As most of the molecular clouds are filamentary and elongated, the magnetic fields (B-fields) in these clouds are found either parallel or perpendicular to the main axes. In the talk, I will present the B-fields mapped in IRDC G34.43+0.24 using 850 micron polarized dust emission observed with the POL-2 instrument at JCMT. We examine the magnetic field geometries and strengths in the northern, central, and southern regions of the filament. The overall field geometry is ordered and aligned closely perpendicular to the filament's main axis, particularly in regions containing the central clumps MM1 and MM2, whereas MM3 in the north has field orientations aligned with its major axis. The overall field orientations are uniform at large (POL-2 at 14” and SHARP at 10”) to small scales (TADPOL at 2.5” and SMA at 1.5”) in the MM1 and MM2 regions. The SHARP/CSO observations in MM3 at 350 micron from Tang et al. show a similar trend as seen in our POL-2 observations. TADPOL observations demonstrate a well-defined field geometry in MM1/MM2 consistent with MHD simulations of accreting filaments. We obtained a plane-of-sky magnetic field strength of 470+/-190 micG, 100+/-40 micG, and 60+/-34 micG in the central, northern and southern regions of G34, respectively, using the updated Davis-Chandrasekhar-Fermi relation. The estimated value of field strength, combined with column density and velocity dispersion values available in the literature, suggests G34 to be marginally critical with criticality parameter values 0.8+/-0.4, 1.1+/-0.8, and 0.9+/-0.5 in the central, northern, and southern regions, respectively. The turbulent motions in G34 are sub-Alfvénic with Alfvénic Mach numbers of 0.34+/-0.13, 0.53+/-0.30, and 0.49+/-0.26 in the three regions. The observed aligned B-fields in G34.43+0.24 are consistent with theoretical models suggesting that B-fields play an important role in guiding the contraction of the cloud driven by gravity. I will also discuss some of my ongoing projects where I am investigating the dust grain characteristics such as heating, radiative alignment, and collisional disalignment of grains.
The Fermi Gamma-ray Space Telescope with its main instrument onboard,
the Large Area Telescope, opened a new era in the study of high-energy
emission from Active Galactic Nuclei. When combined with contemporaneous
ground- and space-based observations, Fermi-LAT achieves its full
capability to characterize the jet structure and the emission mechanisms
at work in different classes of radio-loud AGN, i.e. blazars, radio
galaxies and narrow-line Seyfert 1 galaxies.
In this talk I will discuss the broad-band properties of
gamma-ray-emitting AGN, highlighting major findings and open questions
regarding the jet physics, cosmological evolution, and accretion
processes of super-massive black holes in the Fermi era.
Furthermore, I will discuss the perspectives for future studies of
relativistic jets in AGN with the Large Synoptic Survey Telescope from
near-infrared to ultraviolet and the Cherenkov Telescope Array at Very
European Solar Telescope: Recent progress
The main goal of EST is the simultaneous observation of the solar photosphere and chromosphere to understand the complex interaction between the plasma and the magnetic field. The drastic changes in the plasma beta parameter between these two layers affect drastically the way this interaction takes place and has profound implications on the required spatial and temporal scales of the observations, as well as on the polarimetric sensitivity that is needed to adequately detect the polarization signals. In this talk, we will summarize the most stringent requirements and how the suite of instruments of EST have been defined. A number of recent instrumental and numerical developments carried out by members of the project have paved the way for the practical implementation of novel instruments that will make possible for EST to be at the frontier of technological development since first light. These have especial relevance in the field of adaptive optics, integral field units and applications of neural networks. In this talk, all these concepts will be revised, together with the timeline of the project.
TITLE2: Impact of partial ionization on the solar atmosphere
The partial ionization of the solar atmosphere has been receiving increasing attention in recent years. The presence of neutrals can, for instance, modify the equilibrium of magnetic structures, introduce instabilities under certain magnetic configurations, lead to plasma heating, or change the way the various wave modes transform into each other and propagate through the atmosphere. These are aspects that, in some cases, have been studied in simple scenarios to find analytical expressions that determine the plasma and the field behavior. More recently, advanced numerical simulations have allowed to gain insight into them with more complex magnetic and plasma configurations. Under an observational point of view, there is little evidence of these phenomena or of the potential decoupling between the neutral and ionized species in some circumstances. With the advent of new large aperture telescopes, some of these effects may be observable. In this talk, I will comment some observational and numerical results obtained by the IAC group related to the impact of partial ionization on solar phenomena.
