Weekly issue

Week 17, 2025

Apr 21–27, 2025

Week 17, 2025 includes 3 curated papers, centered on QSO, spectroscopy, high-z.

2504.17007v1

The First Photometric Evidence of a Transient/Variable Source at z>5 with JWST

Christa DeCoursey, Eiichi Egami, Fengwu Sun, Arshia Akhtarkavan, Rachana Bhatawdekar, Andrew J. Bunker, David A. Coulter, Michael Engesser, Ori D. Fox, Sebastian Gomez, Kohei Inayoshi, Benjamin D. Johnson, Mitchell Karmen, Conor Larison, Xiaojing Lin, Jianwei Lyu, Seppo Mattila, Takashi J. Moriya, Justin D. R. Pierel, Dávid Puskás, Armin Rest, George H. Rieke, Brant Robertson, Sepehr Salamat, Louis-Gregory Strolger, Sandro Tacchella, Christian Vassallo, Christina C. Williams, Yossef Zenati, Junyu Zhang

Theme match 3/5

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Reports AT 2023adya, a transient/variable source in a z_spec=5.274 GOODS-N galaxy, detected via a 0.19 mag fade in F356W over ~2 rest-frame months with a significant difference-image residual (SN_var≈6). No contemporaneous variability is seen in the rest-UV (F090W/F115W), and the rest-frame V-band absolute magnitude is MV≈−18.48. NIRCam/Grism data show no broad Hα (FWHM=130±26 km s−1), disfavoring an AGN origin; Ia is possible but unlikely given low high‑z rates, with CCSN remaining plausible while TDEs are disfavored by low event rates. The result establishes practical JWST sensitivity to transient/variable phenomena beyond z>5, nudging discovery space toward the reionization era.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1: Compare Epoch1 vs. Epoch2 NIRCam cutouts and the RGB composites to verify the F356W‑only residual centered on the host nucleus and the lack of F090W/F115W changes; also note the labeled companion that could affect blending in Epoch1.
Figure 2: Use the overplotted MV≈−18.5 marker against B‑band peak distributions to gauge which CCSN subclasses or Ia could match the luminosity, keeping in mind it is a lower limit if Epoch1 was pre‑peak/post‑peak.
Figure 3: Inspect the NIRCam/WFSS extractions of Hα (F444W) and [O III]5008 (F356W) to confirm the absence of broad components (Hα FWHM ~130 km s−1) and assess the caveat that [O III] lies at the blue edge with imperfect background subtraction.

A Massive Gas Outflow Outside the Line-of-Sight: Imaging Polarimetry of the Blue Excess Hot Dust Obscured Galaxy W0204-0506

Roberto J. Assef, Marko Stalevski, Lee Armus, Franz E. Bauer, Andrew Blain, Murray Brightman, Tanio Díaz-Santos, Peter R. M. Eisenhardt, Román Fernández-Aranda, Hyunsung D. Jun, Mai Liao, Guodong Li, Lee R. Martin, Elena Shablovinskaia, Devika Shobhana, Daniel Stern, Chao-Wei Tsai, Andrey Vayner, Dominic J. Walton, Jingwen Wu, Dejene Zewdie

