Context. 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. Aims. We investigated the C II and dust morphology of a z ∼ 3.4 lensed galaxy hosting four clumps detected in the UV continuum. We aimed to observe the C II emission of individual clumps that, unlike the UV, is not affected by dust extinction, to probe their nature and cold gas content. Methods. We conducted ALMA observations probing scales down to ∼300 pc and detected three C II 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. Results. We converted the C II luminosity of individual clumps into molecular gas mass and found M mol ∼ 10 8 M ⊙ . By complementing it with the star formation rate (SFR) estimate from the UV continuum, we estimated the gas depletion time ( t dep ) of clumps and investigated their location in the Schmidt–Kennicutt plane. While the NE clump has a very short t dep = 0.16 Gyr, which is comparable with high-redshift starbursts, the SW and C clumps instead have longer t dep > 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 ( β ∼ −2.5) and it indicates that dust inhomogeneities do not significantly affect the detection of UV clumps in this target. Conclusions. 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.
ABSTRACT
The origin of the Lyman α (Lyα) emission in galaxies is a long-standing issue: despite several processes known to originate this line (e.g. active galactic nucleus, star formation, cold ...accretion, shock heating), it is difficult to discriminate among these phenomena based on observations. Recent studies have suggested that the comparison of the ultraviolet (UV) and optical properties of these sources could solve the riddle. For this reason, we investigate the rest-frame UV and optical properties of Abell 2895b, a strongly lensed Lyα emitter at redshift z ∼ 3.7. From this study, we find that our target is a compact (rn ∼ 1.2 pkpc) star-forming (star formation rate ≃11 M⊙ yr−1) galaxy having a young stellar population. Interestingly, we measure a high ratio of the Hβ and the UV continuum monochromatic luminosities (L(Hβ)/L(UV) ≃ 100). Based on tracks of theoretical stellar models (starburst99 and bpass), we can only partially explain this result by assuming a recent (≲10 Myr), bursty episode of star formation and considering models characterized by binary stars, a top-heavy initial mass function and subsolar metallicities (Z ≲ 0.01 Z⊙). These assumptions also explain the observed low (C/O) abundance of our target (≃0.23(C/O)⊙). By comparing the UV and optical data sets, we find that the Lyα and UV continuum are more extended (×2) than the Balmer lines, and that the peak of the Lyα is offset (≃0.6 pkpc). The multiwavelength results of our analysis suggest that the observed Lyα emission originates from a recent star formation burst, likely taking place in an off-centre clump.
ABSTRACT
Giant star-forming regions (clumps) are widespread features of galaxies at z ≈ 1−4. Theory predicts that they can play a crucial role in galaxy evolution, if they survive to stellar feedback ...for >50 Myr. Numerical simulations show that clumps’ survival depends on the stellar feedback recipes that are adopted. Up to date, observational constraints on both clumps’ outflows strength and gas removal time-scale are still uncertain. In this context, we study a line-emitting galaxy at redshift z ≃ 3.4 lensed by the foreground galaxy cluster Abell 2895. Four compact clumps with sizes ≲280 pc and representative of the low-mass end of clumps’ mass distribution (stellar masses ≲2 × 108 M⊙) dominate the galaxy morphology. The clumps are likely forming stars in a starbursting mode and have a young stellar population (∼10 Myr). The properties of the Lyman-α (Lyα) emission and nebular far-ultraviolet absorption lines indicate the presence of ejected material with global outflowing velocities of ∼200–300 km s−1. Assuming that the detected outflows are the consequence of star formation feedback, we infer an average mass loading factor (η) for the clumps of ∼1.8–2.4 consistent with results obtained from hydrodynamical simulations of clumpy galaxies that assume relatively strong stellar feedback. Assuming no gas inflows (semiclosed box model), the estimates of η suggest that the time-scale over which the outflows expel the molecular gas reservoir (≃7 × 108 M⊙) of the four detected low-mass clumps is ≲50 Myr.
ABSTRACT
We use a sample of 706 galaxies, selected as O iiλ3727 (O ii) emitters in the Survey for High-z Absorption Red and Dead Sources (SHARDS) on the CANDELS/GOODS-N field, to study the ...differential attenuation of the nebular emission with respect to the stellar continuum. The sample includes only galaxies with a counterpart in the infrared and log10(M*/M⊙) > 9, over the redshift interval 0.3 ≲ z ≲ 1.5. Our methodology consists in the comparison of the star formation rates inferred from O ii and Hα emission lines with a robust quantification of the total star-forming activity (SFR TOT) that is independently estimated based on both infrared and ultraviolet (UV) luminosities. We obtain $f\, =\, E(B-V)_{\mathrm{stellar}}$/E(B − V)nebular = 0.69$^{0.71}_{0.69}$ and 0.55$^{0.56}_{0.53}$ for O ii and Hα, respectively. Our resulting f-factors display a significant positive correlation with the UV attenuation and shallower or not-significant trends with the stellar mass, the SFRTOT, the distance to the main sequence, and the redshift. Finally, our results favour an average nebular attenuation curve similar in shape to the typical dust curve of local starbursts.
