Photo-z performance for precision cosmology

Current and future weak-lensing surveys will rely on photometrically estimated redshifts of very large numbers of galaxies. In this paper, we address several different aspects of the demanding photo-z performance that will be required for future experiments, such as the proposed ESA Euclid mission. It is first shown that the proposed all-sky near-infrared photometry from Euclid, in combination with anticipated ground-based photometry (e.g. PanStarrs-2 or DES) should yield the required precision in individual photo-z of σz(z) ≤ 0.05(1 +z) at IAB≤ 24.5. Simple a priori rejection schemes based on the photometry alone can be tuned to recognize objects with wildly discrepant photo-z and to reduce the outlier fraction to ≤0.25 per cent with only modest loss of otherwise usable objects. Turning to the more challenging problem of determining the mean redshift 〈z〉 of a set of galaxies to a precision of |Δ〈z〉| ≤ 0.002(1 +z) we argue that, for many different reasons, this may be best accomplished by relying on the photo-z themselves rather than on the direct measurement of 〈z〉 from spectroscopic redshifts of a representative subset of the galaxies, as has usually been envisaged. We present in Appendix A an analysis of the substantial difficulties in the latter approach that arise from the presence of large-scale structure in spectroscopic survey fields. A simple adaptive scheme based on the statistical properties of the photo-z likelihood functions is shown to meet this stringent systematic requirement, although further tests on real data will be required to verify this. We also examine the effect of an imprecise correction for Galactic extinction on the photo-z and the precision with which the Galactic extinction can be determined from the photometric data itself, for galaxies with or without spectroscopic redshifts. We also explore the effects of contamination by fainter overlapping objects in photo-z determination. The overall conclusion of this paper is that the acquisition of photometrically estimated redshifts with the precision required for Euclid, or other similar experiments, will be challenging but possibl

Leptonic decay of Heavy-light Mesons in a QCD Potential Model

We study the masses and decay constants of heavy-light flavour mesons D, Ds, B and Bs in a QCD Potential model. The mesonic wavefunction is used to compute the masses of D and B mesons in the ground state and the wavefunction is transformed to momentum space to estimate the pseudoscalar decay constants of these mesons. The leptonic decay widths and branching ratio of these mesons for different leptonic channels are also computed to compare with the experimental values. The results are found to be compatible with available data.Comment: 9 pages,3 table

Photo-z Performance for Precision Cosmology II : Empirical Verification

The success of future large scale weak lensing surveys will critically depend on the accurate estimation of photometric redshifts of very large samples of galaxies. This in turn depends on both the quality of the photometric data and the photo-z estimators. In a previous study, (Bordoloi et al. 2010) we focussed primarily on the impact of photometric quality on photo-z estimates and on the development of novel techniques to construct the N(z) of tomographic bins at the high level of precision required for precision cosmology, as well as the correction of issues such as imprecise corrections for Galactic reddening. We used the same set of templates to generate the simulated photometry as were then used in the photo-z code, thereby removing any effects of "template error". In this work we now include the effects of "template error" by generating simulated photometric data set from actual COSMOS photometry. We use the trick of simulating redder photometry of galaxies at higher redshifts by using a bluer set of passbands on low z galaxies with known redshifts. We find that "template error" is a rather small factor in photo-z performance, at the photometric precision and filter complement expected for all-sky surveys. With only a small sub-set of training galaxies with spectroscopic redshifts, it is in principle possible to construct tomographic redshift bins whose mean redshift is known, from photo-z alone, to the required accuracy of 0.002(1+z).Comment: 7 pages, 5 figures, accepted for publication in MNRA

A Mathematical and Experimental analysis of degradation of lubricating oil in four stroke Motorbikes

This paper presents a mathematical and experimental analysis of degradation of lubricating oil used in four-stroke motor bikes. For mathematical analysis, Debye equation have been related to the dielectric constant and temperature of lubricating oil samples of four stroke motorbikes The instrumentation system used for experimentation consists of (i) a coaxial cylindrical capacitor and a LM35 IC as sensors (ii) A ATmega 32 based microcontroller system for sampling, processing and display of signal. The coaxial cylindrical capacitive sensor and LM35 are used to provide the measure of dielectric constant and temperature of a lubricating oil sample

