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Wildfire smoke, particularly particulate matter less than 2.5 microns (PM2.5), represents a major source of air pollution and a growing public health problem. PM2.5 is a general term used for any particulate < 2.5 µm; however, a wide variety of particulates with different physical and chemical properties can be formed in this size range. The health impacts of PMs are controlled by their size. Unlike larger particulates, which only enter the respiratory tract, fine PMs (<0.1 µm) can also enter the bloodstream and even pass through the blood-brain barrier. The health risks due to exposure to PM can be different for various PM phases with different physical properties, which is poorly understood. We collected wildfire smoke from more than 10 major wildfires in the Western US using active air samplers that separate particles in different size ranges (>2.5 µm - <0.25 µm). Particles were collected on filters, which are pre-weighted and loaded into the impactor. The filters were weighted and compared with the pre-weight values to calculate the mass of particles collected at each size range. Our results revealed that for all the smoke from varied wildfires, the mass of particles increased with decreasing size, with the majority (more than 50%) being less than 0.25 μm. In addition, the PM2.5 total concentration was recorded using an air quality monitor and compared to the particle size distribution in different smoke samples. The results showed that as the overall concentration of wildfire smoke decreases, the fraction of particles smaller than 0.250 microns increases even more. This suggests that these ultrafine particles not only make up the majority of PM in wildfire smoke but are also more persistent in the atmosphere, even when the total PM concentration is low. Our findings highlight the magnitude of health risks posed by PM and underscore the urgent need for effective solutions to reduce respiratory exposure in affected communities. 

Abstract We present mid-infrared spectroscopic observations of the nucleus of the nearby Seyfert galaxy NGC 7469 taken with the MIRI instrument on the James Webb Space Telescope (JWST) as part of Directors Discretionary Time Early Release Science program 1328. The high-resolution nuclear spectrum contains 19 emission lines covering a wide range of ionization. The high-ionization lines show broad, blueshifted emission reaching velocities up to 1700 km s −1 and FWHM ranging from ∼500 to 1100 km s −1 . The width of the broad emission and the broad-to-narrow line flux ratios correlate with ionization potential. The results suggest a decelerating, stratified, AGN-driven outflow emerging from the nucleus. The estimated mass outflow rate is 1–2 orders of magnitude larger than the current black hole accretion rate needed to power the AGN. Eight pure rotational H 2 emission lines are detected with intrinsic widths ranging from FWHM ∼125 to 330 km s −1 . We estimate a total mass of warm H 2 gas of ∼1.2 × 10 7 M ⊙ in the central 100 pc. The PAH features are extremely weak in the nuclear spectrum, but a 6.2 μ m PAH feature with an equivalent width of ∼0.07 μ m and a flux of 2.7 × 10 −17 W m −2 is detected. The spectrum is steeply rising in the mid-infrared, with a silicate strength of ∼0.02, significantly smaller than seen in most PG QSOs but comparable to other Seyfert 1s. These early MIRI mid-infrared IFU data highlight the power of JWST to probe the multiphase interstellar media surrounding actively accreting supermassive black holes. 

Abstract Nuclear rings are excellent laboratories for studying intense star formation. We present results from a study of nuclear star-forming rings in five nearby normal galaxies from the Star Formation in Radio Survey (SFRS) and four local LIRGs from the Great Observatories All-sky LIRG Survey at sub-kiloparsec resolutions using Very Large Array high-frequency radio continuum observations. We find that nuclear ring star formation (NRSF) contributes 49%–60% of the total star formation of the LIRGs, compared to 7%–40% for the normal galaxies. We characterize a total of 57 individual star-forming regions in these rings, and find that with measured sizes of 10–200 pc, NRSF regions in the LIRGs have star formation rate (SFR) and Σ SFR up to 1.7 M ⊙ yr −1 and 402 M ⊙ yr −1 kpc −2 , respectively, which are about 10 times higher than in NRSF regions in the normal galaxies with similar sizes, and comparable to lensed high- z star-forming regions. At ∼100–300 pc scales, we estimate low contributions (<50%) of thermal free–free emission to total radio continuum emission at 33 GHz in the NRSF regions in the LIRGs, but large variations possibly exist at smaller physical scales. Finally, using archival sub-kiloparsec resolution CO ( J = 1–0) data of nuclear rings in the normal galaxies and NGC 7469 (LIRG), we find a large scatter in gas depletion times at similar molecular gas surface densities, which tentatively points to a multimodal star formation relation on sub-kiloparsec scales. 

Abstract We present results from the James Webb Space Telescope Director’s Discretionary Time Early Release Science program 1328 targeting the nearby, luminous infrared galaxy, VV 114. We use the MIRI and NIRSpec instruments to obtain integral-field spectroscopy of the heavily obscured eastern nucleus (V114E) and surrounding regions. The spatially resolved, high-resolution spectra reveal the physical conditions in the gas and dust over a projected area of 2–3 kpc that includes the two brightest IR sources, the NE and SW cores. Our observations show for the first time spectroscopic evidence that the SW core hosts an active galactic nucleus as evidenced by its very low 6.2μm and 3.3μm polycyclic aromatic hydrocarbon equivalent widths (0.12 and 0.017μm, respectively) and mid- and near-IR colors. Our observations of the NE core show signs of deeply embedded star formation including absorption features due to aliphatic hydrocarbons, large quantities of amorphous silicates, as well as HCN due to cool gas along the line of sight. We detect elevated [Feii]/Pfαconsistent with extended shocks coincident with enhanced emission from warm H₂, far from the IR-bright cores and clumps. We also identify broadening and multiple kinematic components in both H₂and fine structure lines caused by outflows and previously identified tidal features.