19 research outputs found
Magnetic Diagram of the High-Pressure Stabilized Multiferroic Perovskites of the BiFe1-yScyO3 Series
Magnetic properties of the high-pressure stabilized perovskite BiFe1-yScyO3 phases (0.1 ≤ y ≤ 0.9) have been studied by means of magnetization measurements and neutron diffraction. The metastable perovskites of this series undergo irreversible polymorphic transformations upon annealing, the phenomenon referred to as conversion polymorphism. It has been found that the solid solutions with y ≥ 0.70 exhibit no long-range magnetic ordering regardless of their polymorph modification, while those with y ≤ 0.60 are all antiferromagnets. Depending on the scandium content, temperature and structural distortions, three types of the antiferromagnetic orderings, involving collinear, canted and cycloidal spin arrangements, have been revealed in the phases obtained via conversion polymorphism and the corresponding magnetic phase diagram has been suggested
CO Multi-line Imaging of Nearby Galaxies (COMING). III. Dynamical effect on molecular gas density and star formation in the barred spiral galaxy NGC 4303
We present the results of CO(=1-0) and CO(=1-0)
simultaneous mappings toward the nearby barred spiral galaxy NGC 4303 as a part
of the CO Multi-line Imaging of Nearby Galaxies (COMING) project. Barred spiral
galaxies often show lower star-formation efficiency (SFE) in their bar region
compared to the spiral arms. In this paper, we examine the relation between the
SFEs and the volume densities of molecular gas in the eight
different regions within the galactic disk with CO data combined with archival
far-ultraviolet and 24 m data. We confirmed that SFE in the bar region is
lower by 39% than that in the spiral arms. Moreover, velocity-alignment
stacking analysis was performed for the spectra in the individual regions. The
integrated intensity ratios of CO to CO () range from
10 to 17 as the results of stacking. Fixing a kinetic temperature of molecular
gas, was derived from via non-local thermodynamic
equilibrium (non-LTE) analysis. The density in the bar is lower
by 31-37% than that in the arms and there is a rather tight positive
correlation between SFEs and , with a correlation coefficient of
. Furthermore, we found a dependence of on the velocity
dispersion of inter-molecular clouds (). Specifically,
increases as increases when km s. On the other hand, decreases as increases when km s. These relations
indicate that the variations of SFE could be caused by the volume densities of
molecular gas, and the volume densities could be governed by the dynamical
influence such as cloud-cloud collisions, shear and enhanced inner-cloud
turbulence.Comment: 15 pages, 8 figures, accepted for publication in PAS
CI and CO in Nearby Spiral Galaxies -- I. Line Ratio and Abundance Variations at ~ 200 pc Scales
We present new neutral atomic carbon [CI](3P1-3P0) mapping observations
within the inner ~7 kpc and ~4 kpc of the disks of NGC3627 and NGC4321 at a
spatial resolution of 190 pc and 270 pc, respectively, using the ALMA Atacama
Compact Array (ACA). We combine these with the CO(2-1) data from PHANGS-ALMA,
and literature [CI] and CO data for two other starburst and/or active galactic
nucleus (AGN) galaxies (NGC1808, NGC7469), to study: a) the spatial
distributions of CI and CO emission; b) the observed line ratio RCICO =
I_[CI](1-0)/I_CO(2-1) as a function of various galactic properties; and c) the
abundance ratio of [CI/CO]. We find excellent spatial correspondence between CI
and CO emission and nearly uniform RCICO ~0.1 across the majority of the
star-forming disks of NGC3627 and NGC4321. However, RCICO strongly varies from
~0.05 at the centre of NGC4321 to >0.2-0.5 in NGC1808's starburst centre and
NGC7469's centre with an X-ray AGN. Meanwhile, RCICO does not obviously vary
with , similar to the prediction of PDR models. We also find a mildly
decreasing RCICO with an increasing metallicity over 0.7-0.85 solar
metallicity, consistent with the literature. Assuming various typical ISM
conditions representing GMCs, active star-forming regions and strong
starbursting environments, we calculate the LTE radiative transfer and estimate
the [CI/CO] abundance ratio to be ~0.1 across the disks of NGC3627 and NGC4321,
similar to previous large-scale findings in Galactic studies. However, this
abundance ratio likely has a substantial increase to ~1 and >1-5 in NGC1808's
starburst and NGC7469's strong AGN environments, respectively, in line with the
expectations for cosmic-ray dominated region (CRDR) and X-ray dominated region
(XDR) chemistry. Finally, we do not find a robust evidence for a generally
CO-dark, CI-bright gas in the disk areas we probed. (abbreviated)Comment: 23 pages, 13 figures and one table in total (17 pages and 9 figures
in main text). Accepted for publication in A&A. For associated data cubes and
moment maps, see
https://www.canfar.net/storage/vault/list/phangs/RELEASES/DZLIU_etal_202
CO Multi-line Imaging of Nearby Galaxies (COMING) IV. Overview of the Project
Observations of the molecular gas in galaxies are vital to understanding the
evolution and star-forming histories of galaxies. However, galaxies with
molecular gas maps of their whole discs having sufficient resolution to
distinguish galactic structures are severely lacking. Millimeter wavelength
studies at a high angular resolution across multiple lines and transitions are
particularly needed, severely limiting our ability to infer the universal
properties of molecular gas in galaxies. Hence, we conducted a legacy project
with the 45 m telescope of the Nobeyama Radio Observatory, called the CO
Multi-line Imaging of Nearby Galaxies (COMING), which simultaneously observed
147 galaxies with high far-infrared flux in CO, CO, and CO
lines. The total molecular gas mass was derived using the standard
CO-to-H conversion factor and found to be positively correlated with the
total stellar mass derived from the WISE m band data. The fraction of
the total molecular gas mass to the total stellar mass in galaxies does not
depend on their Hubble types nor the existence of a galactic bar, although when
galaxies in individual morphological types are investigated separately, the
fraction seems to decrease with the total stellar mass in early-type galaxies
and vice versa in late-type galaxies. No differences in the distribution of the
total molecular gas mass, stellar mass, and the total molecular gas to stellar
mass ratio was observed between barred and non-barred galaxies, which is likely
the result of our sample selection criteria, in that we prioritized observing
FIR bright (and thus molecular gas-rich) galaxies.Comment: Accepted for publication in PASJ; 47 pages, 5 tables, 29 figures.
On-line supplementary images are available at this URL
(https://astro3.sci.hokudai.ac.jp/~radio/coming/publications/). CO data is
available at the Japanese Virtual Observatory (JVO) website
(https://jvo.nao.ac.jp/portal/nobeyama/coming.do) and the project website
(https://astro3.sci.hokudai.ac.jp/~radio/coming/data/