Äîêóìåíò âçÿò èç êýøà ïîèñêîâîé ìàøèíû. Àäðåñ îðèãèíàëüíîãî äîêóìåíòà : http://star.arm.ac.uk/~ambn/367j.ps Äàòà èçìåíåíèÿ: Tue Dec 18 13:54:37 2001 Äàòà èíäåêñèðîâàíèÿ: Mon Oct 1 20:22:31 2012 Êîäèðîâêà: Ïîèñêîâûå ñëîâà: molecular cloud

A&A 539--545 (2001)
DOI: 10.1051/0004­6361:20010815
c ESO 2001
Astronomy
Astrophysics
High­resolution near­infrared study the deeply embedded
young stellar object S140 IRS
3
Preibisch
, Balega
, Schertl
1
, M. Smith
3
, Weigelt
1
1 Max­Planck­Institut Radioastronomie, Auf H˜ugel 53121 Bonn, Germany
2 Special Astrophysical Observatory, Nizhnij Arkhyz, Zelenchuk region, Karachai­Cherkesia 357147, Russia
3 Armagh Observatory, College Armagh BT61 9DG, Northern Ireland
Received Accepted June 2001
Abstract. explore structures immediately surrounding high­mass young stellar object
within L1204 molecular cloud. have obtained bispectrum speckle interferometric K­band image with
resolution 150 seeing­limited molecular hydrogen emission image Our speckle image
resolves sources,
a close binary separation 0.63
## third component
## away.
A rough assessment system stability suggests that IRS3 triple system unstable. Our speckle image
reveals extended di#use emission very complex morphology around IRS
3. extended di#use feature
north­east
of IRS
3 displays remarkable S­shaped structure. feature innermost
of
an
at
extended structure, which
is pointing towards
a bow­shock patch located
## IRS3. find
strong line emission associated feature, suggesting presence shocks, caused collision
outflowing material the ambient medium. S­shaped structure feature reproduced
model assuming
a precessing outflow Furthermore, several elongated features pointing away
a southern direction. Some
of features exhibit strong emission, demonstrating
3 drives outflows several directions.
words. techniques: interferometric stars: individual: S140 IRS3
-- formation stars: winds, outflows
Introduction
S140 region the south­east edge L1204
dark cloud, located
a distance #900 (Crampton
Fisher 1974). This cloud contains
a small cluster
highly obscured, optically invisible infrared sources, origi­
nally detected Rouan
et (1977). The observa­
tions Beichman
et (1979) revealed three individual
infrared sources region. brightest source
called the other sources
2 and IRS
3
located #17
## north
## IRS infrared
spectra these sources steeply between
10 and
(Lester 1986), demonstrating
deeply embedded young stellar objects associated with
Send o#print requests Preibisch,
e­mail: preib@mpifr­bonn.mpg.de
#
of results presented this paper based
observations obtained German­Spanish Astronomical
Centre, Calar operated Max­Planck­Institute
Astronomy, Heidelberg, jointly the Spanish National
Commission Astronomy. speckle observations col­
lected
at Special Astrophysical Observatory with
telecope.
circumstellar material. luminosity
of was
timated
L
#
3 â10
3 (Lester
et 1986), suggesting
it early B­type with mass roughly
8 M#
.
S140 IRS
a known source strong molecu­
outflows.
A bipolar outflow was detected
Blair (1978) studied more detail Minchin
et (1993). S140
1 lies
in middle between
blue­ and red­shifted outflow lobes. Since the other
infrared sources clearly not
cated the
of outflow, assumed
to source this outflow. Further molecular
emission maps the region presented example
Minchin (1993; CO), Hayashi
& Murata (1992;
CO), Wilner Welch (1994; HCO and SO). While
morphology
of molecular emission these
observations
is consistent with the
driving source outflows, spatial resolution
maps
is coarse exclude possibility that
2
or also contribute outflow activity. What
seems clear, however, that IRS
1 dominates
outflow activity.
