We present a multi-wavelength study of the gravitational lens COSMOS~J095930+023427 ($z_l=0.892$), together with the associated galaxy group located at $z\sim0.7$ along the line of sight and the lensed background galaxy. The source redshift is currently unknown, but estimated to be at $z_s \sim 2$. The analysis is based on the available public HST, Subaru, Chandra imaging data, and VLT spectroscopy. The lensing system is an early-type galaxy showing a strong [OII] emission line, and produces 4 bright images of the distant background source. It has an Einstein radius of $0.79''$, about 4 times large than the effective radius. We perform a lensing analysis using both a Singular Isothermal Ellipsoid (SIE) and a Peudo-Isothermal Elliptical Mass Distribution (PIEMD) for the lensing galaxy, and find that the final results on the total mass, the dark matter (DM) fraction within the Einstein radius and the external shear due to a foreground galaxy group are robust with respect of the choice of the parametric model and the source redshift (yet unknown). We measure the luminous mass from the photometric data, and find the DM fraction within the Einstein radius $f_{\rm DM}$ to be between $0.71\pm 0.13$ and $0.79 \pm 0.15$, depending on the unknown source redshift. Meanwhile, the non-null external shear found in our lensing models supports the presence and structure of a galaxy group at $z\sim0.7$, and an independent measurement of the 0.5-2 keV X-ray luminosity within 20'' around the X-ray centroid provides a group mass of $M=(3-10)\times 10^{13}$ M$_{\odot}$, in good agreement with the previous estimate derived through weak lensing analysis. Finally, by inverting the HST/ACS I$_{814}$ image with the lensing equation, we obtain the reconstructed image of the magnified source galaxy, which has a scale of about 3.3 kpc at $z_s=2$ (2.7 kpc at $z_s=4$) and the typical disturbed disk-like appearance observed in low-mass star-forming galaxies at $z\sim3$. However, deep, spatially resolved spectroscopic data for similar lensed sources are still required to detected the first stage of galaxy evolution, since the available spectrum shows no clear feature due to the background source.
A multi-wavelength study of the gravitational lens COSMOS~J095930+023427 / S., Cao; Covone, Giovanni; Paolillo, Maurizio; Z. H., Zhu. - In: RESEARCH IN ASTRONOMY AND ASTROPHYSICS. - ISSN 1674-4527. - STAMPA. - 13:1(2013), pp. 15-27. [10.1088/1674-4527/13/1/003]
A multi-wavelength study of the gravitational lens COSMOS~J095930+023427
COVONE, GIOVANNI;PAOLILLO, MAURIZIO;
2013
Abstract
We present a multi-wavelength study of the gravitational lens COSMOS~J095930+023427 ($z_l=0.892$), together with the associated galaxy group located at $z\sim0.7$ along the line of sight and the lensed background galaxy. The source redshift is currently unknown, but estimated to be at $z_s \sim 2$. The analysis is based on the available public HST, Subaru, Chandra imaging data, and VLT spectroscopy. The lensing system is an early-type galaxy showing a strong [OII] emission line, and produces 4 bright images of the distant background source. It has an Einstein radius of $0.79''$, about 4 times large than the effective radius. We perform a lensing analysis using both a Singular Isothermal Ellipsoid (SIE) and a Peudo-Isothermal Elliptical Mass Distribution (PIEMD) for the lensing galaxy, and find that the final results on the total mass, the dark matter (DM) fraction within the Einstein radius and the external shear due to a foreground galaxy group are robust with respect of the choice of the parametric model and the source redshift (yet unknown). We measure the luminous mass from the photometric data, and find the DM fraction within the Einstein radius $f_{\rm DM}$ to be between $0.71\pm 0.13$ and $0.79 \pm 0.15$, depending on the unknown source redshift. Meanwhile, the non-null external shear found in our lensing models supports the presence and structure of a galaxy group at $z\sim0.7$, and an independent measurement of the 0.5-2 keV X-ray luminosity within 20'' around the X-ray centroid provides a group mass of $M=(3-10)\times 10^{13}$ M$_{\odot}$, in good agreement with the previous estimate derived through weak lensing analysis. Finally, by inverting the HST/ACS I$_{814}$ image with the lensing equation, we obtain the reconstructed image of the magnified source galaxy, which has a scale of about 3.3 kpc at $z_s=2$ (2.7 kpc at $z_s=4$) and the typical disturbed disk-like appearance observed in low-mass star-forming galaxies at $z\sim3$. However, deep, spatially resolved spectroscopic data for similar lensed sources are still required to detected the first stage of galaxy evolution, since the available spectrum shows no clear feature due to the background source.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
