N. Koning

A spectral line survey of Orion KL in the bands 486-492 and 541-577 GHz with the Odin satellite - II. Data analysis

Aims. We investigate the physical and chemical conditions in a typical star forming region, including an unbiased search for new molecules in a spectral region previously unobserved. Methods. Due to its proximity, the Orion KL region offers a unique laboratory of molecular astrophysics in a chemically rich, massive star forming region. Several ground-based spectral line surveys have been made, but due to the absorption by water and oxygen, the terrestrial atmosphere is completely opaque at frequencies around 487 and 557 GHz. To cover these frequencies we used the Odin satellite to perform a spectral line survey in the frequency ranges 486−492 GHz and 541−577 GHz, filling the gaps between previous spectral scans. Odin’s high main beam efficiency, ηmb = 0.9, and observations performed outside the atmosphere make our intensity scale very well determined. Results. We observed 280 spectral lines from 38 molecules including isotopologues, and, in addition, 64 unidentified lines. A few U-lines have interesting frequency coincidences such as ND and the anion SH − . The beam-averaged emission is dominated by CO, H2O, SO2 ,S O, 13 CO and CH3OH. Species with the largest number of lines are CH3OH, (CH3)2O, SO2, 13 CH3OH, CH3CN and NO. Six water lines are detected including the ground state rotational transition 11,0–10,1 of o-H2O, its isotopologues o-H 18 Oa nd o-H 17 O, the Hot Core tracing p-H2O transition 62,4–71,7 ,a nd the 2 0,2–11,1 transition of HDO. Other lines of special interest are the 10–0 0 transition of NH3 and its isotopologue 15 NH3. Isotopologue abundance ratios of D/H, 12 C/ 13 C, 32 S/ 34 S, 34 S/ 33 S, and 18 O/ 17 O are estimated. The temperatures, column densities and abundances in the various subregions are estimated, and we find very high gas-phase abundances of H2O, NH3 ,S O 2, SO, NO, and CH3OH. A comparison with the ice inventory of ISO sheds new light on the origin of the abundant gas-phase molecules.

Observations of the Circumstellar Water 110→101 and Ammonia 10→00 Lines in IRC +10216 by the Odin Satellite

Submillimeter lines of H2O and NH3 have been detected in the carbon star IRC +10216 (CW Leo) with the Odin submillimeter satellite. The detection of the J = 110 → 101 557 GHz line of ortho-H2O confirms the earlier detection in the same source with SWAS. The detection of the JK = 10 → 00 572 GHz line represents the first observation of the ground-state rotational transition of NH3 in a stellar envelope. By fitting a molecular line transfer model to the observed lines, we derive an ortho-H2O abundance of 2.4 × 10-6, which is consistent with estimates from the SWAS observation. The derived ortho-NH3 abundance of 1 × 10-6 relative to H2 is significantly higher than those derived from 24 GHz inversion transitions and is slightly higher than those from vibrational transitions in the infrared band. The high H2O and NH3 abundances in the carbon-rich star IRC +10216 underscore shortcomings in the conventional gas-phase LTE and non-LTE chemical models.

HYDRODYNAMICAL VELOCITY FIELDS IN PLANETARY NEBULAE

Based on axisymmetric hydrodynamical simulations and three-dimensional (3D) reconstructions with Shape, we investigate the kinematical signatures of deviations from homologous (Hubble-type) outflows in some typical shapes of planetary nebulae (PNs). We find that, in most situations considered in our simulations, the deviations from a Hubble-type flow are significant and observable. The deviations are systematic and a simple parameterization of them considerably improves morphokinematical models of the simulations. We describe such extensions to a homologous expansion law that capture the global velocity structure of hydrodynamical axisymmetric nebulae during their wind-blown phase. It is the size of the poloidal velocity component that strongly influences the shape of the position-velocity diagrams that are obtained, not so much the variation of the radial component. The deviations increase with the degree of collimation of the nebula and they are stronger at intermediate latitudes. We describe potential deformations which these deviations might produce in 3D reconstructions that assume Hubble-type outflows. The general conclusion is that detailed morphokinematical observations and modeling of PNs can reveal whether a nebula is still in a hydrodynamically active stage (windy phase) or whether it has reached ballistic expansion.

