Measurements of three exo-planetesimal compositions: a planetary core, a chondritic body, and an icy Kuiper belt analogue
arXiv:2506.19931v1 Announce Type: new
Abstract: The study of planetesimal debris accreted by white dwarfs offers unique insights into the composition of exoplanets. Using far-ultraviolet and optical spectroscopy, we have analysed the composition of planetesimals accreted by three metal enriched H-dominated white dwarfs with effective temperatures of T_eff = 20 000 K. WD 0059+257 is accreting an object composed of 71.8 +/- 7.9 per cent Fe and Ni by mass, indicating a large core mass fraction of 69 per cent, similar to that of Mercury. We model this planetesimal as having a differentiated Earth-like composition with 65 per cent of its mantle stripped, and we find this mass loss can be caused by vaporisation of the planetesimal's mantle during post-main sequence evolution. The tentative S detection in WD 0059+257 is a possible clue to the nature of the light element in planetary cores, including that of the Earth. The volatile-rich composition of WD 1943+163 is consistent with accretion of a carbonaceous chondrite-like object, but with an extreme Si depletion. WD 1953-715 accretes a planetesimal which contains 64 +/- 21 per cent of O in the form of ices, likely H2O. This body therefore requires an initial orbit at formation beyond a radial distance of > 100 au for ice survival into the white dwarf phase. These three planetary enriched white dwarfs provide evidence of differing core fractions, volatile budgets, and initial orbital separations of the accreted planetesimals, all of which help us understand their formation and evolutionary history.
Studying stellar populations in Omega Centauri with phylogenetics
arXiv:2504.01813v2 Announce Type: replace
Abstract: The nature and formation history of our Galaxy's largest and most enigmatic stellar cluster, known as Omega Centauri (ocen) remains debated. Here, we offer a novel approach to disentangling the complex stellar populations within ocen based on phylogenetics methodologies from evolutionary biology. These include the Gaussian Mixture Model and Neighbor-Joining clustering algorithms applied to a set of chemical abundances of ocen stellar members. Instead of using the classical approach in astronomy of grouping them into separate populations, we focused on how the stars are related to each other. In this way, we could identify stars that likely formed in globular clusters versus those originating from prolonged in-situ star formation and how these stars interconnect. Our analysis supports the hypothesis that ocen might be a nuclear star cluster of a galaxy accreted by the Milky Way with a mass of about 10^9M_sun. Furthermore, we revealed the existence of a previously unidentified in-situ stellar population with a distinct chemical pattern unlike any known population found in the Milky Way to date. Our analysis of ocen is an example of the success of cross-disciplinary research and shows the vast potential of applying evolutionary biology tools to astronomical datasets, opening new avenues for understanding the chemical evolution of complex stellar systems.
An LBT view of the co-rotating group of galaxies around NGC 2750: Deep imaging and new satellite candidates
arXiv:2506.19001v1 Announce Type: new
Abstract: Some galaxies such as the Milky Way and Andromeda display coherently rotating satellite planes, posing tensions with cosmological simulations. NGC 2750 has emerged as an additional candidate system hosting a co-rotating group of galaxies. We aim to assess the presence of a coherent satellite plane around NGC 2750 by identifying new candidate dwarf galaxies and low surface brightness features. We conducted deep, wide-field photometric observations of NGC 2750 using the Large Binocular Telescope in the g- and r-bands. Standard data reduction techniques were applied to enhance the detection of low-surface-brightness features down to about 31 mag/arcsec^2 in r. Our observations led to the discovery of six new candidate dwarf galaxies, including one with properties consistent with an ultra-diffuse galaxy. We also identified tidal features around NGC 2750, indicating past interactions with nearby satellites. The spatial distribution of satellites suggests a moderate flattening, further supported by the newly identified candidates. Follow-up spectroscopic measurements will be critical in confirming or challenging the strong kinematic coherence observed previously. The luminosity function of NGC 2750 reveals an excess of bright satellites compared to similar systems, adding to the growing tension between observed satellite populations and cosmological simulations.
