Research
The full list of my research publications is available in this ADS library.
NIRCam WFSS Data Processing Notebook & Calibrations on Github
A publicly available, step-to-step notebook on the reduction of JWST/NIRCam grism spectral data Code Data
SAPPHIRES (JWST Cycle-3 GO-6434) Early Data Release on Github
We present the early data release (EDR) of Slitless Areal Pure-Parallel HIgh-Redshift Emission Survey (SAPPHIRES), a JWST Cycle-3 Treasury imaging and spectroscopic survey using the powerful NIRCam wide-field slitless spectroscopic (WFSS) mode in pure parallel. SAPPHIRES will obtain NIRCam imaging and WFSS data in many cosmological deep fields totaling a telescope charged time of 709 hours (557-hour exposures). In this EDR, we present NIRCam imaging and WFSS data obtained in parallel to the Frontier Field galaxy cluster MACS J0416.1–2403, which are attached to primary observations JWST-GO-4750...
Data Paper
SAPPHIRES: Extremely Metal-Poor Galaxy Candidates with 12 + log(O/H) \(< 7.0\) at \(z \sim 5 − 7\) from Deep JWST/NIRCam Grism Observations
We search for galaxies with low R3=[O III] \(\lambda\)5008/H\(\beta\) ratios as part of the JWST Cycle-3 large treasury program, the Slitless Areal Pure-Parallel HIgh-Redshift Emission Survey (SAPPHIRES). Using deep NIRCam Wide-Field Slitless Spectrscopy (WFSS) data, we report the discovery of seven extremely metal-poor galaxy candidates in the SAPPHIRES Early Data Release (EDR) field, with estimated 12 + log(O/H) \(<\) 7.0 at \(z \sim 5 − 7\), including two sources with 12 + log(O/H) \(<\) 6.7 (\(Z < 1\% Z_\odot\)), significantly breaking the metallicity floor observed both locally and at high redshift...
Paper Student-leading
The Large-scale Environments of Low-luminosity AGNs at 3.9<z<6 and Implications for Their Host Dark Matter Halos from a Complete NIRCam Grism Redshift Survey
We study the large-scale environments and clustering properties of 28 low-luminosity AGNs at \(z=3.9−6\) in the GOODS-N field. Our sample, identified from the JWST NIRCam Imaging and WFSS data in CONGRESS and FRESCO surveys with either broad H\(\alpha\) emission lines or V-shape continua, are compared to 782 H\(\alpha\) emitters (HAEs) selected from the same data. These AGNs are located in diverse large-scale environments and do not preferentially reside in denser environments compared to HAEs...
Paper Student-leading
Abundant Population of Broad H\(\alpha\) Emitters in the GOODS-N Field Revealed by CONGRESS, FRESCO, and JADES
We present a spectroscopic search for broad H(\alpha\) emitters at z~3.7-6.5 in the GOODS-N field, utilizing JWST/NIRCam slitless spectroscopy from FRESCO and CONGRESS, complemented by JADES imaging. We identify 19 broad H(\alpha\) emitters with FWHM>1000 km/s at \(z\sim4-5.5\), including 9 new sources. We find that 42% of the sample do not satisfy the widely-used color selection criteria for Little Red Dots (LRDs), with the majority of these sources lacking the characteristic steep red slope...
Paper Student-leading
The First Photometric Evidence of a Transient/Variable Source at z>5 with JWST
The James Webb Space Telescope (JWST) discovered 79 transients out to \(z\sim4.8\) through the JADES Transient Survey (JTS), but the JTS did not find any \(z>5\) transients. Here, we present the first photometric evidence of a \(z>5\) transient/variable source with JWST. The source, AT 2023adya, resides in a \(z_\mathrm{spec} = 5.274\) galaxy in GOODS-N, which dimmed from mF356W=26.05\(\pm\)0.02 mag to 26.24\(\pm\)0.02 mag in the rest-frame optical over approximately two rest-frame months, producing a clear residual signal in the difference image (\(m_{\rm F356W}=28.01\pm0.17\) mag) at the galaxy center...
Paper Student-leading
The Luminosity Function and Clustering of H\(\alpha\) Emitting Galaxies at z≈4-6 from a Complete NIRCam Grism Redshift Survey
We study the luminosity function (LF) and clustering properties of 888 Hα emitters (HAEs) at \(3.75 < z < 6\) in the GOODS-N field. The sample, built from JWST CONGRESS and FRESCO NIRCam grism surveys using a novel redshift assignment algorithm, spans ˜62 arcmin22 and reaches \(L_{\rm Hα} \sim 10^{41.2} {\rm erg s^{-1}}\). We identify two prominent filamentary protoclusters at \(z \approx 4.41\) and \(z \approx 5.19\), hosting 98 and 144 HAEs, respectively....
