Phillip N. Appleton

We present JWST MIRI medium-resolution spectrometer (MRS), NIRSpec, NIRCam, and MIRI imaging observations of 3C 305, a radio galaxy with a compact jet that is confined within the galaxy. We utilize the H ₂ 0–0 S(1)–S(7) lines, several mid-infrared (MIR) fine structure lines, and polycyclic aromatic hydrocarbon (PAH) emission in the MIRI MRS spectrum to conduct a multiphase study of the radio jet’s impact on the interstellar medium. Multiple tracers, including H ₂ /PAH 11.3 μ m and [Fe II ] 5.34 μ m, provide evidence for shocks at the jet termination locations. Two Gaussian components are required to reproduce the kinematics of warm H ₂ adequately, with one representing the bulk low-velocity component, while the other corresponds to an outflow. The ionized gas attains higher outflow velocities than the H ₂ outflow. The stark increase in velocities at the jet hotspots points to jet-driven outflows. We fit the H ₂ excitation diagram with a power-law temperature distribution and find that the hotspots exhibit flatter slopes, indicating a larger warm/hot gas mass fraction at these locations. Our MAPPINGS line-ratio analysis indicates that most of the MIR ionized gas can be fit by a “shock+precursor” model. We find that strong radiative losses dominated by line cooling, along with moderate kinetic power of the molecular + ionized gas outflows, can account for all of the estimated jet power, indicating high jet coupling efficiency in 3C 305. Our results, in tandem with other studies on multiphase gas, show that jets efficiently shock-heat and accelerate the gas that comes in contact with them, driving massive, kiloparsec-scale, multiphase outflows.

We present new MeerKAT 21 cm line observations of the neutral hydrogen gas in the compact galaxy group Stephan’s Quintet. These data provide a significantly improved view of the atomic gas distribution and kinematics in the group. New features include the first detections of H i associated with member galaxies NGC 7319 and NGC 7320C, the identification of a high-velocity H i component associated with SQ-A, and the detection of additional H i at low velocities filling the area of the NGC 7318B disk. We also find H i in the previously detected gas bridge linking NGC 7319 and NGC 7318B, and a new northern bridge linking NGC 7319 to the SQ-A star formation region. We detect H i with a wide range of velocities along the line of sight through the northern half of the famous shock ridge, including in the 6200–6500 km s ⁻¹ velocity range occupied by shocked H α emission. We examine the morphology and velocity structure of the H i and consider the origins of different components, finding some evidence that while the gas associated with NGC 7318B has been disturbed by its collision with the group, it may still retain a component of disk rotation. We find no gaseous connection between the tidal tails and NGC 7320C, but reaffirm the close connection between the shocked gas in the ridge (traced by X-ray, radio continuum, and warm H ₂ emission) and the southern tidal tail. Based on the integrated spectrum, we find a total H i mass in the group of 3.5 ± 0.4 × 10 ¹⁰ M _⊙ , higher than the Very Large Array estimate and comparable to FAST.

ESA’s Euclid cosmology mission relies on the very sensitive and accurately calibrated spectroscopy channel of the Near-Infrared Spectrometer and Photometer (NISP). With three operational grisms in two wavelength intervals, NISP provides diffraction-limited slitless spectroscopy over a field of 0.57 deg ² . A blue grism, BG _E , covers the wavelength range 926–1366 nm at a spectral resolution (ℛ) of 440–900 for a 0.″5 diameter source with a dispersion of 1.24 nm px ⁻¹ . Two red grisms, RG _E , span 1206 to 1892 nm at ℛ = 550–740 and a dispersion of 1.37 nm px ⁻¹ . We describe the construction of the grisms as well as the ground testing of the flight model of the NISP instrument, where these properties were established.

Stephan’s Quintet (SQ) is a local compact galaxy group system that exhibits significant star formation activity. A history of tidal interactions between its four member galaxies and a recent collision between an intruder galaxy and the original group are associated with active star formation, particularly in many shocked regions in the intragroup medium. Using an existing star cluster candidate (SCC) catalog constructed from Hubble Space Telescope (HST) UV/optical images, we integrate flux measurements from five near-infrared filters (F090W, F150W, F200W, F277W, and F356W) obtained from JWST NIRCam observations in 2022. Leveraging the extended photometric baseline from HST and JWST, spanning ∼300 to ∼3500 nm, we perform spectral energy distribution (SED) fitting using the C igale code to derive reliable estimates of age, mass, and extinction for the 1588 high-confidence SCCs. We confirm earlier results that very young SCCs (∼a few Myr) are predominantly located along previously identified shock regions near the merging galaxies, while older (>100 Myr) and globular clusters are more widely distributed. Our analysis shows that near-IR photometry helps break the age–extinction degeneracy, reclassifying many SCCs from older to younger, moderately dust-extincted clusters when added to HST-based SED fits. We also observe a strong spatial correlation between young clusters and CO-traced molecular gas, although active star formation is present in several regions with no detectable CO. We find that the two prominent epochs of star formation, around 5 and 200 Myr, correspond to the two major interaction events in SQ that gave rise to the observed extended tidal features.