The Atacama Cosmology Telescope: DR6 Constraints on Extended Cosmological Models
arXiv:2503.14454v2 Announce Type: replace
Abstract: We use new cosmic microwave background (CMB) primary temperature and polarization anisotropy measurements from the Atacama Cosmology Telescope (ACT) Data Release 6 (DR6) to test foundational assumptions of the standard cosmological model and set constraints on extensions to it. We derive constraints from the ACT DR6 power spectra alone, as well as in combination with legacy data from Planck. To break geometric degeneracies, we include ACT and Planck CMB lensing data and baryon acoustic oscillation data from DESI Year-1, and further add supernovae measurements from Pantheon+ for models that affect the late-time expansion history. We verify the near-scale-invariance (running of the spectral index $d n_s/d\ln k = 0.0062 \pm 0.0052$) and adiabaticity of the primordial perturbations. Neutrino properties are consistent with Standard Model predictions: we find no evidence for new light, relativistic species that are free-streaming ($N_{\rm eff} = 2.86 \pm 0.13$, which combined with external BBN data becomes $N_{\rm eff} = 2.89 \pm 0.11$), for non-zero neutrino masses ($\sum m_\nu < 0.082$ eV at 95% CL), or for neutrino self-interactions. We also find no evidence for self-interacting dark radiation ($N_{\rm idr} < 0.134$), early-universe variation of fundamental constants, early dark energy, primordial magnetic fields, or modified recombination. Our data are consistent with standard BBN, the FIRAS-inferred CMB temperature, a dark matter component that is collisionless and with only a small fraction allowed as axion-like particles, a cosmological constant, and the late-time growth rate predicted by general relativity. We find no statistically significant preference for a departure from the baseline $\Lambda$CDM model. In general, models introduced to increase the Hubble constant or to decrease the amplitude of density fluctuations inferred from the primary CMB are not favored by our data.
Euclid: An emulator for baryonic effects on the matter bispectrum
arXiv:2506.18974v1 Announce Type: new
Abstract: The Euclid mission and other next-generation large-scale structure surveys will enable high-precision measurements of the cosmic matter distribution. Understanding the impact of baryonic processes such as star formation and AGN feedback on matter clustering is crucial to ensure precise and unbiased cosmological inference. Most theoretical models of baryonic effects to date focus on two-point statistics, neglecting higher-order contributions. This work develops a fast and accurate emulator for baryonic effects on the matter bispectrum, a key non-Gaussian statistic in the nonlinear regime. We employ high-resolution $N$-body simulations from the BACCO suite and apply a combination of cutting-edge techniques such as cosmology scaling and baryonification to efficiently span a large cosmological and astrophysical parameter space. A deep neural network is trained to emulate baryonic effects on the matter bispectrum measured in simulations, capturing modifications across various scales and redshifts relevant to Euclid. We validate the emulator accuracy and robustness using an analysis of \Euclid mock data, employing predictions from the state-of-the-art FLAMINGO hydrodynamical simulations. The emulator reproduces baryonic suppression in the bispectrum to better than 2$\%$ for the $68\%$ percentile across most triangle configurations for $k \in [0.01, 20]\,h^{-1}\mathrm{Mpc}$ and ensures consistency between cosmological posteriors inferred from second- and third-order weak lensing statistics.
The Simons Observatory: Validation of reconstructed power spectra from simulated filtered maps for the Small Aperture Telescope survey
arXiv:2502.00946v2 Announce Type: replace
Abstract: We present a transfer function-based method to estimate angular power spectra from filtered maps for cosmic microwave background (CMB) surveys. This is especially relevant for experiments targeting the faint primordial gravitational wave signatures in CMB polarisation at large scales, such as the Simons Observatory (SO) small aperture telescopes. While timestreams can be filtered to mitigate the contamination from low-frequency noise, usual methods that calculate the mode coupling at individual multipoles can be challenging for experiments covering large sky areas or reaching few-arcminute resolution. The method we present here, although approximate, is more practical and faster for larger data volumes. We validate it through the use of simulated observations approximating the first year of SO data, going from half-wave plate-modulated timestreams to maps, and using simulations to estimate the mixing of polarisation modes induced by an example of time-domain filtering. We show its performance through an example null test and with an end-to-end pipeline that performs inference on cosmological parameters, including the tensor-to-scalar ratio $r$. The performance demonstration uses simulated observations at multiple frequency bands. We find that the method can recover unbiased parameters for our simulated noise levels.
