AN INTERFEROMETRIC SPECTRAL-LINE SURVEY OF IRC+10216 IN THE 345 GHz BAND

Patel, Nimesh; Gottlieb, C. A.; Thaddeus, P.; Wilson, R. W.; Menten, K. M.; Reid, M. J.; McCarthy, Michael; Cernicharo, J.; He, Jinhong; Brünken, Sandra; Trung, Dinh Van; Keto, Eric

doi:10.1088/0067-0049/193/1/17

Cited by 64 publications

(51 citation statements)

References 39 publications

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“…Fonfría et al (2008) made a sensitive spectral survey in the 11−14 μm range that unveiled a forest of ro-vibrational lines arising from C 2 H 2 and HCN. A recent interferometric spectral survey in the 0.9 mm atmospheric window by Patel et al (2011) allowed to detect a good number of narrow unidentified lines arising from the innermost envelope, inside the acceleration region, that they tentatively assign to molecular rotational transitions within excited vibrational states.…”

Section: Introductionmentioning

confidence: 99%

Molecular abundances in the inner layers of IRC +10216

Agúndez

Fonfría

Cernicharo

et al. 2012

A&A

136

259

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Context. The inner layers of circumstellar envelopes around asymptotic giant branch stars are sites where a variety of processes such as thermochemical equilibrium, shocks induced by the stellar pulsation, and condensation of dust grains determine the chemical composition of the material that is expelled into the outer envelope layers and, ultimately, into interstellar space. Aims. We aim at studying the abundances, throughout the whole circumstellar envelope of the carbon star IRC +10216, of several molecules formed in the inner layers in order to constrain the different processes at work in such regions. Methods. Observations towards IRC +10216 of CS, SiO, SiS, NaCl, KCl, AlCl, AlF, and NaCN have been carried out with the IRAM 30-m telescope in the 80−357.5 GHz frequency range. A large number of rotational transitions covering a wide range of energy levels, including highly excited vibrational states, are detected in emission and serve to trace different regions of the envelope. Radiative transfer calculations based on the LVG formalism have been performed to derive molecular abundances from the innermost out to the outer layers. The excitation calculations include infrared pumping to excited vibrational states and inelastic collisions, for which up-to-date rate coefficients for rotational and, in some cases, ro-vibrational transitions are used. Results. We find that in the inner layers CS, SiO, and SiS have abundances relative to H 2 of 4 × 10 −6 , 1.8 × 10 −7 , and 3 × 10 −6 , respectively, and that CS and SiS have significant lower abundances in the outer envelope, which implies that they actively contribute to the formation of dust. Moreover, in the inner layers, the amount of sulfur and silicon in gas phase molecules is only 27% for S and 5.6% for Si, implying that these elements have already condensed onto grains, most likely in the form of MgS and SiC. Metal-bearing molecules lock up a relatively small fraction of metals, although our results indicate that NaCl, KCl, AlCl, AlF, and NaCN, despite their refractory character, are not significantly depleted in the cold outer layers. In these regions a few percent of the metals Na, K, and Al survive in the gas phase, either in atomic or molecular form, and are therefore available to participate in the gas phase chemistry in the outer envelope.

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Section: Introductionmentioning

confidence: 99%

Molecular abundances in the inner layers of IRC +10216

Agúndez

Fonfría

Cernicharo

et al. 2012

A&A

136

259

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“…IRC+10216, Cernicharo et al 2000;Patel et al 2011), massive star-forming clouds (e.g. Sgr B2, Nummelin et al 2000), or cold molecular clouds (e.g.…”

