We report the detection of a CO emission line from the submillimeter galaxy (SMG) GN10 in the GOODS-N field. GN10 lacks any counterpart in extremely deep optical and near-IR imaging obtained with the ...Hubble Space Telescope and ground-based facilities. This is a prototypical case of a source that is extremely obscured by dust, for which it is practically impossible to derive a spectroscopic redshift in the optical/near-IR. Under the hypothesis that GN10 is part of a proto-cluster structure previously identified at z ~ 4.05 in the same field, we searched for CO4-3 at 91.4 GHz with the IRAM Plateau de Bure Interferometer, and successfully detected a line. We find that the most likely redshift identification is z = 4.0424 ± 0.0013, based on: (1) the very low chance that the CO line is actually serendipitous from a different redshift; (2) a radio-IR photometric redshift analysis; (3) the identical radio-IR spectral energy distribution, within a scaling factor of 2 other SMGs at the same redshift. The faintness at optical/near-IR wavelengths requires an attenuation of A V ~ 5-7.5 mag. This result supports the case that a substantial population of very high-z SMGs exists that had been missed by previous spectroscopic surveys. This is the first time that a CO emission line has been detected for an SMG that is invisible in the optical and near-IR. Our work demonstrates the power of existing and planned facilities for completing the census of star formation and stellar mass in the distant universe by measuring redshifts of the most obscured galaxies through millimeter spectroscopy.
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
Whereas osmotic stress response induced by solutes has been well-characterized in fungi, less is known about the other activities of environmentally ubiquitous substances. The latest methodologies to ...define, identify and quantify chaotropicity, i.e. substance-induced destabilization of macromolecular systems, now enable new insights into microbial stress biology (Cray et al. in Curr Opin Biotechnol 33:228–259, 2015a, doi: 10.1016/j.copbio.2015.02.010 ; Ball and Hallsworth in Phys Chem Chem Phys 17:8297–8305, 2015, doi: 10.1039/C4CP04564E ; Cray et al. in Environ Microbiol 15:287–296, 2013a, doi: 10.1111/1462-2920.12018). We used Aspergillus wentii, a paradigm for extreme solute-tolerant fungal xerophiles, alongside yeast cell and enzyme models (Saccharomyces cerevisiae and glucose-6-phosphate dehydrogenase) and an agar-gelation assay, to determine growth-rate inhibition, intracellular compatible solutes, cell turgor, inhibition of enzyme activity, substrate water activity, and stressor chaotropicity for 12 chemically diverse solutes. These stressors were found to be: (i) osmotically active (and typically macromolecule-stabilizing kosmotropes), including NaCl and sorbitol; (ii) weakly to moderately chaotropic and non-osmotic, these were ethanol, urea, ethylene glycol; (iii) highly chaotropic and osmotically active, i.e. NH₄NO₃, MgCl₂, guanidine hydrochloride, and CaCl₂; or (iv) inhibitory due primarily to low water activity, i.e. glycerol. At ≤0.974 water activity, Aspergillus cultured on osmotically active stressors accumulated low-M ᵣ polyols to ≥100 mg g dry weight⁻¹. Lower-M ᵣ polyols (i.e. glycerol, erythritol and arabitol) were shown to be more effective for osmotic adjustment; for higher-M ᵣ polyols such as mannitol, and the disaccharide trehalose, water-activity values for saturated solutions are too high to be effective; i.e. 0.978 and 0.970 (25 ºC). The highly chaotropic, osmotically active substances exhibited a stressful level of chaotropicity at physiologically relevant concentrations (20.0–85.7 kJ kg⁻¹). We hypothesized that the kosmotropicity of compatible solutes can neutralize chaotropicity, and tested this via in-vitro agar-gelation assays for the model chaotropes urea, NH₄NO₃, phenol and MgCl₂. Of the kosmotropic compatible solutes, the most-effective protectants were trimethylamine oxide and betaine; but proline, dimethyl sulfoxide, sorbitol, and trehalose were also effective, depending on the chaotrope. Glycerol, by contrast (a chaotropic compatible solute used as a negative control) was relatively ineffective. The kosmotropic activity of compatible solutes is discussed as one mechanism by which these substances can mitigate the activities of chaotropic stressors in vivo. Collectively, these data demonstrate that some substances concomitantly induce chaotropicity-mediated and osmotic stresses, and that compatible solutes ultimately define the biotic window for fungal growth and metabolism. The findings have implications for the validity of ecophysiological classifications such as ‘halophile’ and ‘polyextremophile’; potential contamination of life-support systems used for space exploration; and control of mycotoxigenic fungi in the food-supply chain.