The JWST/AURORA Survey: Multiple Balmer and Paschen Emission Lines for Individual Star-forming Galaxies at z=1.5-4.4. I. A Diversity of Nebular Attenuation Curves and Evidence for Non-Unity Dust Covering Fractions
arXiv:2506.17396v1 Announce Type: new
Abstract: We present the nebular attenuation curves and dust covering fractions for 24 redshift z=1.5-4.4 star-forming galaxies using multiple Balmer and Paschen lines from the JWST/AURORA survey. Nebular reddening derived from Paschen lines exceeds that from Balmer lines for at least half the galaxies in the sample when assuming the commonly-adopted Galactic extinction curve, implying the presence of optically-thick star formation. The nebular attenuation curves exhibit a broad range of normalizations (Rv ~ 3.2-16.4). Motivated by the offsets in reddening deduced from the Balmer and Paschen lines, and the high Rv values for the individual nebular attenuation curves, both of which suggest variations in the dust-stars geometry, we propose a model with a subunity dust covering fraction (fcov). Fitting such a model to the HI recombination line ratios indicates fcov ~ 0.6-1.0. The normalizations of the nebular attenuation curves, Rv, are driven primarily by fcov and the mix of optically-thick and thin OB associations. Thus, the diversity of nebular attenuation curves can be accommodated by assuming dust grain properties similar to that of Milky Way sightlines but with a subunity covering fraction of dust. Integrated measurements of multiple Balmer and Paschen lines can be used to place novel constraints on the dust covering fraction towards OB associations. These, in turn, provide new avenues for exploring the role of dust and gas covering fraction in a number of relevant aspects of high-redshift galaxies, including the impact of stellar feedback on ISM porosity and the escape of Ly-alpha and Lyman continuum radiation.
A 16 Myr super-Neptune in Upper-Centaurus Lupus and a preliminary survey of transiting planets in Sco-Cen with TESS
arXiv:2502.00576v3 Announce Type: replace
Abstract: Measuring the properties of planets younger than about 50 Myr helps to test different planetary formation and evolution models. NASA's Transiting Exoplanet Survey Satellite (TESS) has observed nearly the entire sky, including a wide range of star-forming regions and young stellar clusters, expanding our census of the newborn planet population. In this work, we present the discovery of the TIC 88785435 planetary system located in the Upper-Centaurus Lupus (UCL) region of the Scorpius-Centaurus OB association (Sco-Cen) and a preliminary survey of the planet population within Sco-Cen. TIC 88785435 is a pre-main sequence, K7V dwarf ($M_\star = 0.72M_\odot$, $R_\star = 0.91R_\odot$, $T_\mathrm{eff}$ = 3998K, V = 11.7 mag) located within the bounds of UCL. We investigate the distribution of rotation periods measured from the TESS long-cadence data and the Halpha and Li abundances from the spectra of TIC 88785435. TESS long-candence data reveal that TIC 88785435 hosts a transiting super-Neptune ($R_b = 5.03R_\oplus$, P = 10.51 days), TIC 88785435 b. Ground-based follow-up validates the planetary nature of TIC 88785435 b. Using the TESS data, we perform a preliminary survey to investigate how TIC 88785435 b compares to the population of newly born planets located within Sco-Cen.
