Recent astronomy highlights from the Odin satellite

Hjalmarson, Å.; Bergman, P.; Biver, Nicolás; Florén, H. G.; Frisk, U.; Hasegawa, T.; Justtanont, K.; Larsson, Bengt; Lundin, Stefan; Olberg, M.; Olofsson, H.; Persson, G.; Rydbeck, G.; Sandqvist, Aage

doi:10.1016/j.asr.2005.06.014

Cited by 22 publications

(20 citation statements)

References 47 publications

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“…Our 1 0 -0 0 spectrum can also be compared to observations of this transition performed with the Odin satellite (Nordh et al 2003) toward G34 (Hjalmarson et al 2005). Figure 7 shows the comparison.…”

Section: Size Estimatesmentioning

confidence: 96%

On the accretion process in a high-mass star forming region

Hajigholi

Persson

Wirström

et al. 2016

A&A

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Aims. Our aim is to explore the gas dynamics and the accretion process in the early phase of high-mass star formation. Methods. The inward motion of molecular gas in the massive star forming region G34.26+0.15 is investigated by using high-resolution profiles of seven transitions of ammonia at THz frequencies observed with Herschel-HIFI. The shapes and intensities of these lines are interpreted in terms of radiative transfer models of a spherical, collapsing molecular envelope. An accelerated Lambda Iteration (ALI) method is used to compute the models. Results. The seven ammonia lines show mixed absorption and emission with inverse P-Cygni-type profiles that suggest infall onto the central source. A trend toward absorption at increasingly higher velocities for higher excitation transitions is clearly seen in the line profiles. The J = 3 ← 2 lines show only very weak emission, so these absorption profiles can be used directly to analyze the inward motion of the gas. This is the first time a multitransitional study of spectrally resolved rotational ammonia lines has been used for this purpose. Broad emission is, in addition, mixed with the absorption in the 1 0 -0 0 ortho-NH 3 line, possibly tracing a molecular outflow from the star forming region. The best-fitting ALI model reproduces the continuum fluxes and line profiles, but slightly underpredicts the emission and absorption depth in the ground-state ortho line 1 0 -0 0 . An ammonia abundance on the order of 10 −9 relative to H 2 is needed to fit the profiles. The derived ortho-to-para ratio is approximately 0.5 throughout the infalling cloud core similar to recent findings for translucent clouds in sight lines toward W31C and W49N. We find evidence of two gas components moving inwards toward the central region with constant velocities: 2.7 and 5.3 km s −1 , relative to the source systemic velocity. Attempts to model the inward motion with a single gas cloud in free-fall collapse did not succeed.

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Section: Size Estimatesmentioning

confidence: 96%

On the accretion process in a high-mass star forming region

Hajigholi

Persson

Wirström

et al. 2016

A&A

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“…However, the High Velocity Outflow is known to be bi-polar with a FWHP size of 60−70 , as estimated from simultaneous Odin mapping of the H 2 O and CO J = 5−4 brightness distributions Hjalmarson et al 2005). As seen from the radiative transfer equation, the H 2 O excitation temperature corresponding to a size of 70 is only 26 K, while a temperature of 72 K as found by Wright et al (2000) corresponds to a size of only 32 .…”

Section: Discussion -Source Sizes and Source Structurementioning

confidence: 99%

“…1). Using Odin, sensitive observations have been made recently for example towards Orion KL and the Orion Bar , the ρ Oph A core , Sgr B2 (Hjalmarson et al 2005), as well as the molecular cloud S140. The resulting NH 3 abundance in the Orion Bar is 5 × 10 −9 .…”

Section: Hot Core and Compact Ridge Moleculesmentioning

confidence: 99%

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

Persson¹,

Olofsson

Koning

et al. 2007

A&A

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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, η mb = 0.9, and observations performed outside the atmosphere make our intensity scale very well determined.

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“…The column density features discussed are even more pronounced in our first attempts to deconvolve the maps to 40 beam size. Here we have applied a maximum-entropy type deconvolution algorithm using the fact that the Odin beam is an almost circular Gaussian with sidelobes below −30 dB, paired with the strong 13 CO signal (see Hjalmarson et al 2005).…”

Section: Temperaturesmentioning

confidence: 99%

Odin CO and $\mathsf{^{13}}$CO J = 5–4 mapping of Orion KL – a step towards accurate water abundances

Wirström

Bergman

Olofsson

et al. 2006

A&A

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Aims. The very high main beam efficiency (90%) of the telescope on the sub-millimetre wave satellite Odin, in combination with the small calibration errors in the absence of atmospheric attenuation, assures that observed line brightness temperatures are very accurately determined. Based on this, we attempt to determine the column density distribution of H 2 , and the ortho-water abundance, in the Orion KL region. Methods. We have, for the first time, mapped the 12 CO J = 5−4 emission in a 7 × 7 region covering Orion KL, observed simultaneously with a 13 CO J = 5−4 map. Also presented are C 18 O J = 5−4 emission data at four different positions and a C 17 O J = 5−4 emission spectrum detected towards the Orion KL position. The Odin mapping was performed at 1 spacing (beam full width at half maximum 126 at 557 GHz). Results. The CO J = 5−4 narrow line emission from this region mainly arises in the warm, dense gas at the interface (the photondominated region) between the M 42 H ii region and the Orion A molecular cloud, the Orion PDR. The 12 CO and 13 CO J = 5−4 emission maps have been used to determine the column density distribution of H 2 gas across the Orion KL region. The results have been verified by comparing to column densities obtained using the decidedly optically thin C 18 O emission as input to the RADEX radiative transfer code. We find H 2 column densities ranging from 5 × 10 21 cm −2 at map edges to 7× 10 22 cm −2 at the molecular ridge. The mass of the gas in the mapped region is estimated to be 480 M , of which 320 M is situated towards the molecular ridge. We estimate that about half of this mass belongs to the warm Orion PDR interface layer. Finally, based on data from the positions where C 18 O J = 5−4 has been observed, we estimate the ortho-water abundance in the Orion PDR layer to be ≥8 × 10 −8 , higher than previously estimated.

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Recent astronomy highlights from the Odin satellite

Cited by 22 publications

References 47 publications

On the accretion process in a high-mass star forming region

On the accretion process in a high-mass star forming region

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

Odin CO and $\mathsf{^{13}}$CO J = 5–4 mapping of Orion KL – a step towards accurate water abundances

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