| Issue |
A&A
Volume 701, September 2025
|
|
|---|---|---|
| Article Number | A1 | |
| Number of page(s) | 7 | |
| Section | Extragalactic astronomy | |
| DOI | https://doi.org/10.1051/0004-6361/202554887 | |
| Published online | 26 August 2025 | |
Radial dependence of the ratio of Fe II to Mg II equivalent widths in emission-line galaxies
1
Guangxi Key Laboratory for Relativistic Astrophysics, School of Physical Science and Technology, Guangxi University, Nanning 530004, PR China
2
School of Physics and Electronic Information, Guangxi Minzu University, Nanning 530006, PR China
⋆ Corresponding author: luruijing@gxu.edu.cn
Received:
31
March
2025
Accepted:
5
July
2025
Context. The circumgalactic medium (CGM) plays a key role in galaxy evolution by regulating gas accretion, feedback, and metal enrichment, with its chemical evolution and metal distribution revealed through quasar absorption line studies.
Aims. Using data from Sloan Digital Sky Survey extended Baryon Oscillation Spectroscopic Survey (SDSS/eBOSS), we constructed a dataset comprising 853 quasar-emission-line-galaxy (quasar-ELG) pairs with an impact parameter (dp) within 150 kpc. We then analyzed the variations in the ratio of the equivalent widths of the Fe II absorption line to the Mg II absorption line as a function of the impact parameter.
Methods. To achieve this aim, we employed a spectral stacking method to generate median composite spectra in the rest frame of the foreground ELGs. Subsequently, we measured the equivalent widths of the Fe IIλ2600 (Wrλ2600) and Mg IIλ2796 (Wrλ2796) absorption lines in these composite spectra.
Results. Our results indicate that the equivalent width ratio of R (≡Wrλ2600/Wrλ2796) varies as R ∝ (−0.64−0.06+0.08) log(dp [kpc]). Finally, we explored the potential causes and implications of this radial dependence.
Key words: galaxies: general / galaxies: halos / quasars: absorption lines
© The Authors 2025
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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