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TOPIC: Orion Nebula


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RE: Orion Nebula
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Title: Ionised gas diagnostics from protoplanetary discs in the Orion Nebula and the abundance discrepancy problem
Authors: A. Mesa-Delgado (1,2,3,4), M. Núñez-Díaz (3,4), C. Esteban (3,4), J. García-Rojas (3,4), N. Flores-Fajardo (5), L. López-Martín (3,4), Y. G. Tsamis (6), W. J. Henney (5) ((1) Departamento de Astronomía y Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Santiago, Chile, (2) Institute for Astronomy, Honolulu, HI, USA, (3) Instituto de Astrofísica de Canarias, Tenerife, Spain, (4) Departamento de Astrofísica, Universidad de La Laguna, Tenerife, Spain, (5) Centro de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, Campus Morelia, Michoacán, México, (6) European Southern Observatory, Garching bei München, Germany)

We present results from integral field spectroscopy with PMAS. The observed field contains: five protoplanetary discs (also known as proplyds), the high-velocity jet HH 514 and a bowshock. Spatial distribution maps are obtained for different emission line fluxes, the c(H{\beta}) coefficient, electron densities and temperatures, ionic abundances of different ions from collisionally excited lines (CELs), C2+ and O2+ abundances from recombination lines (RLs) and the abundance discrepancy factor of O2+, ADF(O2+). We find that collisional de-excitation has a major influence on the line fluxes in the proplyds. If this is not properly accounted for then physical conditions deduced from commonly used line ratios will be in error, leading to unreliable chemical abundances for these objects. We obtain the intrinsic emission of the proplyds 177-341, 170-337 and 170-334 by a direct subtraction of the background emission, though the last two present some background contamination due to their small sizes. A detailed analysis of 177-341 spectra reveals the presence of high-density gas (3.8 x 10^5 cm^-3) in contrast to the typical values observed in the background gas of the nebula (3800 cm^-3). We also explore how the background subtraction could be affected by the possible opacity of the proplyd. We construct a physical model for the proplyd 177-341 finding a good agreement between the predicted and observed line ratios. Finally, we find that the use of reliable physical conditions returns an ADF(O2+) about zero for the intrinsic spectra of 177-341, while the background emission presents the typical ADF(O2+) observed in the Orion Nebula. We conclude that the presence of high-density ionised gas is severely affecting the abundances determined from CELs and, therefore, those from RLs should be considered as a better approximation to the true abundances.

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Orion Molecular Cloud 1
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Title: A 3D view of the outflow in the Orion Molecular Cloud 1 (OMC-1)
Authors: H. D. Nissen, N. J. Cunningham, M. Gustafsson, J. Bally, J.-L. Lemaire, C. Favre, D. Field

The fast outflow emerging from a region associated with massive star formation in the Orion Molecular Cloud 1 (OMC-1), located behind the Orion Nebula, appears to have been set in motion by an explosive event. Here we study the structure and dynamics of outflows in OMC-1. We combine radial velocity and proper motion data for near-IR emission of molecular hydrogen to obtain the first 3-dimensional (3D) structure of the OMC-1 outflow. Our work illustrates a new diagnostic tool for studies of star formation that will be exploited in the near future with the advent of high spatial resolution spectro-imaging in particular with data from the Atacama Large Millimetre Array (ALMA). We use published radial and proper motion velocities obtained from the shock-excited vibrational emission in the H2 v=1-0 S(1) line at 2.122 \mu m obtained with the GriF instrument on the Canada-France-Hawaii Telescope, the Apache Point Observatory, the Anglo-Australian Observatory and the Subaru Telescope. These data give the 3D velocity of ejecta yielding a 3D reconstruction of the outflows. This allows one to view the material from different vantage points in space giving considerable insight into the geometry. Our analysis indicates that the ejection occurred <720 years ago from a distorted ring-like structure of ~15" (6000 AU) in diameter centred on the proposed point of close encounter of the stars BN, source I and maybe also source n. We propose a simple model involving curvature of shock trajectories in magnetic fields through which the origin of the explosion and the centre defined by extrapolated proper motions of BN, I and n may be brought into spatial coincidence.

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Fledgling stars flicker in the heart of Orion
 

Orion_Herschel_Spitzer_medium,0.jpg

Astronomers using ESA's Herschel and NASA's Spitzer space telescopes have detected surprisingly rapid changes in the brightness of embryonic stars within the well-known Orion Nebula.
Images from Herschel's far-infrared instrument and two of Spitzer's instruments working at shorter wavelengths give us a more detailed picture of stars growing in the heart of one of the most famous objects in the night sky.

