The Galactic Center Lobe as an HII Region

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Hauptverfasser: Anderson, L. D., Luisi, Matteo, Liu, B., Linville, Dylan J., Benjamin, Robert A., Hurley-Walker, Natasha, McClure-Griffiths, N. M., Zucker, Catherine
Format: Preprint
Veröffentlicht: 2024
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author Anderson, L. D.
Luisi, Matteo
Liu, B.
Linville, Dylan J.
Benjamin, Robert A.
Hurley-Walker, Natasha
McClure-Griffiths, N. M.
Zucker, Catherine
author_facet Anderson, L. D.
Luisi, Matteo
Liu, B.
Linville, Dylan J.
Benjamin, Robert A.
Hurley-Walker, Natasha
McClure-Griffiths, N. M.
Zucker, Catherine
contents The Galactic center lobe (GCL) is an object ~1° across that is located north of the Galactic center. In the mid-infrared (MIR) the GCL appears as two 8.0$μ$m filaments between which is strong 24$μ$m and radio continuum emission. Due to its morphology and location in the sky, previous authors have argued that the GCL is located in the Galactic center region, created by outflows from star formation or by activity of the central black hole Sagittarius A*. In an associated paper (Hurley-Walker et al., 2024, in press), low-frequency radio emission indicates that the GCL must instead lie foreground to the Galactic center. If the GCL is foreground to the Galactic center, it is likely to be a type of object common throughout the Galactic disk; we here investigate whether its properties are similar to those of Galactic HII regions. We find that the GCL's MIR morphology, MIR flux densities, dust temperatures, and radio recombination line (RRL) properties as traced by the GBT Diffuse Ionized Gas Survey (GDIGS) are consistent with those of known Galactic HII regions, although the derived electron temperature is low. We search for the ionizing source(s) of the possible HII region and identify a stellar cluster candidate (Camargo #1092/Ryu & Lee #532) and a cluster of young stellar objects (SPICY G359.3+0.3) whose members have Gaia parallaxes distances of 1.7${\pm}$0.4kpc. Taken together, the results of our companion paper and those shown here suggest that the GCL has properties consistent with those of an HII region located ~2kpc from the Sun.
format Preprint
id arxiv_https___arxiv_org_abs_2405_11054
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle The Galactic Center Lobe as an HII Region
Anderson, L. D.
Luisi, Matteo
Liu, B.
Linville, Dylan J.
Benjamin, Robert A.
Hurley-Walker, Natasha
McClure-Griffiths, N. M.
Zucker, Catherine
Astrophysics of Galaxies
The Galactic center lobe (GCL) is an object ~1° across that is located north of the Galactic center. In the mid-infrared (MIR) the GCL appears as two 8.0$μ$m filaments between which is strong 24$μ$m and radio continuum emission. Due to its morphology and location in the sky, previous authors have argued that the GCL is located in the Galactic center region, created by outflows from star formation or by activity of the central black hole Sagittarius A*. In an associated paper (Hurley-Walker et al., 2024, in press), low-frequency radio emission indicates that the GCL must instead lie foreground to the Galactic center. If the GCL is foreground to the Galactic center, it is likely to be a type of object common throughout the Galactic disk; we here investigate whether its properties are similar to those of Galactic HII regions. We find that the GCL's MIR morphology, MIR flux densities, dust temperatures, and radio recombination line (RRL) properties as traced by the GBT Diffuse Ionized Gas Survey (GDIGS) are consistent with those of known Galactic HII regions, although the derived electron temperature is low. We search for the ionizing source(s) of the possible HII region and identify a stellar cluster candidate (Camargo #1092/Ryu & Lee #532) and a cluster of young stellar objects (SPICY G359.3+0.3) whose members have Gaia parallaxes distances of 1.7${\pm}$0.4kpc. Taken together, the results of our companion paper and those shown here suggest that the GCL has properties consistent with those of an HII region located ~2kpc from the Sun.
title The Galactic Center Lobe as an HII Region
topic Astrophysics of Galaxies
url https://arxiv.org/abs/2405.11054