ABSTRACT
The physical properties of Epoch of Reionization (EoR) galaxies are still poorly constrained by observations. To better understand the ionizing properties of galaxies in the EoR, we ...investigate deep, rest-frame ultraviolet (UV) spectra of ≃500 star-forming galaxies at 3 ≤ z ≤ 5 selected from the public ESO-VANDELS spectroscopic survey. The absolute ionizing photon escape fraction ($f_{\rm esc}^{\rm abs}$, i.e. the ratio of leaking against produced ionizing photons) is derived by combining absorption line measurements with estimates of the UV attenuation. The ionizing production efficiency (ξion, i.e. the number of ionizing photons produced per non-ionizing UV luminosity) is calculated by fitting the far-UV (FUV) stellar continuum of the VANDELS galaxies. We find that the $f_{\rm esc}^{\rm abs}$ and ξion parameters increase towards low-mass, blue UV-continuum slopes and strong Ly α emitting galaxies, and both are slightly higher-than-average for the UV-faintest galaxies in the sample. Potential Lyman Continuum Emitters (LCEs, $f_{\rm esc}^{\rm abs} \ge 5{{\ \rm \, per\ cent}}$) and selected Lyman Alpha Emitters (LAEs, WLyα ≤ −20 Å) show systematically higher ξion (log ξion(Hz erg−1) ≈ 25.38, 25.41) than non-LCEs and non-LAEs (log ξion(Hz erg−1) ≈ 25.18, 25.14) at similar UV magnitudes. This indicates very young underlying stellar populations (≈10 Myr) at relatively low metallicities (≈0.2 Z⊙). The FUV non-ionizing spectra of potential LCEs is characterized by blue UV slopes (≤−2), enhanced Ly α emission (≤−25 Å), strong UV nebular lines (e.g. high ${\rm C\, \small {IV}}$1550/${\rm C\, \small {III}}$1908 ≥0.75 ratios), and weak absorption lines (≤1 Å). The latter suggests the existence of low gas-column-density channels in the interstellar medium, which enables the escape of ionizing photons. By comparing our VANDELS results against other surveys in the literature, our findings imply that the ionizing budget in the EoR was likely dominated by UV-faint, low-mass, and dustless galaxies.
ABSTRACT
We present the first X-ray observation at sub-arcsecond resolution of the high-redshift (z = 6.18) radio-loud quasar CFHQS J142952 + 544717 (J1429). The ∼100 net-count 0.3–7 keV spectrum ...obtained from ∼30 ks Chandra exposure is best fit by a single power-law model with a photon index Γ = 2.0 ± 0.2 and no indication of an intrinsic absorber, implying a 3.6–72 keV rest-frame luminosity $L_{\rm X}=(2.3^{+0.6}_{-0.5})\times 10^{46}$ erg s−1. We identify a second X-ray source at 30″ distance from J1429 position, with a soft (Γ ≃ 2.8) and absorbed (equivalent hydrogen column density NH < 13.4 × 1020 cm−2) spectrum, which likely contaminated J1429 spectra obtained in lower angular resolution observations. Based on the analysis of the Chandra image, the bulk of the X-ray luminosity is produced within the central ∼3 kpc region, either by the disc/corona system, or by a moderately aligned jet. In this context, we discuss the source properties in comparison with samples of low- and high-redshift quasars. We find indication of a possible excess of counts over the expectations for a point-like source in a 0.5″–1.5″ (∼3−8 kpc) annular region. The corresponding X-ray luminosity at J1429 redshift is 4 × 1045 erg s−1. If confirmed, this emission could be related to either a large-scale X-ray jet, or a separate X-ray source.
We study the variation of radon mass exhalation rate (
J
m
) and thoron surface exhalation rate (
J
s
) with soil’s porosity and moisture content using a scintillation based monitor-Smart RnDuo. ...Assessment were carried out in around 40 soil samples collected from four villages of East Khasi Hills district, Meghalaya, India. Results revealed that, both
J
m
and
J
s
shows no convincing trend of variation with porosity, while with respect to moisture content, a sporadic increase is observed in the values of
J
m
and
J
s
up to certain level, beyond which a decreasing trend is observed; accountable reasons are discussed in the manuscript.
