Issue |
A&A
Volume 507, Number 3, December I 2009
|
|
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Page(s) | 1425 - 1442 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361/200912507 | |
Published online | 27 August 2009 |
A&A 507, 1425-1442 (2009)
APEX-CHAMP+ high-J CO observations of low-mass young stellar objects
II. Distribution and origin of warm
molecular gas![[*]](/icons/foot_motif.png)
T. A. van Kempen1,2 - E. F. van Dishoeck1,3 - R. Güsten4 - L. E. Kristensen1 - P. Schilke4 - M. R. Hogerheijde1 - W. Boland1,5 - K. M. Menten4 - F. Wyrowski4
1 - Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden,
The Netherlands
2 - Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
3 - Max-Planck Institut für Extraterrestrische Physik (MPE),
Giessenbachstr. 1, 85748 Garching, Germany
4 - Max Planck Institut für Radioastronomie, Auf dem Hügel 69, 53121
Bonn, Germany
5 - Nederlandse Onderzoeksschool Voor Astronomie (NOVA), PO Box 9513,
2300 RA Leiden, The Netherlands
6 - SRON Netherlands Institute for Space Research, PO Box 800, 9700 AV
Groningen, The Netherlands
Received 15 May 2009 / Accepted 18 August 2009
Abstract
Context. The origin and heating mechanisms of warm
(50<T< 200 K) molecular gas
in low-mass young stellar objects (YSOs) are strongly debated. Both
passive heating of the inner collapsing envelope by the protostellar
luminosity as well as active heating by shocks and by UV associated
with the outflows or accretion have been proposed. Most data so far
have focussed on the colder gas component.
Aims. We aim to characterize the warm gas within
protosteller objects, and disentangle contributions from the (inner)
envelope, bipolar outflows and the quiescent cloud.
Methods. High-J CO maps (12CO
J=6-5 and 7-6) of the immediate surroundings (up to
10 000 AU) of eight low-mass YSOs are obtained with
the CHAMP+ 650/850 GHz array receiver
mounted on the APEX telescope. In addition, isotopologue observations
of the 13CO J=6-5
transition and [C I] line
were taken.
Results. Strong quiescent narrow-line 12CO
6-5 and 7-6 emission is seen toward all protostars. In the
case of HH 46 and Ced 110 IRS 4, the
on-source emission originates in material heated by UV photons
scattered in the outflow cavity and not just by passive heating in the
inner envelope. Warm quiescent gas is also present along the outflows,
heated by UV photons from shocks. This is clearly evident in
BHR 71 for which quiescent emission becomes stronger at more
distant outflow positions. Shock-heated warm gas is only detected for
Class 0 flows and the more massive Class I sources such as
HH 46. Outflow temperatures, estimated from the
CO 6-5 and 3-2 line wings, are 100 K, close to model predictions, with
the exception of the L 1551 IRS 5 and IRAS
12496-7650, for which temperatures <50 K are found.
Conclusions. APEX-CHAMP+ is
uniquely suited to directly probe the protostar's feedback on its
accreting envelope gas in terms of heating, photodissociation, and
outflow dispersal by mapping
regions in high-J
CO and
[C I] lines. Photon-heating of the surrounding gas
may prevent further collapse and limit stellar growth.
Key words: astrochemistry - stars: formation - ISM: jets and outflows - submillimeter - stars: circumstellar matter - stars: pre-main sequence
1 Introduction
Low-mass (M<3

Envelope models can be constructed using either a 1-D or 2-D
self-consistent dust radiative transfer calculation, constrained by
observations of the cold dust (e.g. Shirley et al. 2002; Jørgensen
et al. 2002)
and/or the spectral energy distribution (SED)
(e.g. Whitney
et al. 2003a,b; Robitaille et al. 2006;
Crapsi
et al. 2008). Combining heterodyne observations with
radiative transfer
calculations, one can in turn analyze line emission of a large range
of molecules and determine their origin and excitation conditions,
both in the inner and outer regions of protostellar envelopes as well
as in circumstellar disks and fore-ground components
(e.g. Lee
et al. 2007; Brinch et al. 2007; Maret
et al. 2004; Jørgensen 2004; Boogert
et al. 2002). Envelope
models predict that the inner regions are warm (T>100 K),
dense
(n(H2) >106 cm-3)
and relatively small (R< 500 AU).
Most molecular lines observable at (sub)mm wavelengths trace the
colder gas, but a few lines, such as the high-J
CO lines, directly
probe the warm gas. The atmospheric windows at 650 and
850 GHz are the
highest frequency windows in which observations of CO (up to energy
levels of 150 K)
can be routinely carried out. Unfortunately,
few studies have succesfully observed CO transitions or its
isotopologues in these atmospheric windows due to the excellent
weather conditions necessary. In addition, such studies are often
limited to single spectra of only a handful of YSOs
(e.g. Parise
et al. 2006; Schuster et al. 1993; Ceccarelli
et al. 2002; Hogerheijde et al. 1998;
Stark
et al. 2004; Schuster et al. 1995; van Kempen
et al. 2006). The lack of spatial information on the
warm
gas distribution has prevented an in-depth analysis. Comparison
between ground-based high-J CO observations and
far-IR CO
transitions (CO 15-14 and higher) do not always agree on the
origin
of the high-J CO lines (van Kempen et al. 2006).
Complex molecules such as H2CO and CH3OH, emit in high excitation lines at longer wavelengths, and have been observed to have surprisingly high abundances in low-mass protostars (e.g. Ceccarelli et al. 2000; Bottinelli et al. 2007,2004; Blake et al. 1995; van Dishoeck et al. 1995; Maret et al. 2004; Jørgensen 2004; Schöier et al. 2002). Unfortunately, the abundances of these molecules are influenced by the gas-phase and grain surface chemistry, complicating their use as tracers of the physical structure (e.g., Bisschop et al. 2007). It has been proposed that the emission of such molecules originates inside a hot core region, a chemically active area close to the star, coinciding with the passively heated warm inner region of the protostellar envelope where ices have evaporated (Ceccarelli et al. 2000; Bottinelli et al. 2007,2004). However, to fully understand the origin of these complex organics, knowledge of the structure of the warm gas is an essential ingredient.
