18 research outputs found

    Gas mass tracers in protoplanetary disks: CO is still the best

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    Protoplanetary disk mass is a key parameter controlling the process of planetary system formation. CO molecular emission is often used as a tracer of gas mass in the disk. In this study we consider the ability of CO to trace the gas mass over a wide range of disk structural parameters and search for chemical species that could possibly be used as alternative mass tracers to CO. Specifically, we apply detailed astrochemical modeling to a large set of models of protoplanetary disks around low-mass stars, to select molecules with abundances correlated with the disk mass and being relatively insensitive to other disk properties. We do not consider sophisticated dust evolution models, restricting ourselves with the standard astrochemical assumption of 0.1 μ0.1~\mu m dust. We find that CO is indeed the best molecular tracer for total gas mass, despite the fact that it is not the main carbon carrier, provided reasonable assumptions about CO abundance in the disk are used. Typically, chemical reprocessing lowers the abundance of CO by a factor of 3, compared to the case of photo-dissociation and freeze-out as the only ways of CO depletion. On average only 13% C-atoms reside in gas-phase CO, albeit with variations from 2 to 30%. CO2_2, H2_2O and H2_2CO can potentially serve as alternative mass tracers, the latter two being only applicable if disk structural parameters are known.Comment: Accepted for publication in Ap

    Star-forming complexes in the polar ring galaxy NGC660

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    Galaxies with polar rings consist of two subsystems, a disk and a ring, which rotate almost in orthogonal planes. In this paper, we analyze the parameters characterizing the composition of the interstellar medium and star formation in star-forming complexes, belonging to a polar ring galaxy NGC660. We show that star-forming regions in the ring of the galaxy are distinctively different from those in the galaxy disk. They possess substantially lower infrared luminosities, indicative of less dust mass in these regions than in a typical disk star-forming region. UV and Hα\alpha luminosities also appear to be lower in the ring, probably, being a consequence of its relatively recent formation.Comment: Accepted for publication in Open Astronomy, 6 figure

    Quantum Simulation for High Energy Physics

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    It is for the first time that Quantum Simulation for High Energy Physics (HEP) is studied in the U.S. decadal particle-physics community planning, and in fact until recently, this was not considered a mainstream topic in the community. This fact speaks of a remarkable rate of growth of this subfield over the past few years, stimulated by the impressive advancements in Quantum Information Sciences (QIS) and associated technologies over the past decade, and the significant investment in this area by the government and private sectors in the U.S. and other countries. High-energy physicists have quickly identified problems of importance to our understanding of nature at the most fundamental level, from tiniest distances to cosmological extents, that are intractable with classical computers but may benefit from quantum advantage. They have initiated, and continue to carry out, a vigorous program in theory, algorithm, and hardware co-design for simulations of relevance to the HEP mission. This community whitepaper is an attempt to bring this exciting and yet challenging area of research to the spotlight, and to elaborate on what the promises, requirements, challenges, and potential solutions are over the next decade and beyond.Comment: This is a whitepaper prepared for the topical groups CompF6 (Quantum computing), TF05 (Lattice Gauge Theory), and TF10 (Quantum Information Science) within the Computational Frontier and Theory Frontier of the U.S. Community Study on the Future of Particle Physics (Snowmass 2021). 103 pages and 1 figur

    Dust and gas in star-forming complexes in NGC 3351, NGC 5055, and NGC 5457

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    We present a study of the interstellar medium parameters in star-forming complexes (SFCs) in NGC 3351, NGC 5055, and NGC 5457 galaxies. This study concludes our previous investigations of gas and dust in a number of spiral galaxies. The data for the three galaxies confirm the following. There is a tight correlation between near-infrared and far-infrared luminosities of the extragalactic SFCs. Emission at 8 μm also shows a strong correlation with the carbon monoxide emission. Atomic and molecular gas masses do not show any strong correlation with the corresponding velocity scatters; however, in NGC 5055, we see a hint of the SFC with the largest velocity scatter being located at the galaxy periphery
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