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- ItemA Highly Magnified Gravitationally Lensed Red QSO at z = 2.5 with a Significant Flux Ratio Anomaly(London : Institute of Physics Publ., 2023) Glikman, Eilat; Rusu, Cristian E.; Chen, Geoff C.-F.; Chan, James Hung-Hsu; Spingola, Cristiana; Stacey, Hannah; McKean, John; Berghea, Ciprian T.; Djorgovski, S. G.; Graham, Matthew J.; Stern, Daniel; Urrutia, Tanya; Lacy, Mark; Secrest, Nathan J.; O’Meara, John M.We present the discovery of a gravitationally lensed dust-reddened QSO at z = 2.517, identified in a survey for QSOs by infrared selection. Hubble Space Telescope imaging reveals a quadruply lensed system in a cusp configuration, with a maximum image separation of ∼1.″8. We find that, compared to the central image of the cusp, the neighboring brightest image is anomalous by a factor of ∼7-10, which is the largest flux anomaly measured to date in a lensed QSO. Incorporating high-resolution Very Large Array radio imaging and submillimeter imaging with the Atacama Large Millimeter/submillimeter Array, we conclude that a low-mass perturber is the most likely explanation for the anomaly. The optical through near-infrared spectrum reveals that the QSO is moderately reddened with E(B − V) ≃ 0.7-0.9. We see an upturn in the ultraviolet spectrum due to ∼1% of the intrinsic emission being leaked back into the line of sight, which suggests that the reddening is intrinsic and not due to the lens. The QSO may have an Eddington ratio as high as L/L Edd ≈ 0.2. Consistent with previous red QSO samples, this source exhibits outflows in its spectrum, as well as morphological properties suggestive of it being in a merger-driven transitional phase. We find a host galaxy stellar mass of log M ⋆ / M ⊙ = 11.4 , which is higher than the local M BH versus M ⋆ relation but consistent with other high-redshift QSOs. When demagnified, this QSO is at the knee of the luminosity function, allowing for the detailed study of a more typical moderate-luminosity infrared-selected QSO at high redshift.
- ItemThe Bimodal Absorption System Imaging Campaign (BASIC). I. A Dual Population of Low-metallicity Absorbers at z < 1(London : Institute of Physics Publ., 2023) Berg, Michelle A.; Lehner, Nicolas; Howk, J. Christopher; O’Meara, John M.; Schaye, Joop; Straka, Lorrie A.; Cooksey, Kathy L.; Tripp, Todd M.; Prochaska, J. Xavier; Oppenheimer, Benjamin D.; Johnson, Sean D.; Muzahid, Sowgat; Bordoloi, Rongmon; Werk, Jessica K.; Fox, Andrew J.; Katz, Neal; Wendt, Martin; Peeples, Molly S.; Ribaudo, Joseph; Tumlinson, JasonThe bimodal absorption system imaging campaign (BASIC) aims to characterize the galaxy environments of a sample of 36 H i-selected partial Lyman limit systems (pLLSs) and Lyman limit systems (LLSs) in 23 QSO fields at z ≲ 1. These pLLSs/LLSs provide a unique sample of absorbers with unbiased and well-constrained metallicities, allowing us to explore the origins of metal-rich and low-metallicity circumgalactic medium (CGM) at z < 1. Here we present Keck/KCWI and Very Large Telescope/MUSE observations of 11 of these QSO fields (19 pLLSs) that we combine with Hubble Space Telescope/Advanced Camera for Surveys imaging to identify and characterize the absorber-associated galaxies at 0.16 ≲ z ≲ 0.84. We find 23 unique absorber-associated galaxies, with an average of one associated galaxy per absorber. For seven absorbers, all with <10% solar metallicities, we find no associated galaxies with log M ⋆ ≳ 9.0 within ρ/R vir and ∣Δv∣/v esc ≤ 1.5 with respect to the absorber. We do not find any strong correlations between the metallicities or H i column densities of the gas and most of the galaxy properties, except for the stellar mass of the galaxies: the low-metallicity ([X/H] ≤ −1.4) systems have a probability of 0.39 − 0.15 + 0.16 for having a host galaxy with log M ⋆ ≥ 9.0 within ρ/R vir ≤ 1.5, while the higher metallicity absorbers have a probability of 0.78 − 0.13 + 0.10 . This implies metal-enriched pLLSs/LLSs at z < 1 are typically associated with the CGM of galaxies with log M ⋆ > 9.0 , whereas low-metallicity pLLSs/LLSs are found in more diverse locations, with one population arising in the CGM of galaxies and another more broadly distributed in overdense regions of the universe. Using absorbers not associated with galaxies, we estimate the unweighted geometric mean metallicity of the intergalactic medium to be [X/H] ≲ −2.1 at z < 1, which is lower than previously estimated.