Nitrogen fertilization is considered as an important source of atmospheric N₂O emission. A seven site-year on-farm field experiment was conducted at Ottawa and Guelph, ON and Saint-Valentin, QC, ...Canada to characterize the affect of the amount and timing of N fertilizer on N₂O emission in corn (Zea mays L.) production. Using the static chamber method, gas samples were collected for 28-days after preplant and 28-days after sidedress fertilization at the seven site-year, resulting in 14 monitoring periods. For both methods of fertilization, peak N₂O flux and cumulative emission increased with the amount of N applied, with rates ranging from 30 to 900 μg N m⁻² h⁻¹. Depending on N amount and time of application, cumulative emission varied from 0.05 to 2.42 kg N ha⁻¹, equivalent to 0.03% to 1.45% of the N fertilizer applied. Differences in N₂O emission peaks among fertilizer treatments were clearly separated in 13 out of 14 monitoring periods. Total N₂O emissions may have been underestimated compared with annual monitoring in 10 out of the 49 cases because the monitoring period ended before N₂O efflux returned to the baseline level. The flux of N₂O was negligible when soil mineral N in the 0-15 cm layer was < 20 mg N kg⁻¹. While rainfall stimulated emission, soil temperature > 15 °C was likely the driving force responsible for the higher levels of N₂O found for sidedress than preplant application methods. However, caution must be taken when interpreting these later results as preplant fertilization may have continuously stimulated N₂O emissions after the 28-days monitoring period, especially in situations where N₂O effluxes have not fallen back to their baseline levels. Increasing fertilizer rates from 90 to 150 kg N ha⁻¹ resulted in slight increases in yields, but doubled cumulative N₂O emissions.
We present a multi-wavelength, UV-to-radio analysis for a sample of massive (M{sub *} {approx} 10{sup 10} M{sub sun}) IRAC- and MIPS 24 {mu}m detected Lyman break galaxies (LBGs) with spectroscopic ...redshifts z {approx} 3 in the GOODS-North field. For LBGs without individual 24 {mu}m detections, we employ stacking techniques at 24 {mu}m, 1.1 mm, and 1.4 GHz to construct the average UV-to-radio spectral energy distribution and find it to be consistent with that of a luminous infrared galaxy with L{sub IR} = 4.5{sup +1.1}{sub -2.3} x 10{sup 11} L{sub sun} and a specific star formation rate of 4.3 Gyr{sup -1} that corresponds to a mass doubling time {approx}230 Myr. On the other hand, when considering the 24 {mu}m detected LBGs we find among them galaxies with L{sub IR}>10{sup 12} L{sub sun}, indicating that the space density of z {approx} 3 UV-selected ultra-luminous infrared galaxies (ULIRGs) is {approx}(1.5 {+-} 0.5) x 10{sup -5} Mpc{sup -3}. We compare measurements of star formation rates from data at different wavelengths and find that there is tight correlation (Kendall's {tau}>99.7%) and excellent agreement between the values derived from dust-corrected UV, mid-IR, millimeter, and radio data for the whole range of L{sub IR} up to L{sub IR} {approx} 10{sup 13} L{sub sun}. This range is greater than that for which the correlation is known to hold at z {approx} 2, possibly due to the lack of significant contribution from polycyclic aromatic hydrocarbons to the 24 {mu}m flux at z {approx} 3. The fact that this agreement is observed for galaxies with L{sub IR}>10{sup 12} L{sub sun} suggests that star formation in UV-selected ULIRGs, as well as the bulk of star formation activity at this redshift, is not embedded in optically thick regions as seen in local ULIRGs and submillimeter-selected galaxies at z = 2.
