Media Ownership Control: To What Extent Is Competition Law And Policy Sufficient to Provide for Diversity and Plurality in the Media?

In modern economies and societies, the availability of information is central to better decision making by citizens and consumers. In most countries, citizens and consumers receive the information they need through the media, including newspapers, television radio, internet and etc. After 1990s, technological and economic developments have evolved the media sector by converging it to telecommunications and IT sectors and by leading to new interactive broadcasting services transmitted by different technologies. These developments also increased mergers and joint ventures both at global level and national level. As well as these developments, the private benefits of media have increased concentration of ownership in these sectors. There are many people who argue that concentration in media markets has a negative effect on diversity and plurality. Because of increasing concentration in media markets in recent years all over the world, many concerns as to whether competition law and policy is sufficient to ensure the diversity and pluralism in media have arisen. Competition rules can address issues of concentration, efficiency and choice and will tend to encourage dispersed ownership and new entry. However, they cannot guarantee any of it. Competition law cannot therefore provide the certainty we need that a significant number of different media voices will continue to be heard, or that prospective new entrants to the market will be able to add their voice. Moreover, it cannot directly address concerns over editorial freedom or community voice. Therefore, if competition law and policy is assessed as a whole in the context of media, it can be stated that it guarantees diversity to some extent. However, because of the objectives and criteria of competition law is an important part of regulation, it is not designed to deliver diversity and plurality in the media. Special media ownership rules exist across the world because the market alone, even regulated by competition law, is not thought to provide the best results for society and for democracy.

SDSS Absolute Magnitudes for Thin Disc Stars based on Trigonometric Parallaxes

We present a new luminosity-colour relation based on trigonometric parallaxes for thin disc main-sequence stars in SDSS photometry. We matched stars from the newly reduced Hipparcos catalogue with the ones taken from 2MASS All-Sky Catalogue of Point Sources, and applied a series of constraints, i.e. relative parallax errors ($\sigma_{\pi}/\pi\leq0.05$), metallicity ($-0.30\leq[M/H]\leq0.20$ dex), age ($0\leq t \leq 10$ Gyr) and surface gravity ($\log g>4$), and obtained a sample of thin disc main-sequence stars. Then, we used our previous transformation equations (Bilir et al. 2008a) between SDSS and 2MASS photometries and calibrated the $M_{g}$ absolute magnitudes to the $(g-r)_{0}$ and $(r-i)_0$ colours. The transformation formulae between 2MASS and SDSS photometries along with the absolute magnitude calibration provide space densities for bright stars which saturate the SDSS magnitudes.Comment: 7 pages, including 7 figures and 2 tables, accepted for publication in MNRA

Luminosity-Colours relations for thin disc main-sequence stars

In this study we present the absolute magnitude calibrations of thin disc main-sequence stars in the optical ($M_{V}$), and in the near-infrared ($M_{J}$). Thin disc stars are identified by means of Padova isochrones, and absolute magnitudes for the sample are evaluated via the newly reduced Hipparcos data. The obtained calibrations cover a large range of spectral types: from A0 to M4 in the optical and from A0 to M0 in the near-infrared. Also, we discuss the of effects binary stars and evolved stars on the absolute magnitude calibrations. The usage of these calibrations can be extended to the estimation of galactic model parameters for the thin disc individually, in order to compare these parameters with the corresponding ones estimated by $\chi{^2}_{min}$ statistics (which provides galactic model parameters for thin and thick discs, and halo simultaneously) to test any degeneracy between them. The calibrations can also be used in other astrophysical researches where distance plays an important role in that study.Comment: 8 pages, including 12 figures and 4 tables, accepted for publication in MNRA

Absolute Magnitude Calibration for Giants based on the Colour-Magnitude Diagrams of Galactic Clusters. II-Calibration with SDSS

We present an absolute magnitude calibration for red giants with the colour magnitude diagrams of six Galactic clusters with different metallicities i.e. M92, M13, M3, M71, NGC 6791 and NGC 2158. The combination of the absolute magnitudes of the red giant sequences with the corresponding metallicities provides calibration for absolute magnitude estimation for red giants for a given $(g-r)_{0}$ colour. The calibration is defined in the colour interval 0.45 $\leq(g-r)_{0}\leq$ 1.30 mag and it covers the metallicity interval $-2.15\leq \lbrack Fe/H \rbrack \leq$ +0.37 dex. The absolute magnitude residuals obtained by the application of the procedure to another set of Galactic clusters lie in the interval $-0.28< \Delta M \leq +0.43$ mag. However, the range of 94% of the residuals is shorter, $-0.1<\Delta M \leq+0.4$ mag. The mean and the standard deviation of (all) residuals are 0.169 and 0.140 mag, respectively. The derived relations are applicable to stars older than 2 Gyr, the age of the youngest calibrating cluster.Comment: 12 pages, including 5 figures and 10 tables, accepted for publication in PASA. arXiv admin note: substantial text overlap with arXiv:1204.429