Warm gas near protostars can have different origins than
passive
heating alone. Outflow shocks passing through the envelope can be a
source of heat. Quiescent gas, heated by X-rays or UV, is present in
the inner envelope. For example, Stäuber
et al. (2004) show that
significant amounts of far ultra-violet (FUV) or X-ray photons are
necessary to reproduce the line intensities and the derived abundances
of molecules, such as CO+, CN, CH+
and NO in both high and
low-mass protostars. Spaans
et al. (1995) investigated photon heating of
outflow cavity walls to reproduce the observed line intensties and
widths of 12CO 6-5 and 13CO 6-5
emission in Class I
sources (Hogerheijde
et al. 1998). In Paper I, an extension
of this model is proposed in which a Photon Dominated Region (PDR) at
the outflow/envelope cavity walls is present in the HH 46
outflow to
explain the relatively strong and quiescent high-J
CO emission. The
emission of [C I] can constrain the color and extent of the
more
energetic photons. Apart from the accretion disk, UV photons are also
produced by the jet shocks in the outflow cavity and the outflow bow
shock. All these models provide different predictions for the spatial
extent of the warm gas (1
for
the outflow to <1
for
a
passively heated envelope), as well as the different integrated
intensities and line profiles of the high-J
CO transitions.
The most direct tracers of the warm (50<T<200 K) gas are thus the high-J CO lines. So far, studies to directly detect the warm gas components through these lines have rarely been able to disentangle the envelope and outflow contributions. Far infrared (IR) transitions of even higher-J CO, the far-IR CO lines, have been observed using the ISO-LWS instrument to trace the inner regions (e.g., Giannini et al. 2001; Nisini et al. 2002; Ceccarelli et al. 1998; Nisini et al. 1999; Giannini et al. 1999), but could not unambigiously constrain the origin of the warm gas emission, due to the limited spatial and spectral resolution.
The Chajnantor plateau in northern Chile, where the recently
commissioned Atacama Pathfinder EXperiment (APEX)
is located,
currently is the only site able to perform routine observations within
the high frequency atmospheric windows at high (
10
)
spatial
resolutions. The CHAMP+ instrument, developed by
the MPIfR and SRON
Groningen, is the only instrument in the world able to simultaneously
observe molecular line emission in the 650 and
850 GHz atmospheric
windows on sub-arcminute spatial scales and is thus ideally suited to
probe the warm gas directly through observations of the 6-5, 7-6 and
8-7 transitions of CO and its isotopologues with 7-9
angular
resolution (Güsten
et al. 2008; Kasemann et al. 2006).
CHAMP+ has 14 pixels (7
in each frequency window) and is thus capable of fast mapping of the
immediate surroundings of embedded YSOs. The Herschel Space
Observatory will allow observations of far-IR CO lines at
spectral
and spatial resolution similar to APEX (
10
).
Note also that
the beam of Herschel is comparable or smaller than the field of view
of CHAMP+ at its longer wavelenghts (
500
m). Thus the
CHAMP+ data obtained here provide information of
the distribution
of warm gas within the Herschel beams.
In Paper I, we presented the results for one source, HH 46 IRS. In this paper, we present observations of CO and its isotopologues using CHAMP+ for seven additional embedded YSOs and compare them with the HH 46 case. Section 2 presents the sample and observations. The resulting spectral maps are shown in Sect. 3. Section 4 discusses the envelope and outflow structure, while the heating within protostellar envelopes and molecular outflows is analyzed in Sect. 5. Section 6 investigates the relation between the emission of more complex molecules and the emission of high-J CO. Final conclusions are given in Sect. 7.
2 Sample and observations
2.1 Observations
The sample was observed using the CHAMP+ array (Güsten
et al. 2008; Kasemann et al. 2006)
on APEX
(Kasemann et al. 2006).
CHAMP+ observes simultaneously in the
650 GHz
(450 m,
CHAMP+-I) and 850 GHz (350
m, CHAMP+-II)
atmospheric windows. The array has 7 pixels for each
frequency,
arranged in a hexagon of 6 pixels around 1 central
pixel, for a total
of 14 pixels. During the observations, the backend consisted
of 2 Fast
Fourier Transform Spectrometer (FFTS) units serving the central pixel,
and 12 MPI-Auto-Correlator Spectrometer (MACS) units serving
the other
pixels. The FFTS units are capable of observing up to a resolution of
0.04 km s-1
(0.12 MHz) and the MACS units to a spectral
resolution of 0.37 km s-1
(1 MHz), both at a frequency of 806 GHz. The
observations were done during three observing runs in June
2007, October-November 2007 and July 2008 in three different
line
settings; see Table 1.
Note that in July 2008, all
pixels were attached to FFTS units and no MACS backends were used.
For mapping purposes, the array was moved in a small hexagonal pattern
to provide a fully Nyquist sampled map or in an on-the-fly (OTF)
mode. The ``hexa'' pattern covers a region of about
.
For some sources, a slightly larger area was mapped
in a small OTF (
)
map in 12CO 6-5/7-6. Both kinds of
maps were regridded to a regular grid with standard rebinning
algorithms included in the CLASS package
.
A binning method that uses equal weight binning was adopted to produce
contour maps. A pixelsize of 1/3rd of the beamsize was adopted to
create accurate contour maps. CLASS was also used as the main reduction
package for individual lines. At the
edge of the maps, noise levels are often higher due to the shape of
the CHAMP+ array. NGC 1333
IRAS 2, TMR 1 and RCrA IRS 7 were
observed using the hexa mode and have smaller covered areas. Due to
the different beams at 690 and 800 GHz, small differences
exist
between the areas covered in CO 6-5 and 7-6. For the C18O 6-5/13CO 8-7
(setting C; only done for HH 46), a stare mode was
used to increase the S/N within the central pixel. A position switch
of 900
was used for all settings,
except for the stare setting C,
which used a beam-switching of 90
.
Beam efficiencies, derived using observations on planets
during each run, are 0.56 for
CHAMP+-I and 0.43 for CHAMP+-II.
