Reverberation mapping of the broad-line region in NGC 5548: evidence for radiation pressure?
- Department of Astronomy, Beijing Normal University, Beijing 100875 (China)
- Key Laboratory for Particle Astrophysics, Institute of High Energy Physics,Chinese Academy of Sciences, 19B Yuquan Road, Beijing 100049 (China)
- 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, Vol. 827, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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