105 research outputs found
Discovering a misaligned CO outflow related to the red MSX source G034.5964-01.0292
The red MSX source G034.5964-01.0292 (MSXG34), catalogued as a massive YSO,
was observed in molecular lines with the aim of discover and study molecular
outflows. We mapped a region of 3'x3' centered at MSXG34 using the Atacama
Submillimeter Telescope Experiment in the 12CO J=3-2 and HCO+ J=4-3 lines with
an angular and spectral resolution of 22" and 0.11 km/s, respectively.
Additionally, public 13CO J=1-0 and near-IR UKIDSS data obtained from the
Galactic Ring Survey and the WFCAM Sciencie Archive, respectively, were
analyzed. We found that the 12CO spectra towards the YSO present a
self-absorption dip, as it is usual in star forming regions, and spectral wings
evidencing outflow activity. The HCO+ was detected only towards the MSXG34
position at v_LSR ~ 14.2 km/s, in coincidence with the 12CO absorption dip and
approximately with the velocity of previous ammonia observations. HCO+ and NH3
are known to be enhanced in molecular outflows. Analyzing the spectral wings of
the 12CO line, we discovered misaligned red- and blue-shifted molecular
outflows associated with MSXG34. The near-IR emission shows a cone-like shape
nebulosity composed by two arc-like features related to the YSO, which can be
due to a cavity cleared in the circumstellar material by a precessing jet. This
can explain the misalignment in the molecular outflows. From the analysis of
the 13CO J=1--0 data we suggest that the YSO is very likely related to a
molecular clump ranging between 10 and 14 km/s. This suggests that MSXG34, with
an associated central velocity of about 14 km/s, may be located in the
background of this clump. Thus, the blue-shifted outflow is probably deflected
by the interaction with dense gas along the line of sight.Comment: Accepted in A&A June 10, 201
Study of the luminous blue variable star candidate G26.47+0.02 and its environment
Aims. The luminous blue variable (LBV) stars are peculiar very massive stars. The study of these stellar objects and their surroundings is important for understanding the evolution of massive stars and its effects on the interstellar medium. We study the LBV star candidate G26.47+0.02.
Methods. Using several large-scale surveys in different frequencies we performed a multiwavelength study of G26.47+0.02 and its surroundings.
Results. We found a molecular shell (seen in the 13CO J = 1-0 line) that partially surrounds the mid-infrared nebula of G26.47+0.02, which suggests an interaction between the strong stellar winds and the molecular gas. From the HI absorption and the molecular gas study we conclude that G26.47+0.02 is located at a distance of ~4.8 kpc. The radio continuum analysis shows both thermal and non-thermal emission toward this LBV candidate, pointing to wind-wind collision shocks from a binary system. This hypothesis is supported by a search of near-IR sources and the Chandra X-ray analysis. Additional multiwavelength and long-term observations are needed to detect some possible variable behavior, and if that is found, to confirm the binary nature of the system.Facultad de Ciencias AstronĂłmicas y GeofĂsicasInstituto Argentino de RadioastronomĂ
The HII region G35.673-00.847: another case of triggered star formation?
As part of a systematic study that we are performing with the aim to increase
the observational evidence of triggered star formation in the surroundings of
HII regions, we analyze the ISM around the HII region G35.673-00.847, a poorly
studied source. Using data from large-scale surveys: Two Micron All Sky Survey,
Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE), MIPSGAL,
Galactic Ring Survey (GRS), VLA Galactic Plane Survey (VGPS), and NRAO VLA Sky
Survey (NVSS) we performed a multiwavelength study of G35.673-00.847 and its
surroundings. The mid IR emission, shows that G35.673-00.847 has an almost
semi-ring like shape with a cut towards the galactic west. The radius of this
semi-ring is about 1.5' (~1.6 pc, at the distance of ~3.7 kpc). The distance
was estimated from an HI absorption study and from the analysis of the
molecular gas. Indeed, we find a molecular shell composed by several clumps
distributed around the HII region, suggesting that its expansion is collecting
the surrounding material. We find several YSO candidates over the molecular
shell. Finally, comparing the HII region dynamical age and the fragmentation
time of the molecular shell, we discard the collect and collapse as the
mechanism responsible for the YSOs formation, suggesting other processes such
as radiative driven implosion and/or small-scale Jeans gravitational
instabilities.Comment: Accepted for publication in A&A, 18 October 2010. Some figures were
degraded to reduce file siz
A new study towards PSR J1826-1334 and PSR J1826-1256 in the region of HESS J1825-137 and HESS J1826-130
Aims. The goal of this paper is to detect synchrotron emission from the relic
electrons of the crushed pulsar wind nebula (PWN) HESS J1825-137 and to
investigate the origin of the -ray emission from HESS J1826-130.\\
Methods. The study of HESS J1825-137 was carried out on the basis of new radio
observations centred at the position of PSR J1826-1334 performed with the Karl
G. Jansky Very Large Array at 1.4 GHz in configurations B and C. To investigate
the nature of HESS J1826-130, we reprocessed unpublished archival data obtained
with XMM-Newton.\\ Results. The new radio continuum image towards PSR
J1826-1334 reveals a bright radio source, with the pulsar located in its
centre, which suggests that this feature could be the radio counterpart of the
compact component of the PWN detected at high energy. The new 1.4 GHz radio
