552 research outputs found
The Kinematics of HH 34 from HST Images with a Nine-year Time Baseline
We study archival HST [S II] 6716+30 and Hα images of the HH 34 outflow, taken in 1998.71 and in 2007.83. The ~9 yr time baseline and the high angular resolution of these observations allow us to carry out a detailed proper-motion study. We determine the proper motions of the substructure of the HH 34S bow shock (from the [S II] and Hα frames) and of the aligned knots within ~30'' from the outflow source (only from the [S II] frames). We find that the present-day motions of the knots along the HH 34 jet are approximately ballistic, and that these motions directly imply the formation of a major mass concentration in ~900 yr, at a position similar to the one of the present-day HH 34S bow shock. In other words, we find that the knots along the HH 34 jet will merge to form a more massive structure, possibly resembling HH 34S
Implementasi Peraturan Daerah No 14 Tahun 2011 Tentang Rencana Tata Ruang Dan Wilayah Kota Semarang Di Kecamatan Tembalang
Flooding in the City of Semarang derived from two sources that is from the sea and from the top of semarang. Regional Semarang over are prioritized for this flood catchment area is established building houses, simple and elite houses. One of the effort from the City Government Semarang by the application of Local Regulation no. 14 years 2011 about spatial plans and the areas of the City of Semarang. This research was conducted in DKTP Semarang as officer of Semarang's Government. Section of Regional planing and supervision as stakeholder of the Implementation Of The Local Regulation No 14 2011. This Research is based on the rise of the construction of housing in the area of the City of Semarang over especially in Kecamatan Tembalang is not in reflect with RTRW of Semarang City. The purpose of this research is described and analyze Implementation Of Regulation No 14 2011 and analyze what factors which influence the Implementation Of Regulation No 14 2011 the City of Semarang. The results of the study showed that in its implementation there are a number of things can restrickting the implementation of this local regulations. This is due to a lack of human resources , obscurity standards and target of this policy and the less participation of the community and private sectors caused by social and economic conditions. Recommendations from this research are to recruit of human resources to handling the problem , the implementation of RDRTK as a continuity of Semarang's RTRW , and listen to public aspiration
Optical and Near Infrared Study of the Cepheus E outflow, a very low excitation object
We present images and spectra of the Cepheus E (Cep E) region at both optical
and infrared wavelengths. Only the brightest region of the southern lobe of the
Cep E outflow reveals optical emission, suggesting that the extinction close to
the outflow source plays an important r\^ole in the observed difference between
the optical and IR morphologies. Cep E is a unique object since it provides a
link between the spectroscopic properties of the optical Herbig-Haro (HH)
objects and those of deeply embedded outflows.Comment: Accepted Astron. J., 8 files: paper, tables plus 6 figure
Millimeter- and Submillimeter-Wave Observations of the OMC-2/3 Region. II. Observational Evidence for Outflow-Triggered Star Formation in the OMC-2 FIR 3/4 Region
We have carried out the observations of the OMC-2 FIR 3/4 region with the NMA
and ASTE in the HCO (1--0), CO (3--2, 1--0), SiO (=0,
=2--1), CS (2--1), and CHOH (=7--6) lines and in the 3.3 mm
continuum emission. Our NMA observations in the HCO emission have
revealed 0.07 pc-scale dense gas associated with FIR 4. The CO
(3--2,1--0) emission shows high-velocity blue and red shifted components at the
both north-east and south-west of FIR 3, suggesting a molecular outflow nearly
along the plane of the sky driven by FIR 3. The SiO and the CHOH emission
are detected around the interface between the outflow and the dense gas.
Furthermore, the CO (1--0) emission shows an L-shaped structure in the
P-V diagram. These results imply presence of the shock due to the interaction
between the molecular outflow driven by FIR 3 and the dense gas associated with
FIR 4. Moreover, our high angular-resolution observations of FIR 4 in the 3.3
mm continuum emission have first found that FIR 4 consists of eleven dusty
cores. The separation among these cores is on the same order of the Jeans
length, suggesting that the fragmentation into these cores has been caused by
the gravitational instability. The time scale of the fragmentation is similar
to the time scale of the interaction between the molecular outflow and the
dense gas. We suggest that the interaction between the molecular outflow from
FIR 3 and the dense gas associated with FIR 4 triggered the fragmentation into
these dusty cores, and hence the next generation the cluster formation.Comment: 13 pages, 9 figures. Accepted by Ap
The complex structure of HH 110 as revealed from Integral Field Spectroscopy
HH 110 is a rather peculiar Herbig-Haro object in Orion that originates due
to the deflection of another jet (HH 270) by a dense molecular clump, instead
of being directly ejected from a young stellar object. Here we present new
results on the kinematics and physical conditions of HH 110 based on Integral
Field Spectroscopy. The 3D spectral data cover the whole outflow extent (~4.5
arcmin, ~0.6 pc at a distance of 460 pc) in the spectral range 6500-7000 \AA.
