18 research outputs found
Gas mass tracers in protoplanetary disks: CO is still the best
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 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%. CO, HO and HCO 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
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 H 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
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
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