A5070021012- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Astrophysical Phenomena and Observations
- Astrophysics and Cosmic Phenomena
- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Astronomical Observations and Instrumentation
- Gamma-ray bursts and supernovae
- Radio Astronomy Observations and Technology
- Dark Matter and Cosmic Phenomena
- Pulsars and Gravitational Waves Research
- Cosmology and Gravitation Theories
- Solar and Space Plasma Dynamics
- History and Developments in Astronomy
- Scientific Research and Discoveries
- Particle Accelerators and Free-Electron Lasers
- Atomic and Molecular Physics
- Advanced X-ray Imaging Techniques
- Neutrino Physics Research
- Gyrotron and Vacuum Electronics Research
- Experimental and Theoretical Physics Studies
- Adaptive optics and wavefront sensing
- Spectroscopy and Laser Applications
- Astro and Planetary Science
- Atmospheric Ozone and Climate
National Central University
2015-2024
Institute of Astronomy
1995-2023
National Taiwan University
2023
Korea Research Institute of Standards and Science
2022
Micron (United States)
2018
University of Malaya
2018
European Southern Observatory
2018
Max Planck Institute for Radio Astronomy
2013
Institute of Astronomy and Astrophysics, Academia Sinica
1997-2013
Academia Sinica
1997-1999
The central region of the Coma cluster galaxies was observed in energy band from 0.065 to 0.245 kiloelectron volts by Deep Survey telescope aboard Extreme Ultraviolet Explorer. A diffuse emission halo angular diameter approximately 30 arc minutes detected. extreme-ultraviolet (EUV) level exceeds that expected x-ray temperature gas Coma. This suggests presence two more phases emitting gas, one at a 2 x 10(6) kelvin and other 8 10(5) kelvin. latter phase cools rapidly and, steady state, would...
An observation of M87, the central galaxy Virgo Cluster, was performed by deep survey telescope aboard Extreme-Ultraviolet Explorer, in 0.065-0.245 keV energy band. A point source and an extended emission halo radius ~20' are clearly visible data, represent first detection cluster gas EUV. The cannot be explained well-known at X-ray temperatures. Instead, it is necessary to introduce a second component, with temperature between 5 × 105 106 K. rapid cooling plasmas such temperatures implies...
The excess extreme-ultraviolet (EUV) emission detected in the Virgo and Coma clusters is explained by inverse Compton scattering of cosmic microwave background photons, which are scattered relativistic electrons that account for extended radio synchrotron these clusters. lower limits average magnetic fields estimated from EUV close to equipartition derived observations, indicating electron energies field might be equipartition. suggests energy reservoirs approximately 10(61) 10(60) ergs...
The interaction between a supermassive black hole (SMBH) and the surrounding material is of primary importance in modern astrophysics. detection molecular 2-pc circumnuclear disk (CND) immediately around Milky Way SMBH, SgrA*, provides an unique opportunity to study SMBH accretion at sub-parsec scales. Our new wide-field CS(2-1) map toward Galactic center (GC) reveals multiple dense streamers originated from ambient clouds 20-pc further out, connecting central 2 parsecs CND. These gas appear...
Understanding the formation of supermassive black holes (SMBHs) present in centers galaxies is a crucial topic modern astrophysics. Observations have detected SMBHs with mass $M$ $10^{9}\, \rm M_\odot$ high-redshift $\rm z\sim7$. However, how grew to such huge masses within first billion years after big bang remains elusive. One possible explanation that grow quickly through frequent mergers galaxies, which provides sustainable gas maintain rapid growth. This study presents hydrodynamics...
Abstract We present the Atacama Large Millimeter/Sub-millimeter Array (ALMA) cycle-0 science verification data of CO(1–0) line emission in central region NGC 4321 (also known as M100) at distance 17.1 Mpc and VLA, L-band HI same galaxy. have drawn center area M100 12 CO(J = 1–0) with resolution (3.87″ × 2.53″) viewed by ALMA, along Spitzer 8 3.6 μm data. The relationship between surface density molecular gas mass ∑H 2 that star formation rate ∑SFR has been investigated, addition to neutral...
Different models have been used to evaluate the interfacial Dzyaloshinskii-Moriya interaction (DMI) from asymmetric bubble expansion method using magneto-optics. Here we investigate most promising candidates over a range of different magnetic multilayers with perpendicular anisotropy. Models based on standard creep hypothesis are not able reproduce domain wall (DW) velocity profile when DW roughness is high. Our results demonstrate that and interface sample layers correlated. Furthermore,...
Aims.The stochastic acceleration of subrelativistic electrons from a background plasma is studied in order to find possible explanation the hard X-ray emission detected Coma cluster.
We present the first interferometric HCN(J = 3-2) and HCO+(J maps in circumnuclear region of NGC 1097, obtained with Submillimeter Array. The goal is to study characteristics dense gas associated starburst ring/Seyfert nucleus. With these transitions, we suppress diffuse low density emission nuclear region. detect resolve individual compact giant molecular cloud associations (GMAs) 1.4 kpc ring within 350 pc nucleus brighter than both lines, contributes ~20% ~30% total detected flux, central...
Abstract We present confusion-limited SCUBA-2 450 μ m observations in the COSMOS-CANDELS region as part of James Clerk Maxwell Telescope Large Program Ultra Deep Imaging EAO Survey. Our maps at and 850 cover an area arcmin 2 . achieved instrumental noise levels σ = 0.59 mJy beam −1 0.09 deepest each map. The corresponding confusion are estimated to be 0.65 0.36 Above 4 (3.5 ) threshold, we detected 360 (479) sources 237 (314) m. derive blank-field number counts m, covering flux-density range...