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Young Stars Flicker Amidst Clouds of Gas and Dust

Astronomers have spotted young stars in the Orion nebula changing right before their eyes, thanks to the European Space Agency's Herschel Space Observatory and NASA's Spitzer Space Telescope. The colorful specks -- developing stars strung across the image -- are rapidly heating up and cooling down, speaking to the turbulent, rough-and-tumble process of reaching full stellar adulthood.
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Title: First Science Observations with SOFIA/FORCAST: 6 to 37 micron Imaging of the Central Orion Nebula
Authors: R. Y. Shuping, Mark R. Morris, Terry L. Herter, Joseph D. Adams, G. E. Gull, J. Schoenwald, C. P. Henderson, E. E. Becklin, James M. De Buizer, William D. Vacca, Hans Zinnecker, S. Thomas Megeath

We present new mid-infrared images of the central region of the Orion Nebula using the newly commissioned SOFIA airborne telescope and its 5 -- 40 micron camera FORCAST. The 37.1 micron images represent the highest resolution observations (<4") ever obtained of this region at these wavelengths. After BN/KL (which is described in a separate letter in this issue), the dominant source at all wavelengths except 37.1 micron is the Ney-Allen Nebula, a crescent-shaped extended source associated with theta 1D. The morphology of the Ney-Allen nebula in our images is consistent with the interpretation that it is ambient dust swept up by the stellar wind from theta 1D, as suggested by Smith et al. (2005). Our observations also reveal emission from two "proplyds" (proto-planetary disks), and a few embedded young stellar objects (YSOs; IRc9, and OMC1S IRS1, 2, and 10). The spectral energy distribution for IRc9 is presented and fitted with standard YSO models from Robitaille et al. (2007) to constrain the total luminosity, disk size, and envelope size. The diffuse, nebular emission we observe at all FORCAST wavelengths is most likely from the background photodissociation region (PDR) and shows structure that coincides roughly with H_alpha and [N II] emission. We conclude that the spatial variations in the diffuse emission are likely due to undulations in the surface of the background PDR.

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Orion Trapezium Cluster
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Astronomy deepsky video Orion nebula by telescope



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Orion Molecular Cloud 3 region
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Title: Discovery of the Youngest Molecular Outflow associated with an Intermediate-mass protostellar Core, MMS-6/OMC-3
Authors: Satoko Takahashi (ASIAA), Paul Ho (ASIAA and CfA)

We present sub-arcsecond resolution HCN (4-3) and CO (3-2) observations made with the Submillimeter Array (SMA), toward an extremely young intermediate-mass protostellar core, MMS 6-main, located in the Orion Molecular Cloud 3 region (OMC-3). We have successfully imaged a compact molecular outflow lobe (~1500 AU) associated with MMS6-main, which is also the smallest molecular outflow ever found in the intermediate-mass protostellar cores. The dynamical time scale of this outflow is estimated to be <100 yr. The line width dramatically increases downstream at the end of the molecular outflow ({\Delta}v~25 km s^{-1}), and clearly shows the bow-shock type velocity structure. The estimated outflow mass (~10^{-4} M_{sun}) and outflow size are approximately 2-4 orders and 1-3 orders of magnitude smaller, while the outflow force (~10^{-4} M_{sun} km s^{-1} yr^{-1}) is similar, as compared to the other molecular outflows studied in OMC-2/3. These results show that MMS 6-main is a protostellar core at the earliest evolutionary stage, most likely shortly after the 2nd core formation.

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Orion Nebula With Leonid Meteor Shower

Imaged with a self mod Canon 500D with an Orion ShortTube 80 on an Atlas EQ-G. These are a combination of unedited 15 second x 236 images at 1600 ISO. 



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New Planetary Systems In The Orion Nebula



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Panning across the Orion Nebula


Credit: ESO and Igor Chekalin

In this video we pan across a new image of the Orion Nebula from the Wide Field Imager camera on the MPG/ESO 2.2-metre telescope at the La Silla Observatory. This provides a closer look at the many strange and fascinating structures hidden in this very detailed image. The image is a composite of several exposures taken through a total of five different filters. Light that passed through a red filter, as well as light from a filter that shows the glowing hydrogen gas, is coloured red. Light in the yellow--green part of the spectrum is coloured green, blue light is coloured blue and light that passed through an ultraviolet filter has been coloured purple. The exposure times were about 52 minutes through each filter.


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