VLT/NACO infrared adaptive optics images  of small scale structures in OMC1

Lacombe, F.; Gendron, É.; Rouan, D.; Clénet, Y.; Field, D.; Lemaire, J. L.; Gustafsson, M.; Lagrange, Anne-Marie; Mouillet, D.; Rousset, G.; Fusco, Thierry; Rousset-Rouvière, Laurent; Serván, B.; Marlot, C.; Feautrier, Philippe

doi:10.1051/0004-6361:20040030

Cited by 21 publications

(39 citation statements)

References 34 publications

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“…This possibility is illustrated well by the comparison of the H 2 2.12 μm map of Lacombe et al (2004) (Fig. 20) with the Subaru deep exposure (Fig.…”

Section: Hcooch 3 and Ir 11 μM Mapmentioning

confidence: 59%

“…HCOOCH 3 and 2.12 μm H 2 emission MF1: a most striking spatial correlation is observed between the methyl formate distribution at the MF1 peak and the 2.12 μm H 2 emission imaged by Lacombe et al (2004) with adaptative optics (NACO) at the Very Large Telescope. This is shown in Fig.…”

Section: Hcooch 3 and Ir 11 μM Mapmentioning

confidence: 92%

“…21, reproduced in extenso in Shuping et al 2004). The larger extension of the H 2 emission seen in the Subaru map indicates that a rather "thin" layer prevented some H 2 peaks to be visible in the Lacombe et al (2004) map. For a few H 2 emission spots in this field Colgan et al (2007) estimated indeed a foreground absorption corresponding to A v = 4−8.…”

Section: Hcooch 3 and Ir 11 μM Mapmentioning

confidence: 95%

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HCOOCH₃as a probe of temperature and structure in Orion-KL

Favre

Despois

Brouillet

et al. 2011

A&A

100

238

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Context. The Orion Kleinmann-Low nebula (Orion-KL) is a complex region of star formation. Whereas its proximity allows studies on a scale of a few hundred AU, spectral confusion makes it difficult to identify molecules with low abundances. Aims. We studied an important oxygenated molecule, HCOOCH 3 , to characterize the physical conditions, temperature, and density of the different molecular source components. Methyl formate presents strong close rotational transitions covering a wide range of energy, and its emission in Orion-KL is not contaminated by the emission of N-bearing molecules. This study will help in the future 1) to constrain chemical models for the formation of methyl formate in gas phase or on grain mantles and 2) to search for more complex or prebiotic molecules. Methods. We used high-resolution observations from the IRAM Plateau de Bure Interferometer to reduce spectral confusion and to better isolate the molecular emission regions. We used twelve data sets with a spatial resolution down to 1.8 × 0.8 . Continuum emission was subtracted by selecting apparently line-free channels. Results. We identify 28 methyl formate emission peaks throughout the 50 field of observations. The two strongest peaks, named MF1 and MF2, are in the Compact Ridge and in the southwest of the Hot Core, respectively. From a comparison with single-dish observations, we estimate that we miss less than 15% of the flux and that spectral confusion is still prevailing as half of the expected transitions are blended over the region. Assuming that the transitions are thermalized, we derive the temperature at the five main emission peaks. At the MF1 position in the Compact Ridge we find a temperature of 80 K in a 1.8 × 0.8 beam size and 120 K on a larger scale (3.6 × 2.2 ), suggesting an external source of heating, whereas the temperature is about 130 K at the MF2 position on both scales. Transitions of methyl formate in its first torsionally excited state are detected as well, and the good agreement of the positions on the rotational diagrams between the ground state and the v t = 1 transitions suggests a similar temperature. The LSR velocity of the gas is between 7.5 and 8.0 km s −1 depending on the positions and column density peaks vary from 1.6 × 10 16 to 1.6 × 10 17 cm −2 . A second velocity component is observed around 9−10 km s −1 in a north-south structure stretching from the Compact Ridge up to the BN object, and this component is warmer at the MF1 peak. The two other C 2 H 4 O 2 isomers are not detected, and the derived upper limit for the column density is ≤3 × 10 14 cm −2 for glycolaldehyde and ≤2 × 10 15 cm −2 for acetic acid. From the 223 GHz continuum map, we identify several dust clumps with associated gas masses in the range 0.8 to 5.8 M . Assuming that the methyl formate is spatially distributed as the dust is, we find relative abundances of methyl formate in the range ≤0.1 × 10 −8 to 5.2 × 10 −8 . We suggest a relation between the methyl formate distribution and shocks as traced by 2.12 μm H 2 emission.

