The broad-line region and dust torus size of the Seyfert 1 galaxy PGC50427

TL;DR

This study uses three years of monitoring data to measure the sizes of the broad-line region and dust torus in the Seyfert 1 galaxy PGC50427, confirming the AGN unified model and providing black hole mass estimates.

Contribution

First simultaneous reverberation mapping of both the broad-line region and dust torus in PGC50427, demonstrating the spatial relationship between these regions in an AGN.

Findings

BLR size lag of 19 days for Hα emission.

Dust torus lag of 46 days in NIR bands.

Black hole mass estimated at approximately 17 million solar masses.

Abstract

We present the results of a three years monitoring campaigns of the $z = 0.024$ type-1 active galactic nucleus (AGN) PGC50427. Through the use of Photometric Reverberation Mapping with broad and narrow band filters, we determine the size of the broad-line emitting region by measuring the time delay between the variability of the continuum and the H$\alpha$ emission line. The H$\alpha$ emission line responds to blue continuum variations with an average rest frame lag of $19.0 \pm 1.23$ days. Using single epoch spectroscopy we determined a broad-line H$\alpha$ velocity width of 1020 km s$^{-1}$ and in combination with the rest frame lag and adoption a geometric scaling factor $f = 5.5$, we calculate a black hole mass of $M_{BH} \sim 17 \times 10^{6} M_{\odot}$. Using the flux variation gradient method, we separate the host galaxy contribution from that of the AGN to calculate the rest frame 5100\AA~ luminosity at the time of our monitoring campaign. The rest frame lag and the host-subtracted luminosity permit us to derive the position of PGC50427 in the BLR size -- AGN luminosity diagram, which is remarkably close to the theoretically expected relation of $R \propto L^{0.5}$. The simultaneous optical and NIR ($J$ and $K_{s}$) observations allow us to determine the size of the dust torus through the use of dust reverberation mapping method. We find that the hot dust emission ($\sim 1800K$) lags the optical variations with an average rest frame lag of $46.2 \pm 2.60$ days. The dust reverberation radius and the nuclear NIR luminosity permit us to derive the position of PGC50427 on the known $\tau - M{V}$ diagram. The simultaneus observations for the broad-line region and dust thermal emission demonstrate that the innermost dust torus is located outside the BLR in PGC50427, supporting the unified scheme for AGNs. (Abstract shortened, see the manuscript.)