TY - JOUR
T1 - COSMOS 5921+0638
T2 - Characterization and analysis of a new strong gravitationally lensed AGN
AU - Anguita, T.
AU - Faure, C.
AU - Kneib, J. P.
AU - Wambsganss, J.
AU - Knobel, C.
AU - Koekemoer, A. M.
AU - Limousin, M.
N1 - Copyright:
Copyright 2019 Elsevier B.V., All rights reserved.
PY - 2009/11/3
Y1 - 2009/11/3
N2 - Context.Strong lens candidates have been newly identified within the COSMOS field.We present VLT/FORS1 spectroscopic followup observations and HST/WFPC2 imaging of the system COSMOS 5921+0638, which exhibits quadruply lensed images and a perfect Einstein ring. Aims.We investigate the nature of COSMOS 5921+0638 by studying its photometric, spectroscopic and physical properties. Methods.By analyzing our VLT/FORS1 spectroscopy and Subaru/CFHT/HST imaging of COSMOS 5921+0638, we completed both an environmental analysis and detailed analytical and grid-based mass modeling to determine it properties. Results.We measured the redshifts of the lensing galaxy in COSMOS 5921+0638 (zl = 0.551 ± 0.001) and 9 additional galaxies in the field (5 of them at z1 0.35). The redshift of the lensed source was inferred by identifying a candidate Lya line at zs = 3.14 ± 0.05. The mass modeling reveals the requirement of a small external shear (? = 0.038), which is slightly larger than the lensing contribution expected by galaxy groups along the line-of-sight obtained from the zCOSMOS optical group catalog (?groups ∼0.01 and ?groups ∼0.005). The estimated time-delays between the different images are of the order of hours to half a week and the total magnification of the background source is μ ̃ 150. The measured mass-to-light ratio of the lensing galaxy within the Einstein ring is M/LB ̃ 8.5 ± 1.6. Anomalies are observed between the measured and expected flux ratios of the images of the background AGN. Conclusions.Our analysis indicates that the ring and point-like structures in COSMOS 5921+0638 consist of a lensed high redshift galaxy hosting a low luminosity AGN (LLAGN). The observed flux ratio anomalies are probably due to microlensing by stars in the lensing galaxy and/or a combination of static phenomena. Multi-epoch, multi-band space-based observations would allow us to differentiate between the possible causes of these anomalies, since static and/or dynamic variations could be identified. Because of its short time-delays and the possibility of microlensing, COSMOS 5921+0638 is a promising laboratory for future studies of LLAGNs.
AB - Context.Strong lens candidates have been newly identified within the COSMOS field.We present VLT/FORS1 spectroscopic followup observations and HST/WFPC2 imaging of the system COSMOS 5921+0638, which exhibits quadruply lensed images and a perfect Einstein ring. Aims.We investigate the nature of COSMOS 5921+0638 by studying its photometric, spectroscopic and physical properties. Methods.By analyzing our VLT/FORS1 spectroscopy and Subaru/CFHT/HST imaging of COSMOS 5921+0638, we completed both an environmental analysis and detailed analytical and grid-based mass modeling to determine it properties. Results.We measured the redshifts of the lensing galaxy in COSMOS 5921+0638 (zl = 0.551 ± 0.001) and 9 additional galaxies in the field (5 of them at z1 0.35). The redshift of the lensed source was inferred by identifying a candidate Lya line at zs = 3.14 ± 0.05. The mass modeling reveals the requirement of a small external shear (? = 0.038), which is slightly larger than the lensing contribution expected by galaxy groups along the line-of-sight obtained from the zCOSMOS optical group catalog (?groups ∼0.01 and ?groups ∼0.005). The estimated time-delays between the different images are of the order of hours to half a week and the total magnification of the background source is μ ̃ 150. The measured mass-to-light ratio of the lensing galaxy within the Einstein ring is M/LB ̃ 8.5 ± 1.6. Anomalies are observed between the measured and expected flux ratios of the images of the background AGN. Conclusions.Our analysis indicates that the ring and point-like structures in COSMOS 5921+0638 consist of a lensed high redshift galaxy hosting a low luminosity AGN (LLAGN). The observed flux ratio anomalies are probably due to microlensing by stars in the lensing galaxy and/or a combination of static phenomena. Multi-epoch, multi-band space-based observations would allow us to differentiate between the possible causes of these anomalies, since static and/or dynamic variations could be identified. Because of its short time-delays and the possibility of microlensing, COSMOS 5921+0638 is a promising laboratory for future studies of LLAGNs.
KW - Cosmology: observations
KW - Galaxies: individual: COSMOS 5921+0638
KW - Galaxies: quasars: individual: COSMOS 5921+0638
KW - Gravitational lensing
UR - http://www.scopus.com/inward/record.url?scp=70449637461&partnerID=8YFLogxK
U2 - 10.1051/0004-6361/200912091
DO - 10.1051/0004-6361/200912091
M3 - Article
AN - SCOPUS:70449637461
VL - 507
SP - 35
EP - 46
JO - Astronomy and Astrophysics
JF - Astronomy and Astrophysics
SN - 0004-6361
IS - 1
ER -