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 ($T_\textrm{kin}$) 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.Comment: 31 pages, 23 figures. To appear in A&

Cami, Jan

Cordiner, Martin

Cox, Nick L. J.

Ehrenfreund, Pascale

Fan, Haoyu

Farhang, Amin

Foing, Bernard H.

Kulik, Klay

Lallement, Rosine

Linnartz, Harold

MacIsaac, Heather

Rocha, Carlos M. R.

Roueff, Evelyne

Salama, Farid

Sarre, Peter

Smoker, Jonathan

van Loon, Jacco Th.

English

arXiv

arXiv.org e-Print Archive

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

International audienceContext. Small linear carbon chain radicals such as C2 and C3 act as both the building blocks and dissociation fragments of larger carbonaceous species. Their rotational excitation traces the temperature and density of local environments. However, these homo-nuclear di- and triatomic species are only accessible through their electronic and vibrational features because they lack a permanent dipole moment, and high signal-to-noise ratio data are necessary as the result of their generally low abundances in the interstellar medium (ISM).  Aims: In order to improve our understanding of small carbonaceous species in the ISM, we carried out a sensitive survey of C2 and C3 using the ESO Diffuse Interstellar Bands Large Exploration Survey (EDIBLES) dataset. We also expanded our searches to C4, C5, and the 13C12C isotopologue in the most molecule-rich sightlines.  Methods: We fitted synthetic spectra generated following a physical excitation model to the C2 (2-0) Phillips band to obtain the C2 column density (N) as well as the kinetic temperature (Tkin) and number density (n) of the host cloud. The C3 molecule was measured through its Ã − \tilde X (000-000) electronic origin band system. We simulated the excitation of this band with a double-temperature Boltzmann distribution.  Results: We present the largest combined survey of C2 and C3 to date in which the individual transitions can be resolved. In total, we detected C2 in 51 velocity components along 40 sightlines, and C3 in 31 velocity components along 27 sightlines. Further analysis confirms the two molecules are detected in the same velocity components. We find a very good correlation between N(C2) and N(C3) with a Pearson correlation coefficient r = 0.93 and an average N(C2)/N(C3) ratio of 15.5± 1.4. A comparison with the behaviour of the C2 diffuse interstellar bands (DIBs) shows that there are no clear differences among sightlines with and without detections of C2 and C3. This is in direct contrast to the better-studied non-C2 DIBs, which have reduced strengths in molecule-rich environments, consistent with the idea that the C2 DIBs are indeed a distinguishable DIB family. We also identify, for the first time, the Q(2), Q(3), and Q(4) transitions of the 13C12C (2-0) Phillips band in the stacked average spectrum of molecule-rich sightlines, and estimate the isotopic ratio of carbon 12C/13C to be 79±8, consistent with literature results. At this stage it is not yet possible to identify these transitions in individual sightlines. Our search for the C4 and C5 optical bands was unsuccessful; even in stacked spectra no unambiguous identification could be made

Macisaac, Heather

HAL-OBSPM

The EDIBLES survey. VII. A survey of C<sub>2</sub> and C<sub>3</sub> in interstellar clouds

