Optical+NIR analysis of a Newly Confirmed Einstein ring at z$\sim$1 from the Kilo-Degree Survey: Dark matter fraction, total and dark matter density slope and IMF
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| Formato: | Preprint |
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2025
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| author | Li, Rui Napolitano, Nicola R. Ago, Giuseppe D Shalyapin, Vyacheslav N. Zhu, Kai Guo, Xiaotong Li, Ran Koopmans, Leon V. E. Spiniello, Chiara Tortora, Crescenzo La Barbera, Francesco Feng, Haicheng Gao, Liang Huang, Zhiqi Kuijken, Koen Li, Hui Xie, Linghua Radovich, Mario Sergeyev, Alexey |
| author_facet | Li, Rui Napolitano, Nicola R. Ago, Giuseppe D Shalyapin, Vyacheslav N. Zhu, Kai Guo, Xiaotong Li, Ran Koopmans, Leon V. E. Spiniello, Chiara Tortora, Crescenzo La Barbera, Francesco Feng, Haicheng Gao, Liang Huang, Zhiqi Kuijken, Koen Li, Hui Xie, Linghua Radovich, Mario Sergeyev, Alexey |
| contents | We report the spectroscopic confirmation of a bright blue Einstein ring in the Kilo Degree Survey (KiDS) footprint: the Einstein ``blue eye''. Spectroscopic data from X-Shooter at the Very Large Telescope (VLT) show that the lens is a typical early-type galaxy (ETG) at $z_l=0.9906$, while the background source is a Ly$α$ emitter at $z_s=2.823$. The reference lens modeling was performed on a high-resolution $Y-$band adaptive-optics image from HAWK-I at VLT. Assuming a singular isothermal ellipsoid (SIE) total mass density profile, we inferred an Einstein radius $R_{Ein}=10.47 \pm 0.06$ kpc. The average slope of the total mass density inside the Einstein radius, as determined by a joint analysis of lensing and isotropic Jeans equations is $γ_{tot}=2.14^{+0.06}_{-0.07}$, showing no systematic deviation from the slopes of lower redshift galaxies, This can be the evidence of ETGs developing through dry mergers plus moderate dissipationless accretion. Stellar population analysis with 8-band ($gri$ZYJHK$s$) photometries from KiDS and VIKING shows that the total stellar mass of the lens is $M*=(3.95\pm 0.35)\times 10^{11} M_\odot$ (Salpeter Initial Mass Function, IMF), implying a dark matter fraction inside the effective radius to be $f_{\rm DM}=0.307\pm 0.151$. We finally explored the dark matter halo slope and found a strong degeneracy with the dynamic stellar mass. Dark matter adiabatic contraction is needed to explain the posterior distribution of the slope unless IMF heavier than Salpeter is assumed. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2503_10180 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Optical+NIR analysis of a Newly Confirmed Einstein ring at z$\sim$1 from the Kilo-Degree Survey: Dark matter fraction, total and dark matter density slope and IMF Li, Rui Napolitano, Nicola R. Ago, Giuseppe D Shalyapin, Vyacheslav N. Zhu, Kai Guo, Xiaotong Li, Ran Koopmans, Leon V. E. Spiniello, Chiara Tortora, Crescenzo La Barbera, Francesco Feng, Haicheng Gao, Liang Huang, Zhiqi Kuijken, Koen Li, Hui Xie, Linghua Radovich, Mario Sergeyev, Alexey Astrophysics of Galaxies We report the spectroscopic confirmation of a bright blue Einstein ring in the Kilo Degree Survey (KiDS) footprint: the Einstein ``blue eye''. Spectroscopic data from X-Shooter at the Very Large Telescope (VLT) show that the lens is a typical early-type galaxy (ETG) at $z_l=0.9906$, while the background source is a Ly$α$ emitter at $z_s=2.823$. The reference lens modeling was performed on a high-resolution $Y-$band adaptive-optics image from HAWK-I at VLT. Assuming a singular isothermal ellipsoid (SIE) total mass density profile, we inferred an Einstein radius $R_{Ein}=10.47 \pm 0.06$ kpc. The average slope of the total mass density inside the Einstein radius, as determined by a joint analysis of lensing and isotropic Jeans equations is $γ_{tot}=2.14^{+0.06}_{-0.07}$, showing no systematic deviation from the slopes of lower redshift galaxies, This can be the evidence of ETGs developing through dry mergers plus moderate dissipationless accretion. Stellar population analysis with 8-band ($gri$ZYJHK$s$) photometries from KiDS and VIKING shows that the total stellar mass of the lens is $M*=(3.95\pm 0.35)\times 10^{11} M_\odot$ (Salpeter Initial Mass Function, IMF), implying a dark matter fraction inside the effective radius to be $f_{\rm DM}=0.307\pm 0.151$. We finally explored the dark matter halo slope and found a strong degeneracy with the dynamic stellar mass. Dark matter adiabatic contraction is needed to explain the posterior distribution of the slope unless IMF heavier than Salpeter is assumed. |
| title | Optical+NIR analysis of a Newly Confirmed Einstein ring at z$\sim$1 from the Kilo-Degree Survey: Dark matter fraction, total and dark matter density slope and IMF |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2503.10180 |