927 research outputs found
Molecular gas associated with IRAS 10361-5830
We analyze the distribution of the molecular gas and the dust in the
molecular clump linked to IRAS 10361-5830, located in the environs of the
bubble-shaped HII region Gum 31 in the Carina region, with the aim of
determining the main parameters of the associated material and investigating
the evolutionary state of the young stellar objects identified there.
Using the APEX telescope, we mapped the molecular emission in the J=3-2
transition of three CO isotopologues, 12CO, 13CO and C18O, over a 1.5' x 1.5'
region around the IRAS position. We also observed the high density tracers CS
and HCO+ toward the source. The cold dust distribution was analyzed using
submillimeter continuum data at 870 \mu\ obtained with the APEX telescope.
Complementary IR and radio data at different wavelengths were used to complete
the study of the ISM.
The molecular gas distribution reveals a cavity and a shell-like structure of
~ 0.32 pc in radius centered at the position of the IRAS source, with some
young stellar objects (YSOs) projected onto the cavity. The total molecular
mass in the shell and the mean H volume density are ~ 40 solar masses and
~(1-2) x 10 cm, respectively. The cold dust counterpart of the
molecular shell has been detected in the far-IR at 870 \mu\ and in Herschel
data at 350 \mu. Weak extended emission at 24 \mu\ from warm dust is projected
onto the cavity, as well as weak radio continuum emission.
A comparison of the distribution of cold and warm dust, and molecular and
ionized gas allows us to conclude that a compact HII region has developed in
the molecular clump, indicating that this is an area of recent massive star
formation. Probable exciting sources capable of creating the compact HII region
are investigated. The 2MASS source 10380461-5846233 (MSX G286.3773-00.2563)
seems to be responsible for the formation of the HII region.Comment: Accepted in A&A. 11 pages, 10 Postscript figure
870 micron continuum observations of the bubble-shaped nebula Gum 31
We are presenting here a study of the cold dust in the infrared ring nebula
Gum 31. We aim at deriving the physical properties of the molecular gas and
dust associated with the nebula, and investigating its correlation with the
star formation in the region, that was probably triggered by the expansion of
the ionization front. We use 870 micron data obtained with LABOCA to map the
dust emission. The obtained LABOCA image was compared to archival IR,radio
continuum, and optical images. The 870 micron emission follows the 8 micron
(Spitzer), 250 micron, and 500 micron (Herschel) emission distributions showing
the classical morphology of a spherical shell. We use the 870 micron and 250
micron images to identify 60 dust clumps in the collected layers of molecular
gas using the Gaussclumps algorithm. The clumps have effective deconvolved
radii between 0.16 pc and 1.35 pc, masses between 70 Mo and 2800 Mo, and volume
densities between 1.1x10^3 cm^-3 and 2.04x10^5 cm^-3. The total mass of the
clumps is 37600 Mo. The dust temperature of the clumps is in the range from 21
K to 32 K, while inside the HII region reaches ~ 40 K. The clump mass
distribution is well-fitted by a power law dN/dlog(M/Mo) proportional to
M^(-alpha), with alpha=0.93+/-0.28. The slope differs from those obtained for
the stellar IMF in the solar neighborhood, suggesting that the clumps are not
direct progenitors of single stars/protostars. The mass-radius relationship for
the 41 clumps detected in the 870 microns emission shows that only 37% of them
lie in or above the high-mass star formation threshold, most of them having
candidate YSOs projected inside. A comparison of the dynamical age of the HII
region with the fragmentation time, allowed us to conclude that the collect and
collapse mechanism may be important for the star formation at the edge of Gum
31, although other processes may also be acting.Comment: 15 pages, 10 figures. Accepted for publication in A&
Molecular gas and star formation towards the IR dust bubble S24 and its environs
We present a multi-wavelength analysis of the infrared dust bubble S24, and
its environs, with the aim of investigating the characteristics of the
molecular gas and the interstellar dust linked to them, and analyzing the
evolutionary status of the young stellar objects (YSOs) identified there. Using
APEX data, we mapped the molecular emission in the CO(2-1), CO(2-1),
CO(2-1), and CO(3-2) lines in a region of about 5'x 5' in size
around the bubble. The cold dust distribution was analyzed using ATLASGAL and
Herschel images. Complementary IR and radio data were also used.The molecular
gas linked to the S24 bubble, G341.220-0.213, and G341.217-0.237 has velocities
between -48.0 km sec and -40.0 km sec. The gas distribution
reveals a shell-like molecular structure of 0.8 pc in radius bordering
the bubble. A cold dust counterpart of the shell is detected in the LABOCA and
Herschel images.The presence of extended emission at 24 m and radio
continuum emission inside the bubble indicates that the bubble is a compact HII
region. Part of the molecular gas bordering S24 coincides with the extended
infrared dust cloud SDC341.194-0.221. A cold molecular clump is present at the
interface between S24 and G341.217-0.237. As regards G341.220-0.213, the
presence of an arc-like molecular structure at the northern and eastern
sections of this IR source indicates that G341.220-0.213 is interacting with
the molecular gas. Several YSO candidates are found to be linked to the IR
extended sources, thus confirming their nature as active star-forming regions.
