ALBERT

Description: Emergence of drug resistance during visceral leishmaniasis (VL) is a major obstacle imposed during successful therapy. An effective vaccine strategy against this disease is therefore necessary. Our present study exploited the SLA (soluble leishmanial antigen) and PGN (peptidoglycan) stimulated bone marrow-derived dendritic cells (DCs) as a suitable vaccine candidate during experimental VL. SLA-PGN-stimulated DCs showed a significant decrease in hepatic and splenic parasite burden, which were associated with increased production of nitric oxide and pro-inflammatory cytokines such as IL-12, IFN- and IL-17. Elevated level of IL-17 was accompanied with the generation of more Th17 cells. Further studies on DC provided the evidence that these SLA-PGN-stimulated DCs played an important role in providing necessary cytokines such as IL-6, IL-23 and TGF-β for the generation of Th17 cells. Interestingly, inhibition of protein kinase C-β (PKCβ) in DCs led to decreased production of Th17 polarizing cytokines, causing reduction of the Th17 population size. Altogether, our finding highlighted the important role of DC-based PKCβ in regulation of the function and generation of Th17 cells.

Description: The non-Gaussian nature of the epoch of reionization (EoR) 21-cm signal has a significant impact on the error variance of its power spectrum P ( k ). We have used a large ensemble of seminumerical simulations and an analytical model to estimate the effect of this non-Gaussianity on the entire error-covariance matrix $\bf{C}$ ij . Our analytical model shows that $\bf{C}$ ij has contributions from two sources. One is the usual variance for a Gaussian random field which scales inversely of the number of modes that goes into the estimation of P ( k ). The other is the trispectrum of the signal. Using the simulated 21-cm Signal Ensemble, an ensemble of the Randomized Signal and Ensembles of Gaussian Random Ensembles we have quantified the effect of the trispectrum on the error variance $\bf{C}$ ii . We find that its relative contribution is comparable to or larger than that of the Gaussian term for the k range 0.3 ≤ k ≤ 1.0 Mpc –1 , and can be even ~200 times larger at k ~ 5 Mpc –1 . We also establish that the off-diagonal terms of $\bf{C}$ ij have statistically significant non-zero values which arise purely from the trispectrum. This further signifies that the error in different k modes are not independent. We find a strong correlation between the errors at large k values (≥0.5 Mpc –1 ), and a weak correlation between the smallest and largest k values. There is also a small anticorrelation between the errors in the smallest and intermediate k values. These results are relevant for the k range that will be probed by the current and upcoming EoR 21-cm experiments.

Description: We study the cross-correlation of distribution of galaxies, the Sunyaev-Zel'dovich (SZ) and X-ray power spectra of galaxies from current and upcoming surveys and show these to be excellent probes of the nature, i.e. extent, evolution and energetics, of the circumgalactic medium (CGM). The SZ-galaxy cross-power spectrum, especially at large multipoles, depends on the steepness of the pressure profile of the CGM. This property of the SZ signal can, thus, be used to constrain the pressure profile of the CGM. The X-ray cross-power spectrum also has a similar shape. However, it is much more sensitive to the underlying density profile. We forecast the detectability of the cross-correlated galaxy distribution, SZ and X-ray signals by combining South Pole Telescope-Dark Energy Survey (SPT-DES) and eROSITA-DES/eROSITA-LSST (extended ROentgen Survey with an Imaging Telescope Array-Large Synoptic Survey Telescope) surveys, respectively. We find that, for the SPT-DES survey, the signal-to-noise ratio peaks at high mass and redshift with signal-to-noise ratio ~9 around M h ~ 10 13 h –1 M and z ~ 1.5–2 for flat density and temperature profiles. The signal-to-noise ratio peaks at ~6(12) for the eROSITA-DES (eROSITA-LSST) surveys. We also perform a Fisher matrix analysis to find the constraint on the gas fraction in the CGM in the presence or absence of an unknown redshift evolution of the gas fraction. Finally, we demonstrate that the cross-correlated SZ-galaxy and X-ray-galaxy power spectrum can be used as powerful probes of the CGM energetics and potentially discriminate between different feedback models recently proposed in the literature; for example, one can distinguish a ‘no active galactic nuclei feedback’ scenario from a CGM energized by ‘fixed-velocity hot winds’ at greater than 3.

