Cosmological number density n(z) in depth z from p(V/Vm) distribution

Using distribution p(V/Vm) of V/Vm rather than just mean in V/Vm-test leads directly to cosmological number density n(z). Calculation of n(z) from p(V/Vm) is illustrated using best sample (of 76 quasars) available in 1981, when method was developed. This is only illustrative, sample being too small for any meaningful results. Keywords: V/Vm . luminosity volume . cosmological number density . V/Vm distributionComment: 2 pages, 2 tables, briefest version for Proceedings of 27th Meeting of Astronomical Society of India, Bangaluru, 18-20th February 200

Newtonian mechanics & gravity fully model disk galaxy rotation curves without dark matter

EGRET gamma-ray archival data used with GALPROP software show two ringlike structures in Milky Way Plane which roughly tally with distribution of stars ([1] & references therein). To understand fully the implications of this and similar results on detailed structure and rotation curve of especially Milky Way Disk as well as rotation curves of other galaxies as derived from spatially resolved spectroscopic data-cubes, a re-examination of the basis of the connection between mass density and rotation curve is warranted. Kenneth F. Nicholson's approach [2], which uses only Newtonian dynamics & gravity, is presented.Comment: 6 pages, 5 figures, 1 table (Currently visiting Solid State Theory group at University of Muenster, Germany), For IAU Symposium 254 on Galaxy Disk in Cosmological Context, 9-14 June 2008, Copenhagen, Denmar

Need for context-aware computing in astrophysics

The example of disk galaxy rotation curves is given for inferring dark matter from redundant computational procedure because proper care of astrophysical and computational context was not taken. At least three attempts that take the context into account have not found adequate voice because of haste in wrongly concluding existence of dark matter on the part of even experts. This firmly entrenched view, prevalent for about 3/4ths of a century, has now become difficult to correct. The right context must be borne in mind at every step to avoid such a situation. Perhaps other examples exist. Keywords: dark matter; disk galaxy; rotation curve; context-awareness. Topics: Algorithms; Applications.Comment: 3 pages, 1 figure, for: 15th Annual IEEE International Conference on High Performance Computing - Main Conferenc

Relation between positional & strength asymmetries of double radio sources associated with active galaxies

We bring out the identity between two ways of defining a single parameter to combine positional & strength asymmetries of extended extragalactic double radio sources associated with active galaxies. Thus, (r.s - 1)/[(1 + r).(1 + s)], combining arm ratio r (defined to be <= 1, i.e., shorter to longer arm) & strength ratio s (in the sense closer to farther, so that it may be or = 1), is identical to -(1/2)[(1 - fr)/(1 + fr) - t], where fr is strength ratio defined >= 1 (i.e., stronger to weaker), & t = +/- (Q - 1)/(Q + 1), +/- signs applying respectively to doubles with closer hotspot fainter & those with closer hotspot brighter, while Q is arm ratio defined >= 1. Keywords: active galaxies - double radio sources - bilateral symmetry - arm ratio - flux ratioComment: 3 page

The luminosity-volume method : Derivation of the cosmological number density in depth from V/Vm distribution [Number density in depth from luminosity-volume]

The classical cosmological V/Vm-test is introduced and elaborated. Use of the differential distribution p(V/Vm) of the V/Vm-variable rather than just the mean leads directly to the cosmological number density without any need for assumptions about the cosmological evolution of the underlying (quasar) population. Calculation of this number density n(z) from p(V/Vm) is illustrated using the best sample that was available in 1981, when this method was developed. This sample of 76 quasars is clearly too small for any meaningful results. The method will be later applied to a much larger cosmological sample to infer the cosmological number density n(z) as a function of the depth z. Keywords: V/Vm . luminosity volume . cosmological number density . V/Vm distributionComment: 8 pages, 3 table

Getting more out of V/Vm than just the mean

Banhatti (2009) set down the procedure to derive cosmological number density n(z) from the differential distribution p(x) of the fractional luminosity volume relative to the maximum volume, x \equiv V/Vm (0 \leq x \leq 1), using a small sample of 76 quasars for illustrative purposes. This procedure is here applied to a bigger sample of 286 quasars selected from Parkes half-Jansky flat-spectrum survey at 2.7 GHz (Drinkwater et al 1997). The values of n(z) are obtained for 8 values of redshift z from 0 to 3.5. The function n(z) can be interpreted in terms of redshift distribution obtained by integrating the radio luminosity function {\rho}(P, z) over luminosities P for the survey limiting flux density S0 = 0.5 Jy. Keywords. V/Vm - luminosity-volume - cosmological number density - redshift distribution - luminosity function - quasars [Note: This somewhat modified version was submitted to MNRaS on 14 July 2016. It was (almost) rejected, except if thoroughly revised.]Comment: 4 pages, 3 tables, 5 references. Abstract submitted & paper accepted as poster (with a different title) for 29th Meeting of Astronomical Society of India at Pt Ravishankar Shukla University, Raipur, Chhattisgarh State, India, February 201

