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3 results on '"Andrew W. Strong"'

1. eDIG-CHANGES. II. Project Design and Initial Results on NGC 3556

Author

Jiang-Tao Li, Li-Yuan Lu, Zhijie Qu, Robert A. Benjamin, Joel N. Bregman, Ralf-Jürgen Dettmar, Jayanne English, Taotao Fang, Judith A. Irwin, Yan Jiang, Hui Li, Guilin Liu, Paul Martini, Richard J. Rand, Yelena Stein, Andrew W. Strong, Carlos J. Vargas, Q. Daniel Wang, Jing Wang, Theresa Wiegert, Jianghui Xu, and Yang Yang

Subjects
Interstellar medium, Circumgalactic medium, Spiral galaxies, Warm ionized medium, Galaxy rotation curves, Radio continuum emission, Astrophysics, QB460-466
Abstract

The extraplanar diffuse ionized gas (eDIG) represents ionized gases traced by optical/UV lines beyond the stellar extent of galaxies. We herein introduce a novel multislit narrow-band spectroscopy method to conduct spatially resolved spectroscopy of the eDIG around a sample of nearby edge-on disk galaxies (eDIG-CHANGES). In this paper, we introduce the project design and major scientific goals, as well as a pilot study of NGC 3556 (M108). The eDIG is detected to a vertical extent of a few kiloparsecs above the disk, comparable to the X-ray and radio images. We do not see significant vertical variation of the [N ii ]/H α line ratio. A rough examination of the pressure balance between different circumgalactic medium phases indicates the magnetic field is in a rough pressure balance with the X-ray emitting hot gas and may play an important role in the global motion of both the eDIG and the hot gas in the lower halo. At the location of an Hubble Space Telescope/Cosmic Origins Spectrograph observed UV bright background active galactic nucleus ∼29 kpc from the center of NGC 3556, the magnetic pressure is much lower than that of the hot gas and the ionized gas traced by UV absorption lines, although the extrapolation of the pressure profiles may cause some biases in this comparison. By comparing the position–velocity diagrams of the optical and CO lines, we also find the dynamics of the two gas phases are consistent with each other, with no evidence of a global inflow/outflow and a maximum rotation velocity of ∼150 km s ^−1 .

Published
2024
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3. BAYESIAN ANALYSIS OF COSMIC RAY PROPAGATION: EVIDENCE AGAINST HOMOGENEOUS DIFFUSION

Author

Aaron C. Vincent, T. A. Porter, Michael P. Hobson, Gudlaugur Johannesson, Elena Orlando, Roberto Ruiz de Austri, Igor V. Moskalenko, Roberto Trotta, Farhan Feroz, P. B. Graff, Andrew W. Strong, Johannesson, G, de Austri, Rr, Vincent, Ac, Moskalenko, Iv, Orlando, E, Porter, Ta, Strong, Aw, Trotta, R, Feroz, F, Graff, P, Hobson, Mp, Science and Technology Facilities Council (STFC), Science and Technology Facilities Council [2006-2012], and Science and Technology Facilities Council

Subjects
astroparticle physics, cosmic rays, diffusion, Galaxy: general, ISM: general, methods: statistical, Parameter space, 01 natural sciences, Diffusion (business), 010303 astronomy & astrophysics, cosmic ray, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), astro-ph.HE, 0306 Physical Chemistry (incl. Structural), SUPERNOVA-REMNANTS, general [ISM], SECONDARY, ELEMENTAL COMPOSITION, astroparticle physic, Physical Sciences, 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics, Astrophysics - High Energy Astrophysical Phenomena, Bar (music), astro-ph.GA, Bayesian probability, statistical [methods], FOS: Physical sciences, Cosmic ray, FERMI-LAT OBSERVATIONS, Astronomy & Astrophysics, Article, Settore FIS/05 - Astronomia e Astrofisica, 0103 physical sciences, 0201 Astronomical and Space Sciences, Calibration, ENERGY-SPECTRA, Nested sampling algorithm, general [Galaxy], Science & Technology, NUCLEI, 010308 nuclear & particles physics, CONSTRAINTS, Astronomy and Astrophysics, Astrophysics - Astrophysics of Galaxies, Computational physics, Interstellar medium, MODEL, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), SOLAR MODULATION, EMISSION
Abstract

We present the results of the most complete ever scan of the parameter space for cosmic ray (CR) injection and propagation. We perform a Bayesian search of the main GALPROP parameters, using the MultiNest nested sampling algorithm, augmented by the BAMBI neural network machine learning package. This is the first such study to separate out low-mass isotopes ($p$, $\bar p$ and He) from the usual light elements (Be, B, C, N, O). We find that the propagation parameters that best fit $p$, $\bar p$, He data are significantly different from those that fit light elements, including the B/C and $^{10}$Be/$^9$Be secondary-to-primary ratios normally used to calibrate propagation parameters. This suggests each set of species is probing a very different interstellar medium, and that the standard approach of calibrating propagation parameters using B/C can lead to incorrect results. We present posterior distributions and best fit parameters for propagation of both sets of nuclei, as well as for the injection abundances of elements from H to Si. The input GALDEF files with these new parameters will be included in an upcoming public GALPROP update., Comment: 20 pages, 10 figures, 5 tables. v2 accepted for publication in ApJ

Published
2021

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