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Abstract Polarized Fourier transform infrared (FTIR) microspectroscopy of the OH-stretching region of hydroxylapatite-chlorapatite solid solutions presents novel problems for the assignment of peaks to specific OH-Cl pairs. Crystal structure refinements of Hughes et al. (2016) identified new positions for column anions in synthetic mixed Cl-OH apatites, with three different column anion arrangements depending on composition. These structural refinements, combined with bond-valence calculations, allow for interpretation of the OH-stretching region. A peak at 3574 cm–1 is identified as that from end-member hydroxylapatite. A second major peak at 3548 cm–1 is only found in mixed chlorapatite-hydroxylapatite solid solutions, as is a third peak at 3592 cm–1. Both represent perturbations of the OH-stretching vibration as compared to hydroxylapatite, to lower and higher frequency, respectively. Both of the new peaks are the result of a Clb-OH sequence, with adjacent anions in crystallographically similar positions, both above or both below adjacent mirror planes. One configuration has the hydrogen atom pointed toward the chlorine atom. The second has the hydrogen of the OH group pointed away from the chlorine atom. Both configurations present novel problems. The shift to lower wavenumber at 3548 cm–1 is characteristic of hydrogen bonding in fluorapatite-hydroxylapatite mixtures, yet the distance between O(H) and Clb is too great to allow it. The shift of OH-stretching vibrations to lower wavenumber is produced through changes in polarization of intervening Cl-Ca2′ (or Ca2) and Ca2(′)-O3 bonds, which are affected by the presence of the large chlorine atom. Lowering the OH-stretching vibration mimics the expected effect of chlorine on a neighboring OH group in the apatite c-axis column, though without hydrogen bonding. The shift to higher wavenumbers, i.e., higher frequency at 3592 cm–1, is the opposite of that expected for hydrogen bonding between column anions in the apatite mineral group. It is ascribed to the interaction between an adjacent Clb and the oxygen end of an adjacent OH dipole. This pairing places an oxygen and a chlorine atom in close proximity. Possible means of accommodation are discussed. A ubiquitous peak at 3498 cm–1 represents hydrogen bonding between an OH and the OHa site, with an interoxygen distance of about 2.9 Å. Published modeling supports the hypothesis that the OHa site is occupied by an O rather than an OH. However, no clear counterpart to this pairing is observed in crystal structure refinements for specimens lacking OHa, although the infrared absorbance is present. The existence of oxyapatite is inferred from studies of plasma-sprayed biomaterials, but the crystal-lographic details of the substitution have remained elusive. A minor shoulder at 3517 cm–1 does not have a clear counterpart in the structural refinements. Sequences of three columnar anions (e.g., OH-Cl-OH or Cl-OH-OH) can be ruled out, but an unequivocal assignment awaits further research. 

Abstract Fluoride is one of the most consumed pharmaceuticals in the world, and its facility in preventing dental caries is recognized as one of the top 10 public health achievements of the 20th century. Although hydroxylapatite is often used as an analog of dental enamel, the details of the substitution of F for OH in the apatite anion column are not well known. Using new synthesis techniques, this study extends the structure work on P63/m apatites along the middle portion of the F-OH apatite join to compositions near the composition of fluoridated human teeth. The first F substituent in hydroxylapatite, near fluoridated dental enamel compositions, is dramatically underbonded by the surrounding Ca2 atoms (0.72 vu) in a hydroxylapatite matrix. However, the hydroxyl hydrogen is able to contribute 0.20 or 0.10 vu in hydrogen bonding, depending on whether the substitution creates a reversal site in the anion column; this hydrogen bonding alleviates the bonding requirements of the substituent F. As F concentrations increase along the join, the average hydroxyl contributes increasing amounts of hydrogen bonding to the F column anions; to mitigate the loss of its hydrogen bonding, the hydroxyl oxygen migrates toward the adjacent mirror plane that contains the bonded Ca2 atoms, and the triangle of bonded Ca2 ions concomitantly contracts. These two mechanisms increase bonding to the column hydroxyl oxygen from the adjoining Ca2 atoms to balance the loss of hydrogen bonding that stabilizes the substituent F column anion and the increasing concentration of underbonded F. 