previous studies, near­infrared images
of S140
region were obtained example Lenzen (1987),

Preibisch High­resolution near­infrared imaging S140
3
Harker (1997), Whitney
al. (1997),
(1998). These observations, however, seeing­
limited therefore not have resolution required
study the environment
( 1000 AU) individual
sources S140 IRS. paper represents
high­resolution study
of S140 star­forming
gion. paper (Schertl 2000) presented
a mas resolution bispectrum speckle interferometric
K­band image
of the central
3
â
3
## region around
1,
polarimetric measurements. This image showed
a bright elongated clumpy structure pointing away
a direction consistent with
of blue­shifted
outflow lobe. The centrosymmetric pattern high
larization
in feature suggests
it represents scat­
tered light from the central source We therefore
interpreted this feature clumpy inner
of
a
partially evacuated cavity circumstellar envelope
around which been excavated the south­
eastern wing strong outflow from the
paper (Weigelt 2001) presented bispectrum
speckle interferometry observations larger
13
##
field
of S140 IRS
1 and environment. addition
point sources, found several arc­like struc­
tures around The general appearance the di#use
structures suggests that they trace interaction
energetic outflows from
1 with circumstellar
terial. combination with molecular line emission maps
from literature, image provided evidence
presence flows four di#erent directions, apparently
originating from IRS
1.
The wealth interesting structures revealed
images
of motivation extending
high­resolution imaging study region
3.
Here present results our bispectrum speckle
terferometry observations
of
in K­band. We
obtained images light molecular hydrogen
emission line 2.12 Molecular hydrogen emission
is
a convenient tracer
of
to moderate­velocity shocks
(e.g. Smith 1993) will important information
about the outflow activity young stellar objects.
Observations data reduction
Bispectrum speckle imaging
speckle interferograms recorded with
6
m
SAO telescope and October 2000. The
tector
of speckle camera Rockwell HAWAII
array detector. observations were made through
a
K­band filter with center wavelength/FWHM bandwidth
µm/0.21 µm. was
posure frame 2216 speckle interfer­
ograms S140
3 and 5826 speckle interferograms
of
reference star 110410 obtained. The corre­
sponding e#ective telescope length was obtained
using K­band re­imaging optics designed di#raction­
limited speckle imaging SAO telescope.
The field­of­view 10.8
## â10.8 (400â400 pixel), seeing
was
## (FWHM).
Di#raction­limited images were reconstructed using
bispectrum speckle interferometry method (Weigelt
1977; Lohmann 1983; Hofmann
& Weigelt 1986). The
bispectrum
of frame consisted million elements.
The object power spectrum determined with the
speckle interferometry method (Labeyrie 1970). Speckle
interferograms unresolved single stars were recorded
just before object, served refer­
ence stars determination speckle transfer
function. resulting K­band image has
a resolution
2.2. Molecular hydrogen images
Conventional near­infrared images region
were obtained October Omega Prime
near­IR camera (Bizenberger
et 1998) Calar
Alto telescope. pixel scale Omega Prime
pixel, seeing
. Images were taken
through NB2122 filter,
a filter centered the
1-0 S(1)
H
2 molecule
at µm, and
through broad­band
K filter (1.944-2.292 µm). each
di#erent dither positions,
a series images with
exposure NB2122 filter and images
with 1.677
s exposure time
K filter were taken.
The total integration time therefore the
NB2122 filter and 1.677
in
# filter. Standard data
reduction techniques were used subtract, field,
and mosaic data McCaughrean 1994). Then,
NB2122 filter image was carefully aligned with
K
filter image several point sources outer parts
image. Finally,
K filter image was subtracted from
NB2122 filter image order create continuum­
subtracted
2 emission line image.
Results
Fig. present images S140 IRS most
important features revealed speckle image
follows:
IRS
3 clearly resolved three point sources. The
angular separation brightest components, which
IRS (627 mas with
position angle
of
85
#
is (1.2±0.2) mag fainter
than IRS K­band. third component,
located (1306 south
3a
a position
angle 172
#
#
. (2.5
± mag fainter than
IRS several bright and extended features
of di#use emission
pointing from IRS towards the south­east. These
features are marked letters Fig.
