A 0.6 Mpc H ɪ structure associated with Stephan's Quintet
Abstract
Stephan's Quintet (SQ, co-moving radial distance = 85 ± 6 Mpc, taken from the NASA/IPAC Extragalactic Database (NED)) is unique among compact groups of galaxies. Observations have previously shown that interactions between multiple members, including a high-speed intruder galaxy currently colliding into the intragroup medium, have probably generated tidal debris in the form of multiple gaseous and stellar filaments, the formation of tidal dwarfs and intragroup-medium starbursts, as well as widespread intergalactic shocked gas. The details and timing of the interactions and collisions remain poorly understood because of their multiple nature. Here we report atomic hydrogen (H ɪ) observations in the vicinity of SQ with a smoothed sensitivity of 1σ = 4.2 × 10¹⁶ cm⁻² per channel (velocity bin-width Δv = 20 km s⁻¹; angular resolution = 4′), which are about two orders of magnitude deeper than previous observations. The data show a large H ɪ structure (with linear scale of around 0.6 Mpc) encompassing an extended source of size approximately 0.4 Mpc associated with the debris field and a curved diffuse feature of length around 0.5 Mpc attached to the south edge of the extended source. The diffuse feature was probably produced by tidal interactions in early stages of the formation of SQ (>1 Gyr ago), although it is not clear how the low-density H I gas (N_(H ɪ) ≲ 10¹⁸ cm⁻²) can survive the ionization by the intergalactic ultraviolet background on such a long time scale. Our observations require a rethinking of properties of gas in outer parts of galaxy groups and demand complex modelling of different phases of the intragroup medium in simulations of group formation.
Additional Information
© The Author(s) 2022. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. This work is supported by the National Key R&D Programme of China No. 2017YFA0402704 and National Natural Science Foundation of China (NSFC) No. 11873055 and sponsored (in part) by the Chinese Academy of Sciences (CAS) through a grant to the CAS South America Center for Astronomy. C.K.X. acknowledges NSFC grant No. 11733006. C.C. acknowledges NSFC grant No. 11803044 and 12173045. N.-Y.T. is supported by the National key R&D program of China under grant no. 2018YFE0202900 and the Cultivation Project for FAST Scientific Payoff and Research Achievement of CAMS-CAS. J.-S.H. acknowledges NSFC grant No. 11933003. U.L. acknowledges support from project PID2020-114414GB-100, financed by MCIN/AEI/10.13039/501100011033, from project P20_00334 financed by the Junta de Andalucia and from FEDER/Junta de Andalucía-Consejería de Transformaciòn Econòmica, Industria, Conocimiento y Universidades/Proyecto A-FQM-510-UGR20. F.R. acknowledges support from the Knut and Alice Wallenberg Foundation. This work made use of data from FAST, a Chinese national mega-science facility built and operated by the National Astronomical Observatories, CAS. We thank P. Jiang, L. Hou, C. Sun and other FAST operation team members for supports in the observations and data reductions, and H.-C. Feng and Y. Huang for helping with the optical spectroscopic observation of NGC 7320a. Support of the staff from the Lijiang 2.4 m telescope is acknowledged. Funding for the Lijiang 2.4 m telescope has been provided by the CAS and the People's Government of Yunnan Province. This research has made use of the NASA/IPAC Extragalactic Database, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. We dedicate this Article to the memory of Y. Gao, a coauthor of the Article who passed away recently. Contributions. C.K.X. carried out the observations, performed the data reduction, calibration and modelling, and interpreted the results. C.C. carried out the data reduction, calibration and modelling, interpreted the results and collected ancillary data. P.N.A. interpreted the results and proofread the manuscript. P.-A.D. and M.Y. interpreted the results and collected ancillary data. N.-Y.T. carried out the observations and calibration. Y.G., Y.S.D., J.-S.H., U.L. and F.R. interpreted the results. Data availability. Observational data are available from the FAST archive (http://fast.bao.ac.cn) 1 year after data collection, following FAST data policy. The data that support the findings of this study are openly available in Science Data Bank at https://www.scidb.cn/s/jiIfee. Code availability. The Python and IDL code for the data reduction pipeline is available at https://www.scidb.cn/s/jiIfee. The authors declare no competing interests.Attached Files
Published - 41586_2022_Article_5206.pdf
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Additional details
- PMCID
- PMC9581777
- Eprint ID
- 120263
- Resolver ID
- CaltechAUTHORS:20230321-821906400.71
- Created
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2023-06-08Created from EPrint's datestamp field
- Updated
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2023-06-08Created from EPrint's last_modified field
- Caltech groups
- Infrared Processing and Analysis Center (IPAC)