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“…This possibility is illustrated well by the comparison of the H 2 2.12 μm map of Lacombe et al (2004) (Fig. 20) with the Subaru deep exposure (Fig.…”

Section: Hcooch 3 and Ir 11 μM Mapmentioning

confidence: 59%

Section: Hcooch 3 and Ir 11 μM Mapmentioning

confidence: 92%

Section: Hcooch 3 and Ir 11 μM Mapmentioning

confidence: 95%

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HCOOCH₃as a probe of temperature and structure in Orion-KL

Favre

Despois

Brouillet

et al. 2011

A&A

100

238

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“…A slower outflow (∼18 km s −1 ) is moving in the NE-SW direction (Genzel et al 1981;Greenhill et al 1998;Nissen et al 2007). The morphology of most of the objects in the slower outflow SW of BN is clearly bow shaped (Stolovy et al 1998;Schultz et al 1999;Gustafsson et al 2003;Lacombe et al 2004;Kristensen et al 2007;Colgan et al 2007). We model one of these bow shocks, which has been observed with the ESO-VLT (Gustafsson 2006).…”

Section: Introductionmentioning

confidence: 90%

3D model of bow shocks

Gustafsson¹,

Ravkilde

Kristensen

et al. 2010

A&A

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Context. Shocks produced by outflows from young stars are often observed as bow-shaped structures in which the H 2 line strength and morphology are characteristic of the physical and chemical environments and the velocity of the impact. Aims. We present a 3D model of interstellar bow shocks propagating in a homogeneous molecular medium with a uniform magnetic field. The model enables us to estimate the shock conditions in observed flows. As an example, we show how the model can reproduce rovibrational H 2 observations of a bow shock in OMC1.Methods. The 3D model is constructed by associating a planar shock with every point on a 3D bow skeleton. The planar shocks are modelled with a highly sophisticated chemical reaction network that is essential for predicting accurate shock widths and line emissions. The shock conditions vary along the bow surface and determine the shock type, the local thickness, and brightness of the bow shell. The motion of the cooling gas parallel to the bow surface is also considered. The bow shock can move at an arbitrary inclination to the magnetic field and to the observer, and we model the projected morphology and radial velocity distribution in the plane-of-sky. Results. The morphology of a bow shock is highly dependent on the orientation of the magnetic field and the inclination of the flow. Bow shocks can appear in many different guises and do not necessarily show a characteristic bow shape. The ratio of the H 2 v = 2−1 S(1) line to the v = 1−0 S(1) line is variable across the flow and the spatial offset between the peaks of the lines may be used to estimate the inclination of the flow. The radial velocity comes to a maximum behind the apparent apex of the bow shock when the flow is seen at an inclination different from face-on. Under certain circumstances the radial velocity of an expanding bow shock can show the same signatures as a rotating flow. In this case a velocity gradient perpendicular to the outflow direction is a projection effect of an expanding bow shock lighting up asymmetrically because of the orientation of the magnetic field. With the 3D model we reproduce the brightness levels in three H 2 lines as well as the shape and size of a chosen bow shock in OMC1. The inferred bow inclination and the orientation and strength of the magnetic field fit into the pattern suggested by independent observations.