The direction innermost brightest feature has
position angle #170
. Feature
a position angle
#120
. Feature
is
a strongly curved di#use
emission south 3a;

Preibisch High­resolution near­infrared imaging
of
#
###
#
#
#
####
##
#########
Fig. Images
of images north left; view
##
â
. Upper Left:
Color representation
of mas resolution bispectrum speckle K­band image
of IRS
3. areas mag fainter
than intensity. Upper Right: Greyscale representation K­band speckle image with annotation features
discussed text. The dashed­lined arrow right edge image indicates direction towards S140
Lower Left: Greyscale representation K­band speckle image; black contour lines show
a smoothed representation
this image order pronounce structure faintest di#use emission features. The thick contours show
continuum­subtracted emission image. Contours drawn times the noise level
above median
in continuum­subtracted image. The estimated accuracy
of alignment between image and
speckle image #0.2
##
. Lower Right: Greyscale
+ contour representation
of K­band speckle image reconstructed
a
reduced resolution mas order better show fainter details. shows model curve computed
from precessing model
patch
of apparently di#use emission
is found
#0.5 north­east IRS another (E) located
south­east IRS
extended di#use emission
is found north­east
IRS feature displays
a remarkable S­shaped
structure lower­right).
Comparison
of speckle image with
H emission
image (Fig.
1 yields following results:
. Strong extended
2 emission found north­
eastern
of image, coinciding with feature
speckle image.

Preibisch High­resolution near­infrared imaging S140
3
. Another peak
of
H emission
is found south­east
of
3b. coincides roughly feature
B extends
southern feature
Interpretation
Feature
4.1.1. Scattered light and shock emission
Feature does show strong
H line emission,
is strongly polarized. polarization pattern
feature K­band polarimetric images
S region presented
by Whitney (1997) and
(1998) suggests scattered light origi­
nating Comparison
H
# fluxes
integrated over
## aperture centered
2 emis­
shows that #20%
2 line emission,
while #80%
of flux
is continuum emission. Feature
F
probably represents
a denser region environment
3, where light from reflected
rection, causing observed high degree
of polarization,
where outflowing material collides denser
causing strong shocks giving
to observed
2 emission.
4.1.2. precessing outflow?
Feature related
to
a much larger, strongly elongated
structure pointing away from
3 north­eastern
rection seen very
in the deep K­band
complex presented Yao (1998;
their Yao's image, structure clearly
traced more than
## away from
3 with position
angle #64
#
. Our feature
is innermost bright­
part elongated nebulosity. elongated
nebulosity can seen well the deep K­band
image
of S140 region presented Hodapp (1994).
Interestingly, image shows
a di#use patch emis­
a bow­shock shape, located
## north­east
position angle #68
#
. appears very likely
that bow­shock patch
is related elongated
emission near IRS
3 and feature
F.
Our result feature
F
is associated with strong
molecular hydrogen shock emission
in combination
presence bow­shock feature further away
strongly suggests that material
is flowing away from IRS
3
north­eastern direction. Our speckle image allows
resolve detailed morphology innermost
feature reveals
a remarkable wiggly S­shaped
structure. This
in speckle image recon­
structed with reduced resolution (Fig. lower right).