These efficiencies were found to vary by less than 10
over a single observing run and between runs. Between pixels the
variation is similar, all within 10
.
Depending on observing
mode, a given sky position is covered by many (all) pixels, so the
average
(relative) calibration error will be a few per cent. Typical single
side-band system
temperatures are 700 K for CHAMP+-I and
2100 K for CHAMP+-II.
The 12-m APEX dish produces a beam of 9
at 650 GHz and 7
at
850 GHz. Pointing was checked on various planets and sources
and was
found to be within 3
.
Calibration of the sources was done using
similar observations, as well as hot and cold loads.
The typical sideband rejection at both frequencies was measured to be
less than 10dB. At APEX 10 dB is used as the input to the
calibrator (both continuum and line. From all these effects, the total
calibration error is estimated to be
30
,
including the atmospheric model.
Note that all technical aspects of CHAMP+ will
be discussed more extensively in Güsten et al. (to be
submitted to A&A, see also Güsten
et al. 2008).
The difference in CO 7-6
emission of 60
for IRAS 12496-7650 in van
Kempen et al. (2006) and this
paper can be accounted for by the respective calibration and pointing
errors of FLASH and CHAMP+. A factor of
2 difference is found with
the observations of TMR 1 in Hogerheijde
et al. (1998). Since a similar
factor of 2 is seen between the observations of T Tau
in
Schuster et al. (1995)
and Hogerheijde et al.
(1998), it is most likely that
the side-band gain ratios for the observations taken by
Hogerheijde et al. (1998)
were incorrectly calibrated.
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Figure 1: Maps of CO 6-5 ( top row) and CO 7-6 ( bottom row) of NGC 1333 IRAS 2. The left-most image shows the total integrated intensity over the line. The middle figures show the outflow contributions from the red ( dashed lines) and blue ( solid lines) outflow. Contours are in increasing levels of 4 K km s-1 for both transitions. The outflow contributions are calculated by only including emission greater or smaller than +/-1.5 km s-1 from the central velocity. The right-most image at the top row shows the 12CO spectra at the central position. |
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Figure 2: Maps of CO 6-5 ( top row) and CO 7-6 ( bottom row) of L 1551 IRS 5. The left-most image shows the total integrated intensity over the line. The middle figures show the outflow contributions from the red ( dashed lines) and blue ( solid lines) outflow. Contours are in increasing levels of 0.5 K km s-1 for both transitions. The outflow contributions are calculated by only including emission greater or smaller than +/-1.5 km s-1 from the central velocity. The right-most image at the top row shows the 12CO spectra at the central position. |
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Figure 3: Maps of CO 6-5 ( top row) and CO 7-6 ( bottom row) of TMR 1. The left-most image shows the total integrated intensity over the line. The middle figures show the outflow contributions from the red ( dashed lines) and blue ( solid lines) outflow. Contours are in increasing levels of 1 K km s-1 for both transitions.The outflow contributions are calculated by only including emission greater or smaller than +/-1.5 km s-1 from the central velocity. The right-most image at the top row shows the 12CO spectra at the central position, while the right-most image at the bottom row shows the spectra of the observed isotopologues and [C I] 2-1 at the central position. |
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Figure 4: CO 6-5 ( left) CO 7-6 ( middle) maps and spectra of the central position of HH 46. The left-most image shows the total integrated intensity over the line. The middle figures show the outflow contributions from the red ( dashed lines) and blue ( solid lines) outflow. Contours are in increasing levels of 2 K km s-1 for CO 6-5 and 3 K km s-1 for CO 7-6. The outflow contributions are calculated by only including emission greater or smaller than +/-1.5 km s-1 from the central velocity. The right-most image at the top row shows the 12CO spectra at the central position, while the right-most image at the bottom row shows the spectra of the observed isotopologues and [C I] 2-1 at the central position (see also Paper I). |
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Figure 5: Maps of CO 6-5 ( top row) and CO 7-6 ( bottom row) of Ced 110 IRS 4. The left-most image shows the total integrated intensity over the line. The middle figures show the outflow contributions from the red ( dashed lines) and blue ( solid lines) outflow. Contours are in increasing levels of 3 K km s-1 for both transitions. The outflow contributions are calculated by only including emission greater or smaller than +/-1.5 km s-1 from the central velocity. The right-most image at the top row shows the 12CO spectra at the central position, while the right-most image at the bottom row shows the spectra of the observed isotopologues and [C I] 2-1 at the central position. |
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Figure 6: Maps of CO 6-5 ( top row) and CO 7-6 ( bottom row) of BHR 71. The left-most image shows the total integrated intensity over the line. The middle figures show the outflow contributions from the red ( dashed lines) and blue ( solid lines) outflow. Contours are in increasing levels of 10 K km s-1 for CO 6-5 and 5 K km s-1 for CO 7-6. The outflow contributions are calculated by only including emission greater or smaller than +/-1.5 km s-1 from the central velocity. The right-most image at the top row shows the 12CO spectra at the central position, while the right-most image at the bottom row shows the spectra of the observed isotopologues and [C I] 2-1 at the central position. |
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Figure 7: Maps of CO 6-5 ( top row) and CO 7-6 ( bottom row) of IRAS 12496-7650. The left-most image shows the total integrated intensity over the line. The middle figures show the outflow contributions from the red ( dashed lines) and blue ( solid lines) outflow. Contours are in increasing levels of 3 K km s-1 for both transitions. The outflow contributions are calculated by only including emission greater or smaller than +/-1.5 km s-1 from the central velocity. The right-most image at the top row shows the 12CO spectra at the central position, while the right-most image at the bottom row shows the spectra of the observed isotopologues and [C I] 2-1 at the central position. |
