Origin of the wide-angle hot H2 in DG Tauri: New insight from SINFONI spectro-imaging

We wish to test the origins proposed for the extended hot H2 at 2000K around the atomic jet from the T Tauri star DGTau, in order to constrain the wide-angle wind structure and the possible presence of an MHD disk wind. We present flux calibrated IFS observations in H2 1-0 S(1) obtained with SINFONI/VLT. Thanks to spatial deconvolution by the PSF and to accurate correction for uneven slit illumination, we performed a thorough analysis and modeled the morphology, kinematics, and surface brightness. We also compared our results with studies in [FeII], [OI], and FUV-pumped H2. The limb-brightened H2 emission in the blue lobe is strikingly similar to FUV-pumped H2 imaged 6yr later, confirming that they trace the same hot gas and setting an upper limit of 12km/s on any expansion proper motion. The wide-angle H2 rims are at lower blueshifts than probed by narrow long-slit spectra. We confirm that they extend to larger angle and to lower speed the onion-like velocity structure observed in optical atomic lines. The latter is shown to be steady over more/equal than 4yr but undetected in [FeII] by SINFONI, probably due to strong iron depletion. The H2 rim thickness less/equal than 14AU rules out excitation by C-shocks, and J-shock speeds are constrained to 10km/s. We find that explaining the H2 wide-angle emission with a shocked layer requires either a recent outburst (15yr) into a pre-existing ambient outflow or an excessive wind mass flux. A slow photoevaporative wind from the dense irradiated disk surface and an MHD disk wind heated by ambipolar diffusion seem to be more promising and need to be modeled in more detail

ALMA CO J=6-5 observations of IRAS16293-2422: Shocks and entrainment

Observations of higher-excited transitions of abundant molecules such as CO are important for determining where energy in the form of shocks is fed back into the parental envelope of forming stars. The nearby prototypical and protobinary low-mass hot core, IRAS16293-2422 (I16293) is ideal for such a study. The source was targeted with ALMA for science verification purposes in band 9, which includes CO J=6-5 (E_up/k_B ~ 116 K), at an unprecedented spatial resolution (~0.2", 25 AU). I16293 itself is composed of two sources, A and B, with a projected distance of 5". CO J=6-5 emission is detected throughout the region, particularly in small, arcsecond-sized hotspots, where the outflow interacts with the envelope. The observations only recover a fraction of the emission in the line wings when compared to data from single-dish telescopes, with a higher fraction of emission recovered at higher velocities. The very high angular resolution of these new data reveal that a bow shock from source A coincides, in the plane of the sky, with the position of source B. Source B, on the other hand, does not show current outflow activity. In this region, outflow entrainment takes place over large spatial scales, >~ 100 AU, and in small discrete knots. This unique dataset shows that the combination of a high-temperature tracer (e.g., CO J=6-5) and very high angular resolution observations is crucial for interpreting the structure of the warm inner environment of low-mass protostars.Comment: Accepted for publication in A&A Letter

Alarm fatigue in the ward

This article addresses the need of including acoustical perspectives in the debate on alarm fatigue within the healthcare domain. We show how conceptualisations and proposed solutions to alarm fatigue are unequally distributed across what could be called the ‘alarm chain’: a generic model of the core structural elements and dynamic relations that constitute any alarm scenario. A focal point in the alarm chain – the ‘alarm mediation cleft’ – seems to divide the alarm fatigue literature from the segment of the alarm literature that deals with auditory alarm design. The current healthcare discourse on alarm fatigue is centred around the ‘premediated alarm phase’, which has the consequence of an unfortunate dichotomous approach to the functionality of sound. We address some shortcomings of this approach and outline some methodological implications and potentials of searching for signs of alarm fatigue in the ‘post-mediated alarm phase’

Catch Crops in Organic Farming Systems without Livestock Husbandry - Model Simulations

During the last years, an increasing number of stockless farms in Europe converted to organic farming practice without re-establishing a livestock. Due to the lack of animal manure as a nutrient input, the relocation and the external input of nutrients is limited in those organic cropping systems. The introduction of a one-year green manure fallow in a 4-year crop rotation, including clover-grass mixtures as a green manure crop is the classical strategy to solve at least some of the problems related to the missing livestock. The development of new crop rotations, including an extended use of catch crops and annual green manure (legumes) may be another possibility avoiding the economical loss during the fallow year. Modelling of the C and N turnover in the soil-plant-atmosphere system using the soil-plant-atmosphere model DAISY is one of the tools used for the development of new organic crop rotations. In this paper, we will present simulations based on a field experiment with incorporation of different catch crops. An important factor for the development of new crop rotations for stockless organic farming systems is the expected N mineralisation and immobilisation after incorporation of the plant materials. Therefore, special emphasise will be put on the simulation of N-mineralisation/-immobilisation and of soil microbial biomass N. Furthermore, particulate organic matter C and N as an indicator of remaining plant material under decomposition will be investigated

