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Canovas H.,University of Valparaiso | Caceres C.,University of Valparaiso | Schreiber M.R.,University of Valparaiso | Hardy A.,University of Valparaiso | And 6 more authors.
Monthly Notices of the Royal Astronomical Society: Letters | Year: 2016

Models of planet formation and disc evolution predict a variety of observables in the dust structure of protoplanetary discs. Here, we present Atacama Large Millimeter/submillimeter Array (ALMA) Band-6 and Band-7 observations of the transition disc Sz 91 showing that the continuum emission at 870 μm, which is dominated by emission from large dust grains, is localized in an optically thin narrow ring. We find that most of the emission (~95 per cent) is concentrated in a ring located at 110 au from the central star that is only about 44 au wide. In contrast, the 12CO (2-1) emission peaks closer to the star and is detected up to ~488 au from the star. The concentration of large grains in a ring-like structure while the gas disc extends much further in and further out is in qualitative agreement with predictions of hydrodynamical models of planet-disc interactions including radial drift and gas drag. © 2016 The Authors. Source

Rabanus D.,Atacama Large Millimeter submillimeter Array
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

Current large observatories, both in operation and projects in development or construction, face the challenge to find skilled personnel for integration and operation. Typical locations of these observatories are found to be remote, mainly due to electromagnetic pollution prevention, which in many if not all cases reduces the attractiveness of the work posts. Additional budgetary limitations restrict the recruitment radius for certain positions to the local labor market. This paper outlines these staffing constraints in more detail and elaborates on the need for training programs on various levels, which can be costly. This, in turn, drives the need for creative retention efforts. Therefore, financial modeling, contingency, risk and quality management, and the reliability, availability, and maintainability of an observatory are directly coupled to the local embedding in the labor market of the host country. © 2012 SPIE. Source

Da Cunha E.,Max Planck Institute for Astronomy | Da Cunha E.,Swinburne University of Technology | Walter F.,Max Planck Institute for Astronomy | Smail I.R.,Durham University | And 16 more authors.
Astrophysical Journal | Year: 2015

The ALESS survey has followed up on a sample of 122 sub-millimeter sources in the Extended Chandra Deep Field South at 870 μm with the Atacama Large Millimeter Array (ALMA), allowing us to pinpoint the positions of sub-millimeter galaxies (SMGs) to ∼0.3 arcsec and to find their precise counterparts at different wavelengths. This enabled the first compilation of the multi-wavelength spectral energy distributions (SEDs) of a statistically reliable survey of SMGs. In this paper, we present a new calibration of the magphys SED modeling code that is optimized to fit these ultraviolet-to-radio SEDs of star-forming galaxies using an energy balance technique to connect the emission from stellar populations, dust attenuation, and dust emission in a physically consistent way. We derive statistically and physically robust estimates of the photometric redshifts and physical parameters (such as stellar masses, dust attenuation, star formation rates (SFRs), and dust masses) for the ALESS SMGs. We find that the ALESS SMGs have median stellar mass , median SFR , median overall V-band dust attenuation mag, median dust mass , and median average dust temperature K. We find that the average intrinsic SED of the ALESS SMGs resembles that of local ultra-luminous infrared galaxies in the infrared range, but the stellar emission of our average SMG is brighter and bluer, indicating lower dust attenuation, possibly because they are more extended. We explore how the average SEDs vary with different parameters (redshift, sub-millimeter flux, dust attenuation, and total infrared luminosity), and we provide a new set of SMG templates that can be used to interpret other SMG observations. To put the ALESS SMGs into context, we compare their stellar masses and SFRs with those of less actively star-forming galaxies at the same redshifts. We find that at , about half of the SMGs lie above the star-forming main sequence (with SFRs three times larger than normal galaxies of the same stellar mass), while half are consistent with being at the high-mass end of the main sequence. At higher redshifts (), the SMGs tend to have higher SFRs and stellar masses, but the fraction of SMGs that lie significantly above the main sequence decreases to less than a third. © 2015. The American Astronomical Society. All rights reserved. Source

Glendenning B.E.,U.S. National Radio Astronomy Observatory | Ibsen J.,Atacama Large Millimeter submillimeter Array | Kosugi G.,Japan National Astronomical Observatory | Raffi G.,European Southern Observatory
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010

The ALMA Software (~ 80% completed) is in daily use at the ALMA Observatory and has been developed as an end-toend system including: proposal preparation, dynamic scheduling, instrument control, data handling and formatting, data archiving and retrieval, automatic and manual data processing, and support for observatory operations. This presentation will expand on some software management aspects, procedures for releases, integrated system testing and deployment in Chile. The need for a realistic validation environment, now achieved with a two antenna interferometer at the observatory, and the balance between incremental development and stability of the software (a challenge at the moment) will be explained. © 2010 SPIE. Source

Canovas H.,University of Valparaiso | Canovas H.,University of Chile | Menard F.,French National Center for Scientific Research | Menard F.,University of Chile | And 10 more authors.
Astronomy and Astrophysics | Year: 2013

Context. HD 142527 is a pre-transition disk with strong evidence for ongoing planet formation. Recent observations show a disrupted disk with spiral arms, a dust-depleted inner cavity and the possible presence of gas streams driving gas from the outer disk toward the central star. Aims. We aim to derive the morphology of the disk and the distribution and properties of the dust at its surface. Methods. We have obtained polarized differential images of HD 142527 at H and Ks bands with NaCo at the VLT. Combining these images with classical PSF-subtraction, we are able to derive the polarization degree of this disk. Results. At H band the polarization degree of the disk varies between 10% and 25%. This result cannot be reproduced by dust distributions containing highly porous material. The polarization is better matched by distributions of compact particles, with maximum sizes at least up to a few microns, in agreement with previous observations. We also observe two regions of low emission (nulls) in total and in polarized intensity. In particular, one of these nulls is at roughly the same position as the maximum of the horse-shoe shape observed in submillimeter continuum emission ALMA band-7 (345 GHz) observations. We discuss the possible link between these two features. © ESO, 2013. Source

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