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1. The Intensity Profile of the Solar Supergranulation

Author

Goldbaum, N. J., Rast, M. P., Ermolli, I., Sands, J. S., and Berrilli, F.

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

We have measured the average radial (cell center to network boundary) profile of the continuum intensity contrast associated with supergranular flows using data from the Precision Solar Photometric Telescope (PSPT) at the Mauna Loa Solar Observatory (MLSO). After removing the contribution of the network flux elements by the application of masks based on Ca II K intensity and averaging over more than 10^5 supergranular cells, we find a ~ 0.1% decrease in red and blue continuum intensity from the supergranular cell centers outward, corresponding to a ~ 1.0 K decrease in brightness temperature across the cells. The radial intensity profile may be caused either by the thermal signal associated with the supergranular flows or a variation in the packing density of unresolved magnetic flux elements. These are not unambiguously distinguished by the observations, and we raise the possibility that the network magnetic fields play an active role in supergranular scale selection by enhancing the radiative cooling of the deep photosphere at the cell boundaries., Comment: Accepted to ApJ

Published
2009
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2. THE AGORA HIGH-RESOLUTION GALAXY SIMULATIONS COMPARISON PROJECT. II. ISOLATED DISK TEST

Author

Kim, J, Agertz, O, Teyssier, R, Butler, M, Ceverino, D, Choi, J, Feldmann, R, Keller, B, Lupi, A, Quinn, T, Revaz, Y, Wallace, S, Gnedin, N, Leitner, S, Shen, S, Smith, B, Thompson, R, Turk, M, Abel, T, Arraki, K, Benincasa, S, Chakrabarti, S, Degraf, C, Dekel, A, Goldbaum, N, Hopkins, P, Hummels, C, Klypin, A, Li, H, Madau, P, Mandelker, N, Mayer, L, Nagamine, K, Nickerson, S, O'Shea, B, Primack, J, Roca-Fabrega, S, Semenov, V, Shimizu, I, Simpson, C, Todoroki, K, Wadsley, J, Wise, J, Kim J. -H., Agertz O., Teyssier R., Butler M. J., Ceverino D., Choi J. -H., Feldmann R., Keller B. W., Lupi A., Quinn T., Revaz Y., Wallace S., Gnedin N. Y., Leitner S. N., Shen S., Smith B. D., Thompson R., Turk M. J., Abel T., Arraki K. S., Benincasa S. M., Chakrabarti S., Degraf C., Dekel A., Goldbaum N. J., Hopkins P. F., Hummels C. B., Klypin A., Li H., Madau P., Mandelker N., Mayer L., Nagamine K., Nickerson S., O'Shea B. W., Primack J. R., Roca-Fabrega S., Semenov V., Shimizu I., Simpson C. M., Todoroki K., Wadsley J. W., Wise J. H., Kim, J, Agertz, O, Teyssier, R, Butler, M, Ceverino, D, Choi, J, Feldmann, R, Keller, B, Lupi, A, Quinn, T, Revaz, Y, Wallace, S, Gnedin, N, Leitner, S, Shen, S, Smith, B, Thompson, R, Turk, M, Abel, T, Arraki, K, Benincasa, S, Chakrabarti, S, Degraf, C, Dekel, A, Goldbaum, N, Hopkins, P, Hummels, C, Klypin, A, Li, H, Madau, P, Mandelker, N, Mayer, L, Nagamine, K, Nickerson, S, O'Shea, B, Primack, J, Roca-Fabrega, S, Semenov, V, Shimizu, I, Simpson, C, Todoroki, K, Wadsley, J, Wise, J, Kim J. -H., Agertz O., Teyssier R., Butler M. J., Ceverino D., Choi J. -H., Feldmann R., Keller B. W., Lupi A., Quinn T., Revaz Y., Wallace S., Gnedin N. Y., Leitner S. N., Shen S., Smith B. D., Thompson R., Turk M. J., Abel T., Arraki K. S., Benincasa S. M., Chakrabarti S., Degraf C., Dekel A., Goldbaum N. J., Hopkins P. F., Hummels C. B., Klypin A., Li H., Madau P., Mandelker N., Mayer L., Nagamine K., Nickerson S., O'Shea B. W., Primack J. R., Roca-Fabrega S., Semenov V., Shimizu I., Simpson C. M., Todoroki K., Wadsley J. W., and Wise J. H.

Abstract

Using an isolated Milky Way-mass galaxy simulation, we compare results from nine state-of-the-art gravito-hydrodynamics codes widely used in the numerical community. We utilize the infrastructure we have built for the AGORA High-resolution Galaxy Simulations Comparison Project. This includes the common disk initial conditions, common physics models (e.g., radiative cooling and UV background by the standardized package Grackle) and common analysis toolkit yt, all of which are publicly available. Subgrid physics models such as Jeans pressure floor, star formation, supernova feedback energy, and metal production are carefully constrained across code platforms. With numerical accuracy that resolves the disk scale height, we find that the codes overall agree well with one another in many dimensions including: gas and stellar surface densities, rotation curves, velocity dispersions, density and temperature distribution functions, disk vertical heights, stellar clumps, star formation rates, and Kennicutt-Schmidt relations. Quantities such as velocity dispersions are very robust (agreement within a few tens of percent at all radii) while measures like newly formed stellar clump mass functions show more significant variation (difference by up to a factor of ∼3). Systematic differences exist, for example, between mesh-based and particle-based codes in the low-density region, and between more diffusive and less diffusive schemes in the high-density tail of the density distribution. Yet intrinsic code differences are generally small compared to the variations in numerical implementations of the common subgrid physics such as supernova feedback. Our experiment reassures that, if adequately designed in accordance with our proposed common parameters, results of a modern high-resolution galaxy formation simulation are more sensitive to input physics than to intrinsic differences in numerical schemes.

