The Translucent Molecular Clouds toward HD 154368. I. Extinction, Abundances, and Depletions

Snow, Theodore P.; Black, J. H.; Dishoeck, E. F. van; Burks, G. S.; Crutcher, R. M.; Lutz, B. L.; Hanson, M. M.; Shuping, R. Y.

doi:10.1086/177416

Cited by 36 publications

(30 citation statements)

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“…The PDR model is for a density of 10 5 cm −3 and radiation field ∼650-900 times the average interstellar value (Jansen et al 1995): J95. The observational results derived from our ISO measurements are shown as well as previous results from Lyu et al (2001) and Hollis et al (1995) Lyu et al (2001) with a hydrogen column density from Snow et al (1996). derive X(CH 2 ) ≈ 4 × 10 −9 and 7 × 10 −10 , respectively, carefully considering beam-filling factors.…”

Section: Comparison With Modelssupporting

confidence: 78%

“…Using the results of Lyu et al (2001) with hydrogen abundances for their lines of sight (see van Dishoeck & Black 1986;Snow et al 1996), we calculate value consistent with our line of sight values and the diffuse cloud model listed in Table 4. For the high densities and temperatures prevailing in the Orion-KL and W51 M hot cores, Hollis et al (1995) Lee et al (1996): L96 and the gas-grain model of Ruffle & Herbst (2001): RH01 including photochemistry (P1/A at 10 8 yr).…”

Section: Comparison With Modelssupporting

confidence: 62%

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Far-infrared detection of methylene

Polehampton¹,

Menten²,

Brünken

et al. 2005

A&A

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Abstract. We present a clear detection of CH 2 in absorption towards the molecular cloud complexes Sagittarius B2 and W49 N using the ISO Long Wavelength Spectrometer. These observations represent the first detection of its low excitation rotational lines in the interstellar medium. Towards Sagittarius B2, we detect both ortho and para transitions allowing a determination of the total CH 2 column density of N(CH 2 ) = (7.5± 1.1)× 10 14 cm −2 . We compare this with the related molecule, CH, to determine [CH/CH 2 ] = 2.7±0.5. Comparison with chemical models shows that the CH abundance along the line of sight is consistent with diffuse cloud conditions and that the high [CH/CH 2 ] ratio can be explained by including the effect of grain-surface reactions.

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Section: Comparison With Modelssupporting

confidence: 78%

Section: Comparison With Modelssupporting

confidence: 62%

Far-infrared detection of methylene

Polehampton¹,

Menten²,

Brünken

et al. 2005

A&A

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“…The spectroscopic distance estimate is 800 pc (Snow et al 1996). The Hipparcos parallax measurement allows an uncertain distance estimate of 370 pc.…”

Section: Hd 154368mentioning

confidence: 92%

The origin of massive O-type field stars

Wit¹,

Testi²,

Palla³

et al. 2004

A&A

110

136

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Abstract. We present a study aimed at clarifying the birthplace for 43 massive O-type field stars. In this first paper we present the observational part: a search for stellar clusters near the target stars. We derive stellar density maps at two different resolving scales, viz. ∼0.25 pc and ∼1.0 pc from NTT and TNG imaging and the 2MASS catalogue. These scales are typical for cluster sizes. The main result is that the large majority of the O-type field population are isolated stars: only 12% (5 out of 43) of the O-type field stars is found to harbour a small-scale stellar cluster. We review the literature and aim at characterizing the stellar field of each O-type field star with the emphasis on star formation and the presence of known young stellar clusters. An analysis of the result of this paper and a discussion of the O-type field population as products of a dynamical ejection event is presented in an accompanying paper.

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“…References.-(1) Bohlin et al 1978; (2) Zsargó et al 1997;(16) Shull & van Steenberg 1985;(17) Rachford et al 2002;(18) Snow et al 1996;(19) Gry et al 2002;(20) Sonnentrucker et al 2002;(21) Jenkins & Tripp 2001;(22) Diplas & Savage 1994;(23) Howk et al 1999;(24) Snow et al 1998;(25) Fitzpatrick & Massa 1990;(26) Sonnentrucker et al 2003;(27) Boissé et al 2005Boissé et al . et al (1999 adopted an average rate that was independent of temperature.…”

Section: H 2 Formationmentioning

confidence: 99%

Chemical Rates on Small Grains and PAHs: C⁺Recombination and H₂Formation

Wolfire

Tielens

Hollenbach

et al. 2008

ApJ

104

135

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We use observations of the C i, C ii, H i, and H 2 column densities along lines of sight in the Galactic plane to determine the formation rate of H 2 on grains and to determine chemical reaction rates with polycyclic aromatic hydrocarbons (PAHs). Photodissociation region models are used to find the best-fit parameters to the observed columns. We find the H 2 formation rate on grains has a low rate (R $ 1 ; 10 À17 cm 3 s À1 ) along lines of sight with low column density (A V P 0:25) and low molecular fraction ( f H 2 P 10 À4 ). At higher column densities (0:25 A V 2:13), we find a rate of R $ 3:5 ; 10 À17 cm 3 s À1 . The lower rate at low column densities could be the result of grain processing by interstellar shocks, which may deplete the grain surface area or process the sites of H þ H formation, thereby inhibiting H 2 production. Alternatively, the formation rate may be normal, and the low molecular fraction may be the result of lines of sight that graze larger clouds. Such lines of sight would have a reduced H 2 self-shielding compared to the lineof-sight column. We find the reaction C þ þ PAH À ! C þ PAH 0 is best fit with a rate 2:4 ; 10 À7 È PAH T À0:5 2 cm 3 s À1 with T 2 ¼ T /100 K, and the reaction C þ þ PAH 0 ! C þ PAH þ is best fit with a rate 8:8 ; 10 À9 È PAH cm 3 s À1 . In high-column-density gas, we find È PAH $ 0:4. In low-column-density gas, È PAH is less well constrained, with È PAH $ 0:2Y0:4.

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The Translucent Molecular Clouds toward HD 154368. I. Extinction, Abundances, and Depletions

Cited by 36 publications

References 0 publications

Far-infrared detection of methylene

Far-infrared detection of methylene

The origin of massive O-type field stars

Chemical Rates on Small Grains and PAHs: C⁺Recombination and H₂Formation

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The Translucent Molecular Clouds toward HD 154368. I. Extinction, Abundances, and Depletions

Cited by 36 publications

References 0 publications

Far-infrared detection of methylene

Far-infrared detection of methylene

The origin of massive O-type field stars

Chemical Rates on Small Grains and PAHs: C+Recombination and H2Formation

Contact Info

Product

Resources

About

Chemical Rates on Small Grains and PAHs: C⁺Recombination and H₂Formation