ALMA hints at the presence of turbulent disk galaxies at z > 5

High-redshift galaxies are expected to be more turbulent than local galaxies because of their smaller size and higher star formation and thus stronger feedback from star formation, frequent mergers events, and gravitational instabilities. However, this scenario has recently been questioned by the observational evidence of a few galaxies at z~4-5 with a gas velocity dispersion similar to what is observed in the local population. Our goal is to determine whether galaxies in the first Gyrs of the Universe have already formed a dynamically cold rotating disk similar to the local counterparts. We studied the gas kinematic of 22 main-sequence star-forming galaxies at z > 5 and determined their dynamical state by estimating the ratio of the rotational velocity and of the gas velocity dispersion. We mined the ALMA archive and exploited the [CII] and [OIII] observations to perform a kinematic analysis of the cold and warm gas of z>5 main-sequence galaxies. The gas kinematics of the high-z galaxies is consistent within the errors with rotating but turbulent disks. We infer a velocity dispersion that is systematically higher by 4 times than the local galaxy population and the z~5 dust-obscured galaxies reported in the literature. The difference between our results and those reported at similar redshift can be ascribed to the systematic difference in the galaxy properties in the two samples: the disks of massive dusty galaxies are dynamically colder than the disks of dust-poor galaxies. The comparison with the theoretical predictions suggests that the main driver of the velocity dispersion in high-z galaxies is the gravitational energy that is released by the transport of mass within the disk. Finally, we stress that future deeper ALMA high-angular resolution observations are crucial to constrain the kinematic properties of high-z galaxies and to distinguish rotating disks from kpc-scale mergers.Comment: 14 pages, 11 figures, 1 tables, accepted for publication in A&

Dust attenuation law in JWST galaxies at z = 7-8

Attenuation curves in galaxies depend on dust chemical composition, content, and grain size distribution. Such parameters are related to intrinsic galaxy properties such as metallicity, star formation rate, and stellar age. Due to the lack of observational constraints at high redshift, dust empirical curves measured in the local Universe (e.g. Calzetti and SMC curves) have been employed to describe the dust attenuation at early epochs. We exploit the high sensitivity and spectral resolution of the JWST to constrain the dust attenuation curves in high-z galaxies. Our goals are to check whether dust attenuation curves evolve with redshift and quantify the dependence of the inferred galaxy properties on the assumed dust attenuation law. We develop a modified version of the SED fitting code BAGPIPES by including a detailed dust attenuation curve parametrization. Dust parameters are derived, along with galaxy properties, from the fit to the data from FUV to mm bands. Once applied to three star-forming galaxies at z = 7-8, we find that their attenuation curves differ from local templates. One out of three galaxies shows a characteristic MW bump, typically associated to the presence of small carbonaceous dust grains such as PAHs. This is one of the first evidences suggesting the presence of PAHs in early galaxies. Galaxy properties such as stellar mass and SFR inferred from SED fitting are strongly affected by the assumed attenuation curve, though the adopted star formation history also plays a major role. Our results highlight the importance of accounting for the potential diversity of dust attenuation laws when analyzing the properties of galaxies at the EoR, whose dust properties are still poorly understood. The application of our method to a larger sample of galaxies observed with JWST can provide us important insights into the properties of dust and galaxies in the early universe.Comment: 19 pages, 10 figure

Misexpression of a chloroplast aspartyl protease leads to severe growth defects and alters carbohydrate metabolism in Arabidopsis

The crucial role of carbohydrate in plant growth and morphogenesis is widely recognized. In this study, we describe the characterization of nana, a dwarf Arabidopsis (Arabidopsis thaliana) mutant impaired in carbohydrate metabolism. We show that the nana dwarf phenotype was accompanied by altered leaf morphology and a delayed flowering time. Our genetic and molecular data indicate that the mutation in nana is due to a transfer DNA insertion in the promoter region of a gene encoding a chloroplast-located aspartyl protease that alters its pattern of expression. Overexpression of the gene (oxNANA) phenocopies the mutation. Both nana and oxNANA display alterations in carbohydrate content, and the extent of these changes varies depending on growth light intensity. In particular, in low light, soluble sugar levels are lower and do not show the daily fluctuations observed in wild-type plants. Moreover, nana and oxNANA are defective in the expression of some genes implicated in sugar metabolism and photosynthetic light harvesting. Interestingly, some chloroplast-encoded genes as well as genes whose products seem to be involved in retrograde signaling appear to be down-regulated. These findings suggest that the NANA aspartic protease has an important regulatory function in chloroplasts that not only influences photosynthetic carbon metabolism but also plastid and nuclear gene expression

Aquatic Organic Matter in the Seine Basin: Sources, Spatio-Temporal Variability, Impact of Urban Discharges and Influence on Micro-pollutant Speciation

