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1. Characterizing the fundamental bending vibration of a linear polyatomic molecule for symmetry violation searches

   https://doi.org/10.1088/1367-2630/ace471  

   Jadbabaie, Arian ; Takahashi, Yuiki ; Pilgram, Nickolas H ; Conn, Chandler J ; Zeng, Yi ; Zhang, Chi ; Hutzler, Nicholas R ( July 2023 , New Journal of Physics)

   Polyatomic molecules have been identified as sensitive probes of charge-parity violating and parity violating physics beyond the Standard Model (BSM). For example, many linear triatomic molecules are both laser-coolable and have parity doublets in the ground electronic$\tilde{X}{}^2{\mathrm{\Sigma }}^{+}(010)$state arising from the bending vibration, both features that can greatly aid BSM searches. Understanding the$\tilde{X}{}^2{\mathrm{\Sigma }}^{+}(010)$state is a crucial prerequisite to precision measurements with linear polyatomic molecules. Here, we characterize the fundamental bending vibration of${}^{174}$YbOH using high-resolution optical spectroscopy on the nominally forbidden$\tilde{X}{}^2{\mathrm{\Sigma }}^{+}(010)$$\to \tilde{A}{}^2{\mathrm{\Pi }}_{1/2}(000)$transition at 588 nm. We assign 39 transitions originating from the lowest rotational levels of the$\tilde{X}{}^2{\mathrm{\Sigma }}^{+}(010)$state, and accurately model the state’s structure with an effective Hamiltonian using best-fit parameters. Additionally, we perform Stark and Zeeman spectroscopy on the$\tilde{X}{}^2{\mathrm{\Sigma }}^{+}(010)$state and fit the molecule-frame dipole moment to$D_{\mathrm{m}\mathrm{o}\mathrm{l}}=2.16(1)$Dand the effective electrong-factor to$g_S=2.07(2)$. Further, we use an empirical model to explain observed anomalous line intensities in terms of interference from spin–orbit and vibronic perturbations in the excited$\tilde{A}{}^2{\mathrm{\Pi }}_{1/2}(000)$state. Our work is an essential step toward searches for BSM physics in YbOH and other linear polyatomic molecules.

    

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2. The MASSIVE Survey. XVI. The Stellar Initial Mass Function in the Center of MASSIVE Early-type Galaxies

   https://doi.org/10.3847/1538-4357/ac69ea  

   Gu, Meng ; Greene, Jenny E. ; Newman, Andrew B. ; Kreisch, Christina ; Quenneville, Matthew E. ; Ma, Chung-Pei ; Blakeslee, John P. ( June 2022 , The Astrophysical Journal)

   The stellar initial mass function (IMF) is a fundamental property in the measurement of stellar masses and galaxy star formation histories. In this work, we focus on the most massive galaxies in the nearby universe$\log (M_{\star }/M_{\odot })>11.2$. We obtain high-quality Magellan/LDSS-3 long-slit spectroscopy with a wide wavelength coverage of 0.4–1.01μm for 41 early-type galaxies (ETGs) in the MASSIVE survey and derive high signal-to-noise spectra within an aperture ofR_e/8. Using detailed stellar synthesis models, we constrain the elemental abundances and stellar IMF of each galaxy through full spectral modeling. All the ETGs in our sample have an IMF that is steeper than a Milky Way (Kroupa) IMF. The best-fit IMF mismatch parameter,α_IMF= (M/L)/(M/L)_MW, ranges from 1.1 to 3.1, with an average of 〈α_IMF〉 = 1.84, suggesting that on average, the IMF is more bottom heavy than Salpeter. Comparing the estimated stellar masses with the dynamical masses, we find that most galaxies have stellar masses that are smaller than their dynamical masses within the 1σuncertainty. We complement our sample with lower-mass galaxies from the literature and confirm that$\log ({\alpha }_{\mathrm{IMF}})$is positively correlated with$\log (\sigma )$,$\log (M_{\star })$, and$\log (M_{\mathrm{dyn}})$. From the combined sample, we show that the IMF in the centers of more massive ETGs is more bottom heavy. In addition, we find that$\log ({\alpha }_{\mathrm{IMF}})$is positively correlated with both [Mg/Fe] and the estimated total metallicity [Z/H]. We find suggestive evidence that the effective stellar surface density Σ_Kroupamight be responsible for the variation ofα_IMF. We conclude thatσ, [Mg/Fe], and [Z/H] are the primary drivers of the global stellar IMF variation.