We present Weak Gravitational Lensing measurements of a sample of 157 clusters within the Kilo Degree Survey (KiDS), detected with a > 5σthermal Sunyaev-Zel’dovich (SZ) signal by the Atacama Cosmology Telescope (ACT). Using a halo-model approach, we constrained the average total cluster mass,M_WL, accounting for the ACT cluster selection function of the full sample. We find that the SZ cluster mass estimateM_SZ, which was calibrated using X-ray observations, is biased withM_SZ/M_WL = (1 − b_SZ) = 0.65 ± 0.05. Separating the sample into six mass bins, we find no evidence of a strong mass dependency for the mass bias, (1 − b_SZ). Adopting this ACT-KiDS SZ mass calibration would bring thePlanckSZ cluster count into agreement with the counts expected from thePlanckcosmic microwave background ΛCDM cosmological model, although it should be noted that the cluster sample considered in this work has a lower average massM_SZ, uncor = 3.64 × 10¹⁴ M_⊙compared to thePlanckcluster sample which has an average mass in the rangeM_SZ, uncor = (5.5 − 8.5)×10¹⁴ M_⊙, depending on the sub-sample used. 

Abstract We present power spectra of the cosmic microwave background (CMB) anisotropy in temperature and polarization, measured from the Data Release 6 maps made from Atacama Cosmology Telescope (ACT) data. These cover 19,000 deg²of sky in bands centered at 98, 150 and 220 GHz, with white noise levels three times lower thanPlanckin polarization. We find that the ACT angular power spectra estimated over 10,000 deg², and measured to arcminute scales in TT, TE and EE, are well fit by the sum of CMB and foregrounds, where the CMB spectra are described by the ΛCDM model. Combining ACT with larger-scalePlanckdata, the joint P-ACT dataset provides tight limits on the ingredients, expansion rate, and initial conditions of the universe. We find similar constraining power, and consistent results, from either thePlanckpower spectra or from ACT combined withWMAPdata, as well as from either temperature or polarization in the joint P-ACT dataset. When combined with CMB lensing from ACT andPlanck, and baryon acoustic oscillation data from the Dark Energy Spectroscopic Instrument (DESI DR1), we measure a baryon density of Ω_bh²= 0.0226 ± 0.0001, a cold dark matter density of Ω_ch²= 0.118 ± 0.001, a Hubble constant ofH₀= 68.22 ± 0.36 km/s/Mpc, a spectral index ofn_s= 0.974 ± 0.003, and an amplitude of density fluctuations ofσ₈= 0.813 ± 0.005. Including the DESI DR2 data tightens the Hubble constant toH₀= 68.43 ± 0.27 km/s/Mpc; ΛCDM parameters agree between the P-ACT and DESI DR2 data at the 1.6σlevel. We find no evidence for excess lensing in the power spectrum, and no departure from spatial flatness. The contribution from Sunyaev-Zel'dovich (SZ) anisotropy is detected at high significance; we find evidence for a tilt with suppressed small-scale power compared to our baseline SZ template spectrum, consistent with hydrodynamical simulations with feedback. 

Abstract We present Atacama Cosmology Telescope (ACT) Data Release 6 (DR6) maps of the Cosmic Microwave Background temperature and polarization anisotropy at arcminute resolution over three frequency bands centered on 98, 150 and 220 GHz. The maps are based on data collected with the AdvancedACT camera over the period 2017–2022 and cover 19,000 square degrees with a median combined depth of 10 μK arcmin. We describe the instrument, mapmaking and map properties and illustrate them with a number of figures and tables. The ACT DR6 maps and derived products are available on LAMBDA athttps://lambda.gsfc.nasa.gov/product/act/actadv_prod_table.html. We also provide an interactive web atlas athttps://phy-act1.princeton.edu/public/snaess/actpol/dr6/atlasand HiPS data sets in Aladin (e.g.https://alasky.cds.unistra.fr/ACT/DR4DR6/color_CMB). 

