The EDIBLES Survey. VII. A survey of C2 and C3 in interstellar clouds

Abstract

We carried out a sensitive survey of C${}_2$ and C${}_3$ using the EDIBLES data set. We also expanded our searches to C${}_4$, C${}_5$, and ${}^{13}$C${}^{12}$C isotopologue in the most molecule-rich sightlines. We fit synthetic spectra generated following a physical excitation model to the C${}_2$ (2-0) Phillips band to obtain the C${}_2$ column density ($N$) as well as the kinetic temperature ($T_{\text{kin}}$) and number density ($n$) of the host cloud. The C${}_3$ molecule was measured through its $\tilde{A}-\tilde{X}$ (000-000) electronic origin band system. We simulated the excitation of this band with a double-temperature Boltzmann distribution. We present the largest combined survey of C${}_2$ and C${}_3$ to date in which the individual transitions can be resolved. In total we detected C${}_2$ in 51 velocity components along 40 sightlines, and C${}_3$ in 31 velocity components along 27 sightlines. The two molecules are detected in the same velocity components. We find a very good correlation between $N$(C${}_2$) and $N$(C${}_3$) with Pearson $r=0.93$ and an average $N$(C${}_2$)/$N$(C${}_3$) ratio of 15.5$\pm$1.4. A comparison with the behaviour of the C${}_2$ DIBs shows that there are no clear differences among sightlines with and without detection of C${}_2$ and C${}_3$. This is in direct contrast to the better-studied non-C${}_2$ DIBs who have reduced strengths in molecule-rich environments. We also identify for the first time the $Q$(2), $Q$(3), and $Q$(4) transitions of the ${}^{13}$C${}^{12}$C (2-0) Phillips band in a stacked average spectrum, and estimate the isotopic ratio of carbon ${}^{12}$C/${}^{13}$C as 79$\pm$8. Our search for the C${}_4$ and C${}_5$ optical bands was unsuccessful.

31 pages, 23 figures. To appear in A&A

References in corpus (23)

• A Catalog of Diffuse Interstellar Bands in the Spectrum of HD 204827
• Studies of the Diffuse Interstellar Bands. III. HD 183143
• Abundances and Behavior of 12CO, 13CO, and C2 in Translucent Sight Lines
• Confirming interstellar C${}_{60}^{+}$ using the Hubble Space Telescope
• ExoMol line lists XXXI: Spectroscopy of lowest eights electronic states of C${}_2$
• The ESO Diffuse Interstellar Bands Large Exploration Survey: EDIBLES I. Project description, survey sample and quality assessment
• Carbon isotopic fractionation in molecular clouds
• A sensitivity study of the neutral-neutral reactions C + C3 and C + C5 in cold dense interstellar clouds
• Gas-grain model of carbon fractionation in dense molecular clouds
• The Behavior of Selected Diffuse Interstellar Bands with Molecular Fraction in Diffuse Atomic and Molecular Clouds
• Interstellar 12C/13C from CH+ absorption lines: Results from an extended survey
• Abundances and rotational temperatures of the C2 interstellar molecule towards six reddened early-type stars
• Detection of vibronic bands of C${}_3$ in a translucent cloud towards HD 169454
• HD 62542: Probing the Bare, Dense Core of a Translucent Interstellar Cloud
• CRIRES high-resolution near-infrared spectroscopy of diffuse interstellar band profiles. Detection of 12 new DIBs in the YJ band and the introduction of a combined ISM sight line and stellar analysis approach
• Centrosymmetric molecules as possible carriers of diffuse interstellar bands
• First detection of the carbon chain molecules 13CCC and C13CC towards SgrB2(M)
• Dense molecular clouds in the SN2008fp host galaxy
• The EDIBLES survey V: Line profile variations in the $\lambda \lambda$5797, 6379, and 6614 diffuse interstellar bands as a tool to constrain carrier sizes
• The Transition from Diffuse Molecular Gas to Molecular Cloud Material in Taurus
• Small carbon chains in circumstellar envelopes
• The Bending of C${}_3$: Experimentally Probing the $l$-type Doubling and Resonance
• Theoretical studies of carbon isotopic fractionation in reactions of C with C${}_2$: dynamics, kinetics, and isotopologue equilibria

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• Spectral survey of the diffuse gas toward BL Lac in the Q band