Hubble Space Telescope Research Articles

A Revised Density Estimate for the Largest Known Exoplanet, HAT-P-67 b

Abstract Low-density (ρ p < 0.1 g cm−3) hot Saturns are expected to quickly (<100 Myr) lose their atmospheres owing to stellar irradiation, explaining their rarity. HAT-P-67 b seems to be an exception, with ρ p < 0.09 g cm−3 and maintaining its atmosphere to well after 1 Gyr. We present a photometric and spectroscopic follow-up of HAT-P-67 b to determine how it avoided mass loss. HAT-P-67 b orbits a V = 10.1 evolved F-type star in a 4.81-day orbit. We present new radial velocity observations of the system from the NEID spectrograph on the WIYN 3.5 m Telescope from a follow-up campaign robust to stellar activity. We characterize the activity using photometry and activity indicators, revealing a stellar rotation period (5.40 ± 0.09 days) near HAT-P-67 b’s orbital period. We mitigate the stellar activity using a constrained quasi-periodic Gaussian process through a joint fit of archival ground-based photometry, TESS photometry, and our NEID observations, obtaining a planetary mass of M p = 0.45 M J ± 0.15 M J. Combined with a radius measurement of R p = 2.140 R J ± 0.025 R J, this yields a density of ρ p = 0.06 1 − 0.021 + 0.020 g cm − 3 , making HAT-P-67 b the second-lowest-density hot giant known to date. We find that the recent evolution of the host star caused mass loss for HAT-P-67 b to only recently occur. The planet will be tidally disrupted/engulfed in ∼150–500 Myr, shortly after losing its atmosphere. With rapid atmospheric mass loss, a large helium leading tail, and upcoming observations with the Hubble Space Telescope, HAT-P-67 b is an exceptional target for future studies, for which an updated mass measurement provides important context.

Status Report on the Chicago-Carnegie Hubble Program (CCHP): Measurement of the Hubble Constant Using the Hubble and James Webb Space Telescopes

Abstract We present the latest results from the Chicago-Carnegie Hubble Program to measure the Hubble constant, using data from the James Webb Space Telescope (JWST). The overall program aims to calibrate three independent methods: (1) tip of the red giant branch (TRGB) stars, (2) J-region asymptotic giant branch (JAGB) stars, and (3) Cepheids. To date, our program includes 10 nearby galaxies, hosting 11 Type Ia supernovae (SNe Ia) suitable for measuring the Hubble constant (H 0). It also includes the galaxy NGC 4258, whose geometric distance provides the zero-point calibration. In this paper, we discuss our results from the TRGB and JAGB methods. Our current best (highest-precision) estimate is H 0 = 70.39 ± 1.22 (stat) ± 1.33 (sys) ± 0.70 (σ SN), based on the TRGB method alone, with a total of 24 SN Ia calibrators from both Hubble Space Telescope and JWST data. Based on our new JWST data only, and tying into SNe Ia, we find values of H 0 = 68.81 ± 1.79 (stat) ± 1.32 (sys) for the TRGB, and H 0 = 67.80 ± 2.17 (stat) ± 1.64 (sys) km s−1 Mpc−1 for the JAGB method. The distances measured using the TRGB and the JAGB methods agree, on average, at a level better than 1%, and with the SHoES Cepheid distances at just over the 1% level. Our results are consistent with the current standard Lambda cold dark matter (ΛCDM) model, without the need for the inclusion of additional new physics. Future JWST data will be required to increase the precision and accuracy of the local distance scale.

Coevolution of halo and quasar properties in dense environments: CARLA J1017+6116 at z=2.8