In this paper, we present a mathematical framework that permits a detailed performance analysis of Bluetooth connections in fading channels. Conversely to most part of the literature, we distinguish ...between the transmission of useful and duplicate frames, which are handled in a different manner by the receiving unit. To this end, we define a two-state Markov Chain and we apply the renewal reward theory to determine the expressions of the throughput, energy efficiency and delay performance of the link. Although the model can be applied to any version of Bluetooth specifications, as a proof of concept we provide an accurate performance analysis of an asymmetric Bluetooth v2.0+EDR (Enhanced Data Rate) connection in typical propagation environments. The analysis reveals that best performance are (almost) always obtained by using the longest baseband frames transmitted at 2Mbps in the low-to-medium signal-to-noise ratio (SNR) region, and at 3 Mbps in the high SNR region. Furthermore, we observed that it is more fruitful assigning the master role to the destination unit. The model, hence, proves to be a valuable tool to gain insights on the aspects that have a major impact on the system performance.
Context. Going from a redshift of 6 down to nearly 4, galaxies grow rapidly from low-mass galaxies towards the more mature types of massive galaxies seen at cosmic noon. Growth via gas accretion and ...mergers undoubtedly shape this evolution, however, there is considerable uncertainty at present over the contribution of each of these processes to the overall evolution of galaxies. Furthermore, previous characterisations of the morphology of galaxies in the molecular gas phase have been limited by the coarse resolution of earlier observations. Aims. In this work, we utilise new high-resolution ALMA CII observations to analyse three main sequence (MS) galaxy systems at a redshift of z ∼ 4.5 and at resolutions of up to 0.15″. This approach enables us to investigate the morphology and kinematics on a kpc scale and understand the processes at play as well as the classifications of galaxies at high resolution. Thanks to this unique window, we are able to gain insights into the molecular gas of MS galaxies undergoing mass assembly in the early Universe. Methods. We used intensity and velocity maps, position-velocity diagrams, and radial profiles of CII in combination with dust continuum maps to analyse the morphology and kinematics of the three systems. Results. In general, we find that the high-resolution ALMA data reveal more complex morpho-kinematic properties. For one galaxy in our sample, we identified interaction-induced clumps, demonstrating the profound effect that mergers have on the molecular gas in galaxies, which is consistent with what has been suggested by recent simulations. One galaxy that was previously classified as dispersion-dominated turned out to show two bright CII emission regions, which could either be classified as merging galaxies or massive star-forming regions within the galaxy itself. The high-resolution data for the other dispersion dominated object also revealed clumps of CII that had not been identified previously. Within the sample, we might also detect star-formation powered outflows (or outflows from active galactic nuclei) that appear to be fuelling diffuse gas regions and enriching the circumgalactic medium. The new high-resolution ALMA data we present in this paper reveal that the galaxies in our sample are much more complex than they previously appeared in the low-resolution ALPINE data. In particular, we find evidence of merger induced clumps in the galaxy DC8187, along with signs of merging components for the other two objects. This may be evidence that the number of mergers at high redshift are significantly underestimated at present.
Payments for Ecosystem Services (PES) have become a popular instrument in the last decades and this growing trend is also clearly evident in Brazil. However, challenges related to implementation of ...these schemes are often underestimated. Any guarantee that a payment will secure or provide such a service is subject not only to underlying ecological uncertainties but also to those entailed by the kinds of social interaction that are inherent to policy implementation. It is argued that the objectives proposed with these instruments can only be attained by ensuring a wide participation of land users. This article advances this topic reporting and discussing evidence on farmer's reasons to participate in three PES-water schemes in Brazil using a combination of qualitative and quantitative research approaches. Results indicate that the diverging opinions regarding how ecosystem services are generated or secured, decentralized governance structures and the involvement of representative bodies in scheme design and implementation are important factors to consider. Furthermore, access to information and general environmental concern were found to be important variables to explain the propensity of farmers to participate. This generates serious policy implications for developing consistent communication and consultation strategies with scheme beneficiaries.
•We employ quantitative and qualitative methods to analyze three PES schemes in Brazil.•Non-economic factors were found to be crucial for determining land use decisions about participating in PES.•Centralized governance achieves higher participation levels but can undermine trust building efforts.•Propensity to participate strongly increases with greater access to information for potential beneficiaries.•Findings suggest that communication tends to be overlooked in the Brazilian PES context.
