Abstract We present the initial sample of redshifts for 3839 galaxies in the MeerKAT DEEP2 field—the most sensitive ∼1.4 GHz radio field yet observed with σ n = 0.55 μ Jy beam −1 , reaching the ...confusion limit. Using a spectrophotometric technique combining coarse optical spectra with broadband photometry, we obtain redshifts with σ z ≲ 0.01(1 + z ), as determined from repeat observations. The resulting radio luminosity functions between 0.2 < z < 1.3 from our sample of 3839 individual galaxies are in remarkable agreement with those inferred from previous modeling of radio source counts, confirming a ≳50% excess in radio-based star formation rate density (SFRD) ( z ) measurements at 0.2 < z < 1.3 compared to those from the UV–IR. Several sources of systematic error are discussed—totalling ∼0.13 dex when added in quadrature. Even in the event that all systematic errors work to decrease the radio-based SFRD values, they are incapable of reconciling differences between the radio-based measurements with those from the UV–IR at 0.5 < z < 1.3. We conclude that significant work remains to have confidence in a full accounting of the star formation budget of the Universe.
We present evidence for very high gas fractions and extended molecular gas reservoirs in normal, near-infrared-selected (BzK) galaxies at z ∼ 1.5. Our results are based on multi-configuration CO2–1 ...observations obtained at the IRAM Plateau de Bure Interferometer. All six star-forming galaxies observed were detected at high significance. High spatial resolution observations resolve the CO emission in four of them, implying sizes of the gas reservoirs of order of 6–11 kpc and suggesting the presence of ordered rotation. The galaxies have UV morphologies consistent with clumpy, unstable disks, and UV sizes that are consistent with those measured in CO. The star formation efficiencies are homogeneously low within the sample and similar to those of local spirals—the resulting gas depletion times are ∼0.5 Gyr, much higher than what is seen in high-z submillimeter galaxies and quasars. The CO luminosities can be predicted to within 0.15 dex from the observed star formation rates (SFRs) and stellar masses, implying a tight correlation of the gas mass with these quantities. We use new dynamical models of clumpy disk galaxies to derive dynamical masses for our sample. These models are able to reproduce the peculiar spectral line shapes of the CO emission. After accounting for the stellar and dark matter masses, we derive molecular gas reservoirs with masses of (0.4–1.2)×1011 M☉. The implied conversion (CO luminosity-to-gas mass) factor is very high: αCO = 3.6 ± 0.8, consistent with a Galactic conversion factor but 4 times higher than that of local ultra-luminous IR galaxies that is typically used for high-redshift objects. The gas mass in these galaxies is comparable to or larger than the stellar mass, and the gas accounts for an impressive 50%–65% of the baryons within the galaxies' half-light radii. We are thus witnessing truly gas-dominated galaxies at z ∼ 1.5, a finding that explains the high specific SFRs observed for z > 1 galaxies. The BzK galaxies can be viewed as scaled-up versions of local disk galaxies, with low-efficiency star formation taking place inside extended, low-excitation gas disks. These galaxies are markedly different than local ULIRGs and high-z submillimeter galaxies and quasars, where higher excitation and more compact gas is found
The fraction of Lyman-α emitters (LAEs) among the galaxy population has been found to increase from z ~ 0 to z ~ 6 and drop dramatically at z> 6. This drop has been interpreted as an effect of an ...increasingly neutral intergalactic medium (IGM) with increasing redshift, while a Lyman continuum escape fraction evolving with redshift and/or a sudden change of galaxy physical properties can also contribute to the decreasing LAE fraction. We report the result of a large VLT/FORS2 program aiming to confirm spectroscopically a large galaxy sample at z ≥ 6 that has been selected in several independent fields through the Lyman break technique. Combining those data with archival data, we create a large and homogeneous sample of z ~ 6 galaxies (N = 127), complete in terms of Lyα detection at > 95% for Lyα equivalent width EW(Lyα) ≥ 25 Å. We use this sample to derive a new measurement of the LAE fraction at z ~ 6 and derive the physical properties of these galaxies through spectral energy distribution (SED) fitting. We find a median LAE fraction at z ~ 6 lower than in previous studies, while our sample exhibits typical properties for z ~ 6 galaxies in terms of UV luminosity and UVβ slope. The comparison of galaxy physical properties between LAEs and non-LAEs is comparable to results at lower redshift: LAEs with the largest EW(Lyα) exhibit bluer UV slopes, are slightly less massive and less star-forming. The main difference between LAEs and non-LAEs is that the latter are significantly dustier. Using predictions of our SED fitting code accounting for nebular emission, we find an effective Lyα escape fraction fesceff(Lyα) = 0.23-0.17+0.36 remarkably consistent with the value derived by comparing UV luminosity function with Lyα luminosity function. We conclude that the drop in the LAE fraction from z ~ 6 to z> 6 is less dramatic than previously found and the effect of an increasing IGM neutral fraction is possibly observed at 5 <z< 6. The processes driving the escape of Lyα photons at z ~ 6 are similar to those at lower redshifts and based on our derived fesceff(Lyα), we find that the IGM has a relatively small impact on Lyα photon visibility at z ~ 6, with a lower limit for the IGM transmission to Lyα photons, TIGM ≳ 0.20, likely due to the presence of outflows.