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Figure 8: Maps of CO 6-5 ( top row) and CO 7-6 ( bottom row) of RCrA IRS 7a. The left-most image shows the total integrated intensity over the line. The middle figures show the outflow contributions from the red ( dashed lines) and blue ( solid lines) outflow. Contours are in increasing levels of 10 K km s-1 for both transitions. The outflow contributions are calculated by only including emission greater or smaller than +/-8 km s-1 from the central velocity. The right-most image at the top row shows the 12CO spectra at the central position. |
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2.2 Sample
The sample consists of eight well-known and well-studied embedded protostars, with a slight bias toward the southern sky. A variety of protostars in mass, luminosity, evolutionary stage and parental cloud is included. All sources have been studied in previous surveys of embedded YSOs in the sub-mm (e.g., Jørgensen et al. 2004,2002; Groppi et al. 2007). More information on southern sources can be found in van Kempen et al. (2006) (IRAS 12496-7650), van Kempen et al. 2009 submitted (IRAS 12496-7650, RCrA IRS 7 and Ced 110 IRS 4) and Paper I (HH 46). Table 2 gives the parameters of each source and its properties. References to previous continuum studies (Col. 7) include infrared (IR) and (sub)millimeter dust continuum photometry, and studies of CO emission (Col. 8) include both submillimeter and far-IR lines. Note that the binary source of N1333 IRAS 2A, N1333 IRAS 2B is not covered by our map.2.3 Spectral energy distribution
For all sources, SED information was acquired from the literature, ranging from near-IR to the (sub-)mm wavelengths. Spitzer-IRAC (3.6, 4.5, 5.6, 8.0








3 Results
3.1 Maps
Figures 1 to 8 show the integrated intensity and the red- and blue-shifted outflow emission mapped in the CO 6-5 line, as well as the spectra at the central position of all observed emission lines. Both the integrated intensity and outflow maps were spatially rebinned to a resolution of 10


Table 3
presents the intensities of both CO lines. Here, the total
integrated emission, the peak main beam
temperature, the emission in the red and blue outflow wings shown in
the outflow maps and the noise levels are given for the central
position, as well as at positions with clear detections of outflow
wings away from the center. The limits for the
red and blue outflow were chosen to be -10 to
-1.5 km s-1 with
respect to the source velocity for the blueshifted emission and +1.5 to
+10 km s-1 with respect to the
source velocity for the
redshifted emission for most sources. These limits were chosen after
examination of the profiles of the spectra and subtracting Gaussians
that were fitted to the central 3 km s-1
of the profile. For all
sources, except RCrA IRS 7, the difference in the
blue- and
red-shifted emission between the two methods was less than 5.
The
outflowing gas of RCrA IRS 7 was derived by limiting the red- and
blue-shifted emission to -20 to -8 and +8 to +20 km s-1
from line
center. This corresponds to a
km s-1
for the
quiescent material. Broad line widths of 3 km s-1
are also seen
for the rarer isotopologues C18O and C17O,
much wider than
typically observed for these species in low-mass YSOs
(Schöier et al. 2006).
Noise levels (see Table 3)
differ greatly between sources and even within single maps.
12CO 6-5 and 7-6 was detected at the
central position of all
sources, ranging from 20.8 K km s-1
(
K) for
Ced 110 IRS 4 for CO 6-5 to
407.6 K km s-1 (
K) for
RCrA IRS 7A for the CO 7-6 line.
All maps show extended
emission, except for IRAS 12496-7650, which shows unresolved
emission
in the CO 7-6 transition. However, the scales on which
extended
emission is seen varies significantly, with detections at all mapped
positions for RCrA IRS 7 to only 1 or 2 for
IRAS 12496-7650, TMR 1 and
Ced 110 IRS 4. All sources except RCrA IRS 7
and NGC 1333 IRAS 2 show
spectra with a single peak over the entire map, while the latter two
have spectra that are self-absorbed.
Figures 9 to 12 clearly identify the variation of the line profiles across the maps, especially when outflowing gas is present, such as in the maps of NGC 1333 IRAS 2, BHR 71, HH 46 and RCrA IRS 7. The sources for which little to no shocked emission is seen do show spatially resolved CO 6-5 and 7-6 emission, but always quiescent narrow emission located close to the central pixel.
3.2 Outflow emission
From the outflow maps in Figs. 1 to 8,
it can be concluded that the contributions from shocks within the
bipolar outflows to the warm gas differ greatly from source to
source. RCrA IRS 7, NGC 1333 IRAS 2,
HH 46, and BHR 71 produce
spatially resolved flows, but TMR 1, L 1551
IRS 5, IRAS 12496-7650 and
Ced 110 IRS 4 do not have warm shocked gas that
results in broad high-J CO
in any of the off-positions. Small shocks on the source position are
seen, but are generally weak. For all sources in the sample, outflow
emission has been detected in low (
)
excitation CO
lines, although such flows have large differences in spatial scales,
ranging from tens of arcminutes to the central twenty arcseconds
(e.g. Parise
et al. 2006; Bourke et al. 1997; Moriarty-Schieven
& Snell 1988; Bachiller et al. 1994;
Cabrit
& Bertout 1992; Hogerheijde et al. 1998;
Fridlund
et al. 1989; van Kempen et al.
2009, submitted). Table 3 gives the
integrated intensities of the CO emission
at selected off-positions for the outflowing gas.
3.3 Isotopologue observations at the central position
For HH 46, transitions of 13CO J=6-5
and 8-7 and C18O
J=6-5 as well as [C I] 2-1 were
observed (see Table 1
and 2).
TMR 1, Ced 110 IRS 4,
IRAS 12496-7650 and BHR 71 were observed in 13CO 6-5
and [C I] 2-1. The results at the central position
can be found in Fig. 1
to 8,
as well as Table 4.
All 13CO 6-5 spectra can be fitted with
single Gaussians. However, the width of the Gaussians varies with a FWHM
of 1.2 km s-1
for HH 46 and BHR 71 to
2.2 km s-1
for Ced 110 IRS 4 and IRAS 12496-7650.
[C I] 2-1 is detected for TMR 1,
HH 46 and Ced 110 IRS 4 (
3
). No
line was found for IRAS 12496-7650 and BHR 71 down to
a 1
limit of
0.6 K in 0.7 km s-1
bins. Integrated line strengths are
on the order of 3 K km s-1
with widths of 0.75 km s-1.