We present a high-resolution (down to 0.''18), multi-transition imaging study of the molecular gas in the z = 4.05 submillimeter galaxy GN20. GN20 is one of the most luminous starburst galaxy known ...at z>4, and is a member of a rich proto-cluster of galaxies at z = 4.05 in GOODS-North. We have observed the CO 1-0 and 2-1 emission with the Very Large Array (VLA), the CO 6-5 emission with the Plateau de Bure Interferometer, and the 5-4 emission with Combined Array for Research in Millimeter Astronomy. The H{sub 2} mass derived from the CO 1-0 emission is 1.3 x 10{sup 11}({alpha}/0.8) M{sub sun}. High-resolution imaging of CO 2-1 shows emission distributed over a large area, appearing as partial ring, or disk, of {approx}10 kpc diameter. The integrated CO excitation is higher than found in the inner disk of the Milky Way, but lower than that seen in high-redshift quasar host galaxies and low-redshift starburst nuclei. The CO 4-3 integrated line strength is more than a factor of 2 lower than expected for thermal excitation. The excitation can be modeled with two gas components: a diffuse, lower excitation component with a radius {approx}4.5 kpc and a filling factor {approx}0.5, and a more compact, higher excitation component (radius {approx}2.5 kpc, filling factor {approx}0.13). The lower excitation component contains at least half the molecular gas mass of the system, depending on the relative conversion factor. The VLA CO 2-1 image at 0.''2 resolution shows resolved, clumpy structure, with a few brighter clumps with intrinsic sizes {approx}2 kpc. The velocity field determined from the CO 6-5 emission is consistent with a rotating disk with a rotation velocity of {approx}570 km s{sup -1} (using an inclination angle of 45{sup 0}), from which we derive a dynamical mass of 3 x 10{sup 11} M{sub sun} within about 4 kpc radius. The star formation distribution, as derived from imaging of the radio synchrotron and dust continuum, is on a similar scale as the molecular gas distribution. The molecular gas and star formation are offset by {approx}1'' from the Hubble Space Telescope I-band emission, implying that the regions of most intense star formation are highly dust obscured on a scale of {approx}10 kpc. The large spatial extent and ordered rotation of this object suggests that this is not a major merger, but rather a clumpy disk accreting gas rapidly in minor mergers or smoothly from the proto-intracluster medium. Qualitatively, the kinematic and structural properties of GN20 compare well to the most rapid star formers fed primarily by cold accretion in cosmological hydrodynamic simulations. Conversely, if GN20 is a major, gas-rich merger, then some process has managed to ensure that the star formation and molecular gas distribution has not been focused into one or two compact regions.
We present the deepest 100 to 500 μm far-infrared observations obtained with the Herschel Space Observatory as part of the GOODS-Herschel key program, and examine the infrared (IR) 3–500 μm spectral ...energy distributions (SEDs) of galaxies at 0 < z < 2.5, supplemented by a local reference sample from IRAS, ISO, Spitzer, and AKARI data. We determine the projected star formation densities of local galaxies from their radio and mid-IR continuum sizes. We find that the ratio of total IR luminosity to rest-frame 8 μm luminosity, IR8 (≡ LIRtot), follows a Gaussian distribution centered on IR8 = 4 (σ = 1.6) and defines an IR main sequence for star-forming galaxies independent of redshift and luminosity. Outliers from this main sequence produce a tail skewed toward higher values of IR8. This minority population (<20%) is shown to consist of starbursts with compact projected star formation densities. IR8 can be used to separate galaxies with normal and extended modes of star formation from compact starbursts with high–IR8, high projected IR surface brightness (ΣIR > 3 × 1010 L⊙ kpc-2) and a high specific star formation rate (i.e., starbursts). The rest-frame, UV-2700 Å size of these distant starbursts is typically half that of main sequence galaxies, supporting the correlation between star formation density and starburst activity that is measured for the local sample. Locally, luminous and ultraluminous IR galaxies, (U)LIRGs (LIRtot), are systematically in the starburst mode, whereas most distant (U)LIRGs form stars in the “normal” main sequence mode. This confusion between two modes of star formation is the cause of the so-called “mid-IR excess” population of galaxies found at z > 1.5 by previous studies. Main sequence galaxies have strong polycyclic aromatic hydrocarbon (PAH) emission line features, a broad far-IR bump resulting from a combination of dust temperatures (Tdust ~ 15–50 K), and an effective Tdust ~ 31 K, as derived from the peak wavelength of their infrared SED. Galaxies in the starburst regime instead exhibit weak PAH equivalent widths and a sharper far-IR bump with an effective Tdust ~ 40 K. Finally, we present evidence that the mid-to-far IR emission of X-ray active galactic nuclei (AGN) is predominantly produced by star formation and that candidate dusty AGNs with a power-law emission in the mid-IR systematically occur in compact, dusty starbursts. After correcting for the effect of starbursts on IR8, we identify new candidates for extremely obscured AGNs.