We built emission-line intensity maps of H, [NII] and [SII] and of
their radial velocity channels. Furthermore, we analysed the spatial
distribution of the excitation and electron density from [NII]/H,
[SII]/H, and [SII] 6716/6731 integrated line-ratio maps, as well as
their behaviour as a function of velocity, from line-ratio channel maps. Our
results fully reproduce the morphology and kinematics obtained from previous
imaging and long-slit data. In addition, the IFS data revealed, for the first
time, the complex spatial distribution of the physical conditions (excitation
and density) in the whole jet, and their behaviour as a function of the
kinematics. The results here derived give further support to the more recent
model simulations that involve deflection of a pulsed jet propagating in an
inhomogeneous ambient medium. The IFS data give richer information than that
provided by current model simulations or laboratory jet experiments. Hence,
they could provide valuable clues to constrain the space parameters in future
theoretical works.Comment: 12 pages, 15 figures Accepted in MNRA
On the Influence of Magnetic Fields on the Structure of Protostellar Jets
We here present the first results of fully three-dimensional (3-D) MHD
simulations of radiative cooling pulsed (time-variable) jets for a set of
parameters which are suitable for protostellar outflows. Considering different
initial magnetic field topologies in approximate with the
thermal gas, i.e., (i) a longitudinal, and (ii) a helical field, both of which
permeating the jet and the ambient medium; and (iii) a purely toroidal field
permeating only the jet, we find that the overall morphology of the pulsed jet
is not very much affected by the presence of the different magnetic field
geometries in comparison to a nonmagnetic calculation. Instead, the magnetic
fields tend to affect essentially the detailed structure and emission
properties behind the shocks at the head and at the pulse-induced internal
knots, particularly for the helical and toroidal geometries. In these cases, we
find, for example, that the emissivity behind the internal knots can
be about three to four times larger than that of the purely hydrodynamical jet.
We also find that some features, like the nose cones that often develop at the
jet head in 2-D calculations involving toroidal magnetic fields, are smoothed
out or absent in the 3-D calculations.Comment: 13 pages, 3 figures, Accepted by ApJ Letters after minor corrections
(for high resolution figures, see http://www.iagusp.usp.br/~adriano/h.tar
Can Protostellar Jets Drive Supersonic Turbulence in Molecular Clouds?
Jets and outflows from young stellar objects are proposed candidates to drive
supersonic turbulence in molecular clouds. Here, we present the results from
multi-dimensional jet simulations where we investigate in detail the energy and
momentum deposition from jets into their surrounding environment and quantify
the character of the excited turbulence with velocity probability density
functions. Our study include jet--clump interaction, transient jets, and
magnetised jets. We find that collimated supersonic jets do not excite
supersonic motions far from the vicinity of the jet. Supersonic fluctuations
are damped quickly and do not spread into the parent cloud. Instead subsonic,
non-compressional modes occupy most of the excited volume. This is a generic
feature which can not be fully circumvented by overdense jets or magnetic
fields. Nevertheless, jets are able to leave strong imprints in their cloud
structure and can disrupt dense clumps. Our results question the ability of
collimated jets to sustain supersonic turbulence in molecular clouds.Comment: 33 pages, 18 figures, accepted by ApJ, version with high resolution
figures at:
http://www.ita.uni-heidelberg.de/~banerjee/publications/jet_paper.pd
Generation of radiative knots in a randomly pulsed protostellar jet I. Dynamics and energetics
HH objects are characterized by a complex knotty morphology detected mainly
along the axis of protostellar jets in a wide range of bands. Evidence of
interactions between knots formed in different epochs have been found,
suggesting that jets may result from the ejection of plasma blobs from the
source. We aim at investigating the physical mechanism leading to the irregular
knotty structure observed in jets in different bands and the complex
interactions occurring among blobs of plasma ejected from the stellar source.
We perform 2D axisymmetric HD simulations of a randomly ejected pulsed jet. The
jet consists of a train of blobs which ram with supersonic speed into the
ambient medium. The initial random velocity of each blob follows an exponential
distribution. We explore the ejection rate parameter to derive constraints on
the physical properties of protostellar jets by comparison of model results
with observations. Our model takes into account radiative losses and thermal
conduction. We find that the mutual interactions of blobs ejected at different
epochs and with different speed lead to a variety of plasma components not
described by current models. The main features characterizing the random pulsed
jet scenario are: single high speed knots, showing a measurable proper motion
in nice agreement with observations; irregular chains of knots aligned along
the jet axis and possibly interacting with each other; reverse shocks
interacting with outgoing knots; oblique shocks produced by the reflection of
shocks at the jet cocoon. All these structures concur to determine the
morphology of the jet in different bands. We also find that the thermal
conduction plays a crucial role in damping out HD instabilities that would
develop within the cocoon and that contribute to the jet breaking.Comment: 10 pages, 10 figures, accepted for publication in A&
A Micro Molecular Bipolar Outflow From HL Tau
We present detailed geometry and kinematics of the inner outflow toward HL
Tau observed using Near Infrared Integral Field Spectograph (NIFS) at the
Gemini-North 8-m Observatory. We analyzed H2 2.122 um emission and [Fe II]
1.644 um line emission as well as the adjacent continuum observed at a <0".2
resolution. The H2 emission shows (1) a bubble-like geometry to the northeast
of the star, as briefly reported in the previous paper, and (2) faint emission
in the southwest counterflow, which has been revealed through careful analysis.
The emission on both sides of the star show an arc 1".0 away from the star,
exhibiting a bipolar symmetry. Different brightness and morphologies in the
northeast and southwest flows are attributed to absorption and obscuration of
the latter by a flattened envelope and a circumstellar disk. The H2 emission
shows a remarkably different morphology from the collimated jet seen in [Fe II]
emission. The positions of some features coincide with scattering continuum,
indicating that these are associated with cavities in the dusty envelope. Such
properties are similar to millimeter CO outflows, although the spatial scale of
the H2 outflow in our image (~150 AU) is strikingly smaller than the mm
outflows, which often extend over 1000-10000 AU scales. The position-velocity
diagram of the H2 and [Fe II] emission do not show any evidence for kinematic
interaction between these flows. All results described above support the
scenario that the jet is surrounded by an unseen wide-angled wind, which
interacts with the ambient gas and produce the bipolar cavity and shocked H2
emission.Comment: 13 pages, 4 figures, accepted for publication in ApJ
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