13CO 8-7 and C18O 6-5
were observed towards HH 46 only,
but not detected down to a 1
level of 0.15 and 0.3 in a 0.7 km s-1
channel.
3.4 13CO 6-5 and [C I] 2-1 maps
For 13CO 6-5 and [C I] 2-1 maps were also obtained. Spectra at the central position are given in Figs. 1 to 8. Integrated intensity maps are presented in Fig. 13 (13CO 6-5) and Fig. 14 ([C I] 2-1) It is seen that such observations are often dominated by centrally located unresolved emission, but not always peaked at the source. Both HH 46 and BHR 71 also show some isotopic emission associated with the outflow. For HH 46, 13CO 6-5 is only detected off-source for the blue outflow, where part of the outflow is unobscured by cloud or envelope (Paper I).
Table 1: Adopted Champ+ settings.
4 Envelope
4.1 Envelope models
In order to investigate whether high-J CO emission can be reproduced by a passively heated envelope, the properties of the protostellar envelopes were calculated by modelling 850







The parameters of the best-fitting envelope models can be
found in
Table 5,
together with the corresponding physical
parameters of the envelope. The three main parameters of DUSTY, Y,
the ratio over the inner to outer radius, p, the
power law exponent
of the density profile and
,
the opacity at a 100
m,
are scaled by the
and the
distance, D given in Table 2, to get the
physical
properties of each source. Figure 15 shows the
best-fitting model of each source of the radial profiles of the
850
m
images and the SEDs of the entire sample.
The inner radii of the protostellar envelopes range
from 5 to 35 AU corresponding to
K,
a limit chosen by us. Most sources also show a steep profile with all
sources having
,
with the exception of Ced 110 IRS 4, which has a p=1.4.
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Figure 9:
Spectra of 12CO 6-5 over an area of
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Figure 10:
Spectra of 12CO 6-5 over an area of
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Figure 11:
Spectra of 12CO 6-5 over an area of
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Figure 12:
Spectra of 12CO 6-5 over an area of
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Figure 13: 13CO 6-5 integrated intensity maps of BHR 71 ( upper left), Ced 110 IRS 4 ( upper middle), HH 46 ( upper right), IRAS 12496-7650 ( lower left) and TMR 1 ( lower middle). |
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Figure 14: [C I] 2-1 integrated intensity maps of Ced 110 IRS 4 ( left) and TMR 1 ( right). Note that the TMR 1 data suffer from a de-rotation problem in the calibrator data and are subject to change. |
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Figure 15:
The SEDs and radial profiles at 850 |
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Figure 16:
The contribution of the envelope to CO lines at the source position
with |
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4.2 CO emission within protostellar envelopes
Using the best-fit envelope temperature and density structure derived
from the dust emission, the CO intensities and line profiles from the
protostellar envelopes were in turn simulated with the self-consistent
1D molecular line radiative transfer code RATRAN (Hogerheijde & van der Tak 2000)
using data files of the LAMDA database (Schöier
et al. 2005). CO
abundances with respect to H2 are taken from
Jørgensen et al. (2005).
A ``drop'' abundance with
and
is adopted. This ``drop''
abundance profile describes a warm (
)
inner region
with a high abundance X0
and a region in which
and
where CO is frozen out to a low abundance
.
In the outer region (
), the abundance is again
high at X0 because
freeze-out timescales become longer than the
typical life-times of protostars. In our models,
K
and
cm-3
are adopted, following the
conclusions of Jørgensen
et al. (2005). There, the derived abundances are
based upon the emission of low-excitation optically thin lines such as
C18O lines (both 2-1 and 3-2, 1-0 is often
dominated by the
very cold cloud material) and C17O. Paper I
showed
that contrary to the low-J CO lines there
is little difference
between ``jump'' and ``drop'' abundances for the emission in high-Jtransitions.
A static velocity field is assumed with a turbulent width
of 1 km s-1. Due to the static
nature of the velocity field,
excessive self-absorption is seen in line profiles of CO lines
up to
the 8-7 transition. The total area of a Gaussian fitted to the line
wings is used in those cases to derive an upper limit. This is a very
strict limit as the true CO emission associated with the
envelope is
best fitted by a infall velocity (Schöier
et al. 2002), producing
integrated intensities between the two limits. However,
Schöier et al. (2002)
show that the envelope emission modelled with an
infall velocity is in the worst case only a factor 2 greater than the
intensity derived from the static envelope. The lower limit is derived
from the actual modelled integrated intensity with the static velocity
field.
Figure 16
shows the resulting integrated intensities produced by the model
protostellar envelopes of all CO lines from J=1-0
up to J=19-18. The data for all transitions were
convolved with a 10
beam used for CHAMP+,
except the three lowest
transitions, which are convolved with a beam of 20
.
Such beams are typical for single-dish submillimeter telescopes. 10
will also be the approximate
beam for several transitions covered by
the PACS and HIFI
(Band 6 and 7) instruments on Herschel at the higher
frequencies. Overplotted are the observed line strengths from various
CO lines of different studies, including the far-IR high-J
CO lines of Giannini
et al. (1999) and Giannini
et al. (2001), assuming that all flux observed by
the ISO-LWS in its 80
beam originates in a 10
region. See Table 2
for the references used.
The low-J CO emission can often be completely reproduced by the envelope models, as it is dominated by the colder gas in the outer regions of the envelopes. For HH 46, Ced 110 IRS 4 and RCrA IRS 7, the observed quiescent emission in the CO 6-5 and 7-6 lines is clearly brighter by a factor of 3-5 than the modelled envelope emission, even for the 13CO 6-5 lines (see Table 6).
For RCrA IRS 7, the difference is almost an order magnitude. Deep C18O 6-5 spectra are needed to fully pin down the envelope models. In Paper I, the quiescent CO 6-5 and 7-6 emission of HH 46 was attributed to ``photon heating'' (Spaans et al. 1995), both by UV from the accretion disk and shocks inside the outflow cavity. Figure 16 clearly shows that this method of heating likely applies to other sources.