Theme match 3/5

Digest

VLT/FORS2 imaging polarimetry of the blue-excess Hot DOG WISE J020446.13–050640.8 (W0204–0506) finds a spatially integrated UV polarization of 24.7 ± 0.7% in R_Special, clinching a scattered-light origin for the faint blue continuum. The source is resolved, showing a polarization fraction and angle gradient aligned with the HST/WFC3 morphology, which SKIRT radiative-transfer models reproduce with a dusty conical polar outflow that starts at the sublimation radius, has half-opening angle ≤50°, and is viewed at inclination ≥45°, favoring graphite-rich dust. Inferred gas mass and outflow velocity fall within ranges seen for [O III] outflows in other Hot DOGs, though the feedback impact on the host remains uncertain. The work showcases imaging polarimetry as a geometry probe for dusty quasar outflows complementary to spectroscopy.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1 (SED): Check how the blue excess is modeled—heavily obscured luminous AGN plus a lightly obscured, lower-luminosity component that accounts for scattered UV—quantifying the ~2 dex mismatch between UV and mid-IR power.
Figure 2 (Maps): Inspect the pixel-resolved polarization fraction and angle versus HST F555W/F160W structure; the alignment and cone-edge overlays constrain the outflow axis, projected ∼10 kpc extent, and confirm the scatterers lie outside our direct line of sight.
Figure 3 (p[λ] vs dust): Compare the measured ~25% R-band point to SKIRT predictions; note that graphite-rich dust and a single approaching/receding cone can reach the observed polarization, whereas other mixtures underpredict it.
Figure 4 (χ² grids): Read the allowed regions for inclination and half-opening angle; the hatched zones mark disallowed direct-view configurations, highlighting the preferred i ≥45° and θ ≤50° solution consistent with a torus-limited cone.

Insights on Metal Enrichment and Environmental Effect at $z\approx5-7$ with JWST ASPIRE/EIGER and Chemical Evolution Model

Zihao Li, Koki Kakiichi, Lise Christensen, Zheng Cai, Avishai Dekel, Xiaohui Fan, Emanuele Paolo Farina, Hyunsung D. Jun, Zhaozhou Li, Mingyu Li, Maria Pudoka, Fengwu Sun, Maxime Trebitsch, Fabian Walter, Feige Wang, Jinyi Yang, Huanian Zhang, Siwei Zou

Theme match 2/5

Digest

Using JWST/NIRCam WFSS across 26 quasar fields (ASPIRE+EIGER), the authors build a [O III]-selected sample of 604 galaxies at z=5.34–6.94 and flag 204 protocluster members via a friends-of-friends search. Stacked spectra detect Hγ and [O III] λ4363, giving Te=2.0(+0.3,-0.4)×10^4 K and a metal-poor median 12+log(O/H)=7.65(+0.26,-0.15). With NIRSpec-anchored strong-line calibrations, the MZR shows ≈0.2 dex higher metallicity at the high-mass end in overdense regions, while the full z>5 sample sits ≈0.2 dex below the local FMR. A simple chemical-evolution model points to dilution from intense gas accretion, with protocluster galaxies closer to gas equilibrium—evidence for accelerated early enrichment during protocluster assembly at z≈5–7.

Open paper page arXiv abstract arXiv PDF Highlighted PDF

Key figures to inspect

Figure 1: Check the z=5.34–6.94 distribution and ASPIRE vs EIGER contributions to gauge survey volume and where overdensities pile up; this sets the environment comparison baseline.
Figure 2: Inspect the stacked spectrum for Hγ and [O III] λ4363 visibility and S/N; these lines underpin the Te≈2×10^4 K and the low median metallicity—also verify the 4959/5007 ratio consistency.
Figure 3: Use the mass–excitation diagram to see where field and protocluster stacks fall relative to the Coil et al. (2015) AGN demarcation, assessing AGN contamination in the [O III]-selected sample.
Figure 4: Compare protocluster vs field MZR using the R3 (C24) calibration and note the ≈0.2 dex high-mass enhancement; contrast with the local FMR offset and with literature curves at similar redshift.

Week 17, 2025

The First Photometric Evidence of a Transient/Variable Source at z>5 with JWST

Digest

Key figures to inspect

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A Massive Gas Outflow Outside the Line-of-Sight: Imaging Polarimetry of the Blue Excess Hot Dust Obscured Galaxy W0204-0506

Digest

Key figures to inspect

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Insights on Metal Enrichment and Environmental Effect at $z\approx5-7$ with JWST ASPIRE/EIGER and Chemical Evolution Model

Digest

Key figures to inspect

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