Imaging Spectrophotometry of the Orion Nebula Core. I. Emission-Line Mapping and Physical Conditions: Erratum

1993 ◽  
Vol 408 ◽  
pp. 758 ◽  
Author(s):  
Richard W. Pogge ◽  
J. Michael Owen ◽  
Bruce Atwood
Keyword(s):  
Emission Line ◽  
Orion Nebula ◽  
Physical Conditions

scholarly journals The nature of the cometary knots in the Helix Nebula as determined by HST images

1997 ◽  
Vol 180 ◽  
pp. 332-340
Author(s):  
C. R. O'Dell ◽  
A. Burkert
Keyword(s):  
Emission Line ◽  
Color Image ◽  
New Technology ◽  
Central Star ◽  
Detailed Examination ◽  
The Sun ◽  
Orion Nebula ◽  
The North ◽  
Detection Of Objects ◽  
Single Field

In a brief paper at the first meeting of this series, Vorontzov-Velyaminov (1968) presented the first examination of the fine scale structure found in the Helix Nebula. At that time he used the term “filaments” to describe them, although the results of improved spatial resolution during the ensuing decades (Malin 1982, Meaburn et al. 1992, Walsh & Meaburn 1993) show that the term “Cometary Knot”(CK) communicates a clearer picture of their form. The most useful groundbased images are those of Meaburn et al.(1992) made with the New Technology Telescope, which showed that each CK has a characteristic form, composed of a central dark knot, accompanied by a luminous cusp on the substellar side, and accompanied by a thin sheath of luminous material extending from the edge of the cusp to large distances. Owing to their much higher density, the Cusps are of lower ionization than the nebula as a whole, so that one sees the central dark knots, which evidently contain significant amounts of dust, in silhouette against the background nebular emission. Radio observations of the CO line show that the CK are also sources of molecular emission (Huggins et al.1992). The groundbased emission line images show that the “tails” trailing away from the Cusps lie closely on radial lines passing between the Cusp and the Central Star. Although these objects appear to be diving towards the Central Star, such an interpretation is naive, as their form must be determined by a central repulsive force arising from the star, much as true comets in our Solar System may trail their tails behind while approaching the Sun but actually follow their tails as they recede from the Sun. We also now know, from yet another excellent study by Meaburn et al. (1996) that the CK as a group are expanding away from the Central Star, although this group velocity of about 10 km s–1 is about half that value of 21 km s–1 characteristic of the nebula as a whole (Taylor 1977,Terrett 1979). The greatest breakthrough in imaging was the Hubble Space Telescope's WFPC2 (O'Dell & Handron 1996, hereafter O&H) program on a single field of view (FOV) in the north ring of the Helix in Hα, [NII], and [OIII]. One year later the same field was reimaged in [OI] and with the f547m filter, the newer observations allowing calibration of the emission line images with correction for the underlying continuum. A second, contiguous field, was also imaged, in all five filters. The results of both sets of observations are used in this paper and a combined color image is shown in the rear section of this volume. The method of calibration was the same as that used in studies of the Orion Nebula (Hu 1993). Details of the calibration and digital copies of the images can be obtained from the first author. The new observations show heretofore unseen structure which is discussed in the following sections. They indicate that there are about 3500 detectable CK in the entire Helix Nebula, with the actual number probably being much larger as strong observational selection effects operate against detection of objects far from the Central Star. The images also show that the previously known orientation along radial lines is followed, but a detailed examination shows that the tails show small local variations, as if additional, non-radial, forces are acting on them (Fig.4). O&H demonstrated that the chord diameters, measured across the cusps, decrease from about 1.8″ at 120″ distance from the Central Star to about 0.6″ at 180″. There are so many known CK that one cannot use a sequential system of designation. In this paper we will use a coordinate based system, dividing the nebula into boxes of 1″ in Declination and 0.1s of Right Ascension and dropping the values common to all of the CK. Therefore, a CK located at 22:29:42.331 −20:47:32.1 would have the designation Helix 423-732. This system will allow future studies to uniquely identify all CK with only six digits within the range of declination −20:45:00 and −20:55:00, with any objects found north or south of this range having either 4 or 5 inserted as an additional digit immediately after the hyphen. Epoch 2000 is used for the positions and the position is judged to be at the center of the dark knot.

