Radiative Transfer and Starless Cores

Abstract

We develop a method of analyzing radio frequency spectral line observations to derive data on the temperature, density, velocity, and molecular abundance of the emitting gas. The method incorporates a radiative transfer code with a new technique for handling overlapping hyperfine emission lines within the accelerated lambda iteration algorithm and a heuristic search algorithm based on simulated annnealing. We apply this method to new observations of N_2H^+ in three Lynds clouds thought to be starless cores in the first stages of star formation and determine their density structure. A comparison of the gas densities derived from the molecular line emission and the millimeter dust emission suggests that the required dust mass opacity is about kappa_{1.3mm}=0.04 cm^2/g, consistent with models of dust grains that have opacities enhanced by ice mantles and fluffy aggregrates.

42 pages, 17 figures, to appear in ApJ

References in corpus (15)

• Dense Cores in Dark Clouds. XIV. N2H+(1-0) maps of dense cloud cores
• Systematic Molecular Differentiation in Starless Cores
• Molecular ions in L1544. II. The ionization degree
• Tracing the Mass during Low-Mass Star Formation. II. Modelling the Submillimeter Emission from Pre-Protostellar Cores
• N2H+ and C18O Depletion in a Cold Dark Cloud
• A Survey for Infall Motions toward Starless Cores. II. $CS(2-1)$ and $N_2{H}^{+}(1-0)$ Mapping Observations
• Molecular Evolution in Collapsing Prestellar Cores
• A Catalogue of Optically Selected Cores
• Molecular ions in L1544. I. Kinematics
• An empirical model for protostellar collapse
• Tracing the Mass during Low-Mass Star Formation. III. Models of the Submillimeter Dust Continuum Emission from Class 0 Protostars
• The dust temperature distribution in prestellar cores
• A High Resolution Study of the Slowly Contracting, Starless Core L1544
• Monte Carlo Radiative Transfer in Embedded Prestellar Cores
• Monte Carlo radiative transfer in molecular cloud cores

Cited by in corpus (52)

• Comparing the statistics of interstellar turbulence in simulations and observations: Solenoidal versus compressive turbulence forcing
• Probing the evolutionary status of starless cores through N2H+ and N2D+ observations
• On the internal structure of starless cores. II. A molecular survey of L1498 and L1517B
• First detection of water vapor in a pre-stellar core
• Dynamics and Depletion in Thermally Supercritical Starless Cores
• Water in star-forming regions (WISH): Physics and chemistry from clouds to disks as probed by Herschel spectroscopy
• The Different Structures of the Two Classes of Starless Cores
• The Virial Balance of Clumps and Cores in Molecular Clouds
• Modeling the Physical Structure of the Low Density Pre-protostellar Core Lynds 1498
• The Dust Emissivity Spectral Index in the Starless Core TMC-1C
• Is protostellar heating sufficient to halt fragmentation? A case study of the massive protocluster G8.68-0.37
• Molecular Line Profile Fitting with Analytic Radiative Transfer Models
• Detection of (15)NNH+ in L1544: non-LTE modelling of dyazenilium hyperfine line emission and accurate (14)N/(15)N values
• B335: A Laboratory for Astrochemistry in a Collapsing Cloud
• High sensitivity maps of molecular ions in L1544: I. Deuteration of N2H+ and HCO+ and first evidence of N2D+ depletion
• Modeling molecular hyperfine line emission
• Probing Inward Motions in Starless Cores Using The HCN J = 1-0 Hyperfine Transitions : A Pointing Survey Toward Central Regions
• Dark cloud cores and gravitational decoupling from turbulent flows
• The standard model of star formation applied to massive stars: accretion disks and envelopes in molecular lines
• Mopra CO Observations of the Bubble HII Region RCW120
• Molecular line radiative transfer in protoplanetary disks: Monte Carlo simulations versus approximate methods
• Core and filament formation in magnetized, self-gravitating isothermal layers
• The Initial Conditions of Clustered Star Formation. II. N2H+ Observations of the Ophiuchus B Core
• Oscillations of starless cores
• The Kinematics of Molecular Cloud Cores in the Presence of Driven and Decaying Turbulence: Comparisons with Observations
• Observation of HCN hyperfine line anomalies towards low- and high-mass star-forming cores
• ${}^{14}$N/${}^{15}$N ratio measurements in prestellar cores with N${}_2$H${}^{+}$: new evidence of ${}^{15}$N-antifractionation
• The cosmic-ray ionisation rate in the pre-stellar core L1544
• NH_3(1_0-0_0) in the pre-stellar core L1544
• Molecular Emission Line Formation in Prestellar Cores
• Abundance of HCN and its C and N isotopologues in L1498
• Gravitationally unstable condensations revealed by ALMA in the TUKH122 prestellar core in the Orion A cloud
• H2D+ in the high mass star-forming Region Cygnus-X
• 12mm line survey of the dense molecular gas towards the W28 field TeV gamma-ray sources
• Chemical modeling of the L1498 and L1517B prestellar cores: CO and HCO+ depletion
• Oscillating Starless Cores: The Nonlinear Regime
• CO abundances in a protostellar cloud: freeze-out and desorption in the envelope and outflow of L483
• Reliability of NH3 as the temperature probe of cold cloud cores
• Velocity distribution of collapsing starless cores, L694-2 and L1197
• A large (~1 pc) contracting envelope around the prestellar core L1544
• Supersonic turbulence in the cold massive core JCMT 18354-0649S
• Mapping the prestellar core Ophiuchus D (L1696A) in ammonia
• Deuteration of c-C${}_3$H${}_2$ towards the pre-stellar core L1544
• ALMA reveals a pseudo-disc in a proto-brown dwarf
• Radiative Transfer of HCN: Interpreting observations of hyperfine anomalies
• Properties of the Molecular Cores of Low Luminosity Objects
• Observations and radiative transfer modelling of a massive dense cold core in G333
• Molecular Line Profiles of Collapsing Gas Clouds
• Scaled up low-mass star formation in massive star-forming cores in the G333 giant molecular cloud
• Complex structure of a proto-brown dwarf
• Unified Models of Molecular Emission from Class 0 Protostellar Outflow Sources
• Why do some cores remain starless ?