CXOCY J220132.8-320144: An Edge-on Spiral Gravitational Lens
Abstract
We present the CXOCY J220132.8-320144 system, which is composed of an edge-on spiral galaxy at z=0.32 lensing a z=3.9 background quasar. Two images of the quasar are seen. The geometry of the system is favorable to separate the relative mass contribution of the disk and halo in the inner parts of the galaxy. We model the system with one elliptical mass component with the same ellipticity as the light distribution and manage to reproduce the quasar image positions and fluxes. We also model the system with two mass components, disk and halo. Again, we manage to reproduce the quasar image positions and fluxes. However, all models predict at least a third visible image close to the disk that is not seen in our images. We speculate that this is most likely due to extinction by the disk. We also measure the rotational velocity of the galaxy at 2.7 disk scale radius to be vc=130+/-20 km s-1 from the [O II] emission lines. When adding the rotational velocity constraint to the models, we find that the contribution to the rotational velocity of the disk is likely to be equal to or larger than the contribution of the halo at this radius. The detection of the third image and a more accurate measurement of the rotational velocity would help to set tighter constraints on the mass distribution of this edge-on spiral galaxy.
Partly based on observations collected at the European Southern Observatory, Chile, under programs 72.A-509 and 74.A-0493. This paper includes data gathered with the 6.5 meter Magellan Telescopes located at Las Campanas Observatory, Chile.- Publication:
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The Astrophysical Journal
- Pub Date:
- December 2006
- DOI:
- 10.1086/508148
- arXiv:
- arXiv:astro-ph/0611330
- Bibcode:
- 2006ApJ...652..955C
- Keywords:
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- Cosmology: Dark Matter;
- Galaxies: Halos;
- Galaxies: Spiral;
- Galaxies: Structure;
- Cosmology: Gravitational Lensing;
- Astrophysics
- E-Print:
- 8 pages, 5 figures, ApJ accepted (scheduled Dec 1 2006, 652, 955)