Published
2016

4. THEAGORAHIGH-RESOLUTION GALAXY SIMULATIONS COMPARISON PROJECT. II. ISOLATED DISK TEST

Author

Daniel Ceverino, Thomas P. Quinn, Oscar Agertz, Brian W. O'Shea, Ikkoh Shimizu, Ben W. Keller, Vadim A. Semenov, Colin DeGraf, Spencer Clark Wallace, John H. Wise, Joel R. Primack, Alessandro Lupi, Nir Mandelker, Lucio Mayer, Keita Todoroki, Britton D. Smith, Jun-Hwan Choi, Avishai Dekel, Robert Thompson, Samantha M. Benincasa, Philip F. Hopkins, Kentaro Nagamine, Sijing Shen, Robert Feldmann, Cameron Hummels, Nickolay Y. Gnedin, Tom Abel, Kenza S. Arraki, Samuel N. Leitner, Sukanya Chakrabarti, James Wadsley, Michael J. Butler, Santi Roca-Fàbrega, Anatoly Klypin, Romain Teyssier, Christine M. Simpson, Piero Madau, Sarah Nickerson, Nathan J. Goldbaum, Matthew J. Turk, Ji-hoon Kim, Yves Revaz, Hui Li, Kim, J, Agertz, O, Teyssier, R, Butler, M, Ceverino, D, Choi, J, Feldmann, R, Keller, B, Lupi, A, Quinn, T, Revaz, Y, Wallace, S, Gnedin, N, Leitner, S, Shen, S, Smith, B, Thompson, R, Turk, M, Abel, T, Arraki, K, Benincasa, S, Chakrabarti, S, Degraf, C, Dekel, A, Goldbaum, N, Hopkins, P, Hummels, C, Klypin, A, Li, H, Madau, P, Mandelker, N, Mayer, L, Nagamine, K, Nickerson, S, O'Shea, B, Primack, J, Roca-Fabrega, S, Semenov, V, Shimizu, I, Simpson, C, Todoroki, K, Wadsley, J, and Wise, J

Subjects
Cosmology and Nongalactic Astrophysics (astro-ph.CO), formation [galaxies], Radiative cooling, ISM: structure, astro-ph.GA, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Astronomy & Astrophysics, Physical Chemistry, Atomic, 01 natural sciences, methods: numerical, 010305 fluids & plasmas, Particle and Plasma Physics, kinematics and dynamics [galaxies], 0103 physical sciences, Galaxy formation and evolution, galaxies: formation, Nuclear, theory, 010303 astronomy & astrophysics, evolution [galaxies], Astrophysics::Galaxy Astrophysics, Galaxy rotation curve, Physics, theory [cosmology], Star formation, Molecular, numerical [methods], Astronomy and Astrophysics, Scale height, Astrophysics - Astrophysics of Galaxies, Galaxy, Supernova, Distribution function, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), astro-ph.CO, galaxies: kinematics and dynamic, structure [ISM], galaxies: evolution, Astronomical and Space Sciences, Astrophysics - Cosmology and Nongalactic Astrophysics, Physical Chemistry (incl. Structural)
Abstract

Using an isolated Milky Way-mass galaxy simulation, we compare results from 9 state-of-the-art gravito-hydrodynamics codes widely used in the numerical community. We utilize the infrastructure we have built for the AGORA High-resolution Galaxy Simulations Comparison Project. This includes the common disk initial conditions, common physics models (e.g., radiative cooling and UV background by the standardized package Grackle) and common analysis toolkit yt, all of which are publicly available. Subgrid physics models such as Jeans pressure floor, star formation, supernova feedback energy, and metal production are carefully constrained across code platforms. With numerical accuracy that resolves the disk scale height, we find that the codes overall agree well with one another in many dimensions including: gas and stellar surface densities, rotation curves, velocity dispersions, density and temperature distribution functions, disk vertical heights, stellar clumps, star formation rates, and Kennicutt-Schmidt relations. Quantities such as velocity dispersions are very robust (agreement within a few tens of percent at all radii) while measures like newly-formed stellar clump mass functions show more significant variation (difference by up to a factor of ~3). Systematic differences exist, for example, between mesh-based and particle-based codes in the low density region, and between more diffusive and less diffusive schemes in the high density tail of the density distribution. Yet intrinsic code differences are generally small compared to the variations in numerical implementations of the common subgrid physics such as supernova feedback. Our experiment reassures that, if adequately designed in accordance with our proposed common parameters, results of a modern high-resolution galaxy formation simulation are more sensitive to input physics than to intrinsic differences in numerical schemes., 28 pages, 35 figures, Accepted for publication in the Astrophysical Journal, Image resolution greatly reduced, High-resolution version of this article is available at http://www.jihoonkim.org/agora/AGORA_Paper4_draft.pdf, The first paper of the AGORA Initiative is at http://adsabs.harvard.edu/abs/2014ApJS..210...14K, More information on AGORA is at http://www.AGORAsimulations.org/

Published
2016
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