Spectacular Spitzer images of the Trifid Nebula: Protostars in a young, massive-star-forming region

Abstract

Spitzer IRAC and MIPS images of the Trifid Nebula (M20) reveal its spectacular appearance in infrared light, highlighting the nebula's special evolutionary stage. The images feature recently-formed massive protostars and numerous young stellar objects, and a single O star that illuminates the surrounding molecular cloud from which it formed, and unveil large-scale, filamentary dark clouds. The hot dust grains show contrasting infrared colors in shells, arcs, bow-shocks and dark cores. Multiple protostars are detected in the infrared, within the cold dust cores of TC3 and TC4, which were previously defined as Class 0. The cold dust continuum cores of TC1 and TC2 contain only one protostar each. The Spitzer color-color diagram allowed us to identify ~160 young stellar objects and classify them into different evolutionary stages. The diagram also revealed a unique group of YSOs which are bright at 24 micron but have the spectral energy distribution peaking at 5-8 micron. Despite expectation that Class 0 sources would be "starless" cores, the Spitzer images, with unprecedented sensitivity, uncover mid-infrared emission from these Class 0 protostars. The mid-infrared detections of Class 0 protostars show that the emission escapes the dense, cold envelope of young protostars. The mid-infrared emission of the protostars can be fit by two temperatures of 150 and 400 K; the hot core region is probably optically thin in the mid-infrared regime, and the size of hot core is much smaller than that of the cold envelope. The presence of multiple protostars within the cold cores of Class 0 objects implies that clustering occurs at this early stage of star formation. The TC3 cluster shows that the most massive star is located at the center of the cluster and at the bottom of the gravitational-potential well.

arXiv commentAccepted for publication in ApJ. Full resolution images are available at http://spider.ipac.caltech.edu/staff/rho/

References in corpus (23)

• The Infrared Array Camera (IRAC) for the Spitzer Space Telescope
• Dust Grain Size Distributions and Extinction in the Milky Way, LMC, and SMC
• Infrared Emission from Interstellar Dust. II. The Diffuse Interstellar Medium
• The Formation of Massive Stars from Turbulent Cores
• The Wavelength Dependence of Interstellar Extinction from 1.25 to 8.0 microns Using GLIMPSE Data
• Scattering by Interstellar Dust Grains: Optical and Ultraviolet
• Absolute Calibration of the Infrared Array Camera on the Spitzer Space Telescope
• Massive star formation: Nurture, not nature
• Massive star formation in 100,000 years from turbulent and pressurized molecular clouds
• The Physics of Star Formation
• A CS J=5-4 Mapping Survey Towards High-mass Star Forming Cores Associated with Water Masers
• A "Starless" Core that Isn't: Detection of a Source in the L1014 Dense Core with the Spitzer Space Telescope
• The Circumstellar Environments of High-Mass Protostellar Objects I: Submillimetre Continuum Emission
• Protostars in the Elephant Trunk Nebula
• The 24-Micron View of Embedded Star Formation in NGC 7129
• 3-D Models of Embedded High-Mass Stars: Effects of a Clumpy Circumstellar Medium
• Chandra Observation of the Trifid Nebula: X-ray emission from the O star complex and actively forming pre-main sequence stars
• The Photoionization of a Star-Forming Core in the Trifid Nebula
• Is the Cepheus E Outflow driven by a Class 0 Protostar?
• X-rays and Protostars in the Trifid Nebula
• Pre-Orion Cores in the Trifid Nebula
• Radio continuum emission from the central stars of M20 and the detection of a new supernova remnant near M20
• Windows through the Dusty Disks Surrounding the Youngest Low Mass Protostellar Objects