Infall-driven gravitational instability in accretion discs
arXiv:2506.13701v2 Announce Type: replace
Abstract: Gravitational instability (GI) is typically studied in cooling-dominated discs, often modelled using simplified prescriptions such as $\beta$-cooling. In this paper, we investigate the onset and evolution of GI in accretion discs subject to continuous mass injection, combining 1D and 3D numerical simulations. We explore an alternative self-regulation mechanism in which mass replenishment drives the system toward marginal stability $Q\sim 1$. In this regime, the disc establishes a steady-state disc-to-star mass ratio, balancing the mass transported to the central object with that added to the disc. Our 3D simulations reveal that the general scaling predicted from the linear theory are respected, however there are important difference compared to the cooling case in terms of morphology and pattern speed. Unlike the flocculent spirals seen in cooling-driven instability, the power is concentrated towards the dominant modes in infall-driven spirals. Additionally, spiral waves generate at the mass injection location, and propagate at constant pattern speed, unlike in the cooling case. This suggests a fundamental difference in how mass-regulated and cooling-regulated discs behave and transport angular momentum.
The Orbit of WASP-4 b is in Decay
arXiv:2506.15022v1 Announce Type: new
Abstract: WASP-4 b is a hot Jupiter exhibiting a decreasing orbital period, prompting investigations into potential mechanisms driving its evolution. We analyzed 173 transit light curves, including 37 new observations, and derived mid-transit timings with EXOFAST, forming the most extensive TTV dataset for this system. Adding 58 literature timings and removing unreliable data, we constructed a TTV diagram with 216 points. Our analysis considered linear, quadratic, and apsidal motion models, with the quadratic model proving to be significantly superior in all model comparison statistics. We found no significant periodic signals in the data. The quadratic model allows us to infer a tidal quality factor of Q' ~ 80,000 from the orbital decay rate if this is due to stellar tides. Theoretical considerations indicate that such efficient dissipation is possible due to internal gravity waves in the radiative core of WASP-4, but only in our models with a more evolved host star, possibly near the end of its main-sequence lifetime, and with a larger radius than the observed one. Our main-sequence models produce only about a third of the required dissipation (Q' ~ 200,000 - 500,000). Therefore, the observed orbital decay can only be explained by a slightly larger or more evolved host, resembling the case for WASP-12. Our findings highlight the need for further stellar modeling and improvement in our current understanding of tidal dissipation mechanisms driving orbital decay in close-in exoplanetary systems.
The Second and Third Data Releases from the UKIRT Hemisphere Survey
arXiv:2506.14621v1 Announce Type: new
Abstract: This paper describes the second and third data releases (DR2 and DR3, respectively) from the ongoing United Kingdom Infrared Telescope (UKIRT) Hemisphere Survey (UHS). DR2 is primarily comprised of the $K$-band portion of the UHS survey, and was released to the public on June 1, 2023. DR3 mainly includes the $H$-band portion of the survey, with a public release scheduled for September 2025. The $H$- and $K$-band data releases complement the previous $J$-band data release (DR1) from 2018. The survey covers approximately 12,700 square degrees between declinations of 0 degrees and $+$60 degrees and achieves median 5$\sigma$ point source sensitivities of 19.0 mag and 18.0 mag (Vega) for $H$ and $K$, respectively. The data releases include images and source catalogs which include $\sim$581 million $H$-band detections and $\sim$461 million $K$-band detections. DR2 and DR3 also include merged catalogs, created by combining $J$- and $K$-band detections (DR2) and $J$-, $H$-, and $K$-band detections (DR3). The DR2 merged catalog has a total of $\sim$513 million sources, while the DR3 merged catalog contains $\sim$560 million sources.
