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3
  • Joon Hyeop Lee
  • Mina Pak, Hye-Ran Lee
  • Lee, Joon Hyeop; Pak, Mina; Lee, Hye-Ran; Song, Hyunmi
  • 2019
  • ApJ, 872, 78L
We present our discovery of observational evidence for the coherence between galaxy rotation and the average line-of-sight motion of neighbors. We use the Calar Alto Legacy Integral Field Area (CALIFA) survey data analyzed with the Python CALIFA STARLIGHT Synthesis Organizer platform, and the NASA-Sloan Atlas catalog. After estimating the projected angular momentum vectors of 445 CALIFA galaxies, we build composite maps of their neighbor galaxies on the parameter space of line-of-sight velocity versus projected distance. The composite radial profiles of the luminosity-weighted mean velocity of neighbors show striking evidence for dynamical coherence between the rotational direction of the CALIFA galaxies and the average moving direction of their neighbor galaxies. The signal of such dynamical coherence is significant for the neighbors within 800 kpc from the CALIFA galaxies, for which the luminosity-weighted mean velocity is as large as 61.7 ± 17.6 km s-1 (3.5σ significance to the bootstrap uncertainty) when the angular momentum is measured at R e < R ≤ 2R e of each CALIFA galaxy. In the comparison of the subsamples, we find that faint, blue, or kinematically misaligned galaxies show stronger coherence with neighbor motions than bright, red, or kinematically well-aligned galaxies do. Our results indicate that (1) the rotation of a galaxy (particularly at its outskirt) is significantly influenced by interactions with its neighbors up to 800 kpc, (2) the coherence is particularly strong between faint galaxies and bright neighbors, and (3) galaxy interactions often cause internal kinematic misalignment or possibly even kinematically distinct cores.
2
  • Taehyun Jung
  • Il je Cho
  • S. Issaoun, M. D. Johnson, L. Blackburn, C. D. Brinkerink, M. Moscibrodzka, A. Chael, C. Goddi, I. Marti-Vidal, J. Wagner, S. S. Doeleman, H. Falcke, T. P. Krichbaum, K. Akiyama, U. Bach, K. L. Bouman, G. C. Bower, A. Broderick, I. Cho, G. Crew, J. Dexter, V. Fish, R. Gold, J. L. Gomez, K. Hada, A. Hernandez-Gomez, M. Janßen, M. Kino, M. Karmer, L. Loinard, R.-S. Lu, S. Markoff, D. P. Marrone, L. D. Matthews, J. M. Moran, C. Muller, E. Ros, H. Rottmann, S. Sanchez, R. P. J. Tilanus, P. de Vicente, M. Wielgus, J. A. Zensus, G.-Y. Zhao
  • 2019
  • ApJ
The Galactic center supermassive black hole Sagittarius A* (Sgr A*) is one of the most promising targets to study the dynamics of black hole accretion and outflow via direct imaging with very long baseline interferometry (VLBI). At 3.5 mm (86 GHz), the emission from Sgr A* is resolvable with the Global Millimeter VLBI Array (GMVA). We present the first observations of Sgr A* with the phased Atacama Large Millimeter/submillimeter Array (ALMA) joining the GMVA. Our observations achieve an angular resolution of ∼87 μas, improving upon previous experiments by a factor of two. We reconstruct a first image of the unscattered source structure of Sgr A* at 3.5 mm, mitigating the effects of interstellar scattering. The unscattered source has a major-axis size of 120 ± 34 μas (12 ± 3.4 Schwarzschild radii) and a symmetrical morphology (axial ratio of {1.2}-0.2+0.3), which is further supported by closure phases consistent with zero within 3σ. We show that multiple disk-dominated models of Sgr A* match our observational constraints, while the two jet-dominated models considered are constrained to small viewing angles. Our long-baseline detections to ALMA also provide new constraints on the scattering of Sgr A*, and we show that refractive scattering effects are likely to be weak for images of Sgr A* at 1.3 mm with the Event Horizon Telescope. Our results provide the most stringent constraints to date for the intrinsic morphology and refractive scattering of Sgr A*, demonstrating the exceptional contribution of ALMA to millimeter VLBI.
1
  • Jaewon Yoo
  • M. T. Soumagnac, C.G. Sabiu, R. Barkana, J. Yoo
  • 2019
  • MNRAS
Baryon Acoustic Oscillations (BAOs) in the early Universe are predicted to leave an as yet undetected signature on the relative clustering of total mass versus luminous matter. This signature, a modulation of the relative large-scale clustering of baryons and dark matter, offers a new angle to compare the large scale distribution of light versus mass. A detection of this effect would provide an important confirmation of the standard cosmological paradigm and constrain alternatives to dark matter as well as non-standard fluctuations such as Compensated Isocurvature Perturbations (CIPs). The first attempt to measure this effect in the SDSS-III BOSS Data Release 10 CMASS sample remained inconclusive but allowed to develop a method, which we detail here and use to conduct the second observational search. When using the same model as in our previous study and including CIPs in the model, the DR12 data are consistent with a null-detection, a result in tension with the strong evidence previously measured with the DR10 data. This tension remains when we use a more realistic model taking into account our knowledge of the survey flux limit, as the data then privilege a zero effect. In the absence of CIPs, we obtain a null detection consistent with both the absence of the effect and the amplitude predicted in previous theoretical studies. This shows the necessity of more accurate data in order to prove or disprove the theoretical predictions.
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