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1. KODIAQ-Z: Metals and Baryons in the Cool Intergalactic and Circumgalactic Gas at 2.2 ≲ z ≲ 3.6

   https://doi.org/10.3847/1538-4357/ac7400  

   Lehner, Nicolas; Kopenhafer, Claire; O’Meara, John M.; Howk, J. Christopher; Fumagalli, Michele; Prochaska, J. Xavier; Acharyya, Ayan; O’Shea, Brian W.; Peeples, Molly S.; Tumlinson, Jason; et al (September 2022, The Astrophysical Journal)

   Abstract We present the KODIAQ-Z survey aimed to characterize the cool, photoionized gas at 2.2 ≲z≲ 3.6 in 202 Hi-selected absorbers with 14.6 ≤ $\log N_{\mathrm{H}\mathrm{I}}$< 20 that probe the interface between galaxies and the intergalactic medium (IGM). We find that gas with $14.6\le \log N_{\mathrm{H}\mathrm{I}}<20$at 2.2 ≲z≲ 3.6 can be metal-rich (−1.6 ≲ [X/H] ≲ − 0.2) as seen in damped Lyαabsorbers (DLAs); it can also be very metal-poor ([X/H] < − 2.4) or even pristine ([X/H] < − 3.8), which is not observed in DLAs but is common in the IGM. For $16<\log N_{\mathrm{H}\mathrm{I}}<20$absorbers, the frequency of pristine absorbers is about 1%–10%, while for $14.6\le \log N_{\mathrm{H}\mathrm{I}}\le 16$absorbers it is 10%–20%, similar to the diffuse IGM. Supersolar gas is extremely rare (<1%) at these redshifts. The factor of several thousand spread from the lowest to highest metallicities and large metallicity variations (a factor of a few to >100) between absorbers separated by less than Δv< 500 km s⁻¹imply that the metals are poorly mixed in $14.6\le \log N_{\mathrm{H}\mathrm{I}}<20$gas. We show that these photoionized absorbers contribute to about 14% of the cosmic baryons and 45% of the cosmic metals at 2.2 ≲z≲ 3.6. We find that the mean metallicity increases withN_Hi, consistent with what is found inz< 1 gas. The metallicity of gas in this column density regime has increased by a factor ∼8 from 2.2 ≲z≲ 3.6 toz< 1, but the contribution of the $14.6\le \log N_{\mathrm{H}\mathrm{I}}<19$absorbers to the total metal budget of the universe atz< 1 is a quarter of that at 2.2 ≲z≲ 3.6. We show that FOGGIE cosmological zoom-in simulations have a similar evolution of [X/H] withN_Hi, which is not observed in lower-resolution simulations. In these simulations, very metal-poor absorbers with [X/H] < − 2.4 atz∼ 2–3 are tracers of inflows, while higher-metallicity absorbers are a mixture of inflows and outflows. 

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2. Multi-scale Physical Properties of NGC 6334 as Revealed by Local Relative Orientations between Magnetic Fields, Density Gradients, Velocity Gradients, and Gravity

   https://doi.org/10.3847/1538-4357/acb540  

   Liu, Junhao; Zhang, Qizhou; Koch, Patrick M.; Liu, Hauyu Baobab; Li, Zhi-Yun; Li, Shanghuo; Girart, Josep Miquel; Chen, Huei-Ru Vivien; Ching, Tao-Chung; Ho, Paul T.; et al (March 2023, The Astrophysical Journal)

