研究目的
To determine the redshift (or stringent lower limits) of a number of bright BL Lacs objects.
研究成果
The spectroscopic observations of bright BL Lacs indicate that these objects are likely sources with extremely beamed nuclear emission. Simulations show that the next generation of extremely large optical telescopes may allow the detection of very weak absorptions to probe this hypothesis further.
研究不足
The high quality of the spectra and the extended spectral range did not allow the detection of intrinsic spectral features for the sources, limiting the study to providing lower limits to their redshift.
1：Experimental Design and Method Selection:
Optical and near-infrared medium-resolution spectra of four bright BL Lac objects were secured using the spectrograph X-Shooter at the ESO-VLT.
2：Sample Selection and Data Sources:
The targets were selected based on their brightness and unknown redshift.
3：List of Experimental Equipment and Materials:
X-Shooter spectrograph at ESO-VLT was used.
4：Experimental Procedures and Operational Workflow:
Observations were carried out in service mode using the standard NODDING mode for accurate sky subtraction. Data reduction was performed by the X-Shooter data reduction pipeline.
5：Data Analysis Methods:
The minimum detectable equivalent width (EW) was computed to search for spectral features. The absence of features allowed for the derivation of stringent lower limits to the redshift.
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