The Silk Nebula: A Newly Discovered Giant [OIII] Emission Filament
Abstract
We report [O\,\textsc{iii}] narrow-band imaging of an extremely large-scale nebula, the Silk Nebula, discovered by the SWONS (Super Wide-Field [O\,\textsc{iii}] Narrow-band Survey), together with multi-fiber medium-resolution spectroscopic data covering the Hα, [N\,\textsc{ii}], [S\,\textsc{ii}], and [O\,\textsc{iii}] emission lines, acquired with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) as part of the Medium-Resolution Spectroscopic Survey of Nebulae (MRS-N). Based on 2,684 high-quality spectra, we measured its physical parameters, including relative line intensities, radial velocities (RVs), and full widths at half-maximum (FWHMs). The [S\,\textsc{ii}]/Hα ratio of the nebula significantly exceeds the shock-excitation threshold of 0.4. Its location in BPT diagnostic diagrams and spatial morphology of [O\,\textsc{iii}] both support the optical emission is dominated by shock-heated gas. The oxygen abundance is near solar and spatially uniform, consistent with a shock propagating into the ambient interstellar medium. Because [O\,\textsc{iii}] is the only emission line that clearly traces the nebular morphology, we base our distance estimate exclusively on the [O\,\textsc{iii}] kinematics, obtaining a fiducial distance of ∼160 pc. At this distance, the nebula has a physical extent of ∼28 pc along the north-south direction. We suggest that the Silk Nebula is a large [O\,\textsc{iii}] filament possibly associated with a supernova remnant, although a diffuse-ionized-gas (DIG) or ionized-bubble origin cannot be ruled out with the present data, and one of the largest angular-scale [O\,\textsc{iii}] emission structures documented to date. Future deep X-ray observations and shock-modeling efforts are required to firmly establish its nature.
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BibTeX
@misc{wu2026silk,
title = {{The Silk Nebula: A Newly Discovered Giant [OIII] Emission Filament}},
author = {Yi-Fei Wu and Songyu Jia and Chao-Jian Wu and Chao Zhang and Li-Yue Zhang and Shu Wang and Juan-Juan Ren and Quzhen Dongyang and Hong-Yun Qiu and Zhi-Hong He and Jichen Zhang and Guo-You Sun and Wei-Guo Zhang and Jian-Jun Chen and Hong-Liang Yan and Xiang-Song Fang and Hong Wu},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.13329},
eprint = {2610.13329},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.13329},
}
RIS
TY - UNPB
TI - The Silk Nebula: A Newly Discovered Giant [OIII] Emission Filament
AU - Yi-Fei Wu
AU - Songyu Jia
AU - Chao-Jian Wu
AU - Chao Zhang
AU - Li-Yue Zhang
AU - Shu Wang
AU - Juan-Juan Ren
AU - Quzhen Dongyang
AU - Hong-Yun Qiu
AU - Zhi-Hong He
AU - Jichen Zhang
AU - Guo-You Sun
AU - Wei-Guo Zhang
AU - Jian-Jun Chen
AU - Hong-Liang Yan
AU - Xiang-Song Fang
AU - Hong Wu
PY - 2026
DA - 2026/10/09
PB - arXiv
DO - 10.48550/arxiv.2610.13329
UR - https://arxiv.org/abs/2610.13329
AB - We report [O\,\textsc{iii}] narrow-band imaging of an extremely large-scale nebula, the Silk Nebula, discovered by the SWONS (Super Wide-Field [O\,\textsc{iii}] Narrow-band Survey), together with multi-fiber medium-resolution spectroscopic data covering the Hα, [N\,\textsc{ii}], [S\,\textsc{ii}], and [O\,\textsc{iii}] emission lines, acquired with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) as part of the Medium-Resolution Spectroscopic Survey of Nebulae (MRS-N). Based on 2,684 high-quality spectra, we measured its physical parameters, including relative line intensities, radial velocities (RVs), and full widths at half-maximum (FWHMs). The [S\,\textsc{ii}]/Hα ratio of the nebula significantly exceeds the shock-excitation threshold of 0.4. Its location in BPT diagnostic diagrams and spatial morphology of [O\,\textsc{iii}] both support the optical emission is dominated by shock-heated gas. The oxygen abundance is near solar and spatially uniform, consistent with a shock propagating into the ambient interstellar medium. Because [O\,\textsc{iii}] is the only emission line that clearly traces the nebular morphology, we base our distance estimate exclusively on the [O\,\textsc{iii}] kinematics, obtaining a fiducial distance of ∼160 pc. At this distance, the nebula has a physical extent of ∼28 pc along the north-south direction. We suggest that the Silk Nebula is a large [O\,\textsc{iii}] filament possibly associated with a supernova remnant, although a diffuse-ionized-gas (DIG) or ionized-bubble origin cannot be ruled out with the present data, and one of the largest angular-scale [O\,\textsc{iii}] emission structures documented to date. Future deep X-ray observations and shock-modeling efforts are required to firmly establish its nature.
ER -