data do not reveal emission with an extension comparable with that observed in
-rays for the HESS J1825-137 source. On the other hand, the XMM-Newton
study of the region including PSR J1826-1256 reveals an elongated non-thermal
X-ray emitting nebula with the pulsar located in the northern border and a tail
towards the peak of the very high energy source. The spectrum is characterized
by a power law with a photon index going from 1.6 around the pulsar to 2.7 in
the borders of the nebula, a behaviour consistent with synchrotron cooling of
electrons. From our X-ray analysis we propose that HESS J1826-130 is likely
produced by the PWN powered by PSR J1826-1256 via the inverse Compton
mechanism.Comment: 9 pages, 5 figures, 4 tables. Accepted for publication in the
Astronomy & Astrophysics Journal. The quality of the images has been degrade
The molecular environment of the pillar-like features in the HII region G46.5-0.2
At the interface of HII regions and molecular gas peculiar structures appear,
some of them with pillar-like shapes. Understanding their origin is important
for characterizing triggered star formation and the impact of massive stars on
the interstellar medium. In order to study the molecular environment and the
influence of the radiation on two pillar-like features related to the HII
region G46.5-0.2, we performed molecular line observations with the Atacama
Submillimeter Telescope Experiment, and spectroscopic optical observations with
the Isaac Newton Telescope. From the optical observations we identified the
star that is exciting the HII region as a spectral type O4-6. The molecular
data allowed us to study the structure of the pillars and a HCO+ cloud lying
between them. In this HCO+ cloud, which have not any well defined 12CO
counterpart, we found direct evidence of star formation: two molecular outflows
and two associated near-IR nebulosities. The outflows axis orientation is
perpendicular to the direction of the radiation flow from the HII region.
Several Class I sources are also embedded in this HCO+ cloud, showing that it
is usual that the YSOs form large associations occupying a cavity bounded by
pillars. On the other hand, it was confirmed that the RDI process is not
occurring in one of the pillar tips.Comment: Accepted in MNRAS (2017 June 13
Study of the luminous blue variable star candidate G26.47+0.02 and its environment
The luminous blue variable (LBV) stars are peculiar very massive stars. The
study of these stellar objects and their surroundings is important for
understanding the evolution of massive stars and its effects on the
interstellar medium. We study the LBV star candidate G26.47+0.02. Using several
large-scale surveys in different frequencies we performed a multiwavelength
study of G26.47+0.02 and its surroundings. We found a molecular shell (seen in
the 13CO J=1-0 line) that partially surrounds the mid-infrared nebula of
G26.47+0.02, which suggests an interaction between the strong stellar winds and
the molecular gas. From the HI absorption and the molecular gas study we
conclude that G26.47+0.02 is located at a distance of ~4.8 kpc. The radio
continuum analysis shows a both thermal and non-thermal emission toward this
LBV candidate, pointing to wind-wind collision shocks from a binary system.
This hypothesis is supported by a search of near-IR sources and the Chandra
X-ray analysis. Additional multiwavelength and long-term observations are
needed to detect some possible variable behavior, and if that is found, to
confirm the binary nature of the system.Comment: accepted in A&A 01/05/201
HII region G46.5-0.2: the interplay between ionizing radiation, molecular gas and star formation
HII regions are particularly interesting because they can generate dense
layers of gas and dust, elongated columns or pillars of gas pointing towards
the ionizing sources, and cometary globules of dense gas, where triggered star
formation can occur. Understanding the interplay between the ionizing radiation
and the dense surrounding gas is very important to explain the origin of these
peculiar structures, and hence to characterize triggered star formation.
G46.5-0.2 (G46), a poorly studied galactic HII region located at about 4 kpc,
is an excellent target to perform this kind of studies. Using public molecular
data extracted from the Galactic Ring Survey (13CO J=1-0) and from the James
Clerk Maxwell Telescope data archive (12CO, 13CO, C18O J=3-2, HCO+ and HCN
J=4-3), and infrared data from the GLIMPSE and MIPSGAL surveys, we perform a
complete study of G46, its molecular environment and the young stellar objects
placed around it. We found that G46, probably excited by an O7V star, is
located close to the edge of the GRSMC G046.34-00.21 molecular cloud. It
presents a horse-shoe morphology opening in direction of the cloud. We observed
a filamentary structure in the molecular gas likely related to G46 and not
considerable molecular emission towards its open border. We found that about
10' towards the southwest of G46 there are some pillar-like features, shining
at 8 um and pointing towards the HII region open border. We propose that the
pillar-like features were carved and sculpted by the ionizing flux from G46. We
found several young stellar objects likely embedded in the molecular cloud
grouped in two main concentrations: one, closer to the G46 open border
consisting of Class II type sources, and other one mostly composed by Class I
type YSOs located just ahead the pillars-like features, strongly suggesting an
age gradient in the YSOs distribution.Comment: Accepted for publication in The Astronomical Journal (April 14,
2015). Some figures were degraded to reduce file siz
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