We investigate theoretical models for the radio halo and hard X-ray (HXR) excess in Coma galaxy cluster. Time-independent time-dependent reacceleration relativistic electrons have been carried out to study formation of HXR excess. In these models, are injected by merger shocks reaccelerated ensuing violent turbulence. The effects different Mach numbers on emission also investigated. adopt 6 μG as central magnetic field reproduce observed spectra via synchrotron emission. obtain a "plateau"...
We report the detection of X-ray pulsations with a period ~315.87 ms from 2009 XMM-Newton observation for radio-quiet gamma-ray pulsar, LAT PSR J0007+7303, centered in supernova remnant CTA 1. The detected pulsed is consistent periodicity at same epoch found Fermi Gamma-ray Space Telescope. broader sinusoidal structure folded light curve emission dissimilar to that emission, and phase peak about 0.5 shifting bands, indicating main component X-rays originates different sites pulsar. conclude...
Distant luminous quasars provide important information on the growth of first supermassive black holes, their host galaxies and epoch reionization. The identification is usually performed through detection Lyman-$α$ line redshifted to $\sim$ 0.9 microns at z>6.5. Here, we report discovery a very quasar, PSO J006.1240+39.2219 redshift z=6.618, selected based its red colour multi-epoch emission in single near-infrared band. Lyman-$α$-line luminosity unusually high estimated be...
We investigated the properties of host galaxies active galactic nuclei (AGNs). used radio emission around to represent AGN activity and infrared (IR) star-forming stellar population galaxies. determined that have higher masses (SMs) within central kiloparsec radius than normal do independent Hubble types galaxies; but both exhibit similar specific star formation rates (SSFRs), ranging between yr−1. find SM surface density might be as an indicator identify AGNs. also discovered certain AGNs...
We report mid-infrared observations of several luminous infrared galaxies (LIGs) carried out with the Infrared Space Observatory. Our sample was chosen to represent different phases a merger sequence galaxy-galaxy interaction special emphasis on early/intermediate stages merging. The emission these LIGs shows extended structures for early and intermediate mergers, indicating that most luminosities are not from central active galactic nucleus. Both hardness (indicated by IRAS 12, 25, 60 μm...
We investigate the evolution and number distribution of radio halos in galaxy clusters. Without reacceleration or regeneration, relativistic electrons responsible for diffuse emission will lose their energy via inverse Compton synchrotron losses a rather short time, have lifetimes ~0.1 Gyr. Radio could last ~Gyr if significant level is involved. The would be comparable with cosmological time radio-emitting are mainly secondary generated by pion decay following proton-proton collisions...
view Abstract Citations (21) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Extreme Ultraviolet Spectrum of the BL Lacertae Object PKS 2155-304 Koenigl, Arieh ; Kartje, John F. Bowyer, Stuart Kahn, Steven M. Hwang, Chorng-Yuan We carried out two spectroscopic observations object 2155 - 304 with Explorer during 1993 June (∼111 ks) and July (∼157 ks). source was detected in ∼75-110 Å range both epochs, but spectra differ detail, flux has...
The multiconfiguration relativistic random-phase-approximation theory is applied to autoionizing levels of the neutral zinc atom between 4${\mathit{s}}_{1/2}$ and 4${\mathit{p}}_{3/2}$ ionization thresholds. There are five Rydberg series doubly excited states that manifest themselves as autoionization resonances in 4s photoionization cross section. Theoretical predictions for positions profiles excellent agreement with experiment.
We investigate the ionization mechanisms for hidden broad-line region (HBLR) and non-HBLR Seyfert 2 galaxies by comparing some optical emission line ratios. note that [N ii] λ6583/Hα ratio of is significantly higher than HBLR while other ratios, such as [O iii]/Hβ i]/Hα, are similar. To probe origin this difference, we explore theoretical results different models, photoionization, starburst, shock models. find none these models can explain high with solar abundance; must be reproduced from...
We report on a 105-ks Suzaku observation (obsid 404011010 with J. Takata as PI) of the supernova remnant CTA 1 (G119.5+10.2). The soft X-ray was carried out using both timing and imaging modes. A ∼10-arcmin extended feature, which is interpreted bow-shock component pulsar wind nebula, revealed in this deep for first time. nebular spectrum can be modelled by power law photon index ∼1.8, suggests slow synchrotron cooling scenario. approximately constant across feature. compare our observations...
Abstract We report the discovery of BL Lacertae object FIRST J233153.20+112952.11 at redshift >6 using near-infrared spectroscopy and broadband observations in infrared, submillimeter, radio wavelengths. The detection continuum break ∼0.92 μ m spectrum provides an approximate 6.57, corresponding to age universe ∼800 Myr. rest-frame UV/optical shows no emission lines detected with equivalent width >1.5 Å. nondetection C iv λ 1549 broad line constrains luminosity accretion disk be ≲10 45...
We carried out a spectroscopic observation of the BL Lacertae object Mrk 421 with Extreme Ultraviolet Explorer (EUVE) over an 11 day period in 1995 late April to early May (~242 ks useful time). During this period, source underwent flare that was detected also X-rays and TeV γ-rays. The best continuous coverage obtained by EUVE, which resolved smooth rise fall flux, measuring variability as much factor ~1.5 span ~2 days. spectrum extended from ~65 100 Å could be fitted power law energy...
We present high-resolution (~2'') H I 21 cm and CO(1-0) observations of the quasar (QSO) galaxy pair 0248+430. The QSO Q0248+430 (zem = 1.313) has been found to show two metal absorption-line systems at redshifts za ~ 0.052, which are consistent with redshift a foreground luminous infrared 15'' (~11 h-1 kpc) away. In our observations, CO emission this galaxy, G0248+430, shows broad velocity distribution (~173 km s-1) but is spatially confined small unresolved region less than 1.5 × kpc; H2...