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Register a new userFabry-Perot Kinematics of HH 202, 203-204 in the Orion Nebula: Are they part of a Big Bipolar Outflow?
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Added by
Eduardo de la Fuente Acosta
Publication date
2001
fields
Physics
and research's language is
English
Authors
Margarita Rosado
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We present a kinematic study of the Herbig-Haro objects HH 202, 203 and 204 using Halpha and [NII] Fabry-Perot velocity maps. For HH 202 we find new features that could belong to this HH object or that perhaps are associated with an outflow different from HH 202. Because of its high velocity (up to 100 km/seg) this outflow probably can be a HH flow not catalogued previously. Large internal motions are found in the fainter regions of HH 203-204, as well as evidence of transverse density gradients. We show that the apex of HH 204 is the zone of maximum velocity in agreement with bow shock models. From our studies, we find kinematic evidence that suggests that HH 203-204 and HH 202 are part of a single and large (approx 0.55 pc) HH flow.
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We have obtained a Halpha position-velocity cube from Fabry-Perot interferometric observations of the HH 110 flow. We analyze the results in terms of anisotropic wavelet transforms, from which we derive the spatial distribution of the knots as well as their characteristic sizes (along and across the outflow axis). We then study the spatial behaviour of the line width and the central radial velocity. The results are interpreted in terms of a simple ``mean flow+turbulent eddy jet/wake model. We find that most of the observed kinematics appear to be a direct result of the mean flow, on which are superposed low amplitude (35 km/s) turbulent velocities.
We present results from integral field optical spectroscopy with the Potsdam Multi-Aperture Spectrograph of the Herbig-Haro (HH) object HH 204, with a spatial sampling of 1 x 1 arcsec^2. We have obtained maps of different emission lines, physical conditions and ionic abundances from collisionally excited lines. The ionization structure of the object indicates that the head of the bow shock is optically thick and has developed a trapped ionization front. The density at the head is at least five times larger than in the background ionized gas. We discover a narrow arc of high T_e([N II]) values delineating the southeast edge of the head. The temperature in this zone is about 1,000 K higher than in the rest of the field and should correspond to a shock-heated zone at the leading working surface of the gas flow. This is the first time this kind of feature is observed in a photoionized HH object. We find that the O^+ and O abundance maps show anomalous values at separate areas of the bow shock probably due to: a) overestimation of the collisional de-excitation effects of the [O II] lines in the compressed gas at the head of the bow shock, and b) the use of a too high T_e([N II]) at the area of the leading working surface of the flow.
One of the outstanding problems in star-formation theory concerns the transfer of angular momentum such that mass can accrete onto a newly born young stellar object (YSO). From a theoretical standpoint, outflows and jets are predicted to play an essential role in angular momentum transfer and their rotation motions have been reported for both low- and high-mass YSOs. However, little quantitative discussion on outflow launching mechanisms have been presented for high-mass YSOs due to a lack of observational data. Here we present a clear signature of rotation in the bipolar outflow driven by Orion Source I, a high-mass YSO candidate, using the Atacama Large Millimeter/Submillimeter Array (ALMA). A rotational transition of silicon monoxide (Si18O) reveals a velocity gradient perpendicular to the outflow axis which is consistent with that of the circumstellar disk traced by a high-excitation water (H2O) line. The launching radii and outward velocity of the outflow are estimated to be >10 au and 10 km s-1, respectively. These parameters rule out a possibility that the observed outflow is produced by entrainment of a high-velocity jet, and that contribution from stellar-wind or X-wind which have smaller launching radii are significant in the case of Source I. Thus, present results provide a convincing evidence of a rotating outflow directly driven by the magneto-centrifugal disk wind launched by a high-mass YSO candidate.
In this work we derive the full 3-D kinematics of the near-infrared outflow HH 223, located in the dark cloud Lynds 723 (L723), where a well-defined quadrupolar CO outflow is found. HH 223 appears projected onto the two lobes of the east-west CO outflow. The radio continuum source VLA 2, towards the centre of the CO outflow, harbours a multiple system of low-mass young stellar objects. One of the components has been proposed to be the exciting source of the east-west CO outflow. From the analisys of the kinematics, we get further evidence on the relationship between the near-infrared and CO outflows and on the location of their exciting source. The proper motions were derived using multi-epoch, narrow-band H$_2$ (2.122 $mu$m line) images. Radial velocities were derived from the 2.122 $mu$m line of the spectra. Because of the extended (~5 arcmin), S-shaped morphology of the target, the spectra were obtained with the Multi-Object-Spectroscopy (MOS) observing mode using the instrument LIRIS at the 4.2m William Herschel Telescope. To our knowledge, this work is the first time that MOS observing mode has been successfully used in the near infrared range for an extended target.
The common assumption that Theta-1-Ori C is the dominant ionizing source for the Orion Nebula is critically examined. This assumption underlies much of the existing analysis of the nebula. In this paper we establish through comparison of the relative strengths of emission lines with expectations from Cloudy models and through the direction of the bright edges of proplyds that Theta-2-Ori-A, which lies beyond the Bright Bar, also plays an important role. Theta-1-Ori-C does dominate ionization in the inner part of the Orion Nebula, but outside of the Bright Bar as far as the southeast boundary of the Extended Orion Nebula, Theta-2-Ori-A is the dominant source. In addition to identifying the ionizing star in sample regions, we were able to locate those portions of the nebula in 3-D. This analysis illustrates the power of MUSE spectral imaging observations in identifying sources of ionization in extended regions.
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