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- de la Fuente, Eduardo, et al.
(författare)
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Ultracompact H II regions with extended emission: the case of G43.89-0.78 and its molecular environment
- 2020
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 497:4, s. 4436-4447
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Tidskriftsartikel (refereegranskat)abstract
- The Karl Jansky Very Large Array (VLA), Owens Valley Radio Observatory (OVRO), Atacama Large Millimetric Array (ALMA), and the infrared Spitzer observatories are powerful facilities to study massive star formation regions and related objects such as ultra-compact (UC) H II regions, molecular clumps, and cores. We used these telescopes to study the UC H II region G43.89-0.78. The morphological study at arcminute scales using NVSS and Spitzer data shows that this region is similar to those observed in the bubble-like structures revealed by Spitzer observations. With this result, and including a physical characterization based on 3.6 cm data, we suggest G43.89-0.78 be classified as an UC H II region with Extended Emission because it meets the operational definition given in this paper comparing radio continuum data at 3.6 and 20 cm. For the ultra-compact component, we use VLA data to obtain physical parameters at 3.6 cm confirming this region as an UC H II region. Using ALMA observations, we detect the presence of a dense (2.6 x 10(7) cm(-3)) and small (similar to 2.0 arcsec; 0.08 pc) molecular clump with a mass of 220 M-circle dot and average kinetic temperature of 21 K, located near to the UC H II region. In this clump, catalogued as G43.890-0.784, water masers also exist, possibly tracing a bipolar outflow. We discover in this vicinity two additional clumps which we label as G43.899-0.786 (T-d = 50 K; M = 11 M-circle dot) and G43.888-0.787 (T-d = 50 K; M = 15 M-circle dot).
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| 2. |
- De La Fuente, Eduardo, et al.
(författare)
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Ultracompact HII regions with extended emission: The complete view
- 2020
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 492:1, s. 895-914
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Tidskriftsartikel (refereegranskat)abstract
- © 2019 The Author(s). In this paper, we present the results of a morphological study performed on a sample of 28 ultracompact HII (UC HII) regions located near extended free-free emission, using radio continuum (RC) observations at 3.6 cm with the C and D Very Large Array (VLA) configurations, with the aim of determining a direct connection between them. By using previously published observations in B and D VLA configurations, we compiled a final catalogue of 21 UC HII regions directly connected with the surrounding extended emission (EE). The observed morphology of most of the UC HII regions in RC emission is irregular (single- or multipeaked sources) and resembles a classical bubble structure in the Galactic plane with well-defined cometary arcs. RC images superimposed on colour composite Spitzer images reinforce the assignations of direct connection by the spatial coincidence between the UC components and regions of saturated 24 μm emission. We also find that the presence of EE may be crucial to understand the observed infrared excess because an underestimation of ionizing Lyman photons was considered in previous works (e.g. Wood & Churchwell; Kurtz, Churchwell & Wood).
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