We present new observational evidence supporting the hypothesis that SQ-A, a starburst in the intragroup medium (IGrM) of Stephan’s Quintet (SQ), is triggered by a high-speed collision between two gas systems, one associated with the IGrM (v ∼ 6900 km s⁻¹) and another with the intruder galaxy NGC 7318b (v ∼ 6000 km s⁻¹). The new CO(2–1) data set from the Atacama Large Millimeter/submillimeter Array has angular resolutions between 0 . ″ 2 and 7 . ″ 0 and the new Very Large Array H i data cube has an angular resolution of 6 . ″ 6 × 7 . ″ 9 . The CO maps show that the two gas systems are bridged by another system with an intermediate velocity of ∼6600 km s⁻¹, whereas the H i data show that the component of v ∼ 6600 km s⁻¹ fits well into a gap in the more extended v ∼ 6000 km s⁻¹ component, albeit with a displacement of ∼5 kpc. Both the bridge and the complementary distributions between different gas systems are common features of starbursts triggered by cloud–cloud collision. An analysis of clumps (sizes of 100–200 pc) reveals very diversified star formation (SF) activity in clumps belonging to different kinematic systems, with the molecular gas depletion time of the v ∼ 6900 km s⁻¹ clumps being more than 10 times longer than that of the v ∼ 6600 km s⁻¹ clumps. The results are consistent with a scenario in which the enhanced SF activity (and the starburst) in the system of v ∼ 6600 km s⁻¹ is due to gas compression generated in cloud–cloud collisions, whereas the suppression of SF in the v ∼ 6900 km s⁻¹ system is due to vortices (i.e. gas rotation) generated in more complex collisions involving dense clouds and diffuse intercloud gas associated with high-speed shocks.

We present new observational evidence supporting the hypothesis that SQ-A, a starburst in the intra-group medium (IGrM) of Stephan's Quintet (SQ), is triggered by a high-speed collision between two gas systems, one associated with the IGrM (v~6900 km/s) and another with the intruder galaxy NGC7318b (v~6000 km/s). The new ALMA CO(2-1) dataset has angular resolutions between 0.2" and 7.0" and the new VLA HI datacube an angular resolution of 6.6" * 7.9". The CO maps show that the two gas systems are bridged by another system with an intermediate velocity of ~6600 km/s, whereas the HI data show that the component of v~6600 km/s fits well into a gap in the more extended v~6000 km/s component, albeit with a displacement of ~5 kpc. Both the bridge and the complementary distributions between different gas systems are common features of starbursts triggered by cloud-cloud collision. An analysis of clumps (sizes of 100--200 pc) reveals very diversified star formation (SF) activity in clumps belonging to different kinematic systems, with the molecular gas depletion time of the v~6900 km/s clumps more than 10 times longer than that of the v~6600 km/s clumps. The results are consistent with a scenario in which the enhanced SF activity (and the starburst) in the system of v~6600 km/s is due to gas compression generated in cloud-cloud collisions, whereas the suppression of SF in the v~6900 km/s system is due to vortices (i.e. gas rotation) generated in more complex collisions involving dense clouds and diffuse intercloud gas accompanied by blast-wave shocks.

The Near-Infrared Spectrometer and Photometer (NISP) on board the Euclid satellite provides multiband photometry and R ≳ 450 slitless grism spectroscopy in the 950–2020 nm wavelength range. In this reference article, we illuminate the background of NISP’s functional and calibration requirements, describe the instrument’s integral components, and provide all its key properties. We also sketch the processes needed to understand how NISP operates and is calibrated as well as its technical potentials and limitations. Links to articles providing more details and the technical background are included. The NISP’s 16 HAWAII-2RG (H2RG) detectors with a plate scale of 0″.3 pixel⁻¹ deliver a field of view of 0.57 deg². In photometric mode, NISP reaches a limiting magnitude of ~24.5 AB mag in three photometric exposures of about 100 s in exposure time for point sources and with a S/N of five. For spectroscopy, NISP’s pointsource sensitivity is a signal-to-noise ratio = 3.5 detection of an emission line with flux ~2 × 10⁻¹⁶ erg s⁻¹ cm⁻² integrated over two resolution elements of 13.4 Å in 3 × 560 s grism exposures at 1.6 µm (redshifted Hα). Our calibration includes on-ground and in-flight characterisation and monitoring of the pixel-based detector baseline, dark current, non-linearity, and sensitivity to guarantee a relative photometric accuracy better than 1.5% and a relative spectrophotometry better than 0.7%. The wavelength calibration must be accurate to 5 Å or better. The NISP is the state-of-the-art instrument in the near-infrared for all science beyond small areas available from HST and JWST – and it represents an enormous advance from any existing instrumentation due to its combination of field size and high throughput of telescope and instrument. During Euclid’s six-year survey covering 14 000 deg² of extragalactic sky, NISP will be the backbone in determining distances of more than a billion galaxies. Its near-infrared data will become a rich reference imaging and spectroscopy data set for the coming decades.