It
is
very tempting speculate that feature traces
cessing outflow originating from Therefore,
compare general structure this feature
image with precession model described Eisl˜o#el
(1996). model, the trajectory
a precessing
projected the given formula
#
,
x
,
y
) cos
# (1)
sin(2#l/#
#
)
#
0
y
0
where
#
is precession amplitude, precession
length,
0 the initial phase
at source, rotation
angle the the plane sky,
l distance
from the source position
x
,
0
. The model curve shown
Fig. (lower image) obtained values
0.25,
=
,
0 190
#
, and
#
. curve
traces observed morphology
of feature remarkably
well. The parameters the model curve shown Fig.
yield precession length scale #4000 AU. Assuming
flow velocity #100--200 km
s
,
as typically found
young stellar objects Eisl˜o#el
et 2000; Richer
2000), corresponding precession period would
#100--200
If our interpretation correct, next question would
causes the precession outflow? possi­
explanation might
be outflow originates from
member close binary system where the rotational
axis star driving outflow misaligned with the
orbital plane the binary. their theoretical study
non­coplanar binary systems, Bate (2000) found that
rotation axis star (and therefore out­
flow) precesses with
a period
of binary pe­
riods.
In case 3a, where assume
a mass
#8M# (Lester 1986), model would require
binary
a separation
of #6--9 150 mas
(#135 resolution
of image, would clearly not
able resolve such
a close binary. Therefore, ob­
servations inconsistent with hypothesis
precessing outflow originating from non­coplanar binary
system. Finally,
we our precessing outflow model
course the possible explanation shape
feature The observed K­band morphology might also
caused projection e#ects when looking clumpy
structure, inhomogeneous extinction. Another po­
tential problem with precessing outflow model might
counterpart this
outflow, which would
be expected
a position angle
245
#
. However, this might simply due inclina­
tion outflow with respect the line­of­sight:
outflow perpendicular
to line­of­sight
but tilted direction, expected counterpart would
point away
us therefore could well hidden
circumstellar extinction.
4.2. Di#use emission south
Features and seem point away from 3a.
One possible interpretation
of these features may that
see scattered light from limb­brightened walls
cavity circumstellar envelope around IRS sim­
to extended emission found south
ofPreibisch High­resolution near­infrared imaging
of
(cf. Schertl
et 2000). Another possibility would that
these features either represent outflowing material that
they trace shock­heated regions
in which outflowing ma­
terial collides ambient medium. second possi­
bility
is supported find strong
H
emission coinciding with feature indicating the pres­
ence shocked material.
In case, range
position angles features and #180
#
might indicate
a poorly collimated outflow.
Feature
C displays
a remarkable curved shape:
it seems
at
in
a southern direction strongly
turns
to east. From origin
of this feature
direction changes nearly
# This remarkable cur­
vature could indicative compression from west­
ern direction. Interestingly, this direction
which S140
1 found, most luminous source
the S140 cluster.
is expected strongly a#ect
environment several mechanisms. Firstly,
the source strong outflow activity several directions
(cf. Weigelt 2001). Secondly, from radio observations
region, Evans
et (1989) concluded that
most radio emission from
1 probably arises from
optically region, while some fraction originates
from collimated stellar wind. Both mechanisms,
expanding region
as
a strong stellar wind,
can expected
of considerable influence am­
bient molecular cloud material. Therefore, seems
quite plausible that
1 compresses IRS
distorting and bending the material observed fea­
ture
In context
it
is interesting Bally
Reipurth (2001) reported discovery several with
strongly curved shapes. authors explana­
tions bent bending could caused side­
wards compression, either other outflows
or
by irra­
diation from massive stars. Alternatively, bending
may indicate source
is ejected from their
cluster. Masciadri Raga (2001) have recently presented
three­dimensional gas­dynamical models interaction
between outflowing material from young stellar object
and
a wind perpendicular outflow direction. These
models can reproduce curved shapes observed
Bally Reipurth (2001) very well
markable similarity morphology feature
4.3. Features
E
Our image reveals two compact features,
Despite point­source appearance, find that
these features clearly more extended than
pected point source. Feature could connected
cannot exclude
a chance projection.
Feature appears isolated and shows strong
2 emission. This suggests
it may related
outflow system south
of Proper motion measure­
ments these features, interpreted ballistic motions,
could soon determine
if these features associated with
outflows from
of infrared sources.
