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1. Laboratory Study of the Cameron Bands, the First Negative Bands, and Fourth Positive Bands in the Middle Ultraviolet 180–280 nm by Electron Impact Upon CO

   https://doi.org/10.1029/2020JE006602  

   Lee, Rena A. ; Ajello, Joseph M. ; Malone, Charles P. ; Evans, J. Scott ; Veibell, Victoir ; Holsclaw, Gregory M. ; McClintock, William E. ; Hoskins, Alan C. ; Jain, Sonal ; Gérard, Jean‐Claude ; et al ( January 2021 , Journal of Geophysical Research: Planets)

   We have analyzed medium‐resolution (full width at half maximum, FWHM = 1.2 nm), Middle UltraViolet (MUV; 180–280 nm) laboratory emission spectra of carbon monoxide (CO) excited by electron impact at 15, 20, 40, 50, and 100 eV under single‐scattering conditions at 300 K. The MUV emission spectra at 100 eV contain the Cameron Bands (CB) CO(a³Π → X¹Σ⁺), the fourth positive group (4PG) CO(A¹Π → X¹Σ⁺), and the first negative group (1NG) CO⁺(B²Σ⁺→ X²Σ) from direct excitation and cascading‐induced emission of an optically thin CO gas. We have determined vibrational intensities and emission cross sections for these systems, important for modeling UV observations of the atmospheres of Mars and Venus. We have also measured the CB “glow” profile about the electron beam of the long‐lived CO (a³Π) state and determined its average metastable lifetime of 3 ± 1 ms. Optically allowed cascading from a host of triplet states has been found to be the dominant excitation process contributing to the CB emission cross section at 15 eV, most strongly by the d³Δ and a'³Σ⁺electronic states. We normalized the CB emission cross section at 15 eV electron impact energy by multilinear regression (MLR) analysis to the blended 15 eV MUV spectrum over the spectral range of 180–280 nm, based on the 4PG emission cross section at 15 eV that we have previously measured (Ajello et al., 2019,https://doi.org/10.1029/2018ja026308). We find the CB total emission cross section at 15 eV to be 7.7 × 10⁻¹⁷ cm².

    

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2. Laboratory Study of the Cameron Bands and UV Doublet in the Middle Ultraviolet 180–300 nm by Electron Impact upon CO 2 with Application to Mars

   https://doi.org/10.3847/1538-4357/ac88c8  

   Lee, Rena A. ; Ajello, Joseph M. ; Malone, Charles P. ; Evans, J. Scott ; Veibell, Victoir ; Holsclaw, Gregory M. ; McClintock, William E. ; Hoskins, Alan C. ; Jain, Sonal K. ; Gérard, Jean-Claude ; et al ( October 2022 , The Astrophysical Journal)

   We have observed electron impact fluorescence from CO₂to excite the Cameron bands (CBs), CO (a³Π →X¹Σ⁺; 180–280 nm), the first-negative group (1NG) bands, CO⁺(B²Σ⁺→X²Σ⁺; 180–320 nm), the fourth-positive group (4PG) bands, CO (A¹Π →X¹Σ⁺; 111–280 nm), and the UV doublet, CO₂⁺($\tilde{B}{}^2{\mathrm{\Sigma }}_u^{+}\to \tilde{X}{}^2{\mathrm{\Pi }}_g;$288.3 and 289.6 nm) in the ultraviolet (UV). This wavelength range matches the spectral region of past and present spacecraft equipped to observe UV dayglow and aurora emissions from the thermospheres (100–300 km) of Mars and Venus. Our large vacuum system apparatus is able to measure the emission cross sections of the strongest optically forbidden UV transitions found in planetary spectra. Based on our cross-sectional measurements, previous CB emission cross-sectional errors exceed a factor of 3. The UV doublet lifetime is perturbed through$\tilde{B}{}^2{\mathrm{\Sigma }}_u^{+}-\tilde{A}{}^2{\mathrm{\Pi }}_u$spin–orbit coupling. Forward modeling codes of the Mars dayglow have not been accurate in the mid-UV due to systematic errors in these two emission cross sections. We furnish absolute emission cross sections for several band systems over electron energies 20–100 eV for CO₂. We present a CB lifetime, which together with emission cross sections, furnish a set of fundamental physical constants for electron transport codes such as AURIC (Atmospheric Ultraviolet Radiance Integrated Code). AURIC and Trans-Mars are used in the analysis of UV spectra from the Martian dayglow and aurora.

    

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3. Jansky Very Large Array Detections of CO(1–0) Emission in H i-absorption-selected Galaxies at z ≳ 2

   https://doi.org/10.3847/2041-8213/ac7bdd  

   Kaur, B. ; Kanekar, N. ; Rafelski, M. ; Neeleman, M. ; Prochaska, J. X. ; Revalski, M. ( July 2022 , The Astrophysical Journal Letters)

