The Propagation of Magneto-Centrifugally Launched Jets: I

We present simulations of the propagation of magnetized jets. This work differs from previous studies in that the cross-sectional distributions of the jets's state variables are derived from analytical models for magneto-centrifugal launching. The source is a magnetized rotator whose properties are specfied as boundary conditions. The jets in these simulations are considerably more complex than the ``top-hat''constant density etc. profiles used in previous work. We find that density and magnetic field stratification (with radius) in the jet leads to new behavior including the separation of an inner jet core from a low density collar. We find this {\it jet within a jet} structure, along with the magnetic stresses, leads to propagation behaviors not observed in previous simulation studies. Our methodology allows us to compare MHD jets from different types of sources whose properties could ultimately be derived from the behavior of the propagating jets.Comment: 42 pages, accepted by the Ap

Connecting the pieces: using ORCIDs to improve research impact and repositories

Quantitative data are crucial in the assessment of research impact in the academic world. However, as a young university created in 2009, King Abdullah University of Science and Technology (KAUST) needs to aggregate bibliometrics from researchers coming from diverse origins, not necessarily with the proper affiliations. In this context, the University has launched an institutional repository in September 2012 with the objectives of creating a home for the intellectual outputs of KAUST researchers. Later, the university adopted the first mandated institutional open access policy in the Arab region, effective June 31, 2014. Several projects were then initiated in order to accurately identify the research being done by KAUST authors and bring it into the repository in accordance with the open access policy. Integration with ORCID has been a key element in this process and the best way to ensure data quality for researcher’s scientific contributions. It included the systematic inclusion and creation, if necessary, of ORCID identifiers in the existing repository system, an institutional membership in ORCID, and the creation of dedicated integration tools. In addition and in cooperation with the Office of Research Evaluation, the Library worked at implementing a Current Research Information System (CRIS) as a standardized common resource to monitor KAUST research outputs. We will present our findings about the CRIS implementation, the ORCID API, the repository statistics as well as our approach in conducting the assessment of research impact in terms of usage by the global research community

Connecting the pieces: using ORCIDs to improve research impact and repositories

Quantitative data are crucial in the assessment of research impact in the academic world. However, as a young university created in 2009, King Abdullah University of Science and Technology (KAUST) needs to aggregate bibliometrics from researchers coming from diverse origins, not necessarily with the proper affiliations. In this context, the University has launched an institutional repository in September 2012 with the objectives of creating a home for the intellectual outputs of KAUST researchers. Later, the university adopted the first mandated institutional open access policy in the Arab region, effective June 31, 2014. Several projects were then initiated in order to accurately identify the research being done by KAUST authors and bring it into the repository in accordance with the open access policy. Integration with ORCID has been a key element in this process and the best way to ensure data quality for researcher’s scientific contributions. It included the systematic inclusion and creation, if necessary, of ORCID identifiers in the existing repository system, an institutional membership in ORCID, and the creation of dedicated integration tools. In addition and in cooperation with the Office of Research Evaluation, the Library worked at implementing a Current Research Information System (CRIS) as a standardized common resource to monitor KAUST research outputs. We will present our findings about the CRIS implementation, the ORCID API, the repository statistics as well as our approach in conducting the assessment of research impact in terms of usage by the global research community

Transit flow models for low and high mass protostars

In this work, the gas infall and the formation of outflows around low and high mass protostars are investigated. A radial self-similar approach to model the transit of the molecular gas around the central object is employed. We include gravitational and radiative fields to produce heated pressure-driven outflows with magneto-centrifugal acceleration and collimation. Outflow solutions with negligible or vanishing magnetic field are reported. They indicate that thermodynamics is a sufficient engine to generate an outflow. The magnetized solutions show dynamically significant differences in the axial region, precisely where the radial velocity and collimation are the largest. They compare quantitatively well with observations. The influence of the opacity on the transit solutions is also studied. It is found that, when dust is not the dominant coolant, such as in the primordial universe, mass infall rates have substantial larger values in the equatorial region. This suggests that star forming in a dust-free environment should be able to accrete much more mass and become more massive than present day protostars.It is also suggested that molecular outflows may be dominated by the global transit of material around the protostar during the very early stages of star formation, especially in the case of massive or dust-free star formation.Comment: 19 pages, 15 figures, accepted by Ap

A Global Jet/Circulation Model for Young Stars

Powerful, highly collimated jets, surrounded by bipolar molecular outflows, are commonly observed near Young Stellar Objects (YSOs). In the usual theoretical picture of star formation, a jet is ejected from a magnetized accretion disk, with a molecular outflow being driven either by the jet or by a wider wind coming from the disk. Here, we propose an alternative global model for the flows surrounding YSOs. In addition to a central accretion-ejection engine driving the jet, the molecular outflow is powered by the infalling matter and follows a circulation pattern around the central object without necessarily being entrained by a jet. It is shown that the model produces a heated pressure-driven outflow with magneto-centrifugal acceleration and collimation. We report solutions for the three different parts of this self-similar model, i.e. the jet, the infalling envelope and the circulating matter that eventually forms the molecular outflow. This new picture of the accretion/outflow phase provides a possible explanation for several observed properties of YSO outflows. The most relevant ones are the presence of high mass molecular outflows around massive protostars, and a realistic fraction (typically 0.1) of the accretion flow that goes into the jet.Comment: accepted for publication in Astronomy and Astrophysic

HST/STIS Spectroscopy of the Optical Outflow from DG Tau: Indications for Rotation in the Initial Jet Channel

We have carried out a kinematical, high angular resolution (~ 0".1) study of the jet from DG Tau within 0."5 from the source (or 110 AU along this flow). We analysed line profiles extracted from a set of seven spectra taken with STIS on board the Hubble Space Telescope, with the slits parallel to the jet axis but displaced transversely every 0".07. For the flow of moderate velocity (-70 km/s), we have found systematic differences in the radial velocities of lines emitted on alternate sides of the jet axis. The results are corrected for the effects due to uneven illumination of the slit. The relative Doppler shifts range from 5 to 20 km/s. If this is interpreted as rotation, the flow is then rotating clockwise looking from the jet towards the source and the derived toroidal velocities are in the range 6 - 15 km/s. Using recent estimates of the mass loss rate, one obtains for the considered velocity regime, an angular momentum flux of ~ 3.8x10E-5 M_sun/yr AU km/s. Our findings may constitute the first detection of rotation in the initial channel of a jet flow. The derived values appear to be consistent with the predictions of popular magneto-centrifugal jet-launching models, although we cannot exclude transverse outflow asymmetries other than rotation.Comment: aastex, 23 pages, 5 b/w figures, 3 color figures, ApJ in pres