- Published on 19 November 2020
4. Extragalactic astronomy
The spatially resolved broad line region of IRAS 09149-6206
The GRAVITY collaboration reports on near-infrared interferometric spectra of the Br-gamma line, resolving the broad line region (BLR) of a nearby active galaxy nucleus (AGN). They are able to measure the size of the BLR (radius 0.075pc) and estimate the mass of the black hole (10^8 M_sun). These results are compatible with average values that have been measured in nearby AGNs through reverberation mapping as well as with the standard M_BH-sigma relation. A surprising result is the 0.14 pc offset between the BLR and the centroid of the hot dust distribution, which is traced by the 2.3 micron continuum. The hot dust is thought to be distributed in a ring, with a measured radius of 0.35 pc, since the high temperature inside the ring sublimates the dust. The offset falls well inside the ring and is thought to be due to the brightness asymmetry of the ring. A clear velocity gradient, almost perpendicular to the offset, is interpreted as the Keplerian rotation of the BLR.