Extreme AGN feedback in the fossil galaxy group SDSSTG 4436
arXiv:2506.13907v1 Announce Type: new
Abstract: Supermassive black hole feedback is the currently favoured mechanism to regulate the star formation rate of galaxies and prevent the formation of ultra-massive galaxies ($M_\star>10^{12}M_\odot$). However, the mechanism through which the outflowing energy is transferred to the surrounding medium strongly varies from one galaxy evolution model to another, such that a unified model for AGN feedback does not currently exist. The hot atmospheres of galaxy groups are highly sensitive laboratories of the feedback process, as the injected black hole energy is comparable to the binding energy of halo gas particles. Here we report multi-wavelength observations of the fossil galaxy group SDSSTG 4436. The hot atmosphere of this system exhibits a highly relaxed morphology centred on the giant elliptical galaxy NGC~3298. The X-ray emission from the system features a compact core ($<$10 kpc) and a steep increase in the entropy and cooling time of the gas, with the cooling time reaching the age of the Universe $\sim15$ kpc from the centre of the galaxy. The observed entropy profile implies a total injected energy of $\sim1.5\times10^{61}$ ergs, which given the high level of relaxation could not have been injected by a recent merging event. Star formation in the central galaxy NGC~3298 is strongly quenched and its stellar population is very old ($\sim$10.6 Gyr). The currently detected radio jets have low power and are confined within the central compact core. All the available evidence implies that this system was affected by giant AGN outbursts which excessively heated the neighbouring gas and prevented the formation of a self-regulated feedback cycle. Our findings imply that AGN outbursts can be energetic enough to unbind gas particles and lead to the disruption of cool cores.
BEBOP VII. SOPHIE discovery of BEBOP-3b, a circumbinary giant planet on an eccentric orbit
arXiv:2506.14615v1 Announce Type: new
Abstract: Planetary systems orbiting close binaries are valuable testing grounds for planet formation and migration models. More detections with good mass measurements are needed. We present a new planet discovered during the BEBOP survey for circumbinary exoplanets using radial velocities. We use data taken with the SOPHIE spectrograph at the Observatoire de Haute-Provence, and perform a spectroscopic analysis to obtain high precision radial velocities. This planet is the first radial velocity detection of a previously unknown circumbinary system. The planet has a mass of $0.56$ $M_{Jup}$ and orbits its host binary in 550 days with an eccentricity of 0.25. Compared to most of the previously known circumbinary planets, BEBOP-3b has a long period (relative to the binary) and a high eccentricity. There also is a candidate outer planet with a $\sim1400$ day orbital period. We test the stability of potential further candidate signals inside the orbit of BEBOP-3b, and demonstrate that there are stable orbital solutions for planets near the instability region which is where the Kepler circumbinary planets are located. We also use our data to obtain independent dynamical masses for the two stellar components of the eclipsing binary using High Resolution Cross-Correlation Spectroscopy (HRCCS), and compare those results to a more traditional approach, finding them compatible with one another.
Infall-driven gravitational instability in accretion discs
arXiv:2506.13701v1 Announce Type: new
Abstract: Gravitational instability (GI) is typically studied in cooling-dominated discs, often modelled using simplified prescriptions such as $\beta$-cooling. In this paper, we investigate the onset and evolution of GI in accretion discs subject to continuous mass injection, combining 1D and 3D numerical simulations. We explore an alternative self-regulation mechanism in which mass replenishment drives the system toward marginal stability $Q\sim 1$. In this regime, the disc establishes a steady-state disc-to-star mass ratio, balancing the mass transported to the central object with that added to the disc. Our 3D simulations reveal that the general scaling predicted from the linear theory are respected, however there are important difference compared to the cooling case in terms of morphology and pattern speed. Unlike the flocculent spirals seen in cooling-driven instability, the power is concentrated towards the dominant modes in infall-driven spirals. Additionally, spiral waves generate at the mass injection location, and propagate at constant pattern speed, unlike in the cooling case. This suggests a fundamental difference in how mass-regulated and cooling-regulated discs behave and transport angular momentum.