Radio-loud active galactic nuclei, in particular radio-loud quasars, are fueled by accretion onto supermassive black holes and are among the most energetic sources in the Universe. While their impact on their surroundings — from the interstellar medium to the circumgalactic medium — is well recognized, the specific mechanisms remain uncertain. In this study we analyze deep Keck Cosmic Web Imager observations of the Lyα halo surrounding the radio-loud quasar at the center of the cluster CARLA J1017+6116 at z = 2.8. As is known from previous observations, the cluster hosts a high fraction of early-type galaxies, and the star formation of its spectroscopically confirmed cluster members is typical of or higher than that of galaxies on the main sequence. We find that the Lyα halo extends at least 16 (128 physical kpc) to a level of surface brightness of 10^-19 with a total observed Lyα luminosity of $ 43.35±0.05 log_ L_⊙ $. The halo has distinct kinematic regions with asymmetries suggestive of complex interactions between the quasar and the intracluster medium, possibly driven by a combination of biconical feedback and episodic activity. Despite the quasar classification, our reanalysis of very long baseline interferometry data finds no evidence of extended jet structures; we instead find compact and variable radio emission that could indicate episodic jet activity or suppression by the dense interstellar medium. Combining these observations with imaging obtained with the Hubble Space Telescope, we identified one Lyα-emitting source within the quasar halo. While mechanical feedback from a jet appears limited or episodic, radiative feedback likely plays a dominant role in shaping the extended Lyα halo, highlighting the complex interplay between quasar-driven processes and the surrounding dense environment.

Denoising Diffusion Probabilistic Model for Realistic and Fast Generated Euclid-like Data for Weak Lensing Analysis

Abstract Understanding and mitigating measurement systematics in weak lensing (WL) analysis requires large data sets of realistic galaxies with diverse morphologies and colors. Missions like Euclid, the Nancy Roman Space Telescope, and Vera C. Rubin Observatory’s Legacy Survey of Space and Time will provide unprecedented statistical power and control over systematic uncertainties. Achieving the stringent shear measurement requirement of ∣m∣ < 10−3 demands analyzing 109 galaxies. Accurately modeling galaxy morphology is crucial, as it is shaped by complex astrophysical processes that are not yet fully understood. Subtle deviations in shape and structural parameters can introduce biases in shear calibration. The interplay between bulges, disks, star formation, and mergers contributes to morphological diversity, requiring simulations that faithfully reproduce these features to avoid systematics in shear measurements. Generating such a large and realistic data set efficiently is feasible using advanced generative models like denoising diffusion probabilistic models. In this work, we extend Hubble Space Telescope (HST) data across Euclid’s broad optical band using the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey and develop a generative AI tool to produce realistic Euclid-like galaxies while preserving morphological details. We validate our tool through visual inspection and quantitative analysis of galaxy parameters, demonstrating its capability to simulate realistic Euclid galaxy images, which will address WL challenges and enhance calibration for current and future cosmological missions.

Dynamic infrared aurora on Jupiter

Auroral emissions are an important diagnostic for a planet’s magnetosphere and upper atmosphere. At the outer planets, the characteristics of emission from the triatomic hydrogen ion H3+ are key to understanding the auroral energy budget. We present James Webb Space Telescope observations of Jupiter’s infrared auroral H3+ emission, exhibiting variability on timescales down to seconds. Together with simultaneous Hubble Space Telescope ultraviolet observations, these results imply an auroral H3+ lifetime of 150 s, and that H3+ cannot efficiently radiate heat deposited by bursty auroral precipitation. However, H3+ radiation is particularly efficient in a dusk active region, which has no significant ultraviolet counterpart. The cause of such emission is unclear. We also present observations of rapid eastward-travelling auroral pulses in the dawn side auroral region and pulsations that propagate rapidly along the Io footprint tail. Together, these observations open a diagnostic window for the jovian magnetosphere and ionosphere.

A JWST project on 47 Tucanae. Binaries among multiple populations

Almost all globular clusters (GCs) contain multiple stellar populations consisting of stars with varying helium and light-element abundances. These populations include first-population stars, which exhibit similar chemical compositions as halo-field stars with comparable Fe/H and second-population stars, characterized by higher helium and nitrogen abundances along with reduced levels of oxygen and carbon. Nowadays, one of the most intriguing open questions about GCs pertains to the formation and evolution of their multiple populations. Recent works based on N-body simulations of GCs show that the fractions and characteristics of binary stars can serve as dynamic indicators of the formation period of multiple-population GCs and their subsequent dynamical evolution. Nevertheless, the incidence of binaries among multiple populations is still poorly studied. Moreover, the few available observational studies focus only on the bright stars of a few GCs. We used deep images of the GC 47,Tucanae collected with the James Webb and the Hubble space telescopes to investigate the incidence of binaries among multiple populations of M dwarfs and bright main-sequence stars. To reach this objective, we used UV, optical, and near-infrared filters to construct photometric diagrams that allowed us to disentangle binary systems and multiple populations. Moreover, we compared these observations with a large sample of simulated binaries. In the cluster central regions, the incidence of binaries among first-population stars is only slightly higher than that of second-population stars. In contrast, in the external regions, the majority of the studied binaries (≳ 85 %) are composed of first-population stars. These results are consistent with the GC formation scenarios in which the second-population stars originate in the cluster's central region, forming a compact and dense stellar group within a more extended system of first-population stars.