Population types of cataclysmic variables in the solar neighborhood

The Galactic orbital parameters of 159 cataclysmic variables in the Solar neighbourhood are calculated, for the first time, to determine their population types using published kinematical parameters. Population analysis shows that about 6 per cent of cataclysmic variables in the sample are members of the thi ck disc component of the Galaxy. This value is consistent with the fraction obt ained from star count analysis. The rest of the systems in the sample are found to be in the thin disc component of the Galaxy. Our analysis revealed no halo CVs in the Solar vicinity. About 60 per cent of the thick disc CVs have orbital periods be low the orbital period gap. This result is roughly consistent with the predictions of population synthesis models developed for cataclysmic variables. A kinematical age of 13 Gyr is obtained using total space velocity dispersion of the most probable thick disc CVs which is consistent with the age of thick disc component of the Galaxy

New colour-transformations for the Sloan photometry and revised metallicity calibration and equations for photometric parallax estimation

We evaluated new colour-transformations for the Sloan photometry by 224 standards and used them to revise both the equations for photometric parallax estimation and metallicity calibration cited by Karaali et al. (2003). This process improves the metallicity and absolute magnitude estimations by [Fe/H]<=0.3 dex and M^{H}_{g} <= 0.1 mag respectively. There is a high correlation for metallicities and absolute magnitudes derived for two systems, UBV and Sloan, by means of the revised calibrations.Comment: 11 pages, including 7 figures and 2 tables, accepted for publication in PAS

Estimation of Galactic Model Parameters and Metalicity Distribution in Intermediate Latitudes with SDSS

We estimated the galactic model parameters for a set of 20 intermediate-latitude fields with galactic longitudes 0<l<100 and 160<l<240, included in the currently available Data Release 6 (DR6) of SDSS, to explore their possible variation with galactic longitude. The local space densities of the thick disc and halo are almost the same for all fields, =6.52% and =0.35%, respectively, a result different than the one cited for high-latitude fields. The thin disc's scaleheight is 325 pc in the galactic centre changes to 369 pc in the third quadrant, which confirms the existence of disc flare, whereas the thick disc scaleheight is as large as 952 pc at galactic longitude l=20 and 10% lower at l=160, which confirms the existence of the disc long bar in the direction l=27. Finally, the variation of the axis ratio of the halo with galactic longitude is almost flat, =0.56, except a slight minimum and a small maximum in the second and third quadrants, respectively, indicating an effect of the long bar which seems plausible for a shallow halo. We estimated the metallicities of unevolved G-type stars and discussed the metallicity gradient for different vertical distances. The metallicity gradient is d[M/H]/dz=-0.30 dex kpc$^{-1}$ for short distances, confirming the formation of this region of the Galaxy by dissipational collapse. However, its change is steeper in the transition regions of different galactic components. The metallicity gradient is almost zero for inner halo (5<z<10 kpc), indicating a formation of merger or accretion of numerous fragments such as dwarf galaxies.Comment: 31 pages, 18 figures and 4 tables, accepted for publication in New Astronom

Spatial distribution and galactic model parameters of cataclysmic variables

The spatial distribution, galactic model parameters and luminosity function of cataclysmic variables (CVs) in the solar neighbourhood have been determined from a carefully established sample of 459 CVs. The sample contains all of the CVs with distances computed from the Period-Luminosity-Colours (PLCs) relation of CVs which has been recently derived and calibrated with {\em 2MASS} photometric data. It has been found that an exponential function fits best to the observational z-distributions of all of the CVs in the sample, non-magnetic CVs and dwarf novae, while the sech^{2} function is more appropriate for nova-like stars and polars. The vertical scaleheight of CVs is 158$\pm$14 pc for the {\em 2MASS} J-band limiting apparent magnitude of 15.8. On the other hand, the vertical scaleheights are 128$\pm$20 and 160$\pm$5 pc for dwarf novae and nova-like stars, respectively. The local space density of CVs is found to be $\sim3\times10^{-5}$ pc^{-3} which is in agreement with the lower limit of the theoretical predictions. The luminosity function of CVs shows an increasing trend toward higher space densities at low luminosities, implying that the number of short-period systems should be high. The discrepancies between the theoretical and observational population studies of CVs will almost disappear if for the z-dependence of the space density the sech^{2} density function is used.Comment: 29 pages, 9 figures and 5 tables, accepted for publication in New Astronom