The Euclid space mission aims to investigate the nature of dark energy and dark matter by mapping the large-scale structure of the Universe. A key component of Euclid's observational strategy is slitless spectroscopy, conducted using the Near Infrared Spectrometer and Photometer (NISP). This technique enables the acquisition of large-scale spectroscopic data without the need for targeted apertures, allowing precise redshift measurements for millions of galaxies. These data are essential for Euclid's core science objectives, including the study of cosmic acceleration and the evolution of galaxy clustering, as well as enabling many non-cosmological investigations. This study presents the SIR processing function (PF), which is responsible for processing slitless spectroscopic data. The objective is to generate science-grade fully-calibrated one-dimensional spectra, ensuring high-quality spectroscopic data. The processing function relies on a source catalogue generated from photometric data, effectively corrects detector effects, subtracts cross-contaminations, minimizes self-contamination, calibrates wavelength and flux, and produces reliable spectra for later scientific use. The first Quick Data Release (Q1) of Euclid's spectroscopic data provides approximately three million validated spectra for sources observed in the red-grism mode from a selected portion of the Euclid Wide Survey. We find that wavelength accuracy and measured resolving power are within requirements, thanks to the excellent optical quality of the instrument. The SIR PF represents a significant step in processing slitless spectroscopic data for the Euclid mission. As the survey progresses, continued refinements and additional features will enhance its capabilities, supporting high-precision cosmological and astrophysical measurements.

This paper describes the near-infrared processing function (NIR PF) that processes near-infrared images from the Near-Infrared Spectrometer and Photometer (NISP) instrument onboard the Euclid satellite. NIR PF consists of three main components: (i) a common pre-processing stage for both photometric (NIR) and spectroscopic (SIR) data to remove instrumental effects; (ii) astrometric and photometric calibration of NIR data, along with catalogue extraction; and (iii) resampling and stacking. The necessary calibration products are generated using dedicated pipelines that process observations from both the early performance verification (PV) phase in 2023 and the nominal survey operations. After outlining the pipeline's structure and algorithms, we demonstrate its application to Euclid Q1 images. For Q1, we achieve an astrometric accuracy of 9-15 mas, a relative photometric accuracy of 5 mmag, and an absolute flux calibration limited by the 1% uncertainty of the Hubble Space Telescope (HST) CALSPEC database. We characterise the point-spread function (PSF) that we find very stable across the focal plane, and we discuss current limitations of NIR PF that will be improved upon for future data releases.

We present Chandra and XMM-Newton X-ray observations of the compact group HCG 57, and optical integral field spectroscopy of the interacting galaxy pair HCG 57A/D. These two spiral galaxies recently suffered an off-axis collision with HCG 57D passing through the disk of A. We find evidence of a gas bridge linking the galaxies, containing ∼10⁸ M _⊙ of hot, ∼1 keV thermal plasma and warm ionized gas radiating in Hα, Hβ, [O iii] and [N ii] lines. The optical emission lines in the central regions of HCG 57D show excitation properties consistent with H ii-regions, while the outer rim of HCG 57D parts of the bridge and the outer regions of HCG 57A show evidence of shocked gas consistent with shock velocities of 200–300 km s⁻¹. In contrast, the X-ray emitting gas requires a collision velocity of 650–750 km s⁻¹ to explain the observed temperatures. These different shock velocities can be reconciled by considering the contributions of rotation to collision velocity in different parts of the disks, and the clumpy nature of the preshock medium in the galaxies, which likely lead to different shock velocities in different components of the turbulent postshocked gas. We examine the diffuse X-ray emission in the group members and their associated point sources, identifying X-ray active galactic nuclei in HCG 57A, B, and D. We also confirm the previously reported ∼1 keV intra-group medium and find it to be relaxed with a low central entropy (18.0 ± 1.7 keV cm² within 20 kpc) but a long cooling time (5.9 ± 0.8 Gyr).