A FAST survey of H I narrow-line self-absorptions in <i>Planck</i> Galactic cold clumps guided by HC<sub>3</sub>N

Liu, Xunchuan; Wu, Yuefang; Zhang, C.; Tang, Ningyu; Liu, T.; Wang, K.; Li, D.; Qian, Lei; Qin, Sheng-Li; Esimbek, Jarken; Wang, J.; Yuan, Jinghua; Xu, Fengrong; Yuan, Lixia

doi:10.1051/0004-6361/202141477

Cited by 5 publications

(17 citation statements)

References 92 publications

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“…We followed the method of Liu et al (2022) to extract HINSA features. To extract HINSA, it was required to understand the physical properties of the emission regions, at least the central velocity, v c,m , velocity dispersion, σ m , and excitation temperature, T ex (i.e., the initial conditions to extract HINSA; see Liu et al 2022). These three physical parameters were obtained by using the high-sensitivity molecular-line observations of the high-mass star-forming region G176.51+00.20 made by Liu et al (2021).…”

Section: Data Analysis and Resultsmentioning

confidence: 99%

“…The only detected 12 CO emission, corresponding to Beams 2, 5, and 7, is also weak. The HINSA features in the WCER are probably associated with CO-dark or CO-faint gas (e.g., Wolfire et al 2010;Tang et al 2016;Liu et al 2022). This is an issue worthy of further observations.…”

Section: Association Between the Hinsa Features And The Molecular Cloudsmentioning

confidence: 90%

“…H I narrow-line self-absorption (HINSA), a special case of HISA, is usually associated with CO clouds, and its line width is comparable to or smaller than that of CO (see Li & Goldsmith 2003;Goldsmith & Li 2005;Tang et al 2016;Wang et al 2020). HINSA has been found to be an excellent tracer of molecular clouds (Li & Goldsmith 2003), and this tight correlation has been confirmed by numerous studies (e.g., Krčo & Goldsmith 2010;Tang et al 2020;Liu et al 2022).…”

Section: Introductionmentioning

confidence: 88%

“…Stars form in molecular clouds, and it is important for star formation to synthesize molecular H 2 from atomic H. However, it is difficult to directly extract individual components from H I emission and correlate them with molecular clouds (Li & Goldsmith 2003;Liu et al 2022). In such conditions, H I selfabsorption (HISA) lines have become a very useful tracer of H I. HISA occurs in environments where cold H I gas is in front of a warmer emission background (e.g., Knapp 1974); such conditions are ubiquitous in the Milky Way (e.g., Heeschen 1955;Gibson et al 2000;Wang et al 2020).…”

Section: Introductionmentioning

confidence: 99%

“…Numerous surveys have provided abundant knowledge about the environment and physical properties of the regions producing HINSA. For instance, the detection rate of HINSA is ∼77% (Li & Goldsmith 2003) in optically selected dark clouds (Lee & Myers 1999), ∼80% (Krčo & Goldsmith 2010) in molecular cores (Lynds 1962;i.e., the Lynds dark cloud, which has a peak optical extinction of 6 mag or more; see the catalog of dark clouds in), and ∼58% (Tang et al 2020) to ∼92% (Liu et al 2022) in Planck Galactic cold clumps (PGCCs; cold and quiescent clumps in very early evolution stages of star formation; see Planck Collaboration et al 2011;Wu et al 2012;Planck Collaboration et al 2016). These results indicate that HINSA is associated with molecular clouds, especially molecular cores and/or clumps.…”

Section: Introductionmentioning

confidence: 99%

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H i Narrow-line Self-absorptions toward the High-mass Star-forming Region G176.51+00.20

