199 research outputs found
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
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]3726,29 to
[SII]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_out2Msun/yr, the
low associated mass-loading factor, =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: 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< M1500<-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> 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] > 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
To high redshift and low mass: exploring the emergence of quenched galaxies and their environments at in the ultra-deep JADES MIRI F770W parallel
We present the robust selection of quiescent (QG) and post-starburst (PSB)
galaxies using ultra-deep NIRCam and MIRI imaging from the JWST Advanced Deep
Extragalactic Survey (JADES). Key to this is MIRI 7.7m imaging which
breaks the degeneracy between old stellar populations and dust attenuation at
by providing rest-frame -band. Using this, we identify 23 passively
evolving galaxies in UVJ color space in a mass-limited (log
) sample over 8.8 arcmin. Evaluation of this
selection with and without 7.7m shows that dense wavelength coverage
with NIRCam ( bands including medium-bands) can compensate for
lacking the band anchor, meaning that robust selection of high-redshift QGs
is possible with NIRCam alone. Our sample is characterized by rapid quenching
timescales ( Myr) with formation redshifts
and includes a potential record-holding massive QG at and two QGs with evidence for significant residual
dust content (). In addition, we present a large sample of 12
log PSBs, demonstrating that UVJ selection can be
extended to low mass. Analysis of the environment of our sample reveals that
the group known as the Cosmic Rose contains a massive QG and a dust-obscured
star-forming galaxy (a so-called Jekyll and Hyde pair) plus three additional
QGs within kpc. Moreover, the Cosmic Rose is part of a larger
overdensity at which contains 7/12 of our low-mass PSBs. Another 4
low-mass PSBs are members of an overdensity at ; this result strongly
indicates low-mass PSBs are preferentially associated with overdense
environments at .Comment: 27 pages, 10 figures, 2 tables (not including appendices or
references). Submitted to ApJ. Comments welcome
JADES: The emergence and evolution of Ly emission and constraints on the IGM neutral fraction
The rest-frame UV recombination emission line Ly can be powered by
ionising photons from young massive stars in star forming galaxies, but its
ability to be resonantly scattered by neutral gas complicates its
interpretation. For reionization era galaxies, a neutral intergalactic medium
(IGM) will scatter Ly from the line of sight, making Ly a
useful probe of the neutral fraction evolution. Here, we explore Ly 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 (), and thus represent a poorly-explored
class of galaxies. The low spectral resolution () spectra of a subset
of 84 galaxies in GOODS-S with (as derived with optical lines)
are fit with line and continuum models, in order to search for significant line
emission. Through exploration of the R100 data, we find evidence for Ly
in 17 sources. This sample allows us to place observational constraints on the
fraction of galaxies with Ly emission in the redshift range
, with a decrease from to . We also find a positive
correlation between Ly equivalent width and M, as seen in other
samples. These results are used to estimate the neutral gas fraction at
, agreeing with previous results ().Comment: 18 pages, 10 figures. Accepted for publication in A&
JADES: the emergence and evolution of Lyα 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  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
- …