pop-cosmos: Insights from generative modeling of a deep, infrared-selected galaxy population
arXiv:2506.12122v1 Announce Type: new
Abstract: We present an extension of the pop-cosmos model for the evolving galaxy population up to redshift $z\sim6$. The model is trained on distributions of observed colors and magnitudes, from 26-band photometry of $\sim420,000$ galaxies in the COSMOS2020 catalog with Spitzer IRAC $\textit{Ch. 1}<26$. The generative model includes a flexible distribution over 16 stellar population synthesis (SPS) parameters, and a depth-dependent photometric uncertainty model, both represented using score-based diffusion models. We use the trained model to predict scaling relationships for the galaxy population, such as the stellar mass function, star-forming main sequence, and gas-phase and stellar metallicity vs. mass relations, demonstrating reasonable-to-excellent agreement with previously published results. We explore the connection between mid-infrared emission from active galactic nuclei (AGN) and star-formation rate, finding high AGN activity for galaxies above the star-forming main sequence at $1\lesssim z\lesssim 2$. Using the trained population model as a prior distribution, we perform inference of the redshifts and SPS parameters for 429,669 COSMOS2020 galaxies, including 39,588 with publicly available spectroscopic redshifts. The resulting redshift estimates exhibit minimal bias ($\text{median}[\Delta_z]=-8\times10^{-4}$), scatter ($\sigma_\text{MAD}=0.0132$), and outlier fraction ($6.19\%$) for the full $0
Emission-line Stacking of 21cm Intensity Maps with MeerKLASS: Inference Pipeline and Application to the L-band Deep-field Data
arXiv:2504.03908v2 Announce Type: replace
Abstract: We present a novel analysis of observational systematics through the emission-line stacking of the MeerKLASS L-band deep-field intensity maps, following the detection in arXiv:2407.21626. A stacking signal is obtained by stacking the 21cm intensity map cubelets around the galaxy positions from the GAMA survey at $0.39\lesssim z \lesssim0.46$. An extensive simulation framework is built to study the viability of the stacking detection, the covariance estimation, and the model inference, which are then applied to the data. The statistical significance of the detection is $8.66\sigma$ when averaged into an angular map, and $7.45\sigma$ when averaged into a spectrum. The stacked spectrum exhibits an oscillating component of systematics, and we provide evidence that these systematics are a convolutional effect on the map data. The oscillation frequency matches the diffraction from the secondary reflector into the primary beam of the MeerKAT telescope. Bayesian inference can be used to constrain the systematics and the average HI emission of the galaxies. The fitting of the parameters gives a constraint on the systematics frequency $\nu_{\rm sys}\,[{\rm MHz}] = 17.90^{+6.53}_{-4.27}$. The posterior of the systematics amplitude reaches the wide prior and gives $A_{\rm sys}=0.50^{+0.33}_{-0.33}$. A tentative measurement of the average HI mass of the sources is achieved at $\log_{10}[\langle M_{HI}\rangle/M_\odot ]=9.84^{+0.48}_{-0.59}$, which is an underestimation limited by the narrow redshift bin, the strong degeneracy with the systematics, and the low-density galaxy sample. These shortfalls will be resolved for future MeerKLASS data to enable accurate measurements of the HI density through stacking of intensity maps.
Euclid: Relativistic effects in the dipole of the 2-point correlation function
arXiv:2410.06268v2 Announce Type: replace
Abstract: Gravitational redshift and Doppler effects give rise to an antisymmetric component of the galaxy correlation function when cross-correlating two galaxy populations or two different tracers. In this paper, we assess the detectability of these effects in the Euclid spectroscopic galaxy survey. We model the impact of gravitational redshift on the observed redshift of galaxies in the Flagship mock catalogue using a Navarro-Frenk-White profile for the host haloes. We isolate these relativistic effects, largely subdominant in the standard analysis, by splitting the galaxy catalogue into two populations of faint and bright objects and estimating the dipole of their cross-correlation in four redshift bins. In the simulated catalogue, we detect the dipole signal on scales below $30\,h^{-1}{\rm Mpc}$, with detection significances of $4\,\sigma$ and $3\,\sigma$ in the two lowest redshift bins, respectively. At higher redshifts, the detection significance drops below $2\,\sigma$. Overall, we estimate the total detection significance in the Euclid spectroscopic sample to be approximately $6\,\sigma$. We find that on small scales, the major contribution to the signal comes from the nonlinear gravitational potential. Our study on the Flagship mock catalogue shows that this observable can be detected in Euclid Data Release 2 and beyond.