   Abstract We present ALMA dust polarization and molecular line observations toward four clumps (I(N), I, IV, and V) in the massive star-forming region NGC 6334. In conjunction with large-scale dust polarization and molecular line data from JCMT, Planck, and NANTEN2, we make a synergistic analysis of relative orientations between magnetic fields (θ_B), column density gradients (θ_NG), local gravity (θ_LG), and velocity gradients (θ_VG) to investigate the multi-scale (from ∼30 to 0.003 pc) physical properties in NGC 6334. We find that the relative orientation betweenθ_Bandθ_NGchanges from statistically more perpendicular to parallel as column density ( $N_{{\mathrm{H}}_2}$) increases, which is a signature of trans-to-sub-Alfvénic turbulence at complex/cloud scales as revealed by previous numerical studies. Becauseθ_NGandθ_LGare preferentially aligned within the NGC 6334 cloud, we suggest that the more parallel alignment betweenθ_Bandθ_NGat higher $N_{{\mathrm{H}}_2}$is because the magnetic field line is dragged by gravity. At even higher $N_{{\mathrm{H}}_2}$, the angle betweenθ_Bandθ_NGorθ_LGtransits back to having no preferred orientation, or statistically slightly more perpendicular, suggesting that the magnetic field structure is impacted by star formation activities. A statistically more perpendicular alignment is found betweenθ_Bandθ_VGthroughout our studied $N_{{\mathrm{H}}_2}$range, which indicates a trans-to-sub-Alfvénic state at small scales as well, and this signifies that magnetic field has an important role in the star formation process in NGC 6334. The normalized mass-to-flux ratio derived from the polarization-intensity gradient (KTH) method increases with $N_{{\mathrm{H}}_2}$, but the KTH method may fail at high $N_{{\mathrm{H}}_2}$due to the impact of star formation feedback. 

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3. The EDGE-CALIFA Survey: Spatially Resolved ¹³ CO(1–0) Observations and Variations in ¹² CO(1–0)/ ¹³ CO(1–0) in Nearby Galaxies on Kiloparsec Scales

   https://doi.org/10.3847/1538-4365/acd840  

   Cao, Yixian; Wong, Tony; Bolatto, Alberto D; Leroy, Adam K; Rosolowsky, Erik; Utomo, Dyas; Sánchez, Sebastián F; Barrera-Ballesteros, Jorge K; Levy, Rebecca C; Colombo, Dario; et al (August 2023, The Astrophysical Journal Supplement Series)

   Abstract We present¹³CO(J= 1 → 0) observations for the EDGE-CALIFA survey, which is a mapping survey of 126 nearby galaxies at a typical spatial resolution of 1.5 kpc. Using detected¹²CO emission as a prior, we detect¹³CO in 41 galaxies via integrated line flux over the entire galaxy and in 30 galaxies via integrated line intensity in resolved synthesized beams. Incorporating our CO observations and optical IFU spectroscopy, we perform a systematic comparison between the line ratio ${\mathit{}}_{12/13}\equiv I{[}^{12}\mathrm{CO}(J=1\to 0)\left]/I{[}^{13}\mathrm{CO}\right(J=1\to 0\left)\right]$and the properties of the stars and ionized gas. Higher ${\mathit{}}_{12/13}$values are found in interacting galaxies compared to those in noninteracting galaxies. The global ${\mathit{}}_{12/13}$slightly increases with infrared colorF₆₀/F₁₀₀but appears insensitive to other host-galaxy properties such as morphology, stellar mass, or galaxy size. We also present azimuthally averaged ${\mathit{}}_{12/13}$profiles for our sample up to a galactocentric radius of 0.4r₂₅(∼6 kpc), taking into account the¹³CO nondetections by spectral stacking. The radial profiles of ${\mathit{}}_{12/13}$are quite flat across our sample. Within galactocentric distances of 0.2r₂₅, the azimuthally averaged ${\mathit{}}_{12/13}$increases with the star formation rate. However, Spearman rank correlation tests show the azimuthally averaged ${\mathit{}}_{12/13}$does not strongly correlate with any other gas or stellar properties in general, especially beyond 0.2r₂₅from the galaxy centers. Our findings suggest that in the complex environments in galaxy disks, ${\mathit{}}_{12/13}$is not a sensitive tracer for ISM properties. Dynamical disturbances, like galaxy interactions or the presence of a bar, also have an overall impact on ${\mathit{}}_{12/13}$, which further complicates the interpretations of ${\mathit{}}_{12/13}$variations. 

