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Register a new userA one-sided knot ejection at the core of the HH 111 outflow
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L. Gomez
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We present an astrometry study of the radio source VLA 1 at the core of the HH 111 outflow using new data (2007) as well as archival observations (1992-1996). All data were taken at 3.6 cm with the Very Large Array in its most extended (A) configuration. The source VLA 1 has undergone a dramatic morphological change, showing a one-sided knot ejection in the 2007 epoch. We also report on the detection of a 3.6 cm compact continuum source (VLA 3) located at (-10.6,98.7) from VLA 1. No significant absolute proper motions were found for VLA 1 and VLA 3 and the upper limits are consistent with those found for (embedded) radio sources in the Orion Nebula. We favor the interpretation that in the continuum at 3.6 cm we are observing two nearly perpendicular jets. HH 111 presents a new case of one-sided jet ejection in a young stellar object. The Galactic (or extragalactic) nature of VLA 3 remains unclear.
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We present sensitive, high angular resolution ($0rlap.{}05$) VLA continuum observations made at 7 mm of the core of the HH 111/121 quadrupolar outflow. We estimate that at this wavelength the continuum emission is dominated by dust, although a significant free-free contribution ($sim$30%) is still present. The observed structure is formed by two overlapping, elongated sources approximately perpendicular to each other as viewed from Earth. We interpret this structure as either tracing two circumstellar disks that exist around each of the protostars of the close binary source at the core of this quadrupolar outflow or a disk and a jet perpendicular to it. Both interpretations have advantages and disadvantages, and future high angular resolution spectroscopic millimeter observations are required to favor one of them in a more conclusive way.
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.
We present millimeter line observations of the HH 111 outflow and its driving source. The molecular gas emission observed with IRAM 30m and the CSO reveals a small condensation of cold and dense gas. The low-velocity outflow has been mapped with the IRAM PdBI interferometer. The cold gas is distributed in a hollow cylinder surrounding the optical jet. The formation of this cavity and its kinematics are well accounted for in the frame of outflow gas entrainment by jet bow shocks. Evidence of gas acceleration is found along the cavity walls, correlated with the presence of optical bow shocks. The cavity has been expanding with a mean velocity of 4 km/s on a timescale of 8700 yr, similar to the dynamical age of the optical jet. The separation of the inner walls reaches 8-10, which matches the transverse size of the wings in the bow shock. CSO observations of the J=7-6 line show evidence of a high-velocity and hot gas component (T=300-1000 K) with a low filling factor, associated with shocked molecular gas in the jet. [CI] observations are consistent with C-type non-dissociative shocks. Mapping of the high-velocity molecular bullets B1-B3 located beyond the optical jet, with the PdBI, reveals small structures of 3 by 7 flattened perpendicular to the flow direction. They are made of cold gas of moderate density(a few 10^3 cm-3). The bullets appear to expand into the low-density surrounding medium. We conclude that they are probably shocked gas knots resulting from past time-variable ejections in the jet.
We present the results of Very Large Array NH$_{3}$ $(J,K)=(1,1)$ and $(2,2)$ observations of the HH 111/HH 121 protostellar system. HH 111, with a spectacular collimated optical jet, is one of the most well-known Herbig-Haro objects. We report the detection of a new source (NH$_{3}-$S) in the vicinity of HH 111/HH 121 ($sim$0.03 pc from the HH 111 jet source) in two epochs of the ammonia observations. This constitutes the first detection of this source, in a region which has been thoroughly covered previously by both continuum and spectral line interferometric observations. We study the kinematic and physical properties of HH 111 and the newly discovered NH$_{3}-$S. We also use HCO$^{+}$ and HCN $(J=4-3)$ data obtained with the James Clerk Maxwell Telescope and archival Atacama Large Millimeter/submillimeter Array $^{13}$CO, $^{12}$CO, and C$^{18}$O $(J=2-1)$, N$_2$D$^{+}$ $(J=3-2)$, and $^{13}$CS $(J=5-4)$ data to gain insight into the nature of NH$_{3}-$S. The chemical structure of NH$_3-$S shows evidence for selective freeze-out, an inherent characteristic of dense cold cores. The inner part of NH$_3-$S shows subsonic non-thermal velocity dispersions indicating a coherent core, while they increase in the direction of the jets. Archival near- to far-infrared data show no indication of any embedded source in NH$_3-$S. The properties of NH$_3-$S and its location in the infrared dark cloud suggest that it is a starless core located in a turbulent medium with turbulence induced by Herbig-Haro jets and associated outflows. More data is needed to fully understand the physical and chemical properties of NH$_3-$S and if/how its evolution is affected by nearby jets.
We present 70 and 160 micron Herschel science demonstration images of a field in the Orion A molecular cloud that contains the prototypical Herbig-Haro objects HH 1 and 2, obtained with the Photodetector Array Camera and Spectrometer (PACS). These observations demonstrate Herschels unprecedented ability to study the rich population of protostars in the Orion molecular clouds at the wavelengths where they emit most of their luminosity. The four protostars previously identified by Spitzer 3.6-40 micron imaging and spectroscopy are detected in the 70 micron band, and three are clearly detected at 160 microns. We measure photometry of the protostars in the PACS bands and assemble their spectral energy distributions (SEDs) from 1 to 870 microns with these data, Spitzer spectra and photometry, 2MASS data, and APEX sub-mm data. The SEDs are fit to models generated with radiative transfer codes. From these fits we can constrain the fundamental properties of the protostars. We find luminosities in the range 12-84 L_sun and envelope densities spanning over two orders of magnitude. This implies that the four protostars have a wide range of envelope infall rates and evolutionary states: two have dense, infalling envelopes, while the other two have only residual envelopes. We also show the highly irregular and filamentary structure of the cold dust and gas surrounding the protostars as traced at 160 microns.
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