We analyze how passive galaxies at z~ 1.5 populate the mass-size plane as a function of their stellar age, to understand if the observed size growth with time can be explained with the appearance of ...larger quenched galaxies at lower redshift. We use a sample of 32 passive galaxies extracted from the Wide Field Camera 3 Infrared Spectroscopic Parallel (WISP) survey with spectroscopic redshift 1.3 <, ~ z<, ~ 2.05, specific star formation rates lower than 0.01 Gyr super(-1), and stellar masses above 4.5 x 10 super(10)M sub(middot in circle). All galaxies have spectrally determined stellar ages from fitting of their rest-frame optical spectra and photometry with stellar population models. When dividing our sample into young (age < or =2.1 Gyr) and old (age >2.1 Gyr) galaxies we do not find a significant trend in the distributions of the difference between the observed radius and that predicted by the mass-size relation. This result indicates that the relation between the galaxy age and its distance from the mass-size relation, if it exists, is rather shallow, with a slope alpha > ~ -0.6. At face value, this finding suggests that multiple dry and/or wet minor mergers, rather than the appearance of newly quenched galaxies, are mainly responsible for the observed time evolution of the mass-size relation in passive galaxies.
Abstract We compared the effects of aversive and gentle handling in late pregnant ewes on fearfulness, heart rate variability and spatial learning in lambs. Twenty-four Norwegian -Dala ewes were ...studied. Ewes were subjected to gentle (i.e. soft talking and calm behavior) or aversive handling (i.e. swift movements and shouting) for 10 min twice a day during the last five weeks of pregnancy. Lambs from aversively (AVS) or gently (GEN) treated ewes were tested at 4 weeks of age. Lamb behavior was recorded during a) a human approach test, composed of 4 min of isolation and 4 min of exposure to an unfamiliar human, b) an umbrella startle test followed by 5-min recording, and c) two repetitions of a maze test. In addition, heart rate variability was recorded telemetrically before and after the human and startle tests. The baseline heart rate variability measures suggested a lower influence of vagal stimulation in AVS lambs. In the human approach test, AVS lambs vocalized and explored the environment less, and were slower to approach the human. They also tended to have higher flight distances during the startle test than the GEN lambs. The prenatal treatment had no significant effect in the maze test. In conclusion, we showed that aversive handling of pregnant ewes increased fearfulness and reduced vagal tone in their progeny compared to GEN lambs. These effects can have consequences for how lambs cope with rearing conditions.
Machine perfusion is increasingly utilized in liver transplantation to face the detrimental consequences of the use of extended-criteria donors. Hypothermic oxygenated machine perfusion (HOPE) ...appears to be more protective relative to static cold storage. Conversely, normothermic machine perfusion (NMP) allows a better graft evaluation. We describe a pilot prospective study on machine perfusion in selected grafts.
HOPE was executed for all the grafts procured from donors after cardiac death (DCDs) and for livers from donors after brain death (DBDs) requiring prolonged preservation time. NMP was used when a more precise evaluation was needed. Both HOPE and NMP were performed through the portal vein and hepatic artery.
From July 2016 to November 2017, we performed 7 HOPE procedures: 5 for DCD and 2 for DBD grafts. Two livers presented with macrovesicular steatosis >30% (1 DCD and 1 DBD). HOPE lasted 240 minutes (180–320 min) with a total ischemia time of 575 minutes (410–810 min). Six grafts were successfully transplanted. One DCD graft required additional evaluation using NMP. The graft was then discarded due to extensive hepatocellular necrosis. In the post-transplant course, acute and chronic renal failure were the main complications affecting 3 and 2 recipients, respectively. In our series, steatosis was the main risk factor for kidney injury. Patient and graft survival rate was 100% and no ischemic cholangiopathies were observed after 270 days (106–582 days).
Our study confirms HOPE safety and efficacy for DCD and DBD grafts. These data are particularly significant for DCD management in the Italian setting where the mandatory 20-minute hands-off interval before death declaration further prolongs warm ischemia time.
•HOPE reduces DCD-graft-related morbidity and prolongs preservation of liver DBD grafts.•HOPE protected our DCD livers with prolonged WIT and no major post-transplant complications occurred.•Prolonged DBD liver graft preservation was safely achieved in 2 cases using the HOPE procedure.•In our series, post-LT kidney injury was mainly related to steatosis rather than to the type of donor.
![Unveiling [C II] clumps in ...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/0004-6361/small "Unveiling [C II] clumps in a lensed star-forming galaxy at z ∼ 3.4")
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