The next decade will see the arrival of three 30m-class Extremely Large Telescopes (ELTs). These giants are promising profound transformation of our understanding of the universe through large-scale surveys of a myriad of previously unseen astronomical objects across vast areas of sky and cosmic space-time. To carry out such surveys, the ELTs must have i) a super-efficient wide-field corrector (WFC) that can expand their field of view (FOV) over a broad wavelength range and ii) highly multiplexed multi-object spectrographs to target a number of objects simultaneously. The McDonald Observatory (MDO) has a strong heritage not only in designing and building traditional astronomical instruments, but also in developing novel instruments and technologies that are directly scalable to the ELT-class wide field survey sciences. I will highlight some of the scientific opportunities brought forth by the ELT Wide-Field MOS (WfMOS) capability and the MDO’s instrument programs that can enable such capability in the era of ELTs and beyond.
The evaluation of the global atmospheric structure, variation, and loss rate is key to a better understanding of the physics that drives the current state of the Martian atmosphere. Operating for more than 2 Mars years, the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission has provided an unprecedented opportunity to study the spatial and temporal variability of the Martian upper atmosphere and ionosphere and their interaction with the solar wind under both nominal and disturbed conditions. One of the primary goals of the MAVEN mission is to characterize the atmospheric loss rates at Mars and understand the relations between those escape rates and solar drivers. Among the dominant atmospheric loss processes, photochemical escape is the major loss process of heavy atomic species, where the escape rate is not directly measured by MAVEN, requiring numerical models to constrain. This talk will present comprehensive modeling efforts of photochemical escape process and formation of the hot atomic coronae at Mars for various atmospheric conditions. The talk will also present the observed and modeled characteristics of the Martian upper atmosphere and ionosphere, that are relevant to the photochemical escape process.
The studies of planet formation have been heavily dominated by theoretical work because observing planets in formation was not possible. The situation is however gradually changing. Thanks to increasingly powerful observing facilities and techniques, we are now able to peer into the birthplaces of planets – so-called circumstellar disks – and routinely find signatures hinting at, and for a few systems direct evidence of, on-going planet formation. In this talk I will introduce how planet formation theories are being tested with and improved by observational data. In particular, I will present a specific example PDS 70, a 5-million-year-old young star surrounded by a disk of gas and dust with two accreting giant protoplanets detected across a broad range of wavelengths from optical to millimeter, offering a perfect test bed for planet-disk interaction and planet formation theories.
천문학은 우리 역사에 깊이 관여돼 있다. 그 중요성은 라대일 박사와 박창범 박사가 『단군세기』에서 ‘戊辰五十年五星聚婁’ 기록을 발굴하고 이를 천문학적으로 증명하면서 크게 부각됐다. 이것은 ‘BC 1733년 오성이 루 주위에 모였다’ 같이 해석되는 단군조선시대의 천문기록이다. 이런 사실이 우리 역사에 미치는 영향에 대해 알아보기로 한다. 또한 지금까지 우주의 역사는 대부분 서양의 관점에서 기술됐다는 점도 짚고 넘어가기로 한다. 가장 좋은 예가 교육과정에서 서양의 아리스토텔레스 4원소는 가르치면서 동양의 태호복희 5원소는 가르치지 않는다는 것이다. 그 결과 대한민국 국민 대부분이 학창시절 태극기의 원리를 제대로 배우지 못했다. 최소한의 태극기에 대한 지식도 알아보기로 한다.
Planet formation is the process where dust grains grow to pebbles,
planetesimals, and rocky planets or cores of gas giant planets in
protoplanetary disks. The process as well as the planetary properties
such as masses can be imprinted in disks, thus obtaining the detailed
disk structure is central to understand how the planet forming activity
proceeds in the entire regions of the disks. I will review the recent
results of disk observations mainly with the Atacama Large
Millimeter/submillimeter Array (ALMA). The fine disk
structures/substructures have been resolved with about 5-au resolution
of ALMA in dust continuum, and those images often show that the disks
consist of concentric annuli, or sometimes show the spiral arms or
strong non-axisymmetry. Combined also with the gas observations,
plausible mechanisms to explain those structures include the trapping of
dust particles at the local pressure maxima and the disk-planet