on ratios of optical and mid-IR lines by exploiting photoionization models of different ionizing sources (AGN, star formation and shocks). We find that pure AGN photoionization models are good at reproducing observations of Seyfert galaxies with an AGN fractional contribution to the mid-IR (5-40 micron) emission larger than 50 per cent. For targets with a lower AGN contribution these same models do not fully reproduce the observed mid-IR line ratios. Mid-IR ratios like [NeV]/[NeII], [OIV]/[NeII] and [NeIII]/[NeII] show a dependence on the AGN fractional contribution to the mid-IR unlike optical line ratios. An additional source of ionization, either from star formation or radiative shocks, can help explain the observations in the mid-IR. Among combinations of optical and mid-IR diagnostics in line ratio diagrams, only those involving the [OI]/Halpha ratio are promising diagnostics for simultaneously unraveling the relative role of AGN, star formation and, shocks. A proper identification of the dominant ionizing source would require the exploitation of analysis tools based on advanced statistical techniques as well as spatially resolved data., Comment: 31 pages, 15 figures, 2 tables. Accepted for publication in A&A

Recent attempts to detect [OIII] 88$\mu$m emission from super-early ($z>10$) galaxy candidates observed by JWST have been unsuccessful. By using zoom-in simulations, we show that these galaxies are faint, and mostly fall below the local metal-poor $\rm [OIII]-SFR$ relation as a result of their low ionization parameter, $U_{\rm ion}\lesssim 10^{-3}$. Such low $U_{\rm ion}$ values are found in galaxies that are in an early assembly stage, and whose stars are still embedded in high-density natal clouds. However, the most luminous galaxy in our sample ($\rm{log}[L_{\rm{[OIII]}}/L_\odot] = 8.4$, $U_{\rm ion} \approx 0.1$) could be detected by ALMA in only $2.8$ hrs., Comment: 6 pages, 3 figures, Submitted to MNRAS (comments are welcome)

In the submm regime, spectral line scans and line intensity mapping (LIM) are new promising probes for the cold gas content and star formation rate of galaxies across cosmic time. However, both of these two measurements suffer from field-to-field variance. We study the effect of field-to-field variance on the predicted CO and [CII] power spectra from future LIM experiments such as CONCERTO, as well as on the line luminosity functions (LFs) and the cosmic molecular gas mass density that are currently derived from spectral line scans. We combined a 117 $\rm deg^2$ dark matter lightcone from the Uchuu cosmological simulation with the simulated infrared dusty extragalactic sky (SIDES) approach. We find that in order to constrain the CO LF with an uncertainty below 20%, we need survey sizes of at least 0.1 $\rm deg^2$. Furthermore, accounting for the field-to-field variance using only the Poisson variance can underestimate the total variance by up to 80%. The lower the luminosity is and the larger the survey size is, the higher the level of underestimate. At $z$<3, the impact of field-to-field variance on the cosmic molecular gas density can be as high as 40% for the 4.6 arcmin$^2$ field, but drops below 10% for areas larger than 0.2 deg$^2$. However, at $z>3$ the variance decreases more slowly with survey size and for example drops below 10% for 1 deg$^2$ fields. Finally, we find that the CO and [CII] LIM power spectra can vary by up to 50% in $\rm 1 deg^2$ fields. This limits the accuracy of the constraints provided by the first 1 deg$^2$ surveys. The level of the shot noise power is always dominated by the sources that are just below the detection thresholds. We provide an analytical formula to estimate the field-to-field variance of current or future LIM experiments. The code and the full SIDES-Uchuu products (catalogs, cubes, and maps) are publicly available.

GDS J033218.92-275302.7 (here GS-14) is a $z\sim5.5$ galaxy detected in [CII] as part of the ALPINE survey with unusual UV spectral features that have been interpreted as signatures of either a double stellar population or of an active galactic nucleus (AGN). We exploited the multi-wavelength coverage of GS-14 to investigate the properties and the origin of its emission. We performed UV-to-NIR SED-fitting, with single/double stellar population and/or AGN component. We analyzed the VIMOS spectrum, which shows highly-ionized emission lines (Ovi, Nv, and Niv). The line properties have been compared with those observed in galaxies and AGN, and with the predictions from radiation transfer models for star-forming galaxies, AGN, and shocks. The SED-fitting provides a total stellar mass of $M_*=(4 \pm 1) \times 10^{10} M_\odot$, an age of the main stellar population of $\sim670 Myr$ and a recent short (8 Myr) burst of star formation (SF) of $\sim 90 M_\odot yr^{-1}$. The Nv line has a characteristic P-Cygni profile, which suggests a $\sim 3 Myr$ old population of stars with a mass of $\sim 5 \times10^{7} M_\odot$. The Nv profile also shows evidence for an additional component of nebular emission. The comparison of the line ratios with theoretical models allows us to associate the emission with SF or AGN, but the strong radiation field required to ionize the Ovi is more commonly related to AGN activity. We found evidence for an old and already evolved stellar population at $z\sim 5.5$ and show that the galaxy is experiencing a second short burst of SF. In addition, GS-14 carries signatures of obscured AGN activity. The AGN could be responsible for the short depletion time of this galaxy, thus making GS-14 one of the two ALPINE sources with hints of an active nucleus and an interesting target for future follow-ups., Comment: Accepted in A&A, 10 pages, 4 figures

