More Like this

1. Obscured AGN at z < 1.5: X-Ray to Far-infrared SEDs and Host Galaxy Morphologies in the GOODS Fields

   https://doi.org/10.3847/1538-4357/ae40b4  

   Jarvis, William WH; Auge, Connor; Sanders, David; Ding, Xuheng; Kim-Bolt, Jeana; Urry, C Megan; Hooper, Eric; Peca, Alessandro; Ghosh, Aritra; Tian, Chuan; et al (April 2026, The Astrophysical Journal)

   Abstract We present an analysis of spectral energy distributions (SEDs), galaxy light profiles, and visual morphological classifications for 194 X-ray luminous active galactic nuclei (AGN) (intrinsic absorption-corrected $\log \left(L_{\mathrm{X},0.5-7\mathrm{keV}}\right)>42.5\left(\mathrm{maximum}45.2\right)\mathrm{erg}{\mathrm{s}}^{-1}$ ) withz < 1.5 in the Great Observatories Origins Deep Survey (GOODS) fields. We generate X-ray to far-infrared SEDs normalized at 1μm for all AGN and sort them according to their emission slopes in the ultraviolet (UV) and infrared (IR). We visually classify their host galaxies’ morphologies and compute their bulge/total light ratios using the Galaxy Shapes of Light (galight) software. Most (94%) GOODS AGN exhibit obscured (i.e., diminished UV and/or mid-IR emission) SEDs. Only 6% show unobscured, quasar-like SEDs. Secular processes appear to play a large role in stimulating AGN emission, since only ∼1/3 of galaxies are undergoing interactions. We also describe the morphological identification of a population of suspected postmerger spheroid galaxies with obscured UV/IR SEDs and distinguish them from the host galaxies of AGN with less obscuration in the UV or IR. 

   more » « less
2. (Nearly) Model-independent Constraints on the Neutral Hydrogen Fraction in the Intergalactic Medium at z ∼ 5–7 Using Dark Pixel Fractions in Lyα and Lyβ Forests

   https://doi.org/10.3847/1538-4357/aca678  

   Jin, Xiangyu; Yang, Jinyi; Fan, Xiaohui; Wang, Feige; Bañados, Eduardo; Bian, Fuyan; Davies, Frederick B.; Eilers, Anna-Christina; Farina, Emanuele Paolo; Hennawi, Joseph F.; et al (January 2023, The Astrophysical Journal)

   Abstract Cosmic reionization was the last major phase transition of hydrogen from neutral to highly ionized in the intergalactic medium (IGM). Current observations show that the IGM is significantly neutral atz> 7 and largely ionized byz∼ 5.5. However, most methods to measure the IGM neutral fraction are highly model dependent and are limited to when the volume-averaged neutral fraction of the IGM is either relatively low ( ${\overline{x}}_{\mathrm{H}\mathrm{I}}\lesssim {10}^{-3}$ ) or close to unity ( ${\overline{x}}_{\mathrm{H}\mathrm{I}}\sim 1$ ). In particular, the neutral fraction evolution of the IGM at the critical redshift range ofz= 6–7 is poorly constrained. We present new constraints on ${\overline{x}}_{\mathrm{H}\mathrm{I}}$ atz∼ 5.1–6.8 by analyzing deep optical spectra of 53 quasars at 5.73 <z< 7.09. We derive model-independent upper limits on the neutral hydrogen fraction based on the fraction of “dark” pixels identified in the Lyαand Lyβforests, without any assumptions on the IGM model or the intrinsic shape of the quasar continuum. They are the first model-independent constraints on the IGM neutral hydrogen fraction atz∼ 6.2–6.8 using quasar absorption measurements. Our results give upper limits of ${\overline{x}}_{\mathrm{H}\mathrm{I}}(z=6.3)<0.79\pm 0.04$ (1σ), ${\overline{x}}_{\mathrm{H}\mathrm{I}}(z=6.5)<0.87\pm 0.03$ (1σ), and ${\overline{x}}_{\mathrm{H}\mathrm{I}}(z=6.7)<{0.94}_{-0.09}^{+0.06}$ (1σ). The dark pixel fractions atz> 6.1 are consistent with the redshift evolution of the neutral fraction of the IGM derived from Planck 2018. 

   more » « less
3. Massive Extremely High-velocity Outflow in the Quasar J164653.72+243942.2

   https://doi.org/10.3847/1538-4357/adef0d  

   Rodríguez_Hidalgo, Paola; Choi_최, Hyunseop 현섭; Hall, Patrick B; Leighly, Karen M; Flores, Liliana; Charles, Mikel M; DeFrancesco, Cora; Hlavacek-Larrondo, Julie; Perreault-Levasseur, Laurence (September 2025, The Astrophysical Journal)

