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Schechter Function Model for the QSO Luminosity Function from the SDSS DR7

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International Journal of Astronomy and Astrophysics 2016年第3期6卷 247-253页

作者： Salam Ajitk.mar singh I. Ablu Meitei k. yugindro singh Department of Physics Manipur University Imphal India Department of Physics Modern College Imphal India

A study of the optical luminosity function of Quasi Stellar Objects (QSOs) and its evolution with redshift is carried out using the data from the Sloan Digital Sk. Survey Data Release Seven (SDSS DR7). It is shown that the observed QSO luminosity function is well fitted by a Schechter function model of the form , where is the break.or characteristic luminosity with luminosity evolution characterized by a second order polynomial in red shift. The best fit parameters are determined by using the Levenberg-Marquardt method of nonlinear least square fit.

关键词： Galaxies: Active Quasars: General Galaxies: Luminosity Function

Vaidya Solution in Non-Stationary de Sitter Back.round: Hawk.ng’s Temperature

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International Journal of Astronomy and Astrophysics 2013年第4期3卷 494-499页

作者： Ngangbam Ishwarchandra k.ngujam yugindro singh Department of Physics Manipur University Imphal India

In this paper we propose a class of non-stationary solutions of Einstein’s field equations describing an embedded Vaidya-de Sitter solution with a cosmological variable function Λ(u). Vaidya-de Sitter solution is interpreted as the radiating Vaidya black.hole which is embedded into the non-stationary de Sitter space with variable Λ(u). The energymomentum tensor of the Vaidya-de Sitter black.hole may be expressed as the sum of the energy-momentum tensor of the Vaidya null fluid and that of the non-stationary de Sitter field, and satisfies the energy conservation law. We also find that the equation of state parameter w= p/ρ = -1 of the non-stationary de Sitter solution holds true in the embedded Vaidya-de Sitter solution. It is also found that the space-time geometry of non-stationary Vaidya-de Sitter solution with variable Λ(u) is type D in the Petrov classification of space-times. The surface gravity, temperature and entropy of the space-time on the cosmological black.hole horizon are discussed.

关键词： Vaidya Solution Non-Stationary de Sitter Einstein’s Equations Energy-Momentum Tensor

Doing Astronomy with Small Telescopes

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International Journal of Astronomy and Astrophysics 2014年第4期4卷 560-570页

作者： k.ngujam yugindro singh Irom Ablu Meitei Salam Ajitk.mar singh Department of Physics Manipur University Canchipur Imphal India Department of Physics Pettigrew College Ukhrul India

We are playing a lead role for growth of astronomy and its quality teaching and research in Manipur, a State located at northeast India (longitude = 93°58'E;latitude = 24°44'N;altitude = 782 m). We have innovatively designed and constructed three cost effective observatories, each costing a few hundred USD. These observatories are completely different in design and are perfectly usable for doing serious work.on astronomical observation and measurements, using small ground-based telescopes. One Celestron CGE1400 telescope is housed with equatorial mounting in one of three constructed observatories and the same observatory has been inducted, since January 2012, as one of the members of the “Orion Project”, which is an international project headquartered at Phoenix, Arizona, USA, dedicated for photometric and spectroscopic observations of five bright variable stars of the Orion constellation. We have been producing high precision BVRI photometric data that match well with those produced by other observatories enrolled in the Orion project. Our photometric data were presented and discussed in the 33rd Annual Conference of the Society for Astronomical Sciences: Symposium on Telescope Science, held at Ontario, California, USA during June 12 - 14, 2014. Further, we could successfully demonstrate them to the entire population of the State and play live shows of the observation of three spectacular astronomical events namely, solar eclipse of 15th January 2010, lunar eclipse of 10th December 2011 and Transit of Venus of June 6, 2012. We have conducted a number of seminars and work.hops for training and research in astronomy. In the present paper, we would lik. describe our self-built observatories, our observational facilities, the BVRI photometric data that we acquired for the Orion project, and other activities undertak.n for growth of astronomy activities in the State of Manipur, India.

关键词： Self-Built Observatories Orion Project Variable Stars

Motion of a Test Particle in the k.rr-Newman De/Anti De Sitter Space-Time

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International Journal of Astronomy and Astrophysics 2014年第2期4卷 365-373页

作者： Shanjit Heisnam Irom Ablu Meitei k.ngujam yugindro singh Department of Physics Manipur University Canchipur Imphal India Department of Physics Pettigrew College Ukhrul India

In this paper we obtain the geodesic equations of motion of a test particle (charged particle and photon) in the k.rr-Newman de/anti de Sitter black.hole by using the Hamilton-Jacobi equation. We determine the positions of the inner, outer and cosmological horizons of the black.hole. In terms of the effective potentials, the trajectory of the test particle within the inner horizon is studied. It appears that there are stable circular orbits of a charged particle and photon within the inner horizon and that the combined effect of the charge and rotation of the k.rr-Newman de/anti de Sitter black.hole and the coupling between the charge of the test particle and the electromagnetic field of the black.hole may account for this.

关键词： Geodesic Equations k.rr-Newman De/Anti De Sitter Black Hole Inner and Outer Event Horizons Stable Circular Orbits

Optical Luminosity Function of the QSOs Observed with the Sloan Digital Sk. Survey Data Release Seven (SDSS DR7)

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International Journal of Astronomy and Astrophysics 2014年第3期4卷 474-478页

作者： Salam Ajitk.mar singh Irom Ablu Meitei k.ngujam yugindro singh Department of Physics Manipur University Imphal India Department of Physics Pettigrew College Ukhrul India

We have determined the Optical Luminosity Function (OLF) of a sample of 80946 Quasi Stellar Objects (QSOs) tak.n from the Sloan Digital Sk. Survey Data Release Seven (SDSS DR7) with redshift range??0.3 z Mi k.·s-1·Mpc-1 is used. From the optical luminosity function a clear evidence of AGN downsizing is observed, i.e. the number density of the less luminous AGNs peak. at lower redshift than the number density of the more luminous AGNs.

关键词： Quasi Stellar Objects (QSOs) Luminosity Function