The Two-component Circumgalactic Medium Emission around <i>z</i>  ∼ 2 Radio-loud Quasars

The Astrophysical Journal · 2026-05-05

Abstract We present Ly α , He ii , and C iv observations of seven z ∼ 2 radio-loud quasars observed using the Keck Cosmic Web Imager and compare it to observed radio jet emission using archival Very Large Array and Atacama Large Millimeter/submillimeter Array radio observations. We detect 80–120 kpc diameter Ly α and 10–40 kpc He ii and C iv emission around the targets. We find the Ly α emission to be brighter within the inner 30 kpc by factors of 2–10 compared to other literature samples. We reproduce the trend for increased total luminosity for a larger on-sky area, but find our targets tend to be brighter for a given area when compared to literature observations, even when adjusting for the observational sensitivity. We infer that the He ii and C iv is likely powered by quasar photoionization, with the ionizing radiation likely escaping along the radio jet axis, which is aligned with the He ii and C iv emission. The observations agree with a two-component model of the circumgalactic medium (CGM), where the inner CGM (&lt;30 kpc) is directly influenced by the host galaxies, whereas gas motions in the outer CGM (&gt;30 kpc) are governed by turbulence and the larger-scale environment.

Multi-Component Ionized Gas Outflows in a Hot Dust-Obscured Galaxy W2026+0716 with Keck/OSIRIS

ArXiv.org · 2025-04-29

We present narrowband-filtered integral field unit (IFU) observations of the Hot Dust-Obscured Galaxy (Hot DOG) WISE J202615.27$+$071624.0 (hereafter W2026$+$0716) at redshift $z=2.570$ using Keck/OSIRIS. Our analysis reveals a multi-component ionized gas outflow structure in this heavily obscured AGN host galaxy. Multi-component Gaussian decomposition of the [O III] and H$α$ emission lines uncovers extremely broad and asymmetric profiles, characteristic of AGN-driven outflows. Kinematic mapping shows spatially distinct structures: the [O III] and H$α$ dominated components (with radii of $1.20 \pm 0.56$ kpc) are separated by a projected offset of $\sim 1.1$ kpc and exhibit divergent velocity regimes. The [O III] outflow reaches a velocity of 3210 $\pm$ 50 km s$^{-1}$, while the H$α$ outflow component attains 2310 $\pm$ 840 km s$^{-1}$. Dynamical modeling supports a biconical outflow structure, with [O III] and H$α$ emissions dominating separate cones and significant dust obscuration of the redshifted outflow. Their comparable momentum outflow rates and energy outflow rates suggest a potential physical connection in their driving mechanisms. Spectral energy distribution (SED) analysis reveals anomalous optical/UV excess, attributed to AGN photon scattering by dust or outflowing material, classifying W2026+0716 as a "Blue Hot DOG". The derived outflow timescale ($\sim10^{5}$ yr) aligns with the evolutionary phase of Blue Hot DOGs, suggesting AGN feedback operates persistently during this transitional stage.

Deriving Stellar Parameters for High-redshift (1.2 ≤ <i>z</i> ≤ 2.6) Galaxies Using CIGALE

Research Notes of the AAS · 2025-04-03

Abstract We present results for 19 galaxies in the redshift range 1.2 ≲ z ≲ 2.6 to model star formation rate (SFR) and stellar mass using galactic spectral energy distributions. With W. M. Keck Observatory MOSFIRE we spectroscopically confirm redshifts using lines of H α , which are further used to confirm SFR and stellar mass calculations. Our observed and modeled SFRs are in reasonable agreement, validating the modeled parameters produced by the application of Code Investigating GALaxy Emission stellar population synthesis software to Keck MOSFIRE observations of high-redshift galaxies.