Description: The observed 21 cm signal from the epoch of reionization will be distorted along the line of sight by the peculiar velocities of matter particles. These redshift-space distortions will affect the contrast in the signal and will also make it anisotropic. This anisotropy contains information about the cross-correlation between the matter density field and the neutral hydrogen field, and could thus potentially be used to extract information about the sources of reionization. In this paper, we study a collection of simulated reionization scenarios assuming different models for the sources of reionization. We show that the 21 cm anisotropy is best measured by the quadrupole moment of the power spectrum. We find that, unless the properties of the reionization sources are extreme in some way, the quadrupole moment evolves very predictably as a function of global neutral fraction. This predictability implies that redshift-space distortions are not a very sensitive tool for distinguishing between reionization sources. However, the quadrupole moment can be used as a model-independent probe for constraining the reionization history. We show that such measurements can be done to some extent by first-generation instruments such as LOFAR, while the SKA should be able to measure the reionization history using the quadrupole moment of the power spectrum to great accuracy.

Description: A proposed method for dealing with foreground emission in upcoming 21-cm observations from the epoch of reionization is to limit observations to an uncontaminated window in Fourier space. Foreground emission can be avoided in this way, since it is limited to a wedge-shaped region in k || , k space. However, the power spectrum is anisotropic owing to redshift-space distortions from peculiar velocities. Consequently, the 21-cm power spectrum measured in the foreground avoidance window – which samples only a limited range of angles close to the line-of-sight direction – differs from the full redshift-space spherically averaged power spectrum which requires an average over all angles. In this paper, we calculate the magnitude of this ‘wedge bias’ for the first time. We find that the bias amplifies the difference between the real-space and redshift-space power spectra. The bias is strongest at high redshifts, where measurements using foreground avoidance will overestimate the redshift-space power spectrum by around 100 per cent, possibly obscuring the distinctive rise and fall signature that is anticipated for the spherically averaged 21-cm power spectrum. In the later stages of reionization, the bias becomes negative, and smaller in magnitude (20 per cent).

Description: Measurements of the H i 21-cm power spectra from the reionization epoch will be influenced by the evolution of the signal along the line-of-sight direction of any observed volume. We use numerical as well as seminumerical simulations of reionization in a cubic volume of 607 Mpc across to study this so-called light-cone effect on the H i 21-cm power spectrum. We find that the light-cone effect has the largest impact at two different stages of reionization: one when reionization is ~20 per cent and other when it is ~80 per cent completed. We find a factor of ~4 amplification of the power spectrum at the largest scale available in our simulations. We do not find any significant anisotropy in the 21-cm power spectrum due to the light-cone effect. We argue that for the power spectrum to become anisotropic, the light-cone effect would have to make the ionized bubbles significantly elongated or compressed along the line of sight, which would require extreme reionization scenarios. We also calculate the two-point correlation functions parallel and perpendicular to the line of sight and find them to differ. Finally, we calculate an optimum frequency bandwidth below which the light-cone effect can be neglected when extracting power spectra from observations. We find that if one is willing to accept a 10 per cent error due to the light-cone effect, the optimum frequency bandwidth for k = 0.056 Mpc –1 is ~7.5 MHz. For k = 0.15 and 0.41 Mpc –1 , the optimum bandwidth is ~11 and ~16 MHz, respectively.

Description: We present a detailed comparison of three different simulations of the epoch of reionization (EoR). The radiative transfer simulation ( c 2 -ray ) among them is our benchmark. Radiative transfer codes can produce realistic results, but are computationally expensive. We compare it with two seminumerical techniques: one using the same haloes as c 2 -ray as its sources (Sem-Num), and one using a conditional Press–Schechter scheme (CPS+GS). These are vastly more computationally efficient than c 2 -ray , but use more simplistic physical assumptions. We evaluate these simulations in terms of their ability to reproduce the history and morphology of reionization. We find that both Sem-Num and CPS+GS can produce an ionization history and morphology that is very close to c 2 -ray , with Sem-Num performing slightly better compared to CPS+GS. We also study different redshift-space observables of the 21-cm signal from EoR: the variance, power spectrum and its various angular multipole moments. We find that both seminumerical models perform reasonably well in predicting these observables at length scales relevant for present and future experiments. However, Sem-Num performs slightly better than CPS+GS in producing the reionization history, which is necessary for interpreting the future observations. The CPS+GS scheme, however, has the advantage that it is not restricted by the mass resolution of the dark matter density field.

