Xihan Ji
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View article: JADES and BlackTHUNDER: rest-frame Balmer-line absorption and the local environment in a Little Red Dot at <i>z</i> = 5
JADES and BlackTHUNDER: rest-frame Balmer-line absorption and the local environment in a Little Red Dot at <i>z</i> = 5 Open
We present a ‘Little Red Dot’ (LRD) broad-line AGN at z = 5.077, observed with NIRSpec/MSA and NIRSpec/IFU by the JADES and BlackTHUNDER surveys. Combining spatially resolved and high-resolution spectroscopy, we characterize its central en…
View article: Overmassive black holes in the early Universe can be explained by gas-rich, dark matter-dominated galaxies
Overmassive black holes in the early Universe can be explained by gas-rich, dark matter-dominated galaxies Open
JWST has revealed the apparent evolution of the black hole (BH)–stellar mass (MBH–M*) relation in the early Universe, while remaining consistent with the BH–dynamical mass (MBH–Mdyn) relation. We predict BH masses for z > 3 galaxies in …
View article: Enhanced search for neutral current <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mi mathvariant="normal">Δ</mml:mi> </mml:math> radiative single-photon production in MicroBooNE
Enhanced search for neutral current radiative single-photon production in MicroBooNE Open
We report results from an updated search for neutral current (NC) resonant Δ ( 1232 ) baryon production and subsequent Δ radiative decay (NC Δ → N γ ). We consider events with and without final state protons; events with a proton can…
View article: JADES reveals a large population of low mass black holes at high redshift
JADES reveals a large population of low mass black holes at high redshift Open
JWST has revealed a large population of active galactic nuclei (AGN) in the distant universe, which are challenging our understanding of early massive black hole (BH) seeding and growth. We expand the exploration of this population to lowe…
View article: A Deep Dive down the Broad-line Region: Permitted O <scp>I</scp> , Ca <scp>II,</scp> and Fe <scp>II</scp> Emission in an Active Galactic Nucleus Little Red Dot at <i>z</i> = 5.3
A Deep Dive down the Broad-line Region: Permitted O <span>I</span> , Ca <span>II,</span> and Fe <span>II</span> Emission in an Active Galactic Nucleus Little Red Dot at <i>z</i> = 5.3 Open
We present a spectroscopic analysis of a broad-line active galactic nucleus (AGN) selected as a little red dot (LRD) at z = 5.3 behind the Bullet cluster (Bz5.3) based on JWST/NIRCam and NIRSpec data. The detection of strong Fe ii , O i , …
View article: BlackTHUNDER – A non-stellar Balmer break in a black hole-dominated little red dot at <i>z</i> = 7.04
BlackTHUNDER – A non-stellar Balmer break in a black hole-dominated little red dot at <i>z</i> = 7.04 Open
Recent observations from James Webb Space Telescope (JWST) have revealed an abundant population of active galactic nuclei (AGNs) and the so-called ‘Little Red Dots’ (LRDs) at $2\lesssim z \lesssim 11$, many of which are characterized by V-…
View article: Measurement of charged-current muon neutrino-argon interactions without pions in the final state using the MicroBooNE detector
Measurement of charged-current muon neutrino-argon interactions without pions in the final state using the MicroBooNE detector Open
We report a new measurement of flux-integrated differential cross sections for charged-current (CC) muon neutrino interactions with argon nuclei that produce no final-state pions (νμCC0π). These interactions are of particular importance as…
View article: JADES-GS-z14-1: A Compact, Faint Galaxy at <i>z</i> ≈ 14 with Weak Metal Lines from Extremely Deep JWST MIRI, NIRCam, and NIRSpec Observations
JADES-GS-z14-1: A Compact, Faint Galaxy at <i>z</i> ≈ 14 with Weak Metal Lines from Extremely Deep JWST MIRI, NIRCam, and NIRSpec Observations Open
JWST has shed light on galaxy formation and metal enrichment within 300 Myr of the Big Bang. While luminous galaxies at z > 10 often show significant [O iii ] λλ 4959, 5007 emission lines, it remains unclear whether such features are preva…
View article: SDSS-IV MaNGA: Data-model discrepancy in temperature-sensitive line ratios for star-forming galaxies
SDSS-IV MaNGA: Data-model discrepancy in temperature-sensitive line ratios for star-forming galaxies Open
Aims . Gas-phase metallicity is a fundamental parameter that helps constrain the star-forming history and chemical evolution of a galaxy. Measuring the electron temperature through auroral-to-strong line ratios is a direct approach to deri…
View article: Measurement of three-dimensional inclusive muon-neutrino charged-current cross sections on argon with the MicroBooNE detector
