Séminaire/Seminar Galaxies |
| « HerS-3: An Exceptional Einstein Cross Reveals a Massive Dark Matter Halo » |
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Pierre Cox |
| We present a study of HerS-3, a dusty star-forming galaxy at z=3.0607, which is gravitationally amplified into an exceptional Einstein cross with a fifth image of the background galaxy seen at the center of the cross. The 1-mm spectra of each of the five images obtained with the NOrthern Extended Millimeter Array (NOEMA) display a series of molecular lines that have similar central velocities, unambiguously confirming that the five images have identical redshifts. The high angular (0.1") resolution 1~mm dust continuum measured with the Atacama Large sub-Millimeter Array (ALMA) reveals the detailed morphology of each image. The HST F110W image shows a foreground lensing group of four galaxies with a photometric redshift z~0.96. Lens models that only include the four visible galaxies are unable to reproduce the properties of HerS-3. By adding a fifth massive component, lying ~2.0” south-east of the group, the source reconstruction does match precisely the peak emission, shape and orientation for each of the five images. The fact that no galaxy is detected near that position indicates the presence of a massive dark matter halo in the lensing galaxy group. In the source plane, HerS-3 appears as an infrared luminous starburst galaxy seen edge-on. The serendipitous discovery of this exceptional Einstein cross offers a potential laboratory for exploring at small spatial scales a nuclear starburst at the peak of cosmic evolution and studying the properties of a massive dark matter halo associated with the lensing galaxy group. |
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jeudi 31 octobre 2024 - 11:30 Salle des séminaires Évry Schatzman Institut d'Astrophysique de Paris |
| Page web du séminaire / Seminar's webpage |