Physical and chemical fingerprint of protostellar disc formation

(Abridged) The purpose of this paper is to explore and compare the physical and chemical structure of Class I low-mass protostellar sources on protoplanetary disc scales. We present a study of the dust and gas emission towards a representative sample of 12 Class I protostars from the Ophiuchus molecular cloud with the Atacama Large Millimeter/submillimeter Array (ALMA). The continuum at 0.87 mm and molecular transitions from C17O, C34S, H13CO+, CH3OH, SO2 , and C2H were observed at high angular resolution (0.4", ~60 au diameter) towards each source. Disc and stellar masses are estimated from the continuum flux and position-velocity diagrams, and six of the sources show disc-like structures. Towards the more luminous sources, compact emission and large line widths are seen for transitions of SO2 that probe warm gas (Eu ~200 K). In contrast, C17O emission is detected towards the least evolved and less luminous systems. No emission of CH3OH is detected towards any of the continuum peaks, indicating an absence of warm CH3OH gas towards these sources. A power-law relation is seen between the stellar mass and the bolometric luminosity, corresponding to a mass accretion rate of (2.4 +/- 0.6) x 10^-7 Msun/year for the Class I sources. This mass accretion rate is lower than the expected value if the accretion is constant in time and rather points to a scenario of accretion occurring in bursts. The differentiation between C17O and SO2 suggests that they trace different physical components: C17O traces the densest and colder regions of the disc-envelope system, while SO2 may be associated with regions of higher temperature, such as accretion shocks. The lack of warm CH3OH emission suggests that there is no hot-core-like region around any of the sources and that the CH3OH column density averaged over the disc is low.Comment: 20 pages, 16 figures, 8 table

Evidence for a single hydrogen molecule connected by an atomic chain

Stable, single-molecule conducting-bridge configurations are typically identified from peak structures in a conductance histogram. In previous work on Pt with H$_2$ at cryogenic temperatures it has been shown that a peak near 1 $G{_0}$ identifies a single molecule Pt-H$_{2}$-Pt bridge. The histogram shows an additional structure with lower conductance that has not been identified. Here, we show that it is likely due to a hydrogen decorated Pt chain in contact with the H$_2$ molecular bridge.Comment: 4 pages, 4 figure

Far infrared CO and H2_2O emission in intermediate-mass protostars

Intermediate-mass young stellar objects (YSOs) provide a link to understand how feedback from shocks and UV radiation scales from low to high-mass star forming regions. Aims: Our aim is to analyze excitation of CO and H$_2$O in deeply-embedded intermediate-mass YSOs and compare with low-mass and high-mass YSOs. Methods: Herschel/PACS spectral maps are analyzed for 6 YSOs with bolometric luminosities of $L_\mathrm{bol}\sim10^2 - 10^3$ $L_\odot$. The maps cover spatial scales of $\sim 10^4$ AU in several CO and H$_2$O lines located in the $\sim55-210$ $\mu$m range. Results: Rotational diagrams of CO show two temperature components at $T_\mathrm{rot}\sim320$ K and $T_\mathrm{rot}\sim700-800$ K, comparable to low- and high-mass protostars probed at similar spatial scales. The diagrams for H$_2$O show a single component at $T_\mathrm{rot}\sim130$ K, as seen in low-mass protostars, and about $100$ K lower than in high-mass protostars. Since the uncertainties in $T_\mathrm{rot}$ are of the same order as the difference between the intermediate and high-mass protostars, we cannot conclude whether the change in rotational temperature occurs at a specific luminosity, or whether the change is more gradual from low- to high-mass YSOs. Conclusions: Molecular excitation in intermediate-mass protostars is comparable to the central $10^{3}$ AU of low-mass protostars and consistent within the uncertainties with the high-mass protostars probed at $3\cdot10^{3}$ AU scales, suggesting similar shock conditions in all those sources.Comment: Accepted to Astronomy & Astrophysics. 4 pages, 5 figures, 3 table