Hubble Space TelescopeSurvey of Interstellar12CO/13CO in the Solar Neighborhood

Sheffer, Yaron; Rogers, M.; Federman, S. R.; Lambert, David L.; Gredel, R.

doi:10.1086/520875

Cited by 66 publications

(105 citation statements)

References 69 publications

(158 reference statements)

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“…The term in the denominator corrects from visual to FUV extinction. Note, that the elemental abundances of carbon show an elemental ratio (ER) of 67, close to the average ratio in the local ISM (Sheffer et al 2007). We computed 168 models.…”

Section: Model Parameter Gridmentioning

confidence: 55%

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Carbon fractionation in photo-dissociation regions

Röllig

Ossenkopf

2013

A&A

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We upgraded the chemical network from the UMIST Database for Astrochemistry 2006 to include isotopes such as 13 C and 18 O. This includes all corresponding isotopologues, their chemical reactions and the properly scaled reaction rate coefficients. We study the fractionation behavior of astrochemically relevant species over a wide range of model parameters, relevant for modelling of photo-dissociation regions (PDRs). We separately analyze the fractionation of the local abundances, fractionation of the total column densities, and fractionation visible in the emission line ratios. We find that strong C + fractionation is possible in cool C + gas. Optical thickness as well as excitation effects produce intensity ratios between 40 and 400. The fractionation of CO in PDRs is significantly different from the diffuse interstellar medium. PDR model results never show a fractionation ratio of the CO column density larger than the elemental ratio. Isotope-selective photo-dissociation is always dominated by the isotope-selective chemistry in dense PDR gas. The fractionation of C, CH, CH + and HCO + is studied in detail, showing that the fractionation of C, CH and CH + is dominated by the fractionation of their parental species. The light hydrides chemically derive from C + , and, consequently, their fractionation state is coupled to that of C + . The fractionation of C is a mixed case depending on whether formation from CO or HCO + dominates. Ratios of the emission lines of [C ii], [C i], 13 CO, and H 13 CO + provide individual diagnostics to the fractionation status of C + , C, and CO.

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Section: Model Parameter Gridmentioning

confidence: 55%

“…Liszt (2007) to decline for higher column densities and a total CO column densities of a few 10 16 cm −2 from Galactic CO absorption and emission at 1.3 and 2.1 mm wavelengths for clouds with a total CO column density N(CO) ≤ 10 16 cm −2 . Sheffer et al (2007) showed, that UV data toward diffuse/translucent lines of sight can give 0.5…”

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confidence: 99%

Carbon fractionation in photo-dissociation regions

Röllig

Ossenkopf

2013

A&A

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“…Approximating again the partition function by Q(T ) ∼ kt/(hB) (Sect. 3.1.1) we have Q(163K) ≈ 62 and Q(103K) ≈ 39, and using the 12 CO to 13 CO isotopologic ratio of 69 (e.g., Sheffer et al 2007), the derived total CO column densities toward source n are ≈4.3 × 10 18 cm −2 and ≈6.7 × 10 18 cm −2 , of the same order as for the BN object. With the CO-to-H 2 conversion factor of 8 × 10 −5 , the corresponding H 2 column densities are 5.3 × 10 22 cm −2 and 8.4 × 10 22 cm −2 .…”

Section: Source N 321 Co Absorption and Emissionmentioning

confidence: 70%

Disk and outflow signatures in Orion-KL: the power of high-resolution thermal infrared spectroscopy

