Optically-Selected BLR-less Active Galactic Nuclei from the SDSS Stripe82 Database I: The Sample

Abstract

This is the first paper in a dedicated series to study the properties of the optically selected BLR-less AGNs (Active Galactic Nuclei with no-hidden central broad emission line regions). We carried out a systematic search for the BLR-less AGNs through the Sloan Digital Sky Survey Legacy Survey (SDSS Stripe82 Database). Based on the spectral decomposition results for all the 136676 spectroscopic objects (galaxies and QSOs) with redshift less than 0.35 covered by the SDSS Stripe82 region, our spectroscopic sample for the BLR-less AGNs includes 22693 pure narrow line objects without broad emission lines but with apparent AGN continuum emission $R_{AGN}>0.3$ and apparent stellar lights $R_{ssp}>0.3$. Then, using the properties of the photometry magnitude RMS ($RMS$) and the Pearson's coefficients ($R_{1,2}$) between two different SDSS band light curves: $RM{S}_k>3\times RM{S}_{M_k}$ and $R_{1,2}>\sim 0.8$, the final 281 pure narrow objects with true photometry variabilities are our selected reliable candidates for the BLR-less AGNs. The selected candidates with higher confidence levels not only have the expected spectral features of the BLR-less AGNs, but also show significant true photometry variabilities. The reported sample at least four-times enlarges the current sample of the BLR-less AGNs, and will provide more reliable information to explain the lack of the BLRs of AGNs in our following studies.

Accepted and to be published in MNRAS. 18 pages, 1 table and 10 figures

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• SDSS J1058+5443: A blue quasar does not have optical/NUV broad emission lines
• Systematic research of low redshift optically selected SDSS Type-2 AGN but with apparent long-term optical variabilities from Catalina Sky Survey, I: data sample and basic results
• Long-term variability of the composite galaxy SDSS J103911-000057: A candidate of true Type-2 AGN
• Are broad optical balmer lines from central accretion disk in PG 1613+658?