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• Molecular Cloud Evolution II. From cloud formation to the early stages of star formation in decaying conditions
• Cloud-cloud collisions and triggered star formation
• Overview of the Massive Young Star-Forming Complex Study in Infrared and X-ray (MYStIX) Project
• Dynamical HII Region Evolution in Turbulent Molecular Clouds
• The relations among 8, 24, and 160 micron dust emission within nearby spiral galaxies
• Molecular clouds in the Trifid nebula M20; Possible evidence for a cloud-cloud collision in triggering the formation of the first generation stars
• Triggered O star formation in M20 via cloud-cloud collision: Comparisons between high-resolution CO observations and simulations
• The origin of short-lived radionuclides and the astrophysical environment of solar system formation
• Spitzer IRAC and MIPS Imaging of Clusters and Outflows in 9 High-mass Star Forming Regions
• Detection of an inner gaseous component in a Herbig Be star accretion disk: Near- and mid-infrared spectro-interferometry and radiative transfer modeling of MWC 147
• The MYStIX InfraRed-Excess Source Catalog
• X-ray and IR Point Source Identification and Characteristics In the Embedded, Massive Star-Forming Region RCW 38
• Early-stage young stellar objects in the Small Magellanic Cloud
• A Multiwavelength Look at Galactic Massive Star Forming Regions
• Gradients of chemical abundances in the Milky Way from HII regions: distances derived from Gaia EDR3 parallaxes and temperature inhomogeneities
• Mopra CO Observations of the Bubble HII Region RCW120
• Observational study of sites of triggered star formation: CO and mid-infrared observations
• PAHs as tracers of the molecular gas in star-forming galaxies
• Variation of the extinction law in the Trifid nebula
• X-ray and IR Point Source Identification and Characteristics in the Embedded, Massive Star-Forming Region RCW 108
• Tracing the Energetics and Evolution of Dust with Spitzer: a Chapter in the History of the Eagle Nebula
• Mid-Infrared Images of Stars and Dust in Irregular Galaxies
• Spitzer Observations of the HII Region NGC 2467: An Analysis of Triggered Star Formation
• Properties of protostars in the Elephant Trunk globule IC 1396A
• Young Stellar Groups Around Herbig Ae/Be Stars: A Low-Mass YSO Census
• The Interstellar Bubbles of G38.9-0.4 and the Impact of Stellar Feedback on Star Formation
• The Mid-Infrared Colors of the ISM and Extended Sources at the Galactic Center
• Star Formation in the Trifid Nebula
• The Origin of [CII] 158um Emission toward the HII Region Complex S235
• The correlation between WISE 12 $\mu$m emission and molecular gas tracers on sub-kpc scales in nearby star-forming galaxies
• Candidate X-ray-Emitting OB Stars in the MYStIX Massive Star-Forming Regions
• Carbon- and Oxygen-rich Asymptotic Giant Branch (AGB) stars in the Bulge Asymmetries and Dynamical Evolution (BAaDE) survey
• Probing the massive star forming environment - a multiwavelength investigation of the filamentary IRDC G333.73+0.37
• Massive Star Formation at the Periphery of the Evolved Giant HII Region W 39
• Star forming activity in the H II regions associated with IRAS 17160-3707 complex
• Astrophysics in 2006
• Young Stellar Populations in MYStIX Star Forming Regions: Candidate Protostars
• A Method to Extract Spatially Resolved Polycyclic Aromatic Hydrocarbon Emission from Spitzer Spectra: Application to M51
• Modeling IR Spectral Energy Distributions: A Pilot Study of Starburst Parameters and Silicate Absorption Curves for Some GOALS Galaxies
• Coeval intermediate-mass star formation in N4W
• The Effect of Molecular Cloud Properties on the Kinematics of Stars Formed in the Trifid Region
• The Young Stellar Population, Distance, and Cloud-Cloud Collision Induced Star Formation Scenario of the Trifid Nebula
• SDSS-V LVM: Resolving Physical Conditions in the Trifid Nebula
• The Interaction of Supernova Remnant G357.7+0.3 with the Interstellar Medium
• Massive Star Formation in the LMC. I. N159 and N160 Complexes
• On the nature of V2282 Sgr