Millimeter- and submillimeter-wave spectrum of C17O. Rotational hyperfine structure analyzed using the Lamb-dip technique

Cazzoli, G.; Dore, Luca; Puzzarini, Cristina; Beninati, Sabina

doi:10.1039/b203245g

Cited by 53 publications

(39 citation statements)

References 15 publications

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“…A detailed description of the spectrometer is given in Ref. [21], whereas our experimental set up for performing sub-Doppler resolution spectroscopy has been described in some previous papers [22][23][24][25]. Therefore, here, we only report the main details related to the present investigation.…”

Section: Methodsmentioning

confidence: 97%

The hyperfine structure in the rotational spectra of bromofluoromethane: Lamb-dip technique and quantum-chemical calculations

et al. 2008

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Section: Methodsmentioning

confidence: 97%

The hyperfine structure in the rotational spectra of bromofluoromethane: Lamb-dip technique and quantum-chemical calculations

et al. 2008

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“…comm., (2) Müller et al (2001), (3) Cazzoli et al (2002), (4) Gottlieb et al (2003), (5) Kukolich (1967), (6) Lee et al (2001), astronomical, (7) Caselli et al (2002c), astronomical. N 2 H + (3-2) observations were carried out in 2001 April. All data were taken in frequency switching mode with frequency throws of approximately 7 or 14 MHz.…”

Section: Observationsmentioning

confidence: 99%

On the internal structure of starless cores

Tafalla

Myers

Caselli

et al. 2004

A&A

430

561

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Abstract.We have characterized the physical structure and chemical composition of two close-to-round starless cores in Taurus-Auriga, L1498 and L1517B. Our analysis is based on high angular resolution observations in at least two transitions of NH 3 , N 2 H + , CS, C 34 S, C 18 O, and C 17 O, together with maps of the 1.2 mm continuum. For both cores, we derive radial profiles of constant temperature and constant turbulence, together with density distributions close to those of non-singular isothermal spheres. Using these physical conditions and a Monte Carlo radiative transfer model, we derive abundance profiles for all species and model the strong chemical differentiation of the core interiors. According to our models, the NH 3 abundance increases toward the core centers by a factor of several (≈5) while N 2 H + has a constant abundance over most of the cores. In contrast, both C 18 O and CS (and isotopomers) are strongly depleted in the core interiors, most likely due to their freeze out onto grains at densities of a few 10 4 cm −3 . Concerning the kinematics of the dense gas, we find (in addition to constant turbulence) a pattern of internal motions at the level of 0.1 km s −1 . These motions seem correlated with asymmetries in the pattern of molecular depletion, and we interpret them as residuals of core contraction. Their distribution and size suggest that core formation occurs in a rather irregular manner and with a time scale of a Myr. A comparison of our derived core properties with those predicted by supersonic turbulence models of core formation shows that our Taurus cores are much more quiescent than representative predictions from these models. In two appendices at the end of the paper we present a simple and accurate approximation to the density profile of an isothermal (Bonnor-Ebert) sphere, and a Monte Carlo-calibrated method to derive gas kinetic temperatures using NH 3 data.

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“…For this reason, we used the most recent laboratory estimates for C 18 O(J = 1−0) (109782.176 MHz, see Cazzoli et al 2003) and for C 17 O(J = 1−0) (112358.990 MHz for the brightest, J F = 1 7/2-0 5/2 component, see Cazzoli et al 2002), which have 1 kHz or better accuracy. For N 2 H + and SO, no accurate laboratory measurements are available, so we used astronomical estimates.…”

Section: Observationsmentioning

confidence: 99%

Dense core formation by fragmentation of velocity-coherent filaments in L1517

Hacar

Tafalla

2011

A&A

194

237

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Context. Low-mass star-forming cores differ from their surrounding molecular cloud in turbulence, shape, and density structure. Aims. We aim to understand how dense cores form out of the less dense cloud material by studying the connection between these two regimes. Methods. We observed the L1517 dark cloud in C 18 O(1-0), N 2 H + (J = 1−0), and SO(J N = 3 2 −2 1 ) with the FCRAO 14 m telescope, and in the 1.2 mm dust continuum with the IRAM 30 m telescope. Results. Most of the gas in the cloud lies in four filaments that have typical lengths of 0.5 pc. Five starless cores are embedded in these filaments and have chemical compositions indicative of different evolutionary stages. The filaments have radial profiles of C 18 O(1−0) emission with a central flattened region and a power-law tail, and can be fitted approximately as isothermal, pressure-supported cylinders. The filaments, in addition, are extremely quiescent. They have subsonic internal motions and are coherent in velocity over their whole length. The large-scale motions in the filaments can be used to predict the velocity inside the cores, indicating that core formation has not decoupled the dense gas kinematically from its parental material. In two filaments, these large-scale motions consist of oscillations in the velocity centroid, and a simple kinematic model suggests that they may be related to core-forming flows. Conclusions. Core formation in L1517 seems to have occurred in two steps. First, the subsonic, velocity-coherent filaments have condensed out of the more turbulent ambient cloud. Then, the cores fragmented quasi-statically and inherited the kinematics of the filaments. Turbulence dissipation has therefore occurred mostly on scales on the order of 0.5 pc or larger, and seems to have played a small role in the formation of the individual cores.

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Millimeter- and submillimeter-wave spectrum of C17O. Rotational hyperfine structure analyzed using the Lamb-dip technique

Cited by 53 publications

References 15 publications

The hyperfine structure in the rotational spectra of bromofluoromethane: Lamb-dip technique and quantum-chemical calculations

The hyperfine structure in the rotational spectra of bromofluoromethane: Lamb-dip technique and quantum-chemical calculations

On the internal structure of starless cores

Dense core formation by fragmentation of velocity-coherent filaments in L1517

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