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Discovery of HCCCO and C5O in TMC-1 with the QUIJOTE line survey.
- Source :
- Astronomy & Astrophysics / Astronomie et Astrophysique; 12/16/2021, Vol. 656, p1-12, 12p
- Publication Year :
- 2021
-
Abstract
- We report on the detection, for the first time in space, of the radical HCCCO and of pentacarbon monoxide, C<subscript>5</subscript>O. The derived column densities are (1.6 ± 0.2) × 10<superscript>11</superscript> cm<superscript>−2</superscript> and (1.5 ± 0.2) × 10<superscript>10</superscript> cm<superscript>−2</superscript>, respectively. We have also analysed the data for all the molecular species of the families HC<subscript>n</subscript>O and C<subscript>n</subscript>O within our QUIJOTE's line survey. Upper limits are obtained for HC<subscript>4</subscript>O, HC<subscript>6</subscript>O, C<subscript>4</subscript>O, and C<subscript>6</subscript>O. We report a robust detection of HC<subscript>5</subscript>O and HC<subscript>7</subscript>O based on 14 and 12 rotational lines detected with a signal-to-noise ratio ≥30 and ≥5, respectively. The derived N(HC<subscript>3</subscript>O)/N(HC<subscript>5</subscript>O) abundance ratio is 0.09 ± 0.03, while N(C<subscript>3</subscript>O)/N(C<subscript>5</subscript>O) is 80 ± 2, and N(HC<subscript>5</subscript>O)/N(HC<subscript>7</subscript>O) is 2.2 ± 0.3. As opposed to the cyanopolyyne family, HC<subscript>2n + 1</subscript>N, which shows a continuous decrease in the abundances with increasing n, the C<subscript>n</subscript>O and HC<subscript>n</subscript>O species show a clear abundance maximum for n = 3 and 5, respectively. They also show an odd and even abundance alternation, with odd values of n being the most abundant, which is reminiscent of the behaviour of C<subscript>n</subscript>H radicals, where in that case species with even values of n are more abundant. We explored the formation of these species through two mechanisms previously proposed, which are based on radiative associations between C<subscript>n</subscript>H <subscript>m</subscript><superscript>+</superscript> m + $ _m^+ $ ions with CO and reactions of C n̄ n − $ _n^- $ and C<subscript>n</subscript>H<superscript>−</superscript> anions with O atoms, and we found that several species, such as C<subscript>5</subscript>O, HC<subscript>4</subscript>O, and HC<subscript>6</subscript>O, are significantly overestimated. Our understanding of how these species are formed is incomplete as of yet. Other routes based on neutral-neutral reactions such as those of C<subscript>n</subscript> and C<subscript>n</subscript>H carbon chains with O, OH, or HCO, could be behind the formation of these species. [ABSTRACT FROM AUTHOR]
- Subjects :
- SIGNAL-to-noise ratio
Subjects
Details
- Language :
- English
- ISSN :
- 00046361
- Volume :
- 656
- Database :
- Complementary Index
- Journal :
- Astronomy & Astrophysics / Astronomie et Astrophysique
- Publication Type :
- Academic Journal
- Accession number :
- 154297619
- Full Text :
- https://doi.org/10.1051/0004-6361/202142634