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Intermediate-mass black holes and the fundamental plane of black hole accretion

G├╝ltekin, Kayhan; Nyland, Kristina; Gray, Nichole; et al.

eprint arXiv:2209.09890

We present new 5 GHz VLA observations of a sample of 8 active intermediate-mass black holes with masses $10^{4.9} < M < 10^{6.1} M_{odot}$ found in galaxies with stellar masses $M_{*} < 3 times 10^{9} M_{odot}$. We detected 5 of the 8 sources at high significance. Of the detections, 4 were consistent with a point source, and one (SDSS J095418.15+471725.1, with black hole mass $M < 10^{5} M_{odot}$) clearly shows extended emission that has a jet morphology. Combining our new radio data with the black hole masses and literature X-ray measurements, we put the sources on the fundamental plane of black hole accretion. We find that the extent to which the sources agree with the fundamental plane depends on their star-forming/composite/AGN classification based on optical narrow emission line ratios. he single star-forming source is inconsistent with the fundamental plane. The three composite sources are consistent, and three of the four AGN sources are inconsistent with the fundamental plane. We argue that this inconsistency is genuine and not a result of misattributing star-formation to black hole activity. Instead, we identify the sources in our sample that have AGN-like optical emission line ratios as not following the fundamental plane and thus caution the use of the fundamental plane to estimate masses without additional constraints, such as radio spectral index, radiative efficiency, or the Eddington fraction.

5 panels of VLA radio maps, showing four point-source detections and one extended source.

Radio maps of all five detected sources from our programme. For each panel, the name of each source is indicated in the top left, the synthesized beam is shown in the bottom right, and a scale bar indicating 1┬ákpc at the distance of the source is shown in the bottom left. The colour scale is different for each panel and is indicated by the colourbar at the right of each panel given in units of Jy. Contours are drawn for panel at levels of Ôłĺ1 (dashed), 2, 3, 5, 10, 20, 30, 50, and 80 times the map rms. All sources plotted are clearly detected at high significance and are consistent with a single point source except for SDSS J0954+4717, which shows clearly extended emission.

4 panels showing various fundamental plane fits with data that mostly disagree.