Comparisons of quiescent galaxies in the distant universe with their counterparts in the local volume show that the structure of galaxies continues to change well after they stop forming stars. Very compact galaxies, that have the stellar mass of the Milky Way and the size of the Milky Way bulge, seem to disappear between redshifts z~2 and z~0. The average size of quiescent population increases by a factor of a few over the same redshift interval. In contrast to the existing surveys of high-redshift universe, at intermediate redshift (0.2 < z < 1)
Polarimetry is established as the third eye of humankind into the Universe, complementing photometry and spectroscopy. Dust and magnetic fields are ubiquitous the Universe and widely thought to play crucial roles in many astrophysical processes, from star formation and stellar feedback to planet formation, molecule formation, and life. Polarization of light induced by alignment of dust grains with magnetic fields is a leading tool for illuminating the dusty and magnetized universe from the UV-optical-NIR to far-IR and (sub-)mm wavelengths. The most powerful observatories (ALMA, NOEMA, IRAM/Nika2-Pol, SOFIA/HAWC+, JCMT/Pol2, APEX/A-mKID, TolTec, BLASTPOL) are providing a vast amount of polarization data, which promise to shed light on the fundamental dust physics (e.g., grain alignment and rotational disruption) as well as the key role of dust and magnetic fields in many astrophysical processes. In this talk, I will comprehensively review the current state-of-the-art of our theoretical frameworks, computational tools, and observational constraints of dust physics and magnetic field properties using multi-wavelength polarization data. I will then introduce a new technique for probing 3D magnetic fields using dust polarization and our grain alignment theory.
Here I would like to introduce the NRF project “A study on the evolutionary process of late-type stars through maser observations” (called SMASTES: Simultaneous Multi-mAser Survey Toward Evolved Stars) which has been starting since Sept. 2022 with a three year plan. SMASTES aims to study statistically characteristics of SiO and H2O maser properties in ~150 M-type oxygen-rich AGB, ~150 S-type AGB and ~150 post-AGB stars according to evolutionary stage using the upgraded wide four-band receiving system of the KVN. In addition to the existing main observation lines of 22 GHz H2O and 43/42/86/129 GHz (v = 1, 2, J = 1-0; v = 1, J = 2-1, J = 3-2) SiO masers, the SiO v = 3, J = 1-0; v = 2, J = 2-1, 3-2; 28SiO v = 0, J = 1-0, 2-1, 3-2; 29SiO v = 0, J = 1-0, 2-1; 30SiO v = 0, J = 1-0 lines are further observed simultaneously together with CS, HCN, SiS, SO, and SO2 thermal lines. Observations toward ~155 oxygen-rich AGB stars (SMASTES I) were completed between Feb. and June 2023. For observational studies on ~155 S-type stars (SMASTES II), the observations are being carried out by the KVN 2023B proposal since September of this year. The observational proposal for ~150 post-AGB stars (SMASTES III) was submitted for the KVN 2024A season. Through these observations, the characteristics of maser properties, chemical trends associated with characteristics of maser properties, SiO abundance and dust formation etc. will be explored according to the oxygen-rich AGB, S-type AGB, and post-AGB phases. A kinematic acceleration of mass loss and asymmetric outflows from the central star to atmosphere → dust layer → outer circumstellar envelope are also investigated during the evolution of early AGB, thermal pulse late AGB, and post-AGB stars. In particular, observational studies on S-type AGB stars with C/O≈1 as a transitional phase from oxygen-rich to carbon-rich stars and post-AGB stars as a transitional phase from AGB stars to planetary nebulae, which have not been studied much so far, will be focused.
As the frequency of electromagnetic waves becomes lower, the signal can penetrate deeper into the sea, while the installation and operation costs get higher. That is why only some of the developed countries operate Very-Low-Frequency (VLF) transmitters that can be used for sending electromagnetic signals to submersible vehicles. This talk will give a brief introduction to the effects of VLF transmitter signals on ionospheric cold plasma and energetic particles coming from the magnetosphere. We also review the signatures captured by Korean satellites, such as NextSat-1. Finally, we discuss the possible contribution of the recently launched SNIPE fleet to this topic.
The ESA mission Gaia is regularly scanning the sky since 2014.5 down to magnitude V≈20.7, and its 4th harvest has just been published with the recent Gaia Focus Product Release. I will first give a brief review of the Gaia mission, its status, observations, instruments and data releases. Next, we will see some of the scientific results obtained for asteroids, focusing on astrometry and photometry. We will expose in particular the improvement on asteroid orbital solutions obtained within the FPR. Last, we will touch upon synergy with ground-based observations, and promises for the study on the dynamics of Solar System Objects.
galactic nuclei are extreme environments where stars are densely packed around a supermassive black hole (SMBH). Occasionally, dynamical interactions in the galactic center lead the stars to interact violently at short distances with each other or with the SMBH, resulting in the formation of nuclear transients. In this talk, I will discuss two types of nuclear transients, tidal disruption events and high-velocity collisions between stars, based on the results of detailed hydrodynamics simulations. Tidal disruption events are one of the most dramatic nuclear transients in which a star is tidally disrupted by the SMBH in a few hours. The conventional picture has been that a star is fully disrupted at the first pericenter passage and the debris circularizes rapidly. However, these events are in fact more diverse and they can be categorized into several groups with different observational signatures depending on stellar pericenter distance, from partial disruptions (i.e., partial mass loss and surviving remnant) to full disruptions which is further sub-categorized depending on relativistic effects. On the other hand, disruptive collisions are the events where two stars collide at a very high relative velocity near the central SMBH. The collision product, a homologously expanding gas cloud, can generate a flare as bright as tidal disruption events. Subsequently, the expanding gas cloud would interact with the nearby SMBH, generating a second, possibly even brighter accretion-driven flare. Because these can happen near BHs at any mass scale, if the accretion is efficient, these disruptive collisions could contribute to the growth of black holes.
A GPU (Graphic Processing Unit) spectrometer for the ALMA (Atacama Large Millimeter/submillimeter Array) Total Power Array has been developed by the KASI and the NAOJ (National Astronomy Observatory of Japan). It is a first in-kind contribution of the KASI to the ALMA international collaboration. The development project went through a series of milestones, from a concept design review in 2016 to commission and science verification in 2023. During the ALMA maintenance period of February 2022, the GPU spectrometer was installed in a technical building at the Array Operation Site by its developers from the KASI and the NAOJ. Right after the installation, SiO (J=2-1; v=1) 86 GHz maser spectral lines toward the Orion KL region were successfully detected using the spectrometer. The spectrometer will be used from the ALMA Cycle 10 (October 2023) for science observations.