We present the first detailed, spatially resolved study of the circumgalactic medium (CGM) surrounding the low-mass, low-redshift star-forming galaxy J0910b (SDSS J091458.61+110845.1; M\u22c6 ∼ 109.2 M\u2299, z = 0.096), focusing on its gas dynamics, ionization mechanisms, and kinematics. J0910b is the lowest-mass galaxy in our low-redshift CGM survey using the Keck Cosmic Web Imager (KCWI). Using KCWI integral field spectroscopy and CLOUDY modeling, we map the ionization structure and velocity field of the CGM through Hα, [O III] λ5007, and [O II] λλ3727, 3729 emission. We detect a predominantly cool (T ∼ 104 K) ionized halo extending to ∼35 kpc (∼0.35 Rvir), with a complex structure including a counterrotating component and two filamentary inflows. The counterrotating CGM contains ∼7.4 × 109 M\u2299 of ionized gas—nearly 5 times the stellar mass—and exhibits a positive radial metallicity gradient, rising from 0.2 Z\u2299 at 9 kpc to 0.65 Z\u2299 at 16 kpc. Velocity dispersion maps reveal a shell-like structure near the interstellar medium-CGM interface, suggesting feedback-driven outflows that redistributed enriched gas. In contrast, the filaments show low metallicities (∼0.07 Z\u2299), high specific angular momentum (j ∼ 3.7 × 103 kpc km s−1), and an accretion rate of 0.05 M\u2299 yr−1, consistent with an intergalactic origin. Together, these components reveal a dynamically rich CGM. The counterrotating gas dominates the halo’s mass, accounts for ∼33% of the cosmic baryon budget, and must be continuously replenished (tcool ∼ 0.3–2 Myr). These results suggest a long-lived, regulated CGM that governs star formation through angular momentum exchange and gas recycling.
\nWe present the design, development, and end-to-end testing of a unique setup for characterizing the noise performance of silicon-based, photon-counting detectors, using delta-doped detectors developed at Jet Propulsion Lab’s Microdevices Laboratory in collaboration with Teledyne-e2v. Combined with atomic layer deposition coatings, delta-doped detectors have been demonstrated to achieve high quantum efficiency (QE) in the ultraviolet, enabling several UV missions (e.g., FIREBall-2, UVEX, SPARCS, and SHIELDS) and proposals (e.g., Hyperion, UVscope, Eos, and others). Understanding the noise performance of these detectors and developing strategies and designs to minimize that noise is important for future applications such as the Habitable Worlds Observatory (HWO). For instance, delta-doped electron multiplying charge-coupled devices have been identified as a target technology for HWO. This test setup is designed to investigate the impact of the ambient thermal environment, where these detectors are operated, on their noise performance, specifically focusing on the dark current plateau observed below 163 K. This plateau limits the signal-to-noise ratio that can be achieved in the photon-counting mode and has broader implications for the noise performance of silicon-based detectors. The test bench incorporates a delta-doped Teledyne-e2v CCD201-20 readout with a Nüvü CCCP v3 controller at 1 MHz and features a dual cooling system: a cryocooler for the detector and a liquid nitrogen–cooled thermal shroud to simulate a temperature-controlled ambient environment. We describe the design of the test setup, including independent thermal control for the detector and shroud, as well as the validation, optimization, and characterization process for the testbed. The testbed allows for further characterization of the noise performance of the detector, optimization of readout sequences, and operations for low clock-induced charge. First measurements of dark rate were taken across a range of detector temperatures (183 K to 143 K), shroud temperatures (298 K to 180 K), with substrate voltage set to 0 V. We find that the measured dark rate is notably lower with the shroud is cooled to 230 K in comparison with similar measurements with a shroud at 298 K. The reduction in dark rate is potentially due to a decrease in optical/NIR photons emitted from the shroud.
", "doi": "10.1117/1.jatis.11.4.042204", "issn": "2329-4124", "publisher": "SPIE", "publication": "Journal of Astronomical Telescopes, Instruments, and Systems", "publication_date": "2025-06", "series_number": "04", "volume": "11", "issue": "04", "pages": "042204" }, { "id": "authors:5fd2v-4m814", "collection": "authors", "collection_id": "5fd2v-4m814", "cite_using_url": "https://authors.library.caltech.edu/records/5fd2v-4m814", "type": "article", "title": "Delta-doped electron-multiplying charge-coupled device for photon-starved ultraviolet astronomy: modeling, performance, trade-offs, and prospects for future upgrades", "author": [ { "family_name": "Picouet", "given_name": "Vincent", "orcid": "0009-0005-1425-3601", "clpid": "Picouet-Vincent" }, { "family_name": "Kyne", "given_name": "Gillian", "clpid": "Kyne-Gillian" }, { "family_name": "Hamden", "given_name": "Erika", "orcid": "0000-0002-3131-7372" }, { "family_name": "Valls-Gabaud", "given_name": "David" }, { "family_name": "Miles", "given_name": "Drew M.", "orcid": "0000-0001-5982-0060", "clpid": "Miles-Drew-M" }, { "family_name": "Khan", "given_name": "Aafaque", "orcid": "0000-0002-1244-0295" }, { "family_name": "Lin", "given_name": "Zeren", "orcid": "0009-0001-7405-1228", "clpid": "Lin-Zeren" }, { "family_name": "Nikzad", "given_name": "Shouleh", "clpid": "Nikzad-Shouleh" }, { "family_name": "Vibert", "given_name": "Didier", "orcid": "0009-0008-0607-631X" }, { "family_name": "Martin", "given_name": "D. Christopher", "orcid": "0000-0002-8650-1644", "clpid": "Martin-D-Christopher" } ], "abstract": "In the pursuit of observing fainter astronomical sources and phenomena, a significant challenge in detector development lies in ensuring that these devices can detect each individual photon they receive. By amplifying each incoming photon by several orders of magnitude, electron-multiplying charge-coupled devices (EMCCDs) offer a promising solution to meet this challenge. Although these detectors boast impressive potential, they can be intricate, requiring precise optimization and fine-tuning of their parameters to unlock their full capabilities in the photon-starved regime. The Faint Intergalactic-medium Redshifted Emission Balloon (FIREBall-2) is a stratospheric project that aims to detect and map the low surface brightness environment of galaxies in the ultraviolet (UV) at z ~ 0.7. As a technology demonstrator for photon-starved astronomy and to advance the technology readiness level of UV EMCCDs, the instrument uses a Teledyne-e2v (T-e2v) EMCCD delta-doped by the Jet Propulsion Laboratory, combined with a NüVü controller. To analyze the detector data and retrieve the device noise contributions, we developed a comprehensive EMCCD model along with DS9 analysis tools to compare the model with the actual data under diverse operating conditions. This allowed us to examine the current performance and limitations of these devices both on the ground and in the stratospheric environment, to unravel the intricacies of these detectors. In addition, we will discuss the development and implementation of an exposure time calculator designed to optimize the end-to-end signal-to-noise ratio under diverse conditions and analyze the different trade-offs associated with such devices. This will be used to explore some EMCCD-related issues encountered on FIREBall-2 and present some recent and potential future upgrade strategies (controller upgrade, red-blocking filter, over-spill register implementation, etc.) to mitigate them.
", "doi": "10.1117/1.jatis.11.1.011206", "issn": "2329-4124", "publisher": "SPIE-Intl Soc Optical Eng", "publication": "Journal of Astronomical Telescopes, Instruments, and Systems", "publication_date": "2025-01-02", "series_number": "01", "volume": "11", "issue": "01", "pages": "011206" } ]