Hansung B. Gim
A5049115462- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Gamma-ray bursts and supernovae
- Stellar, planetary, and galactic studies
- Radio Astronomy Observations and Technology
- Astrophysics and Cosmic Phenomena
- Astronomical Observations and Instrumentation
- Astrophysical Phenomena and Observations
- Particle Accelerators and Free-Electron Lasers
- Astro and Planetary Science
- GNSS positioning and interference
- Geophysics and Gravity Measurements
- Pulsars and Gravitational Waves Research
- Superconducting and THz Device Technology
- Scientific Research and Discoveries
- Particle accelerators and beam dynamics
- Material Science and Thermodynamics
- Methane Hydrates and Related Phenomena
- Quantum, superfluid, helium dynamics
- Cosmology and Gravitation Theories
- CCD and CMOS Imaging Sensors
- Antenna Design and Analysis
- Spacecraft and Cryogenic Technologies
- Phase Equilibria and Thermodynamics
Montana State University
2021-2024
Arizona State University
2018-2024
University of Massachusetts Amherst
2015-2023
Yonsei University
2007-2009
Korea Astronomy and Space Science Institute
2007
We give an overview and describe the rationale, methods, first results from NIRCam images of JWST "Prime Extragalactic Areas for Reionization Lensing Science" ("PEARLS") project. PEARLS uses up to eight filters survey several prime extragalactic areas: two fields at North Ecliptic Pole (NEP); seven gravitationally lensing clusters; high redshift proto-clusters; iconic backlit VV 191 galaxy system map its dust attenuation. also includes NIRISS spectra one NEP NIRSpec high-redshift quasars....
Our current understanding of galaxy evolution still has many uncertainties associated with the details accretion, processing, and removal gas across cosmic time. The next generation radio telescopes will image neutral hydrogen (HI) in galaxies over large volumes at high redshifts, which provide key insights into these processes. We are conducting COSMOS HI Large Extragalactic Survey (CHILES) Karl G. Jansky Very Array, is first survey to simultaneously observe from z=0 z~0.5. Here, we report...
Abstract We report the results of James Webb Space Telescope/NIRCam observations 19 (sub)millimeter sources detected by Atacama Large Millimeter Array (ALMA). The accurate ALMA positions allowed unambiguous identifications their NIRCam counterparts. Taking gravitational lensing into account, these represent 16 distinct galaxies in three fields and constitute largest sample its kind to date. counterparts’ spectral energy distributions cover from rest-frame ultraviolet near-IR provide...
Abstract The James Webb Space Telescope (JWST) North Ecliptic Pole (NEP) Time-domain Field (TDF) is a >14′ diameter field optimized for multiwavelength time-domain science with JWST. It has been observed across the electromagnetic spectrum both from ground and space, including Hubble (HST). As part of HST observations over three cycles (the “TREASUREHUNT” program), deep images were obtained Wide Camera on Advanced Surveys in F435W F606W that cover almost entire JWST NEP TDF. Many...
About 25% of the Milky Way globular clusters (GCs) exhibit unusually extended color distribution stars in core helium-burning horizontal-branch (HB) phase. This phenomenon is now best understood as due to presence helium-enhanced second-generation subpopulations, which has raised possibility that these peculiar GCs might have a unique origin. Here we show with HB are clearly distinct from other normal kinematics and mass. The more massive than dominated by random motion no correlation...
ABSTRACT We present the first JWST observations of z = 4.11 luminous radio galaxy TN J1338–1942, obtained as part ‘Prime Extragalactic Areas for Reionization and Lensing Science’ (‘PEARLS’) project. Our NIRCam observations, designed to probe key rest-frame optical continuum emission line features at this redshift, enable resolved spectral energy distribution modelling that incorporates both a range stellar population assumptions radiative shock models. With an estimated mass log10(M/M⊙) ∼...
Direct-collapse black holes (DCBHs) of mass ∼10 4 − 10 5 M ⊙ that form in HI-cooling halos the early Universe are promising progenitors ≳10 9 supermassive fuel observed z ≳ 7 quasars. Efficient accretion surrounding gas onto such DCBH seeds may render them sufficiently bright for detection with JWST up to ≈ 20. Additionally, very steep and red spectral slope predicted across ≈1 μm wavelength range JWST/NIRSpec instrument during their initial growth phase should make photometrically...