International audienc

Ultrasound Stimulation of Piezoelectric Nanocomposite Hydrogels Boosts Chondrogenic Differentiation in Vitro, in Both a Normal and Inflammatory Milieu

The use of piezoelectric nanomaterials combined with ultrasound stimulation is emerging as a promising approach for wirelessly triggering the regeneration of different tissue types. However, it has never been explored for boosting chondrogenesis. Furthermore, the ultrasound stimulation parameters used are often not adequately controlled. In this study, we show that adipose-tissue-derived mesenchymal stromal cells embedded in a nanocomposite hydrogel containing piezoelectric barium titanate nanoparticles and graphene oxide nanoflakes and stimulated with ultrasound waves with precisely controlled parameters (1 MHz and 250 mW/cm2, for 5 min once every 2 days for 10 days) dramatically boost chondrogenic cell commitment in vitro. Moreover, fibrotic and catabolic factors are strongly down-modulated: proteomic analyses reveal that such stimulation influences biological processes involved in cytoskeleton and extracellular matrix organization, collagen fibril organization, and metabolic processes. The optimal stimulation regimen also has a considerable anti-inflammatory effect and keeps its ability to boost chondrogenesis in vitro, even in an inflammatory milieu. An analytical model to predict the voltage generated by piezoelectric nanoparticles invested by ultrasound waves is proposed, together with a computational tool that takes into consideration nanoparticle clustering within the cell vacuoles and predicts the electric field streamline distribution in the cell cytoplasm. The proposed nanocomposite hydrogel shows good injectability and adhesion to the cartilage tissue ex vivo, as well as excellent biocompatibility in vivo, according to ISO 10993. Future perspectives will involve preclinical testing of this paradigm for cartilage regeneration

Bubbles and outflows. The novel JWST/NIRSpec view of the z = 1.59 obscured quasar XID2028

Quasar feedback in the form of powerful outflows is invoked as a key mechanism to quench star formation in galaxies, although direct observational evidence is still scarce and debated. Here we present Early Release Science JWST NIRSpec IFU observations of the z'='1.59 prototypical obscured Active Galactic Nucleus (AGN) XID2028: This target represents a unique test case for studying quasar feedback at the peak epoch of AGN-galaxy co-evolution because extensive multi-wavelength coverage is available and a massive and extended outflow is detected in the ionised and molecular components. With the unprecedented sensitivity and spatial resolution of the JWST, the NIRSpec dataset reveals a wealth of structures in the ionised gas kinematics and morphology that were previously hidden in the seeing-limited ground-based data. In particular, we find evidence of an interaction between the interstellar medium of the galaxy and the quasar-driven outflow and radio jet that produces an expanding bubble from which the fast and extended wind detected in previous observations emerges. The new observations confirm the complex interplay between the AGN jet, wind and the interstellar medium of the host galaxy, highlighting the role of low-luminosity radio jets in AGN feedback. They also clearly show the new window that NIRSpec opens for detailed studies of feedback at high redshift

GA-NIFS: co-evolution within a highly star-forming galaxy group at z=3.7 witnessed by JWST/NIRSpec IFS

We present NIRSpec IFS observations of a galaxy group around the massive GS_4891 galaxy at z=3.7 in GOODS-South that includes two other two systems, GS_4891_n to the north and GS_28356 to the east. These observations, obtained as part of the GTO GA-NIFS program, allow for the first time to study the spatially resolved properties of the interstellar medium (ISM) and ionized gas kinematics of a galaxy at this redshift. Leveraging the wide wavelength range spanned with the high-dispersion grating (with resolving power R=2700) observations, covering from [OII]$\lambda$$\lambda$3726,29 to [SII]$\lambda$$\lambda$6716,31, we explore the spatial distribution of star-formation rate, nebular attenuation and gas metallicity, together with the mechanisms responsible for the excitation of the ionized gas. GS_4891 presents a clear gradient of gas metallicity (as traced by 12 + log(O/H)) by more than 0.2dex from the south-east (where a star-forming clump is identified) to the north-west. The gas metallicity in the less-massive northern system, GS_4891_n, is also higher by 0.2 dex than at the center of GS_4891, suggesting that inflows of lower-metallicity gas might be favoured in higher-mass systems. The kinematic analysis shows that GS_4891 presents velocity gradients in the ionized gas consistent with rotation. The region between GS_4891 and GS_4891_n does not present high gas turbulence which, together with the difference in gas metallicities, suggests that these two systems might be in a pre-merger stage. Finally, GS_4891 hosts an ionized outflow that extends out to r_out=1.2 kpc from the nucleus and reaches maximum velocities v_out of approximately 400 km/s. Despite entraining an outflowing mass rate of M_out$\sim$2Msun/yr, the low associated mass-loading factor, $\eta$=0.05, implies that the outflow does not have a significant impact on the star-formation activity of the galaxy.Comment: Submitted to Astronomy & Astrophysics on September 25th, 202