Context. Small linear carbon chain radicals such as C2 and C3 act as both the building blocks and dissociation fragments of larger carbonaceous species. Their rotational excitation traces the temperature and density of local environments. However, these homo-nuclear di- and triatomic species are only accessible through their electronic and vibrational features because they lack a permanent dipole moment, and high signal-to-noise ratio data are necessary as the result of their generally low abundances in the interstellar medium (ISM).
Aims. In order to improve our understanding of small carbonaceous species in the ISM, we carried out a sensitive survey of C2 and C3 using the ESO Diffuse Interstellar Bands Large Exploration Survey (EDIBLES) dataset. We also expanded our searches to C4, C5, and the 13C12C isotopologue in the most molecule-rich sightlines.
Methods. We fitted synthetic spectra generated following a physical excitation model to the C2 (2-0) Phillips band to obtain the C2 column density (N) as well as the kinetic temperature (Tkin) and number density (n) of the host cloud. The C3 molecule was measured through its Ã − $ \tilde X$ (000-000) electronic origin band system. We simulated the excitation of this band with a double-temperature Boltzmann distribution.
Results. We present the largest combined survey of C2 and C3 to date in which the individual transitions can be resolved. In total, we detected C2 in 51 velocity components along 40 sightlines, and C3 in 31 velocity components along 27 sightlines. Further analysis confirms the two molecules are detected in the same velocity components. We find a very good correlation between N(C2) and N(C3) with a Pearson correlation coefficient r = 0.93 and an average N(C2)/N(C3) ratio of 15.5± 1.4. A comparison with the behaviour of the C2 diffuse interstellar bands (DIBs) shows that there are no clear differences among sightlines with and without detections of C2 and C3. This is in direct contrast to the better-studied non-C2 DIBs, which have reduced strengths in molecule-rich environments, consistent with the idea that the C2 DIBs are indeed a distinguishable DIB family. We also identify, for the first time, the Q(2), Q(3), and Q(4) transitions of the 13C12C (2-0) Phillips band in the stacked average spectrum of molecule-rich sightlines, and estimate the isotopic ratio of carbon 12C/13C to be 79±8, consistent with literature results. At this stage it is not yet possible to identify these transitions in individual sightlines. Our search for the C4 and C5 optical bands was unsuccessful; even in stacked spectra no unambiguous identification could be made

Haoyu Fan

Carlos M. R. Rocha

Martin Cordiner

Harold Linnartz

Nick L. J. Cox

Amin Farhang

Jonathan Smoker

Evelyne Roueff

Pascale Ehrenfreund

Farid Salama

Bernard H. Foing

Rosine Lallement

Heather MacIsaac

Klay Kulik

Peter Sarre

Jacco Th. van Loon

Jan Cami

EDP Sciences OAI-PMH repository (1.2.0)

The EDIBLES survey

HAL-INSU

Context. Small linear carbon chain radicals such as C2 and C3 act as both the building blocks and dissociation fragments of larger carbonaceous species. Their rotational excitation traces the temperature and density of local environments. However, these homo-nuclear di- and triatomic species are only accessible through their electronic and vibrational features because they lack a permanent dipole moment, and high signal-to-noise ratio data are necessary as the result of their generally low abundances in the interstellar medium (ISM).Aims. In order to improve our understanding of small carbonaceous species in the ISM, we carried out a sensitive survey of C2 and C3 using the ESO Diffuse Interstellar Bands Large Exploration Survey (EDIBLES) dataset. We also expanded our searches to C4, C5, and the 13C12C isotopologue in the most molecule-rich sightlines.Methods. We fitted synthetic spectra generated following a physical excitation model to the C2 (2-0) Phillips band to obtain the C2 column density (N) as well as the kinetic temperature (Tkin) and number density (n) of the host cloud. The C3 molecule was measured through its Ã −  (000-000) electronic origin band system. We simulated the excitation of this band with a double-temperature Boltzmann distribution.Results. We present the largest combined survey of C2 and C3 to date in which the individual transitions can be resolved. In total, we detected C2 in 51 velocity components along 40 sightlines, and C3 in 31 velocity components along 27 sightlines. Further analysis confirms the two molecules are detected in the same velocity components. We find a very good correlation between N(C2) and N(C3) with a Pearson correlation coefficient r = 0.93 and an average N(C2)/N(C3) ratio of 15.5± 1.4. A comparison with the behaviour of the C2 diffuse interstellar bands (DIBs) shows that there are no clear differences among sightlines with and without detections of C2 and C3. This is in direct contrast to the better-studied non-C2 DIBs, which have reduced strengths in molecule-rich environments, consistent with the idea that the C2 DIBs are indeed a distinguishable DIB family. We also identify, for the first time, the Q(2), Q(3), and Q(4) transitions of the 13C12C (2-0) Phillips band in the stacked average spectrum of molecule-rich sightlines, and estimate the isotopic ratio of carbon 12C/13C to be 79±8, consistent with literature results. At this stage it is not yet possible to identify these transitions in individual sightlines. Our search for the C4 and C5 optical bands was unsuccessful; even in stacked spectra no unambiguous identification could be made

Keele Research Repository

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

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

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arXiv.org e-Print Archive

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EDP Sciences OAI-PMH repository (1.2.0)

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