Chemical Variation in Molecular Cloud Cores in the Orion A Cloud. II

Abstract

We have mapped six molecular cloud cores in the Orion A giant molecular cloud (GMC), whose kinetic temperatures range from 10 to 30 K, in CCS and N2H+ with Nobeyama 45 m radio telescope to study their chemical characteristics. We identified 31 intensity peaks in the CCS and N2H+ emission in these molecular cloud cores. It is found for cores with temperatures lower than ~ 25 K that the column density ratio of N(N2H+)/N(CCS) is low toward starless core regions while it is high toward star-forming core regions, in case that we detected both of the CCS and N2H+ emission. This is very similar to the tendency found in dark clouds (kinetic temperature ~ 10 K). The criterion found in the Orion A GMC is N(N2H+)/N(CCS) ~ 2-3. In some cases, the CCS emission is detected toward protostars as well as the N2H+ emission. Secondary late-stage CCS peak in the chemical evolution caused by CO depletion may be a possible explanation for this. We found that the chemical variation of CCS and N2H+ can also be used as a tracer of evolution in warm (10-25 K) GMC cores. On the other hand, some protostars do not accompany N2H+ intensity peaks but are associated with dust continuum emitting regions, suggesting that the N2H+ abundance might be decreased due to CO evaporation in warmer star-forming sites.

37 pages, 22 figures, accepted for publication in PASJ; typos in table format corrected

References in corpus (8)

• The Spitzer Space Telescope Survey of the Orion A & B Molecular Clouds - Part I: A Census of Dusty Young Stellar Objects and a Study of their Mid-IR Variability
• Chemistry in Infrared Dark Cloud Clumps: a Molecular Line Survey at 3 mm
• Ethynyl (C2H) in massive star formation: Tracing the initial conditions?
• Hierarchical Fragmentation of the Orion Molecular Filaments
• A Molecular Line Observation toward Massive Clumps Associated with Infrared Dark Clouds
• Massive Quiescent Cores in Orion: Dynamical State Revealed by High-Resolution Ammonia Maps
• A New 100-GHz Band Two-Beam Sideband-Separating SIS Receiver for Z-Machine on the NRO 45-m Radio Telescope
• Molecular Line Observations of a Carbon-Chain-Rich Core L492

Cited by in corpus (13)

• Angular Momentum of the N2H+ Cores in the Orion A Cloud
• Astrochemical Properties of Planck Cold Clumps
• Catalog of dense cores in the Orion A giant molecular cloud
• Survey Observations to Study Chemical Evolution from High-mass Starless Cores to High-mass Protostellar Objects I: HC3N and HC5N
• Nobeyama 45-m mapping observations toward nearby molecular clouds, Orion A, Aquila Rift, and M17: Project overview
• Gravitationally unstable condensations revealed by ALMA in the TUKH122 prestellar core in the Orion A cloud
• An Ammonia Spectral Map of the L1495-B218 Filaments in the Taurus Molecular Cloud: II CCS & HC${}_7$N Chemistry and Three Modes of Star Formation in the Filaments
• Molecular Cloud Cores with High Deuterium Fraction: Nobeyama Single-Pointing Survey
• Thermal Starless Ammonia Core Surrounded by CCS in the Orion A Cloud
• Molecular Cloud Cores with High Deuterium Fractions: Nobeyama Mapping Survey
• Nobeyama 45-m Mapping Observations toward Orion A. III. Multi-Line Observations toward an Outflow-shocked Region, OMC-2 FIR
• Chemical evolution of the HC3N and N2H+ molecules in dense cores of the Vela C giant molecular cloud complex
• Detection of a turbulent gas component associated with a starless core with subthermal turbulence in the Orion A cloud