Measuring redshifted CO line emission is an unambiguous method for obtaining accurate redshift and total cold gas content of optically faint, dusty starburst systems. Here, we report the first successful spectroscopic determination AzTEC J095942.9+022938 ("COSMOS AzTEC-1"), brightest 1.1mm continuum source found in AzTEC/JCMT survey (Scott et al. 2008), through a clear detection (4-3) (5-4) lines using Redshift Search Receiver on Large Millimeter Telescope. The $z=4.3420\pm0.0004$ confirmed...
Dusty star-forming galaxies (DSFGs) significantly contribute to the stellar buildup in during “cosmic noon,” peak epoch of cosmic star formation. Major mergers and gas accretion are often invoked explain DSFGs’ prodigious formation rates (SFRs) large masses. We conducted a spatially resolved morphological analysis rest-frame ultraviolet/near-infrared (∼0.25–1.3 μm) emission three DSFGs at z ≃ 2.5. Initially discovered as carbon monoxide (CO) emitters by NOrthern Extended Millimeter Array...
Abstract We present a systematic search for radio active galactic nuclei (AGNs) in dwarf galaxies using recent observations taken by the Very Large Array Sky Survey (VLASS). To select these objects, we first establish criterion to identify radio-excess AGNs infrared-radio correlation parameter, q , that describes tight relation between and IR emission star-forming galaxies. find 2 σ threshold of < 1.94 AGNs, which is derived from sample ∼7000 across full mass range NASA-Sloan Atlas have...
The improved sensitivity of interferometric facilities to the 21-cm line atomic hydrogen (HI) enables studies its properties in galaxies beyond local Universe. In this work, we perform a 21 cm spectral stacking analysis combining MIGHTEE and CHILES surveys COSMOS field derive robust HI-stellar mass relation at z=0.36. particular, by thousands star-forming subdivided into stellar bins, optimize signal-to-noise ratio targets mean HI masses different intervals for investigated galaxy...
Abstract The improved sensitivity of interferometric facilities to the 21 cm line atomic hydrogen (H i ) enables studies its properties in galaxies beyond local Universe. In this work, we perform a spectral stacking analysis combining MeerKAT International GigaHertz Tiered Extragalactic Exploration and COSMOS H Large Extra-galactic Survey surveys field derive robust –stellar mass relation at z ≈ 0.36. particular, by thousands star-forming subdivided into stellar bins, optimize...
Utilizing the COSMOS HI Large Extragalactic Survey (CHILES) dataset, we investigate evolution of average atomic neutral hydrogen (HI) properties galaxies over continuous redshift range 0.09 $< z <$ 0.47. First, introduce a simple multi-step, multi-scale imaging and continuum subtraction process that apply to each observing session. These sessions are then averaged onto common \textit{uv}-grid run through Fourier filtering artifact mitigation technique. We demonstrate how this results in...
ABSTRACT We present neutral hydrogen (H i) and ionized α) observations of 10 galaxies out to a redshift 0.1. The H i are from the first epoch (178 h) COSMOS Large Extragalactic Survey (CHILES). Our sample is biased consists late-type with masses that range 1.8 × 107 M⊙ 1.1 1010 M⊙. find although majority show irregularities in morphology kinematics, they generally follow scaling relations found larger samples. α velocities reach flat part rotation curve. identify large-scale structure nearby...
We present a study of 16 HI-detected galaxies found in 178 hours observations from Epoch 1 the COSMOS HI Large Extragalactic Survey (CHILES). focus on two redshift ranges between 0.108 <= z 0.127 and 0.162 0.183 which are among worst affected by radio frequency interference (RFI). While this represents only 10% total coverage 18% expected time source compared to what will be full CHILES survey, we demonstrate that our data reduction pipeline recovers high quality even regions severely...
Abstract We present the first results from deep and wide 5 GHz radio observations of Great Observatories Origins Deep Survey (GOODS)-North ( σ = 3.5 μ Jy beam −1 , synthesized size θ 1.″47 × 1.″42, 52 sources over 109 arcmin 2 ) GOODS-South 3.0 0.″98 0.″45, 88 190 fields using Karl G. Jansky Very Large Array. derive spectral indices α between 1.4 beam-matched images show that overall index distribution is broad even when measured noise flux bias are considered. also find a clustering faint...
