We report an in-depth study of the chemistry of cyanopolyynes in the prototypical L1544 prestellar core.
Using the 100 m Robert C. Byrd Green Bank Telescope (GBT), we observe 3 HC3N emission lines, 9 HC5N lines, 5 HC7N lines and 9 HC9N lines. HC9N is detected for the first time towards the source.
The high spectral resolution (∼0.05 km s−1) reveals double-peaked spectral line profiles with the red-shifted peak 3–5 times brighter. Resolved maps of the nucleus in other molecular tracers indicate that the southern region is redshifted. Therefore, most of the cyanopolyyne emission is likely associated with the southern region of the core, where free carbon atoms are available to form long chains, thanks to the more efficient illumination of radiation from the interstellar field.
We perform a simultaneous modeling of the HC5N, HC7N and HC9N lines, to study the origin of the emission. To allow this analysis, we performed a new calculation of the collision coefficients. The simultaneous fitting indicates a kinetic gas temperature of 5 to 12 K, a source size of 80$\arcsec$ and a gas density greater than 100 cm−3. The HC5N:HC7N:HC9N abundance ratios measured in L1544 are approximately 1:6:4.
We compare our observations with those of the well-studied starless core TMC-1 and with measurements available in different star forming regions. The comparison suggests that complex carbon chain chemistry is active in other sources and is related to the presence of free gaseous carbon. Finally, we discuss possible pathways of formation and destruction in light of new observations.
Eleonora Bianchi, Anthony Remijan, Claudio Codella, Cecilia Ceccarelli, François Lique, Silvia Spezzano, Nadia Balucani, Paola Caselli, Eric Herbst, Linda Podio, Charlotte Vastel, Brett McGuire
Comments: 16 pages, 7 figures, 3 tables
Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2301.10106 [astro-ph.GA] (or arXiv:2301.10106v1 [astro-ph.GA] for this release)
By: Eleonora Bianchi
[v1] Tue Jan 24 2023 4:19:05 PM UTC (7,916 KB)