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1. The metastable Q ³ Δ ₂ state of ThO: a new resource for the ACME electron EDM search

   https://doi.org/10.1088/1367-2630/ab6a3a  

   Wu, X.; Han, Z.; Chow, J.; Ang, D. G.; Meisenhelder, C.; Panda, C. D.; West, E. P.; Gabrielse, G.; Doyle, J. M.; DeMille, D. (February 2020, New Journal of Physics)

   Abstract The best upper limit for the electron electric dipole moment was recently set by the ACME collaboration. This experiment measures an electron spin-precession in a cold beam of ThO molecules in their metastable $H{(}^3{\mathrm{\Delta }}_1)$state. Improvement in the statistical and systematic uncertainties is possible with more efficient use of molecules from the source and better magnetometry in the experiment, respectively. Here, we report measurements of several relevant properties of the long-lived $Q{(}^3{\mathrm{\Delta }}_2)$state of ThO, and show that this state is a very useful resource for both these purposes. TheQstate lifetime is long enough that its decay during the time of flight in the ACME beam experiment is negligible. The large electric dipole moment measured for theQstate, giving rise to a large linear Stark shift, is ideal for an electrostatic lens that increases the fraction of molecules detected downstream. The measured magnetic moment of theQstate is also large enough to be used as a sensitive co-magnetometer in ACME. Finally, we show that theQstate has a large transition dipole moment to the $C{(}^1{\mathrm{\Pi }}_1)$state, which allows for efficient population transfer between the ground state $X{(}^1{\mathrm{\Sigma }}^{+})$and theQstate via $X-C-Q$Stimulated Raman Adiabatic Passage (STIRAP). We demonstrate 90 % STIRAP transfer efficiency. In the course of these measurements, we also determine the magnetic moment ofCstate, the $X\to C$transition dipole moment, and branching ratios of decays from theCstate. 

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2. The CO-to-H ₂ Conversion Factor in the Barred Spiral Galaxy M83

   https://doi.org/10.3847/1538-4357/ad40a0  

   Lee, Amanda_M; Koda, Jin; Hirota, Akihiko; Egusa, Fumi; Heyer, Mark (June 2024, The Astrophysical Journal)

   Abstract We analyze the CO-to-H₂conversion factor (α_CO) in the nearby barred spiral galaxy M83. We present new Hiobservations from the VLA and single-dish GBT in the disk of the galaxy, and combine them with maps of CO(1-0) integrated intensity and dust surface density from the literature.α_COand the gas-to-dust ratio (δ_GDR) are simultaneously derived in annuli of 2 kpc width fromR= 1–7 kpc. We find thatα_COandδ_GDRboth increase radially, by a factor of ∼2–3 from the center to the outskirts of the disk. The luminosity-weighted averages over the disk areα_CO= 3.14 (2.06, 4.96) $M_{\odot }{\mathrm{pc}}^{-2}{\left[\mathrm{K}\mathrm{km}{\mathrm{s}}^{-1}\right]}^{-1}$andδ_GDR= 137 (111, 182) at the 68% (1σ) confidence level. These are consistent with theα_COandδ_GDRvalues measured in the Milky Way. In addition to possible variations ofα_COdue to the radial metallicity gradient, we test the possibility of variations inα_COdue to changes in the underlying cloud populations, as a function of galactic radius. Using a truncated power-law molecular cloud CO luminosity function and an empirical power-law relation for cloud mass and luminosity, we show that the changes in the underlying cloud population may account for a factor of ∼1.5–2.0 radial change inα_CO. 

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3. Analytical Model of Disk Evaporation and State Transitions in Accreting Black Holes

   https://doi.org/10.3847/1538-4357/ac6d5c  

   Cho 조, Hyerin 혜린; Narayan, Ramesh (June 2022, The Astrophysical Journal)

   Abstract State transitions in black hole X-ray binaries are likely caused by gas evaporation from a thin accretion disk into a hot corona. We present a height-integrated version of this process, which is suitable for analytical and numerical studies. With radiusrscaled to Schwarzschild units and coronal mass accretion rate ${\dot{m}}_c$to Eddington units, the results of the model are independent of black hole mass. State transitions should thus be similar in X-ray binaries and an active galactic nucleus. The corona solution consists of two power-law segments separated at a break radiusr_b∼ 10³(α/0.3)⁻², whereαis the viscosity parameter. Gas evaporates from the disk to the corona forr>r_b, and condenses back forr<r_b. Atr_b, ${\dot{m}}_c$reaches its maximum, ${\dot{m}}_{c,\max }\approx 0.02{\left(\alpha /0.3\right)}^3$. If atr≫r_bthe thin disk accretes with ${\dot{m}}_d<{\dot{m}}_{c,\max }$, then the disk evaporates fully before reachingr_b, giving the hard state. Otherwise, the disk survives at all radii, giving the thermal state. While the basic model considers only bremsstrahlung cooling and viscous heating, we also discuss a more realistic model that includes Compton cooling and direct coronal heating by energy transport from the disk. Solutions are again independent of black hole mass, andr_bremains unchanged. This model predicts strong coronal winds forr>r_b, and aT∼ 5 × 10⁸K Compton-cooled corona forr<r_b. Two-temperature effects are ignored, but may be important at small radii. 

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4. 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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5. Extreme Scale Height Variations and Nozzle Shocks in Warped Disks

   https://doi.org/10.3847/1538-4357/ad9a85  

   Kaaz, Nicholas; Lithwick, Yoram; Liska, Matthew; Tchekhovskoy, Alexander (January 2025, The Astrophysical Journal)

   Abstract Accretion disks around both stellar-mass and supermassive black holes (BHs) are likely often warped. Whenever a disk is warped, its scale height varies with azimuth. Sufficiently strong warps cause extreme compressions of the scale height, which fluid parcels “bounce” off of twice per orbit to high latitudes. We study the dynamics of strong warps using (i) the nearly analytic “ring theory” of Fairbairn & Ogilvie, which we generalize to the Kerr metric, and (ii) three-dimensional general-relativistic hydrodynamic simulations of tori (“rings”) around BHs, using theH-AMRcode. We initialize a ring with a warp and study its evolution on tens of orbital periods. The simulations agree excellently with the ring theory until the warp amplitude,ψ, reaches a critical valueψ_c. Whenψ > ψ_c, the rings enter the bouncing regime. We analytically derive (and numerically validate) that ${\psi }_{\mathrm{c}}\approx {(r/r_{\mathrm{g}})}^{-1/2}$in the non-Keplerian regime, wherer_g = GM/c²is the gravitational radius, andMis the mass of the central object. Whenever the scale height bounces, the vertical velocity becomes supersonic, leading to “nozzle shocks” as gas collides at the scale height minima. Nozzle shocks damp the warp within ≈10–20 orbits, which is not captured by the ring theory. Nozzle shock dissipation leads to inflow timescales 1–2 orders of magnitude shorter than unwarpedαdisks, which may result in rapid variability, such as in changing-look active galactic nuclei or in the soft state of X-ray binaries. We propose that steady disks with strong warps may self-regulate to have amplitudes nearψ_c. 

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