et al. 2022

ApJL

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Using the Five-hundred-meter Aperture Spherical radio Telescope (FAST) 19-beam tracking observational mode, high-sensitivity and high-velocity-resolution H i spectral lines have been observed toward the high-mass star-forming region G176.51+00.20. This is a pilot study searching for H i narrow-line self-absorption (HINSA) toward high-mass star-forming regions where bipolar molecular outflows have been detected. This work is confined to the central seven beams of FAST. Two HINSA components are detected in all seven beams, which correspond to a strong CO emission region (SCER; with a velocity of ∼−18 km s−1) and a weak CO emission region (WCER; with a velocity of ∼−3 km s−1). The SCER detected in Beam 3 is probably more suitably classified as a WCER. In the SCER, the HINSA is probably associated with the molecular material traced by the CO. The fractional abundance of HINSA ranges from ∼1.1 × 10−3 to ∼2.6 × 10−2. Moreover, the abundance of HINSA in Beam 1 is lower than that in the surrounding beams (i.e., Beams 2 and 4–7). This possible ring could be caused by the ionization of H i or the relatively rapid conversion from H i to H2 in the higher-density inner region. In the WCER (including Beam 3 in the SCER), the HINSA is probably not associated with CO clouds, but with CO-dark or CO-faint gas.

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Section: Data Analysis and Resultsmentioning

confidence: 99%

Section: Association Between the Hinsa Features And The Molecular Cloudsmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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H i Narrow-line Self-absorptions toward the High-mass Star-forming Region G176.51+00.20

et al. 2022

ApJL

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Peering into the Milky Way by FAST: I. Exquisite Hi structures in the inner Galactic disk from the piggyback line observations of the FAST GPPS survey

Hong

Han

Hou

et al. 2022

Sci. China Phys. Mech. Astron.

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Neutral hydrogen (Hi) is the fundamental component of the interstellar medium. The Galactic Plane Pulsar Snapshot (GPPS) survey is designed for hunting pulsars by using the Five-hundred-meter Aperture Spherical radio Telescope (FAST) from the visible Galactic plane within |b| ≤ 10 • . The survey observations are conducted with the L-band 19-beam receiver in the frequency range of 1.0 − 1.5 GHz, and each pointing has an integration time of 5 minutes. The piggyback spectral data simultaneously recorded during the FAST GPPS survey are great resources for studies on the Galactic Hi distribution and ionized gas. We process the piggyback Hi data of the FAST GPPS survey in the region of 33 • ≤ l ≤ 55 • and |b| ≤ 2 • . The rms of the data cube is found to be approximately 40 mK at a velocity resolution of 0.1 km s −1 , placing it the most sensitive observations of the Galactic Hi by far. The high velocity resolution and high sensitivity of the FAST GPPS Hi data enable us to detect weak exquisite Hi structures in the interstellar medium. Hi absorption line with great details can be obtained against bright continuum sources. The FAST GPPS survey piggyback Hi data cube will be released and updated on the web: http://zmtt.bao.ac.cn/MilkyWayFAST/.

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Cyanopolyyne Chemistry in the L1544 Prestellar Core: New Insights from GBT Observations

Bianchi

Remijan

Codella

et al. 2023

ApJ

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We report a comprehensive study of the cyanopolyyne chemistry in the prototypical prestellar core L1544. Using the 100 m Robert C. Byrd Green Bank Telescope, we observe three emission lines of HC3N, nine lines of HC5N, five lines of HC7N, and nine lines of HC9N. HC9N is detected for the first time toward 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 indicate 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 modeling 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″, 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 toward 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 is related to the presence of free gaseous carbon. Finally, we discuss the possible formation and destruction routes in light of the new observations.

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

Cited by 5 publications

References 92 publications

H i Narrow-line Self-absorptions toward the High-mass Star-forming Region G176.51+00.20

H i Narrow-line Self-absorptions toward the High-mass Star-forming Region G176.51+00.20

Peering into the Milky Way by FAST: I. Exquisite Hi structures in the inner Galactic disk from the piggyback line observations of the FAST GPPS survey

Cyanopolyyne Chemistry in the L1544 Prestellar Core: New Insights from GBT Observations

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

Cited by 5 publications

References 92 publications

H i Narrow-line Self-absorptions toward the High-mass Star-forming Region G176.51+00.20

H i Narrow-line Self-absorptions toward the High-mass Star-forming Region G176.51+00.20

Peering into the Milky Way by FAST: I. Exquisite Hi structures in the inner Galactic disk from the piggyback line observations of the FAST GPPS survey

Cyanopolyyne Chemistry in the L1544 Prestellar Core: New Insights from GBT Observations

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