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4. Stellar Metallicities and Gradients in the Isolated, Quenched Low-mass Galaxy Tucana

   https://doi.org/10.3847/1538-4357/ad25ed  

   Fu, Sal Wanying; Weisz, Daniel R.; Starkenburg, Else; Martin, Nicolas; Mercado, Francisco J.; Savino, Alessandro; Boylan-Kolchin, Michael; Côté, Patrick; Dolphin, Andrew E.; Longeard, Nicolas; et al (April 2024, The Astrophysical Journal)

   Abstract We measure the metallicities of 374 red giant branch (RGB) stars in the isolated, quenched dwarf galaxy Tucana using Hubble Space Telescope narrowband (F395N) calcium H and K imaging. Our sample is a factor of ∼7 larger than what is available from previous studies. Our main findings are as follows. (i) A global metallicity distribution function (MDF) with $〈\mathrm{[Fe/H]}〉=-{1.55}_{-0.04}^{+0.04}$and ${\sigma }_{\mathrm{[Fe/H]}}={0.54}_{-0.03}^{+0.03}$. (ii) A metallicity gradient of −0.54 ± 0.07 dex $R_e^{-1}$(−2.1 ± 0.3 dex kpc⁻¹) over the extent of our imaging (∼2.5R_e), which is steeper than literature measurements. Our finding is consistent with predicted gradients from the publicly available FIRE-2 simulations, in which bursty star formation creates stellar population gradients and dark matter cores. (iii) Tucana’s bifurcated RGB has distinct metallicities: a blue RGB with $〈\mathrm{[Fe/H]}〉=-{1.78}_{-0.06}^{+0.06}$and ${\sigma }_{\mathrm{[Fe/H]}}={0.44}_{-0.06}^{+0.07}$and a red RGB with $〈\mathrm{[Fe/H]}〉=-{1.08}_{-0.07}^{+0.07}$and ${\sigma }_{\mathrm{[Fe/H]}}={0.42}_{-0.06}^{+0.06}$. (iv) At fixed stellar mass, Tucana is more metal-rich than Milky Way satellites by ∼0.4 dex, but its blue RGB is chemically comparable to the satellites. Tucana’s MDF appears consistent with star-forming isolated dwarfs, though MDFs of the latter are not as well populated. (v) About 2% of Tucana’s stars have [Fe/H] < −3% and 20% have [Fe/H] > −1. We provide a catalog for community spectroscopic follow-up. 

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5. Keck Planet Imager and Characterizer Emission Spectroscopy of WASP-33b

   https://doi.org/10.3847/1538-3881/acda91  

   Finnerty, Luke; Schofield, Tobias; Sappey, Ben; Xuan, Jerry W.; Ruffio, Jean-Baptiste; Wang, Jason J.; Delorme, Jacques-Robert; Blake, Geoffrey A.; Buzard, Cam; Fitzgerald, Michael P.; et al (June 2023, The Astronomical Journal)

   Abstract We present Keck Planet Imager and Characterizer (KPIC) high-resolution (R∼35,000)K-band thermal emission spectroscopy of the ultrahot Jupiter WASP-33b. The use of KPIC’s single-mode fibers greatly improves both blaze and line-spread stabilities relative to slit spectrographs, enhancing the cross-correlation detection strength. We retrieve the dayside emission spectrum with a nested-sampling pipeline, which fits for orbital parameters, the atmospheric pressure–temperature profile, and the molecular abundances. We strongly detect the thermally inverted dayside and measure mass-mixing ratios for CO ( ${\mathrm{logCO}}_{\mathrm{MMR}}=-{1.1}_{-0.6}^{+0.4}$), H₂O ( ${\mathrm{logH}}_2{\mathrm{O}}_{\mathrm{MMR}}=-{4.1}_{-0.9}^{+0.7}$), and OH ( ${\mathrm{logOH}}_{\mathrm{MMR}}=-{2.1}_{-1.1}^{+0.5}$), suggesting near-complete dayside photodissociation of H₂O. The retrieved abundances suggest a carbon- and possibly metal-enriched atmosphere, with a gas-phase C/O ratio of ${0.8}_{-0.2}^{+0.1}$, consistent with the accretion of high-metallicity gas near the CO₂snow line and post-disk migration or with accretion between the soot and H₂O snow lines. We also find tentative evidence for¹²CO/¹³CO ∼ 50, consistent with values expected in protoplanetary disks, as well as tentative evidence for a metal-enriched atmosphere (2–15 × solar). These observations demonstrate KPIC’s ability to characterize close-in planets and the utility of KPIC’s improved instrumental stability for cross-correlation techniques. 

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