The ultracompact regions G40.54+2.59 and G34.13+0.47: A new detection of compact radio sources

Abstract

We report the detection of three compact ($<0.001$ pc) radio sources (CRSs) at K${}_a$-band (0.9 cm) in the \uchiirs G040.54+2.59 (two CRSs) and G034.13+0.47 (one CRS). These CRSs have weak flux densities and are located at the center of their respective \uchii regions. We found no clear association between massive ionizing stars and CRSs but some radiative influence on the latter, as suggested by their large emission measures (> $10^7{\mathrm{cm}}^{-6}\mathrm{pc}$), typical of photo evaporating neutral objects close to or associated with massive stars. Our modelling of G40.54+2.59 shows that their CRSs supply enough ionized material to shape its morphology while significantly extending its observable lifetime. On the other hand, despite the possible relation of the CRS with the large-scale outflow signatures observed in G034.13+0.47, the influence of this CRS on the evolution of the \uchii region is unlikely. Our results show that the presence of CRSs can alleviate the so-called lifetime problem of UCHII regions. Still, to address their dynamical evolution adequately, the scenario must include additional mechanisms like ambient confinement, or the role of the kinematics of their associated stellar objects.

arXiv commentPublished in Publications of the Astronomical Society of Japan, Volume 75, Issue 1, February 2023, Pages 90-102, https://doi.org/10.1093/pasj/psac090

References in corpus (34)

• The UKIDSS Galactic Plane Survey
• First GLIMPSE Results on the Stellar Structure of the Galaxy
• A Parallax-based Distance Estimator for Spiral Arm Sources
• The Dynamics of Radiation Pressure-Dominated HII Regions
• Ionizing Photon Emission Rates from O- and Early B-type Stars and Clusters
• Properties of Hi-GAL clumps in the inner Galaxy]{The Hi-GAL compact source catalogue. I. The physical properties of the clumps in the inner Galaxy ($-71.0^{\circ }<\ell <67.0^{\circ }$)
• The Co-ordinated Radio and Infrared Survey for High-Mass Star Formation - II. Source Catalogue
• The RMS Survey: 6 cm continuum VLA observations towards candidate massive YSOs in the northern hemisphere
• The formation of massive stars: accretion, disks and the development of hypercompact HII regions
• New Catalogs of Compact Radio Sources in the Galactic Plane
• Radio Jets from Young Stellar Objects
• Understanding Spatial and Spectral Morphologies of Ultracompact H II Regions
• Observations on the Formation of Massive Stars by Accretion
• The RMS Survey: The Bolometric Fluxes and Luminosity Distributions of Young Massive Stars
• ATLASGAL - Kinematic distances and the dense gas mass distribution of the inner Galaxy
• Wind bubbles within H II regions around slowly moving stars
• Radio outburst from a massive (proto)star. When accretion turns into ejection
• Radio Measurements of the stellar proper motions in the core of the Orion Nebula Cluster
• Expansion of W 3(OH)
• Morphologies of Ultracompact HII Regions in W49A and Sgr B2: Prevalence of Shells and a Modified Classification Scheme
• A search for hypercompact HII regions in the Galactic Plane
• Mining the UKIDSS GPS: star formation and embedded clusters
• An IR Study of the Velocity Structure of the Cometary Compact HII region G29.96-0.02
• Searching for new hypercompact HII regions
• VLBA determination of the distance to nearby star-forming regions VII. Monoceros R2
• The cometary HII regions of DR 21: Bow shocks or champagne flows or both?
• ALMA Observations of the Extraordinary Carina Pillars: HH 901/902
• The compact, time-variable radio source projected inside W3(OH): Evidence for a Photoevaporated Disk?
• Searching for compact radio sources associated to UCHII regions
• The richness of compact radio sources in NGC 6334D to F
• Do individual Spitzer young stellar object candidates enclose multiple UKIDSS sources?
• A Massive Young Runaway Star in W49 North
• Ultracompact HII regions with extended emission: The case of G43.89-0.78 and its molecular environment
• Masgomas-4: Physical characterization of a double-core obscured cluster with a massive and very young stellar population