研究目的
To spectroscopically confirm gravitationally lensed quasars in the Southern Sky discovered using new techniques from the DES and KiDS-DR3 surveys, and to provide their properties such as redshifts, photometry, and lens model parameters.
研究成果
Five out of seven targeted lensed quasar candidates were spectroscopically confirmed, with a success rate of ～70%, consistent with forecasts. The range of source redshifts and Einstein radii aligns with theoretical predictions. The techniques used are effective for discovering bright lenses, but strategies for fainter lenses are needed. Future work should focus on securing deflector redshifts and measuring time delays for cosmological applications.
研究不足
The spectroscopic run was mostly weathered out, limiting observations to only seven candidates. Faint traces of lensing galaxies in spectra prevented secure deflector redshift identification. The brightness of confirmed lenses is at the bright end, indicating that fainter lenses remain undiscovered. Photometric redshift uncertainties affect time delay predictions.
1：Experimental Design and Method Selection:
The study involved selecting high-grade lensed quasar candidates from the DES and KiDS-DR3 surveys using astrometric offset techniques and visual inspection. Spectroscopic follow-up was conducted using the NTT-EFOSC2 instrument to confirm the lenses. Data reduction used standard ESO pipelines, and redshift determination involved Gaussian fitting to emission lines. Lens modeling employed a Singular Isothermal Sphere with external shear (SIS + XS) model.
2：Sample Selection and Data Sources:
Seven candidates were selected based on astrometric offsets between DES/Gaia or KiDS/Gaia coordinates, with visual inspection via the NCSA-DES cut-out server. Data came from DES, KiDS, WISE, and Gaia surveys.
3：List of Experimental Equipment and Materials:
NTT-EFOSC2 spectrograph on the New Technology Telescope (NTT), PYRAF package for image analysis, GALFIT for photometry, and SDSS-DR14 for photometric redshift comparison.
4：Experimental Procedures and Operational Workflow:
Candidates were observed with 20-minute integrations per target under stable seeing conditions. Spectra were reduced, de-blended using Gaussian profiles, and analyzed for emission lines to determine redshifts. Photometry was performed using PSF fitting in g, r, i bands. Lens models were fitted to astrometric data.
5：Data Analysis Methods:
Redshifts were determined by Gaussian fitting to emission lines with error estimation via resampling. Photometric redshifts for deflectors were estimated by comparing colors with SDSS galaxies. Lens parameters were derived using χ2 minimization.
独家科研数据包，助您复现前沿成果，加速创新突破
获取完整内容
