A multiwavelength study of the W33 Main ultracompact HII region

Abstract

The dynamics of ionized gas around the W33 Main ultracompact HII region is studied using observations of hydrogen radio recombination lines and a detailed multiwavelength characterization of the massive star-forming region W33 Main is performed. We used the Giant Meterwave Radio Telescope (GMRT) to observe the H167$\alpha$ recombination line at 1.4 GHz at an angular resolution of 10 arcsec, and Karl. G. Jansky Very Large Array (VLA) data acquired in the GLOSTAR survey to study the dynamics of ionized gas. We also observed the radio continuum at 1.4 GHz and 610 MHz with the GMRT and used GLOSTAR 4$-$8 GHz continuum data to characterize the nature of the radio emission. In addition, archival data from submillimeter to near-infrared wavelengths were used to study the dust emission and identify YSOs in the W33 Main star-forming region. The radio recombination lines were detected at good signal to noise in the GLOSTAR data, while the H167$\alpha$ radio recombination line was marginally detected with the GMRT. The spectral index of radio emission in the region determined from GMRT and GLOSTAR shows the emission to be thermal in the entire region. Along with W33 Main, an arc-shaped diffuse continuum source, G12.81$-$0.22, was detected with the GMRT data. The GLOSTAR recombination line data reveal a velocity gradient across W33 Main and G12.81$-$0.22. The electron temperature is found to be 6343 K and 4843 K in W33 Main and G12.81$-$0.22, respectively. The physical properties of the W33 Main molecular clump were derived by modeling the dust emission using data from the ATLASGAL and Hi-GAL surveys and they are consistent with the region being a relatively evolved site of massive star formation. The gas dynamics and physical properties of G12.81$-$0.22 are consistent with the HII region being in an evolved phase and its expansion on account of the pressure difference is slowing down.

References in corpus (15)

• MAMBO Mapping of Spitzer c2d Small Clouds and Cores
• The UKIDSS Galactic Plane Survey
• Spitzer Observations of NGC 1333: A Study of Structure and Evolution in a Nearby Embedded Cluster
• The Electron Temperature Gradient in the Galactic Disk
• The Early Evolution of Massive Stars: Radio Recombination Line Spectra
• The Spitzer Survey of the Small Magellanic Cloud: Discovery of Embedded Protostars in the HII Region NGC 346
• Metallicity Structure in the Milky Way Disk Revealed by Galactic HII Regions
• A global view on star formation: The GLOSTAR Galactic Plane Survey. I. Overview and first results for the Galactic longitude range 28° < l < 36°
• GLOSTAR -- Radio Source Catalog I: $28^{\circ }<\text{l}<36^{\circ }$ and $|b|<1^{\circ }$
• Diversity of chemistry and excitation conditions in the high-mass star forming complex W33
• FOREST Unbiased Galactic plane Imaging survey with the Nobeyama 45-m telescope (FUGIN) : Molecular clouds toward W33 ; possible evidence for a cloud-cloud collision triggering O star formation
• Massive Stars in the W33 Giant Molecular Complex
• Kinematics and star formation toward W33: a central hub as a hub--filament system
• Uncovering distinct environments in an extended physical system around the W33 complex
• Discovery of a New Population of Galactic HII Regions with Ionized Gas Velocity Gradients

Cited by in corpus (8)

• Physical and chemical complexity in high-mass star-forming regions with ALMA. I. Overview and evolutionary trends of physical properties
• ALMA-IMF X -- The core population in the evolved W33-Main (G012.80) protocluster
• A global view on star formation: The GLOSTAR Galactic plane survey X. Galactic HII region catalog using radio recombination lines
• The ALMA-ATOMS survey: Vibrationally excited HC${}_3$N lines in hot cores
• Imaging Molecular Outflow in Massive Star-forming Regions with HNCO Lines
• MeerKAT and ALMA view of the AGAL045.804-0.356 clump
• A global view on star formation: The GLOSTAR Galactic plane survey XII. Effelsberg's continuum view and data release
• ALMA-IMF VIII -- Combination of Interferometric Continuum Images with Single-Dish Surveys and Structural Analysis of Six Protoclusters