Published works
Title: Inadequate turbulent support in low-metallicity molecular clouds
Abstract: The dynamic properties of molecular clouds are set by the interplay of their self-gravity, turbulence, external pressure, and magnetic field. Among them, the turbulent kinetic energy (Ek) and the self-gravitational energy (Eg) are usually thought to be in the state of virial equilibrium, mainly based on observations around the Solar neighbourhood or in the inner Galaxy. In this work, we present mapping observations of optically-thin 13CO lines, targeting low metallicity molecular clouds from the Galactic outer disk --- the poorly studied part of our Milky Way. By combining samples from the inner Galaxy and nearby metal-poor dwarf galaxies, we find a systematic decline of the cloud virial parameter (2Ek/Eg) towards lower metallicity, reaching sub-virial states where turbulence alone cannot counterbalance the self-gravity of molecular clouds. The magnetic field likely becomes dominant in supporting against the cloud self-gravity under low-metallicity conditions.
Highlight: Evidence of the variation of star formation initial condition with metallicity on scales of molecular clouds.
Implication: Initial conditions of star formation in low metallicity conditions of the early Universe.
Status: Published in Nature Astronomy. Click to see!
Title: Gas dynamics in an AGN-host galaxy at z ≃ 2.6: Regular rotation, noncircular motions, and mass models
Abstract: The gas dynamics of galaxies provide critical insights into the evolution of both baryons and dark matter (DM) across cosmic time. In this context, galaxies at cosmic noon, that is, in the period characterized by the most intense star formation and black hole activities, are particularly significant. We present an analysis of the gas dynamics of PKS 0529–549. This galaxy lies at z ≃ 2.6 and hosts a radio-loud active galactic nucleus (AGN). We used new ALMA observations of the [CI] (2−1) line at a spatial resolution of 0.18′′ (∼1.5kpc). We found that (1) the molecular gas forms a rotation-supported disk with Vrot/σv=6±3 and displays a flat rotation curve out to 3.3 kpc; (2) there are several noncircular components, including a kinematically anomalous structure near the galaxy center, a gas tail to the southwest, and possibly a second weaker tail to the east; and finally, (3) the dynamical estimates of the gas and stellar masses from fitting the rotation curve are inconsistent with photometric estimates made using standard gas conversion factors and stellar population models, respectively. These discrepancies may be due to systematic uncertainties in the photometric masses or in the dynamical masses, or they might be caused by a more massive radio-loud AGN-host galaxy that is hidden behind the gas-rich [CI] emitting starburst galaxy along the line of sight. Our work shows that in-depth investigations of 3D line cubes are crucial for revealing the complexity of gas dynamics in high-z galaxies, in which regular rotation may coexist with noncircular motions and possibly tidal structures.
Highlight: Existence of a dynamically-cold gas disk in an AGN-host starburst radio galaxy.
Implication: Galaxy disks in the early Universe should have an efficient way to dynamically cool down.
Status: Published in Astronomy & Astrophysics. Click to see!
Other Extensions
- Developing a Python-based pipeline to facilitate the FAST data reduction. For more information, visit the project page.
- HI narrow self-absorption (HINSA) in Galactic outer disk molecular clouds
- HI kinematics of the Galactic Anticenter High Velocity Cloud (AC-HVC)
- HI kinematics of the Supernova Remnant IC 443 (SNR IC 443)
- ...