Paper Student-leading
MAGNIF: Spectroscopic Census of H\(\alpha\) Luminosity Functions and Cosmic Star Formation at z ~ 4.5 and 6.3
We measure H\(\alpha\) luminosity functions (LFs) at redshifts z∼4.5 and 6.3 using the JWST MAGNIF (Medium-band Astrophysics with the Grism of NIRCam In Frontier fields) survey. We identify 248 H\(\alpha\) emitters based on the grism spectra and photometric redshifts from combined HST and JWST imaging data. The numbers of the H\(\alpha\) emitters show a large field-to-field variation, highlighting the necessity of multiple fields to mitigate cosmic variance...
Paper Student-leading
ASPIRE: Spectroscopically Complete Census of Obscured Cosmic Star Formation Rate Density at z=4–6
We present a stringent measurement of the dust-obscured star formation rate density (SFRD) at z = 4–6 from the ASPIRE JWST Cycle-1 medium and ALMA Cycle-9 large program. We obtained JWST/NIRCam grism spectroscopy and ALMA 1.2 mm continuum map along 25 independent quasar sightlines, covering a total survey area of ∼35 arcmin2 where we search for dusty star-forming galaxies (DSFGs) at z=0–7....
Paper
NEXUS Early Data Release: NIRCam Imaging and WFSS Spectroscopy from the First (Partial) Wide Epoch
We present the Early Data Release of the Multi-Cycle JWST-NEXUS Treasury program (2024-2028), which includes NIRCam imaging and WFSS observations from the first (partial) NEXUS-Wide epoch covering the central 100 arcmin2 of the NEXUS field, located near the North Ecliptic Pole and within the Euclid Ultra-Deep Field...
Data Paper
Identification of High-Redshift Galaxy Overdensities in GOODS-N and GOODS-S
We conduct a systematic search for high-redshift galaxy overdensities at 4.9<zspec<8.9 in both the Great Observatories Origins Deep Survey (GOODS)-N and GOODS-S fields using James Webb Space Telescope/Near-Infrared Camera (JWST/NIRCam) imaging from the JWST Advanced Deep Extragalactic Survey and JWST Extragalactic Medium-band Survey in addition to JWST/NIRCam wide field slitless spectroscopy from the First Reionization Epoch Spectroscopic Complete Survey...
Paper Student-leading
Identification of more than 40 gravitationally magnified stars in a galaxy at redshift 0.725
Strong gravitational magnification enables the detection of faint background sources and allows researchers to resolve their internal structures and even identify individual stars in distant galaxies. Highly magnified individual stars are useful in various applications, including studies of stellar populations in distant galaxies and constraining dark matter structures in the lensing plane. However, these applications have been hampered by the small number of individual stars observed, as typically one or a few stars are identified from each distant galaxy. Here, we report the discovery of more than 40 microlensed stars in a single galaxy behind Abell 370 at redshift of 0.725 (dubbed "the Dragon arc") when the Universe was half of its current age, using James Webb Space Telescope observations with the time-domain technique...
Paper Media Coverage
JADES: Discovery of an Extreme Galaxy Overdensity at z = 5.4 with JWST/NIRCam in GOODS-S
We report the discovery of an extreme galaxy overdensity at z = 5.4 in the GOODS-S field using James Webb Space Telescope (JWST)/NIRCam imaging from JADES and JEMS alongside JWST/NIRCam wide-field slitless spectroscopy from FRESCO. We identified potential members of the overdensity using Hubble Space Telescope+JWST photometry spanning \(\lambda\)=0.4–5.0 µm. These data provide accurate and well-constrained photometric redshifts down to m∼29–30 mag. We subsequently confirmed N=81 galaxies at 5.2<z<5.5 using JWST slitless spectroscopy over \(\lambda\)=3.9–5.0 µm through a targeted line search for H\(\alpha\) around the best-fit photometric redshift...
Paper Student-leading
JADES: Resolving the Stellar Component and Filamentary Overdense Environment of HST-dark Submillimeter Galaxy HDF850.1 at z = 5.18
HDF850.1 is the brightest submillimeter galaxy (SMG) in the Hubble Deep Field. It is known as a heavily dust-obscured star-forming galaxy embedded in an overdense environment at z=5.18. With nine-band NIRCam images at 0.8-5.0 µm obtained through the JWST Advanced Deep Extragalactic Survey, we detect and resolve the rest-frame UV-optical counterpart of HDF850.1, which splits into two components because of heavy dust obscuration in the center...
Paper