5. the IRS
3 triple system
images show consists least) three
point sources. course, with data hand cannot
these three point sources are physically
lated actually constitute
a triple system; they might
perhaps chance projection. However,
image show any other point sources
field­of­view allows
us least
roughly, evaluate likelihood
of
a chance projection.
three point sources unrelated objects, prob­
ability find three within
##
of other would
P
=
# #(1.3
##
2
(10.8
##
)
# 0.00207.
It therefore reasonable
assume the three sources related consti­
triple system.
interesting make assessment how stable
system rather general result about triple
is that they stable only su#ciently
hierarchical. Eggleton Kiseleva (1995) derived
lowing relation between minimum initial ratio
0
periastron distance
of the outer orbit apastron
distance inner
a stable triple system:
Y min
#
1
1
+
q
q
1
q
1
where
in
=
M
b +M
b
) /M
c and
denotes stellar masses
of individual components.
Lacking detailed information about orbits
of
components, assume that system coplanar
the orbits circular. Using projected separa­
of components
in image estimates their
orbital radii,
0
ac 1306/627
#
Estimates masses the components
derived
in following
we assume
a mass
a primary component
3a based
estimate
of luminosity (Lester 1986). From
estimate masses
of other
components from their K­band magnitude di#erences
M
5
, and
c 3--4
. Based these mass
estimates (and the above estimate the orbital radii),
plotted parameters
of Fig.
2 find that,
allowing generously large uncertainties
parameters, IRS
3 triple system appears
to
stable.
a recent paper, Reipurth (2001) postulated that
dynamical decay triple higher order multiple systems
lead strong outflow activity: system breaks
ejects lightest member, massive disk trunca­
and accompanying large­scale accretion one
remaining stars causes
a burst
of outflow activity. This
model could provide good explanation IRS
3
faintest and therefore probably lightest
component system, being ejected, whereas
is undergoing
a phase strong outflow activity.

Preibisch High­resolution near­infrared imaging S140
3
2. stability criterion triple systems (Eq.
is
shown the thick solid thin dotted indicate
range
of variations resulting the uncertainty
q
.
Systems above the boundary stable, systems below
boundary unstable. estimate
of parameters
IRS
3 system
is shown solid error bars.
assume
a factor
of
2 uncertainty #ac/#ab
,
uncertainties mass estimates.
unclear how scenario would
a#ected IRS actually close binary,
posed the section explain precession
outflow. this case, would with quadruple
tem, the kinematic would much more complicated.
Nevertheless, scenario would probably work.
Another interesting aspect consider this context
is
corresponding timescale.
If stars actually
ejected from system, then the rather compact config­
uration system, stellar separations more
than #1200 suggests kinematic interaction
causing ejection took place not long probably
more than thousand years would imply
that outflow activity only started very recently.
This might explain why, large­scale outflow
detected from IRS
3: outflow from IRS
3
is
probably
so young that swept enough
material detectable
in molecular maps.
future observations hope
to
to determine
proper motions individual objects IRS
3.
provide with important information dynam­
IRS
3 system and show whether the ejection
nario applicable system.
Conclusions
The main results
of high­resolution near­infrared
imaging study S140 IRS
3 can summarized fol­
lows: resolved triple system sepa­
rations 0.63
## (#560 AU) and
## (#1200 AU).
rough evaluation the system parameters suggests
the triple system most likely unstable.
image reveals remarkable S­shaped di#use emis­
feature north­east IRS which inner­
of
a strongly elongated extended feature
pointing towards
a bow­shock
90 north­east 3a.
feature
be associated with strong
H
emission. morphology well explained
model
a precessing outflow. The precession
could caused
a close binary system which the
the outflow source
is mis­aligned with
plane.
Some parts bright di#use emission south
of associated strong
2 emission
therefore
to outflowing material. One
features
is strongly curved; could represent
bended
or outflow. The bending may explained
as compression the material region
west, caused strong outflow source
Acknowledgements. would
to thank Calar Alto
sta# their support during observations, Thomas Stanke
assistance reduction
of Omega ref­
eree Nagata report which helped improve this
paper.
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