The total gas mass in the region and the H ambient density amount to 10300
M and 5900 cm, indicating that G341.220-0.213, G341.217-0.237,
and the S24 HII region are evolving in a high density medium. A triggering star
formation scenario is also investigated.Comment: 17 pages, 16 figures. Submitted to A&A. Revised according to the
referee repor
Mass loss rate determinations of southern OB stars
A sample of OB stars (eleven Of, one O and one B supergiant) has been
surveyed with the Australia Telescope Compact Array at 4.8 and 8.64 GHz with a
resolution of 2'' -- 4''. Five stars were detected; three of them have negative
spectral indices, consistent with non-thermal emission, and two have positive
indices. The thermal radiation from HD 150135 and HD 163181 can be explained as
coming from an optically thick ionized stellar wind. The non-thermal radiation
from CD-47 4551, HD 124314 and HD 150136 possibly comes from strong shocks in
the wind itself and/or in the wind colliding region if the stars have a massive
early-type companion. The percentage of non-thermal emitters among detected O
stars has increased up to ~50%. The Of star HD 124314 clearly shows flux
density variations. Mass loss rates (or upper limits) were derived for all the
observed stars and the results compared with non-radio measurements and
theoretical predictions.Comment: 11 pages, 5 figures, A&A accepte
Unveiling the molecular environment of the ring nebula RCW 78
We present a study of the ionized, neutral atomic, and molecular gas
associated with the ring nebula RCW 78 around the WR star HD 117688 (= WR 55).
We based our study on CO observations carried out with the SEST and NANTEN
telescopes. We report the detection of molecular gas with velocities in the
range -56 to -33 km/s. The CO emission is mainly connected to the western
section, with a total molecular mass of 1.3 x 10^5 solar masses. The analysis
of the HI gas distribution reveals the HI envelope of the molecular cloud,
while the radio continuum emission shows a ring-like structure, which is the
radio counterpart of the optical nebula. The gas distribution is compatible
with the western section of RCW 78 having originated in the photodissociation
and ionization of the molecular gas by HD 117688, and with the action of the
stellar winds of the WR star. A number of infrared point sources classified as
YSO candidates showed that stellar formation activity is present in the
molecular gas linked to the nebula. The fact that the expansion of the bubble
have triggered star formation in this region can not be discarded.Comment: 15 pages, 11 Postscript figures, to be published in A&
Molecular gas towards G18.8+1.8
This work aims at investigating the characteristics of the molecular gas
associated with the nebula G18.8+1.8, linked to the Wolf-Rayet star HD168206
(WR 113), and its relation to other components of its local interstellar
medium.
We carried out molecular observations of the 12CO(J=1-0) and (J=2-1) lines
with angular resolution of 44 arcsec and 22 arcsec using the SEST telescope.
Complementary NANTEN data of the 12CO(1-0) line were also used. The dust
emission was analyzed using Spitzer-IRAC images at 8.0 microns, and WISE data
at 3.4, 4.6, and 12.0 microns.
The SEST data allowed us to identify a molecular component (Cloud 3) having
velocities in the interval from ~ +30 to +36 km/s which is most probably linked
to the nebula. Morphological and kinematical properties suggest that Cloud 3
constitute a wind-blown molecular half-shell, which expands around WR113. The
ratio R_(2-1/1-0) and excitation temperatures indicate that the molecular gas
is being irradiated by strong UV radiation. The location of the inner optical
ring in the outer edge of Cloud 3 suggests that the stars SerOB2-1, -2, -3,
-63, and -64 are responsables for the ionization of Cloud 3 and the inner ring
nebula. A comparison between the spatial distribution of the molecular gas and
the PAH emission at 8 m indicates the existence of a PDR between the
ionized and the molecular gas.