Testing Gamma/Hadron Separation for Ultra-High-Energy Cherenkov Astronomy

2025-09-24

Dark100 is a planned array of six telescopes, using the Panoramic Search for Extraterrestrial Intelligence (PANOSETI) telescope system. It will operate as an imaging atmospheric Cherenkov telescope array, with a telescope design and array layout optimized for accessing gamma rays with tens of TeV to PeV energies. The science goals of Dark100 include the search for ultra-heavy dark matter, observations of Galactic Pevatrons, and the search for ultra-fast optical transients. Rejection of background cosmic rays is key to the sensitivity of the array. We present a first study of gamma/hadron separation based on simulated gamma rays and protons, focusing on the impact of the hadronic background models used in CORSIKA.

Validating the On-axis Point Spread Function Reconstruction for Keck Adaptive Optics

Publications of the Astronomical Society of the Pacific · 2025-10-01

Abstract The largest telescopes (8–10 m) in the world regularly deploy adaptive optics (AO) systems utilizing natural and laser guide stars in tandem with deformable mirrors to correct the turbulent effects of the atmosphere and obtain Point Spread Functions (PSF) with Full Width at Half Maximum (FWHM) of less than 100 mas. While classical techniques seek to extract the PSF from the images, reconstructing the PSF from first principles will allow resolving high angular resolution phenomena in the absence of an unresolved point source in the science field. We use PRIME, a python package for PSF reconstruction and modelling to forward model the PSFs for NIRC2 data from the Keck II telescope’s AO system. We also use PRIME to fit the PSFs to a Fourier model and compare the performance between the two approaches by considering the Strehl, FWHM and the Fraction of Variance Unexplained. We then discuss the implications of our analysis for the upcoming Keck All-sky Precision Adaptive Optics upgrade on the Keck I telescope.

Multicomponent Ionized Gas Outflows in the Hot Dust-obscured Galaxy W2026+0716 with Keck/OSIRIS

The Astrophysical Journal · 2025-06-03 · 1 citations

Abstract We present narrowband-filtered integral field unit observations of the hot dust-obscured galaxy (Hot DOG) WISE J202615.27+071624.0 (hereafter W2026+0716) at redshift z = 2.570 using Keck/OSIRIS. Our analysis reveals a multicomponent ionized gas outflow structure in this heavily obscured active galactic nucleus (AGN) host galaxy. Multicomponent Gaussian decomposition of the [O iii ] and H α emission lines uncovers extremely broad and asymmetric profiles, characteristic of AGN-driven outflows. Kinematic mapping shows spatially distinct structures: the [O iii ]- and H α -dominated components (with radii of 1.20 ± 0.56 kpc) are separated by a projected offset of ∼1.1 kpc and exhibit divergent velocity regimes. The [O iii ] outflow reaches a velocity of 3210 ± 50 km s −1 , while the H α outflow component attains 2310±840 km s −1 . Dynamical modeling supports a biconical outflow structure, with [O iii ] and H α emissions dominating separate cones and significant dust obscuration of the redshifted outflow. Their comparable momentum outflow rates and energy outflow rates suggest a potential physical connection in their driving mechanisms. Spectral energy distribution analysis reveals anomalous optical/UV excess, attributed to AGN photon scattering by dust or outflowing material, classifying W2026+0716 as a “Blue Hot DOG”. The derived outflow timescale (∼10 5 yr) aligns with the evolutionary phase of Blue Hot DOGs, suggesting AGN feedback operates persistently during this transitional stage.

Liger at W.M. Keck Observatory: assembly, integration, and testing

2024-06-14

Liger is an adaptive optics (AO)-fed imager and integral field spectrograph (IFS) designed for W.M. Keck Observatory. Liger will be coupled with the Keck All-sky Precision Adaptive-optics (KAPA) upgrade which will allow both systems to fully utilize their capabilities to maximize scientific return for the broader community. Liger features a custom-designed imaging camera that sequentially feeds the pristine AO image to two select-able integral field spectrograph (IFS) modes: an image slicer for coarse spatial sampling and a lenslet array for finer spatial scales. Both IFS modes utilize a final ”camera” three-mirror anastigmat (TMA) and a Hawaii 4RG detector for data collection. This paper will discuss the assembly, integration, and testing (AIT) of the Liger instrument sub-assemblies. The project is currently in the first of two-fabrication phases where we are manufacturing, assembling, and testing the complete imager system, the IFS camera TMA, grating turret mechanism, and the IFS re-imaging optics mechanisms. The second fabrication phase will include the final fabrication and assembly of the IFS and science cryostat. An integration phase will follow where the full instrument is assembled and integrated into the science cryostat. Once complete the Liger instrument will be shipped to Hawaii for final assembly, integration, and verification at W.M. Keck Observatory.

