Discovery of a Strong-lens Galaxy Pair with the Smallest Projected Separation
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arXiv
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| Format: | Preprint |
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2026
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| _version_ | 1866914593214824448 |
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| author | He, Zizhao Deng, Limeng Chen, Qihang Shu, Yiping Li, Nan Wu, Di |
| author_facet | He, Zizhao Deng, Limeng Chen, Qihang Shu, Yiping Li, Nan Wu, Di |
| contents | We present the spectroscopic confirmation and lens modeling of HSC~J0233$-$0205, a strong-lensing system produced by a close pair of elliptical galaxies at $z_d=0.790\pm0.022$ that lenses a multi-component background source at $z_s=2.160\pm0.002$. The two deflectors are separated by only $0\arcsec.481\pm0\arcsec.004$ ($3.596\pm0.046$ kpc), making this system a compact galaxy-pair lens at relatively high redshift. Joint five-band HSC lens modeling requires two mass components, with Einstein radii of $0\arcsec.774\pm0\arcsec.011$ and $0\arcsec.767\pm0\arcsec.014$, and yields a circularized Einstein radius of $θ_{\rm E}=1\arcsec.549\pm0\arcsec.018$ for the overall system. The lensed source is reconstructed with three components: two extended components separated by $0\arcsec.462\pm0\arcsec.013$ ($3.830\pm0.108$ kpc), together with a compact component nearly aligned with one of them. Integrating the lensing convergence map within the critical curve gives a projected mass of $M_{\rm lensing,crit}=(9.626\pm0.010)\times10^{11}M_\odot$. Combining this with the stellar mass inferred from SED fitting, $M_{\ast,{\rm crit}}=(1.570\pm0.240)\times10^{11}M_\odot$, we obtain a projected dark-matter fraction within the critical curve of $f_{\rm dm}=83.7\pm2.5\%$. Within the $z$-band effective radii of the two deflectors, the corresponding dark-matter fractions are $82.1\pm4.5\%$ and $65.7\pm6.7\%$, respectively. HSC~J0233$-$0205 is therefore a compact, high-redshift galaxy-pair lens. Future high-resolution imaging and spatially resolved spectroscopy will enable detailed tests of merger signatures, the redistribution of stellar and dark matter, and possible light--mass offsets in the lens plane. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2603_12790 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Discovery of a Strong-lens Galaxy Pair with the Smallest Projected Separation He, Zizhao Deng, Limeng Chen, Qihang Shu, Yiping Li, Nan Wu, Di Astrophysics of Galaxies Cosmology and Nongalactic Astrophysics We present the spectroscopic confirmation and lens modeling of HSC~J0233$-$0205, a strong-lensing system produced by a close pair of elliptical galaxies at $z_d=0.790\pm0.022$ that lenses a multi-component background source at $z_s=2.160\pm0.002$. The two deflectors are separated by only $0\arcsec.481\pm0\arcsec.004$ ($3.596\pm0.046$ kpc), making this system a compact galaxy-pair lens at relatively high redshift. Joint five-band HSC lens modeling requires two mass components, with Einstein radii of $0\arcsec.774\pm0\arcsec.011$ and $0\arcsec.767\pm0\arcsec.014$, and yields a circularized Einstein radius of $θ_{\rm E}=1\arcsec.549\pm0\arcsec.018$ for the overall system. The lensed source is reconstructed with three components: two extended components separated by $0\arcsec.462\pm0\arcsec.013$ ($3.830\pm0.108$ kpc), together with a compact component nearly aligned with one of them. Integrating the lensing convergence map within the critical curve gives a projected mass of $M_{\rm lensing,crit}=(9.626\pm0.010)\times10^{11}M_\odot$. Combining this with the stellar mass inferred from SED fitting, $M_{\ast,{\rm crit}}=(1.570\pm0.240)\times10^{11}M_\odot$, we obtain a projected dark-matter fraction within the critical curve of $f_{\rm dm}=83.7\pm2.5\%$. Within the $z$-band effective radii of the two deflectors, the corresponding dark-matter fractions are $82.1\pm4.5\%$ and $65.7\pm6.7\%$, respectively. HSC~J0233$-$0205 is therefore a compact, high-redshift galaxy-pair lens. Future high-resolution imaging and spatially resolved spectroscopy will enable detailed tests of merger signatures, the redistribution of stellar and dark matter, and possible light--mass offsets in the lens plane. |
| title | Discovery of a Strong-lens Galaxy Pair with the Smallest Projected Separation |
| topic | Astrophysics of Galaxies Cosmology and Nongalactic Astrophysics |
| url | https://arxiv.org/abs/2603.12790 |