We present a new prediction of the luminosity functions of the [CII] line at 158 $\mu$m, of the CO lines from J=0 to J=24, and of the molecular gas mass density up to z=10, using the Spectro-Photometric Realisations of Infrared-selected Targets at all-z (SPRITZ) simulation (Bisigello et al. 2021). We update the state-of-the-art phenomenological simulation SPRITZ to include both the CO ($J\leq24$) and [CII] line luminosities. This has been performed using different empirical and theoretical relations to convert the total infrared luminosity (or star formation rate) to [CII] or CO luminosity. The resulting line luminosity functions have been compared for validation with a large set of observations available in the literature. We then used the derived CO and [CII] line luminosities to estimate the molecular gas mass density and compare it with available observations. The CO and [CII] luminosity functions presented here are well in agreement with all the available observations. In particular, the best results for [CII] are obtained deriving the [CII] luminosity directly from the star formation rate, but considering a dependence of this relation on the gas metallicity. For all the CO luminosity functions, the estimates favoured by the data are derived considering different relations, depending on the ionisation mechanism dominating each galaxy, i.e. star formation or active galactic nuclei, and, moreover, deriving the $J\geq4$ CO lines directly from the [CII] luminosity. However, further data are necessary to fully discriminate between models. Finally, the best agreement with observations of the molecular gas mass density are derived by converting the [CII] luminosity to H2 mass, using a [CII]-to-H2 conversion ~130 $\rm M_{\odot}/{\rm L}_{\odot}$. All the line luminosity functions, useful for planning and interpreting future observations, are made publicly available., Comment: 18 pages, 16 figures, 8 tables, accepted for publication in A&A

The outstanding mass growth of supermassive black holes (SMBHs) at the Reionisation Epoch and how it is related to the concurrent growth of their host galaxies, poses challenges to theoretical models aimed at explaining how these systems formed in short timescales (<1 Gyr). To trace the average evolutionary paths of quasi-stellar objects (QSOs) and their host galaxies in the BH mass-host mass ($M_{\rm dyn}$) plane, we compare the star formation rate (SFR), derived from the accurate estimate of the dust temperature and the dust mass ($T_{\rm dust}, M_{\rm dust}$), with the BH accretion rate. To this aim, we analysed a deep, $900$ pc resolution ALMA observation of the sub-mm continuum, [CII] and H$_2$O of the $z\sim 6$ QSO J2310+1855, enabling a detailed study of dust properties and cold gas kinematics. We performed an accurate SED analysis obtaining a dust temperature of $T_{\rm dust} = 71$ K and a dust mass of $M_{\rm dust}= 4.4 \times 10^8\ \rm M_{\odot}$. The implied AGN-corrected SFR is $1240 \ \rm M_{\odot}yr^{-1}$, a factor of 2 smaller than previously reported for this QSO. We derived the best estimate of the dynamical mass $M_{\rm dyn} = 5.2\times 10^{10}\ \rm M_{\odot}$ within $r = 1.7$ kpc, based on a dynamical model of the system. We found that ${\rm SFR}/M_{\rm dyn}>\dot M_{\rm BH}/M_{\rm BH}$, suggesting that AGN feedback might be efficiently acting to slow down the SMBH accretion, while the stellar mass assembly is still vigorously taking place in the host galaxy. In addition, we were also able to detect high-velocity emission on the red and blue sides of the [CII] emission line, that traces a gaseous outflow, and for the first time, we mapped a spatially-resolved water vapour disk through the H$_2$O v=0 $3_{(2,2)}-3_{(1,3)}$ emission line detected at $\nu_{\rm obs} = 274.074$ GHz, whose kinematic properties and size are broadly consistent with those of the [CII] disk., Comment: 15 pages, 10 figures, 4 tables. Accepted in A&A