Undoped and Nd (0.2, 0.6, 0.8, 1.0, 1.2 and 1.6 at%)-doped GdVO
4
single crystals have been grown by optical floating zone technique. XRD analysis reveals small lattice expansion especially along
c
...axis on Nd doping. It has been observed that the extra-ordinary refractive index (RI) of undoped GdVO
4
crystals is higher than the doped GdVO
4
single crystals up to 1.0 at% Nd doping, beyond which it surpasses the value of the undoped crystal. This is due to the competing effect of lattice elongation and decrease in electron density on Nd doping. The increase in RI with Nd doping is attributed to macroscopic polarization effects. Moreover, the extra-ordinary refractive index (
n
e
) only increases on increasing Nd concentration, whereas ordinary refractive index (
n
o
) remains unaffected within the measurement limits. The temperature-dependent RI measurements depicted a positive thermo-optic coefficient (TOC) for RI and birefringence, which is ~ 10
−5
/°C and is independent of doping concentration. TOC for
n
e
is higher than
n
o,
which has been explained on the basis of anisotropic thermal expansion. An important set of relations between TOC and wavelength (532–1551 nm) has been established which is useful for estimating TOC in the temperature range of 30–150 °C.
We present a novel method for identifying candidate high-redshift quasars (HzQs;
z
≳ 5.5) –which are unique probes of supermassive black hole growth in the early Universe– from large-area optical ...and infrared photometric surveys. Using Gaussian mixture models to construct likelihoods and incorporating informed priors based on population statistics, our method uses a Bayesian framework to assign posterior probabilities that differentiate between HzQs and contaminating sources. We additionally include deep radio data to obtain informed priors. Using existing HzQ data in the literature, we set a posterior threshold that accepts ∼90% of known HzQs while rejecting > 99% of contaminants such as dwarf stars or lower redshift galaxies. Running the probability selection on test samples of simulated HzQs and contaminants, we find that the efficacy of the probability method is higher than traditional colour cuts, decreasing the fraction of accepted contaminants by 86% while retaining a similar fraction of HzQs. As a test, we apply our method to the Pan-STARRS Data Release 1 (PS1) source catalogue within the HETDEX Spring field area on the sky, covering 400 sq. deg. and coinciding with deep radio data from the LOFAR Two-metre Sky Survey Data Release 1. From an initial sample of ∼5 × 10
5
sources in PS1, our selection shortlists 251 candidate HzQs, which are further reduced to 63 after visual inspection. Shallow spectroscopic follow-up of 13 high-probability HzQs resulted in the confirmation of a previously undiscovered quasar at
z
= 5.66 with photometric colours
i
−
z
= 1.4, lying outside the typically probed regions when selecting HzQs based on colours. This discovery demonstrates the efficacy of our probabilistic HzQ selection method in selecting more complete HzQ samples, which holds promise when employed on large existing and upcoming photometric data sets.
ABSTRACT
We present Very Large Telescope/Spectrograph for INtegral Field Observations in the Near Infrared (VLT/SINFONI) observations of 35 quasars at 2.1 < z < 3.2, the majority of which were ...selected from the Clusters Around Radio-Loud AGN (CARLA) survey. CARLA quasars have large C iv-based black hole masses (MBH > 109 M⊙) and powerful radio emission ($P_{500\, \rm MHz}$ > 27.5 W Hz−1). We estimate H α-based MBH, finding a scatter of 0.35 dex compared to C iv. We evaluate several recipes for correcting C iv-based masses, which reduce the scatter to 0.24 dex. The radio power of the radio-loud quasars is at most weakly correlated with the interconnected quantities H αwidth, L5100, and MBH, suggesting that it is governed by different physical processes. However, we do find a strong inverse correlation between C iv blueshift and radio power linked to higher Eddington ratios and L5100. Under standard assumptions, the black hole (BH) growth time is longer than the cosmic age for many CARLA quasars, suggesting that they must have experienced more efficient growth in the past. If these BHs were growing from seeds since the epoch of reionization, it is possible that they grew at the Eddington limit like the quasars at z ∼ 6–7, and then continued to grow at the reduced rates observed until z ∼ 2–3. Finally, we study the relation between MBH and environment, finding a weak positive correlation between MBH and galaxydensity measured by CARLA.
Blunt traumatic vertebral injury (TVAI) is frequently associated with head and neck injury and is being detected with increasing frequency due to improved imaging of the trauma patient. In a few ...cases, it can lead to potentially fatal posterior circulation ischaemia There is debate in the literature regarding whether TVAI should be actively screened for and, if so, how. Management of TVAI may be conservative, medical (antiplatelet agents or anticoagulation), endovascular or open surgery. We review the literature concerning the mechanisms and presentation of TVAI following blunt injury and the current screening recommendations. Management strategies proposed are based on the radiological grade and clinical severity of TVAI, where high-grade symptomatic injuries and high-grade injuries in patients where anticoagulation is contraindicated are treated endovascularly and asymptomatic or low-grade injuries are managed with anticoagulation where it is not contraindicated. Follow-up is via CT angiography to assess for resolution of the injury.