Liger at W.M. Keck Observatory: imager structural analysis, fabrication, and characterization plan

2024-06-14 · 2 citations

Liger is an adaptive optics (AO) fed imager and integral field spectrograph (IFS) designed to take advantage of the Keck All-sky Precision Adaptive-optics (KAPA) upgrade to the Keck I telescope. Liger adapts the design of the InfraRed Imaging Spectrograph (IRIS) for the Thirty Meter Telescope (TMT) to Keck by implementing a new imager and re-imaging optics. The performance of the imager is critical as it sequentially feeds the spectrograph and contains essential components such as the pupil wheel, filter wheel, and pupil viewing camera. We present the design and structural analysis of the Liger imager optical assembly including static, modal, and thermal simulations. We present the fabrication as well as the full assembly and characterization plan. The imager will be assembled bench-top in a clean room utilizing a coordinate-measuring machine (CMM) for warm alignment. To ensure optimal performance, the imager will be characterized in a test cryostat before integration with the full Liger instrument. This comprehensive approach to characterization ensures the precision and reliability of the imager, enhancing the observational capabilities of Liger and W.M. Keck Observatory.

Circumgalactic Environments around Distant Quasars 3C 9 and 4C 05.84

arXiv (Cornell University) · 2024-01-08

We present results from the ``Quasar hosts Unveiled by high Angular Resolution Techniques" (QUART) survey studying the Circumgalactic Medium (CGM) by observing rest-frame UV emission lines Ly$α$, C IV and He II around two radio-loud quasars, 3C 9 (z=2.02) and 4C 05.84 (z=2.32), using Keck Cosmic Web Imager (KCWI). We detect large-scale Ly$α$ nebulae around both quasars with projected diameters $\sim$ 100 kpc, with spatially resolved, embedded 15-30 kpc He II and C IV nebulae around both quasars as well as kinematically distinct He II and C IV nebulae at a physical separation of $\sim$ 15 kpc from both quasars. Observations of H$α$, H$β$, and [O III] emission using Keck MOSFIRE spectroscopically confirm that the Ly$α$ nebulae extend to companion galaxies and that these quasars are in a protogroup/protocluster environment. We confirm that the He II and C IV emission is kinematically and spatially coincident with the companion galaxies. We estimate the virial masses of the companion galaxies, their metallicities, and star formation rates, and investigate the sources of ionization. We measure the dynamical mass of the host dark matter halos and estimate that the dark matter halos of these systems will grow to a mass of 2 $\times 10^{14}$ M$_{\odot}$ (3C 9) and 2 $\times 10^{13}$ M$_{\odot}$ (4C 05.84) by z=0. The combined CGM and companion galaxies observations indicate Ly$α$ substructure can indicate the presence of companion galaxies in the CGM.

Innovations and advances in instrumentation at the W. M. Keck Observatory, vol. III

2024-07-19

Since the start of science operations in 1993, the twin 10-meter W. M. Keck Observatory (WMKO) telescopes have continued to maximize their scientific impact to produce transformative discoveries that keep the U.S. observing community on the frontiers of astronomical research. Upgraded capabilities and new instrumentation are provided though collaborative partnerships primarily with the Caltech and University of California instrument development teams and through additional collaborations with the University of Notre Dame, the University of Hawaii, Swinburne University of Technology, industry, and other organizations. This paper summarizes the status and performance of observatory infrastructure projects, technology upgrades, and new additions to the suite of observatory instrumentation. We also provide a status of instrumentation projects in early and advanced stages of development that will achieve the goals and objectives summarized in the 2023 Keck Observatory strategic plan. Developed in collaboration with the WMKO science community, the Keck strategic plan sets our sites on 2035 and meets goals identified in the Astro2020 Decadal Survey.