Carbon-chain molecule survey toward four low-mass molecular outflow sources

Front. Astron. Space Sci.

et al. 2022

The Tian Ma Radio Telescope (TMRT), which is mainly used for deep space exploration and radio astronomy observations, is the largest fully steerable radio telescope in Asia. For promoting the automation of the telescope, an automatic early warning system is designed and implemented. The system can conveniently aggregate heterogeneous sensor data, make use of established strategies to implement an alert system, and send real-time alarms through multiple channels, which is helpful to promote unmanned operation. In addition, we adopt DevOps (a compound of development (Dev) and operations (Ops) which means end-to-end automation in software development and delivery) to simplify the development, upgrading, and maintenance of the telescope automatic early warning system.

Section: Introductionmentioning

confidence: 99%

The Tian Ma 65-m Telescope Automatic Early Warning System

Shang-Guan

Rong-Bing

Front. Astron. Space Sci.

et al. 2022

A FAST survey of H I narrow-line self-absorptions in Planck Galactic cold clumps guided by HC₃N

Liu

et al. 2022

A&A

Self Cite

Using the Five-hundred-meter Aperture Spherical radio Telescope (FAST), we search for H I narrow-line self-absorption (HINSA) features in twelve Planck Galactic cold clumps (PGCCs), the starless core L1521B, and four star forming sources. Eight of the 12 PGCCs have detected emission of J = 2–1 of cyanoacetylene (HC3N). With an improved HINSA extraction method more robust for weaker and blended features with high velocity resolution, the detection rates of HINSA in PGCCs are high, at 92% overall (11/12) and 87% (7/8) among sources with HC3N J = 2–1 emissions. Combining the data of molecular spectra and Planck continuum maps, we studied the morphologies, dynamics, abundances and excitations of H I, CO and HC3N in PGCCs. The spatial distribution of HINSA is similar to that of CO, implying that HINSA features are confined to regions within and around CO emission kernels. HINSA tends to be not detected in regions associated with warm dust and background ionizing radiation, as well as regions associated with stellar objects. The L-band continnum and average background H I emission may be non-ignorable for the excitation of HINSA. The abundances of cold H I in PGCCs are approximately 3 × 10−4, and vary within a factor of ~3. The non-thermal velocity dispersions traced by C18O J = 1–0 and HINSA are consistent with each other (0.1–0.4 km s−1), larger than the typical value of HC3N (~0.1 km s−1). Carbon chain molecule (CCM) abundant PGCCs provide a good sample to study HINSA.

Cyanopolyyne line survey towards high-mass star-forming regions with TMRT

Wang

Yan

et al. 2022

A&A

Context. Cyanopolyynes (HC2n+1 N, n = 1,2,3), which are the linear carbon chain molecules, are precursors for the prebiotic synthesis of simple amino acids. They are important for understanding prebiotic chemistry and may be good tracers of the star formation sequence. Aims. We aim to search for cyanopolyynes in high-mass star-forming regions (HMSFRs) at possibly different evolutionary stages, investigate the evolution of HC3N and its relation with shock tracers, and detect the existence of HC5N and HC7N in HMSFRs with a formed protostar. Methods. We carried out a cyanopolyyne line survey towards a large sample of HMSFRs using the Shanghai Tian Ma 65 m Radio Telescope (TMRT). Our sample consisted of 123 targets taken from the TMRT C band line survey. It included three kinds of sources, namely those with detection of the 6.7 GHz CH3OH maser alone, with detection of the radio recombination line (RRL) alone, and with detection of both (hereafter referred to as Maser-only, RRL-only, and Maser-RRL sources, respectively). For our sample with detection of cyanopolyynes, their column densities were derived using the rotational temperature measured from the NH3 lines. We constructed and fitted the far-infrared (FIR) spectral energy distributions (SED; obtained from the Herschel FIR data and the Atacama Pathfinder Experiment data at 870 µm) of our HC3N sources. Moreover, by analysing the relation between HC3N and other shock tracers, we also investigate whether HC3N is a good tracer of shocks. Results. We detected HC3N in 38 sources, HC5N in 11 sources, and HC7N in G24.790+0.084, with the highest detection rate being found for Maser-RRL sources and a very low detection rate found for RRL-only sources. The mean column density of HC3N was found to be (1.75 ± 0.42) × 1013, (2.84 ± 0.47) × 1013, and (0.82 ± 0.15) × 1013 cm−2 for Maser-only, Maser-RRL, and RRL-only sources, respectively. Based on a fit of the FIR SED, we derive their dust temperatures, H2 column densities, and abundances of cyanopolyynes relative to H2. The mean relative abundance of HC3N was found to be (1.22 ± 0.52) × 10−10 for Maser-only, (5.40 ± 1.45) × 10−10 for Maser-RRL, and (1.65 ± 1.50) × 10−10 for RRL-only sources, respectively. Conclusions. The detection rate, the column density, and the relative abundance of HC3N increase from Maser-only to Maser-RRL sources and decrease from Maser-RRL to RRL-only sources. This trend is consistent with the proposed evolutionary trend of HC3N under the assumption that our Maser-only, Maser-RRL, and RRL-only sources correspond to massive young stellar objects, ultracompact H ii regions, and normal classical H ii regions, respectively. Our detections enlarge the sample of HC3N in HMSFRs and support the idea that unsaturated complex organic molecules can exist in HMSFRs with a formed protostar. Furthermore, a statistical analysis of the integrated line intensity and column density of HC3N and shock-tracing molecules (SiO, H2CO) enabled us to find positive correlations between them. This suggests that HC3N may be another tracer of shocks, and should therefore be the subject of further observations and corresponding chemical simulations. Our results indirectly support the idea that the neutral-neutral reaction between C2H2 and CN is the dominant formation pathway of HC3N.