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We present a study of new 7.7–11.3 μm data obtained with theJames WebbSpace Telescope Mid-InfraRed Instrument in the starburst galaxy M 82. In particular, we focus on the dependency of the integrated CO(1–0) line intensity on the MIRI-F770W and MIRI-F1130W filter intensities to investigate the correlation between H₂content and the 7.7 and 11.3 μm features from polycyclic aromatic hydrocarbons (PAH) in M 82’s outflows. To perform our analysis, we identify CO clouds using the archival¹²CO(J = 1 − 0) NOEMA moment 0 map within 2 kpc from the center of M 82, with sizes ranging between ∼21 and 270 pc; then, we compute the CO-to-PAH relations for the 306 validated CO clouds. On average, the power-law slopes for the two relations in M 82 are lower than what is seen in local main-sequence spirals. In addition, there is a moderate correlation betweenI_{CO(1 − 0)} − I_7.7 μm/I_11.3 μmfor some of the CO cloud groups analyzed in this work. Our results suggest that the extreme conditions in M 82 translate into CO not tracing the full budget of molecular gas in smaller clouds, perhaps as a consequence of photoionization and/or emission suppression of CO molecules due to hard radiation fields from the central starburst. 

Abstract We report on the internal distribution of star formation efficiency in IRAS 08339+6517 (hereafter IRAS08), using ∼200 pc resolution CO(2 − 1) observations from NOEMA. The molecular gas depletion time changes by 2 orders-of-magnitude from disk-like values in the outer parts to less than 10 8 yr inside the half-light radius. This translates to a star formation efficiency per freefall time that also changes by 2 orders-of-magnitude, reaching 50%–100%, different than local spiral galaxies and the typical assumption of constant, low star formation efficiencies. Our target is a compact, massive disk galaxy that has a star formation rate 10× above the z = 0 main sequence; Toomre Q ≈ 0.5−0.7 and high gas velocity dispersion ( σ mol ≈ 25 km s −1 ). We find that IRAS08 is similar to other rotating, starburst galaxies from the literature in the resolved Σ SFR ∝ Σ mol N relation. By combining resolved literature studies we find that the distance from the main sequence is a strong indicator of the Kennicutt-Schmidt power-law slope, with slopes of N ≈ 1.6 for starbursts from 100 to 10 4 M ⊙ pc −2 . Our target is consistent with a scenario in which violent disk instabilities drive rapid inflows of gas. It has low values of Toomre- Q , and also at all radii, the inflow timescale of the gas is less than the depletion time, which is consistent with the flat metallicity gradients in IRAS08. We consider these results in light of popular star formation theories; in general observations of IRAS08 find the most tension with theories in which star formation efficiency is a constant. Our results argue for the need of high-spatial-resolution CO observations for a larger number of similar targets. 

Abstract Estimating interseismic deformation in subduction fault zones can offer insights into the frequency and magnitude of megathrust earthquakes. Diffusive mass transfer is a significant mechanism of strain during interseismic periods along the plate interface, observed through the pervasive scaly fabrics and mineral veins in tectonic mélanges of ancient accretionary prisms. The dissolution of fluid‐mobile elements (e.g., Si and Large‐Ion Lithophile Elements) along scaly folia and subsequent reprecipitation as veins lead to the enrichment of fluid‐immobile elements (e.g., Ti and High Field Strength Elements) in scaly fabrics. The kinetics of dissolution‐precipitation is temperature‐dependent, suggesting depth‐dependent mass transfer along subduction interfaces. Here, we evaluate the magnitudes of volume strain in a suite of mélange samples that span peak metamorphic temperatures of 130–340°C. Micro‐chemical analysis shows that the depletion of fluid‐mobile elements and enrichment of fluid‐immobile elements in scaly fabrics increases with temperature. Assuming the conservation of Ti, we apply mass balance constraints to calculate the volumetric strain in scaly fabrics. Results indicate average volumetric strain of 28% and 95% in the individual scaly fabrics of the Lower Mugi and Makimine mélanges in Japan, which record temperatures near the updip and downdip isotherms bounding the seismogenic zone, respectively. To determine the total volume strain within an area of interest, we integrate the amount of volume loss along individual microstructures across the network using image analyses, which ranges from 3% to 14% for the mélanges. Our approach demonstrates the potential to fully describe the deformation related to mass transfer by connecting characterization in different scales with geochemical analyses.