Measurement of three-dimensional inclusive muon-neutrino charged-current cross sections on argon with the MicroBooNE detector Open
We report the measurement of the triple-differential cross section d3σ/dEvisdcos(θμ)dPμ for inclusive muon-neutrino charged-current scattering on argon. This measurement utilizes data from 6.4×1020 protons on target of exposure collected u…
View article: Irony at z=6.68: a bright AGN with forbidden Fe emission and multi-component Balmer absorption
Irony at z=6.68: a bright AGN with forbidden Fe emission and multi-component Balmer absorption Open
We present the deepest medium-resolution JWST/NIRSpec spectroscopy to date of a bright Little Red Dot (LRD) AGN, Irony at z=6.68. The data reveal broad Balmer emission from H$α$-H$δ$ and Balmer absorption in H$α$-H$ε$. The absorption lines…
View article: BlackTHUNDER: Shedding light on a dormant and extreme little red dot at z=8.50
BlackTHUNDER: Shedding light on a dormant and extreme little red dot at z=8.50 Open
Recent photometric surveys with JWST have revealed a significant population of mysterious objects with red colours, compact morphologies, frequent signs of active galactic nucleus (AGN) activity, and negligible X-ray emission. These 'Littl…
View article: Surprising Increase of Electron Temperature in Metal-Rich Star-Forming Regions
Surprising Increase of Electron Temperature in Metal-Rich Star-Forming Regions Open
Measuring gas-phase metallicity, the relative abundance of elements heavier than helium to the abundance of hydrogen, is essential for constraining the chemical evolution of galaxies. The electron temperature is a crucial parameter for the…
View article: JADES: the chemical enrichment pattern of distant galaxies - silicon depletion and iron enhancement
JADES: the chemical enrichment pattern of distant galaxies - silicon depletion and iron enhancement Open
We present gas-phase abundances of carbon (C), $α$-elements (O, Ne, Si, and Ar) and iron (Fe) obtained from stacked spectra of high-$z$ star-forming galaxies with the deep Near Infrared Spectrograph medium-resolution data from the James We…
View article: Ruling out dominant electron scattering in Little Red Dots’ Rosetta Stone using multiple hydrogen lines
Ruling out dominant electron scattering in Little Red Dots’ Rosetta Stone using multiple hydrogen lines Open
Most little red dots (LRDs) hosting active galactic nuclei (AGNs) show broad ${\rm H} \, \alpha$ emission, which recent studies ascribe to scattering off free electrons within an ionized medium embedding the broad-line region (BLR), rather…
View article: A direct black hole mass measurement in a Little Red Dot at the Epoch of Reionization
A direct black hole mass measurement in a Little Red Dot at the Epoch of Reionization Open
Recent discoveries of faint active galactic nuclei (AGN) at the redshift frontier have revealed a plethora of broad \Halpha emitters with optically red continua, named Little Red Dots (LRDs), which comprise 15-30\% of the high redshift bro…
View article: The missing Fe II bump in faint JWST active galactic nuclei: Possible evidence of metal-poor broad-line regions at early cosmic times
The missing Fe II bump in faint JWST active galactic nuclei: Possible evidence of metal-poor broad-line regions at early cosmic times Open
Recent JWST observations have revealed a large population of intermediate/low-luminosity active galactic nuclei (AGNs) at early times with peculiar properties, different from local AGNs or luminous quasars. To better understand the physica…
View article: JADES – the small blue bump in GN-z11: insights into the nuclear region of a galaxy at <i>z</i> = 10.6
JADES – the small blue bump in GN-z11: insights into the nuclear region of a galaxy at <i>z</i> = 10.6 Open
We report the detection of continuum excess in the rest-frame ultraviolet (UV) between 3000 and 3550 Å in the JWST/Near Infrared Spectrograph (NIRSpec) spectrum of GN-z11, a luminous galaxy $z=10.603$. The shape of the continuum excess res…
View article: JADES reveals a large population of low mass black holes at high redshift
JADES reveals a large population of low mass black holes at high redshift Open
JWST has revealed a large population of active galactic nuclei (AGN) in the distant universe, which are challenging our understanding of early massive black hole seeding and growth. We expand the exploration of this population to lower lum…
View article: Progtuning: Progressive Fine-tuning Framework for Transformer-based Language Models
Progtuning: Progressive Fine-tuning Framework for Transformer-based Language Models Open
