Widespread presence of shallow cusps in the surface-brightness profile of globular clusters

Surface brightness profiles of globular clusters with shallow central cusps (Sigma ~ R^v with -0.3<~ v <~ -0.05) have been associated by several recent studies with the presence of a central intermediate mass black hole (IMBH). Such shallow slopes are observed in several globular clusters thanks to the high angular resolution of Hubble Space Telescope imaging. In this Letter we evaluate whether shallow cusps are a unique signature of a central IMBH by analyzing a sample of direct N-body simulations of star clusters with and without a central IMBH. We ``observe'' the simulations as if they were HST images. Shallow cusps are common in our simulation sample: star clusters without an IMBH have v >~ -0.3 in the pre-core-collapse and core-collapse phases. Post-core-collapse clusters without an IMBH transition to steeper cusps, -0.7<~ v <~ -0.4, only if the primordial binary fraction is very small, f_{bin}< 3 per cent, and if there are few stellar-mass black holes remaining. Otherwise v values overlap the range usually ascribed to the presence of an IMBH throughout the entire duration of the simulations. In addition, measuring v is intrinsically prone to significant uncertainty, therefore typical measurement errors may lead to v > -0.3 even when <~ -0.4. Overall our analysis shows that a shallow cusp is not an unequivocal signature of a central IMBH and casts serious doubts on the usefulness of measuring v in the context of the hunt for IMBHs in globular clusters.Comment: 14 pages, 3 figures, Accepted for publication in The Astrophysical Journal, Letter

Testing Photometric Diagnostics for the Dynamical State and Possible IMBH presence in Globular Clusters

Surface photometry is a necessary tool to establish the dynamical state of stars clusters. We produce realistic HST-like images from N-body models of star clusters with and without central intermediate-mass black holes (IMBHs) in order to measure their surface brightness profiles. The models contain ~600,000 individual stars, black holes of various masses between 0% to 2% of the total mass, and are evolved for a Hubble time. We measure surface brightness and star count profiles for every constructed image in order to test the effect of intermediate mass black holes on the central logarithmic slope, the core radius, and the half-light radius. We use these quantities to test diagnostic tools for the presence of central black holes using photometry. We find that the the only models that show central shallow cusps with logarithmic slopes between -0.1 and -0.4 are those containing central black holes. Thus, the central logarithmic slope seems to be a good way to choose clusters suspect of containing intermediate-mass black holes. Clusters with steep central cusps can definitely be ruled out to host an IMBH. The measured r_c/r_h ratio has similar values for clusters that have not undergone core-collapse, and those containing a central black hole. We notice that observed Galactic globular clusters have a larger span of values for central slope and r_c/r_h than our modeled clusters, and suggest possible reasons that could account for this and contribute to improve future models.Comment: Accepted for publication in Ap

A Review of the HotSOS implementation at the Mandalay Bay Resort and Casino

The purpose of this professional paper is to develop a case that analyzes the implementation of a guest service response system at a full service hotel resort. The term implementation will refer to the following: the start to completion process and steps utilized to install a new method into hotel operations. The definition of system, for the purposes of this report is a technological solution that utilizes limited manual processes and relies upon computers, mobile devices and computer programming. For the purposes of this report the term full service hotel resort will refer to a casino resort and hotel that offers its guest the full array of guest amenities

Chaotic dynamics of the planet in HD 196885 AB

Depending on the planetary orbit around the host star(s), a planet could orbit either one or both stars in a binary system as S-type or P-type, respectively. We have analysed the dynamics of the S-type planetary system in HD 196885 AB with an emphasis on a planet with a higher orbital inclination relative to the binary plane. The mean exponential growth factor of nearby orbits (MEGNO) maps are used as an indicator to determine regions of periodicity and chaos for the various choices of the planet's semimajor axis, eccentricity and inclination with respect to the previously determined observational uncertainties. We have quantitatively mapped out the chaotic and quasi-periodic regions of the system's phase space which indicate a likely regime of the planet's inclination. In addition, we inspect the resonant angle to determine whether alternation between libration and circulation occurs as a consequence of Kozai oscillations, a probable mechanism that can drive the planetary orbit to a very large inclination. Also, we demonstrate the possible higher mass limit of the planet and improve upon the current dynamical model based on our analysis.Comment: 10 pages, 9 figures (Accepted for publication at MNRAS

From class to club : an exploration of high school civic-minded student organizations from 1996-2011 in Corpus Christi, Texas

textOur educational system has long claimed that preparing students to be active citizens is one of its main goals. With high-stakes testing pressures, schools with high minority enrollment have been found to cut back social studies programs and/or implement a drill and practice fragmented teaching style. (Center on Education Policy, 2007; McNeil and Valenzuela, 2000). This research project seeks to understand how civic engagement opportunities were provided for, the impact of these opportunities on students and community members in Corpus Christi, Texas, during the last 15 years, and the ways in which these opportunities may serve to maximize civic engagement for today’s Latino/a student. Using oral histories and archival data as a means to uncover the history of civic-minded organizations in Corpus Christi, Texas, on high school youth and their community, this research project will investigate the founding of the organizations, the people involved in them, and the impact of these organizations as it is perceived by alumni and those with direct experience of the organizations. While a study of this type may not be highly generalizable, it will provide new insights into promising civic education and engagement for previously marginalized groups of students. The findings of this research should add to the educational and social science literature by providing a nuanced understanding of how civic engagement opportunities may be tailored to fit into the learning environment of the high school civics classroom and beyond.Curriculum and Instructio

El edén subvertido. De Jerez a Plateros

1 archivo PDF (10 páginas). tyvlxlviEn este ensayo se plantea una revaloración de la obra cronística lopezVelardeana, poniendo de relieve el impacto cultural y existencial que implicó para el poeta su migración de la provincia zacatecana a la capital de la República durante los años turbulentos de la Revolución Mexicana. Se pone en perspectiva la transición espiritual, ideológica y estética que es perceptible en varias de las crónicas que el vate zacatecano publicó en periódicos y revistas de la Ciudad de México entre 1912 y 1917, atendiendo a las obsesiones presentes en su lírica, como el amor al ideal femenino y al terruño. Se propone una mirada sobre su poesía como rito vital sagrado y sobre su crónica como apropiación estética individualizada del entorno urbano, previamente desconocido. ABSTRACT: This essay proposes a new valuation of Ramón López Velarde’s chronicle work, emphasizing the cultural and existential impact that migration from his hinterland hometown to the capital city of the Mexican Republic provoked on this poet along the turbulent years of the Revolution. It is shown in perspective the spiritual, ideological and aesthetic transition that can be observed in many of the chronicles the bard of Mexican province published in journals and magazines of Mexico City between 1912 and 1917, considering the obsessions that are noticeable in his lyric work, such as love for feminine ideal and for homeland. This article poses a sort of view on his poetic works as sacred and vital rituals, and on his chronicles as his individual aesthetic appropriation of the urban surrounding, previously unknown. PALABRAS CLAVE: López Velarde, cronista, autor, Plateros. KEY WORDS: López Velarde, chronicle, author, Plateros