The Hubble Missing Globular Cluster Survey. I. Survey overview and the first precise age estimate for ESO452-11 and 2MASS-GC01

We present the Hubble Missing Globular Cluster Survey (MGCS), a Hubble Space Telescope Treasury Program dedicated to the observation of all kinematically confirmed Milky Way globular clusters that missed previous Hubble imaging. After introducing the aims of the programme and describing its target clusters, we showcase the first results of the survey. These are related to two clusters, one located at the edge of the Milky Way bulge and observed in optical bands, namely ESO452-11, and one located in the Galactic disc observed in the near-IR, namely 2MASS-GC01. For both clusters, the deep colour-magnitude diagrams obtained from the MGCS observations reach several magnitudes below their main-sequence turn-off and thus enable the first precise estimate of their age. By using the methods developed in the Cluster Ages to Reconstruct the Milky Way Assembly (CARMA) project, we find ESO452-11 to be an old metal-intermediate globular cluster, with $ M/H ≃-0.80^ $ and an age of $ t $ Gyr. Its location on the age-metallicity relation makes it consistent with an in situ origin, in agreement with its dynamical properties. On the other hand, the results for 2MASS-GC01 highlight it as a young metal-intermediate cluster, with an age of $ t $ Gyr at $ M/H $. Despite the large associated uncertainty, our age estimate for this extremely extincted cluster indicates it to be either the youngest globular cluster known to date or a massive and compact open cluster, which is consistent with its almost circular, disc-like orbit.

Late-time HST and JWST Observations of GRB 221009A: Evidence for a Break in the Light Curve at 50 days

Abstract GRB 221009A is one of the brightest transients ever observed, with the highest peak gamma-ray flux for a gamma-ray burst (GRB). A Type Ic-BL supernova (SN), SN 2022xiw, was definitively detected in late-time JWST spectroscopy (t = 195 days, observer frame). However, photometric studies have found SN 2022xiw to be less luminous (10%−70%) than the canonical GRB-SN, SN 1998bw. We present late-time Hubble Space Telescope (HST)/WFC3 and JWST/NIRCam imaging of the afterglow and host galaxy of GRB 221009A at t ∼185, 277, and 345 days post-trigger. Our joint archival ground, HST, and JWST light-curve fits show strong support for a break in the light-curve decay slope at t = 50 ± 10 days (observer frame) and a SN at <1.5× the optical/near-IR flux of SN 1998bw. This break is consistent with an interpretation as a jet break when requiring slow-cooling electrons in a wind medium with an electron energy spectral index p > 2 and ν m < ν c . Our light curves and joint HST/JWST spectral energy distribution (SED) also show evidence for the late-time emergence of a bluer component in addition to the fading afterglow and SN. We find consistency with the interpretations that this source is either a young, massive, low-metallicity star cluster or a scattered-light echo of the afterglow with a SED shape of f ν ∝ ν 2.0±1.0.

Stellar Populations and Molecular Gas Composition in the Low-metallicity Environment of WLM

Abstract We investigate the stellar populations and molecular gas properties of a star-forming region within the dwarf irregular (dIrr) galaxy Wolf–Lundmark–Mellote (WLM). Low-metallicity dIrrs like WLM offer a valuable window into star formation in environments that are unlike those of larger, metal-rich galaxies such as the Milky Way. In these conditions, carbon monoxide (CO), typically used to trace molecular clouds, is more easily photodissociated by ultraviolet (UV) radiation, leading to a larger fraction of CO-dark molecular gas, where H2 exists without detectable CO emission, or CO-dark gas in the form of cold H i. Understanding the molecular gas content and the stellar populations in these star-forming regions provides important information about the role of CO-bright and CO-dark gas in forming stars. Using Hubble Space Telescope imaging across five Wide Field Camera 3 UVIS bands and CO observations from the Atacama Large Millimeter Array, we examine stellar populations within and outside CO cores and the photodissociation region. Our findings indicate similar physical characteristics such as age and mass across the different environments. Assuming 2% of molecular gas is converted to stars, we estimate the molecular gas content and determine that CO-dark gas constitutes a large fraction of the molecular reservoir in WLM. These results are consistent with molecular gas estimates using a previous dust-derived CO-to-H2 conversion factor (α CO) for WLM. These findings highlight the critical role of CO-dark gas in low-metallicity star formation.

