Observations of a high-mass protostar in NGC 7538S

We present high angular resolution continuum observations of the high-mass protostar NGC 7538S with BIMA and CARMA at 3 and 1.4 mm, VLA observations at 1.3, 2, 3.5 and 6 cm, and archive IRAC observations from the Spitzer Space Observatory, which detect the star at 4.5, 5.8, and 8 $\mu$m. The star looks rather unremarkable in the mid-IR. The excellent positional agreement of the IRAC source with the VLA free-free emission, the OH, CH$_3$OH, H$_2$O masers, and the dust continuum confirms that this is the most luminous object in the NGC 7538S core. The continuum emission at millimeter wavelengths is dominated by dust emission from the dense cold cloud core surrounding the protostar. Including all array configurations, the emission is dominated by an elliptical source with a size of ~ 8" x 3". If we filter out the extended emission we find three compact mm-sources inside the elliptical core. The strongest one, $S_A$, coincides with the VLA/IRAC source and resolves into a double source at 1.4 mm, where we have sub-arcsecond resolution. The measured spectral index, $\alpha$, between 3 and 1.4 mm is ~ 2.3, and steeper at longer wavelengths, suggesting a low dust emissivity or that the dust is optically thick. We argue that the dust in these accretion disks is optically thick and estimate a mass of an accretion disk or infalling envelope surrounding S$_A$ to be ~ 60 solar masses.Comment: ApJ Accepted 2012, 13 pages, 9 figure

The migration flux: Understanding international immigration through internal migration

This paper introduces the idea that the network structure that emerges from a foreign-born population's internal migration process changes the conditions for international immigration. The idea is tested by using data from the period between 1998 and 2008 about virtually all internal and international migration events in Spain. The findings show that internal migration changes the intensity and the quality content of immigrant social capital transfers, with both positive and negative ramifications for subsequent network-driven international migration. The effect of internal migration was particularly influential in localities with no prior direct international immigration experience. The findings also revealed a synergistic effect between the two migration processes - high levels of internal migration lead to elevated overall international immigration levels. Almost all research focusing on network-driven migration treats the causal mechanism producing the network effect in an endogenous way. For example, it is commonly claimed that increasing international immigration is the result of an expansion of the immigrant network due to past international immigration. My findings constitute explicit evidence that network-driven international migration is also determined by exogenous factors such as the second-order migration of past migrants in the destination.international; internal; domestic; migration; immigration; cumulative causation; chain migration; social networks

NGC7538 IRS1 - an ionized jet powered by accretion

Analysis of high spatial resolution VLA images shows that the free-free emission from NGC7538 IRS1 is dominated by a collimated ionized wind. We have re-analyzed high angular resolution VLA archive data from 6 cm to 7 mm, and measured separately the flux density from the compact bipolar core and the extended (1.5" - 3") lobes. We find that the flux density of the core is proportional to the frequency to the power of alpha, with alpha being about 0.7. The frequency dependence of the total flux density is slightly steeper with alpha = 0.8. A massive optically thick hypercompact core with a steep density gradient can explain this frequency dependence, but it cannot explain the extremely broad recombination line velocities observed in this source. Neither can it explain why the core is bipolar rather than spherical, nor the observed decrease of 4% in the flux density in less than 10 years. An ionized wind modulated by accretion is expected to vary, because the accretion flow from the surrounding cloud will vary over time. BIMA and CARMA continuum observations at 3 mm show that the free-free emission still dominates at 3 mm. HCO+ J = 1 - 0 observations combined with FCRAO single dish data show a clear inverse P Cygni profile towards IRS1. These observations confirm that IRS1 is heavily accreting with an accretion rate of about 2 times 10(-4) solar masses per year.Comment: Accepted for Astrophysical Journal Letter

Individual choices? Bioscience, culture and society as approaches to genes, eating and health

This paper presents the background and a plan for an interdisciplinary study that aims at examining the practices of eating as an entanglement of biology, culture and society all together. Our interest is on genes not only as a biological fact but also as a scientific discovery that increasingly shapes our understanding of the interconnections between genotype, eating patterns and health. Genetics is assumed to bear a growing role in the self-understanding and eating practices of future consumers. In this paper, we first highlight the basic assumptions on the role of the social and the individual in theory of practices, food-relating taste psychogenomics, and cultural studies

Teacher change and development during training in social and emotional learning programs in Sweden

The paper presents the results from a thematic analysis of the process diaries of teachers involved in teacher training in social and emotional learning (SEL) in Sweden. Twentynine out of the 122 diaries available were analyzed until saturation was reached. The following themes and sub-themes were extracted: development (professional and personal, and classroom climate), and concomitants of development (need for collaboration and unease). The themes and sub-themes are related to theoretical aspects of specialised teacher education and to the debate in Sweden on how to proceed with SEL programs, and more generally with life skills programs. The results suggest that training generates both general teacher improvement and better implementation of SEL programs.peer-reviewe

A detailed study of the accretion disk surrounding the high-mass protostar NGC 7538S

We present deep high angular resolution observations of the high-mass protostar NGC 7538S, which is in the center of a cold dense cloud core with a radius of 0.5 pc and a mass of ~2,000 Msun. These observations show that NGC 7538S is embedded in a compact elliptical core with a mass of 85 - 115 Msun. The star is surrounded by a rotating accretion disk, which powers a very young, hot molecular outflow approximately perpendicular to the rotating accretion disk. The accretion rate is very high, ~ 1.4 - 2.8 10^-3 Msun yr^-1. Evidence for rotation of the disk surrounding the star is seen in all largely optically thin molecular tracers, H13CN J = 1-0, HN13C J = 1-0, H13CO+ J = 1-0, and DCN J = 3-2. Many molecules appear to be affected by the hot molecular outflow, including DCN and H13CO+. The emission from CH3CN, which has often been used to trace disk rotation in young high-mass stars, is dominated by the outflow, especially at higher K-levels. Our new high-angular resolution observations show that the rotationally supported part of the disk is smaller than we previously estimated. The enclosed mass of the inner, rotationally supported part of the disk (D ~ 5", i.e 14,000 AU) is ~ 14 - 24 Msun.Comment: Accepted by ApJ; 20 pages, 20 figure