Cyanopolyyne Chemistry In The L1544 Prestellar Core: New Insights From GBT Observations

By Keith Cowing
Status Report
January 25, 2023
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Cyanopolyyne Chemistry In The L1544 Prestellar Core: New Insights From GBT Observations
Dust temperature calculated from l/SPIRE data at 250, 350, and 500 µm observations towards L1544 and presented in Spezzano et al. (2016). We show superposed in black the GBT HPBWs in the two observed bands. — astro-ph.SR

We report a comprehensive study of the cyanopolyyne chemistry in the prototypical prestellar core L1544.

Using the 100m Robert C. Byrd Green Bank Telescope (GBT) we observe 3 emission lines of HC3N, 9 lines of HC5N, 5 lines of HC7N, and 9 lines of HC9N. HC9N is detected for the first time towards the source.

The high spectral resolution (∼ 0.05 km s−1) reveals double-peak spectral line profiles with the redshifted peak a factor 3-5 brighter. Resolved maps of the core in other molecular tracers indicates that the southern region is redshifted. Therefore, the bulk 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 the interstellar field radiation.

We perform a simultaneous modelling of the HC5N, HC7N, and HC9N lines, to investigate the origin of the emission. To enable this analysis, we performed new calculation of the collisional coefficients. The simultaneous fitting indicates a gas kinetic temperature of 5–12 K, a source size of 80$\arcsec$, and a gas density larger than 100 cm−3. The HC5N:HC7N:HC9N abundance ratios measured in L1544 are about 1:6:4.

We compare our observations with those towards the the well-studied starless core TMC-1 and with the available measurements in different star-forming regions. The comparison suggests that a complex carbon chain chemistry is active in other sources and it is related to the presence of free gaseous carbon. Finally, we discuss the possible formation and destruction routes in the light of the new observations.

Eleonora Bianchi, Anthony Remijan, Claudio Codella, Cecilia Ceccarelli, Francois Lique, Silvia Spezzano, Nadia Balucani, Paola Caselli, Eric Herbst, Linda Podio, Charlotte Vastel, Brett McGuire

Comments: 16 pages, 7 figure, 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 version)
Submission history
From: Eleonora Bianchi
[v1] Tue, 24 Jan 2023 16:19:05 UTC (7,916 KB)
Astrobiology, Astrochemistry

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