Morphological transformation of dwarf galaxies in the Local Group

In the Local Group there are three main types of dwarf galaxies: Dwarf Irregulars, Dwarf Spheroidals, and Dwarf Ellipticals. Intermediate/transitional types are present as well. This contribution reviews the idea that the present day variety of dwarf galaxy morphologies in the Local Group might reveal the existence of a transformation chain of events, of which any particular dwarf galaxy represents a manifestation of a particular stage. In other words, all dwarf galaxies that now are part of the Local Group would have formed identically in the early universe, but then evolved differently because of morphological transformations induced by dynamical processes like galaxy harassment, ram pressure stripping, photo-evaporation, and so forth. We start describing the population of dwarf galaxies and their spatial distribution in the LG. Then, we describe those phenomena that can alter the morphology of a dwarf galaxies, essentially by removing, partially or completely, their gas content. Lastly, we discuss morphological signatures in the Local Group Dwarf Galaxies that can be attributed to different dynamical phenomena. While it is difficult to identify a unique and continuous transformation sequence, we have now a reasonable understanding of the basic evolutionary paths that lead to the various dwarf galaxy type

Gaia 1 cannot be a Thick Disk Galactic cluster

In this note I show how the recently suggested membership of the open cluster Gaia 1 to the Galactic thick disk is based on incorrect assumptions about the structure of the disk itself, and neglect well-known observational evidences on the disk warp and flare.Comment: 2 pages, 1 figure, in press as a Research Note of the American Astronomical Societ

The Milky Way disk

This review summarises the invited presentation I gave on the Milky Way disc. The idea underneath was to touch those topics that can be considered hot nowadays in the Galactic disk research: the reality of the thick disk, the spiral structure of the Milky Way, and the properties of the outer Galactic disk. A lot of work has been done in recent years on these topics, but a coherent and clear picture is still missing. Detailed studies with high quality spectroscopic data seem to support a dual Galactic disk, with a clear separation into a thin and a thick component. Much confusion and very discrepant ideas still exist concerning the spiral structure of the Milky Way. Our location in the disk makes it impossible to observe it, and we can only infer it. This process of inference is still far from being mature, and depends a lot on the selected tracers, the adopted models and their limitations, which in many cases are neither properly accounted for, nor pondered enough. Finally, there are very different opinions on the size (scale length, truncation radius) of the Galactic disk, and on the interpretation of the observed outer disk stellar populations in terms either of external entities (Monoceros, Triangulus-Andromeda, Canis Major), or as manifestations of genuine disk properties (e.g., warp and flare).Comment: 7 pages, 9 figures. Full text in English. To be published in the 57 Bulletin of the Argentinian Association of Astronomy (BAAA 57

Properties and origin of the old, metal rich, star cluster, NGC 6791

In this contribution I summarize the unique properties of the old, metal rich, star cluster NGC 6791, with particular emphasis on its population of extreme blue horizontal branch stars. I then conclude providing my personal view on the origin of this fascinating star cluster.Comment: 7 pages, 4 eps figures, paper presented at the 10th Pacific Rim Conference on Stellar Astrophysics, Seoul, May 27-31, 2013, ASP Conference Series, in pres

The Milky Way thin disk structure as revealed by stars and young open clusters

In this contribution I shall focus on the structure of the Galactic thin disk. The evolution of the thin disk and its chemical properties have been discussed in detail by T. Bensby's contribution in conjunction with the properties of the Galactic thick disk, and by L.Olivia in conjunction with the properties of the Galactic bulge. I will review and discuss the status of our understanding of three major topics, which have been the subject of intense research nowadays, after long years of silence: (1) the spiral structure of the Milky Way, (2) the size of the Galactic disk, and (3) the nature of the Local arm (Orion spur), where the Sun is immersed. The provisional conclusions of this discussion are that : (1) we still have quite a poor knowledge of the Milky Way spiral structure, and the main dis-agreements among various tracers are still to be settled; (2) the Galactic disk does clearly \textit{not} have an obvious luminous cut-off at about 14 kpc from the Galactic center, and next generation Galactic models need to be updated in this respect, and (3) the Local arm is most probably an inter-arm structure, similar to what we see in several external spirals, like M~74. Finally, the impact of GAIA and LAMOST in this field will be briefly discussed as well.Comment: 12 pages, 8 eps figure, invited review, to appear in Proceedings of the IAU Symposium No. 298, "Setting the scene for Gaia and LAMOST", eds. S. Feltzing, G. Zhao, N. A. Walton, and P. A. Whiteloc