   We report a Karl G. Jansky Very Large Array search for redshifted CO(1–0) emission from three Hi-absorption-selected galaxies atz≈ 2, identified earlier in their CO(3–2) or CO(4–3) emission. We detect CO(1–0) emission from DLA B1228-113 atz≈ 2.1933 and DLA J0918+1636 atz≈ 2.5848; these are the first detections of CO(1–0) emission in high-zHi-selected galaxies. We obtain high molecular gas masses,M_mol≈ 10¹¹× (α_CO/4.36)M_⊙, for the two objects with CO(1–0) detections, which are a factor of ≈1.5–2 lower than earlier estimates. We determine the excitation of the mid-JCO rotational levels relative to theJ= 1 level,r_J1, in Hi-selected galaxies for the first time, obtainingr₃₁= 1.00 ± 0.20 andr₄₁= 1.03 ± 0.23 for DLA J0918+1636, andr₃₁= 0.86 ± 0.21 for DLA B1228-113. These values are consistent with thermal excitation of theJ= 3 andJ= 4 levels. The excitation of theJ= 3 level in the Hi-selected galaxies is similar to that seen in massive main-sequence and submillimeter galaxies atz≳2, but higher than that in main-sequence galaxies atz≈ 1.5; the higher excitation of the galaxies atz≳ 2 is likely to be due to their higher star formation rate (SFR) surface density. We use Hubble Space Telescope Wide Field Camera 3 imaging to detect the rest-frame near-ultraviolet (NUV) emission of DLA B1228-113, obtaining an NUV SFR of 4.44 ± 0.47M_⊙yr⁻¹, significantly lower than that obtained from the total infrared luminosity, indicating significant dust extinction in thez≈ 2.1933 galaxy.

    

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4. A Massive, Dusty, Hi Absorption–Selected Galaxy at z ≈ 2.46 Identified in a CO Emission Survey

   https://doi.org/10.3847/1538-4357/ac7b2c  

   Kaur, B. ; Kanekar, N. ; Revalski, M. ; Rafelski, M. ; Neeleman, M. ; Prochaska, J. X. ; Walter, F. ( July 2022 , The Astrophysical Journal)

   We report a NOrthern Extended Millimeter Array (NOEMA) and Atacama Large Millimeter/submillimeter Array search for redshifted CO emission from the galaxies associated with seven high-metallicity ([M/H] ≥ −1.03) damped Lyαabsorbers (DLAs) atz≈ 1.64–2.51. Our observations yielded one new detection of CO(3–2) emission from a galaxy atz= 2.4604 using NOEMA, associated with thez= 2.4628 DLA toward QSO B0201+365. Including previous searches, our search results in detection rates of CO emission of$\approx {56}_{-24}^{+38}$% and$\approx {11}_{-9}^{+26}$%, respectively, in the fields of DLAs with [M/H] > −0.3 and [M/H] < −0.3. Further, the Hi–selected galaxies associated with five DLAs with [M/H] > −0.3 all have high molecular gas masses, ≳5 × 10¹⁰M_⊙. This indicates that the highest-metallicity DLAs atz≈ 2 are associated with the most massive galaxies. The newly identifiedz≈ 2.4604 Hi–selected galaxy, DLA0201+365g, has an impact parameter of ≈7 kpc to the QSO sightline, and an implied molecular gas mass of (5.04 ± 0.78) × 10¹⁰× (α_CO/4.36) × (r₃₁/0.55)M_⊙. Archival Hubble Space Telescope Wide Field and Planetary Camera 2 imaging covering the rest-frame near-ultraviolet (NUV) and far-ultraviolet (FUV) emission from this galaxy yield nondetections of rest-frame NUV and FUV emission, and a 5σupper limit of 2.3M_⊙yr⁻¹on the unobscured star formation rate (SFR). The low NUV-based SFR estimate, despite the very high molecular gas mass, indicates that DLA0201+365g either is a very dusty galaxy, or has a molecular gas depletion time that is around 2 orders of magnitude larger than that of star-forming galaxies at similar redshifts.

    

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5. [C ii] Spectral Mapping of the Galactic Wind and Starbursting Disk of M82 with SOFIA

   https://doi.org/10.3847/1538-4357/acff6e  

   Levy, Rebecca C. ; Bolatto, Alberto D. ; Tarantino, Elizabeth ; Leroy, Adam K. ; Armus, Lee ; Emig, Kimberly L. ; Herrera-Camus, Rodrigo ; Marrone, Daniel P. ; Mills, Elisabeth ; Ricken, Oliver ; et al ( November 2023 , The Astrophysical Journal)

   M82 is an archetypal starburst galaxy in the local Universe. The central burst of star formation, thought to be triggered by M82's interaction with other members in the M81 group, is driving a multiphase galaxy-scale wind away from the plane of the disk that has been studied across the electromagnetic spectrum. Here, we present new velocity-resolved observations of the [Cii] 158μm line in the central disk and the southern outflow of M82 using the upGREAT instrument on board SOFIA. We also report the first detections of velocity-resolved (ΔV= 10 km s⁻¹) [Cii] emission in the outflow of M82 at projected distances of ≈1–2 kpc south of the galaxy center. We compare the [Cii] line profiles to observations of CO and Hiand find that likely the majority (>55%) of the [Cii] emission in the outflow is associated with the neutral atomic medium. We find that the fraction of [Cii] actually outflowing from M82 is small compared to the bulk gas outside the midplane (which may be in a halo or tidal streamers), which has important implications for observations of [Cii] outflows at higher redshift. Finally, by comparing the observed ratio of the [Cii] and CO intensities to models of photodissociation regions, we estimate that the far-ultraviolet (FUV) radiation field in the disk is ∼10^3.5G₀, in agreement with previous estimates. In the outflow, however, the FUV radiation field is 2–3 orders of magnitudes lower, which may explain the high fraction of [Cii] arising from the neutral medium in the wind.

    

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