The Gaseous Blowout of the 30 Doradus Starburst Region in the LMC

Abstract Widespread galactic winds emanate from the Large Magellanic Cloud (LMC), with the 30 Doradus starburst region generating the fastest and most concentrated gas flows. We report on the gas distribution, kinematics, and ionization conditions of the near-side outflow along eight down-the-barrel sightlines using UV absorption-line observations from the Hubble Space Telescope's Ultraviolet Legacy Library of Young Stars as Essential Standards (ULLYSES) program for this region along with H i 21 cm observations from the Parkes Galactic All-Sky Survey (GASS) and Galactic Australian Square Kilometre Array Pathfinder (GASKAP) survey. We find that within Δθ ≲ 1 . ° 7 from the center of 30 Doradus, the wind reaches maximum speeds of 100–150 km s−1 from the LMC’s disk. The total integrated column densities of low ions (O i, Si ii, and Fe ii) in the blueshifted wind, up to v LSR = 150 km s−1, are highest near the center and decline radially outward. We estimate an outflow mass of M outflow, Si ii ≈ (5.7–8.6) × 105 M ⊙, outflow rate of M ̇ outflow ≳ 0.02 M ⊙ yr − 1 , and mass loading factor of η ≳ 0.10 within Δθ ≲ 0 . ° 52 from the center of 30 Doradus. The observed ion ratios—together with photoionization modeling—reveal that this wind is roughly 40%–97% photoionized. The metallicities and dust depletion patterns of the high-velocity absorbers at v LSR ≈ +120 km s−1 can be explained by either a foreground Milky Way (MW) halo cloud or an outflow from the LMC. For the high ions, Si iv and C iv are broader and kinematically offset from the low ions, suggesting turbulent mixing layers existing in the wind. Finally, our hydrodynamical simulations of the Magellanic Clouds and MW system suggest that the Magellanic Corona can protect the LMC winds from the ram pressure forces exerted by the MW’s halo.

OMEGACat. V. Helium Enrichment in ω Centauri as a Function of Metallicity

Abstract Constraining the helium enhancement in stars is critical for understanding the formation mechanisms of multiple populations in star clusters. However, measuring helium variations for many stars within a cluster remains observationally challenging. We use Hubble Space Telescope photometry combined with MUSE spectroscopic data for over 7200 red giant branch stars in ωCen to measure helium differences between distinct groups of stars as a function of metallicity, separating the impact of helium enhancements from other abundance variations on the pseudo-color (chromosome) diagram. Our results show that stars at all metallicities have subpopulations with significant helium enhancement (ΔY min ≳ 0.11). We find a rapid increase in helium enhancement across low metallicities ([Fe/H] ≃ −2.05 to [Fe/H] ≃ −1.92), with this enhancement leveling out at ΔY = 0.15 at higher metallicities. The fraction of helium-enhanced stars steadily increases with metallicity from 10% at [Fe/H] ≃ −2.04 to over 90% at [Fe/H] ≃ −1.04. From these measurements, we calculate the total mass in helium produced over the cluster’s lifetime, finding M He tot ∼ 2.7 × 1 0 5 M ⊙ . This study is the first to examine helium enhancement across the full range of metallicities in ωCen, providing new insight into its formation history and additional constraints on enrichment mechanisms.

