My research asks how dense gas turns into massive stars and clusters, and why the process behaves differently in the Central Molecular Zone (CMZ), the inner few hundred parsecs of the Milky Way. I use ALMA, SMA, VLA, GBT, JCMT, IRAM 30m, CSO, and related data to connect cloud-scale gas dynamics with dense cores, outflows, disks, magnetic fields, and feedback.
Current Themes
Dense gas and star formation in the CMZ
The CMZ has abundant dense molecular gas, but many clouds form stars inefficiently. I work on tracing young embedded star formation and dense-core mass fractions to understand when the dense-gas star formation relation breaks down.
Fragmentation and mass growth
Interferometric observations now resolve massive protoclusters into cores, disks, streamers, and outflows. These data test how massive stars assemble mass after the initial core-fragmentation stage.
Magnetic fields in dense clouds
ALMA polarization observations make it possible to compare magnetic-field geometry with turbulence, gravity, and filamentary gas structures in Galactic Center clouds.
Survey-scale context
CONCERT connects deep observations of selected clouds with wide-field programs such as CMZoom, ACES, and JACKS, linking chemistry, temperature, density, and star formation activity across the CMZ.
Recent Projects and Collaborations
- CONCERT: Coordinated Observations of Nebulae in the Central Molecular Zone Exploring gas Recycling and Transformation links cloud-scale structure to filaments, dense cores, magnetic fields, disks, streamers, and protostellar feedback. Its focused subprojects include QUARTET, MAZURKA, POLKA, BALLAD, CHORUS, and DUET (Dual-band Unified Exploration of Three CMZ Clouds).
- Sgr C massive protostar: In Lu et al. 2026, ALMA resolves a Keplerian disk and two-arm streamer feeding system around an early O-type protostar in Sgr C, offering a direct view of mass delivery to a massive star in the CMZ.
- ALMA disk comparison: An interactive slider compares two observing epochs of a protostellar disk in the CMZ.
- ACES: The ALMA Central Molecular Zone Exploration Survey provides high-resolution molecular-line and continuum data for systematic comparisons among CMZ clouds; Paper IV presents intermediate-resolution spectral-line products.
- CMZ magnetic fields: ALMA polarization observations of the 20 km/s Cloud probe magnetic-field morphology in two massive clumps and connect field geometry with cloud structure.
Does the dense-gas star formation relation break in the CMZ?
The CMZ contains more than 107 solar masses of molecular gas with high mean densities, yet its overall star formation rate is lower than expected from dense-gas star formation relations. This makes the CMZ a nearby laboratory for testing how turbulence, tides, magnetic fields, and time-dependent cloud evolution regulate star formation.
Using VLA and SMA observations, I characterized embedded star formation with H2O masers and free-free emission from ultracompact HII regions toward major CMZ clouds. In Lu et al. 2019, I developed a Monte Carlo approach to estimate recent star formation rates from these short-timescale indicators.
- Several CMZ clouds remain about an order of magnitude below dense-gas star formation expectations, while Sgr B2 and Sgr C are closer to the relation.
- The star formation rates correlate with the mass in gravitationally bound cores on roughly 0.2 pc scales.
- Low bound-core mass fractions may reflect strong turbulence and/or early dynamical stages before large-scale collapse becomes efficient.
Filaments, gas flows, and the growth of massive cores
A central question in massive star formation is whether dense cores form with most of their final mass or continue to grow through accretion along filaments. In Lu et al. 2018, I studied a sample of filamentary high-mass star-forming regions selected from NH3 velocity gradients and followed up with SMA observations.
Potential gas flows into dense cores were identified through NH3 kinematics, implying accretion rates of order 10-4 solar masses per year. At those rates, typical cores can grow substantially over several free-fall times, supporting a picture where filament-fed accretion helps build high-mass stars.
Surveys and Coordinated Campaigns
CONCERT
CONCERT follows four representative CMZ clouds from roughly 100 pc context to 100 AU disk scales. Its observations and homogenized reanalysis connect gas structure, shocks, cores, outflows, magnetic fields, and accretion. DUET is a CONCERT subproject that compares matched 1.3 mm and 3 mm observations across three of these clouds.
CMZoom
I have been involved in the SMA Legacy Survey CMZoom, which mapped major CMZ clouds with the Submillimeter Array.
ACES
ACES extends ALMA mapping of the CMZ with rich molecular-line coverage, supporting cloud-by-cloud studies of chemistry, kinematics, and star formation.
JACKS
I am heavily involved in the JVLA Ammonia CMZ K-band Survey (JACKS) and serve as its data lead. JACKS maps ammonia and related tracers to characterize gas temperature, kinematics, and dense structures across the CMZ.