Background. The Shingles Prevention Study (SPS) demonstrated zoster vaccine efficacy through 4 years postvaccination. A Short-Term Persistence Substudy (STPS) demonstrated persistence of vaccine ...efficacy for at least 5 years. A Long-Term Persistence Substudy (LTPS) was undertaken to further assess vaccine efficacy in SPS vaccine recipients followed for up to 11 years postvaccination. Study outcomes were assessed for the entire LTPS period and for each year from 7 to 11 years postvaccination. Methods. Surveillance, case determination, and follow-up were comparable to those in SPS and STPS. Because SPS placebo recipients were offered zoster vaccine before the LTPS began, there were no unvaccinated controls. Instead, SPS and STPS placebo results were used to model reference placebo groups. Results. The LTPS enrolled 6867 SPS vaccine recipients. Compared to SPS, estimated vaccine efficacy in LTPS decreased from 61.1% to 37.3% for the herpes zoster (HZ) burden of illness (BOI), from 66.5% to 35.4% for incidence of postherpetic neuralgia, and from 51.3% to 21.1% for incidence of HZ, and declined for all 3 outcome measures from 7 through 11 years postvaccination. Vaccine efficacy for the HZ BOI was significantly greater than zero through year 10 postvaccination, whereas vaccine efficacy for incidence of HZ was significantly greater than zero only through year 8. Conclusions. Estimates of vaccine efficacy decreased over time in the LTPS population compared with modeled control estimates. Statistically significant vaccine efficacy for HZ BOI persisted into year 10 postvaccination, whereas statistically significant vaccine efficacy for incidence of HZ persisted only through year 8.
The VIPERS Multi-Lambda Survey Moutard, T; Arnouts, S; Ilbert, O ...
Astronomy and astrophysics (Berlin),
6/2016, Letnik:
590
Journal Article
Recenzirano
Odprti dostop
We investigate the evolution of the galaxy stellar mass function and stellar mass density from redshift z= 0.2 to z= 1.5 of a K sub(s)< 22-selected sample with highly reliable photometric redshifts ...and over an unprecedentedly large area. Our study is based on near-infrared observations carried out with the WIRCam instrument at CFHT over the footprint of the VIPERS spectroscopic survey and benefits from the high-quality optical photometry from the CFHTLS and ultraviolet observations with the GALEX satellite. The accuracy of our photometric redshifts is sigma sub(Delta)z/ (1 + z)< 0.03 and 0.05 for the bright (i sub(AB)< 22.5) and faint (i sub(AB)> 22.5) samples, respectively. The galaxy stellar mass function is measured with ~760000 galaxies down to K sub(s)~ 22 and over an effective area of ~22.4 deg super(2), the latter of which drastically reduces the statistical uncertainties (i.e. Poissonian error and cosmic variance). We point out the importance of carefully controlling the photometric calibration, whose effect becomes quickly dominant when statistical uncertainties are reduced, which will be a major issue for future cosmological surveys with EUCLID or LSST, for instance. By exploring the rest-frame (NUV?r) vs. (r?K sub(s)) colour-colour diagram with which we separated star-forming and quiescent galaxies, (1) we find that the density of very massive log(M sub(?)/M sub(?)) > 11.5 galaxies is largely dominated by quiescent galaxies and increases by a factor 2 from z~ 1 to z~ 0.2, which allows for additional mass assembly through dry mergers. (2) We also confirm the scenario in which star formation activity is impeded above a stellar mass log(? super(*) sub(SF)/M sub(?)) = 10.64+ or -0.01. This value is found to be very stable at 0.2 <z< 1.5. (3) We discuss the existence of a main quenching channel that is followed by massive star-forming galaxies, and we finally (4) characterise another quenching mechanism that is required to explain the clear excess of low-mass quiescent galaxies that is observed at low redshift.
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