JADES : the incidence rate and properties of galactic outflows in low-mass galaxies across 3 < z < 9*

We investigate the incidence and properties of ionised gas outflows in a sample of 52 galaxies with stellar masses between 107 M and 109 M observed with ultra-deep JWST/NIRSpec MSA spectroscopy as part of the JWST Advanced Deep Extragalactic Survey (JADES). The high-spectral resolution (R2700) NIRSpec observations allowed us to identify for the first time the potential signature of outflows in the rest-frame optical nebular lines in low-mass galaxies at z &gt; 4. The incidence fraction of ionised outflows, traced by broad components, is about 25–40%, depending on the intensity of the emission lines. The low incidence fraction might be due to both the sensitivity limit and the fact that outflows are not isotropic, but have a limited opening angle, which only results in detection when this is directed toward our line of sight. Evidence for outflows increases slightly with stellar mass and star formation rate. The median velocity and mass-loading factor (i.e. the ratio of the mass outflow rate and star formation rate) of the outflowing ionised gas are 350 km s−1 and η = 2.0+−1165, respectively. These are 1.5 and 100 times higher than the typical values observed in local dwarf galaxies. Some of these high-redshift outflows can escape the gravitational potential of the galaxy and dark matter halo and enrich the circumgalactic medium and possibly even the intergalactic medium. Our results indicate that outflows can significantly impact the star formation activity in low-mass galaxies within the first 2 Gyr of the Universe

JADES : the emergence and evolution of Ly α emission and constraints on the intergalactic medium neutral fraction

The rest-frame UV recombination emission line Lyα can be powered by ionising photons from young massive stars in star-forming galaxies, but the fact that it can be resonantly scattered by neutral gas complicates its interpretation. For reionisation-era galaxies, a neutral intergalactic medium will scatter Lyα from the line of sight, making Lyα a useful probe of the neutral fraction evolution. Here, we explore Lyα in JWST/NIRSpec spectra from the ongoing JADES programme, which targets hundreds of galaxies in the well-studied GOODS-S and GOODS-N fields. These sources are UV-faint (-20.4 &lt; MUV &lt;-16.4) and thus represent a poorly explored class of galaxy. We fitted the low spectral resolution spectra (R ∼ 100) of a subset of 84 galaxies in GOODS-S with zspec &gt; 5.6 (as derived with optical lines) with line and continuum models to search for significant line emission. Through exploration of the R100 data, we find evidence for Lyα in 17 sources. This sample allowed us to place observational constraints on the fraction of galaxies with Lyα emission in the redshift range 5.6 &lt; z &lt; 7.5, with a decrease from z = 6 to z = 7. We also find a positive correlation between the Lyα equivalent width and MUV, as seen in other samples. We used these results to estimate the neutral gas fraction at z ∼ 7, and our estimates are in agreement with previous results (XHI ∼ 0.5-0.9)

JADES: Probing interstellar medium conditions at z ∼ 5.5-9.5 with ultra-deep JWST/NIRSpec spectroscopy

We present emission-line ratios from a sample of 27 Lyman-break galaxies from z∼ 5.5-9.5 with-17.0&lt; M1500&lt;-20.4, measured from ultra-deep JWST/NIRSpec multi-object spectroscopy from the JWST Advanced Deep Extragalactic Survey (JADES). We used a combination of 28 h deep PRISM/CLEAR and 7 h deep G395M/F290LP observations to measure, or place strong constraints on, ratios of widely studied rest-frame optical emission lines including Hα, Hβ, [O II] λ3726, 3729, [Ne III] λ3869, [O III] λ4959, [O III] λ5007, [O I] λ6300, [N II] λ6583, and [S II] λ6716, 6731 in individual z&gt; 5.5 spectra. We find that the emission-line ratios exhibited by these z∼ 5.5-9.5 galaxies occupy clearly distinct regions of line-ratio space compared to typical z∼ 0-3 galaxies, instead being more consistent with extreme populations of lower-redshift galaxies. This is best illustrated by the [O III]/[O II] ratio, tracing interstellar medium (ISM) ionisation, in which we observe more than half of our sample to have [O III]/[O II] &gt; 10. Our high signal-to-noise spectra reveal more than an order of magnitude of scatter in line ratios such as [O II]/Hβ and [O III]/[O II], indicating significant diversity in the ISM conditions within the sample. We find no convincing detections of [N II] λ6583 in our sample, either in individual galaxies, or a stack of all G395M/F290LP spectra. The emission-line ratios observed in our sample are generally consistent with galaxies with extremely high ionisation parameters (log U∼-1.5), and a range of metallicities spanning from ∼0.1 × Z⊙ to higher than ∼0.3 × Z⊙, suggesting we are probing low-metallicity systems undergoing periods of rapid star formation, driving strong radiation fields. These results highlight the value of deep observations in constraining the properties of individual galaxies, and hence probing diversity within galaxy population