Description: We have used seminumerical simulations of reionization to study the behaviour of the power spectrum of the epoch of reionization 21-cm signal in redshift space. We have considered two models of reionization, one which has homogeneous recombination (HR) and the other incorporating inhomogeneous recombination (IR). We have estimated the observable quantities – quadrupole and monopole moments of H  i power spectrum at redshift space from our simulated data. We find that the magnitude and nature of the ratio between the quadrupole and monopole moments of the power spectrum ( $P^{\rm s}_2 /P^{\rm s}_0$ ) can be a possible probe for the epoch of reionization. We observe that this ratio becomes negative at large scales for $\bar{x}_{{\rm H\,{\scriptscriptstyle {I}}}}\le 0.7$ irrespective of the reionization model, which is a direct signature of an inside-out reionization at large scales. It is possible to qualitatively interpret the results of the simulations in terms of the fluctuations in the matter distribution and the fluctuations in the neutral fraction which have power spectra and cross-correlation P ( k ), P xx ( k ) and P x ( k ), respectively. We find that at large scales the fluctuations in matter density and neutral fraction are exactly anticorrelated through all stages of reionization. This provides a simple picture where we are able to qualitatively interpret the behaviour of the redshift-space power spectra at large scales with varying $\bar{x}_{{\rm H\,{\scriptscriptstyle {I}}}}$ entirely in terms of a just two quantities, namely $\bar{x}_{{\rm H\,{\scriptscriptstyle {I}}}}$ and the ratio P xx / P . The nature of P x becomes different for HR and IR scenarios at intermediate and small scales. We further find that it is possible to distinguish between an inside-out and an outside-in reionization scenario from the nature of the ratio $P^{\rm s}_2 /P^{\rm s}_0$ at intermediate length scales.

Description: The epoch of reionization (EoR) 21-cm signal is expected to become highly non-Gaussian as reionization progresses. This severely affects the error-covariance of the EoR 21-cm power spectrum that is important for predicting the prospects of a detection with ongoing and future experiments. Most earlier works have assumed that the EoR 21-cm signal is a Gaussian random field where (1) the error-variance depends only on the power spectrum and the number of Fourier modes in the particular k bin, and (2) the errors in the different k bins are uncorrelated. Here, we use an ensemble of simulated 21-cm maps to analyse the error-covariance at various stages of reionization. We find that even at the very early stages of reionization ( $\bar{x}_{\rm H\,{\small \small {I}}}\sim 0.9$ ), the error-variance significantly exceeds the Gaussian predictions at small length-scales ( k 〉 0.5 Mpc –1 ) while they are consistent at larger scales. The errors in most k bins (both large and small scales) are however found to be correlated. Considering the later stages ( $\bar{x}_{\rm H\,{\small \small {I}}}=0.15$ ), the error-variance shows an excess in all k bins within k ≥ 0.1 Mpc –1 , and it is around 200 times larger than the Gaussian prediction at k ~ 1 Mpc –1 . The errors in the different k bins are all also highly correlated, barring the two smallest k bins that are anti-correlated with the other bins. Our results imply that the predictions for different 21-cm experiments based on the Gaussian assumption underestimate the errors, and it is necessary to incorporate the non-Gaussianity for more realistic predictions.

Description: Non-gravitational feedback affects the nature of the intracluster medium (ICM). X-ray cooling of the ICM and in situ energy feedback from active galactic nuclei (AGNs) and supernovae as well as pre-heating of the gas at epochs preceding the formation of clusters are proposed mechanisms for such feedback. While cooling and AGN feedbacks are dominant in cluster cores, the signatures of a pre-heated ICM are expected to be present even at large radii. To estimate the degree of pre-heating, with minimum confusion from AGN feedback/cooling, we study the excess entropy and non-gravitational energy profiles up to r 200 for a sample of 17 galaxy clusters using joint data sets of Planck Sunyaev–Zel'dovich pressure and ROSAT /Position Sensitive Proportional Counter gas density profiles. The canonical value of pre-heating entropy floor of 300 keV cm 2 , needed in order to match cluster scalings, is ruled out at 3. We also show that the feedback energy of 1 keV particle –1 is ruled out at 5.2 beyond r 500 . Our analysis takes both non-thermal pressure and clumping into account which can be important in outer regions. Our results based on the direct probe of the ICM in the outermost regions do not support any significant pre-heating.