A spectral line survey of Orion KL in the bands 486–492 and 541–577 GHz with the Odin satellite - I. The observational data

Aims. Spectral line surveys are useful since they allow identification of new molecules and new lines in uniformly calibrated data sets. The subsequent multi-transition analysis will provide improved knowledge of molecular abundances, cloud temperatures and densities, and may also reveal previously unsuspected blends of molecular lines, which otherwise may lead to erroneous conclusions. Nonetheless, large portions of the sub-millimetre spectral regime remain unexplored due to severe absorptions by H2 Oa nd O 2 in the terrestrial atmosphere. The purpose of the measurements presented here is to cover wavelength regions at and around 0.55 mm – regions largely unobservable from the ground. Methods. Using the Odin astronomy/aeronomy satellite, we performed the first spectral survey of the Orion KL molecular cloud core in the bands 486–492 and 541–576 GHz with rather uniform sensitivity (22–25 mK baseline noise). Odin’s 1.1 m size telescope, equipped with four cryo-cooled tuneable mixers connected to broad band spectrometers, was used in a satellite position-switching mode. Two mixers simultaneously observed different 1.1 GHz bands using frequency steps of 0.5 GHz (25 h each). An on-source integration time of 20 h was achieved for most bands. The entire campaign consumed ∼1100 orbits, each containing one hour of serviceable astro-observation. Results. We identified 280 spectral lines from 38 known interstellar molecules (including isotopologues) having intensities in the range 80 to 0.05 K. An additional 64 weak lines remain unidentified. Apart from the ground state rotational 11,0–10,1 transitions of ortho-H2O, H 18 Oa nd H 17 O, the high energy 62,4–71,7 line of para-H2 O( Eu = 867 K) and the HDO(20,2–11,1) line have been observed, as well as the 10–01 lines from NH3 and its rare isotopologue 15 NH3. We suggest assignments for some unidentified features, notably the new interstellar molecules ND and SH − . Severe blends have been detected in the line wings of the H 18 O, H 17 Oa nd 13 CO lines changing the true linewidths of the outflow emission.

Post Asymptotic Giant Branch Bipolar Reflection Nebulae: Result of Dynamical Ejection or Selective Illumination?

A model for post asymptotic giant branch bipolar reflection nebulae has been constructed based on a pair of evacuated cavities in a spherical dust envelope. Many of the observed features of bipolar nebulae, including filled bipolar lobes, an equatorial torus, searchlight beams, and a bright central light source, can be reproduced. The effects on orientation and dust densities are studied and comparisons with some observed examples are offered. We suggest that many observed properties of bipolar nebulae are the result of optical effects and any physical modeling of these nebulae has to take these factors into consideration.

SHAPEMOL: a 3D code for calculating CO line emission in planetary and protoplanetary nebulae - Detailed model-fitting of the complex nebula NGC 6302

This work was partially supported by grant “UNAM-PAPIIT 100410 and 101014” and by the Spanish MICINN within the program CONSOLIDER INGENIO 2010, under grant “Molecular Astrophysics: The Herschel and ALMA Era, ASTROMOL” (ref.: CSD2009-00038).

[Fe III] EMISSION LINES IN THE PLANETARY NEBULA NGC 2392

NGC 2392 is a young double-shell planetary nebula (PN). Its intrinsic structure and shaping mechanism are still not fully understood. In this paper we present new spectroscopic observations of NGC 2392. The slits were placed at two different locations to obtain the spectra of the inner and outer regions. Several [Fe III] lines are clearly detected in the inner region. We infer that NGC 2392 might have an intrinsic structure similar to the bipolar nebula Mz 3, which also exhibits a number of [Fe III] lines arising from the central regions. In this scenario, the inner and outer regions of NGC 2392 correspond to the inner lobes and the outer outflows of Mz 3, respectively. We construct a three-dimensional morpho-kinematic model to examine our hypothesis. We also compare the physical conditions and chemical composition of the inner and outer regions, and discuss the implications on the formation of this type of PN.

Organic Molecules in the spectral line survey of Orion KL with the Odin Satellite from 486-492 GHz and 541-577 GHz

A spectral line survey of Orion KL has been performed over the frequency range of 486–492 GHz and 541–577 GHz using the Odin satellite. Over 1000 lines have been identified from 40 different molecular species, including several organic compounds such as methyl cyanide (CH3CN), methanol (CH3OH, 13CH3OH), and dimethyl ether (CH3OCH3).

Evolution of Maser/IR Objects with Very Thick Dust Envelopes

Some stellar maser sources at preplanetary stage have very thick circumstellar envelopes, for which no near-infrared identifications have been made. We investigated such stars at radio/NIR/MIR wavelengths using the NRO 45-m, ANU 2.2-m, UH 2.2-m, and SUBARU 8.2-m telescopes. Furthermore, using the Spitzer/Glimpse survey of the Galactic plane, we found counterparts in the 3.6 micron band for all of the OH/IR objects without previous NIR identification. One of the most interesting objects among these is IRAS 18450–0148 (W43A) with collimated outflows. Their spectra indicate that they have massive thick disks.