arXiv subjects

PeiZhen Cheng

Publications and source records attributed to PeiZhen Cheng.

3 recordsLinked to original sources

arXiv2025

AGN-Driven Biconical Outflows as the Origin of the Double-Peaked [O~{\sc iii}] doublet in SDSS J134733.36+121724.27

In this manuscript, we recheck the spectroscopic properties of SDSS J134733.36+121724.27 (4C+12.50), confirming the presence of the double-peaked [O~{\sc iii}]$λ\lambda4959,5007$Å doublet and a broad H$α$. The former likely results from AGN-driven biconical outflows, while the absence of a broad H$β$ supports a classification of the source as a Type-1.9 AGN. We analyze its high-quality Sloan Digital Sky Survey (SDSS) optical spectrum after robustly subtracting host galaxy and AGN continuum contributions through a simple stellar population fitting method employing 39 templates and a power-law continuum. Each narrow line of the [O~{\sc iii}]$λ\lambda4959,5007$Å doublet is better described by two Gaussian components (blue-shifted and red-shifted) than by a single Gaussian, as confirmed by the F-test. Broad components are included for both H$α$ and H$β$, but only H$α$ reveals a significant detection, further supported by a comparison between the SDSS spectrum and that previously reported. These results support that the object is highly consistent with a Type-1.9 AGN classification, and the double-peaked [O~{\sc iii}] profiles are most likely produced by AGN-driven biconical outflows rather than by a rotating narrow-line region or a dual AGN merger system. Additional observations are still needed to strengthen these conclusions.

astro-ph.GA↗

arXiv2025

An improved Seyfert-LINER classification line in the [N~{\sc ii}] BPT diagram

In this manuscript, an improved Seyfert-LINER classification line (= S-L line) is proposed in the [N~{\sc ii}] BPT diagram, based on a sample of 47,968 low redshift narrow emission line galaxies from SDSS DR16, motivated by different S-L lines reported in the [N~{\sc ii}] BPT diagram through different methods. The method proposed by Kewley et al. in 2006 is firstly applied, however, the method cannot lead to an accepted S-L line in the [N~{\sc ii}] BPT diagram. Meanwhile, the S-L lines proposed by Schawinski et al. in 2007 and Cid Fernandes et al. in 2010 in the [N~{\sc ii}] BPT diagram are different from each other. Therefore, it is meaningful to check which proposed S-L line is better or to determine an improved one in the [N~{\sc ii}] BPT diagram by a new method. In this manuscript, Seyferts and LINERs that have already been classified in the [S~{\sc ii}] and/or [O~{\sc i}] BPT diagrams can be visualized in the [N~{\sc ii}] BPT diagram, leading the intersection boundary of the two contour maps to be considered as the S-L line in the [N~{\sc ii}] BPT diagram. Rather than the previously proposed S-L lines, the new S-L line can lead to more efficient and harmonious classifications of Seyferts and LINERs, especially in the composite galaxy region, in the [N~{\sc ii}] BPT diagram. Furthermore, based on the discussed S-L lines, the number ratio of Type-2 Seyferts to Type-2 LINERs differs significantly from that of Type-1 Seyferts to Type-1 LINERs in the [N~{\sc ii}] BPT diagram, suggesting that about 90$\%$ of Type-2 LINERs are non-AGN-related objects, true Type-2 AGNs, or objects exhibiting both Seyfert and LINER characteristics.

astro-ph.GA↗

arXiv2021

Long-term variability of the composite galaxy SDSS J103911-000057: A candidate of true Type-2 AGN

In the manuscript, the composite galaxy SDSS J103911-000057 (=SDSS J1039) is reported as a better candidate of true Type-2 AGN without hidden BLRs. None broad but only narrow emission lines detected in SDSS J1039 can be well confirmed both by the F-test technique and by the expected broad emission lines with EW smaller than 13.5Å~ with 99\% confidence level. Meanwhile, a reliable AGN power law component is preferred with confidence level higher than 7sigma in SDSS J1039. Furthermore, the long-term variability of SDSS J1039 from CSS can be well described by the DRW process with intrinsic variability timescale $τ\sim100{\rm days}$, similar as normal quasars. And, based on BH mass in SDSS J1039 through the msig relation and on the correlation between AGN continuum luminosity and total H$α$ luminosity, the expected broad H$α$, if there was, could be re-constructed with line width about $300-1000{\rm km~s^{-1}}$ and with line flux about $666\times10^{-17}{\rm erg~s^{-1}~cm^{-2}}$ under the Virialization assumption to BLRs, providing robust evidence to reject the probability that the intrinsic probable broad H$α$ were overwhelmed by noises of the SDSS spectrum in SDSS J1039. Moreover, the SDSS J1039 does follow the same correlation between continuum luminosity and [O~{\sc iii}] line luminosity as the one for normal broad line AGN, indicating SDSS J1039 classified as a changing-look AGN at dim state can be well ruled out. Therefore, under the current knowledge, SDSS J1039 is a better candidate of true Type-2 AGN.

astro-ph.GA↗