We use deep panchromatic data sets in the GOODS-N field, from GALEX to the deepest Herschel far-infrared (FIR) and VLA radio continuum imaging, to explore the evolution of star-formation activity and ...dust attenuation properties of star-forming galaxies to z Asymptotically = to 4, using mass-complete samples. Our main results can be summarized as follows: (i) the slope of the star-formation rate-M sub(*) correlation is consistent with being constant Asymptotically = to0.8 up to z Asymptotically = to 1.5, while its normalization keeps increasing with redshift; (ii) for the first time we are able to explore the FIR-radio correlation for a mass-selected sample of star-forming galaxies: the correlation does not evolve up to z Asymptotically = to 4; (iii) we confirm that galaxy stellar mass is a robust proxy for UV dust attenuation in star-forming galaxies, with more massive galaxies being more dust attenuated. Strikingly, we find that this attenuation relation evolves very weakly with redshift, with the amount of dust attenuation increasing by less than 0.3 mag over the redshift range 0.5-4 for a fixed stellar mass; (iv) the correlation between dust attenuation and the UV spectral slope evolves with redshift, with the median UV slope becoming bluer with redshift. By z Asymptotically = to 3, typical UV slopes are inconsistent, given the measured dust attenuations, with the predictions of commonly used empirical laws. (v) Finally, building on existing results, we show that gas reddening is marginally larger (by a factor of around 1.3) than the stellar reddening at all redshifts probed. Our results support a scenario where the ISM conditions of typical star-forming galaxies evolve with redshift, such that at z > or =, slanted 1.5 Main Sequence galaxies have ISM conditions moving closer to those of local starbursts.
We report the spectroscopic confirmation of two Lyman break galaxies at redshift >7. The galaxies were observed as part of an ultra-deep spectroscopic campaign with FORS2 at the ESO/VLT for the ...confirmation of z 7 'z-band dropout' candidates selected from our VLT/Hawk-I imaging survey. Both galaxies show a prominent emission line at 9735 A and 9858 A, respectively: the lines have fluxes of ~(1.6-1.2) X 10--17 erg s--1 cm--2 and exhibit a sharp decline on the blue side and a tail on the red side. The asymmetry is quantitatively comparable to the observed asymmetry in z ~ 6 Ly Delta *a lines, where absorption by neutral hydrogen in the intergalactic medium (IGM) truncates the blue side of the emission-line profile. We carefully evaluate the possibility that the galaxies are instead at lower redshift and we are observing either O II, O III, or H Delta *a emission: however from the spectroscopic and the photometric data we conclude that there are no other plausible identifications, except for Ly Delta *a at redshift >7, implying that these are two of the most robust redshift determination for galaxies in the reionization epoch. Based on their redshifts and broadband photometry, we derive limits on the star formation rate and on the ultraviolet spectral slopes of the two galaxies. We argue that these two galaxies alone are unlikely to have ionized the IGM in their surroundings.
We present the final results from our ultra-deep spectroscopic campaign with FORS2 at the ESO Very Large Telescope (VLT) for the confirmation of z 7 'z-band dropout' candidates selected from our ...VLT/Hawk-I imaging survey over three independent fields. In particular, we report on two newly discovered galaxies at redshift ~6.7 in the New Technology Telescope Deep Field. Both galaxies show an Ly Delta *a emission line with rest-frame equivalent widths (EWs) of the order of 15-20 A and luminosities of (2-4) X 1042 erg s--1. We also present the results of ultra-deep observations of a sample of i-dropout galaxies, from which we set a solid upper limit on the fraction of interlopers. Out of the 20 z-dropouts observed we confirm 5 galaxies at 6.6 < z < 7.1. This is systematically below the expectations drawn on the basis of lower redshift observations: in particular, there is a significant lack of objects with intermediate Ly Delta *a EWs (between 20 and 55 A). We conclude that the observed trend for the rising fraction of Ly Delta *a emission in Lyman break galaxies from z ~ 3 to z ~ 6 is most probably reversed from z ~ 6 to z ~ 7. Explaining the observed rapid change in the Ly Delta *a emitter fraction among the dropout population with reionization requires a fast evolution of the neutral fraction of hydrogen in the universe. Assuming that the universe is completely ionized at z = 6 and adopting a set of semi-analytical models, we find that our data require a change of the neutral hydrogen fraction of the order of in a time Delta *Dz ~ 1, provided that the escape fraction does not increase dramatically over the same redshift interval.
