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Register a new userHiRes Deconvolved Spitzer Images of 89 Protostellar Jets and Outflows: New Data on Evolution of Outflow Morphology
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Thangasamy Velusamy
Publication date
2013
fields
Physics
and research's language is
English
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To study the role of protosellar jets and outflows in the time evolution of the parent cores and the protostars, the astronomical community needs a large enough data base of infrared images of protostars at the highest spatial resolution possible, to reveal the details of their morphology. Spitzer provides unprecedented sensitivity in the infrared to study both the jet and outflow features, however its spatial resolution is limited by its 0.85m mirror. Here we use a high resolution deconvolution algorithm, HiRes, to improve the visualization of spatial morphology by enhancing resolution (to sub-arcsecond levels in the IRAC bands) and removing the contaminating sidelobes from bright sources in a sample of 89 protostellar objects. These reprocessed images are useful to detect: (i) wide angle outflow seen in scattered light; (ii) morphological details of H2 emission in jets and bow shocks; and (iii) compact features in MIPS 24 micron images as protostar/ disk and atomic/ionic line emissions associated with the jets. The HiRes fits image data of such a large homogeneous sample presented here will be useful to the community in studying these protostellar objects. To illustrate the utility of this HiRes sample, we show how the opening angle of the wide angle outflows in 31 sources, all observed in the HiRes processed Spitzer images, correlates with age. Our data suggest a power law fit to opening angle versus age with an exponent of ~0.32 and 0.02, respectively for ages less than 8000 yr and greater than 8000 yr.
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We present and discuss emph{Spitzer} and near-infrared H$_{2}$ observations of a new bi-polar protostellar outflow in the Rosette Molecular Cloud. The outflow is seen in all four IRAC bands and partially as diffuse emission in the MIPS 24 $mu$m band. An embedded MIPS 24 $mu$m source bisects the outflow and appears to be the driving source. This source is coincident with a dark patch seen in absorption in the 8 $mu$m IRAC image. emph{Spitzer} IRAC color analysis of the shocked emission was performed from which thermal and column density maps of the outflow were constructed. Narrow-band near-infrared (NIR) images of the flow reveal H$_2$ emission features coincident with the high temperature regions of the outflow. This outflow has now been given the designation MHO 1321 due to the detection of NIR H$_2$ features. We use these data and maps to probe the physical conditions and structure of the flow.
We present SOFIA/FIFI-LS observations of three Class 0 and one Class I outflows (Cep E, HH 1, HH 212, and L1551 IRS5) in the far-infrared [O I]63mum and [O I]145mum transitions. Spectroscopic [O I]63mum maps enabled us to infer the spatial extent of warm, low-excitation atomic gas within these protostellar outflows. If proper shock conditions prevail, the instantaneous mass-ejection rate is directly connected to the [O I]63mum luminosity. In order to unravel evolutionary trends, we analysed a set of 14 Class 0/I outflow sources that were spatially resolved in the [O I]63mum emission. We compared these data with a sample of 72 Class 0/I/II outflow sources that have been observed with Herschel (WISH, DIGIT, WILL, GASPS surveys) without spatially resolving the [O I]63mum line.
We present an analysis of Spitzer-IRS spectroscopic maps of the L1157 protostellar outflow in the H2 pure-rotational lines from S(0) to S(7). The aim of this work is to derive the physical conditions pertaining to the warm molecular gas and study their variations within the flow. The mid-IR H2 emission follows the morphology of the precessing flow, with peaks correlated with individual CO clumps and H2 2.12{mu}m ro-vibrational emission. More diffuse emission delineating the CO cavities is detected only in the low-laying transitions, with J(lower) less or equal to 2. The H2 line images have been used to construct 2D maps of N(H2), H2 ortho-to-para ratio and temperature spectral index beta, in the assumption of a gas temperature stratification where the H2 column density varies as T^(beta). Variations of these parameters are observed along the flow. In particular, the ortho-to-para ratio ranges from 0.6 to 2.8, highlighting the presence of regions subject to recent shocks where the ortho-to-para ratio has not had time yet to reach the equilibrium value. Near-IR spectroscopic data on ro-vibrational H2 emission have been combined with the mid-IR data and used to derive additional shock parameters in the brightest blue- and red-shifted emission knots. A high abundance of atomic hydrogen (H/H2 about 0.1-0.3) is implied by the observed H2 column densities, assuming n(H2) values as derived by independent SiO observations. The presence of a high fraction of atomic hydrogen, indicates that a partially-dissociative shock component should be considered for the H2 excitation in these localized regions. However, planar shock models, either of C- or J-type, are not able to consistently reproduce all the physical parameters derived from our analysis of the H2 emission. Globally, H2 emission contributes to about 50% of the total shock radiated energy in the L1157 outflow.
We present new details of the structure and morphology of the jets and outflows in HH46/47 as seen in Spitzer infrared images from IRAC and MIPS, reprocessed using the ``HiRes deconvolution technique. HiRes improves the visualization of spatial morphology by enhancing resolution (to sub-arcsec levels in IRAC bands) and removing the contaminating side lobes from bright sources. In addition to sharper views of previously reported bow shocks, we have detected: (i) the sharply-delineated cavity walls of the wide-angle biconical outflow, seen in scattered light on both sides of the protostar, (ii) several very narrow jet features at distances 400 AU to 0.1 pc from the star, and, (iii) compact emissions at MIPS 24 micron coincident with the jet heads, tracing the hottest atomic/ionic gas in the bow shocks.
We present results from three-dimensional, self-gravitating, radiation-hydrodynamic simulations of low-mass protostellar outflows. We construct synthetic observations in 12CO in order to compare with observed outflows and evaluate the effects of beam resolution and outflow orientation on inferred outflow properties. To facilitate the comparison, we develop a quantitative prescription for measuring outflow opening angles. Using this prescription, we demonstrate that, in both simulations and synthetic observations, outflow opening angles broaden with time similarly to observed outflows. However, the interaction between the outflowing gas and the turbulent core envelope produces significant asymmetry between the red and blue shifted outflow lobes. We find that applying a velocity cutoff may result in outflow masses that are underestimated by a factor 5 or more, and masses derived from optically thick CO emission further underpredict the mass of the high-velocity gas by a factor of 5-10. Derived excitation temperatures indicate that outflowing gas is hotter than the ambient gas with temperature rising over time, which is in agreement with the simulation gas temperatures. However, excitation temperatures are otherwise not well correlated with the actual gas temperature.
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