The EDIBLES survey

Bacalla, Xavier; Linnartz, H.; Cox, Nicholas; Cami, J.; Roueff, E.; Smoker, J. V.; Farhang, Amin; Bouwman, Jordy; Zhao, Dongfeng

doi:10.1051/0004-6361/201833039

Cited by 34 publications

(32 citation statements)

References 62 publications

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“…Densities of up to ∼ 10 7 cm −3 have been reported (Keto & Caselli 2010;Caselli et al 2019), while the actual peak density in contracting cores is expected to reach much higher values before a protostar forms. The magnitude of the CR ionization rate ζ ion measured in the outer envelopes of molecular clouds (in a range of the gas column densie-mail: ivlev@mpe.mpg.de e-mail: ksilsbee@mpe.mpg.de ties around N ∼ 10 21 cm −2 ) varies significantly from one object to another (Indriolo & McCall 2012;Neufeld & Wolfire 2017;Bacalla et al 2019). Given uncertainties in the leading transport regime(s) governing the CR penetration into the clouds (Ivlev et al 2018;Silsbee & Ivlev 2019), this introduces significant uncertainty in the value of ζ ion near the center; available theories (Padovani et al 2018b) predict ζ ion ∼ 10 −17 − 10 −16 s −1 for N ∼ 10 23 cm −2 .…”

Section: Introductionmentioning

confidence: 99%

Gas and Dust Temperature in Prestellar Cores Revisited: New Limits on Cosmic-Ray Ionization Rate

Ivlev

Silsbee

Sipilä

et al. 2019

ApJ

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We develop a self-consistent model for the equilibrium gas temperature and size-dependent dust temperature in cold, dense pre-stellar cores, assuming an arbitrary power-law size distribution of dust grains. Compact analytical expressions applicable to a broad range of physical parameters are derived and compared with predictions of the commonly used standard model. It is suggested that combining the theoretical results with observations should allow us to constrain the degree of dust evolution and the cosmic-ray ionization rate in dense cores, and to help in discriminating between different regimes of cosmic-ray transport in molecular clouds. In particular, assuming a canonical MRN distribution of grain sizes, our theory demonstrates that the gas temperature measurements in the pre-stellar core L1544 are consistent with an ionization rate as high as ∼ 10 −16 s −1 , an order of magnitude higher than previously thought.

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Section: Introductionmentioning

confidence: 99%

Gas and Dust Temperature in Prestellar Cores Revisited: New Limits on Cosmic-Ray Ionization Rate

Ivlev

Silsbee

Sipilä

et al. 2019

ApJ

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“…We need to understand the mechanisms controlling cosmic-ray penetration into the clouds better in order to explain our observations. Previous studies suggested that the cosmic-ray ionisation rate of molecular clouds in the Galaxy is at the magnitude of 10 −16 s −1 (Indriolo & McCall 2012;Indriolo et al 2015;Bacalla et al 2019). ζ CR can reach a higher value (∼10 −14 s −1 ) in regions close to supernovae remnants (e.g.…”