Domestic gardens collectively cover substantial areas within cities and play an important role in supporting urban biodiversity and ecosystem functioning. The extent of their contribution to urban ...biodiversity is ultimately determined by the attitudes, motivations, and practices of their owners. We identified variables characterizing individual householders and their properties that explained variation in perennial plant and avian species richness and plant diversity among 55 gardens in New Zealand. The size of the vegetated area was most important in explaining bird and plant diversity, independent of property size. Also important and positively associated with plant richness were socio-economic status and ability to discriminate between native and exotic species. Median housing age and neighborhood green space were less important. Contrary to expectations, better educated householders who demonstrated pro-environmental orientation (NEP) did not necessarily have gardens with greater plant diversity, however, people with higher NEP scores tended to have gardens with more structurally complex vegetation. Similar variables were important in explaining native and exotic species richness, but higher exotic plant diversity was associated with older people with smaller properties of lower value. Avian species richness increased primarily with vegetated area, but also the areas of beds and hedges. We demonstrate that although householder knowledge is an important determinant of garden biodiversity, vegetated area is most important. Promoting urban garden biodiversity requires that larger vegetated properties be supported and encouraged, and that planners should consider biodiversity when formulating policies, concerning garden size, property size, and consents that may result in a progressive increase in the proportion of built over/paved areas.
Using deep Herschel and ALMA observations, we investigate the star formation rate (SFR) distributions of X-ray-selected active galactic nucleus (AGN) host galaxies at 0.5 < z < 1.5 and 1.5 < z < 4, ...comparing them to that of normal, star-forming (i.e. ‘main-sequence’, or MS) galaxies. We find that 34–55 per cent of AGNs in our sample have SFRs at least a factor of 2 below that of the average MS galaxy, compared to ≈15 per cent of all MS galaxies, suggesting significantly different SFR distributions. Indeed, when both are modelled as lognormal distributions, the mass and redshift-normalized SFR distributions of X-ray AGNs are roughly twice as broad, and peak ≈0.4 dex lower, than that of MS galaxies. However, like MS galaxies, the normalized SFR distribution of AGNs in our sample appears not to evolve with redshift. Despite X-ray AGNs and MS galaxies having different SFR distributions, the linear-mean SFR of AGNs derived from our distributions is remarkably consistent with that of MS galaxies, and thus with previous results derived from stacked Herschel data. This apparent contradiction is due to the linear-mean SFR being biased by bright outliers, and thus does not necessarily represent a true characterization of the typical SFR of X-ray AGNs.
•HIPPL hormesis is mediated by salicylic acid, jasmonic acid and ethylene.•Glucanases and chitinases play a role in HIPPL induced resistance.•HIPPL delays tissue softening through the downregulation ...of polygalacturonase.•HIPPL and LIUV treatments elicit highly similar transcriptional changes.
Postharvest treatment of tomato fruit with high-intensity, pulsed polychromatic light (HIPPL) has previously been shown to induce delayed ripening and disease resistance comparable to that of low-intensity UV-C (LIUV). Little, however, is known of the mechanisms underpinning postharvest HIPPL hormesis in tomato fruit. Expression of genes involved in plant hormone biosynthesis, defence, secondary metabolism and ripening were monitored 24h post treatment (24 HPT), 10 d post treatment (10 DPT) and 12h post inoculation with Botrytis cinerea (12 HPI). All genes monitored were constitutively expressed and changes in expression profiles following treatment were highly similar for both HIPPL and LIUV treatments. Expression of pathogenesis-related proteins P4, β-1,3,-Glucanase and Chitinase 9 and a jasmonate biosynthesis enzyme (OPR3), were significantly upregulated at 10 DPT and 12 HPI. Both treatments significantly downregulated the expression of polygalacturonase and flavonol synthase at 10 DPT and 12 HPI. Ethylene biosynthesis enzyme ACO1 and β-carotene hydroxylase were significantly upregulated at 24 HPT, and phenylalanine ammonia-lyase (PAL) was significantly upregulated at 12 HPI. Both HIPPL and LIUV treatments stimulate defence responses that are mediated by salicylic acid, jasmonic acid and ethylene. This may lead to broad range resistance against both necrotrophic and biotrophic pathogens as well as abiotic stresses and herbivorous pests. Following inoculation with B. cinerea only PAL showed indication of a gene priming response for HIPPL- and LIUV-treated fruit.
Degraded land that is historically contaminated from different sources of industrial waste provides an opportunity for conversion to bioenergy fuel production and also to increase sequestration of ...carbon in soil through organic amendments. In pot experiments, As mobility was investigated in three different brownfield soils amended with green waste compost (GWC, 30% v/v) or biochar (BC, 20% v/v), planted with
Miscanthus. Using GWC improved crop yield but had little effect on foliar As uptake, although the proportion of As transferred from roots to foliage differed considerably between the three soils. It also increased dissolved carbon concentrations in soil pore water that influenced Fe and As mobility. Effects of BC were less pronounced, but the impacts of both amendments on SOC, Fe, P and pH are likely to be critical in the context of As leaching to ground water. Growing
Miscanthus had no measurable effect on As mobility.
Green waste compost enhances water-soluble iron, phosphorus and carbon, increasing arsenic mobility in soil pore water.
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