Influence of radiative pumping on the HD rotational level populations in diffuse molecular clouds of the interstellar medium
- Question:
- H2 is hardly observed due to the lack of dipole moment. HD is thus a possible way to trace H2. However, the conditions traced by HD are poorly constrained in diffuse molecular clouds.
- Aims:
- To study the excitation of HD rotational level populations in diffuse molecular clouds.
- new method:
- Theoretical calculations.
- progress:
- They find that HD is mainly determined by radiative pumping rather than collision in diffuse molecular clouds, and thus become a more sensitive indicator of the UV radiation intensity.
- note:
- Can HD become a good tracer for the total mass in such an environment?
A Supernova-driven, Magnetically-collimated Outflow as the Origin of the Galactic Center Radio Bubbles
- Question:
- A pair of non-thermal radio bubbles recently discovered in the inner few hundred parsecs of the Galactic center bears a close spatial association with elongated, thermal X-ray features called the X-ray chimneys. While the morphology, position, and orientation vividly point to an outflow from the Galactic center, the physical processes responsible for the outflow remain to be understood.
- Aims:
- To study the origin of the bubbles in GC.
- new method:
- They performed simulations.
- progress:
- They find that a hot gas outflow can naturally form and acquire a vertically elongated shape due to collimation by the magnetic pressure. an initial magnetic field strength of 80 microG and a supernova rate of 1 kyr−1 can well reproduce the observed morphology, internal energy and X-ray luminosity of the bubbles after an evolutionary time of 330 kyr. Inside the bubbles, mutual collisions between the shock waves of individual supernova remnants produce dense filaments of locally amplified magnetic field.
ALMA reveals a cloud-cloud collision that triggers star formation in N66N of the Small Magellanic Cloud
- Question:
- The formation of massive stars in low metallicity galaxy SMC (~0.2 Zsun) is not well known. N66 is a massive star formation region, suitable to study high mass star formation. Star formation in N66 is still poorly understood.
- Aims:
- To study star formation in N66.
- new method:
- ALMA CO (1-0) observations of N66N region in SMC.
- progress:
- They find that this is the first case of identified cloud-cloud (or two filament) collisions in SMC.
The Perseus ALMA Chemistry Survey (PEACHES). I. The Complex Organic Molecules in Perseus Embedded Protostars
- Question:
- It is known that chemical enrichment in COMs is present in low-mass embedded protostars. However, the statistics of COM abundance in low-mass protostars are limited by the scarcity of observations.
- Aims:
- To study protostellar chemistry statistically.
- new method:
- ALMA observations of 50 selected Class 0/I protostars in Perseus.
- progress:
- They find that the detectability of COMs depends on neither the averaged continuum brightness temperature, a proxy of the H2 column density, nor the bolometric luminosity and the bolometric temperature. The correlation between COMs is insensitive to the protostellar properties, such as the bolometric luminosity and the bolometric temperature.
- note:
- The null results could possible point to the origin of COMs from shocks and grain-chemistry. and it also reminds me of previous surveys of ASAI, CALYPSO, etc.
The Extraordinary Outburst in the Massive Protostellar System NGC6334I-MM1: Spatio-kinematics of Water Masers during a Contemporaneous Flare Event
- Question:
- NGC6334I-MM1 exhibit an eruptive accretion event in which various maser species, including water masers, were triggered. The motions triggered by the burst are seldom investigated.
- Aims:
- To study the motions triggered by the burst
- new method:
- VLBI (KaVA) observations of the embedded H2O masers.
- progress:
- They find that 5 clusters of H2O masers with a mean proper motion of 85 km/s. It forms a major axis to have a position angle of −79.4degree, cutting through the dust cavity around MM1B and aligned in the northwest-southeast direction. We interpret this as the axis of the jet driving the CM2 shock and the maser motion. The post-accretion burst relative proper motions of the H2O masers trace shocks of jet motion.
- note:
- The VLBI follow-up observations of M2O sources will shed light on the episodic accretion of high mass star formations.
- Question:
- The fragment characteristic scale is important for filament formation and evolution. The methods used to determine the fragment scale are important. Different methods need to be tested with simulations to verify the best way to determine the scale.
- Aims:
- To test the different methods to determine the fragmentation in filaments.
- new method:
- They used nearest neighbor separation (NNS), minimum spanning tree (MST), two-point correlation function, Nth nearest neighbor separation, Fourier power spectrum.
- progress:
- The test shows that NNS, MST, and two-point correction function can robustly detec the characteristic fragmentation length-scale.
- note:
- They developed a Python package called FRAGMENT.
- Question:
- Turbulence controls the filament and star formation in molecular clouds. Previous VSF studies only use the two dimensional spatial information and one dimensional velocity information. The full information contain 6D information, so some information may be missing in previous analyses.
- Aims:
- To study turbulence via VSF.
- new method:
- They use the Gaia stars to construct the 6D information, because the young stars retain the memory of turbulence of their natal molecular clouds.
- progress:
- They divide the stars in Orion into several regions, and found that the slope is flatter in presence of compressing sources like supernovae and cluster. This is the first case of use 6D information to construct VSF.