Section: Ionsmentioning

confidence: 98%

Chemical exploration of Galactic cold cores

Zhou

Vastel

Montillaud

et al. 2022

A&A

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Context. A solar-type system starts from an initial molecular core that acquires organic complexity as it evolves. The so-called prestellar cores that can be studied are rare, which has hampered our understanding of how organic chemistry sets in and grows. Aims. We selected the best prestellar core targets from the cold core catalogue (based on Planck and Herschel observations) that represent a diversity in terms of their environment to explore their chemical complexity: 1390 (in the compressed shell of Lambda Ori), 869 (in the MBM12 cloud), and 4149 (in the California nebula). Methods. We obtained a spectral survey with the IRAM 30 m telescope in order to explore the molecular complexity of the cores. We carried out a radiative transfer analysis of the detected transitions in order to place some constraints on the physical conditions of the cores and on the molecular column densities. We also used the molecular ions in the survey to estimate the cosmic-ray ionisation rate and the S/H initial elemental abundance using a gas-phase chemical model to reproduce their abundances. Results. We found large differences in the molecular complexity (deuteration, complex organic molecules, sulphur, carbon chains, and ions) and compared their chemical properties with a cold core and two prestellar cores. The chemical diversity we found in the three cores seems to be correlated with their chemical evolution: two of them are prestellar (1390 and 4149), and one is in an earlier stage (869). Conclusions. The influence of the environment is likely limited because cold cores are strongly shielded from their surroundings. The high extinction prevents interstellar UV radiation from penetrating deeply into the cores. Higher spatial resolution observations of the cores are therefore needed to constrain the physical structure of the cores, as well as a larger-scale distribution of molecular ions to understand the influence of the environment on their molecular complexity.

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“…Estimates for the cosmic-ray ionization rate (ζ p ) in relatively low-density, predominantly atomic gas may be obtained from observations of OH + (e.g., Hollenbach et al 2012;Porras et al 2014;Bacalla et al 2019). The simple chemical model described by Porras et al, for example, which balances the most significant production and destruction processes, leads to ζ p ∼ 1.3 × 10 −10 n H N m (OH + )/N m (H).…”

Section: Cn Excitationmentioning

confidence: 99%

“…4.1.2), and assuming T = 80 K there (as in Porras et al), then that relationship between ζ p and the OH + abundance yields ζ p < 5.6 × 10 −17 s −1 . Inclusion of the effects of polycyclic aromatic hydrocarbons (PAHs) on the ionization (Hollenbach et al 2012;Bacalla et al 2019) then would imply ζ p < 1.9-2.8 × 10 −16 s −1 . These limits fall within the range of ionization rates (from several references) tabulated by Bacalla et al (2019) (all adjusted for the f value for the OH + λ3583.8 line from Hodges et al (2018)).…”

Section: Cn Excitationmentioning

confidence: 99%

HD 62542: Probing the Bare, Dense Core of a Translucent Interstellar Cloud

Welty,

Sonnentrucker,

Snow

et al. 2020

Preprint

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We discuss the interstellar absorption from many atomic and molecular species seen in high-resolution HST/STIS UV and high-S/N optical spectra of the moderately reddened B3-5 V star HD 62542. This remarkable sight line exhibits both very steep far-UV extinction and a high fraction of hydrogen in molecular form -with strong absorption from CH, C 2 , CN, and CO, but weak absorption from CH + and most of the commonly observed diffuse interstellar bands. Most of the material resides in a single narrow velocity component -offering a rare opportunity to probe the primarily molecular core of a single interstellar cloud with little associated diffuse atomic gas. Detailed analyses of the spectra indicate that (1) the molecular fraction in the main cloud is high [f (H 2 ) 0.8];(2) the gas is fairly cold (T k = 40-43 K; from the rotational excitation of H 2 and C 2 ); (3) the local hydrogen density n H ∼ 1500 cm −3 (from the C 2 excitation, the fine-structure excitation of C 0 , and simple chemical models); (4) the unusually high excitation temperatures for 12 CO and 13 CO may be largely due to radiative excitation;(5) N (C + ):N (CO):N (C) ∼ 100:10:1; (6) the depletions of many elements are more severe than those seen in any other sight line, and the detailed pattern of depletions differs from those derived from larger samples of Galactic sight lines; and (7) the various neutral/first ion ratios do not yield consistent estimates for the electron density, even when the effects of grain-assisted recombination and low-temperature dielectronic recombination are considered.

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The EDIBLES survey

Cited by 34 publications

References 62 publications

Gas and Dust Temperature in Prestellar Cores Revisited: New Limits on Cosmic-Ray Ionization Rate

Gas and Dust Temperature in Prestellar Cores Revisited: New Limits on Cosmic-Ray Ionization Rate

Chemical exploration of Galactic cold cores

HD 62542: Probing the Bare, Dense Core of a Translucent Interstellar Cloud

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