The Hubble Sequence in Groups: The Birth of the Early-Type Galaxies

The physical mechanisms and timescales that determine the morphological signatures and the quenching of star formation of typical (~L*) elliptical galaxies are not well understood. To address this issue, we have simulated the formation of a group of galaxies with sufficient resolution to track the evolution of gas and stars inside about a dozen galaxy group members over cosmic history. Galaxy groups, which harbor many elliptical galaxies in the universe, are a particularly promising environment to investigate morphological transformation and star formation quenching, due to their high galaxy density, their relatively low velocity dispersion, and the presence of a hot intragroup medium. Our simulation reproduces galaxies with different Hubble morphologies and, consequently, enables us to study when and where the morphological transformation of galaxies takes place. The simulation does not include feedback from active galactic nuclei showing that it is not an essential ingredient for producing quiescent, red elliptical galaxies in galaxy groups. Ellipticals form, as suspected, through galaxy mergers. In contrast with what has often been speculated, however, these mergers occur at z>1, before the merging progenitors enter the virial radius of the group and before the group is fully assembled. The simulation also shows that quenching of star formation in the still star-forming elliptical galaxies lags behind their morphological transformation, but, once started, is taking less than a billion years to complete. As long envisaged the star formation quenching happens as the galaxies approach and enter the finally assembled group, due to quenching of gas accretion and (to a lesser degree) stripping. A similar sort is followed by unmerged, disk galaxies, which, as they join the group, are turned into the red-and-dead disks that abound in these environments.Comment: 12 pages, 12 Figures, 1 Table, accepted for publication in AP

Old and young bulges in late-type disk galaxies

ABRIDGED: We use HSTACS and NICMOS imaging to study the structure and colors of a sample of nine late-type spirals. We find: (1) A correlation between bulge and disks scale-lengths, and a correlation between the colors of the bulges and those of the inner disks. Our data show a trend for bulges to be more metal-enriched than their surrounding disks, but otherwise no simple age-metallicity connection between these systems; (2) A large range in bulge stellar population properties, and, in particular, in stellar ages. Specifically, in about a half of the late-type bulges in our sample the bulk of the stellar mass was produced recently. Thus, in a substantial fraction of the z=0 disk-dominated bulged galaxies, bulge formation occurs after the formation/accretion of the disk; (3) In about a half of the late-type bulges in our sample, however, the bulk of the stellar mass was produced at early epochs; (4) Even these "old" late-type bulges host a significant fraction of stellar mass in a young(er) c component; (5) A correlation for bulges between stellar age and stellar mass, in the sense that more massive late-type bulges are older than less massive late-type bulges. Since the overall galaxy luminosity (mass) also correlates with the bulge luminosity (mass), it appears that the galaxy mass regulates not only what fraction of itself ends up in the bulge component, but also "when" bulge formation takes place. We show that dynamical friction of massive clumps in gas-rich disks is a plausible disk-driven mode for the formation of "old" late-type bulges. If disk evolutionary processes are responsible for the formation of the entire family of late-type bulges, CDM simulations need to produce a similar number of initially bulgeless disks in addition to the disk galaxies that are observed to be bulgeless at z=0.Comment: ApJ in press; paper with high resolution figures available at http://www.exp-astro.phys.ethz.ch/carollo/carollo1_2006.pdf; B, I, and H surface brightness profiles published in electronic tabular for

