Prospects for detecting the 21cm forest from the diffuse intergalactic medium with LOFAR

We discuss the feasibility of the detection of the 21cm forest in the diffuse IGM with the radio telescope LOFAR. The optical depth to the 21cm line has been derived using simulations of reionization which include detailed radiative transfer of ionizing photons. We find that the spectra from reionization models with similar total comoving hydrogen ionizing emissivity but different frequency distribution look remarkably similar. Thus, unless the reionization histories are very different from each other (e.g. a predominance of UV vs. x-ray heating) we do not expect to distinguish them by means of observations of the 21cm forest. Because the presence of a strong x-ray background would make the detection of 21cm line absorption impossible, the lack of absorption could be used as a probe of the presence/intensity of the x-ray background and the thermal history of the universe. Along a random line of sight LOFAR could detect a global suppression of the spectrum from z>12, when the IGM is still mostly neutral and cold, in contrast with the more well-defined, albeit broad, absorption features visible at lower redshift. Sharp, strong absorption features associated with rare, high density pockets of gas could be detected also at z~7 along preferential lines of sight.Comment: 12 pages, 13 figures. MNRAS, in pres

Analisis produktivitas dan kinerja lingkungan dengan menggunakan konsep green productivity (study kasus PT.ABC)

PT. ABC is a private company engaged in the provision of clean water services under the auspices of PT. Kaltim Prima Coal). Constraint occurs is in the process of drinking water treatment and wastewater sludge yield potential as a source of environmental pollution. Other problems also exist in the high BOD and Cod content of wastewater after measurement. As for the number of connections installed for corporate customers, there are only 2,895 connections, while from the data of PTABC, the company's connection target is 12,589, so from the total target of PT. ABC has only been able to obtain a connection of 23% of the target to be achieved. a need to increase water production by PT. ABC in order to increase the quantity of clean water production for all consumers. The concept of green productivity (GP) can be used in the search for solutions to increase productivity and protect the environment. The study begins by identifying the root cause of a lot of liquid waste and a low amount of water production, setting objectives and targets, choosing the resources and information available to arrange alternative green productivity. There are two alternatives, the selected alternative in this study are alternative 2 merge maximizing the raw water intake, repair Well Bore Tj.Bara , and the use of wastewater that is the use of waste as material raw returned by first applying multilevel aeration technology to reduce levels of COD and BOD5 in wastewater. based on the use of the cost benefit anlysis method the company's productivity and EPI increases if implementing this alternative will increase 40% from the initial production of 114% to 154%. And the initial EPI index total value of -20.8 increased to 18.8 so it rose 39.6 which indicates an increase in productivity and environmental performanc

Constraining the epoch of reionization with the variance statistic: simulations of the LOFAR case

Several experiments are underway to detect the cosmic redshifted 21-cm signal from neutral hydrogen from the Epoch of Reionization (EoR). Due to their very low signal-to-noise ratio, these observations aim for a statistical detection of the signal by measuring its power spectrum. We investigate the extraction of the variance of the signal as a first step towards detecting and constraining the global history of the EoR. Signal variance is the integral of the signal's power spectrum, and it is expected to be measured with a high significance. We demonstrate this through results from a simulation and parameter estimation pipeline developed for the Low Frequency Array (LOFAR)-EoR experiment. We show that LOFAR should be able to detect the EoR in 600 hours of integration using the variance statistic. Additionally, the redshift ($z_r$) and duration ($\Delta z$) of reionization can be constrained assuming a parametrization. We use an EoR simulation of $z_r = 7.68$ and $\Delta z = 0.43$ to test the pipeline. We are able to detect the simulated signal with a significance of 4 standard deviations and extract the EoR parameters as $z_r = 7.72^{+0.37}_{-0.18}$ and $\Delta z = 0.53^{+0.12}_{-0.23}$ in 600 hours, assuming that systematic errors can be adequately controlled. We further show that the significance of detection and constraints on EoR parameters can be improved by measuring the cross-variance of the signal by cross-correlating consecutive redshift bins.Comment: 13 pages, 14 figures, Accepted for publication in MNRA

LOFAR insights into the epoch of reionization from the cross-power spectrum of 21 cm emission and galaxies

<p>Using a combination of N-body simulations, semi-analytic models and radiative transfer calculations, we have estimated the theoretical cross-power spectrum between galaxies and the 21 cm emission from neutral hydrogen during the epoch of reionization. In accordance with previous studies, we find that the 21 cm emission is initially correlated with haloes on large scales (greater than or similar to 30 Mpc), anticorrelated on intermediate (similar to 5 Mpc) and uncorrelated on small (less than or similar to 3 Mpc) scales. This picture quickly changes as reionization proceeds and the two fields become anticorrelated on large scales. The normalization of the cross-power spectrum can be used to set constraints on the average neutral fraction in the intergalactic medium and its shape can be a powerful tool to study the topology of reionization. When we apply a drop-out technique to select galaxies and add to the 21 cm signal the noise expected from the LOw Frequency ARray (LOFAR) telescope, we find that while the normalization of the cross-power spectrum remains a useful tool for probing reionization, its shape becomes too noisy to be informative. On the other hand, for an Ly alpha Emitter (LAE) survey both the normalization and the shape of the cross-power spectrum are suitable probes of reionization. A closer look at a specific planned LAE observing program using Subaru Hyper-Suprime Cam reveals concerns about the strength of the 21 cm signal at the planned redshifts. If the ionized fraction at z similar to 7 is lower than the one estimated here, then using the cross-power spectrum may be a useful exercise given that at higher redshifts and neutral fractions it is able to distinguish between two toy models with different topologies.</p>