Euclid preparation. Accurate and precise data-driven angular power spectrum covariances
arXiv:2506.09118v1 Announce Type: new
Abstract: We develop techniques for generating accurate and precise internal covariances for measurements of clustering and weak lensing angular power spectra. These methods are designed to produce non-singular and unbiased covariances for Euclid's large anticipated data vector and will be critical for validation against observational systematic effects. We construct jackknife segments that are equal in area to high precision by adapting the binary space partition algorithm to work on arbitrarily shaped regions on the unit sphere. Jackknife estimates of the covariances are internally derived and require no assumptions about cosmology or galaxy population and bias. Our covariance estimation, called DICES (Debiased Internal Covariance Estimation with Shrinkage), first estimates a noisy covariance through conventional delete-1 jackknife resampling. This is followed by linear shrinkage of the empirical correlation matrix towards the Gaussian prediction, rather than linear shrinkage of the covariance matrix. Shrinkage ensures the covariance is non-singular and therefore invertible, critical for the estimation of likelihoods and validation. We then apply a delete-2 jackknife bias correction to the diagonal components of the jackknife covariance that removes the general tendency for jackknife error estimates to be biased high. We validate internally derived covariances, which use the jackknife resampling technique, on synthetic Euclid-like lognormal catalogues. We demonstrate that DICES produces accurate, non-singular covariance estimates, with the relative error improving by $33\%$ for the covariance and $48\%$ for the correlation structure in comparison to jackknife estimates. These estimates can be used for highly accurate regression and inference.
Euclid preparation: The NISP spectroscopy channel, on ground performance and calibration
arXiv:2506.08378v1 Announce Type: new
Abstract: 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 $\text{BG}_\text{E}$ covers the wavelength range $926$--$1366$\,nm at a spectral resolution $R=440$--$900$ for a $0.5''$ diameter source with a dispersion of $1.24$ nm px$^{-1}$. Two red grisms $\text{RG}_\text{E}$ 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.
Constraints on cosmology and baryonic feedback with joint analysis of Dark Energy Survey Year 3 lensing data and ACT DR6 thermal Sunyaev-Zel'dovich effect observations
arXiv:2506.07432v1 Announce Type: new
Abstract: We present a joint analysis of weak gravitational lensing (shear) data obtained from the first three years of observations by the Dark Energy Survey and thermal Sunyaev-Zel'dovich (tSZ) effect measurements from a combination of Atacama Cosmology Telescope (ACT) and Planck data. A combined analysis of shear (which traces the projected mass) with the tSZ effect (which traces the projected gas pressure) can jointly probe both the distribution of matter and the thermodynamic state of the gas, accounting for the correlated effects of baryonic feedback on both observables. We detect the shear$~\times~$tSZ cross-correlation at a 21$\sigma$ significance, the highest to date, after minimizing the bias from cosmic infrared background leakage in the tSZ map. By jointly modeling the small-scale shear auto-correlation and the shear$~\times~$tSZ cross-correlation, we obtain $S_8 = 0.811^{+0.015}_{-0.012}$ and $\Omega_{\rm m} = 0.263^{+0.023}_{-0.030}$, results consistent with primary CMB analyses from Planck and P-ACT. We find evidence for reduced thermal gas pressure in dark matter halos with masses $M < 10^{14} \, M_{\odot}/h$, supporting predictions of enhanced feedback from active galactic nuclei on gas thermodynamics. A comparison of the inferred matter power suppression reveals a $2-4\sigma$ tension with hydrodynamical simulations that implement mild baryonic feedback, as our constraints prefer a stronger suppression. Finally, we investigate biases from cosmic infrared background leakage in the tSZ-shear cross-correlation measurements, employing mitigation techniques to ensure a robust inference. Our code is publicly available on GitHub.