The Problem of Personal Income Tax Avoidance

The aim of this study is to analyze the concept of antiracism and explore what characterizes the kind of antiracism that the empirical examples presented in this study represent. The empirical examples are instances of what I call antiracist actors. They are rooted in civil society, but also have strong connections with the government through government funding. The empirical data has been gathered through both qualitative and quantitative methods, mainly in the form of a survey and interviews. In order to explore the antiracist actors I have focused on three themes: (1) the shapes and forms of racism, (2) antiracism as a phenomenon, and (3) antiracism as a social arena. Through these themes I have gathered information about how the antiracist actors interpret their activities and the context in which they are working. On the subject of the shapes and forms of racism, I establish that racism is a concept that is hard to define. The antiracist actors lack a common language regarding racism, which affects the antiracist rhetoric. Regarding antiracism as a phenomenon, I conclude that the antiracist strategies mainly consist of three components: (1) knowledge is used as a strategic instrument internally to strengthen the volunteers, (2) knowledge is spread externally to increase awareness of racism, and (3) the antiracist actors deconstruct racist beliefs when opposing racist opinions. Finally, I research antiracism as a social arena and study civil society and theories about social movements in order to explore organizational aspects of the antiracist actors. Using Alberto Meluccis’ social movement theories, there is some evidence to support the thesis that the antiracist actors could be defined as part of an antiracist movement. However, overall there are stronger arguments to suggest the opposite, mainly since the antiracist actors are not in opposition to one or more adversaries. Instead they work with target groups, sometimes targeting the general public, sometimes specific groups like children in a certain school. The main conclusion from my study in this respect is that the antiracist actors are part of what I call association-driven antiracism. The associationdriven antiracism is characterized by non-violent methods and the antiracist actors do not focus on racist adversaries, instead they work with target groups trying to influence them in an antiracist way. The association-driven antiracism secures its continuity through networks, since many activities are project-based and only last for a limited period of time. Also, the antiracist actors are not representatives of particular political parties, instead they gather around the question at hand, antiracism. The antiracist actors within the association-driven antiracism are in close collaboration with the government and partly finance their activities with government funding. This collaboration can be explained as a positive steering process, the rulers (the government) and those who are ruled (the antiracist actors) agree on an antiracist ideology and work in the same direction

The Quantity of Intracluster Light: Comparing Theoretical and Observational Measurement Techniques Using Simulated Clusters

Using a suite of N-body simulations of galaxy clusters specifically tailored to study the intracluster light (ICL) component, we measure the quantity of ICL using a number of different methods previously employed in the literature for both observational and simulation data sets. By measuring the ICL of the clusters using multiple techniques, we identify systematic differences in how each detection method identifies the ICL. We find that techniques which define the ICL solely based on the current position of the cluster luminosity, such as a surface brightness or local density threshold, tend to find less ICL than methods utilizing time or velocity information, including stellar particles' density history or binding energy. The range of ICL fractions (the fraction of the clusters' total luminosity found in the ICL component) we measure at z=0 across all our clusters using any definition span the range from 9-36%, and even within a single cluster different methods can change the measured ICL fraction by up to a factor of two. Separating the cluster's central galaxy from the surrounding ICL component is a challenge for all ICL techniques, and because the ICL is centrally concentrated within the cluster, the differences in the measured ICL quantity between techniques are largely a consequence of this central galaxy/ICL separation. We thoroughly explore the free parameters involved with each measurement method, and find that adjusting these parameters can change the measured ICL fraction by up to a factor of two. While for all definitions the quantity of ICL tends to increase with time, the ICL fraction does not grow at a uniform rate, nor even monotonically under some definitions. Thus, the ICL can be used as a rough indicator of dynamical age, where more dynamically advanced clusters will on average have higher ICL fractions.Comment: 18 pages, 11 figues. Accepted for publication in Ap

Spitzer IRAC Low Surface Brightness Observations of the Virgo Cluster

We present 3.6 and 4.5 micron Spitzer IRAC imaging over 0.77 square degrees at the Virgo cluster core for the purpose of understanding the formation mechanisms of the low surface brightness intracluster light features. Instrumental and astrophysical backgrounds that are hundreds of times higher than the signal were carefully characterized and removed. We examine both intracluster light plumes as well as the outer halo of the giant elliptical M87. For two intracluster light plumes, we use optical colors to constrain their ages to be greater than 3 & 5 Gyr, respectively. Upper limits on the IRAC fluxes constrain the upper limits to the masses, and optical detections constrain the lower limits to the masses. In this first measurement of mass of intracluster light plumes we find masses in the range of 5.5 x 10^8 - 4.5 x 10^9 and 2.1 x 10^8 - 1.5 x 10^9 solar masses for the two plumes for which we have coverage. Given their expected short lifetimes, and a constant production rate for these types of streams, integrated over Virgo's lifetime, they can account for the total ICL content of the cluster implying that we do not need to invoke ICL formation mechanisms other than gravitational mechanisms leading to bright plumes. We also examined the outer halo of the giant elliptical M87. The color profile from the inner to outer halo of M87 (160 Kpc) is consistent with either a flat or optically blue gradient, where a blue gradient could be due to younger or lower metallicity stars at larger radii. The similarity of the age predicted by both the infrared and optical colors (> few Gyr) indicates that the optical measurements are not strongly affected by dust extinction.Comment: 16 pages including appendix, 9 figures, ApJ accepte

Optical Colors of Intracluster Light in the Virgo Cluster Core

We continue our deep optical imaging survey of the Virgo cluster using the CWRU Burrell Schmidt telescope by presenting B-band surface photometry of the core of the Virgo cluster in order to study the cluster's intracluster light (ICL). We find ICL features down to mu_b ~ 29 mag sq. arcsec, confirming the results of Mihos et al. (2005), who saw a vast web of low-surface brightness streams, arcs, plumes, and diffuse light in the Virgo cluster core using V-band imaging. By combining these two data sets, we are able to measure the optical colors of many of the cluster's low-surface brightness features. While much of our imaging area is contaminated by galactic cirrus, the cluster core near the cD galaxy, M87, is unobscured. We trace the color profile of M87 out to over 2000 arcsec, and find a blueing trend with radius, continuing out to the largest radii. Moreover, we have measured the colors of several ICL features which extend beyond M87's outermost reaches and find that they have similar colors to the M87's halo itself, B-V ~ 0.8. The common colors of these features suggests that the extended outer envelopes of cD galaxies, such as M87, may be formed from similar streams, created by tidal interactions within the cluster, that have since dissolved into a smooth background in the cluster potential.Comment: 14 pages. Published in ApJ, September 201

The Connection Between Diffuse Light and Intracluster Planetary Nebulae in the Virgo Cluster

We compare the distribution of diffuse intracluster light detected in the Virgo Cluster via broadband imaging with that inferred from searches for intracluster planetary nebulae (IPNe). We find a rough correspondence on large scales (~ 100 kpc) between the two, but with very large scatter (~ 1.3 mag/arcsec^2). On smaller scales (1 -- 10 kpc), the presence or absence of correlation is clearly dependent on the underlying surface brightness. On these scales, we find a correlation in regions of higher surface brightness (mu_V < ~27) which are dominated by the halos of large galaxies such as M87, M86, and M84. In those cases, we are likely tracing PNe associated with galaxies rather than true IPNe. In true intracluster fields, at lower surface brightness, the correlation between luminosity and IPN candidates is much weaker. While a correlation between broadband light and IPNe is expected based on stellar populations, a variety of statistical, physical, and methodological effects can act to wash out this correlation and explain the lack of a strong correlation at lower surface brightness found here. [abridged