   Abstract We present analysis of one of the most extreme quasar outflows found to date in our survey of extremely high-velocity outflows (EHVOs). J164653.72+243942.2 (z_em ∼ 3.04) shows variable Civλλ1548,1551 absorption at speeds larger than 0.1c, accompanied by Siiv, Nv,and Lyα, and disappearing absorption at lower speeds. We perform absorption measurements using the apparent optical depth method and SimBAL. We find the absorption to be very broad (Δv ∼  35,100 km s⁻¹in the first epoch and 13,000 km s⁻¹in the second one) and fast (v_max ∼  –50,200 km s⁻¹and −49,000 km s⁻¹, respectively). We measure large column densities ( $\log N_{\mathrm{H}}>$ 21.6 (cm⁻²)) and are able to place distance estimates for the EHVO (5 ≲ R ≲ 28 pc) and the lower-velocity outflow (7 ≲ R ≲ 540 pc). We estimate a mass outflow rate for the EHVO to be ${\dot{M}}_{\mathrm{out}}\sim 50–290M_{\odot }{\mathrm{yr}}^{-1}$ and a kinetic luminosity of $\log L_{\mathrm{KE}}\sim 46.5–47.2\left(\mathrm{erg}{\mathrm{s}}^{-1}\right)$ in both epochs. The lower-velocity component has a mass outflow rate ${\dot{M}}_{\mathrm{out}}\sim 10–790M_{\odot }{\mathrm{yr}}^{-1}$ and a kinetic luminosity of $\log L_{\mathrm{KE}}\sim 45.3–47.2\left(\mathrm{erg}{\mathrm{s}}^{-1}\right)$ . We find that J164653.72+243942.2 is not an outlier among EHVO quasars in regard to its physical properties. While its column density is lower than typical BAL values, its higher outflow velocities drive most of the mass outflow rate and kinetic luminosity. These results emphasize the crucial role of EHVOs in powering quasar feedback, and failing to account for these outflows likely leads to underestimating the feedback impact on galaxies. 

   more » « less
4. Resolved Measurements of the CO-to-H ₂ Conversion Factor in 37 Nearby Galaxies

   https://doi.org/10.3847/1538-4357/ad23ed  

   Chiang_江, I-Da 宜達; Sandstrom, Karin M; Chastenet, Jérémy; Bolatto, Alberto D; Koch, Eric W; Leroy, Adam K; Sun_孙, Jiayi 嘉懿; Teng, Yu-Hsuan; Williams, Thomas G (March 2024, The Astrophysical Journal)

   Abstract We measure the CO-to-H₂conversion factor (α_CO) in 37 galaxies at 2 kpc resolution, using the dust surface density inferred from far-infrared emission as a tracer of the gas surface density and assuming a constant dust-to-metal ratio. In total, we have ∼790 and ∼610 independent measurements ofα_COfor CO (2–1) and (1–0), respectively. The mean values forα_{CO (2–1)}andα_{CO (1–0)}are ${9.3}_{-5.4}^{+4.6}$ and ${4.2}_{-2.0}^{+1.9}{M}_{\odot }{\mathrm{pc}}^{-2}{\left(\mathrm{K}\mathrm{km}{\mathrm{s}}^{-1}\right)}^{-1}$ , respectively. The CO-intensity-weighted mean is 5.69 forα_{CO (2–1)}and 3.33 forα_{CO (1–0)}. We examine howα_COscales with several physical quantities, e.g., the star formation rate (SFR), stellar mass, and dust-mass-weighted average interstellar radiation field strength ( $\overline{U}$ ). Among them, $\overline{U}$ , Σ_SFR, and the integrated CO intensity (W_CO) have the strongest anticorrelation with spatially resolvedα_CO. We provide linear regression results toα_COfor all quantities tested. At galaxy-integrated scales, we observe significant correlations betweenα_COandW_CO, metallicity, $\overline{U}$ , and Σ_SFR. We also find thatα_COin each galaxy decreases with the stellar mass surface density (Σ_⋆) in high-surface-density regions (Σ_⋆≥ 100M_⊙pc⁻²), following the power-law relations ${\alpha }_{\mathrm{CO}(2–1)}\propto {\mathrm{\Sigma }}_{\star }^{-0.5}$ and ${\alpha }_{\mathrm{CO}(1–0)}\propto {\mathrm{\Sigma }}_{\star }^{-0.2}$ . The power-law index is insensitive to the assumed dust-to-metal ratio. We interpret the decrease inα_COwith increasing Σ_⋆as a result of higher velocity dispersion compared to isolated, self-gravitating clouds due to the additional gravitational force from stellar sources, which leads to the reduction inα_CO. The decrease inα_COat high Σ_⋆is important for accurately assessing molecular gas content and star formation efficiency in the centers of galaxies, which bridge “Milky Way–like” to “starburst-like” conversion factors. 

   more » « less
5. Evidence for Environmental Effects in the z = 4.3 Protocluster Core SPT2349–56

   https://doi.org/10.3847/2041-8213/adc1c9  

   Hughes, Chayce; Hill, Ryley; Chapman, Scott C; Aravena, Manuel; Archipley, Melanie; Dike, Veronica J; Gonzalez, Anthony; Greve, Thomas R; Gururajan, Gayathri; Hayward, Chris; et al (April 2025, The Astrophysical Journal Letters)

   Abstract We present Atacama Large Millimeter/submillimeter Array observations of the [CI] 492 and 806 GHz fine-structure lines in 25 dusty star-forming galaxies (DSFGs) atz= 4.3 in the core of the SPT2349–56 protocluster. The protocluster galaxies exhibit a median $L_{\left[\text{C}\mathrm{I}\right](2-1)}^{\prime }/L_{\left[\text{C}\mathrm{I}\right](1-0)}^{\prime }$ ratio of 0.94, with an interquartile range of 0.81–1.24. These ratios are markedly different to those observed in DSFGs in the field (across a comparable redshift and 850μm flux density range), where the median is 0.55, with an interquartile range of 0.50–0.76, and we show that this difference is driven by an excess of [Ci](2–1) in the protocluster galaxies for a given 850μm flux density. Assuming local thermal equilibrium, we estimate gas excitation temperatures of $T_{\mathrm{ex}}=59.1_{-6.8}^{+8.1}$ K for our protocluster sample and $T_{\mathrm{ex}}=33.9_{-2.2}^{+2.4}$ K for the field sample. Our main interpretation of this result is that the protocluster galaxies have had their cold gas driven to their cores via close-by interactions within the dense environment, leading to an overall increase in the average gas density and excitation temperature, as well as an elevated [Ci](2–1) luminosity-to-far-infrared-luminosity ratio. 

   more » « less