Understanding 26Al Emission from Cygnus

Plüschke, S.; Cerviño, M.; Diehl, R.; Kretschmer, Karsten; Hartmann, D. H.; Knödlseder, J.

doi:10.1016/s1387-6473(02)00197-5

Cited by 20 publications

(19 citation statements)

References 11 publications

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“…The cloud might be associated with the Cygnus OB7 complex with a distance of 800 pc (Plüschke et al 2002), consistent with the extinction estimate. Therefore, we adopt a distance of 800 ± 100 pc with a reliability flag of 0.…”

Section: D27 G9204+393supporting

confidence: 87%

Galactic cold cores

Montillaud

Juvela

Rivera-Ingraham

et al. 2015

A&A

160

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Context. For the project Galactic cold cores, Herschel photometric observations were carried out as a follow-up of cold regions of interstellar clouds previously identified with the Planck satellite. The aim of the project is to derive the physical properties of the population of cold sources and to study its connection to ongoing and future star formation. Aims. We build a catalogue of cold sources within the clouds in 116 fields observed with the Herschel PACS and SPIRE instruments. We wish to determine the general physical characteristics of the cold sources and to examine the correlations with their host cloud properties. Methods. From Herschel data, we computed colour temperature and column density maps of the fields. We estimated the distance to the target clouds and provide both uncertainties and reliability flags for the distances. The getsources multiwavelength source extraction algorithm was employed to build a catalogue of several thousand cold sources. Mid-infrared data were used, along with colour and position criteria, to separate starless and protostellar sources. We also propose another classification method based on submillimetre temperature profiles. We analysed the statistical distributions of the physical properties of the source samples. Results. We provide a catalogue of ∼4000 cold sources within or near star forming clouds, most of which are located either in nearby molecular complexes ( 1 kpc) or in star forming regions of the nearby galactic arms (∼2 kpc). About 70% of the sources have a size compatible with an individual core, and 35% of those sources are likely to be gravitationally bound. Significant statistical differences in physical properties are found between starless and protostellar sources, in column density versus dust temperature, mass versus size, and mass versus dust temperature diagrams. The core mass functions are very similar to those previously reported for other regions. On statistical grounds we find that gravitationally bound sources have higher background column densities (median N bg (H 2 ) ∼ 5 × 10 21 cm −2 ) than unbound sources (median N bg (H 2 ) ∼ 3 × 10 21 cm −2 ). These values of N bg (H 2 ) are higher for higher dust temperatures of the external layers of the parent cloud. However, only in a few cases do we find clear N bg (H 2 ) thresholds for the presence of cores. The dust temperatures of cloud external layers show clear variations with galactic location, as may the source temperatures. Conclusions. Our data support a more complex view of star formation than in the simple idea of a column density threshold. They show a clear influence of the surrounding UV-visible radiation on how cores distribute in their host clouds with possible variations on the Galactic scale.

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Section: D27 G9204+393supporting

confidence: 87%

Galactic cold cores

Montillaud

Juvela

Rivera-Ingraham

et al. 2015

A&A

160

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“…This point is essential to the comparison of observed fluxes with the theoretical predictions, because the latter are often mostly based on the clustered stellar content, which is better inventoried than the isolated or non-clustered sources. It is interesting to note here that Plüschke et al (2002) find that the contribution of non-clustered sources may amount to about 20-30%, which tallies with our observational estimate; however, their result was based on an assumed correction of the stellar content of the Cygnus OB associations that has never been observationally substantiated afterward.…”

Section: Discussionsupporting

confidence: 74%

“…Plüschke et al (2000) shows that the discrepancy could be alleviated if one includes the enhanced (but highly uncertain) yields from massive close binary systems in the calculation. Alternatively, Plüschke et al (2002) argues that the problem may well come from underestimating the stellar content of the Cygnus OB associations, because of a strong interstellar extinction, as was proven to be the case for Cyg OB2. In Knödlseder et al (2002), the authors eventually speculate that future stellar models, especially models including the effects of stellar rotation, could solve the dilemma.…”

Section: Introductionmentioning

confidence: 99%

New estimates of the gamma-ray line emission of the Cygnus region from INTEGRAL/SPI observations