Near infrared spectroscopy of protostars

1981 ◽  
Vol 303 (1480) ◽  
pp. 487-496
Keyword(s):  
Infrared Spectroscopy ◽  
Near Infrared Spectroscopy ◽  
Gas Dynamics ◽  
Near Infrared ◽  
Molecular Gas ◽  
Orion Nebula ◽  
Ionized Gas ◽  
Physical Conditions ◽  
Vibrational Bands ◽  
Optical Wavelengths

Observational study of protostars and their immediate environs has recently become possible as a result of advances in infrared spectroscopy, especially in the near infrared (A = 2—5 pm). Although such stars are totally obscured at optical wavelengths by the enshrouding dust and gas from which they formed, the near infrared spectroscopy has yielded detection of emission lines from both ionized gas and high excitation molecular gas ( T >2000 K) probably within a few astronomical units of several such sources (e.g. the BN object in the Orion nebula). The former lines provide the first constraints on the spectral type and temperature of the protostar; the latter reveal the physical conditions (density and temperature) and gas dynamics in the immediate protostellar nebula. . Data on the BN object covering the CO, 13 CO, and H 2 vibrational bands and the H II lines are presented as an illustration of these techniques.

scholarly journals Near-IR emission line imaging of PN

1997 ◽  
Vol 180 ◽  
pp. 237-237
Author(s):  
T.M. Hodge ◽  
C.E. Woodward ◽  
D.M. Kelly ◽  
J. Fischer ◽  
M. A. Greenhouse ◽  
...  
Keyword(s):  
Emission Line ◽  
Ionization Potential ◽  
Orion Nebula ◽  
Spatial Studies ◽  
Spatially Resolved ◽  
Ngc 7027 ◽  
Line Imaging ◽  
Ngc 7662 ◽  
Physical And Chemical ◽  
Ir Emission

Spatial studies of the emission line regions in planetary nebulae (PN) can provide insight into the physical and chemical environments across the nebulae. In a collaborative effort by the coauthors, a K-band Fabry-Perot etalon has been coupled with an advanced 256 × 256 InSb focal plane array at the Wyoming Infrared Observatory 2.3m telescope. This system permits us to obtain spatially resolved, 0.24″/pixel, moderate spectral resolution (R ≈ 800), flux-density IR emission line images of astronomical sources. We obtained continuum-subtracted images of Br γ, HeI 2.06 μm, the 2-μm UIR features, and the 3.3 μm PAH dust feature in the PN NGC 6572, NGC 7027, and NGC 7662. One objective was to determine the spatial morphology of two unidentified emission lines, UIR1−2.199 μm, and UIR2−2.287 μm (Geballe et al. 1991). These UIR lines appear in the spectra of many PN (Hora et al. 1997) and in the Orion Nebula (Luhman & Rieke 1996). Geballe et al. suggested that the UIR lines are most likely forbidden transitions and showed that the parent ion ionization potential is ≈ 30–40 eV, while the ionization potential for the ions themselves is 40–60 eV. Here we directly compare the distribution of the UIR emitters to that of the gas (H+,He+) and dust (PAHs).

scholarly journals Structure and physical conditions in the Huygens region of the Orion nebula

2016 ◽  
Vol 464 (4) ◽  
pp. 4835-4857 ◽  
Author(s):  
C. R. O'Dell ◽  
G. J. Ferland ◽  
M. Peimbert
Keyword(s):  
Orion Nebula ◽  
Physical Conditions

scholarly journals The Relationship Between the Emission-Line Spectra and X-Ray/UV Continuum

1997 ◽  
Vol 159 ◽  
pp. 252-253
Author(s):  
Youjun Lu ◽  
Tinggui Wang
Keyword(s):  
Emission Line ◽  
Inverse Correlation ◽  
Baldwin Effect ◽  
Spectral Parameters ◽  
X Ray ◽  
Physical Conditions ◽  
Broad Emission ◽  
The Baldwin Effect ◽  
The Relationship ◽  
The Continuum

According to photoionization calculations, the broad emission-line (BEL) spectrum depends not only on the physical conditions of line-emitting gas, but also on the spectral shape of incident ionizing continuum, especially from the UV to X-ray. Analysis of emission-line spectra and their correlations with the continuum, therefore, provide a way of probing the anisotropy of ionizing continuum on the BLR scale, which is predicted by current models. Previous works have concentrated on explaining the Baldwin effect, an inverse correlation between equivalent width and continuum luminosity. In this contribution, we present the results of an analysis of 75 AGNs which have well-determined soft X-ray spectral parameters from ROSAT and UV line and continuum measurements.

scholarly journals A New Molecular Core in L1641

1987 ◽  
Vol 115 ◽  
pp. 81-82
Author(s):  
H. Takaba ◽  
Y. Fukui
Keyword(s):  
Star Formation ◽  
Emission Line ◽  
Hot Spots ◽  
Orion Nebula ◽  
Dark Cloud ◽  
Star Forming ◽  
Star Forming Regions ◽  
The North ◽  
Molecular Core ◽  
A Site

L1641 is a large dark cloud which extends 6.3 degree2 to the south of the Orion nebula (Lynds 1962). This region contains a reflection nebula, NGC 1999, several emission line stars and Herbig-Haro objects and is thought to be a site of on-going star formation. A CO(J = 1-0) map obtained with the Nagoya 1.5 m telescope (Takano 1983) revealed that CO hot spots extend further to the north by ∼ 30′ from NGC 1999. This suggests that L1641 may contain other regions of recent star formation. Therefore, we have mapped the L1641 cloud to investigate if there are other star-forming regions in it.

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