In contrast, the envelopes of both IRAS 12496-7650 and
L 1551 IRS 5 can account for all the emission
detected in the 12CO 6-5 and
7-6 lines. Giannini
et al. (1999) and Giannini
et al. (2001) report emission
of high-J CO (14-13 to 19-18) lines at far-IR of
NGC 1333 IRAS 2,
IRAS 12496-7650 and RCrA. For RCrA, RCrA IRS 7 is
within the beam, but
the emission is probably dominated by emission from RCrA itself.
Fluxes in excess of 10-20 W cm-2
are seen for IRAS 12496-7650. They assumed that the flux
originates within the central
3
(
400 AU).
It is very clear from Fig. 16
that such observed emission cannot be produced by a passively heated
envelope. A more likely explanation is that the CO emission detected
with ISO-LWS is either located outside the inner 10
as is the
likely case for IRAS 12496-7650 (see van
Kempen et al. 2006) or
associated with an energetic outflow.
5 Outflows
5.1 Shocks
Bachiller & Tafalla (1999)
propose an evolutionary sequence of outflows
around low-mass protostars, with young deeply embedded YSOs
(Class 0)
producing highly collimated and energetic outflows, and with more
evolved embedded YSOs (Class I) producing outflows which show
less
energetic shocks and a wider opening angle (Arce
et al. 2007, see also). Observations of the shocked 12CO 6-5
and 7-6
gas in the outflow directions confirm the scenario that the shocks
within the vicinity of the protostar grow weaker in energy over
time. The Class 0 sources (NGC 1333 IRAS 2,
BHR 71 and RCrA IRS 7) all
show shocked warm gas in their CO 6-5 and 7-6 lines,
in both blue-
and red-shifted outflow. Of the Class I sources, only
HH 46 shows
shocked gas in its red-shifted outflow. L 1551 IRS 5,
one of the
most-studied molecular outflows
(Bachiller
et al. 1994; Moriarty-Schieven & Snell
1988), shows little emission in the
high-J lines associated with outflow shocks.
Although several
spectra do show a small outflow wing, the integrated emission in the
wings is not higher than a few .
All other Class I flows show
no sign of shocked warm gas. HH 46 and L 1551
IRS 5, even though
classified as Class I, have massive envelopes of a
few
,
more
characteristic of Class 0 (Jørgensen
et al. 2002). L 1551 IRS 5 is
believed to be older and to consist of several sucessive ejection
events
(White
et al. 2000; Bachiller et al. 1994).
Figure 17
shows the maximum outflow velocities of the 12CO 6-5
and 3-2 lines vs. the bolometric temperature, envelope mass
and outflow force. A clear absence of warm high-velocity material is
seen for sources with a higher bolometric temperature. Only the cold
outflow of IRAS 12496-7650 is seen at higher
(van
Kempen et al. 2006).
Similarly, there is also a clear relation between the mean outflow
force of both red and blue outflow lobes, and the maximum velocity seen
in both 12CO 3-2 and 12CO 6-5
emission. Outflow forces are derived from the spatial scales and
velocities of low-excitation CO line emission (1-0, 2-1 and 3-2) (Bourke
et al. 1997; Hogerheijde et al. 1998;
Cabrit
& Bertout 1992, Paper I; van Kempen
et al. 2009, submitted)
5.2 Temperatures of the swept-up gas
The excitation temperature of the outflowing swept-up gas can be derived from the ratios of different CO line wings. As an example, Fig. 18 shows the CO 3-2 data from van Kempen et al. (2009) submitted and Paper I and CO 6-5 data from this paper overplotted on the same scales for a few sources. The CO 6-5 data have not been binned to the larger CO 3-2 beam, so the comparison assumes similar volume filling factors of the shocked gas; for HH 46 in Paper I it has been checked that rebinning gives similar results within the uncertainties. If the density is known this excitation temperature can be related to the kinetic temperature using the diagnostic plots produced by the RADEX radiative transfer code (van der Tak et al. 2007).
As can be seen from the temperature analysis of HH 46 (Paper I), there are many uncertainties, leading to error bars as large as 50 K on the inferred temperatures. The ratios depend on the velocity, the optical depth of the line wings and the ambient density at different distances from the source. For HH 46, a drop in temperature was observed if the density remains constant, but it is more plausible that the density is lower at larger radii which will result in a constant kinetic temperature with distance.
Table 7
gives the median temperatures using the extreme
velocities of the line wings with intensities >,
assuming the
line wings are optically thin and with an ambient cloud density of
104 cm-3.
CO 3-2 spectra can be found in
Hogerheijde et al. (1998)
(TMR 1, L 1551 IRS 5), Knee
& Sandell (2000) (NGC 1333
IRAS 2), Parise
et al. (2006) (BHR 71), van Kempen et al. (2006)
(IRAS 12496-7650), van Kempen et al. (2009,
submitted) (RCrA IRS 7, Ced 110 IRS 4) and
Paper I (HH 46).
Table 2: The sample of sources observed with CHAMP+.
Table 3: Properties of the 12CO linesa.
The main error on these temperature estimates is the optical
depth in
the outflow wings. Deep 13CO 3-2 observations
show that outflows
can be optically thick. Hogerheijde
et al. (1998) find optical depths in
the 12CO 3-2 line wings,
,
on the order of 10,
while in Paper I
-1.8
is found for
HH 46. Even if the optical depths are assumed to be similar in
CO 3-2
and CO 6-5, kinetic temperatures can be almost 50
lower than
those given in Table 7.
For a more thorough discussion about the density of the surrounding envelope and cloud material, see Paper I. Our choice of the density of 104 cm-3 is based on the typical densities found in model envelopes of Jørgensen et al. (2002) at distances of a few thousand AU, corresponding to the 10 K radius where the envelope merges with the surrounding molecular cloud. Higher densities will produce lower outflow temperatures (see Paper I for more extensive discussion).