Beuther¹,

Linz²,

Bik³

et al. 2010

A&A

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Context. The Orion-KL region contains the closest examples of high-mass accretion disk candidates. Studying their properties is an essential step in studying high-mass star formation. Aims. Resolving the molecular line emission at high spatial and spectral resolution in the immediate environment of the exciting sources to infer the physical properties of the associated gas. Methods. We used the CRIRES high-resolution spectrograph mounted on the VLT to study the ro-vibrational 12 CO, 13 CO, the Pfund β, and H 2 emission between 4.59 and 4.72 μm wavelengths toward the BN object, the disk candidate source n, and a proposed dust density enhancement IRC3. Results. We detected CO absorption and emission features toward all three targets. Toward the BN object, the data partly confirm the results obtained more than 25 years ago; however, we also identify several new features. While the blue-shifted absorption is likely caused by outflowing gas, toward the BN object we detect CO in emission extending in diameter to ∼3300 AU with a velocity structure close to the v lsr . Although at the observational spectral resolution limit, the 13 CO line width of that feature increases with energy levels, consistent with a disk origin. If one also attributes the extended CO emission to a disk origin, its extent is consistent with other massive disk candidates in the literature. For source n, we also find the blueshifted CO absorption likely from an outflow. However, it also exhibits a narrower range of redshifted CO absorption and adjacent weak CO emission, consistent with infalling motions. We do not spatially resolve the emission for source n. For both sources we conduct a Boltzmann analysis of the 13 CO absorption features and find temperatures between 100 and 160 K, and H 2 column densities of a few times 10 23 cm −2 . The observational signatures from IRC3 are very different with only weak absorption against a much weaker continuum source. However, the CO emission is extended and shows wedge-like position velocity signatures consistent with jet-entrainment of molecular gas, potentially associated with the Orion-KL outflow system. We also present and discuss the Pfund β and H 2 emission in the region. Conclusions. This analysis toward the closest high-mass disk candidates outlines the power of high spectral and spatial resolution mid-infrared spectroscopy for studying the gas properties close to young massive stars. We will extend qualitatively similar studies to larger samples of high-mass young stellar objects to constrain the physical properties of the dense innermost gas structures in more detail and in a statistical sense.

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“…12 CO and 13 CO need similar amounts of self-shielding to survive in a hostile interstellar environment. This favors the more abundant isotopologue (e.g., Sheffer et al 2007). For the Galaxy, such effects can be quantified.…”

Section: Chemical Fractionation and Isotope Selective Photodissociationmentioning

confidence: 99%

Weak¹³CO in the Cloverleaf quasar: evidence for a young, early generation starburst

Henkel¹,

Downes

Weiß³

et al. 2010

A&A

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Observations of 12 CO at high redshift indicate rapid metal enrichment in the nuclear regions of at least some galaxies in the early universe. However, the enrichment may be limited to nuclei that are synthesized by short-lived massive stars, excluding classical "secondary" nuclei like 13 C. Testing this idea, we used the IRAM Interferometer to tentatively detect the 13 CO J = 3 → 2 line at a level of 0.3 Jy km s −1 toward the Cloverleaf quasar at z = 2.5. This is the first observational evidence for 13 C at high redshift. The 12 CO/ 13 CO J = 3 → 2 luminosity ratio is with 40 +25 −8 much higher than ratios observed in molecular clouds of the Milky Way and in the ultraluminous galaxy Arp 220, but may be similar to that observed toward NGC 6240. Large Velocity Gradient models simulating seven 12 CO transitions and the 13 CO line yield 12 CO/ 13 CO abundance ratios in excess of 100. It is possible that the measured ratio is affected by a strong submillimeter radiation field, which reduces the contrast between the 13 CO line and the background. It is more likely, however, that the ratio is caused by a real deficiency of 13 CO. This is already apparent in local ultraluminous galaxies and may be even more severe in the Cloverleaf because of its young age ( < ∼ 2.5 Gyr). A potential conflict with optical data, indicating high abundances also for secondary nuclei in quasars of high redshift, may be settled if the bulk of the CO emission is originating sufficiently far from the active galactic nucleus of the Cloverleaf.

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Hubble Space TelescopeSurvey of Interstellar¹²CO/¹³CO in the Solar Neighborhood

Cited by 66 publications

References 69 publications

Carbon fractionation in photo-dissociation regions

Carbon fractionation in photo-dissociation regions

Disk and outflow signatures in Orion-KL: the power of high-resolution thermal infrared spectroscopy

Weak¹³CO in the Cloverleaf quasar: evidence for a young, early generation starburst

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Hubble Space TelescopeSurvey of Interstellar12CO/13CO in the Solar Neighborhood

Cited by 66 publications

References 69 publications

Carbon fractionation in photo-dissociation regions

Carbon fractionation in photo-dissociation regions

Disk and outflow signatures in Orion-KL: the power of high-resolution thermal infrared spectroscopy

Weak13CO in the Cloverleaf quasar: evidence for a young, early generation starburst

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Product

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Hubble Space TelescopeSurvey of Interstellar¹²CO/¹³CO in the Solar Neighborhood

Weak¹³CO in the Cloverleaf quasar: evidence for a young, early generation starburst