Quasar Milli-lensing and Cold Dark Matter (TNG50) Subhaloes. I. Image Splitting

Abstract We use numerical mass density profiles from the TNG50 simulation to study the impact of gravitational milli-lensing by dark matter subhaloes on the images of lensed quasars. Specifically, we study the formation of subimages and the probability of their detection. For high-concentration density profiles, the mass determines the amplitude of the image splitting, but for less compact subhaloes, the separation between subimages also depends on the interplay between the inner slope of the density profile and the macro-magnification induced by the lens galaxy. For a log-slope m = −2, close to the mean value of TNG50 density profiles, the detection possibilities increase with respect to less steep, commonly used, analytical models. For typical values of the concentration, 104 ≤ C v ≤ 106, and macro-magnification μ ≥ 10, subhaloes in the entire studied mass range (M sh ≥ 3.5 × 108 M ⊙) can produce separations between subimages detectable with the Hubble Space Telescope or JWST. Considering the absence of reported image splitting in optical observations of lensed quasars, we establish an upper limit on the subhaloes mass fraction α 0 mix = 0.005 ± 0.003 , consistent within uncertainties with the abundance of lensing-efficient subhaloes directly inferred from the TNG50 simulation, f TNG mix = 0.01 ± 0.01 . We show that subhalo density profiles that were initially proposed to explain anomalies in the gravitational arcs of three lensed quasar systems, have also the potential to cause observable point image splitting. This presents an intriguing statistical puzzle when comparing the absence of image splitting in 400 quasar images to the three claimed detections of subhaloes in a small sample of modeled gravitational arcs.

Discovery of Two Ultra-diffuse Galaxies with Unusually Bright Globular Cluster Luminosity Functions via a Mark-dependently Thinned Point Process (MATHPOP)

Abstract We present MArk-dependently THinned POint Process (Mathpop), a novel method to infer the globular cluster (GC) counts in ultra-diffuse galaxies (UDGs) and low-surface brightness galaxies (LSBGs). Many known UDGs have a surprisingly high ratio of GC number to surface brightness. However, standard methods to infer GC counts in UDGs face various challenges, such as photometric measurement uncertainties, GC membership uncertainties, and assumptions about the GC luminosity functions (GCLFs). Mathpop tackles these challenges using the mark-dependent thinned point process, enabling joint inference of the spatial and magnitude distributions of GCs. In doing so, Mathpop allows us to infer and quantify the uncertainties in both GC counts and GCLFs with minimal assumptions. As a precursor to Mathpop, we also address the data uncertainties coming from the selection process of GC candidates: we obtain probabilistic GC candidates instead of the traditional binary classification based on the color–magnitude diagram. We apply Mathpop to 40 LSBGs in the Perseus cluster using GC catalogs from a Hubble Space Telescope imaging program. We then compare our results to those from an independent study using the standard method. We further calibrate and validate our approach through extensive simulations. Our approach reveals two LSBGs having GCLF turnover points much brighter than the canonical value with Bayes’ factor being ∼4.5 and ∼2.5, respectively. An additional crude maximum-likelihood estimation and simulation study show that their GCLF TO points are approximately 0.9 mag and 1.1 mag brighter than the canonical value, with p-values of ∼10−8 and ∼10−5, respectively.

The Progenitor Systems of Classical Novae in M31

Abstract We present the first characterization of the statistical relationship between a large sample of novae in M31 and their progenitor stellar populations in the form of a delay time distribution. To this end, we leverage the spatially resolved stellar age distribution of the M31 disk derived from deep Hubble Space Telescope photometry by the Panchromatic Hubble Andromeda Treasury survey and a large catalog of novae in M31. Our delay time distribution has two statistically significant detections: one population of nova progenitors with ages between 2 and 3.2 Gyr and an unnormalized rate of ( 3.7 − 3.5 + 6.8 ± 2.1 ) × 10 − 9 events M ⊙ −1, and another of ages between 7.9 Gyr and the age of the Universe with ( 4.8 − 0.9 + 1.0 ± 0.2 ) × 10 − 9 events M ⊙ −1 (uncertainties are statistical and systematic, respectively). Together with the upper limits we derive at other time bins, these detections are consistent with either a constant production efficiency or a higher production efficiency of novae at earlier delay times.