A Mathematical and Experimental analysis of degradation of lubricating oil in four stroke Motorbikes

This paper presents a mathematical and experimental analysis of degradation of lubricating oil used in four-stroke motor bikes. For mathematical analysis, Debye equation have been related to the dielectric constant and temperature of lubricating oil samples of four stroke motorbikes The instrumentation system used for experimentation consists of (i) a coaxial cylindrical capacitor and a LM35 IC as sensors (ii) A ATmega 32 based microcontroller system for sampling, processing and display of signal. The coaxial cylindrical capacitive sensor and LM35 are used to provide the measure of dielectric constant and temperature of a lubricating oil sample

Ornamental fisheries in Northeast India: State of the art and future directions

Not AvailableOrnamental fish keeping is a growing sector in aquaculture and still the 2nd most popular hobby comprising of 100 million of hobbyist in the world. More than 2500 fish species are involved in the global ornamental fish industry, where over 60% are of freshwater origin and 40% of marine origin. Out of the 422 fish species that have been reported for the Northeast region, 250 have the potential to be ornamental, with Assam having the largest number of ornamental fish species (187 species) recorded. Several species of fish can be considered as potential ornamental fish, at least during their early juvenile phase or during their breeding season. Wetlands/lakes of Assam and other Northeast states contribute a major portion in Ornamental fish diversity of Northeast India.Not Availabl

The COS-Dwarfs Survey: The Carbon Reservoir Around sub-L* Galaxies

We report new observations of circumgalactic gas from the COS-Dwarfs survey, a systematic investigation of the gaseous halos around 43 low-mass z $\leq$ 0.1 galaxies using background QSOs observed with the Cosmic Origins Spectrograph. From the projected 1D and 2D distribution of C IV absorption, we find that C IV absorption is detected out to ~ 0.5 R$_{vir}$ of the host galaxies. The C IV absorption strength falls off radially as a power law and beyond 0.5 R$_{vir}$, no C IV absorption is detected above our sensitivity limit of ~ 50-100 m$\AA$. We find a tentative correlation between detected C IV absorption strength and star formation, paralleling the strong correlation seen in highly ionized oxygen for L~L* galaxies by the COS-Halos survey. The data imply a large carbon reservoir in the CGM of these galaxies, corresponding to a minimum carbon mass of $\gtrsim$ 1.2$\times 10^6$ $M_\odot$ out to ~ 110 kpc. This mass is comparable to the carbon mass in the ISM and more than the carbon mass currently in stars of these galaxies. The C IV absorption seen around these sub-L* galaxies can account for almost two-thirds of all $W_r$> 100 m$\AA$ C IV absorption detected at low z. Comparing the C IV covering fraction with hydrodynamical simulations, we find that an energy-driven wind model is consistent with the observations whereas a wind model of constant velocity fails to reproduce the CGM or the galaxy properties.Comment: 18 Pages, 11 Figures, ApJ 796 13

Possible use of Punica granatum (Pomegranate) in cancer therapy

The intake of fruits has proven to reduce the risk and incidence of cancer worldwide and plays a crucial role in cancer prevention. Pomegranate (Punica granatum), which belongs to the Punicaceae family, is one such plant that contains beneficial nutrients as well as many bioactive components and important phytochemicals that can be attributed to cancer-related therapeutic purposes. Pomegranate possesses antioxidant, anti-inflammatory, anti-proliferative, anti-angiogenic, anti-invasive, and anti-metastatic properties, and induces apoptosis. It also down-regulates various signaling pathways such as NF-?B, PI3K/AKT/mTOR, and Wnt, and down-regulates the expression of genes that are responsible in cancer development, such as anti-apoptotic genes, MMPs, VEGF, c-met, cyclins, Cdks, and pro-inflammatory cytokines. Therefore, inclusion of the fruit in one's diet would assist in a healthy life protected from cancer and also act as an effective chemotherapeutic with no toxic side effects