•Cr co-doped Nd:GdVO4 crystal is grown for the first time by OFZ technique.•Absorption at ~1100 nm for 1.0 at% Cr doping decreases on increase in O2 in growth ambience.•But for higher conc. (1.2 & ...1.5 at%) absorption increases on increase in O2 in ambience.•The trend of emission intensity at 1064 nm is in agreement with absorption data for all conc.•Along with Cr content the conc. of O2 in the growth ambience is also an important consideration for desired saturable absorption.
Single crystals of Cr co-doped Nd (0.5 at%):GdVO4 with varied Cr concentrations of 1.0, 1.2 and 1.5 at% were grown in ambience having 10%, 20% and 25% oxygen by optical floating zone technique for the first time to the best of our knowledge. Lattice parameters were found to be unchanged with Cr doping concentration. The etch pit dislocation density was in the range of 103–104/cm2. The observed fringes of nearly uniform thickness and spacing in birefringence interferometry indicate the optical uniformity of the crystal across the cross-section. Further, the effect of the doping concentration and the growth atmosphere on the optical absorption, particularly for the 2A1→2B2 transition (at ~1100 nm) due to Cr5+ ion, was investigated using polarized lights (i.e., E ǁ 001 or π-polarized) and E ⊥ 001 or σ-polarized) and found to be polarization sensitive. The transition peak of Cr at 1100 nm are allowed only for π- polarization of light whereas the transitions at 650 nm are allowed only for σ- polarization of light. The absorption of Cr5+ ion increases at 1100 nm with the increase of oxygen ambience for the Cr concentration 1.2 and 1.5 at% and for the crystals with Cr concentrations of 1.0 at%, a reverse effect in the absorption of Cr5+ ion was observed. The broad absorption transition at ~1100 nm is important as it results in saturable absorption that is used for self-Q-switching application. In accordance with the absorption data the photo luminescence intensity increases for 1.0 at% Cr doping and decreases for the 1.2 and 1.5 at% Cr doping with the increase of oxygen percentage in the growth ambience respectively. The observation has important technical implication in context to saturable absorption application. It suggests that to attain the desired level of saturable absorption, the growth ambience and the concentration of Cr should be chosen in line with the result presented here.
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•Novel silicone core SiH and Si-oxirane terminal dendrimers was synthesized.•Hyrosilation reaction of SiH functional dendrimers was carried out using Speier’s catalyst.•Thermal ...properties of hardener (TETA) cured silicone oxirane dendrimers were studied.•Effect of change in thermal behavior of commercial resin on addition of the silicone oxirane dendrimers was studied.
A series of silicone core dendrimers bearing SiH terminal group was synthesized by the reaction of tetraethoxysilane and diorganochlorosilane in high yields, which on reacting with allylglycidylether in presence of Speier’s catalyst yielded oxirane terminated dendrimers. These dendrimers were characterized using physico-chemical techniques viz; elemental analysis, Fourier transforms infrared spectroscopy (FT-IR) and proton nuclear magnetic resonance spectroscopy (1H NMR spectroscopy). Molecular weight was determined by vapour pressure osmometry (VPO). The rheological studies were performed to study the curing behavior of oxirane dendrimer with triethylenetetraamine. Thermal properties of cured dendrimers were evaluated using thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC). Change in thermal properties of epoxy resin (LY556) on addition of dendrimers was also studied by TGA and DSC.
Condensation of 9-chloro-2,4-(un)substituted acridines (1a-c) with various amines (2a-e) and 9-isothiocyanato-2,4-(un)substituted acridines (4a,b) with different amines (2a,b,d,e) gave condensed ...products 3a-o and 5a-g respectively. Compounds 3a-o and 5a-g were screened for anti-inflammatory activity at a dose of 50mg/kg p.o. Compound 3e exhibited 41.17% anti-inflammatory activity which is better than most commonly used standard drug ibuprofen which showed 39% anti-inflammatory (at 50mg/kg p.o.) activity. Anticancer activity evaluation of compounds 3a-o and 5a-g was carried out against a small panel of human cancer cell lines and compounds 3g, 3m and 5g exhibited good anticancer activity against breast (MCF-7), liver (HEP-2), colon (COLO-205, 502713, HCT-15), lung (A-549) and neuroblastoma (IMR-32) cancer cell lines at a concentration of 1 x 10(-5)M.
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