The intermediate-age open cluster NGC 2112

We report on $BVI$ CCD photometry of a field centered on the region of the intermediate-age open cluster NGC 2112 down to V=21. Due to the smaller field coverage, we are able to limit the effect of field star contamination which hampered in the past precise determinations of the cluster age and distance. This way, we provide updated estimates of NGC 2112 fundamental parameters. Having extended the photometry to the $I$ pass-band, we are able to construct a colour-colour diagram, from which we infer a reddening $E_{B-V}= 0.63\pm0.14$ mag. The comparison of the Colour-Magnitude Diagram (CMD) with theoretical isochrones leads to a distance of $850 \pm 100$ pc, and an age of $2.0 \pm 0.3$ Gyr. While the distance is in agreement with previous determinations, the age turns out to be much better constrained and significantly lower than previous estimates.Comment: 7 pages, 7 eps figures, in press in MNRA

Incentives and Institutions. A Bottom-up Approach to Climate Policy

This paper comments and assesses “Fragmented Carbon Markets and Reluctant Nations: Implications for the Design of Effective Architectures”, a paper that David Victor presented at the international workshop on "Architectures for Agreement: Addressing Global Climate Change in the Post-Kyoto World", organized by Joe Aldy and Rob Stavins at the J.F. Kennedy School of Government in May 2006. By analyzing Victor’s proposals for an effective climate agreement post 2012, this paper emphasizes the contribution that game-theoretical analyses have provided to the design of climate agreements. It therefore emphasizes how incentives and institutions play a crucial role in affecting the final outcome of negotiations on climate change control, and how incentives and institutions can be modified to achieve a better control of climate change. This paper also discusses a wider policy approach that can enhance the effectiveness of measures designed to address the climate change problem.Agreements, Climate, Incentives, Negotiations, Policy

The Road to Copenhagen: What Agreement Can Actually Be Effective and Stable? by Carlo Carraro

Klimaveränderung; Umweltabkommen; Internationale Zusammenarbeit; Welt

Old open clusters in the outer Galactic disk

The outer parts of the Milky Way disk are believed to be one of the main arenas where the accretion of external material in the form of dwarf galaxies and subsequent formation of streams is taking place. The Monoceros stream and the Canis Major and Argo over-densities are notorious examples. VLT high resolution spectra have been acquired for five distant open clusters. We derive accurate radial velocities to distinguish field interlopers and cluster members. For the latter we perform a detailed abundance analysis and derive the iron abundance [Fe/H] and the abundance ratios of several $\alpha$ elements. Our analysis confirms previous indications that the radial abundance gradient in the outer Galactic disk does not follow the expectations extrapolated from the solar vicinity, but exhibits a shallower slope. By combining the metallicity of the five program clusters with eight more clusters for which high resolution spectroscopy is available, we find that the mean metallicity in the outer disk between 12 and 21 kpc from the Galactic center is [Fe/H] $\approx -0.35$, with only marginal indications for a radial variation. In addition, all the program clusters exhibit solar scaled or slightly enhanced $\alpha$ elements, similar to open clusters in the solar vicinity and thin disk stars. We investigate whether this outer disk cluster sample might belong to an extra-galactic population, like the Monoceros ring. However, close scrutiny of their properties - location, kinematics and chemistry - does not convincingly favor this hypothesis. On the contrary, they appear more likely genuine Galactic disk clusters. We finally stress the importance to obtain proper motion measurements for these clusters to constrain their orbits.Comment: 19 pages, 9 eps figure, in press in A&A, abstract rephrased to fit i