RCW 49 at mid-infrared wavelengths: A glimpse from the Spitzer Space Telescope

The luminous, massive star formation region RCW 49, located in the southern Galactic plane, was imaged with the Infrared Array Camera (IRAC) on the Spitzer Space Telescope as part of the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) program. The IRAC bands contain polycyclic aromatic hydrocarbon (PAH) features at 3.3, 6.2, 7.7, and 8.6 μm, as well as the Brα line. These features are the major contributors to the diffuse emission from RCW 49 in the IRAC bands. The Spitzer IRAC images show that the dust in RCW 49 is distributed in a network of fine filaments, pillars, knots, sharply defined boundaries, bubbles, and bow shocks. The regions immediately surrounding the ionizing star cluster and W-R stars are evacuated of dust by stellar winds and radiation. The IRAC images of RCW 49 suggest that the dust in RCW 49 has been sculpted by the winds and radiation from the embedded luminous stars in the inner 5′ (inner ∼6 pc) of the nebula. At projected angular radii φ > 5′ from the central ionizing cluster, the azimuthally averaged infrared intensity falls off as ∼φ-3. Both high-resolution radio and mid-IR images suggest that the nebula is density bounded along its western boundary. The filamentary structure of the dust in RCW 49 suggests that the nebula has a small dust filling factor and, as a consequence, the entire nebula may be slightly density bounded to H-ionizing photons

Identification of main-sequence stars with mid-infrared excesses using glimpse: β pictoris analogs?

Spitzer IRAC 3.6-8 μm photometry obtained as part of the GLIMPSE survey has revealed mid-infrared excesses for 33 field stars with known spectral types in a 1.2 deg2 field centered on the southern Galactic H II region RCW 49. These stars comprise a subset of 184 stars with known spectral classification, most of which were preselected to have unusually red IR colors. We propose that the mid-IR excesses are caused by circumstellar dust disks that are either very late remnants of stellar formation or debris disks generated by planet formation. Of these 33 stars, 29 appear to be main-sequence stars on the basis of optical spectral classifications. Five of the 29 main-sequence stars are O or B stars with excesses that can be plausibly explained by thermal bremsstrahlung emission, and four are post-main-sequence stars. The lone O star is an O4 V((f)) at a spectrophotometric distance of 3233-535 +540 pc and may be the earliest member of the Westerlund 2 cluster. Of the remaining 24 main-sequence stars, 18 have spectral energy distributions that are consistent with hot dusty debris disks, a possible signature of planet formation. Modeling the excesses as blackbodies demonstrates that the blackbody components have fractional bolometric disk-to-star luminosity ratios, L IR/L*, ranging from 10-3 to 10-2 with temperatures ranging from 220 to 820 K. The inferred temperatures are more consistent with asteroid belts than with the cooler temperatures expected for Kuiper belts. Mid-IR excesses are found in all spectral types from late B to early K

