Effects of Subhalos on Interpreting Highly Magnified Sources Near Lensing Caustics
Large magnification factors near gravitational lensing caustics of galaxy-cluster lenses allow the study of individual stars or compact stellar associations at cosmological distances. We study how the presence of sub-galactic subhalos, an inevitable consequence of cold dark matter, can alter the pro...
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IOP Publishing
2025-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/ada76a |
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| author | Lingyuan Ji Liang Dai |
| author_facet | Lingyuan Ji Liang Dai |
| author_sort | Lingyuan Ji |
| collection | DOAJ |
| description | Large magnification factors near gravitational lensing caustics of galaxy-cluster lenses allow the study of individual stars or compact stellar associations at cosmological distances. We study how the presence of sub-galactic subhalos, an inevitable consequence of cold dark matter, can alter the property of caustics and hence change the interpretation of highly magnified sources that lie atop them. First, we consider a galaxy-cluster halo populated with subhalos sampled from a realistic subhalo mass function calibrated to N -body simulations. Then, we compare a semianalytical approximation and an adaptive ray-shooting method that we employ to quantify the property of the caustics. As a case study, we investigate Earendel, a z = 6.2 candidate of magnified single- or multiple-star system with a lone lensed image atop the critical curve in the Sunrise Arc. We find that the source size constraint (≲0.3 pc) previously derived from macrolens models should be relaxed by a factor of a few to 10 when subhalos are accounted for, therefore allowing the possibility of a compact star cluster. The subhalos could introduce an astrometric perturbation that is ≲0 $\mathop{.}\limits^{\unicode{x02033}}$ 5, which does not contradict observation. These conclusions are largely robust to changes in the subhalo population. Subhalos therefore should be seriously accounted for when interpreting the astrophysical nature of similar highly magnified sources uncovered in recent high- z observations. |
| format | Article |
| id | doaj-art-45cd6a8e4ef14a159b5b554f18a3d04d |
| institution | DOAJ |
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| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
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| spelling | doaj-art-45cd6a8e4ef14a159b5b554f18a3d04d2025-08-20T03:12:46ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01980219010.3847/1538-4357/ada76aEffects of Subhalos on Interpreting Highly Magnified Sources Near Lensing CausticsLingyuan Ji0https://orcid.org/0000-0002-3947-7362Liang Dai1https://orcid.org/0000-0003-2091-8946Berkeley Center for Cosmological Physics, University of California , Campbell Hall 341, Berkeley, CA 94720, USA; Department of Physics, University of California , 366 Physics North MC 7300, Berkeley, CA 94720, USA ; liangdai@berkeley.eduDepartment of Physics, University of California , 366 Physics North MC 7300, Berkeley, CA 94720, USA ; liangdai@berkeley.eduLarge magnification factors near gravitational lensing caustics of galaxy-cluster lenses allow the study of individual stars or compact stellar associations at cosmological distances. We study how the presence of sub-galactic subhalos, an inevitable consequence of cold dark matter, can alter the property of caustics and hence change the interpretation of highly magnified sources that lie atop them. First, we consider a galaxy-cluster halo populated with subhalos sampled from a realistic subhalo mass function calibrated to N -body simulations. Then, we compare a semianalytical approximation and an adaptive ray-shooting method that we employ to quantify the property of the caustics. As a case study, we investigate Earendel, a z = 6.2 candidate of magnified single- or multiple-star system with a lone lensed image atop the critical curve in the Sunrise Arc. We find that the source size constraint (≲0.3 pc) previously derived from macrolens models should be relaxed by a factor of a few to 10 when subhalos are accounted for, therefore allowing the possibility of a compact star cluster. The subhalos could introduce an astrometric perturbation that is ≲0 $\mathop{.}\limits^{\unicode{x02033}}$ 5, which does not contradict observation. These conclusions are largely robust to changes in the subhalo population. Subhalos therefore should be seriously accounted for when interpreting the astrophysical nature of similar highly magnified sources uncovered in recent high- z observations.https://doi.org/10.3847/1538-4357/ada76aStrong gravitational lensingCaustic curveCold dark matter |
| spellingShingle | Lingyuan Ji Liang Dai Effects of Subhalos on Interpreting Highly Magnified Sources Near Lensing Caustics The Astrophysical Journal Strong gravitational lensing Caustic curve Cold dark matter |
| title | Effects of Subhalos on Interpreting Highly Magnified Sources Near Lensing Caustics |
| title_full | Effects of Subhalos on Interpreting Highly Magnified Sources Near Lensing Caustics |
| title_fullStr | Effects of Subhalos on Interpreting Highly Magnified Sources Near Lensing Caustics |
| title_full_unstemmed | Effects of Subhalos on Interpreting Highly Magnified Sources Near Lensing Caustics |
| title_short | Effects of Subhalos on Interpreting Highly Magnified Sources Near Lensing Caustics |
| title_sort | effects of subhalos on interpreting highly magnified sources near lensing caustics |
| topic | Strong gravitational lensing Caustic curve Cold dark matter |
| url | https://doi.org/10.3847/1538-4357/ada76a |
| work_keys_str_mv | AT lingyuanji effectsofsubhalosoninterpretinghighlymagnifiedsourcesnearlensingcaustics AT liangdai effectsofsubhalosoninterpretinghighlymagnifiedsourcesnearlensingcaustics |