Reverberation mapping of the broad-line region in NGC 5548: evidence for radiation pressure?

Journal Article · Sat Aug 20 04:00:00 EDT 2016 · Astrophysical Journal

DOI:https://doi.org/10.3847/0004-637X/827/2/118· OSTI ID:22868773

Lu, Kai-Xing; Bi, Shao-Lan ^[1]; Du, Pu; Hu, Chen; Li, Yan-Rong; Zhang, Zhi-Xiang; Wang, Kai; Huang, Ying-Ke; Wang, Jian-Min ^[2]; Bai, Jin-Ming ^[3]

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1. Department of Astronomy, Beijing Normal University, Beijing 100875 (China)
2. Key Laboratory for Particle Astrophysics, Institute of High Energy Physics,Chinese Academy of Sciences, 19B Yuquan Road, Beijing 100049 (China)
3. Yunnan Observatory, Chinese Academy of Sciences, Kunming 650011, Yunnan (China)

NGC 5548 is the best-observed reverberation-mapped active galactic nucleus with long-term, intensive monitoring. Here we report results from a new observational campaign between 2015 January and July. We measure the centroid time lag of the broad Hβ emission line with respect to the 5100 Å continuum and obtain τ{sub cent}=7.20{sub −0.35}{sup +1.33} days in the rest frame. This yields a black hole mass of M{sub ∙}=8.71{sub −2.61}{sup +3.21}×10{sup 7}M{sub ⊙} using a broad Hβ line dispersion of 3124 ± 302 km s{sup −1} and a virial factor of f{sub B{sub L{sub R}}}=6.3±1.5 for the broad-line region (BLR), consistent with the mass measurements from previous Hβ campaigns. The high-quality data allow us to construct a velocity-binned delay map for the broad Hβ line, which shows a symmetric response pattern around the line center, a plausible kinematic signature of virialized motion of the BLR. Combining all the available measurements of Hβ time lags and the associated mean 5100 Å luminosities over 18 campaigns between 1989 and 2015, we find that the Hβ BLR size varies with the mean optical luminosity, but, interestingly, with a possible delay of 2.35{sub −1.25}{sup +3.47} years. This delay coincides with the typical BLR dynamical timescale of NGC 5548, indicating that the BLR undergoes dynamical changes, possibly driven by radiation pressure.

• OSTI ID: 22868773
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 827; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
BLACK HOLES
DISPERSIONS
EMISSION
GALAXIES
GALAXY NUCLEI
LUMINOSITY
MASS
RADIATION PRESSURE
SYMMETRY
VELOCITY