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  1. Abstract We present 1.3 mm (230 GHz) observations of the recent and nearby Type II supernova, SN 2023ixf, obtained with the Submillimeter Array (SMA) at 2.6–18.6 days after explosion. The observations were obtained as part the SMA Large Program, POETS (Pursuit of Extragalactic Transients with the SMA). We do not detect any emission at the location of SN 2023ixf, with the deepest limits of L ν (230 GHz) ≲ 8.6 × 10 25 erg s −1 Hz −1 at 2.7 and 7.7 days, and L ν (230 GHz) ≲ 3.4 × 10 25 erg s −1 Hz −1 at 18.6 days. These limits are about a factor of 2 times dimmer than the millimeter emission from SN 2011dh (IIb), about 1 order of magnitude dimmer compared to SN 1993J (IIb) and SN 2018ivc (IIL), and about 30 times dimmer than the most luminous nonrelativistic SNe in the millimeter band (Type IIb/Ib/Ic). Using these limits in the context of analytical models that include synchrotron self-absorption and free–free absorption, we place constraints on the proximate circumstellar medium around the progenitor star, to a scale of ∼2 × 10 15 cm, excluding the range M ̇ ∼ few × 10 − 6 − 10 − 2 M ⊙ yr −1 (for a wind velocity, v w = 115 km s −1 , and ejecta velocity, v ej ∼ (1 − 2) × 10 4 km s −1 ). These results are consistent with an inference of the mass-loss rate based on optical spectroscopy (∼2 × 10 −2 M ⊙ yr −1 for v w = 115 km s −1 ), but are in tension with the inference from hard X-rays (∼7 × 10 −4 M ⊙ yr −1 for v w = 115 km s −1 ). This tension may be alleviated by a nonhomogeneous and confined CSM, consistent with results from high-resolution optical spectroscopy. 
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    Free, publicly-accessible full text available July 1, 2024
  2. Abstract

    We use molecular line data from the Atacama Large Millimeter/submillimeter Array, Submillimeter Array, James Clerk Maxwell Telescope, and NANTEN2 to study the multiscale (∼15–0.005 pc) velocity statistics in the massive star formation region NGC 6334. We find that the nonthermal motions revealed by the velocity dispersion function (VDF) stay supersonic over scales of several orders of magnitude. The multiscale nonthermal motions revealed by different instruments do not follow the same continuous power law, which is because the massive star formation activities near central young stellar objects have increased the nonthermal motions in small-scale and high-density regions. The magnitudes of VDFs vary in different gas materials at the same scale, where the infrared dark clump N6334S in an early evolutionary stage shows a lower level of nonthermal motions than other more evolved clumps due to its more quiescent star formation activity. We find possible signs of small-scale-driven (e.g., by gravitational accretion or outflows) supersonic turbulence in clump N6334IV with a three-point VDF analysis. Our results clearly show that the scaling relation of velocity fields in NGC 6334 deviates from a continuous and universal turbulence cascade due to massive star formation activities.

     
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  3. 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 (θB), column density gradients (θNG), local gravity (θLG), and velocity gradients (θVG) to investigate the multi-scale (from ∼30 to 0.003 pc) physical properties in NGC 6334. We find that the relative orientation betweenθBandθNGchanges from statistically more perpendicular to parallel as column density (NH2) increases, which is a signature of trans-to-sub-Alfvénic turbulence at complex/cloud scales as revealed by previous numerical studies. BecauseθNGandθLGare preferentially aligned within the NGC 6334 cloud, we suggest that the more parallel alignment betweenθBandθNGat higherNH2is because the magnetic field line is dragged by gravity. At even higherNH2, the angle betweenθBandθNGorθLGtransits 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 betweenθBandθVGthroughout our studiedNH2range, 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 withNH2, but the KTH method may fail at highNH2due to the impact of star formation feedback.

     
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  4. Abstract We present the first detailed polarimetric studies of Cygnus A at 230 GHz with the Submillimeter Array (SMA) to constrain the mass accretion rate onto its supermassive black hole. We detected the polarized emission associated with the core at a fractional polarization of . This low fractional polarization suggests that the polarized emission is highly depolarized. One of the possible explanations is due to a significant variance in the Faraday rotation measure within the synthesized beam. By assuming the Faraday depolarization caused by inhomogeneous column density of the magnetized plasma associated with the surrounding radiatively-inefficient accretion flow within the SMA beam, we derived the constraint on the mass accretion rate to be larger than 0.15 yr −1 at the Bondi radius. The derived constraint indicates that an adiabatic inflow–outflow solution or an advection-dominated accretion flow should be preferable as the accretion flow model in order to explain the jet power of Cygnus A. 
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  6. Abstract We report the first >99% confidence detection of X-ray polarization in BL Lacertae. During a recent X-ray/ γ -ray outburst, a 287 ks observation (2022 November 27–30) was taken using the Imaging X-ray Polarimetry Explorer (IXPE), together with contemporaneous multiwavelength observations from the Neil Gehrels Swift observatory and XMM-Newton in soft X-rays (0.3–10 keV), NuSTAR in hard X-rays (3–70 keV), and optical polarization from the Calar Alto and Perkins Telescope observatories. Our contemporaneous X-ray data suggest that the IXPE energy band is at the crossover between the low- and high-frequency blazar emission humps. The source displays significant variability during the observation, and we measure polarization in three separate time bins. Contemporaneous X-ray spectra allow us to determine the relative contribution from each emission hump. We find >99% confidence X-ray polarization Π 2 – 4 keV = 21.7 − 7.9 + 5.6 % and electric vector polarization angle ψ 2–4keV = −28.°7 ± 8.°7 in the time bin with highest estimated synchrotron flux contribution. We discuss possible implications of our observations, including previous IXPE BL Lacertae pointings, tentatively concluding that synchrotron self-Compton emission dominates over hadronic emission processes during the observed epochs. 
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