Constraining the clustering and 21-cm signature of radio galaxies at cosmic dawn

The efficiency of radio emission is an important unknown parameter of early galaxies at cosmic dawn, as models with high efficiency have been shown to modify the cosmological 21-cm signal substantially, deepening the absorption trough and boosting the 21-cm power spectrum. Such models have been previously directly constrained by the overall extragalactic radio background as observed by ARCADE-2 and LWA-1. In this work, we constrain the clustering of high redshift radio sources by utilizing the observed upper limits on arcminute-scale anisotropy from the VLA at 4.9~GHz and ATCA at 8.7~GHz. Using a semi-numerical simulation of a plausible astrophysical model for illustration, we show that the clustering constraints on the radio efficiency are much stronger than those from the overall background intensity, by a factor that varies from 12 at redshift 7 to 30 at redshift 22. As a result, the predicted maximum depth of the global 21-cm signal is lowered by a factor of 5 (to 1700~mK), and the maximum 21-cm power spectrum peak at cosmic dawn is lowered by a factor of 24 (to $2\times 10^5$~mK$^2$). We conclude that the observed clustering is the strongest current direct constraint on such models, but strong early radio emission from galaxies remains viable for producing a strongly enhanced 21-cm signal from cosmic dawn.Comment: 8 pages, 3 figure

HERA Phase I Limits on the Cosmic 21 cm Signal: Constraints on Astrophysics and Cosmology during the Epoch of Reionization

Recently, the Hydrogen Epoch of Reionization Array (HERA) has produced the experiment's first upper limits on the power spectrum of 21 cm fluctuations at z ~ 8 and 10. Here, we use several independent theoretical models to infer constraints on the intergalactic medium (IGM) and galaxies during the epoch of reionization from these limits. We find that the IGM must have been heated above the adiabatic-cooling threshold by z ~ 8, independent of uncertainties about IGM ionization and the radio background. Combining HERA limits with complementary observations constrains the spin temperature of the z ~ 8 neutral IGM to 27 K $\langle {\overline{T}}_{S}\rangle$ 630 K (2.3 K $\langle {\overline{T}}_{S}\rangle$ 640 K) at 68% (95%) confidence. They therefore also place a lower bound on X-ray heating, a previously unconstrained aspects of early galaxies. For example, if the cosmic microwave background dominates the z ~ 8 radio background, the new HERA limits imply that the first galaxies produced X-rays more efficiently than local ones. The z ~ 10 limits require even earlier heating if dark-matter interactions cool the hydrogen gas. If an extra radio background is produced by galaxies, we rule out (at 95% confidence) the combination of high radio and low X-ray luminosities of L r,ν /SFR > 4 × 1024 W Hz-1 ${M}_{\odot }^{-1}$ yr and L X /SFR 39 erg s-1 ${M}_{\odot }^{-1}$ yr. The new HERA upper limits neither support nor disfavor a cosmological interpretation of the recent Experiment to Detect the Global EOR Signature (EDGES) measurement. The framework described here provides a foundation for the interpretation of future HERA results

Constraining the Clustering and 21 cm Signature of Radio Galaxies at Cosmic Dawn

Abstract The efficiency of radio emission is an important unknown parameter of early galaxies at cosmic dawn, as models with high efficiency have been shown to modify the cosmological 21 cm signal substantially, deepening the absorption trough and boosting the 21 cm power spectrum. Such models have been previously directly constrained by the overall extragalactic radio background, as observed by Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission 2 and Long Wavelength Array. In this work, we constrain the clustering of high-redshift radio sources by utilizing the observed upper limits on arcminute-scale anisotropy from the Very Large Array at 4.9 GHz and Australia Telescope Compact Array at 8.7 GHz. Using a seminumerical simulation of a plausible astrophysical model for illustration, we show that the clustering constraints on the radio efficiency are much stronger than those from the overall background intensity by a factor that varies between 18 and 55 in the redshift range of 7–22. As a result, the predicted maximum depth of the global 21 cm signal is lowered by a factor of 6 (to 1400 mK), and the maximum 21 cm power spectrum peak at cosmic dawn is lowered by a factor of 45 (to 1.3 × 105 mK2). We conclude that the observed clustering is the strongest current direct constraint on such models, but strong early radio emission from galaxies remains viable for producing a strongly enhanced 21 cm signal from cosmic dawn.</jats:p

Influence of spin-state transition on structural and other physical properties in Ba0.5Sr0.5Co0.8Fe0.2O3-delta ceramic

We explore, in detail, the remarkable influence of spin-state transition - low (S = 1/2) to high spin (S = 5/2) - on crystallographic, thermal, electrical, and mechanical properties in Ba0.5Sr0.5Co0.8Fe0.2O3-delta ceramic. The low to high spin transition takes place at T* similar to 600 K with a rather broad transition zone of nearly 200 K. We find that the electrical resistivity, mechanical stiffness and toughness, thermal expansion coefficient, and the crystallographic structure exhibit clear anomalous features around T*. The transition, however, appears to be isostructural Pm (3) over barm -> Pm (3) over barm (cubic -> cubic). Significant influence of spin-state transition on a variety of properties could have serious implications for several applications ranging from magnetic sensors to electrocatalysts to ion separation membranes

Dietary supplementation of Neem (Azadirachta indica) leaf extracts improved growth performance and reduced production cost in broilers

Background and Aim: Global trend to remove the antibiotic growth promoter (AGP) from animals contributes to the exploration of successful measures to sustain production and reduces the intestinal diseases in the post-AGP era. Plant extracts, therefore, have been used to improve performance and intestinal health. Here, we conducted a study to evaluate the effects of neem (Azadirachta indica) leaf extracts (NLE) as alternatives to AGPs in broiler chickens. Materials and Methods: Sixty day-old broiler chicks were assigned to 12-floor pens, each stocked with five birds and divided into three treatment groups of four pens per treatment. The groups were: Negative control, basal diet without additives; positive control, basal diet with antibiotics and vitamins; and NLE treated group, basal diet supplemented with 0.1% aqua extract of neem leaves. Results: Overall feed intake was significantly (p≤0.05) highest in the positive control. Higher body weight, higher dressing percentage, and lower feed conversion ratio were observed in birds treated with NLE compared to the negative control group (p≤0.05) but not the positive control group (p>0.05). There was no significant variation in hematology between different groups. Furthermore, the economic evaluation indicated that the NLE treatment was found cheaper than control and antibiotic treatment in cost-benefit analysis. Conclusion: We suggest NLE might be a cheaper alternative to antibiotics in broiler production as indicated by improved body weight and feed efficiency