Hai Ngo Ngoc

Overview

Understanding the origin of black hole seeds – whether from Population III stellar remnants ("light seeds") or the direct collapse of primordial gas clouds ("heavy seeds") – remains a central motivation in modern astrophysics, since the seeding channel largely determines how quickly a black hole can grow into the multi-million or billion solar-mass objects observed at low and high redshift alike. Distinguishing between these channels requires black hole mass measurements across the full range of galaxy environments, from small star clusters to giant ellipticals.

My Research

I target the low-mass end of this problem by searching for intermediate-mass black holes hiding in the nuclear star clusters of dwarf and low-mass early-type galaxies. Using end-to-end mock observations for ELT/HARMONI and dynamical modelling of the resulting stellar kinematics, I aim to recover black hole masses and test whether these clusters formed in situ or through the inspiral of migrated star clusters – a direct probe of the seeding and early-growth stage of black hole evolution.

Overview

Black holes span an enormous range of masses, yet intermediate-mass black holes (10³–10⁶ M_☉) remain the most elusive population, sitting in the observational gap between stellar-mass remnants and supermassive black holes. Filling this gap is essential for building a continuous picture of black hole demographics and for testing whether the relations that govern supermassive black holes extend down to much smaller systems.

My Research

I lead dynamical mass measurements across this spectrum using two complementary tracers. With JWST/NIRSpec and NIRCam, I built a Python pipeline to separate AGN continuum emission from stellar light, enabling accurate stellar-kinematic mass measurements that I have applied to the supermassive black holes in NGC 4258 and M87. In parallel, I model ALMA molecular-gas datacubes with KinMS to determine black hole masses in NGC 7052, NGC 4061, NGC 2513, and Circinus, extending the census toward the intermediate-mass end.

Overview

The tight correlations observed between black hole mass and host-bulge properties, such as stellar velocity dispersion and luminosity, suggest that black holes and galaxies do not evolve independently but instead influence one another's growth, plausibly through feedback processes. Testing this coevolution picture requires dynamical mass measurements spanning a wide range of galaxy masses, morphologies, and cosmic epochs.

My Research

My measurements of black hole masses in galaxies ranging from dwarf systems to massive ellipticals, using both stellar kinematics (JWST) and molecular-gas kinematics (ALMA), directly populate the black hole-galaxy scaling relations. Combining these dynamical masses with independent bulge-property measurements lets me test where individual galaxies sit relative to the mean relation and what that implies for their shared assembly history.

Overview

Dynamical black hole mass measurements depend entirely on accurately recovering the kinematics of stars or gas orbiting within a black hole's sphere of influence, which demands high angular resolution and careful modelling techniques such as Jeans anisotropic modelling and multi-Gaussian expansion fitting. Advancing these techniques toward fainter, more distant, or more crowded targets is central to progress in the field.

My Research

I apply and develop a full kinematic and dynamical modelling pipeline – including MGE fitting, JAM, pPXF, and image reduction with IRAF – to extract stellar and gas kinematics from JWST/NIRSpec and NIRCam imaging, ALMA molecular-gas datacubes modelled with KinMS, and mock HARMONI/MICADO observations, in order to recover reliable dynamical masses across all of my target systems.

Overview

Because instruments such as ELT/HARMONI and MICADO are not yet operational, realistic mock observations and simulators are the primary tool for anticipating their scientific capabilities, identifying detection limits, and designing efficient observing strategies well before first light.

My Research

Using the HARMONI Simulator (HSIM) and the MICADO simulator (SimCADO), together with KinMS for molecular-gas modelling, I simulate mock IFS datacubes and imaging of dwarf galaxies and star clusters to recover intermediate-mass black hole masses from dynamical modelling, design observing strategies for detecting IMBH kinematic signatures within 20 Mpc, and quantify the limitations of HARMONI for this science case.