A theoretical study by
Hatchell et al. (1999)
using a jet-driven bow shock model suggests that
the kinetic temperatures of molecular outflows are typically of order
of 50-150 K along the axis and rising toward the location of
the bow
shock, with overall values increasing with higher jet velocities. The
temperatures found in Table 7 agree well
with
these predicted temperatures. For several outflows, e.g.,
IRAS 12496-7650 (blue) or Ced 110 IRS 4
(red), temperatures are
significantly lower, however. The lowest outflow temperatures are found
for
the flows of L 1551 IRS 5, where
CO 4-3/6-5 ratios are on the order of 8
or higher. At an assumed density of 104 cm-3,
this corresponds
to kinetic temperatures of 50 K and lower. If both line wings
are
optically thin, densities must be lower than 103 cm-3
to
produce temperatures of 100 K,
observed for other flows.
6 Heating processes in the molecular outflow and protostellar envelope
As discussed in Sect. 4, several sources show quiescent, narrow 12CO 6-5 and 7-6 emission that is more intense than can be produced by an envelope model. Moreover, strong narrow high-J CO emission is observed off-source along outflow axes for most sources. In Paper I, we proposed that for HH 46 the quiescent narrow 12CO 6-5 and 7-6 line emission originates within the outflow cavity walls heated to 250-400 K by an enhancement factor G0 with respect to the standard interstellar radiation field of a few hundred. The UV photons can be created by jet shocks in the outflow cavities as well as in the disk-star accretion boundary layer near the central protostar. This heating method was first proposed by Spaans et al. (1995), but extended by Paper I to both the inner envelope as well as the outflow cavity walls much further from the central star. The data presented in this paper show that photon heating is present in other protostars as well, especially in outflow cavities. Even in sources with little to no outflow, such as Ced 110 IRS 4, relatively strong narrow 12CO 6-5 and 7-6 lines are seen at positions not associated with the central protostar, see Fig. 16. The presence of significant radiative ``feedback'' from the protostar on its surroundings may have consequences for the collapse of the envelope, limiting the accretion rate and mass of the star and suppressing disk fragmentation (e.g., Offner et al. 2009).
The origin of such quiescent high-J CO emission at the source velocity is physically different from both the thermal emission of the protostellar envelope (see Sect. 6.4), emission from shocks present at the working surfaces of outflows (Raga et al. 2007; Reipurth & Raga 1999).
Slow (
km s-1)
C-shocks may produce similar quiescent
levels of CO 6-5 and 7-6 emission in outflows
(Spaans
et al. 1995; Draine & Roberge 1984).
However, the presence of quiescent
12CO 6-5 and 7-6 emission in
the envelopes of TMR 1 and Ced 110
IRS 4, both of which show little to no spatially resolved
outflow
emission in the CO 3-2 line (Hogerheijde et al. 1998;
van Kempen et al. submitted), is more easily
explained with the
photon heating scenario than with slow C-shocks. In addition, the
narrow line widths for other sources argue against this scenario.
6.1 Envelope and outflow of BHR 71
The proposed model that photon heating takes place both in the outflow
cavities and the inner envelope is clearly illustrated by the
observations of BHR 71. At the north and south position of the
outflow, shocked gas is clearly detected, but almost no shocked gas is
seen near the central star. Quiescent gas with
km s-1
is observed both within the inner envelope and along the
outflow. In the 12CO 7-6 map,
the photon heating in the
envelope can be strongly identified by the central contour.
BHR 71 is
the only source for which the quiescent emission at the outflow
position is (much) brighter than that seen at the position of the
envelope. It is likely that strong shocks producing copious UV are
present in the main outflow. This outflow (Bourke
et al. 1997) is
clearly detected at the edges of the map, but the secondary weaker
outflow, associated with the IRS2 position, as seen by
Parise et al. (2006)
is not detected down to the noise levels. Shocked CO 6-5 and
7-6 emission is also only seen at relatively low levels in
the inner 20
and strongly increases
at 40
away from the source
for both outflows.
6.2 The ``fossil'' outflow of L 1551 IRS 5
The outflow of L 1551 IRS 5 has been considered an example of
an older
outflow, due to its large size (Moriarty-Schieven & Snell
1988; Fridlund
et al. 1989),
large opening angle (Bachiller
et al. 1994) and other submillimeter
properties (Bachiller
et al. 1994; Hogerheijde et al. 1998;
Cabrit
& Bertout 1992). White
et al. (2000)
constructed a detailed model from a wide variety of space- and
ground-based IR continuum and spectroscopic observations, including a
wide opening angle of the outflow (50
)
and low
densities inside the cavity. This view is clearly confirmed by the low
derived temperatures of 40 to 50 K of the shocked
gas, which is much
cooler than in other sources. Little high-J
CO emission is seen at
the off-positions, and the maps are dominated by the emission of the
central source. Comparison of the peak temperatures of CO 4-3 (Hogerheijde et al. 1998),
6-5 and 7-6 shows that
at
high-J transitions is similar to that at low-J
CO transitions. This suggest that even though the outflow is
present, the density in the surrounding cloud must be quite low.
![]() |
Figure 17:
|
Open with DEXTER |
![]() |
Figure 18: Line wings of CO 6-5 ( solid) and CO 3-2 ( dashed) for HH 46 (red wing at central position and in the red outflow), Ced 110 IRS 4 (blue at the central position), RCrA IRS 7A (red and blue at the central position). |
Open with DEXTER |
6.3 The PDR of RCrA IRS 7
The lines of RCrA IRS 7 are an order of magnitude stronger
than those
of equivalent sources in different clouds. Even at off-positions at
the edge of the observed area, integrated intensities larger than
300 K km s-1 are
seen. Even with the high luminosity of 20-30
,
these integrated intensities cannot originate from heating
by RCrA IRS 7 itself. A likely explanation is the proximity of
the A5
star RCrA (
)
at 36
(4500 AU). RCrA
was observed by ISO-LWS, and many strong high-J CO lines
(CO 14-13 to 21-20) were detected in the large beam of ISO
(Lorenzetti
et al. 1999; Giannini et al. 1999).
Models were put forward with the
emission originating in relatively small (
0.002 pc), dense
(>106 cm-3)
and hot (
T>300-1000 K)
regions
(Giannini et al. 1999).
