Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 2609.03608

C3PO: A Lyα Emitting Galaxy at $z \sim 9$

Weida Hu·Casey Papovich·Taylor A. Hutchison·Rebecca L. Larson·Pablo Arrabal Haro·Steven L. Finkelstein·Nikko J. Cleri·Lu Shen·Jiayang Yang
View original source ↗Read source document ↗Export metadata ↓

Abstract

We present deep, $>10$ hr, JWST NIRSpec G140M and G395M observations of a previously known galaxy C3PO-8447 at $z=8.99781$. Our new NIRSpec data from the Carbon-3 plus Oxygen (C3PO) survey detect Ly$α$ emission with an escape fraction of $1.5\pm0.3\%$ and a velocity offset of $210\pm80$ km s$^{-1}$, making C3PO-8447 the third Ly$α$ emitting galaxy confirmed at $z\gtrsim 9$. The galaxy has a low stellar mass of $2.2\pm0.1\times 10^7\ M_\odot$, a young stellar age of $1.6\pm0.2$ Myr, and a low oxygen abundance of $12+\log(\mathrm{O/H}) = 7.50\pm0.08$. UV diagnostic diagrams incorporating the C IV, O III], and C III] emission lines indicate that the ionization of C3PO-8447 is dominated by the recent starburst. The low Ly$α$ escape fraction of C3PO-8447 implies that C3PO-8447 resides in a small ionized bubble with radius $R \sim 0.07$ to 0.20 pMpc, which can be produced by C3PO-8447 alone. We find no evidence for either a large-scale galaxy overdensity around C3PO-8447 or a significant contribution from nearby galaxies to its ionizing photon budget. Taken together, these results suggest that C3PO-8447 likely represents an ionized bubble powered by a single low-mass, vigorously star-forming galaxy during the early stages of cosmic reionization.

Explore related subjects

astro-ph.GA

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Weida Hu, Casey Papovich, Taylor A. Hutchison, Rebecca L. Larson, Pablo Arrabal Haro, Steven L. Finkelstein, Nikko J. Cleri, Lu Shen, Jiayang Yang. 2026-09-03. C3PO: A Lyα Emitting Galaxy at $z \sim 9$. https://arxiv.org/abs/2609.03608

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

A graph-based Neural Network surrogate model for accelerating semi-analytical model of galaxy formation and evolution

Understanding how galaxy populations emerge and evolve from the growth of dark matter structure is a central challenge in galaxy formation theory. Semi-analytic models (SAMs) provide an efficient framework to address this problem, but exploring large ensembles of merger trees across broad parameter spaces remains computationally demanding. We develop a conditional graph neural network surrogate model that combines merger tree information with SAM parameters to predict galaxy properties across cosmic time. Using merger trees of dark matter halos from the Uchuu simulation and the Galacticus SAM, the model predicts stellar mass, luminosity, angular momentum, gas metal mass, and specific star formation rate across the wide redshift range of 0 <= z <= 5. For instance, the model can predict stellar mass at 0 <= z <= 3 with a scatter of 0.19-0.28 dex and coefficient of determination R^2 of 0.946-0.973 (R^2 close to 1 indicates prediction closely matching the truth). The results show that a single graph based model can reproduce these galaxy properties with good accuracy over multiple SAM realizations, merger trees and redshifts. This catalog-level model provides a practical route for accelerating SAM based studies of galaxy formation to enable a more detailed investigation of the model parameter space. The inference code, trained models, and example data products are publicly available at https://github.com/MutongCat/sam2galaxy-gnn.

astro-ph.GA↗
arXiv2026

Radiation Pressure Instability in the "turn-on" Changing-Look AGN SDSS J1430+2303

We aim to investigate the multi-wavelength variability, spectral, and timing properties of the changing-look active galactic nucleus (CL AGN) SDSS J1430+2303, and to explore the physical origin of its peculiar variability pattern that has not been observed before in other CL AGN. We perform a multi-wavelength analysis using optical, ultraviolet, and X-ray observations. We investigate the long-term optical color variation, characterize the evolution of the X-ray spectrum and timing properties, and construct broad-band spectral energy distributions to constrain the black hole mass, spin, and Eddington ratio. The optical flux increased by an order of magnitude over four years, accompanied by a spectral transition from Seyfert 1.9 to 1.2. The long-term color variation follows the ``bluer-when-brighter'' trend, with a color-magnitude slope consistent with previous statistical results for CL and Type 1 AGNs. During the brightened high state, the optical, ultraviolet, and X-ray light curves exhibited rapid decaying periods with progressively decreasing amplitudes, a behavior not previously reported in other CL AGNs. X-ray spectral analysis reveals a remarkably weak soft excess that declines more steeply than the hard X-rays as the total luminosity decreases. X-ray timing analysis shows a nearly constant break frequency and a hard lag at $\sim10^{-4}$ Hz during the luminosity decline, suggesting a stable disk--corona geometry. Broad-band spectral energy distribution fitting constrains the black hole mass to $M_{\rm BH}=3.8-19.5\times10^7\,M_\odot$ and favors a high spin ($a\gtrsim0.77$), while the correspondingly low Eddington ratio can account for the observed weak soft excess. We propose that the observed multi-wavelength decaying periods and their progressively decreasing amplitudes are associated with a shrinking unstable zone driven by radiation-pressure instability in the accretion disk.

astro-ph.GA↗
arXiv2026

Quantifying Environmental Effects on Galaxy Properties using Non-spherical Voids Identified from SDSS DR7

Cosmic voids provide a distinct low-density region for studying the environmental effects of galaxy properties. Using the SDSS DR7 catalog, we identify non-spherical voids via Voronoi tessellation and the watershed algorithm, and classify void galaxies based on their local volume. We compare and find that void galaxies classified by this method are systematically less massive, fainter, bluer, and have higher specific star formation rate (sSFR) than non-void galaxies and all galaxy samples. We then divide void and non-void galaxies into stellar mass bins to focus on the environmental dependence of $g-r$ color and sSFR. By further classifying galaxies into blue/red and star-forming/quiescent populations, we calculate the ratio of blue to red and star-forming to quiescent for void and non-void galaxies separately. Comparing the ratio of the void value to the non-void value for both metrics presents an overall decreasing trend with stellar mass $M_*$ over the $9.4-10.4$ range in $\log[M_*/\mathrm{M}_\odot]$, indicating a stronger environmental effect in lower-mass systems. These results show that our classification of void galaxies in non-spherical voids based on local volume offers a robust approach for quantifying the influence of underdense environments on galaxy evolution.

astro-ph.GA↗