NGC 4395 is a bulgeless spiral galaxy , harboring one of the nearest known type 1 Seyfert nuclei .
Although there is no consensus on the mass of its central engine , several estimates suggest it to be one of the lightest massive black holes ( MBHs ) known .
We present the first direct dynamical measurement of the mass of this MBH from a combination of two-dimensional gas kinematic data , obtained with the adaptive optics assisted near infrared integral field spectrograph Gemini/NIFS , and high-resolution multiband photometric data from Hubble Space Telescope ’ s Wide Field Camera 3 ( HST /WFC3 ) .
We use the photometric data to model the shape and stellar mass-to-light ratio ( M/L ) of the nuclear star cluster .
From the Gemini/NIFS observations , we derive the kinematics of warm molecular hydrogen gas as traced by emission through the H _ { 2 } 1–0 S ( 1 ) transition .
These kinematics show a clear rotational signal , with a position angle orthogonal to NGC 4395 ’ s radio jet .
Our best fitting tilted ring models of the kinematics of the molecular hydrogen gas contain a black hole with mass M = 4 _ { -3 } ^ { +8 } \times 10 ^ { 5 } M _ { \odot } ( 3 \sigma uncertainties ) embedded in a nuclear star cluster of mass M = 2 \times 10 ^ { 6 } M _ { \odot } .
Our black hole mass measurement is in excellent agreement with the reverberation mapping mass estimate of Peterson et al .
( 2005 ) , but shows some tension with other mass measurement methods based on accretion signals .