HH 114 MMS: a new chemically active outflow

Context. A small group of bipolar protostellar outflows display strong emission from shock-tracer molecules such as SiO and CH3OH, and are generally referred to as "chemically active." The best-studied outflow from this group is the one in L 1157. Aims. We study the molecular emission from the bipolar outflow powered by the very young stellar object HH 114 MMS and compare its chemical composition with that of the L1157 outflow. Methods. We have used the IRAM 30m radio telescope to observe a number of transitions from CO, SiO, CH3OH, SO, CS, HCN, and HCO+ toward the HH 114 MMS outflow. The observations consist of maps and a two-position molecular survey. Results. The HH 114 MMS outflow presents strong emission from a number of shock-tracer molecules that dominate the appearance of the maps around the central source. The abundance of these molecules is comparable to the abundance in L 1157. Conclusions. The outflow from HH 114 MMS is a spectacular new case of a chemically active outflow.Comment: 4 pages, 3 figures. Accepted for publication in Astronomy & Astrophysic

The function of the secondary lining in the New Austrian Tunnelling Method

The decision to build the Secondary Lining in Route Tunnels which are perforated using the New Austrian Tunnelling Method does not generally depend on reasons of structural strength. The paper discusses the implications of the issue as well as the pros and cons of the current alternative courses of action

The Musca cloud: A 6 pc-long velocity-coherent, sonic filament

Filaments play a central role in the molecular clouds' evolution, but their internal dynamical properties remain poorly characterized. To further explore the physical state of these structures, we have investigated the kinematic properties of the Musca cloud. We have sampled the main axis of this filamentary cloud in $^{13}$CO and C$^{18}$O (2--1) lines using APEX observations. The different line profiles in Musca shows that this cloud presents a continuous and quiescent velocity field along its $\sim$6.5 pc of length. With an internal gas kinematics dominated by thermal motions (i.e., $\sigma_{NT}/c_s\lesssim1$) and large-scale velocity gradients, these results reveal Musca as the longest velocity-coherent, sonic-like object identified so far in the ISM. The transonic properties of Musca present a clear departure from the predicted supersonic velocity dispersions expected in the Larson's velocity dispersion-size relationship, and constitute the first observational evidence of a filament fully decoupled from the turbulent regime over multi-parsec scales.Comment: 12 pages, 6 figures; Accepted for publication in A&

Disk masses in the Orion Molecular Cloud-2: distinguishing time and environment

The mass evolution of protoplanetary disks is driven by both internal processes and external factors, such as photoevaporation. Disentangling these two effects, however, has remained difficult. We measure the dust masses of a sample of 132 disks in the Orion Molecular Cloud (OMC)-2 region, and compare them to (i) externally photoevaporated disks in the Trapezium cluster, and (ii) disks in nearby low-mass star forming regions (SFRs). This allows us to test if initial disk properties are the same in high- and low-mass SFRs, and enables a direct measurement of the effect of external photoevaporation on disks. A ~ $20' \times 4'$ mosaic of 3 mm continuum observations from the Atacama Large Millimeter/submillimeter Array (ALMA) was used to measure the fluxes of 132 disks and 35 protostars >0.5 pc away from the Trapezium. We identify and characterize a sample of 34 point sources not included in the Spitzer catalog on which the sample is based. Of the disks, 37 (28%) are detected, with masses ranging from 7-270 M_e. The detection rate for protostars is higher at 69%. Disks near the Trapezium are found to be less massive by a factor $0.18^{+0.18}_{-0.11}$, implying a mass loss rate of $8\times10^{-8}$ M_sun/yr. Our observations allow us to distinguish the impact of time and environment on disk evolution in a single SFR. The disk mass distribution in OMC-2 is statistically indistinguishable from that in nearby low-mass SFRs, like Lupus and Taurus. We conclude that age is the main factor determining the evolution of these disks. This result is robust with respect to assumptions of dust temperature, sample incompleteness and biases. The difference between the OMC-2 and Trapezium cluster samples is consistent with mass loss driven by far-ultraviolet radiation near the Trapezium. Together, this implies that in isolation, disk formation and evolution proceed similarly, regardless of cloud mass.Comment: Accepted for publication in A&A. 16 pages, 6 figure

Non-isothermal filaments in equilibrium

The physical properties of the so-called Ostriker isothermal filament (Ostriker 1964) have been classically used as benchmark to interpret the stability of the filaments observed in nearby clouds. However, recent continuum studies have shown that the internal structure of the filaments depart from the isothermality, typically exhibiting radially increasing temperature gradients. The presence of internal temperature gradients within filaments suggests that the equilibrium configuration of these objects should be therefore revisited. The main goal of this work is to theoretically explore how the equilibrium structure of a filament changes in a non-isothermal configuration. We solve the hydrostatic equilibrium equation assuming temperature gradients similar to those derived from observations. We obtain a new set of equilibrium solutions for non-isothermal filaments with both linear and asymptotically constant temperature gradients. Our results show that, for sufficiently large internal temperature gradients, a non-isothermal filament could present significantly larger masses per unit length and shallower density profiles than the isothermal filament without collapsing by its own gravity. We conclude that filaments can reach an equilibrium configuration under non-isothermal conditions. Detailed studies of both the internal mass distribution and temperature gradients within filaments are then needed in order to judge the physical state of filaments.Comment: 5 pages, 2 figures, accepted for publication in A&

Fibers in the NGC1333 proto-cluster

Are the initial conditions for clustered star formation the same as for non-clustered star formation? To investigate the initial gas properties in young proto-clusters we carried out a comprehensive and high-sensitivity study of the internal structure, density, temperature, and kinematics of the dense gas content of the NGC1333 region in Perseus, one of the nearest and best studied embedded clusters. The analysis of the gas velocities in the Position-Position-Velocity space reveals an intricate underlying gas organization both in space and velocity. We identified a total of 14 velocity-coherent, (tran-)sonic structures within NGC1333, with similar physical and kinematic properties than those quiescent, star-forming (aka fertile) fibers previously identified in low-mass star-forming clouds. These fibers are arranged in a complex spatial network, build-up the observed total column density, and contain the dense cores and protostars in this cloud. Our results demonstrate that the presence of fibers is not restricted to low-mass clouds but can be extended to regions of increasing mass and complexity. We propose that the observational dichotomy between clustered and non-clustered star-forming regions might be naturally explained by the distinct spatial density of fertile fibers in these environments.Comment: 25 pages, 17 figures; Accepted for publication in A&

Gravitational collapse of the OMC-1 region

We have investigated the global dynamical state of the Integral Shaped Filament in the Orion A cloud using new N$_2$H$^+$ (1-0) large-scale, IRAM30m observations. Our analysis of its internal gas dynamics reveals the presence of accelerated motions towards the Orion Nebula Cluster, showing a characteristic blue-shifted profile centred at the position of the OMC-1 South region. The properties of these observed gas motions (profile, extension, and magnitude) are consistent with the expected accelerations for the gravitational collapse of the OMC-1 region and explain both the physical and kinematic structure of this cloud.Comment: 5 pages, 2 figures; Accepted by A&

Propiedades de la trayectoria descrita por un punto cualquiera de una barra cuyos extremos se mueven sobre una curva dada

Se estudian las propiedades de la trayectoria, que dependen de la longitud de la barra y del punto que se torne de ella. Determinación del área comprendida entre la curva dada y la· obtenida. Aplicaciones para la división por medios mecánicos, de superficies cerradas; establecimiento de curvas de transición; estudio de la circulación de vehículos en curva, etc