511 research outputs found
An HI interstellar bubble surrounding WR85 and RCW118
We analyze the distribution of the interstellar matter in the environs of the
Wolf-Rayet star LSS3982 (= WR85, WN6+OB?) linked to the optical ring nebula
RCW118. Our study is based on neutral hydrogen 21cm-line data belonging to the
Southern Galactic Plane Survey (SGPS).
The analysis of the HI data allowed the identification of a neutral hydrogen
interstellar bubble related to WR 85 and the 25' diameter ring nebula RCW118.
The HI bubble was detected at a systemic velocity of -21.5 km/s, corresponding
to a kinematical distance of 2.8+/-1.1 kpc, compatible with the stellar
distance. The neutral stucture is about 25' in radius or 21+/-8 pc, and is
expanding at 9+/-2 km/s. The associated ionized and neutral masses amount to
3000 Mo. The CO emission distribution depicts a region lacking CO coincident in
position and velocity with the HI structure. The 9'.3 diameter inner optical
nebula appears to be related to the approaching part of the neutral atomic
shell. The HI void and shell are the neutral gas counterparts of the optical
bubble and have very probably originated in the action of the strong stellar
wind of the central star during the O-type and WR phases on the surrounding
interstellar medium. The HI bubble appears to be in the momentun conserving
stage.Comment: 9 pages, 7 figures, accepted in MNRA
Milky Way Kinematics: Measurements at the Subcentral Point of the Fourth Quadrant
We use atomic hydrogen (HI) data from the Southern Galactic Plane Survey to
study the kinematics of the fourth quadrant of the Milky Way. By measuring the
terminal velocity as a function of longitude throughout the fourth Galactic
quadrant we have derived the most densely sampled rotation curve available for
the Milky Way between 3 < R < 8 kpc. We determine a new joint rotation curve
fit for the first and fourth quadrants, which can be used for kinematic
distances interior to the Solar circle. From our data we place new limits on
the peak to peak variation of streaming motions in the fourth quadrant to be
~10 km/s. We show that the shape of the average HI profile beyond the terminal
velocity is consistent with gas of three velocity dispersions, a cold component
with km/s, a warmer component with km/s and a
fast component with km/s. Examining the widths with Galactic
radius we find that the narrowest two components show little variation with
radius and their small scale fluctuations track each other very well,
suggesting that they share the same cloud-to-cloud motions. The width of the
widest component is constant until R<4 kpc, where it increases sharply.Comment: 36 pages, 10 figures, accepted to ApJ. Full electronic version of
table 1 available at
ftp://ftp.atnf.csiro.au/pub/people/nmcclure/papers/velocity_tab1.te
A Complete Atlas of HI Absorption toward HII Regions in the Southern Galactic Plane Survey (SGPS1)
We present a complete catalog of H I emission and absorption spectrum pairs,
toward H II regions, detectable within the boundaries of the Southern Galactic
Plane Survey (SGPS I), a total of 252 regions. The catalog is presented in
graphical, numerical and summary formats. We demonstrate an application of this
new dataset through an investigation of the locus of the Near 3kpc Arm.Comment: Accepted for publication by ApJS Feb 6, 2014. Data files and Figure
Set (252 images) to appear in the on-line version of the journa
Comment on the paper "Calorimetric Dark Matter Detection with Galactic Center Gas Clouds"
The paper "Calorimetric Dark Matter Detection with Galactic Center Gas
Clouds" (Bhoonah et al. 2018) aims to derive limits on dark matter interactions
by demanding that heat transfer due to DM interactions is less than that by
astrophysical cooling, using clouds in the hot, high-velocity nuclear outflow
wind of the Milky Way ( K, 330 km/s).
We argue that clouds in such an extreme environment cannot be assumed to be
stable over the long timescales associated with their radiative cooling rates.
Furthermore, Bhoonah et al. (2018) uses incorrect parameters for their clouds.Comment: 2 pages, 1 figure. Version appearing in Phys. Rev. Let
GASS High Velocity Clouds in the Region of the Magellanic Leading Arm
We present a catalog of high-velocity clouds in the region of the Magellanic
Leading Arm. The catalog is based on neutral hydrogen (\HI) observations from
the Parkes Galactic All-Sky Survey (GASS). Excellent spectral resolution allows
clouds with narrow-line components to be resolved. The total number of detected
clouds is 419. We describe the method of cataloging and present the basic
parameters of the clouds. We discuss the general distribution of the
high-velocity clouds and classify the clouds based on their morphological type.
The presence of a significant number of head-tail clouds and their distribution
in the region is discussed in the context of Magellanic System simulations. We
suggest that ram-pressure stripping is a more important factor than tidal
forces for the morphology and formation of the Magellanic Leading Arm and that
different environmental conditions might explain the morphological difference
between the Magellanic Leading Arm and Magellanic Stream. We also discuss a
newly identified population of clouds that forms the LA IV and a new diffuse
bridge-like feature connecting the LA II and III complexes.Comment: 20 pages, 24 figures, accepted by ApJ on December 14, 201
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