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Perturbed Angular Distributions from 120,122, 124Sn(40Ar, 4n)156, 158, 160Er Reaction Products Recoiling in Vacuum
SDSS IV MaNGA - Rotation Velocity Lags in the Extraplanar Ionized Gas from MaNGA Observations of Edge-on Galaxies
We present a study of the kinematics of the extraplanar ionized gas around
several dozen galaxies observed by the Mapping of Nearby Galaxies at the Apache
Point Observatory (MaNGA) survey. We considered a sample of 67 edge-on galaxies
out of more than 1400 extragalactic targets observed by MaNGA, in which we
found 25 galaxies (or 37%) with regular lagging of the rotation curve at large
distances from the galactic midplane. We model the observed emission
velocity fields in the galaxies, taking projection effects and a simple model
for the dust extinction into the account. We show that the vertical lag of the
rotation curve is necessary in the modeling, and estimate the lag amplitude in
the galaxies. We find no correlation between the lag and the star formation
rate in the galaxies. At the same time, we report a correlation between the lag
and the galactic stellar mass, central stellar velocity dispersion, and axial
ratio of the light distribution. These correlations suggest a possible higher
ratio of infalling-to-local gas in early-type disk galaxies or a connection
between lags and the possible presence of hot gaseous halos, which may be more
prevalent in more massive galaxies. These results again demonstrate that
observations of extraplanar gas can serve as a potential probe for accretion of
gas.Comment: 13 pages, 11 figures, accepted for publication in Ap
High resolution observations of SiO masers: comparing the spatial distribution at 43 and 86 GHz
We present sub-milliarcsecond observations of SiO masers in the late-type
stars IRC +10011 and Chi Cyg. We have used the NRAO Very Long Baseline Array
(VLBA) to map the 43 GHz (v=1, 2 J=1-0) and the 86 GHz (v=1, 2 J=2-1) SiO
masers. All the transitions have been imaged except the v=2 J=2-1 in IRC
+10011. We report the first VLBI map of the v=1 J=2-1 28SiO maser in IRC +10011
as well as the first VLBA images of SiO masers in an S-type Mira variable, Chi
Cyg. In this paper we have focused on the study of the relative spatial
distribution of the different observed lines. We have found that in some cases
the observational results are not reproduced by the current theoretical pumping
models, either radiative or collisional. In particular, for IRC +10011, the v=1
J=1-0 and J=2-1 28SiO lines have different spatial distributions and emitting
region sizes, the J=2-1 emission being located in an outer region of the
envelope. For Chi Cyg, the distributions also differ, but the sizes of the
masing regions are comparable. We suggest that the line overlaps between
ro-vibrational transitions of two abundant molecular species, H2O and 28SiO, is
a possible explanation for the discrepancies found between the observations and
the theoretical predictions. We have introduced this overlapping process in the
calculations of the excitation of the SiO molecule. We conclude that the line
overlaps can strongly affect the excitation of SiO and may reproduce the
unexpected observational results for the two sources studied.Comment: 16 pages, 12 figure
On the Structure and Scale of Cosmic Ray Modified Shocks
Strong astrophysical shocks, diffusively accelerating cosmic rays (CR) ought
to develop CR precursors. The length of such precursor is believed to
be set by the ratio of the CR mean free path to the shock speed,
i.e., , which is formally
independent of the CR pressure . However, the X-ray observations of
supernova remnant shocks suggest that the precursor scale may be significantly
shorter than which would question the above estimate unless the
magnetic field is strongly amplified and the gyroradius is strongly
reduced over a short (unresolved) spatial scale. We argue that while the CR
pressure builds up ahead of the shock, the acceleration enters into a strongly
nonlinear phase in which an acoustic instability, driven by the CR pressure
gradient, dominates other instabilities (at least in the case of low
plasma). In this regime the precursor steepens into a strongly nonlinear front
whose size scales with \emph{the CR pressure}as , where is the scale of
the developed acoustic turbulence, and is the ratio of CR to gas
pressure. Since , the precursor scale reduction may be strong
in the case of even a moderate gas heating by the CRs through the acoustic and
(possibly also) the other instabilities driven by the CRs.Comment: EPS 2010 paper, to appear in PPC
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