Studying the Kinematics of Faint Stellar Populations with the Planetary Nebula Spectrograph

Galaxies are faint enough when one observes just their light distributions, but in studying their full dynamical structure the stars are spread over the six dimensions of phase space rather than just the three spatial dimensions, making their densities very low indeed. This low signal is unfortunate, as stellar dynamics hold important clues to these systems' life histories, and the issue is compounded by the fact that the most interesting information comes from the faintest outer parts of galaxies, where dynamical timescales (and hence memories of past history) are longest. To extract this information, we have constructed a special-purpose instrument, the Planetary Nebula Spectrograph, which observes planetary nebulae as kinematic tracers of the stellar population, and allows one to study the stellar dynamics of galaxies down to extremely low surface brightnesses. Here, we present results from this instrument that illustrate how it can uncover the nature of low surface-brightness features such as thick disks by studying their kinematics, and trace faint kinematic populations that are photometrically undetectable.Comment: 4 pages, 2 figures. To be published in "Hunting for the Dark: The Hidden Side of Galaxy Formation", eds. V.P. Debattista & C.C. Popescu, AIP Conf. Se

Mass-to-light ratios of ellipticals in LCDM

We use the mass-to-light gradients in early-type galaxies to infer the global dark matter fraction, f_d=M_d/M_*, for these systems. We discuss implications about the total star formation efficiency in dark-matter halos and show that the trend of $f_{\rm d}$ with mass produces virial mass-to-light ratios which are consistent with semi-analitical models. Preliminary kurtosis analysis of the quasi-constant M/L galaxies in Romanowsky et al. seems at odd with Dekel et al. simulations.Comment: 5 pages, 4 figures. To appear in Proceedings of XXIst IAP Colloquium, "Mass Profiles & Shapes of Cosmological Structures" (Paris, 4-9 July 2005), eds G. A. Mamon, F. Combes, C. Deffayet, B. Fort (Paris: EDP Sciences). Figure enlarged with respect the proceeding format, minor changes. Collaboration website at http://www.astro.rug.nl/~pns/pns_team.htm

Recent ν\nus from IceCube

IceCube is a 1 km$^3$ neutrino detector now being built at the South Pole. Its 4800 optical modules will detect Cherenkov radiation from charged particles produced in neutrino interactions. IceCube will search for neutrinos of astrophysical origin, with energies from 100 GeV up to $10^{19}$ eV. It will be able to separate $\nu_e$, $\nu_\mu$ and $\nu_\tau$. In addition to detecting astrophysical neutrinos, IceCube will also search for neutrinos from WIMP annihilation in the Sun and the Earth, look for low-energy (10 MeV) neutrinos from supernovae, and search for a host of exotic signatures. With the associated IceTop surface air shower array, it will study cosmic-ray air showers. IceCube construction is now 50% complete. After presenting preliminary results from the partial detector, I will discuss IceCube's future plans.Comment: Invited talk presented at Neutrino 2008; 7 page

Convergence science in the Anthropocene: Navigating the known and unknown

Rapidly changing ecological and social systems currently pose significant societal challenges. Navigating the complexity of social-ecological change requires ap- proaches able to cope with, and potentially solve, both foreseen and unforeseen societal challenges. The emergent field of convergence addresses the intricacies of such challenges, and is thus relevant to a broad range of interdisciplinary issues. This paper suggests a way to conceptualize convergence research. It discusses how it relates to two major societal challenges (adaptation, transformation), and to the generation of policy-relevant science. It also points out limitations to the further development of convergence research

Resilience and well-being among children of migrant parents in South-East Asia

There has been little systematic empirical research on the well-being of children in transnational households in South-East Asia—a major sending region for contract migrants. This study uses survey data collected in 2008 from children aged 9, 10 and 11 and their caregivers in Indonesia, the Philippines, and Vietnam (N=1,498). Results indicate that while children of migrant parents, especially migrant mothers, are less likely to be happy compared to children in non-migrant households, greater resilience in child well-being is associated with longer durations of maternal absence. There is no evidence for a direct parental migration effect on school enjoyment and performance. The analyses highlight the sensitivity of results to the dimension of child well-being measured and who makes the assessment.Publisher PDFPeer reviewe

The relation between stellar magnetic field geometry and chromospheric activity cycles - I. The highly variable field of ɛ Eridani at activity minimum

The young and magnetically active K dwarf Epsilon Eridani exhibits a chromospheric activity cycle of about 3 years. Previous reconstructions of its large-scale magnetic field show strong variations at yearly epochs. To understand how Epsilon Eridani's large-scale magnetic field geometry evolves over its activity cycle we focus on high cadence observations spanning 5 months at its activity minimum. Over this timespan we reconstruct 3 maps of Epsilon Eridani's large-scale magnetic field using the tomographic technique of Zeeman Doppler Imaging. The results show that at the minimum of its cycle, Epsilon Eridani's large-scale field is more complex than the simple dipolar structure of the Sun and 61 Cyg A at minimum. Additionally we observe a surprisingly rapid regeneration of a strong axisymmetric toroidal field as Epsilon Eridani emerges from its S-index activity minimum. Our results show that all stars do not exhibit the same field geometry as the Sun and this will be an important constraint for the dynamo models of active solar-type stars

In-medium vector mesons and low mass lepton pairs from heavy ion collisions

The rho and omega meson self-energy at finite temperature and baryon density have been analysed for an exhaustive set of mesonic and baryonic loops in the real time formulation of thermal field theory. The large enhancement of spectral strength below the nominal rho mass is seen to cause a substantial enhancement in dilepton pair yield in this mass region. The integrated yield after space-time evolution using relativistic hydrodynamics with quark gluon plasma in the initial state leads to a very good agreement with the experimental data from In-In collisions obtained by the NA60 collaboration.Comment: Invited Talk at the DAE-BRNS Workshop on Hadron Physics, Bhabha Atomic Research Centre, Mumbai, India, October 31-November 4, 201