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“…The CR (together with mm3a and mm3b) is thought to be the place where icy grains are released into the gas phase by an outflow from the HC (Blake et al 1987;Liu et al 2002). Therefore, based on the reported association between the emissions of HCOOCH 3 and the 2.12 µm vibrationally excited H 2 (Lacombe et al 2004), it has been suggested that shocks between the ISM and high-velocity gas "bullets" from the outflow (Zapata et al 2009;Bally et al 2011) explains the production of COMs, which has the same morphology as HCOOCH 3 (Favre et al 2011b). In a similar scenario, N-bearing COMs may be released to the gas phase north-east of the HC (e.g., HC 3 N, CH 2 CHCN), where the low-velocity outflow is impacting the ambient dusty material, and the weak emission /nondetection of these molecules along the high-velocity outflow may be due to lack of dusty material in the NW-SE direction .…”

Section: Chemistry In the Outflowmentioning

confidence: 99%

Resolving the chemical substructure of Orion-KL

Feng

Beuther

Henning

et al. 2015

A&A

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Context. The Kleinmann-Low nebula in Orion (Orion-KL) is the nearest example of a high-mass star-forming environment. Studying the resolved chemical substructures of this complex region provides important insight into the chemistry of high-mass star-forming regions (HMSFRs), as it relates to their evolutionary states. Aims. The goal of this work is to resolve the molecular line emission from individual substructures of Orion-KL at high spectral and spatial resolution and to infer the chemical properties of the associated gas.Methods. We present a line survey of Orion-KL obtained from combined Submillimeter Array (SMA) interferometric and IRAM 30 m single-dish observations. Covering a 4 GHz bandwidth in total, this survey contains over 160 emission lines from 20 species (25 isotopologues), including 11 complex organic molecules (COMs). Spectra are extracted from individual substructures and the intensity-integrated distribution map for each species is provided. We then estimate the rotation temperature for each substructure, along with their molecular column densities and abundances. Results. For the first time, we complement 1.3 mm interferometric data with single-dish observations of the Orion-KL region and study small-scale chemical variations in this region. (1) We resolve continuum substructures on ∼3 angular scale. (2) We identify lines from the low-abundance COMs CH 3 COCH 3 and CH 3 CH 2 OH, as well as tentatively detect CH 3 CHO and long carbon-chain molecules C 6 H and HC 7 N. (3) We find that while most COMs are segregated by type, peaking either towards the hotcore (e.g., nitrogenbearing species) or the compact ridge (e.g., oxygen-bearing species like HCOOCH 3 and CH 3 OCH 3 ), the distributions of others do not follow this segregated structure (e.g., CH 3 CH 2 OH, CH 3 OH, CH 3 COCH 3 ). (4) We find a second velocity component of HNCO, SO 2 , 34 SO 2 , and SO lines, which may be associated with a strong shock event in the low-velocity outflow. (5) Temperatures and molecular abundances show large gradients between central condensations and the outflow regions, illustrating a transition between hot molecular core and shock-chemistry dominated regimes. Conclusions. Our observations of spatially resolved abundance variations in Orion-KL provide the nearest reference source for hot molecular core and outflow chemistry, which will be an important example for interpreting the chemistry of more distant HMSFRs.

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VLT/NACO infrared adaptive optics images of small scale structures in OMC1

Cited by 21 publications

References 34 publications

HCOOCH₃as a probe of temperature and structure in Orion-KL

HCOOCH₃as a probe of temperature and structure in Orion-KL

3D model of bow shocks

Resolving the chemical substructure of Orion-KL

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VLT/NACO infrared adaptive optics images of small scale structures in OMC1

Cited by 21 publications

References 34 publications

HCOOCH3as a probe of temperature and structure in Orion-KL

HCOOCH3as a probe of temperature and structure in Orion-KL

3D model of bow shocks

Resolving the chemical substructure of Orion-KL

Contact Info

Product

Resources

About

HCOOCH₃as a probe of temperature and structure in Orion-KL

HCOOCH₃as a probe of temperature and structure in Orion-KL