The intensity mapping of the [CII] 158um line redshifted to the sub-mm window is a promising probe of the z>4 star formation and its spatial distribution into the large-scale structure. To prepare the first-generation experiments (e.g., CONCERTO), we need realistic simulations of the sub-mm extragalactic sky in spectroscopy. We present a new version of the SIDES simulation including the main sub-mm lines around 1mm (CO, [CII], [CI]). This approach successfully reproduces the observed line luminosity functions. We then use our simulation to generate CONCERTO-like cubes (125-305GHz) and forecast the power spectra of the fluctuations caused by the various astrophysical components at those frequencies. Depending on our assumptions on the relation between star formation rate and [CII] luminosity, and the star formation history, our predictions of the z~6 [CII] power spectrum vary by two orders of magnitude. This highlights how uncertain the predictions are and how important future measurements will be to improve our understanding of this early epoch. SIDES can reproduce the CO shot noise recently measured at ~100 GHz by the mmIME experiment. Finally, we compare the contribution of the different astrophysical components at various redshift to the power spectra. The continuum is by far the brightest, by a factor of 3 to 100 depending on the frequency. At 300GHz, the CO foreground power spectrum is higher than the [CII] one for our base scenario. At lower frequency, the contrast between [CII] and extragalactic foregrounds is even worse. Masking the known galaxies from deep surveys should allow to reduce the foregrounds to 20% of the [CII] power spectrum up to z~6.5. However, this masking method will not be sufficient at higher redshifts. The code and the products of our simulation are released publicly and can be used for both intensity mapping experiments and sub-mm continuum and line surveys., Comment: 28 pages, 19 figures, 2 tables, accepted by A&A, the code and the products are available at https://cesamsi.lam.fr/instance/sides/home

The characterization of the dynamical state of galaxies up to z~7 is crucial for constraining the mechanisms driving the mass assembly in the early Universe. However, it is unclear whether the data quality of current and future observations is sufficient to perform a solid dynamical analysis. This paper defines the angular resolution and S/N required for a robust characterization of the dynamical state of galaxies up to the EoR. The final aim is to help design spatially-resolved surveys targeting emission lines of primeval galaxies. We investigate the [CII]-158um emission from z~6-7 LBGs from the SERRA cosmological simulation, covering a range of dynamical states: from disks to major mergers. We create ALMA mock observations with various data quality and apply the kinematic classification methods used in the literature. These tests allow us to quantify the performances of such methods as a function of angular resolution and S/N. We find that barely-resolved observations do not allow the correct dynamical characterization of a galaxy, resulting in the misclassification of all disks in our sample. However, even when using spatially-resolved observations with data quality typical of high-z galaxies, the standard kinematic classification methods, based on the analysis of the moment maps, fail to distinguish a merger from a disk. The high angular resolution and S/N needed to apply these standard methods successfully can be achieved with current data only for a handful of bright galaxies. We propose a new classification method, called PVsplit, that quantifies the asymmetries and morphological features in position-velocity diagrams using three empirical parameters. We test PVsplit on our mock data concluding that it can predict whether a galaxy is a disk or a merger provided that S/N $\gtrsim10$, and the major axis is covered by $\gtrsim3$ independent resolution elements., Comment: Submitted to Astronomy and Astrophysics (A&A) Journal. Comments are welcome

We introduce SERRA, a suite of zoom-in high-resolution ($\sim 10\,\rm pc$) cosmological simulations including non-equilibrium chemistry and on-the-fly radiative transfer. The outputs are post-processed to derive galaxy UV+FIR continuum and emission line properties. Results are compared with available multi-wavelength data to constrain the physical properties (e.g., star formation rates, stellar/gas/dust mass, metallicity) of high-redshift $6 \lesssim z \lesssim 15$ galaxies. This flagship paper focuses on the $z=7.7$ sub-sample, including 202 galaxies with stellar mass $10^7 M_\odot \lesssim M_\star \lesssim 5\times 10^{10}M_\odot$, and specific star formation ranging from ${\rm sSFR} \sim 100\,{\rm Gyr}^{-1}$ in young, low-mass galaxies to $\sim 10\,{\rm Gyr}^{-1}$ for older, massive ones. At this redshift, SERRA galaxies are typically bursty, i.e. they are located above the Schmidt-Kennicutt relation by a factor $\kappa_s = 3.03^{+4.9}_{-1.8}$, consistent with recent findings for [OIII] and [CII] emitters at high-$z$. They also show relatively large ${\rm IRX} = L_{\rm FIR}/L_{\rm UV}$ values as a result of their compact/clumpy morphology effectively blocking the stellar UV luminosity. Note that this conclusion might be affected by insufficient spatial resolution at the molecular cloud level. We confirm that early galaxies lie on the standard $\rm [CII]-SFR$ relation; their observed $L_{\rm [OIII]}/L_{\rm [CII]} \simeq 1-10$ ratios can be reproduced by a part of the SERRA galaxies without the need of a top-heavy IMF and/or anomalous C/O abundances. [OI] line intensities are similar to local ones, making ALMA high-$z$ detections challenging but feasible ($\sim 6\,\rm hr$ for a SFR of $50\,M_\odot\,{\rm yr}^{-1}$)., Comment: 23 pages, 14 figures, accepted by MNRAS; part of the data used for this study is available at the website http://cosmology.sns.it/data_access.html