TY - JOUR

T1 - Large-scale numerical simulations of star formation put to the test

T2 - comparing synthetic images and actual observations for statistical samples of protostars

AU - Frimann, Søren

AU - Jørgensen, Jes Kristian

AU - Haugbølle, Troels

N1 - Accepted for publication in A&A

PY - 2016

Y1 - 2016

N2 - Context. Both observations and simulations of embedded protostars haveprogressed rapidly in recent years. Bringing them together is animportant step in advancing our knowledge about the earliest phases ofstar formation. Aims: To compare synthetic continuum images andspectral energy distributions (SEDs), calculated from large-scalenumerical simulations, to observational studies, thereby aiding in boththe interpretation of the observations and in testing the fidelity ofthe simulations. Methods: The adaptive mesh refinement code,RAMSES, is used to simulate the evolution of a 5 pc × 5 pc ×5 pc molecular cloud. The simulation has a maximum resolution of 8 AU,resolving simultaneously the molecular cloud on parsec scales andindividual protostellar systems on AU scales. The simulation ispost-processed with the radiative transfer code RADMC-3D, which is usedto create synthetic continuum images and SEDs of the protostellarsystems. In this way, more than 13 000 unique radiative transfer models,of a variety of different protostellar systems, are produced. Results: Over the course of 0.76 Myr the simulation forms more than 500protostars, primarily within two sub-clusters. The synthetic SEDs areused to calculate evolutionary tracers Tbol andLsmm/Lbol. It is shown that, while the observeddistributions of the tracers are well matched by the simulation, theygenerally do a poor job of tracking the protostellar ages. Disks formearly in the simulation, with 40% of the Class 0 protostars beingencircled by one. The flux emission from the simulated disks is found tobe, on average, a factor ~6 too low relative to real observations; anissue that can be traced back to numerical effects on the smallestscales in the simulation. The simulated distribution of protostellarluminosities spans more than three order of magnitudes, similar to theobserved distribution. Cores and protostars are found to be closelyassociated with one another, with the distance distribution between thembeing in excellent agreement with observations. Conclusions: Theanalysis and statistical comparison of synthetic observations to realones is established as a powerful tool in the interpretation ofobservational results. By using a large set of post-processedprotostars, which make statistical comparisons to observational surveyspossible, this approach goes beyond comparing single objects to isolatedmodels of star-forming cores.

AB - Context. Both observations and simulations of embedded protostars haveprogressed rapidly in recent years. Bringing them together is animportant step in advancing our knowledge about the earliest phases ofstar formation. Aims: To compare synthetic continuum images andspectral energy distributions (SEDs), calculated from large-scalenumerical simulations, to observational studies, thereby aiding in boththe interpretation of the observations and in testing the fidelity ofthe simulations. Methods: The adaptive mesh refinement code,RAMSES, is used to simulate the evolution of a 5 pc × 5 pc ×5 pc molecular cloud. The simulation has a maximum resolution of 8 AU,resolving simultaneously the molecular cloud on parsec scales andindividual protostellar systems on AU scales. The simulation ispost-processed with the radiative transfer code RADMC-3D, which is usedto create synthetic continuum images and SEDs of the protostellarsystems. In this way, more than 13 000 unique radiative transfer models,of a variety of different protostellar systems, are produced. Results: Over the course of 0.76 Myr the simulation forms more than 500protostars, primarily within two sub-clusters. The synthetic SEDs areused to calculate evolutionary tracers Tbol andLsmm/Lbol. It is shown that, while the observeddistributions of the tracers are well matched by the simulation, theygenerally do a poor job of tracking the protostellar ages. Disks formearly in the simulation, with 40% of the Class 0 protostars beingencircled by one. The flux emission from the simulated disks is found tobe, on average, a factor ~6 too low relative to real observations; anissue that can be traced back to numerical effects on the smallestscales in the simulation. The simulated distribution of protostellarluminosities spans more than three order of magnitudes, similar to theobserved distribution. Cores and protostars are found to be closelyassociated with one another, with the distance distribution between thembeing in excellent agreement with observations. Conclusions: Theanalysis and statistical comparison of synthetic observations to realones is established as a powerful tool in the interpretation ofobservational results. By using a large set of post-processedprotostars, which make statistical comparisons to observational surveyspossible, this approach goes beyond comparing single objects to isolatedmodels of star-forming cores.

KW - stars: formation

KW - stars: protostars

KW - circumstellar matter

KW - protoplanetary disks

KW - radiative transfer

KW - magnetohydrodynamics

U2 - 10.1051/0004-6361/201525702

DO - 10.1051/0004-6361/201525702

M3 - Journal article

VL - 587

JO - Astronomy & Astrophysics

JF - Astronomy & Astrophysics

SN - 0004-6361

M1 - A59

ER -