A search for candidate young stellar objects (YSOs) in the region around
G18.8+1.8 based on available 2MASS, MSX, IRAS, and Spitzer-IRAC catalogs
resulted in the detection of about sixty sources, some of them projected onto
Cloud 3. Two small spots of clustered candidates YSOs are projected near the
outer border of Cloud 3, although a triggered stellar formation scenario is
doubtful.Comment: 12 pages, 9 figures, accepted for publication in A&
Multifrequency study of the ring nebula SG13
We investigate the morphology and kinematics of the interstellar medium in
the environs of the open cluster Mrk50, which includes the Wolf-Rayet star
WR157 and a number of early B-type stars. The analysis was performed using
radio continuum images at 408 and 1420 MHz, and HI 21cm line data taken from
the Canadian Galactic Plane Survey, molecular observations of the 12CO (J=1-0)
line at 115 GHz from the Five College Radio Astronomy Observatory and available
mid and far IR observations obtained with the MSX and IRAS satellites,
respectively. This study allowed identification of the radio continuum and
molecular counterpart of the ring nebula SG13, while no neutral atomic
structure was found to be associated. The nebula is also detected in images in
the mid and far infrared, showing the existence of dust well mixed with the
ionized gas. We estimate the main physical parameters of the material linked to
the nebula. The interstellar gas distribution in the environs of Mrk50 is
compatible with a stellar wind bubble created by the mass loss from WR157. The
distribution of young stellar object (YSO) candidates in the region shows that
stellar formation activity may be present in the molecular shell that encircles
the ring nebula.Comment: Accepted for publication in MNRAS, 13 pages, 11 figure
Choosing a similarity index to quantify gait data variability
Repeatability and reproducibility of joint kinematics can be assessed through Similarity Indices (SI) quantifying their pattern variability. These include: Coefficient of Multiple Correlation (CMC) [1]; Mean Absolute Variability (MAV) [2]; and Linear Fit Method (LFM) [3], which accounts for scaling (a1), offset (a0) and truthfulness of the linear model between the curves (R2). Among gait cycles, the intra-subject variability for a given joint is due to physiological fluctuations of the range of motion (ROM) and time shift. SIs might be differently affected for each joint, due to their different ROMs, and by marker positioning, leading to offsets among gait curves. This paper aims to investigate the effects that each of these sources of curve variability has on the SIs, in order to provide indications on which is the most suitable for the assessment of gait similarity
The radio and IR counterparts of the ring nebula around HD211564
We report the detection of the radio and infrared counterparts of the ring
nebula around the WN3(h) star HD211564 (WR152), located to the southwest of the
HII region Sh2132. Using radio continuum data from the Canadian Galactic Plane
Survey, we identified the radio counterparts of the two concentric rings, of
about 9' and 16' in radius, related to the star. After applying a filling
factor f = 0.05-0.12, electron densities and ionized masses are in the range
10-16 cm^-3 and 450-700 Mo, respectively. The analysis of the HI gas emission
distribution allowed the identification of 5900 Mo of neutral atomic gas with
velocities between -52 and -43 km/s probably linked to the nebula. The region
of the nebula is almost free of molecular gas. Only four small clumps were
detected, with a total molecular mass of 790 Mo. About 310 Mo are related to a
small infrared shell-like source linked to the inner ring, which is also
detected in the MSX band A. An IRAS YSO candidate is detected in coincidence
with the shell-like IR source.
We suggest that the optical nebula and its neutral counterparts originated
from the stellar winds from the WR star and its massive progenitor, and are
evolving in the envelope of a slowly expanding shell centered at (l,b) = (102
30, -0 50), of about 31 pc in radius. The bubble's energy conversion efficiency
is in agreement with recent numerical analysis and with observational results.Comment: 11 pages, 7 figures, accepted in MNRA
Sh2-205: II. Its quiescent stellar formation activity
We present a study of active stellar forming regions in the environs of the
HII region Sh2-205. The analysis is based on data obtained from point source
catalogues and images extracted from 2MASS, MSX, and IRAS surveys.
Complementary data are taken from CO survey. The identification of primary
candidates to stellar formation activity is made following colour criteria and
the correlation with molecular gas emission.
A number of stellar formation tracer candidates are projected on two
substructures of the HII region: SH148.83-0.67 and SH149.25-0.00. However, the
lack of molecular gas related to these structures casts doubts on the nature of
the sources. Additional infrared sources may be associated with the HI shell
centered at (l,b) = (149\degr 0\arcmin, -1\degr 30\arcmin).
The most striking active area was found in connection to the HII region LBN
148.11-0.45, where stellar formation candidates are projected onto molecular
gas. The analytical model to the "collect and collapse" process shows that
stellar formation activity could have been triggered by the expansion of this
HII region.Comment: Accepted for publication in MNRAS, 10 pages, 5 figures, 5 table
- …