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, ΛCDM, 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 thePlanckmission. To break geometric degeneracies, we include ACT andPlanckCMB lensing data and baryon acoustic oscillation data from DESI Year-1. To test the dependence of our results on non-ACT data, we also explore combinations replacingPlanckwithWMAPand DESI with BOSS, 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 indexdn_s/dlnk= 0.0062 ± 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_eff= 2.86 ± 0.13, which combined with astrophysical measurements of primordial helium and deuterium abundances becomesN_eff= 2.89 ± 0.11), for non-zero neutrino masses (∑m_ν< 0.089 eV at 95% CL), or for neutrino self-interactions. We also find no evidence for self-interacting dark radiation (N_idr< 0.134), or for early-universe variation of fundamental constants, including the fine-structure constant (α_EM/α_EM,0= 1.0043 ± 0.0017) and the electron mass (m_e/m_e,0= 1.0063 ± 0.0056). Our data are consistent with standard big bang nucleosynthesis (we findY_p= 0.2312 ± 0.0092), theCOBE/FIRAS-inferred CMB temperature (we findT_CMB= 2.698 ± 0.016 K), a dark matter component that is collisionless and with only a small fraction allowed as axion-like particles, a cosmological constant (w= -0.986 ± 0.025), and the late-time growth rate predicted by general relativity (γ= 0.663 ± 0.052). We find no statistically significant preference for a departure from the baseline ΛCDM model. In fits to models invoking early dark energy, primordial magnetic fields, or an arbitrary modified recombination history, we findH₀= 69.9^+0.8_-1.5, 69.1 ± 0.5, or 69.6 ± 1.0 km/s/Mpc, respectively; using BOSS instead of DESI BAO data reduces the central values of these constraints by 1–1.5 km/s/Mpc while only slightly increasing the error bars. 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 over ΛCDM by our data. 

Abstract Nebular-phase observations of peculiar Type Ia supernovae (SNe Ia) provide important constraints on progenitor scenarios and explosion dynamics for both these rare SNe and the more common, cosmologically useful SNe Ia. We present observations from an extensive ground- and space-based follow-up campaign to characterize SN 2022pul, a super-Chandrasekhar mass SN Ia (alternatively “03fg-like” SN), from before peak brightness to well into the nebular phase across optical to mid-infrared (MIR) wavelengths. The early rise of the light curve is atypical, exhibiting two distinct components, consistent with SN Ia ejecta interacting with dense carbon–oxygen (C/O)-rich circumstellar material (CSM). In the optical, SN 2022pul is most similar to SN 2012dn, having a low estimated peak luminosity (M_B= −18.9 mag) and high photospheric velocity relative to other 03fg-like SNe. In the nebular phase, SN 2022pul adds to the increasing diversity of the 03fg-like subclass. From 168 to 336 days after peakB-band brightness, SN 2022pul exhibits asymmetric and narrow emission from [Oi]λλ6300, 6364 (FWHM ≈ 2000 km s⁻¹), strong, broad emission from [Caii]λλ7291, 7323 (FWHM ≈ 7300 km s⁻¹), and a rapid Feiiito Feiiionization change. Finally, we present the first ever optical-to-MIR nebular spectrum of an 03fg-like SN Ia using data from JWST. In the MIR, strong lines of neon and argon, weak emission from stable nickel, and strong thermal dust emission (withT≈ 500 K), combined with prominent [Oi] in the optical, suggest that SN 2022pul was produced by a white dwarf merger within C/O-rich CSM. 

ABSTRACT Compact sources can cause scatter in the scaling relationships between the amplitude of the thermal Sunyaev–Zel’dovich Effect (tSZE) in galaxy clusters and cluster mass. Estimates of the importance of this scatter vary – largely due to limited data on sources in clusters at the frequencies at which tSZE cluster surveys operate. In this paper, we present 90 GHz compact source measurements from a sample of 30 clusters observed using the MUSTANG2 instrument on the Green Bank Telescope. We present simulations of how a source’s flux density, spectral index, and angular separation from the cluster’s centre affect the measured tSZE in clusters detected by the Atacama Cosmology Telescope (ACT). By comparing the MUSTANG2 measurements with these simulations we calibrate an empirical relationship between 1.4 GHz flux densities from radio surveys and source contamination in ACT tSZE measurements. We find 3 per cent of the ACT clusters have more than a 20 per cent decrease in Compton-y but another 3 per cent have a 10 per cent increase in the Compton-y due to the matched filters used to find clusters. As sources affect the measured tSZE signal and hence the likelihood that a cluster will be detected, testing the level of source contamination in the tSZE signal using a tSZE-selected catalogue is inherently biased. We confirm this by comparing the ACT tSZE catalogue with optically and X-ray-selected cluster catalogues. There is a strong case for a large, high-resolution survey of clusters to better characterize their source population.