    

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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)

   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${\mathit{}}_{12/13}\equiv I{[}^{12}\mathrm{CO}(J=1\to 0)]/I{[}^{13}\mathrm{CO}(J=1\to 0)]$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. Acceleration and Spectral Redistribution of Cosmic Rays in Radio-jet Shear Flows

   https://doi.org/10.3847/1538-4357/acfda9  

   Webb, G. M. ; Xu, Y. ; Biermann, P. L. ; Al-Nussirat, S. ; Mostafavi, P. ; Li, G. ; Barghouty, A. F. ; Zank, G. P. ( November 2023 , The Astrophysical Journal)

   A steady-state, semi-analytical model of energetic particle acceleration in radio-jet shear flows due to cosmic-ray viscosity obtained by Webb et al. is generalized to take into account more general cosmic-ray boundary spectra. This involves solving a mixed Dirichlet–Von Neumann boundary value problem at the edge of the jet. The energetic particle distribution functionf₀(r,p) at cylindrical radiusrfrom the jet axis (assumed to lie along thez-axis) is given by convolving the particle momentum spectrum$f_0(\infty ,p\prime )$with the Green’s function$G(r,p;p\prime )$, which describes the monoenergetic spectrum solution in which$f_0\to \delta (p-p\prime )$asr→ ∞ . Previous work by Webb et al. studied only the Green’s function solution for$G(r,p;p\prime )$. In this paper, we explore for the first time, solutions for more general and realistic forms for$f_0(\infty ,p\prime )$. The flow velocityu=u(r)e_zis along the axis of the jet (thez-axis).uis independent ofz, andu(r) is a monotonic decreasing function ofr. The scattering time$\tau {(r,p)={\tau }_0(p/p_0)}^{\alpha }$in the shear flow region 0 <r<r₂, and$\tau {(r,p)={\tau }_0(p/p_0)}^{\alpha }{(r/r_2)}^s$, wheres> 0 in the regionr>r₂is outside the jet. Other original aspects of the analysis are (i) the use of cosmic ray flow lines in (r,p) space to clarify the particle spatial transport and momentum changes and (ii) the determination of the probability distribution${\psi }_p(r,p;p\prime )$that particles observed at (r,p) originated fromr→ ∞ with momentum$p\prime$. The acceleration of ultrahigh-energy cosmic rays in active galactic nuclei jet sources is discussed. Leaky box models for electron acceleration are described.

    

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5. Bounds on eigenfunctions of quantum cat maps

   https://doi.org/10.1088/1402-4896/ad0331  

   Kim, Elena ; Koirala, Robert ( October 2023 , Physica Scripta)

   We studyℓ^∞norms ofℓ²-normalized eigenfunctions of quantum cat maps. For maps with short quantum periods (constructed by Bonechi and de Biévre in F Bonechi and S De Bièvre (2000,Communications in Mathematical Physics,211, 659–686)) we show that there exists a sequence of eigenfunctionsuwith$\parallel u{\parallel }_{\infty }\gtrsim {\left(\log N\right)}^{-1/2}$. For general eigenfunctions we show the upper bound$\parallel u{\parallel }_{\infty }\lesssim {\left(\log N\right)}^{-1/2}$. Here the semiclassical parameter is$h={\left(2\pi N\right)}^{-1}$. Our upper bound is analogous to the one proved by Bérard in P Bérard (1977,Mathematische Zeitschrift,155, 249-276) for compact Riemannian manifolds without conjugate points.

    

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