SN 2024abfo: A partially stripped type II supernova from a yellow supergiant

We present photometric and spectroscopic data of the type IIb supernova (SN) 2024abfo in NGC 1493 (at 11 Mpc). The steroid Terrestrial-impact Last Alert System (ATLAS) survey discovered the object just a few hours after the explosion and observed a fast rise on the first day. Signs of the sharp shock breakout peak and the subsequent cooling phase are observed in the ultraviolet and the bluest optical bands in the first couple of days, while no peak is visible in the reddest filters. Subsequently, in analogy with normal SNe IIb, the light curve of SN 2024abfo rises again in all bands to the broad peak, with the maximum light reached around 1 month after the explosion. Its absolute magnitude at peak is M_r=-16.5±0.1 mag, making it a faint SN IIb. The early spectra are dominated by Balmer lines with broad P-Cygni profiles, indicating ejecta velocity of 22,500 One month after the explosion, the spectra display a transition towards being He-dominated, though the H lines do not completely disappear, supporting the classification of SN 2024abfo as a relatively H-rich SN IIb. We identify the progenitor of SN 2024abfo in archival images of the Hubble Space Telescope, the Dark Energy Survey, and the XMM-Newton space telescope, in multiple optical filters. From its spectral energy distribution, the progenitor is consistent with being a yellow supergiant, having an initial mass of 15 This detection supports an emerging trend of SN IIb progenitors being more luminous and hotter than SN II ones, and being primaries of massive binaries. Within the SN IIb class, fainter events such as SN 2024abfo tend to have cooler and more expanded progenitors than luminous SNe IIb.

HST Transmission Spectra of the Hot Neptune HD 219666 b: Detection of Water and the Challenge of Constraining Both Water and Methane

Abstract Although Neptunian-sized (2–5 R ⊕) planets appear to be extremely common in the Galaxy, many mysteries remain about their overall nature. To date, only 11 Neptunian-sized planets have had their atmospheres spectroscopically characterized, and these observations hint at interesting diversity within this class of planets. Much of our understanding of these worlds and others derive from transmission spectroscopy with the Hubble Space Telescope’s Wide Field Camera 3 (HST/WFC3). One key outcome of HST/WFC3 observations has been the consistent detection of water but no methane in Neptunian atmospheres, though recent James Webb Space Telescope (JWST) observations are potentially starting to overturn this “missing methane” paradigm. In this work, we present the transmission spectrum of the hot Neptune HD 219666 b from 1.1 to 1.6 μm from two transit observations using HST/WFC3 G141. Our fiducial atmospheric retrieval detects water at ∼3σ in HD 219666 b’s atmosphere and prefers no contribution from methane, similar to these previous observations of other planets. Motivated by recent detections of methane in Neptunian atmospheres by JWST, we explore additional models and find that a methane-only scenario could adequately fit the data, though it is not preferred and likely unphysical. We discuss the impact of this methane detection challenge on our understanding of planetary atmospheres based on HST/WFC3 observations alone, and where JWST observations offer a solution.

The R-Process Alliance: Hunting for gold in the near-UV spectrum of 2MASS J05383296–5904280

Context. Over the past few years, the R-Process Alliance (RPA) has successfully carried out a search for stars that are highly enhanced in elements produced via the rapid neutron-capture (r-) process. In particular, the RPA has identified a number of relatively bright, highly r-process-enhanced (r-II) stars, suitable for observations with the Hubble Space Telescope (HST), facilitating abundance derivation of elements such as gold (Au) and cadmium (Cd). Aims. This paper presents the detailed abundances derived for the metal-poor ([Fe/H] = −2.55) highly r-process-enhanced ([Eu/Fe] = +1.29) r-II star 2MASS J05383296–5904280. Methods. One-dimensional local thermodynamic equilibrium (LTE) elemental abundances were derived via equivalent width and spectral synthesis using high-resolution high signal-to-noise near-UV HST/STIS and optical Magellan/MIKE spectra. Results. Abundances were determined for 43 elements, including 26 neutron-capture elements. In particular, abundances of the rarely studied elements Nb, Mo, Cd, Lu, Os, Pt, and Au are derived from the HST spectrum. These results, combined with RPA near-UV observations of two additional r-II stars, increase the number of Cd abundances derived for r-process-enriched stars from seven to ten and Au abundances from four to seven. A large star-to-star scatter is detected for both of these elements, highlighting the need for more detections enabling further investigations, specifically into possible non-LTE effects.

