Martin Bureau

Abstract:

As part of the mm-Wave Interferometric Survey of Dark Object Masses (WISDOM) project, we present an estimate of the mass of the supermassive black hole (SMBH) in the nearby fast-rotating early-type galaxy NGC 4697. This estimate is based on Atacama Large Millimeter/submillimeter Array (ALMA) cycle-3 observations of the 12CO(2–1) emission line with a linear resolution of 29 pc (0.53 arcsec). We find that NGC 4697 hosts a small relaxed central molecular gas disc with a mass of 1.6 × 107 M⊙, co-spatial with the obscuring dust disc visible in optical Hubble Space Telescope imaging. We also resolve thermal 1 mm continuum emission from the dust in this disc. NGC 4697 is found to have a very low molecular gas velocity dispersion, σgas = 1.65+0.68−0.65 km s^−1. This seems to be partially because the giant molecular cloud mass function is not fully sampled, but other mechanisms such as chemical differentiation in a hard radiation field or morphological quenching also seem to be required. We detect a Keplerian increase of the rotation of the molecular gas in the very centre of NGC 4697, and use forward modelling of the ALMA data cube in a Bayesian framework with the KINematic Molecular Simulation (KINMS) code to estimate an SMBH mass of (1.3+0.18−0.17) × 108 M⊙ and an i-band mass-to-light ratio of 2.14+0.04−0.05M⊙/L⊙ (at the 99 per cent confidence level). Our estimate of the SMBH mass is entirely consistent with previous measurements from stellar kinematics. This increases confidence in the growing number of SMBH mass estimates being obtained in the ALMA era.

Abstract:

As a part of the mm-Wave Interferometric Survey of Dark Object Masses (WISDOM) project, we present an estimate of the mass of the supermassive black hole (SMBH) in the nearby fast-rotator early-type galaxy NGC 3665. We obtained the Combined Array for Research in Millimeter Astronomy (CARMA) B and C array observations of the 12CO(J = 2 − 1) emission line with a combined angular resolution of 0.59 arcsec. We analysed and modelled the three-dimensional molecular gas kinematics, obtaining a best-fitting SMBH mass MBH=5.75+1.49−1.18×10^8 M⊙, a mass-to-light ratio at H-band (M/L)H = 1.45 ± 0.04 (M/L)⊙,H and other parameters describing the geometry of the molecular gas disc (statistical errors, all at 3σ confidence). We estimate the systematic uncertainties on the stellar M/L to be ≈0.2 (M/L)⊙,H, and on the SMBH mass to be ≈0.4 × 108 M⊙. The measured SMBH mass is consistent with that estimated from the latest correlations with galaxy properties. Following our older works, we also analysed and modelled the kinematics using only the major-axis position–velocity diagram, and conclude that the two methods are consistent.

Abstract:

We present dynamical measurements for 586 Hα-detected star-forming galaxies from the KMOS (K-band Multi-Object Spectrograph) Redshift One Spectroscopic Survey (KROSS). The sample represents typical star-forming galaxies at this redshift (z = 0.6-1.0), with a median star formation rate of ≈7 M ⊙ yr -1 and a stellar mass range of log (M * [M ⊙ ]) ≈ 9-11. We find that the rotation velocity-stellar mass relationship (the inverse of the Tully- Fisher relationship) for our rotationally dominated sources (v C /σ 0 > 1) has a consistent slope and normalization as that observed for z = 0 discs. In contrast, the specific angular momentum (j * angular momentum divided by stellar mass) is ≈0.2-0.3 dex lower on average compared to z = 0 discs. The specific angular momentum scales as j s ∝ M * 0.6±0.2 , consistent with that expected for dark matter (i.e. j DM ∝ M DM 2/3 ). We find that z≈ 0.9 star-forming galaxies have decreasing specific angular momentum with increasing Sérsic index. Visually, the sources with the highest specific angular momentum, for a given mass, have the most disc-dominated morphologies. This implies that an angular momentum-mass-morphology relationship, similar to that observed in local massive galaxies, is already in place by z ≈ 1.