The Impact of Aristotelianism on Modern Philosophy

This volume presents the papers delivered during the Fall 1999 lecture series of the School of Philosophy at the Catholic University of America. It originates from the wish to trace across the centuries the continuous presence of the five intellectual virtues set forth by Aristotle in book VI of the Nicomachean Ethics. All speakers were asked to consider their author\u2019s position as regards the concepts of art, prudence, science, wisdom, understanding, and look for reactions to Aristotle\u2019s original understanding of them. Of course, this was a very specific question, and although the speakers were encouraged to consider this issue, they were not necessitated to do so. It was rather suggested they looked into the general issue of the impact of Aristotle on the philosophers they were familiar with, namely Zabarella, Galilei, Su\ue1rez, Semery, Leibniz, Rousseau, Kant, Hegel, Nietzsche, Husserl, Heidegger, Wittgenstein, and Gadamer. For the sake of precision, the scope of the volume was limited to modern philosophy, i.e., to the period that begins with the Renaissance and ends with the twentieth century. It is true that many representative philosophers are considered in the volume, but just as many are missing. On the other side, the inclusion of Hellenistic or early and late medieval philosophy would have made a thorough reconstruction of the impact of Aristotle\u2019s intellectual virtues a sheer impossibility. Obviously, the restriction of the diachronic scope does not bring with itself a claim at completeness. Finally, it needs be recognized that it was not only and not simply Aristotle that influenced modern philosophy. The impact the contributors have written about is rather the impact of a tradition, the tradition Renaissance Aristotelianism, which was first molded by Aldo Manuzio\u2019s edition of Aristotle\u2019s Opera (Venice, 1495-98), found its standing in the monumental edition of the Giunti with Averroes\u2019 commentary (Venice, 1550-52), and reached its blossoming by means of the European diffusion of the Paduan School. It has never been obvious to deal with Aristotle, and Sir Anthony Kenny\u2019s recent essays on Aristotelianism, the volume on the questions \u201cwhose Aristotle? whose Aristotelianism?\u201d edited by R. W. Sharples, and the volume on the impact of the Paduan School on early modern philosophy edited by Gregorio Piaia prove that. Aristotle is both the most praised and the most condemned philosopher of all times. At the beginning of the twentieth century, Ernst Cassirer described the shift that took place from sixteenth to seventeenth-century philosophy as a shift from the concept of substance to the concept of relation. As long as the concept of substance and the idea that a property is predicated of an individual subject maintained scientific primacy, Aristotelianism was in great demand and was able to defeat threatening alternatives such as Ramism; but as soon as Descartes established the convenience of expressing all scientific problems in terms of function, i.e., in terms of the relation of two or more ideas or bodies in space and time, Aristotelianism began an inexorable descent. By the middle of the eighteenth century, Aristotelianism virtually disappeared from university curricula and from scientific publications all over Europe. This did not mean, however, that Aristotle was forgotten. Kant kept referring to Aristotle all of his life, and the sections dedicated to Aristotle in Hegel\u2019s Lectures on the History of Philosophy prepared the Aristotle Renaissance of the early nineteenth century, which was made possible by Immanuel Becker\u2019s edition of the Opera (Berlin, 1831-36). Finally, that Aristotle experienced a further Renaissance all over the twentieth century was due to Leo XIII\u2019s proclamation of Thomism as the official doctrine of the Catholic Church in the encyclical letter Aeterni Patris of August 4, 1879; and it was also due to the reappraisal of his philosophy that began with Werner Jaeger and ended with Gadamer. This volume is about the history of a tradition, the tradition of Renaissance and modern Aristotelianism. It does not aim at replacing any of the existing works that have been dedicated to the whole or to parts of the history of Aristotelianism. It aims, however, at tracing the impact of Aristotelianism on modern philosophy in the form of a clear line that goes through the writings of the philosophers of the Western tradition. Each paper of this volume provides an original contribution in as far as it illuminates the role played by Aristotelianism as one of the sources, if not as the dominant one, of one individual philosopher. Often, to deal with Aristotle or Aristotelianism meant to take a stance concerning an issue that was discussed in one\u2019s own age\u2014this was the case, e.g., for Kant when he looked into a new understanding of the concepts of art, prudence, science, wisdom, and understanding. However, one should not look into this volume for an exposition of the history of the five concepts that constitute Aristotle\u2019s theory of the intellectual virtues. No individual contributor has pursued this object. What they have rather tried to reconstruct, and what they have accomplished all together is a thoughtful discussion of a problem that crosses the ages and is always actual, namely the problem whether one may consider Aristotle\u2019s list of five intellectual virtues to be complete, and, if not, by means of what other virtues it might be completed

What Have We Learned about the Employment Effects of Severance Pay? Further Iterations of Lazear Et al.

Severance pay, employment protection, employment, unemployment, labor force participation, time-varying labor market institutions, J23, J64, J65,

Reassessing Resistance: Race, Gender and Sexuality in Prison

The relationship between power and resistance behind prison walls has long animated sociological discussions of imprisonment. In this article we advance a fresh understanding of resistance that recognizes the multi-faceted dimensions of prisoner agency while acknowledging the dangers in simply valorizing the strategies of the confined to subvert penal power. For us the importance of resistance is that it makes explicit the connections between everyday actions and broader inequalities. Nevertheless we identify three limitations in conventional characterizations of resistance. First it is understood as a privileged quality in the human spirit. Second, is the assumption that those who do not challenge authority accept the legitimacy of the institution. Third is the equation of resistance with rudimentary political action. Though drawing on our empirical research conducted in male and female prisons in the UK we refine the concept to overcome these limitations. In particular we indicate how social identities mediate prisoner agency and are crucially implicated in acts of contestation. Our more general ambition is to place at the centre of prison sociology the still marginalized issues of gender, race and sexuality