Cosmology with supernova Encore in the strong lensing cluster MACS J0138−2155

We present a comprehensive spectroscopic analysis of MACS J0138−2155, at z = 0.336. It is the first galaxy cluster known to host two strongly lensed supernovae (SNe), Requiem and Encore, and thus provides us with a chance to obtain a reliable H0 measurement from the time delays between multiple images. We took advantage of new spectroscopic data from the Multi Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope, complemented with archival imaging from the Hubble Space Telescope. The MUSE data cover a central 1 arcmin2 of the lensing cluster, for a total depth of 3.7 hours, including 2.9 hours recently obtained by our Target of Opportunity programme. Based on these observations, we release a new spectroscopic catalogue containing reliable redshifts for 107 objects. This includes 50 galaxy cluster members with secure redshift values in the range 0.324 < z < 0.349, and 13 lensed multiple images from four background sources between 0.767 ≤ z ≤ 3.420, including four images of the host galaxy of the two SNe. We exploited the MUSE data to study the stellar kinematics of 14 bright cluster members and two background galaxies, obtaining reliable measurements of their line-of-sight velocity dispersion. Finally, we combined these results with measurements of the total magnitude of the cluster members in the Hubble Space Telescope F160W band to calibrate the Faber-Jackson relation between luminosity and stellar velocity dispersion (L ∝ σv1/α) for the early-type cluster member galaxies, measuring a slope α = 0.25−0.05+0.05 and a scatter of 25−4+6 km s−1 about the relation. We compared the calibrated relation with six other strong lensing clusters in the redshift range 0.31 ≤ z ≤ 0.59, finding a general agreement and no clear sign of evolution with redshift. A pure and complete sample of cluster member galaxies and a reliable characterisation of their total mass structure are key to building accurate total mass maps of the cluster and mitigating the impact of parametric degeneracies, which is necessary for inferring the value of H0 from the measured time delays between the lensed images of the two SNe.

Exploring the atmosphere of GJ 1132 b with CRIRES+

With a mass, radius, and mean density similar to Earth’s, the rocky planet GJ 1132 b is the first truly small planet for which an atmosphere detection was proposed. If confirmed, ultra-reduced magma outgassing is the only mechanism capable of producing HCN and H2O in large enough quantities to match the Hubble Space Telescope observations. The proposed atmosphere detection, however, was challenged by reanalysis of the same HST data by different teams. Recent James Webb Space Telescope observations returned ambiguous results due to the unaccounted for variability seen between two different visits. Here we report the analysis of three CRIRES+ transit observations of GJ 1132 b in order to determine the presence or absence of He I, HCN, CH4, and H2O in its atmosphere. We are unable to detect the presence of any of these species in the atmosphere of GJ 1132 b assuming a clear, H2-dominated atmosphere, although we can place upper limits for the volume mixing ratios of CH4, HCN, and H2O using injection tests and atmospheric retrievals. These retrieved upper limits show the capability of CRIRES+ at detecting chemical species in rocky exoplanets, if the atmosphere is H2 dominated. The detection of the atmospheres of small planets with high mean molecular weight, and the capability to distinguish between the variability introduced by stellar activity and/or the planetary atmosphere will require high-resolution spectrographs in the upcoming extremely large telescopes.

Searching for exotic object companions in the dense core of NGC 362

The dense cores of globular clusters (GCs) are efficient environments for the production of exotic stellar populations, including millisecond pulsars (MSPs), low-mass X-ray binaries (LMXBs), and cataclysmic variables (CVs). Most of these objects likely form through two- and three-body interactions and are useful tracers of the cluster’s dynamical evolution. In this work, we explore the exotic object population in the galactic GC NGC 362, searching for the optical counterpart of 33 X-ray sources identified within 1′ from the cluster centre. To this end, we exploited a large Hubble Space Telescope dataset obtained in eight different epochs and covering a wavelength range from the near UV to the optical I band. To identify the most promising counterparts, we followed a multi-step analysis based on four main ingredients, namely, positional coincidence, position in the colour–magnitude diagrams, Hα excess, and photometric variability. In addition, we complemented the photometric analysis with spectroscopic information coming from the analysis of MUSE radial velocity curves. Thanks to this multi-diagnostic approach, we were able to identify 28 high-confidence optical counterparts, including several candidate MSPs, active binaries, and CVs. The most intriguing counterparts include a candidate black widow system, an eclipsing binary blue straggler, and a system in outburst, potentially representing either an LMXB or a nova eruption from a CV. The candidate MSPs proposed in this work will contribute to ongoing radio analyses with MeerKAT for the identification and detailed study of MSPs in NGC 362.