Radio free-free emission is considered to be one of the most reliable tracers star formation in galaxies. However, as it constitutes faintest part radio spectrum -- being roughly an order magnitude less luminous than synchrotron at GHz frequencies typically targeted surveys usage a rate tracer has mostly remained limited local Universe. Here we perform multi-frequency stacking analysis using deep Karl G. Jansky Very Large Array observations 1.4, 3, 5, 10 and 34 COSMOS GOODS-North fields...
Abstract Henize 2–10 is a dwarf starburst galaxy hosting ∼10 6 M ⊙ black hole (BH) that driving an ionized outflow and triggering star formation within the central ∼100 pc of galaxy. Here, we present Atacama Large Millimeter/submillimeter Array continuum observations from 99 to 340 GHz, as well spectral line molecules CO (1–0, 3–2), HCN HCO+ with focus on BH its vicinity. Incorporating centimeter-wave radio measurements literature, show energy distribution dominated by synchrotron emission...
Abstract Radio astronomy is undergoing a renaissance, as the next generation of instruments provides massive leap forward in collecting area and therefore raw sensitivity. However, to achieve this theoretical level sensitivity science data products, we need address much more pernicious systematic effects, which are true limitation. These become all significant when consider that time used by survey instruments, such Square Kilometre Array (SKA), will be dedicated deep surveys. CHILES H i...
Abstract We report the discovery of two kinematically anomalous atomic hydrogen (H i ) clouds in M 100 (NGC 4321), which was observed as part Deciphering Interplay between Interstellar medium, Stars, and Circumgalactic medium (DIISC) survey H 21 cm at 3.3 km s −1 spectroscopic 44″ × 30″ spatial resolution using Karl G. Jansky Very Large Array. 15 The National Radio Astronomy Observatory is a facility Science Foundation operated under cooperative agreement by Associated Universities, Inc....
Abstract The Time Domain Field (TDF) near the North Ecliptic Pole in JWST’s continuous-viewing zone will become a premier “blank field” for extragalactic science. JWST/NIRCam data 16 arcmin 2 portion of TDF identify 4.4 μ m counterparts 62 63 3 GHz sources with S (3 GHz) > 5 Jy. one unidentified radio source may be lobe nearby Seyfert galaxy, or it an infrared-faint source. bulk properties radio-host galaxies are consistent those found by previous work: redshifts range from 0.14–4.4...
Abstract We explore the growth of stellar disks in 14 nearby spiral galaxies as part Deciphering Interplay between Interstellar medium, Stars, and Circumgalactic medium (DIISC) survey. study radial distribution specific star formation rates (sSFRs) investigate ratio difference outer inner sSFRs (Δ sSFR = out – ) disk total sSFR, Δ /sSFR, to quantify growth. find /sSFR H i gas fraction show a mild correlation Spearman’s ρ 0.30, indicating that are likely proceed outward galactic with high...
We present our investigation of the Extended Ultraviolet (XUV) disk galaxy, NGC 3344, conducted as part Deciphering Interplay between Interstellar medium, Stars, and Circumgalactic medium (DIISC) survey. use surface aperture photometry individual young stellar complexes to study star formation its effect on physical properties interstellar medium. measure specific star-formation rate (sSFR) find it increase from $\rm10^{-10} yr^{-1}$ in inner $\rm>10^{-8} extended disk. This provides...
Henize 2-10 is a dwarf starburst galaxy hosting $\sim10^{6}~M_{\odot}$ black hole (BH) that driving an ionized outflow and triggering star formation within the central $\sim100$ pc of galaxy. Here we present ALMA continuum observations from 99 to 340 GHz, as well spectral line molecules CO (1-0, 3-2), HCN HCO$^{+}$ with focus on BH its vicinity. Incorporating cm-wave radio measurements literature, show energy distribution dominated by synchrotron emission 1.4 to~340 GHz index...
The JWST North Ecliptic Pole (NEP) Time Domain Field (TDF) is a $>$14 arcmin diameter field optimized for multi-wavelength time-domain science with JWST. Its location within JWST's northern continuous viewing zone offers optimal conditions studies JWST, ensuring year-round observability, absence of bright stars, and minimal Zodiacal foreground interference. It has been observed across the electromagnetic spectrum both from ground space, including Hubble Space Telescope (HST). As part HST...