Kinematics of young stellar objects in NGC 2024 based on infrared proper motions

Abstract

The most recently formed young stellar objects (YSOs) in active star forming regions are excellent tracers of their parent cloud motion. Their positions and dynamics provide insight into cluster formation and constrain kinematic decoupling timescales between stars and gas. However, because of their strong extinction and young age, embedded YSOs are mainly visible at infrared wavelengths and thus absent from astrometric surveys such as Gaia. We measured the proper motions of 6,769 sources toward the NGC 2024 cluster in the Flame Nebula using multi-epoch near-infrared observations from three ESO public surveys: VISIONS, VHS, and the VISTA/VIRCAM science verification program. Cross-validation of our results with Gaia using optically visible stars shows excellent agreement, with uncertainties on the same order of magnitude. For 362 YSO candidates identified from the literature, we derived proper motions on the order of <5 mas/yr with mean measurement uncertainties of ~0.22 mas/yr. This is the first homogeneous proper motion measurement of this quality for more than half of these stars. For Class I and flat-spectrum sources, our results provide a >13-fold increase in available proper motion measurements. We analyzed the positional and kinematic differences between YSO classes and confirmed a previously reported inside-out age segregation from younger to older stars, likely driven by an outward movement of older stars. No evidence of prolonged hierarchical assembly was found. Instead, the results support a rapid (<1 Myr) cluster collapse. This scenario also accounts for the observed slightly higher 1D velocity dispersion of Class I sources relative to Class flat objects. YSO radial velocities generally align with the gas velocities measured from 12CO(3-2), HNC(1-0), HCN(1-0), and show a weaker correlation with N_2H+(1-0). Some Class II and III objects appear to be already decoupling.

19 pages, 19 figures, 3 tables. Accepted for publication in A&A

References in corpus (27)

• The Resolved Properties of Extragalactic Giant Molecular Clouds
• Filamentary structure of star-forming complexes
• A Large Catalog of Accurate Distances to Local Molecular Clouds: The Gaia DR2 Edition
• The Gould's Belt Distances Survey (GOBELINS) II. Distances and structure towards the Orion Molecular Clouds
• The anatomy of the Orion B Giant Molecular Cloud: A local template for studies of nearby galaxies
• A Classification Scheme for Young Stellar Objects Using the WIDE-FIELD INFRARED SURVEY EXPLORER AllWISE Catalog: Revealing Low-Density Star Formation in the Outer Galaxy
• A Galactic-scale gas wave in the Solar Neighborhood
• Unifying low and high mass star formation through density amplified hubs of filaments
• Properties of the dense core population in Orion B as seen by the Herschel Gould Belt survey
• The star formation history of the Sco-Cen association. Coherent star formation patterns in space and time
• Age Gradients in the Stellar Populations of Massive Star Forming Regions Based on a New Stellar Chronometer
• Core-Halo Age Gradients and Star Formation in the Orion Nebula and NGC~2024 Young Stellar Clusters
• Protoplanetary disk masses in NGC 2024: Evidence for two populations
• Low Mass Stars and Brown Dwarfs in NGC 2024: Constraints on the Substellar Mass Function
• Characterizing the line emission from molecular clouds. II. A comparative study of California, Perseus, and Orion A
• Most nearby young star clusters formed in three massive complexes
• The Corona Australis star formation complex is accelerating away from the Galactic plane
• Extinction of Taurus, Orion, Perseus and California Molecular Clouds Based on the LAMOST, 2MASS and Gaia surveys I: Three-dimensional Extinction and Structure
• Kinematics of the Optically Visible YSOs Toward the Orion B Molecular Cloud
• The physical properties of Cluster Chains
• Emergence of high-mass stars in complex fiber networks (EMERGE). I. Early ALMA Survey: observations and massive data reduction
• The APEX Large CO Heterodyne Orion Legacy Survey (ALCOHOLS). I. Survey overview
• Understanding the Planetary Formation and Evolution in Star Clusters(UPiC)-I: Evidence of Hot Giant Exoplanets Formation Timescales
• VISIONS: The VISTA Star Formation Atlas -- I. Survey overview
• The NEMESIS Catalogue of Young Stellar Objects for the Orion Star Formation Complex. I. General description of data curation
• Emergence of high-mass stars in complex fiber networks (EMERGE) IV. Environmental dependence of the fiber widths
• VISIONS: The VISTA Star Formation Atlas -- II. The data processing pipeline