University of Arizona

About: University of Arizona is a education organization based out in Tucson, Arizona, United States. It is known for research contribution in the topics: Population & Galaxy. The organization has 63805 authors who have published 155998 publications receiving 6854915 citations. The organization is also known as: UA & U of A.

Atlas of quasar energy distributions

Abstract: We present an atlas of the spectral energy distributions (SEDs) of normal, nonblazar, quasars over the whole available range (radio to 10 keV X-rays) of the electromagnetic spectrum. The primary (UVSX) sample includes 47 quasars for which the spectral energy distributions include X-ray spectral indices and UV data. Of these, 29 are radio quiet, and 18 are radio loud. The SEDs are presented both in figures and in tabular form, with additional tabular material published on CD-ROM. Previously unpublished observational data for a second set of quasars excluded from the primary sample are also tabulated. The effects of host galaxy starlight contamination and foreground extinction on the UVSX sample are considered and the sample is used to investigate the range of SED properties. Of course, the properties we derive are influenced strongly by the selection effects induced by quasar discovery techniques. We derive the mean energy distribution (MED) for radio-loud and radio-quiet objects and present the bolometric corrections derived from it. We note, however, that the dispersion about this mean is large (approximately one decade for both the infrared and ultraviolet components when the MED is normalized at the near-infrared inflection). At least part of the dispersion in the ultraviolet may be due to time variability, but this is unlikely to be important in the infrared. The existence of such a large dispersion indicates that the MED reflects only some of the properties of quasars and so should be used only with caution.

Central masses and broad-line region sizes of active galactic nuclei. ii. a homogeneous analysis of a large reverberation-mapping database

Abstract: We present improved black hole masses for 35 active galactic nuclei (AGNs) based on a complete and consistent reanalysis of broad emission-line reverberation-mapping data From objects with multiple line measurements, we find that the highest precision measure of the virial product cτΔV2/G, where τ is the emission-line lag relative to continuum variations and ΔV is the emission-line width, is obtained by using the cross-correlation function centroid (as opposed to the cross-correlation function peak) for the time delay and the line dispersion (as opposed to FWHM) for the line width and by measuring the line width in the variable part of the spectrum Accurate line-width measurement depends critically on avoiding contaminating features, in particular the narrow components of the emission lines We find that the precision (or random component of the error) of reverberation-based black hole mass measurements is typically around 30%, comparable to the precision attained in measurement of black hole masses in quiescent galaxies by gas or stellar dynamical methods Based on results presented in a companion paper by Onken et al, we provide a zero-point calibration for the reverberation-based black hole mass scale by using the relationship between black hole mass and host-galaxy bulge velocity dispersion The scatter around this relationship implies that the typical systematic uncertainties in reverberation-based black hole masses are smaller than a factor of 3 We present a preliminary version of a mass-luminosity relationship that is much better defined than any previous attempt Scatter about the mass-luminosity relationship for these AGNs appears to be real and could be correlated with either Eddington ratio or object inclination

Word-of-Mouth for Movies: Its Dynamics and Impact on Box Office Revenue

Abstract: This paper uses actual WOM information to examine the dynamic patterns of WOM and how it helps explain box office revenue. The WOM data was collected from the website of Yahoo! Movies. The results show that WOM activities are the most active during pre-release and the opening week, and that movie audiences tend to hold relatively high expectation before release, but become more critical in the opening week. More importantly, WOM information offers significant explanatory power for both aggregate and weekly box office revenue, especially in the early weeks after opening. However, most of this explanatory power comes from the volume of WOM, not its valence as measured by the percentages of positive and negative messages.

Global vegetation change through the Miocene/Pliocene boundary

Abstract: Between 8 and 6 million years ago, there was a global increase in the biomass of plants using C4 photosynthesis as indicated by changes in the carbon isotope ratios of fossil tooth enamel in Asia, Africa, North America and South America. This abrupt and widespread increase in C4 biomass may be related to a decrease in atmospheric CO2 concentrations below a threshold that favoured C3-photosynthesizing plants. The change occurred earlier at lower latitudes, as the threshold for C3 photosynthesis is higher at warmer temperatures.