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Are there larger stellar velocity dispersions in low redshift Type-1 AGN than in Type-2 AGN?

Astrophysics of Galaxies 2022-05-03 v1

Abstract

The main objective is to check the Unified Model (UM) expected similar stellar velocity dispersions between Type-1 AGN and Type-2 AGN, then to provide further clues on BH mass properties. Not similar as previous comparisons of BH masses estimated by \msig relations to Type-2 AGN but Virial BH masses in Type-1 AGN, reliable stellar velocity dispersions σ\sigma measured through absorption features around 4000\AA~ are directly compared between so-far the largest samples of 6260 low redshift (z < 0.3z~<~0.3) Type-1 AGN and almost all the Type-2 AGN in SDSS DR12. Although half of Type-1 AGN do not have measured σ\sigma due to unapparent absorption features overwhelmed by AGN activities, both properties of mean spectra of Type-1 AGN with and without measured σ\sigma and positive dependence of σ\sigma on [O~{\sc iii}] luminosity can lead to statistically larger σ\sigma of all the Type-1 AGN than the 6260 Type-1 AGN with measured stellar velocity dispersions. Then, direct σ\sigma comparisons can lead to statistically larger σ\sigma in Type-1 AGN, with confidence level higher than 10sigma, after considering necessary effects of different redshift and different central AGN activities. Although Type-1 AGN have σ\sigma only about (9±3)(9\pm3)\% larger than Type-2 AGN, the difference cannot be well explained at current stage. Unless there was strong evidence to support different \msig relations or to support quite different evolution histories between Type-1 AGN and Type-2 AGN, the statistically larger σ\sigma in Type-1 AGN provides a strong challenge to the Unified model of AGN.

Keywords

Cite

@article{arxiv.2205.00194,
  title  = {Are there larger stellar velocity dispersions in low redshift Type-1 AGN than in Type-2 AGN?},
  author = {Zhang XueGuang},
  journal= {arXiv preprint arXiv:2205.00194},
  year   = {2022}
}

Comments

28 pages, 19 figures, 2 tables; Accepted to be published in ApJS