Occultation of the radio source 2019+098 (3C411) by comet 1983e (Sugano-Saigusa-Fujikawa)

[This cometary occultation observation from June 1983 remained to be formally reported due to other preoccupations of the authors. It was presented in seminars to colleagues at Ooty, Bangalore and elsewhere. We now write it up as we have been asked about it by various colleagues at various times, and feel we owe it to them to put it firmly on record.] We planned and observed with Ooty Radio Telescope the occultation with Comet 1983e Sugano-Saigusa-Fujikawa of the extragalactic radio source 2019+098 = 3C411. The results are presented formally for the first time, along with a brief account of other cometary occultations and general background of planning, execution and interpretation of such observations which will be useful for other future observers. The occultation occurred at 07:52 IST on 12th June 1983. It amounted to 25% peak to peak fluctuation in the flux density of the radio source. The rough predicted occultation time was 07:24 IST. We interpret the results after refining the occultation time to allow for various effects.Comment: 9 pages, 4 figures, 2 tables, paper to be enhanced shortl

Mass Distribution, Rotation Curves and Gravity Theories

{Comparison of mass density profiles of galaxies of varying sizes based on some gravity theories from observed galaxy rotation curves and assessing the need for dark matter.} We present an analysis of the rotation curves of five galaxies of varying galactic radii: NGC6822 (4.8 kpc), Large Magellanic Cloud (9 kpc), The Milky Way (17 kpc), NGC3198 (30 kpc) and UGC9133 (102.5 kpc). The mass and mass density profiles of these galaxies have been computed using the scientific computing s/w package MATLAB taking the already available velocity profiles of the galaxies as the input, and without considering any Dark Matter contribution. We have plotted these profiles after computing them according to three different theories of gravity (and dynamics): Newtonian (black line), Modified Newtonian Dynamics (MoND) (green line) and Vacuum Modified Gravity (red line). We also consider how the profile due to the Newtonian theory would modify if we take into account a small negative value of the Cosmological Constant (5 x 10^-56 cm^-2 from theory) (blue line). Comparing these mass and mass density profiles, we try to form an idea regarding what could be a realistic theory of gravity and whether we need Dark Matter to explain the results. Keywords : disk galaxy rotation curves, galaxy mass, mass density profile, dark matter, Newtonian theory, MoND, Vacuum Modified Gravity, negative cosmological constantComment: 59pp, 47 figures, 5 tables, 9 refs. Mainly added figures with self-explanatory captions from earlier to this version. In case of any queries about calculation method as presented in this version, see previous version. Also see previous version for condensed figure

Application of slingshot model to the giant radio galaxy DA240 (Brief : DA 240 in slingshot model)

We attempt a slingshot model interpretation of the unusual association of some 1&1/3 dozen nonstellar galaxian objects around the parent optical galaxy of the giant radio galaxy DA 240 (= 0748.6+55.8 (J2000)). Similar interpretation may be possible for another large radio galaxy 3C 31 (= NGC 383 = 0104.6+32.1 (1950.0)).Comment: 6 pages, 2 figures, based on S Muthumeenal's 2007 MPhil project; Keywords. active galaxy - radio galaxy - beam model - slingshot mode

Exergy - a useful concept for ecology and sustainability

We present the relatively less known thermodynamic concept of exergy in the context of ecology and sustainability. To this end, we first very briefly outline thermodynamics as it arose historically via engineering studies. This enables us to define exergy as available energy. An example of applying the concept of exergy to a simple human process is next described. Then we present an exergy analysis of Earth as a flow system, also concurrently describing other necessary concepts. Finally, we briefly comment on the applicability of exergy analysis to ecology and sustainability. Keywords: exergy - energy - work - thermodynamics - heat transfer - flow processesComment: 13 pages, 15 figures, Presented at International Humboldt Kolleg at Institute for Social & Economic Change, Bengaluru, 19-21 October 2011. (First author added & paper modified from earlier version accordingly.