CRITICAL PERSPECTIVES ON SUSTAINABILITY IN BUSINESS CONTEXTS: PARADOXES, RHETORICS AND IDENTITIES

It has been argued that business organizations can play a relevant role in addressing contemporary ecological, social and economical challenges and contributing to global sustainable development. However, many authors affirm that current attempts to implement sustainability in organizations are often biased toward business and financial goals. In the introductory part of the dissertation I thus discuss the possible tenets of a critical approach to investigate sustainability in business organizations, which consists basically in a rejection of common assumptions associated with sustainability and CSR, such as the \u2018win-win\u2019 and the \u2018business case\u2019 arguments, in favor of an exploration of the tensions arising from their implementation. I operationalized these principles in three empiric contributions that constitute the core of this dissertation. Chapter I is a multiple-case study of companies strongly committed to environmental sustainability. As a consequence, they try to orient most of their processes, levels and everyday operations towards environmental goals. The HRM system of these companies plays a major role in this regard and we found that many different green HRM practices are devoted to sustain a greater environmental sustainability in their operations. At the same time however, because of the multiple goals that characterize both corporate sustainability and HRM systems, a series of tensions emerged that affect the green HRM systems of these organizations. Following the guidance of paradox theory, these tensions have been conceptualized as eight paradoxes. The essential finding of this study is that paradoxes characterize all the companies studied and were pervasive in their green HRM systems. Besides the specific contribution to the HRM literature, this study supports the idea that sustainability is a paradoxical accomplishment in organizations, that conveys tensions and contradictions at many different levels. In their everyday work managers need thus to take into account tensions, trying to deal with them instead of uncritically downplaying conflicts in favor of a positive, win-win conception of corporate sustainability. While conducting this research project it also emerged the key role of the CSR manager as champion of sustainability in organizations. In Chapter II therefore, I investigated the emergent managerial figure of the CSR manager. I indeed conducted a study of the occupational group of CSR managers in Italy focused on how the members of this occupation conceive their role in relation to the change that sustainability is supposed to bring inside organizations. As theoretical lens I applied the concept of occupational rhetorics, which correspond to idealized images the members of an occupation use to represent their work in a favorable manner in front of themselves and their colleagues. On the basis of a multi-method research process which included in-depth interviews, observations at public events and meetings and focus group interviews, I identified five broad rhetoric repertoires (the motor of change, the business oriented, the idealist, the fatalist and the bookkeeper of CSR) that highlight the diversity and ambiguity that surround the work of these practitioners in organizations. Overall however, the large prevalence of business argumentations in their talk due to the exigency to get legitimacy for their role, lead to the conclusion that these managers are more likely to foster continuity instead of change in current business practices. Whereas Chapter II focuses at the group level and tries to account for the shared representations of the role within the occupational group of CSR managers, Chapter III further zooms-in at the individual level and investigates the identity work operated by the same managers. The topic of identity was already incorporated in the original research project, including in the interview track questions aimed at encouraging identity talk in the interviewees. Accordingly, a part of the empiric documentation of the previous study was selected and analyzed in light of the literature on identity work and paradox theory. The identity work performed by CSR managers has been conceptualized in this chapter in three tensions: the \u2018goal tension\u2019 (between a prevalent business-orientation or a values-orientation), the \u2018space tension\u2019 (between a conception of the self as an \u2018organizational insider\u2019 versus an \u2018outsider\u2019) and the time tension (between a self \u2018focused on the short-term\u2019 versus \u2018on the long-term\u2019). It was found that CSR managers react in a varied way to these tensions, in some cases embracing one pole of the tensions, in some others expressing a paradoxical identity work. In particular, the metaphors our interviewees used to talk about themselves were found to be powerful expressions of this varied identity positioning. The dissertation moves from the assumption that CSR and sustainability represent complex and contradictory accomplishments in organizations. It thus adopts theoretical frameworks that allow to track the contradictory nature of sustainability in business contexts. The first contribution of this dissertation is the conceptualization of a series of tensions and contradictions that characterize corporate sustainability at various levels. In this sense, the dissertation represents a theory building effort that moves from difficulties and conflicts experienced in concrete organizational settings, to develop theoretical insights in a relatively \u2018young\u2019 field of investigation such as corporate sustainability. The dissertation also investigates possible ways through which managerial actors react and cope with tensions. On this, the interpretative guidance provided by paradox theory in Chapter I and III results particularly useful, because it distinguishes between different types of coping strategies that are more or less suitable to deal with paradoxical tensions in organizations. In Chapter II it is instead discussed how CSR managers recur to multiple meanings to legitimize their own role, strategically leveraging the ambiguity that surrounds sustainability in business contexts. In the case of CSR managers, it was found that this ambiguity results mainly in an apology of the status quo and in a conception of CSR and sustainability consistent with a vision of \u2018business as usual\u2019. In sum, the dissertation adds to an existing body of literature that highlights the limits of current approaches to CSR and sustainability in organizations, which appear too much instrumental, rationalistic and business-oriented. It shows indeed that many tensions characterize specific aspects of sustainability in business contexts, namely green HRM policies and practices, CSR managers\u2019 occupational rhetorics and their identity work. As a consequence, in the dissertation it is argued for the emergence of more balanced, alternative and challenging views of sustainability, which should be embraced also at the managerial level in order to be effectively implemented in organizations. In the conclusions, a reflexive account of the research path accomplished is given

The GSC-II-based survey of ancient cool white dwarfs I. The sample of spectroscopically confirmed WDs

The GSC-II white dwarf survey was designed to identify faint and high proper motion objects, which we used to define a new and independent sample of cool white dwarfs. With this survey we aim to derive new constraints on the halo white dwarf space density. Also, these data can provide information on the age of thick disk and halo through the analysis of the luminosity function. On the basis of astrometric and photometric parameters, we selected candidates with mu > 0.28 as/yr and R_F > 16 in an area of 1150 square degrees. Then, we separated white dwarfs from late type dwarfs and subdwarfs by means of the reduced proper motion diagram. Finally, spectroscopic follow-up observations were carried out to confirm the white dwarf nature of the selected candidates. We found 41 white dwarfs of which 24 are new discoveries. Here we present the full sample and for each object provide positions, absolute proper motions, photometry, and spectroscopy.Comment: 14 pages, 7 figures, submitted to A&