Abstract
ABSTRACT The mass scaling relation between supermassive black holes and their host spheroids has previously been described by a quadratic or steeper relation at low masses (105 < M bh/M ⊙ ≲ 107). How this extends into the realm of intermediate-mass black holes (102 < M bh/M ⊙ < 105) is not yet clear, although for the barred Sm galaxy LEDA 87300, Baldassare et al. recently reported a nominal virial mass of M bh = 5 × 104 M ⊙ residing in a “spheroid” of stellar mass equal to 6.3 × 108 M ⊙. We point out, for the first time, that LEDA 87300 therefore appears to reside on the near-quadratic M bh–M sph,* relation. However, Baldassare et al. modeled the bulge and bar as the single spheroidal component of this galaxy. Here we perform a 3-component bulge+bar+disk decomposition and find a bulge luminosity which is 7.7 times fainter than the published “bulge” luminosity. After correcting for dust, we find that M bulge = 0.9 × 108 M ⊙ and M bulge/M disk = 0.04—which is now in accord with ratios typically found in Scd–Sm galaxies. We go on to discuss slight revisions to the stellar velocity dispersion (40 ± 11 km s−1) and black hole mass ( M bh = 2.9 − 2.3 + 6.7 × 10 4 f 2.3 M ⊙ ?> ) and show that LEDA 87300 remains consistent with the M bh–σ relation, and also the near-quadratic M bh–M sph,* relation when using the reduced bulge mass. LEDA 87300 therefore offers the first support for the rapid but regulated (near-quadratic) growth of black holes, relative to their host bulge/spheroid, extending into the domain of intermediate-mass black holes.
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