Chemical transitions for interstellar C2 and CN in cloud envelopes

Federman, S. R.; Strom, C.; Lambert, David L.; Cardelli, Jason A.; Smith, Verne V.; Joseph, Charles L.

doi:10.1086/173930

Cited by 116 publications

(197 citation statements)

References 0 publications

Supporting

Mentioning

169

Contrasting

Order By: Relevance

“…These models have been reviewed by ) and van Dishoeck (1991. Observations of other simple molecules such as CH, CH ϩ , C 2 , CO, CN, and OH similarly provide constraints on the chemical models Black, 1988, 1989;Federman et al, 1980Federman et al, , 1984Federman et al, , 1994Danks et al, 1984). Likewise, Turner (see Turner, 1996, and references therein) has developed translucent cloud models in order to understand the basic ion-molecule chemistry of a number of observed molecular species including HCO ϩ , H 2 CO, NH 3 , N 2 H ϩ , SO, SO 2 , CS, H 2 S, SO ϩ , and HCS ϩ .…”

Section: B X-ray Dissociation Regionsmentioning

confidence: 94%

“…It derives rather directly from the chemistry of those more transparent PDRs, diffuse and translucent clouds Langer, 1974, 1976;Black and Dalgarno, 1977;Federman et al 1980Federman et al , 1984Federman et al , 1994Danks et al, 1984;van Dishoeck and Black, 1986, 1988Viala, 1986;Viala et al, 1988;Federman and Huntress, 1989;van Dishoeck, 1991;Heck et al, 1992;Turner, 1996, and references therein) PDR chemistry differs from standard, interstellar, ionmolecule chemistry 8 in a number of ways. Obviously, because of the high far-ultraviolet flux, photoreactions are very important, as are reactions with atomic H. The formation and photodissociation of H 2 is central to PDRs, and we begin with a discussion of H 2 chemistry and H 2 far-ultraviolet-pumped heating.…”

Section: B Chemistry In Pdrsmentioning

confidence: 99%

See 1 more Smart Citation

Photodissociation regions in the interstellar medium of galaxies

Hollenbach

Tielens²

1999

Rev. Mod. Phys.

751

712

View full text Add to dashboard Cite

The interstellar medium of galaxies is the reservoir out of which stars are born and into which stars inject newly created elements as they age. The physical properties of the interstellar medium are governed in part by the radiation emitted by these stars. Far-ultraviolet (6 eVϽh Ͻ13.6 eV) photons from massive stars dominate the heating and influence the chemistry of the neutral atomic gas and much of the molecular gas in galaxies. Predominantly neutral regions of the interstellar medium in which the heating and chemistry are regulated by far ultraviolet photons are termed PhotoDissociation Regions (PDRs). These regions are the origin of most of the non-stellar infrared (IR) and the millimeter and submillimeter CO emission from galaxies. The importance of PDRs has become increasingly apparent with advances in IR and submillimeter astronomy. The IR emission from PDRs includes fine structure lines of C, C ϩ , and O; rovibrational lines of H 2 ; rotational lines of CO; broad mid-IR features of polycyclic aromatic hydrocarbons; and a luminous underlying IR continuum from interstellar dust. The transition of H to H 2 and C ϩ to CO occurs within PDRs. Comparison of observations with theoretical models of PDRs enables one to determine the density and temperature structure, the elemental abundances, the level of ionization, and the radiation field. PDR models have been applied to interstellar clouds near massive stars, planetary nebulae, red giant outflows, photoevaporating planetary disks around newly formed stars, diffuse clouds, the neutral intercloud medium, and molecular clouds in the interstellar radiation field-in summary, much of the interstellar medium in galaxies. Theoretical PDR models explain the observed correlations of the [CII] 158 m with the CO Jϭ1 -0 emission, the CO Jϭ1 -0 luminosity with the interstellar molecular mass, and the [CII] 158 m plus [OI] 63 m luminosity with the IR continuum luminosity. On a more global scale, PDR models predict the existence of two stable neutral phases of the interstellar medium, elucidate the formation and destruction of star-forming molecular clouds, and suggest radiation-induced feedback mechanisms that may regulate star formation rates and the column density of gas through giant molecular clouds. [S0034-6861(99)01001-6] CONTENTS

show abstract

Section: B X-ray Dissociation Regionsmentioning

confidence: 94%

Section: B Chemistry In Pdrsmentioning

confidence: 99%

Photodissociation regions in the interstellar medium of galaxies

Hollenbach

Tielens²

1999

Rev. Mod. Phys.