Section: Introductionmentioning

confidence: 99%

Molecules atz= 0.89

Müller

Beelen

Guèlin

et al. 2011

A&A

164

284

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We present the results of a 7 mm spectral survey of molecular absorption lines originating in the disk of a z = 0.89 spiral galaxy located in front of the quasar PKS 1830−211. Our survey was performed with the Australia Telescope Compact Array and covers the frequency interval 30-50 GHz, corresponding to the rest-frame frequency interval 57-94 GHz. A total of 28 different species, plus 8 isotopic variants, were detected toward the south-west absorption region, located about 2 kpc from the center of the z = 0.89 galaxy, which therefore has the largest number of detected molecular species of any extragalactic object so far. The results of our rotation diagram analysis show that the rotation temperatures are close to the cosmic microwave background temperature of 5.14 K that we expect to measure at z = 0.89, whereas the kinetic temperature is one order of magnitude higher, indicating that the gas is subthermally excited. The molecular fractional abundances are found to be in-between those in typical Galactic diffuse and translucent clouds, and clearly deviate from those observed in the dark cloud TMC 1 or in the Galactic center giant molecular cloud Sgr B2. The isotopic ratios of carbon, nitrogen, oxygen, and silicon deviate significantly from the solar values, which can be linked to the young age of the z = 0.89 galaxy and a release of nucleosynthesis products dominated by massive stars. Toward the north-east absorption region, where the extinction and column density of gas is roughly one order of magnitude lower than toward the SW absorption region, only a handful of molecules are detected. Their relative abundances are comparable to those in Galactic diffuse clouds. We also report the discovery of several new absorption components, with velocities spanning between −300 and +170 km s −1 . Finally, the line centroids of several species (e.g., CH 3 OH, NH 3 ) are found to be significantly offset from the average velocity. If caused by a variation in the proton-to-electron mass ratio μ with redshift, these offsets yield an upper limit | Δμ μ | < 4×10 −6 , which takes into account the kinematical noise produced by the velocity dispersion measured from a large number of molecular species.

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“…Crosas & Menten 1997;Groenewegen et al 1998;Cernicharo et al 2000;De Beck et al 2012) object IRC +10 216, towards which many spectral line surveys have been executed in several different wavelength ranges (e.g. Cernicharo et al 2000Cernicharo et al , 2010He et al 2008;Tenenbaum et al 2010;Patel et al 2011). …”

Section: Introductionmentioning

confidence: 99%

PO and PN in the wind of the oxygen-rich AGB star IK Tauri

Beck

Kamiński

Patel

et al. 2013

A&A

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Context. Phosphorus-bearing compounds have only been studied in the circumstellar environments of the asymptotic giant branch star IRC +10 216 and the protoplanetary nebula CRL 2688, both carbon-rich objects, and the oxygen-rich red supergiant VY CMa. The current chemical models cannot reproduce the high abundances of PO and PN derived from observations of VY CMa. No observations have been reported of phosphorus in the circumstellar envelopes of oxygen-rich asymptotic giant branch stars. Aims. We aim to set observational constraints on the phosphorous chemistry in the circumstellar envelopes of oxygen-rich asymptotic giant branch stars, by focussing on the Mira-type variable star IK Tau. Methods. Using the IRAM 30 m telescope and the Submillimeter Array, we observed four rotational transitions of PN (J = 2−1, 3−2, 6−5, 7−6) and four of PO (J = 5/2−3/2, 7/2−5/2, 13/2−11/2, 15/2−13/2). The IRAM 30 m observations were dedicated line observations, while the Submillimeter Array data come from an unbiased spectral survey in the frequency range 279−355 GHz. Results. We present the first detections of PN and PO in an oxygen-rich asymptotic giant branch star and estimate abundances X(PN/H 2 ) ≈ 3 × 10 −7 and X(PO/H 2 ) in the range 0.5−6.0 × 10 −7 . This is several orders of magnitude higher than what is found for the carbon-rich asymptotic giant branch star IRC +10 216. The diameter ( 0. 7) of the PN and PO emission distributions measured in the interferometric data corresponds to a maximum radial extent of about 40 stellar radii. The abundances and the spatial occurrence of the molecules are in very good agreement with the results reported for VY CMa. We did not detect PS or PH 3 in the survey. Conclusions. We suggest that PN and PO are the main carriers of phosphorus in the gas phase, with abundances possibly up to several 10 −7 . The current chemical models cannot account for this, underlining the strong need for updated chemical models that include phosphorous compounds.

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AN INTERFEROMETRIC SPECTRAL-LINE SURVEY OF IRC+10216 IN THE 345 GHz BAND

Cited by 64 publications

References 39 publications

Molecular abundances in the inner layers of IRC +10216

Molecular abundances in the inner layers of IRC +10216

Molecules atz= 0.89

PO and PN in the wind of the oxygen-rich AGB star IK Tauri

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