Fine-tuning is a promising technique for leveraging Transformer-based language models in downstream tasks. As model sizes continue to grow, updating all model parameters becomes increasingly costly. Parameter-efficient fine-tuning methods …
View article: JADES and BlackTHUNDER: rest-frame Balmer-line absorption and the local environment in a Little Red Dot at z = 5
JADES and BlackTHUNDER: rest-frame Balmer-line absorption and the local environment in a Little Red Dot at z = 5 Open
We present a broad-line AGN at z=5.077, observed with both NIRSpec/MSA and NIRSpec/IFU by the JADES and BlackTHUNDER surveys. The target exhibits all the hallmark features of a 'Little Red Dot' (LRD) AGN. The combination of spatially resol…
View article: Overmassive black holes in the early Universe can be explained by gas-rich, dark matter-dominated galaxies
Overmassive black holes in the early Universe can be explained by gas-rich, dark matter-dominated galaxies Open
JWST has revealed the apparent evolution of the black hole (BH)-stellar mass ($M_\mathrm{BH}$-$M_\rm{\ast}$) relation in the early Universe, while remaining consistent the BH-dynamical mass ($M_\mathrm{BH}$-$M_\mathrm{dyn}$) relation. We p…
View article: Narrow-line AGN selection in CEERS: Spectroscopic selection, physical properties, and X-ray and radio analysis
Narrow-line AGN selection in CEERS: Spectroscopic selection, physical properties, and X-ray and radio analysis Open
The transformative era opened by the James Webb Space Telescope (JWST) on the high- z Universe allows us to investigate the early stages of supermassive black hole (SMBH) evolution, with the first results showing a greater than expected nu…
View article: Narrow-line AGN selection in CEERS: Spectroscopic selection, physical properties, and X-ray and radio analysis
Narrow-line AGN selection in CEERS: Spectroscopic selection, physical properties, and X-ray and radio analysis Open
The transformative era opened by the James Webb Space Telescope (JWST) on the high- z Universe allows us to investigate the early stages of supermassive black hole (SMBH) evolution, with the first results showing a greater than expected nu…
View article: Metallicity of active galactic nuclei from ultraviolet and optical emission lines – I. Carbon abundance dependence
Metallicity of active galactic nuclei from ultraviolet and optical emission lines – I. Carbon abundance dependence Open
Metallicity (Z) estimates based on ultraviolet (UV) emission lines from the narrow-line regions of active galactic nuclei (AGNs) have been found to differ from those derived from optical lines. However, the origin of this discrepancy ($ZR$…
View article: A black hole in a near-pristine galaxy 700 million years after the Big Bang
A black hole in a near-pristine galaxy 700 million years after the Big Bang Open
The recent discovery of a large number of massive black holes within the first two billion years after the Big Bang, as well as their peculiar properties, have been largely unexpected based on the extrapolation of the properties of luminou…
View article: JADES: nitrogen enhancement in high-redshift broad-line active galactic nuclei
JADES: nitrogen enhancement in high-redshift broad-line active galactic nuclei Open
The unexpectedly high nitrogen-to-oxygen (N/O) ratios observed in high-redshift (z) galaxies have challenged our understanding of early star formation. Notably, many of these nitrogen-rich galaxies show signatures of active galactic nuclei…
View article: The density-bounded twilight of starbursts in the early Universe
The density-bounded twilight of starbursts in the early Universe Open
The peculiar nebular emission displayed by galaxies in the early Universe presents a unique opportunity to gain insight into the regulation of star formation in extreme environments. We investigate 500 (109) galaxies with deep NIRSpec/PRIS…
View article: Resolving the nature and putative nebular emission of GS9422: an obscured AGN without exotic stars
Resolving the nature and putative nebular emission of GS9422: an obscured AGN without exotic stars Open
Understanding the sources that power nebular emission in high-redshift galaxies is fundamentally important not only for shedding light on to the drivers of reionization, but to constrain stellar populations and the growth of black holes. H…
View article: JWST MIRI reveals the diversity of nuclear mid-infrared spectra of nearby type 2 quasars
JWST MIRI reveals the diversity of nuclear mid-infrared spectra of nearby type 2 quasars Open
Type 2 quasars (QSO2s) are active galactic nuclei (AGN) seen through a significant amount of dust and gas that obscures the central supermassive black hole and the broad-line region. Here, we present new mid-infrared spectra of the central…