751

712

View full text Add to dashboard Cite

show abstract

“…The ambient H number density can be estimated either from C i ( * , * * ) (n = 700 cm −3 ; B05) or C 2 absorption lines (n = 300 cm −3 ; Federman et al 1994), assuming the latter are not significantly contaminated by the dense shell. Adopting n = 500 cm −3 , we get a "theoretical" value of R 0 = 3.5×10 −4 pc while observations indicate R 0 0.04 pc, in marked disagreement.…”

Section: B2 Momentum Balance and Ambient Densitymentioning

confidence: 99%

“…This bright star is significantly reddened [E(B − V) = 0.53] and its optical spectrum displays strong absorption lines Article published by EDP Sciences from e.g. CH, CH + , CN (Federman et al 1994), typical of diffuse molecular clouds. HD 34078 has a high proper motion of μ = 43 mas yr −1 , corresponding to a transverse velocity of 103 km s −1 or 22 AU yr −1 for a distance D = 530 pc (this value will be used in the following for consistency with B05; it is compatible with the trigonometric parallax estimate of 446 +220 −111 pc).…”

Section: Introductionmentioning

confidence: 99%

CO emission and variable CH and CH⁺absorption towards HD 34078: evidence for a nascent bow shock?

Boissé¹,

Rollinde

Hily-Blant

et al. 2009

A&A

Self Cite

View full text Add to dashboard Cite

Context. The runaway star HD 34078, initially selected to investigate small scale structure in a foreground diffuse cloud, has been shown to be surrounded by highly excited H 2 , the origin of which is unclear. Aims. We first search for an association between the foreground cloud and HD 34078. Second, we extend previous investigations of temporal absorption line variations (CH, CH + , H 2 ) in order to better characterize them and understand their relation to small-scale structure in the molecular gas. Methods. We have mapped the 12 CO(2-1) emission at 12 resolution around HD 34078's position, using the 30 m IRAM antenna. The follow-up of CH and CH + absorption lines has been extended over 5 more years: 26 visible spectra have been acquired since 2003 at high or intermediate resolution. In parallel, CH absorption towards the reddened star ζ Per has been monitored to check the instrumental stability and homogeneity of our measurements. Three more FUSE spectra have been obtained to search for N(H 2 ) variations. Results. CO observations show a pronounced maximum near HD 34078's position, clearly indicating that the star and diffuse cloud are associated. The optical spectra confirm the reality of strong, rapid and correlated CH and CH + fluctuations (up to 26% for N(CH + ) between 2007 and 2008). On the other hand, N(H 2 , J = 0) has varied by less than 5% over 4 years, indicating the absence of marked density structure at scales below 100 AU. We also discard N(CH) variations towards ζ Per at scales less than 20 AU. Conclusions. Observational constraints from this work and from 24 μm dust emission appear to be consistent with H 2 excitation but inconsistent with steady-state bow shock models and rather suggest that the shell of compressed gas surrounding HD 34078 or lying at the boundary of a small foreground clump is seen at an early stage of the interaction. The CH and CH + time variations as well as their high abundances are likely due to chemical structure in the shocked gas layer located at the stellar wind/ambient cloud interface. Finally, the lack of variation in both N(H 2 , J = 0) towards HD 34078 and N(CH) towards ζ Per suggests that quiescent molecular gas is not subject to pronounced small-scale structure.

show abstract

“…HD 34078 is a 09.5 star extincted by a foreground molecular cloud (E(B -V) -0.52). Many species have already been detected toward this direction: Hi and CO column densities have been measured by Mc Lachlan and Nandy (1984) from an IUE spectrum while CH, CN, C 2 and CH+ have been observed by Federman et al (1994) and Allen(1994).…”

Section: H 2 Toward H D 34078mentioning

confidence: 99%

First Results from the FUSE Mission

Sonneborn¹,

Moos

2002

Highlights astron.

View full text Add to dashboard Cite

Abstract. The Far Ultraviolet Spectroscopic Explorer (FUSE) provides high-resolution spectroscopy at far ultraviolet (FUV) wavelengths (905-1187A) of many astronomical objects in order to address fundamental questions related to the origin of the universe. FUSE, a cooperative project of the United States, Canada, and France, was launched in June 1999 for a three-year primary mission. The instrument sensitivity permits studies of many extragalactic sources at high spectral resolution. The key science drivers for the mission design are absorption-line spectroscopy of the ISM and IGM to investigate D/H, O VI, and molecular hydrogen abundances and distribution in the Galaxy and beyond t o z~ 0.3. Most of the observing time is available to Guest Investigators. This Joint Discussion summarizes some of the scientific results determined primarily from the first several months of FUSE observations.

show abstract

Chemical transitions for interstellar C2 and CN in cloud envelopes

Cited by 116 publications

References 0 publications

Photodissociation regions in the interstellar medium of galaxies

Photodissociation regions in the interstellar medium of galaxies

CO emission and variable CH and CH⁺absorption towards HD 34078: evidence for a nascent bow shock?

First Results from the FUSE Mission

Contact Info

Product

Resources

About

Chemical transitions for interstellar C2 and CN in cloud envelopes

Cited by 116 publications

References 0 publications

Photodissociation regions in the interstellar medium of galaxies

Photodissociation regions in the interstellar medium of galaxies

CO emission and variable CH and CH+absorption towards HD 34078: evidence for a nascent bow shock?

First Results from the FUSE Mission

Contact Info

Product

Resources

About

CO emission and variable CH and CH⁺absorption towards HD 34078: evidence for a nascent bow shock?