Imaging neutral hydrogen on large-scales during the Epoch of Reionization with LOFAR

The first generation of redshifted 21 cm detection experiments, carried out with arrays like LOFAR, MWA and GMRT, will have a very low signal-to-noise ratio per resolution element (\sim 0.2). In addition, whereas the variance of the cosmological signal decreases on scales larger than the typical size of ionization bubbles, the variance of the formidable galactic foregrounds increases, making it hard to disentangle the two on such large scales. The poor sensitivity on small scales on the one hand, and the foregrounds effect on large scales on the other hand, make direct imaging of the Epoch of Reionization of the Universe very difficult, and detection of the signal therefore is expected to be statistical.Despite these hurdles, in this paper we argue that for many reionization scenarios low resolution images could be obtained from the expected data. This is because at the later stages of the process one still finds very large pockets of neutral regions in the IGM, reflecting the clustering of the large-scale structure, which stays strong up to scales of \sim 120 comoving Mpc/h (\sim 1 degree). The coherence of the emission on those scales allows us to reach sufficient S/N (\sim 3) so as to obtain reionization 21 cm images. Such images will be extremely valuable for answering many cosmological questions but above all they will be a very powerful tool to test our control of the systematics in the data. The existence of this typical scale (\sim 120 comoving Mpc/h) also argues for designing future EoR experiments, e.g., with SKA, with a field of view of at least 4 degree.Comment: Replaced with final version (minor changes), 9 figures, 11 pages, accepted for publication in MNRA

Influence of Aerobic and Nitrogen Flush Packaging Methods and Frozen Storage on Quality Characteristics of Prune Puree Incorporated Ready-to-Eat Mutton Kheema

The present investigation was carried out to evaluate the influence of aerobic packaging and nitrogen flush packaging methods on quality characteristics (physico-chemical, microbial and sensory quality) of 15 % prune puree extended mutton kheema at 0, 30, 60 and 90 days of frozen storage (-18 ±1 °C). The results revealed that there was a significant (P<0.05) decrease in pH, thiobarbituric acid reactive substance (TBARS) values, tyrosine value and per cent free fatty acid (FFA) values with incorporation of prune puree. Furthermore, there was a significant (P<0.05) increase in the pH, TBARS values, tyrosine and FFA content as the storage progressed from 0-90 days in during frozen storage. Irrespective of storage days and treatments, nitrogen flush packaged mutton kheema recorded significantly (P<0.05) lower pH, TBARS, Tyrosine value and FFA content compared to aerobic packaging method. Prune puree added mutton kheema recorded significantly (P<0.05) lower standard plate counts (SPC) and yeast and mould counts, and these counts are increased as the storage progressed from 0 to 90 days during frozen temperature. Nitrogen flush packaging of mutton kheema also helped in limiting the microbial growth during entire period of storage. Organoleptic evaluation scores of all the products were rated as excellent to very good, except for the appearance, which was rated as good. However, the scores decreased significantly with increase in storage time during frozen temperature. Based on the results, it is concluded that prune puree could be beneficially incorporated at levels of 15 % improving the physico-chemical, microbial quality with more health benefits. Nitrogen flush pouches for packaging mutton kheema help in preserving the sensory scores of fresh product during frozen storage

Probing reionization with LOFAR (Low Frequency Array) using 21-cm redshift space distortions

One of the most promising ways to study the epoch of reionization (EoR) is through radio observations of the redshifted 21-cm line emission from neutral hydrogen. These observations are complicated by the fact that the mapping of redshifts to line-of-sight positions is distorted by the peculiar velocities of the gas. Such distortions can be a source of error if they are not properly understood, but they also encode information about cosmology and astrophysics. We study the effects of redshift space distortions on the power spectrum of 21-cm radiation from the EoR using large-scale N-body and radiative transfer simulations. We quantify the anisotropy introduced in the 21-cm power spectrum by redshift space distortions and show how it evolves as reionization progresses and how it relates to the underlying physics. We go on to study the effects of redshift space distortions on LOFAR observations, taking instrument noise and foreground subtraction into account.We find that LOFAR should be able to directly observe the power spectrum anisotropy due to redshift space distortions at spatial scales around k ∼ 0.1Mpc−1 after 1000 h of integration time. At larger scales, sample errors become a limiting factor, while at smaller scales detector noise and foregrounds make the extraction of the signal problematic. Finally, we show how the astrophysical information contained in the evolution of the anisotropy of the 21-cm power spectrum can be extracted from LOFAR observations, and how it can be used to distinguish between different reionization scenarios.Web of Scienc

The LOFAR radio environment

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