Harmonizing the RR Lyrae and Clump Distance Scales - Stretching the Short Distance Scale to Intermediate Ranges?

I explore the consequences of making the RR Lyrae and clump giant distance scales consistent in the solar neighborhood, Galactic bulge and Large Magellanic Cloud (LMC). I employ two major assumptions: 1) that the absolute magnitude - metallicity, M_V(RR) - [Fe/H], relation for RR Lyrae stars is universal, and 2) that absolute I-magnitudes of clump giants, M_I(RC), in Baade's Window are known (e.g., can be inferred from the local Hipparcos-based calibration or theoretical modeling). A comparison between the solar neighborhood and Baade's Window sets M_V(RR) at [Fe/H] = -1.6 in the range (0.59 +/- 0.05, 0.70 +/- 0.05), somewhat brighter than the statistical parallax solution. More luminous RR Lyrae stars imply younger ages of globular cluster, which would be in better agreement with the conclusions from the currently favored stellar evolution and cosmological models. A comparison between Baade's Window and the LMC sets the M_I^{LMC}(RC) in the range (-0.33 +/- 0.09, -0.53 +/- 0.09). The distance modulus to the LMC, mu^{LMC}, is between 18.24 +/- 0.08 and 18.44 +/- 0.07. Unlike M_I^{LMC}(RC), this range in mu^{LMC} does NOT depend on the adopted value of the dereddened LMC clump magnitude, I_0^{LMC}(RC). I argue that the currently available information is insufficient to select the correct distance scale with high confidence.Comment: version accepted to MNRAS, added discussion about the dependence of the results on theoretical assumptions and observational input, stressed that the derived range of the LMC distance modulus between 18.24 and 18.44 is insensitive to the controversial dereddened I-magnitude of the LMC clump giant

The Distance to the Large Magellanic Cloud

I demonstrate that the two unexpected results in the local Universe: anomalous intrinsic (V-I)_0 colors of RR Lyrae stars and clump giants in the Galactic center, and very short distances to Magellanic Clouds inferred from clump giants, can be at least partially resolved with a modified coefficient of selective extinction A_V/E(V-I). With this modification, I find a new clump-giant distance modulus to the Large Magellanic Cloud, mu_{LMC} = 18.27 +/- 0.07, which is 0.09 larger than the Udalski (1998b) result. When distance estimates from the red clump, RR Lyrae stars and the eclipsing binary HV2274 are combined, one obtains mu_{LMC} = 18.31 +/- 0.04 (internal).Comment: less detailed and more review-style version of ApJ Letter (528, L9), to be published in the ASP Conference Series Vol. 203, 1999: ``The Impact of Large Scale Surveys on Pulsating Star Research'', L. Szabados and D. Kurtz, ed

A Test for the Origin of Quasar Redshifts

It is commonly accepted that quasar redshifts have a cosmological character and that most of the quasars are at Gigaparsec distances. However, there are some cases where several quasars with completely different redshifts and a nearby active galaxy are aligned in a certain way or occupy a very small patch on the sky, which is claimed by some authors to be unlikely to happen by chance. Is there a small subset of quasars with non-cosmological redshifts? For quasars apparently associated with galaxies, we consider two scenarios for the origin of their redshift: 1. a standard, cosmological scenario, 2. a velocity-induced Doppler shift of a nearby object's spectrum (local, ejection scenario). We argue for a simple astrometric test which can distinguish between these two sources of quasar redshifts by constraining their proper motions. We give the predictions for the maximum possible proper motions of a quasar for the cosmological and local scenarios of the origin of their redshifts. We apply these theoretical results to the Bukhmastova (2001) catalog, which contains more than 8000 close QSO-galaxy associations. In the standard interpretation of quasar redshifts, their typical proper motions are a fraction of micro arc-second, and beyond the reach of planned astrometric missions like GAIA and SIM. On the other hand, the quasars ejected from local AGNs at velocities close to the speed of light would have proper motions 5-6 orders of magnitude larger, which would easily be measurable with future astrometric missions. The distributions of proper motions for the cosmological and local scenarios are very well separated. Moreover, the division corresponds nicely to the expected accuracy from GAIA and SIM.Comment: results unchanged, minor additions, 10 pages, 6 figures, 1 table, accepted to MNRA

Total to Selective Extinction Ratios and Visual Extinctions from Ultraviolet Data

We present determinations of the total to selective extinction ratio R_V and visual extinction A_V values for Milky Way stars using ultraviolet color excesses. We extend the analysis of Gnacinski and Sikorski (1999) by using non-equal weights derived from observational errors. We present a detailed discussion of various statistical errors. In addition, we estimate the level of systematic errors by considering different normalization of the extinction curve adopted by Wegner (2002). Our catalog of 782 R_V and A_V values and their errors is available in the electronic form on the World Wide Web.Comment: 20 pages, 7 figures, submitted to Acta Astronomic

Correcting Parameters of Events Based on the Entropy of Microlensing Ensemble

We entertain the idea that robust theoretical expectations can become a tool in removing hidden observational or data-reduction biases. We illustrate this approach for a specific problem associated with gravitational microlensing. Using the fact that a group is more than just a collection of individuals, we derive formulae for correcting the distribution of the dimensionless impact parameters of events, u_min. We refer to the case when undetected biases in the u_min distribution can be alleviated by multiplication of impact parameters of all events by a common constant factor. We show that in this case the general maximum likelihood problem of solving an infinite number of equations reduces to two constraints, and we find an analytic solution. Under the above assumptions, this solution represents a state in which the ``entropy'' of a microlensing ensemble is at its maximum, that is, the distribution of u_min resembles a specific, theoretically expected, box-like distribution to the highest possible extent. We also show that this technique does not allow one to correct the parameters of individual events on the event by event basis independently from each other.Comment: 16 pages, version accepted by ApJ, results unchanged, additional discussion regarding conditions suitable for application of the presented metho

An introduction to economic analysis in medicine - the basics of methodology and chosen terms. Examples of results of evaluation in nuclear medicine

This article overviews the basic terms and methodology approaches in economic analysis in medicine: cost-benefit analysis, cost-effectiveness analysis, cost-utility analysis and costminimisation analysis. Particular emphasis is put on nuclear medicine economic evaluation, e.g. FDG - PET studies, sestamibi breast cancer imaging and radioiodine therapy of hyperthyroidism

The Extinction Toward the Galactic Bulge from RR Lyrae Stars

We present mean reddenings toward 3525 RR0 Lyrae stars from the Galactic bulge fields of the MACHO Survey. These reddenings are determined using the color at minimum V-band light of the RR0 Lyrae stars themselves and are found to be in general agreement with extinction estimates at the same location obtained from other methods. Using 3256 stars located in the Galactic Bulge, we derive the selective extinction coefficient RV,VR = AV/E(V − R) = 4.3 ± 0.2. This value is what is expected for a standard extinction law with RV,BV = 3.1 ± 0.3