The effect of a strong external radiation field on protostellar envelopes in Orion

Abstract

We discuss the effects of an enhanced interstellar radiation field (ISRF) on the observables of protostellar cores in the Orion cloud region. Dust radiative transfer is used to constrain the envelope physical structure by reproducing SCUBA 850 micron emission. Previously reported 13CO, C17O and H2CO line observations are reproduced through detailed Monte Carlo line radiative transfer models. It is found that the 13CO line emission is marginally optically thick and sensitive to the physical conditions in the outer envelope. An increased temperature in this region is needed in order to reproduce the 13CO line strengths and it is suggested to be caused by a strong heating from the exterior, corresponding to an ISRF in Orion 10^3 times stronger than the "standard" ISRF. The typical temperatures in the outer envelope are higher than the desorption temperature for CO. The C17O emission is less sensitive to this increased temperature but rather traces the bulk envelope material. The data are only fit by a model where CO is depleted, except in the inner and outermost regions where the temperature increases above 30-40 K. The fact that the temperatures do not drop below approximately 25 K in any of the envelopes whereas a significant fraction of CO is frozen-out suggest that the interstellar radiation field has changed through the evolution of the cores. The H2CO lines are successfully reproduced in the model of an increased ISRF with constant abundances of 3-5x10^{-10}.

arXiv comment11 pages, 10 figures. Accepted for publication in A&A

References in corpus (21)

• An atomic and molecular database for analysis of submillimetre line observations
• Tracing the Mass during Low-Mass Star Formation. II. Modelling the Submillimeter Emission from Pre-Protostellar Cores
• Physical structure and CO abundance of low-mass protostellar envelopes
• Does IRAS 16293-2422 have a hot core? Chemical inventory and abundance changes in its protostellar environment
• Molecular Inventories and Chemical Evolution of Low-mass Protostellar Envelopes
• User Manual for DUSTY
• The H2CO abundance in the inner warm regions of low mass protostellar envelopes
• Numerical methods for non-LTE line radiative transfer: Performance and convergence characteristics
• The structure of protostellar envelopes derived from submillimeter continuum images
• Models for Dense Molecular Cloud Cores
• Molecular freeze-out as a tracer of the thermal and dynamical evolution of pre- and protostellar cores
• Astrochemistry of Sub-Millimeter Sources in Orion: Studying the Variations of Molecular Tracers with Changing Physical Conditions
• Imaging chemical differentiation around the low-mass protostar L483-mm
• H2CO and CH3OH abundances in the envelopes around low-mass protostars
• Modeling the Physical Structure of the Low Density Pre-protostellar Core Lynds 1498
• Physical-chemical modeling of the low-mass protostar IRAS 16293-2422
• Periodic X-ray Emission from the O7 V Star theta^1 Orionis C
• On the origin of H2CO abundance enhancements in low-mass protostars
• B335: A Laboratory for Astrochemistry in a Collapsing Cloud
• Massive Quiescent Cores in Orion. I. Temperature Structure
• Mapping of Large Scale 158 micron [CII] Line Emission: Orion A

Cited by in corpus (37)

• Interpreting Spectral Energy Distributions from Young Stellar Objects. I. A grid of 200,000 YSO model SEDs
• Astrochemistry During the Formation of Stars
• The ALMA-PILS survey: The sulphur connection between protostars and comets: IRAS 16293-2422 B and 67P/Churyumov-Gerasimenko
• Continuum Variability of Deeply Embedded Protostars as a Probe of Envelope Structure
• The nature of the Class I population in Ophiuchus as revealed through gas and dust mapping
• APEX-CHAMP+ high-J CO observations of low-mass young stellar objects: IV. Mechanical and radiative feedback
• The Bolocam Galactic Plane Survey. XIV. Physical Properties of Massive Starless and Star Forming Clumps
• The Spitzer c2d Survey of Large, Nearby, Interstellar Clouds.X. The Chamaeleon II Pre-Main Sequence Population as Observed With IRAC and MIPS
• Molecule sublimation as a tracer of protostellar accretion: Evidence for accretion bursts from high angular resolution C18O images
• Hierarchical Fragmentation of the Orion Molecular Filaments
• Subarcsecond Submillimeter Imaging of the Ultracompact HII Region G5.89-0.39
• Dense Gas Tracers in Perseus: Relating the N2H+, NH3, and Dust Continuum Properties of Pre- and Proto-Stellar Cores
• ALMA observations of the kinematics and chemistry of disc formation
• The dust temperatures of the prestellar cores in the rho Oph main cloud and in other star forming regions: consequences for the core mass function
• APEX-CHAMP+ high-J CO observations of low-mass young stellar objects: II. Distribution and origin of warm molecular gas
• Observations of nitrogen isotope fractionation in deeply embedded protostars
• The JCMT Gould Belt Survey: Evidence for Dust Grain Evolution in Perseus Star-forming Clumps
• Physical structure and water line spectrum predictions of the Intermediate Mass protostar OMC2-FIR4
• The JCMT Transient Survey: Detection of sub-mm variability in a Class I protostar EC 53 in Serpens Main
• High angular resolution observations towards OMC-2 FIR 4: Dissecting an intermediate-mass protocluster
• Waterfalls around protostars: Infall motions towards Class 0/I envelopes as probed by water
• Survey Observations to Study Chemical Evolution from High-mass Starless Cores to High-mass Protostellar Objects I: HC3N and HC5N
• Strong irradiation of protostellar cores in Corona Australis
• Star formation in the Vela Molecular Ridge. Large scale mapping of cloud D in the mm continuum
• The Small-Scale Physical Structure and Fragmentation Difference of Two Embedded Intermediate Mass Protostars in Orion
• Survey Observations to Study Chemical Evolution from High-Mass Starless Cores to High-Mass Protostellar Objects II. HC${}_3$N and N${}_2$H${}^{+}$
• Evolutionary Status of Brightest and Youngest Source in the Orion Molecular Cloud-3 Region
• Externally heated protostellar cores in the Ophiuchus star-forming region
• The methanol lines and hot core of OMC2-FIR4, an intermediate-mass protostar, with Herschel-HIFI
• Physical parameters for Orion KL from modelling its ISO high resolution far-IR CO line spectrum
• Evidence for episodic warm outflowing CO gas from the intermediate mass young stellar object IRAS 08470-4321
• Confirmation of Enhanced Long Wavelength Dust Emission in OMC 2/3
• Modeling water emission from low-mass protostellar envelopes
• ALMA-IMF XVI: Mass-averaged temperature of cores and protostellar luminosities in the ALMA-IMF protoclusters
• Cold Dust in Hot Regions
• The role of external FUV irradiation in the survival of astrophysical ices in Elias 29
• Mass estimates for very cold (< 8 K) gas in molecular cloud cores