Martin

Knödlseder

Diehl

et al. 2009

A&A

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Context. The Cygnus region harbours a huge complex of massive stars at a distance of 1.0-2.0 kpc from us. About 170 O stars are distributed over several OB associations, among which the Cyg OB2 cluster is by far the largest with about 100-120 O stars. As a consequence of their successive nuclear-burning episodes, these massive stars inject large quantities of radioactive nuclei into the interstellar medium such as 26 Al and 60 Fe. The gamma-ray line signal from the latter is a solid tracer of ongoing nucleosynthesis. Aims. We want to compare the decay emission from the Cygnus region with predictions of recently improved stellar models. As a first step, we establish observational constraints upon the gamma-ray line emission from 26 Al and 60 Fe, with particular emphasis placed on separating the emission due to the Cygnus complex from the foreground and background mean Galactic contributions. Methods. We used the high-resolution gamma-ray spectrometer INTEGRAL/SPI to analyse the 26 Al and 60 Fe decay signal from the Cygnus region. The weak gamma-ray line emissions at 1809 and 1173/1332 keV have been characterised in terms of photometry, spectrometry, and source morphology. Results. The 1809 keV emission from Cygnus is centred on the position of the Cyg OB2 cluster and has a typical size of 9 • or more. The total 1809 keV flux from the Cygnus region is (6.0 ± 1.0) × 10 −5 ph cm −2 s −1 , but the flux really attributable to the Cygnus complex reduces to (3.9 ± 1.1) × 10 −5 ph cm −2 s −1 . The 1809 keV line centroid agrees with expectations considering the direction and distance of the Cygnus complex, and the line width is consistent with typical motions of the interstellar medium. No decay emission from 60 Fe has been observed from the Cygnus region and an upper limit of 1.6 × 10 −5 ph cm −2 s −1 was derived. Conclusions. The determination in a coherent way of the gamma-ray line emission of the clustered OB population of the nearby Cygnus complex will allow a more accurate comparison of observations with theoretical expectations based on the most recent stellar models.

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“…Our aim here is simply to gather the nearby clustered stellar population that is very likely responsible for most of the strong 1809 keV emission from Cygnus. In some previous studies (del Rio et al 1996;Plüschke et al 2002), the total 1809 keV flux from the Cygnus region was compared to theoretical predictions based on the clustered stellar content of the Cygnus region supplemented by a few isolated WR stars and SNRs. In our study, we focus both observationally and theoretically on the clustered stellar content alone, because the clustered population is likely to be better inventoried than the isolated or non-clustered population.…”

Section: The Stellar Content Of the Cygnus Complexmentioning

confidence: 99%

Predicted gamma-ray line emission from the Cygnus complex

Martin

Knödlseder

Meynet

et al. 2010

A&A

116

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Context. The Cygnus region harbours a huge complex of massive stars at a distance of 1.0-2.0 kpc from us. About 170 O stars are distributed over several OB associations, among which the Cyg OB2 cluster is by far the most important with about 100-120 O stars. These massive stars inject large quantities of radioactive nuclei into the interstellar medium, such as 26 Al and 60 Fe, and their gammaray line decay signals can provide insight into the physics of massive stars and core-collapse supernovae. Aims. Past studies of the nucleosynthesis activity of Cygnus have concluded that the level of 26 Al decay emission as deduced from CGRO/COMPTEL observations was a factor 2-3 above the predictions based on the theoretical yields available at that time and on the observed stellar content of the Cygnus region. We reevaluate the situation from new measurements of the gamma-ray decay fluxes with INTEGRAL/SPI (presented in a previous paper) and new predictions based on recently improved stellar models. Methods. We built a grid of nucleosynthesis yields from recent models of massive stars. Compared to previous works, our data include some of the effects of stellar rotation for the higher mass stars and a coherent estimate of the contribution from SNIb/c. We then developed a population synthesis code to predict the nucleosynthesis activity and corresponding decay fluxes of a given stellar population of massive stars. Results. The observed decay fluxes from the Cygnus complex are found to be consistent with the values predicted by population synthesis at solar metallicity; and yet, when extrapolated to the possible subsolar metallicity of the Cygnus complex, our predictions fail to account for the INTEGRAL/SPI measurements. The observed extent of the 1809 keV emission from Cygnus is found to be consistent with the result of a numerical simulation of the diffusion of 26 Al inside the superbubble blown by Cyg OB2. Conclusions. Our work indicates that the past dilemma regarding the gamma-ray line emission from Cygnus resulted from an overestimate of the 1809 keV flux of the Cygnus complex, combined with an underestimate of the nucleosynthesis yields. Our results illustrate the importance of stellar rotation and SNIb/c in the nucleosynthesis of 26 Al and 60 Fe. The effects of binarity and metallicity may also be necessary to account for the observations satisfactorily.

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Understanding 26Al Emission from Cygnus

Cited by 20 publications

References 11 publications

Galactic cold cores

Galactic cold cores

New estimates of the gamma-ray line emission of the Cygnus region from INTEGRAL/SPI observations

Predicted gamma-ray line emission from the Cygnus complex

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