However, the spatial distribution of the CO 6-5 and 7-6 seen
in Fig. 8
does not agree with this
hypothesis. A much more likely explanation is that RCrA itself
irradiates the outer edges of the cloud and envelope around RCrA IRS
7a, creating a PDR at its surface, much like the case of intermediate
mass sources in Orion (Jørgensen
et al. 2006).
6.4 Presence of [C I] 2-1
A limit on the amount of FUV/X-ray emission that is available to dissociate CO and H2 can be derived from the presence of the [C I] 2-1. Photodissociation of CO can only occur at 912-1100 Å (van Dishoeck & Black 1988), so the absence of strong [C I] 2-1 emission in the outflow cavities of most protostars suggests that the radiation field in outflows does not produce sufficiently energetic radiation, but still heats the cavity walls to a few hundred K. This would also limit the shock velocities to <90 km s-1, since higher shock velocities produce CO and H2dissocating photons (Neufeld & Dalgarno 1989).
[C I] is detected in the inner 10
for HH 46, TMR 1 and
Ced 110 IRS 4 at levels
of 2 K km s-1. For
IRAS 12496-7650 and BHR 71, no
[C I] 2-1 was detected. The low emission in all
sources can be
accounted for by a C abundance of a few times 10-6
with respect
to H2. Such abundances can be maintainted by low
UV levels produced
by cosmic ray radiation (Flower
et al. 1994).
Table 4: CO isotopologue and [C I] properties at the source position.
Table 5: Inferred envelope properties from the DUSTY models.
7 Conclusions
In this paper, we have presented the first 12CO 6-5 and 7-6 maps of a sample of 8 low-mass protostars with a large range of luminosities, evolution and densities, as well as several isotopologue and [C I] observations. All observations have been carried out with the CHAMP+ instrument. The main conclusions of this paper are:
- Warm gas, as traced by 12CO 6-5 and 7-6, is present in all observed protostars at the central position. Three different origins of the warm gas emission are found: (i) the inner envelope heated passively by the protostellar luminosity; (ii) shocked gas in the outflow; and (iii) quiescent gas heated by UV photons. This latter mechanism, as detailed in Spaans et al. (1995) and in Paper I, generally dominates the extended high-J CO emission.
- Envelope models show that for HH 46 and Ced 110 IRS 4, passive heating of the envelope is insufficient to explain the observed 12CO 6-5, 7-6 and 13CO 6-5 lines, requiring heating of the envelope by UV photons even at the (0, 0) position.
- Photon heating of the cavity walls takes place on arcmin scales for the outflow cavities of several other Class 0 and Class I protostars, as seen at positions off-source of BHR 71, NGC 1333 IRS 2, HH 46 and L 1551 IRS 5. The necessary UV photons are created by internal jet shocks and the bow shock where the jet interacts with the ambient medium, in addition to the disk-star accretion boundary layer. The distribution of the quiescent CO 6-5 and 7-6 emission of BHR 71, with narrow emission stronger at larger distances from the source, confirms the hypothesis that UV photons necessary for the heating can originate both mechanisms. This suggests that photon heating is present in all outflows.
- The lack of [C I] 2-1 emission in the outflows constrains the production of energetic CO dissociative photons in the shocks. The observed [C I] emission at the source position can be accounted for by a low atomic C abundance that is maintained by cosmic ray induced UV photodissocation of CO.
- Shocked 12CO 6-5 and 7-6 gas only exists in large quantities in flows of more massive sources (NGC 1333 IRAS 2, BHR 71, HH 46 and RCrA IRS 7), while low-mass flows do not show much shocked gas that emits in the 12CO 6-5 and 7-6 lines. Within the proposed model of Bachiller & Tafalla (1999), the outflows of Class I are more evolved and are driven with much less energy, producing much weaker shocks. This is also reflected in the decreasing maximum velocity of 12CO 6-5 with lower outflow force.
- Kinetic temperatures of
100 K are found for the molecular gas in most flows studied here. Such temperatures agree with expected conditions of jet driven flows modelled by (Hatchell et al. 1999). Only the flows of L 1551 IRS 5 and IRAS 12496-7650 are much colder (<50 K), in agreement with the ``fossil'', empty nature of the flows.
Table 6: 13CO model predictions.
- The very strong intensities at all positions of RCrA IRS 7, an order of magnitude higher than can be produced by passive heating, must be due to a significant PDR region near the source. Likely, RCrA itself heats the outside of the RCrA IRS 7 envelope and cloud region.

Table 7: Outflow kinetic temperature estimatesa.
AcknowledgementsT.v.K. and astrochemistry at Leiden Observatory are supported by a Spinoza prize and by NWO grant 614.041.004. The staff at APEX and many members of the Bonn submillimeter group are thanked for the excellent support during observations. CHAMP+ is constructed with funds from NWO grant 600.063.310.10. We thank Ronald Stark for continued support of the CHAMP+ project.
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Footnotes
- ... gas
- Fits files of data used in constructing maps are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/507/1425
- ... (APEX)
- This publication is based on data acquired with the Atacama Pathfinder Experiment (APEX). APEX is a collaboration between the Max-Planck-Institut für Radioastronomie, the European Southern Observatory, and the Onsala Space Observatory.
- ... package
- CLASS is part of the GILDAS reduction package.
See http://www.iram.fr/IRAMFR/GILDAS for more information. - ...
- Note that this power law index is not the same as the power
law index p for the normalized 850
m radial emission profile.
All Tables
Table 1: Adopted Champ+ settings.
Table 2: The sample of sources observed with CHAMP+.
Table 3: Properties of the 12CO linesa.
Table 4: CO isotopologue and [C I] properties at the source position.
Table 5: Inferred envelope properties from the DUSTY models.
Table 6: 13CO model predictions.
Table 7: Outflow kinetic temperature estimatesa.
All Figures
![]() |
Figure 1: Maps of CO 6-5 ( top row) and CO 7-6 ( bottom row) of NGC 1333 IRAS 2. The left-most image shows the total integrated intensity over the line. The middle figures show the outflow contributions from the red ( dashed lines) and blue ( solid lines) outflow. Contours are in increasing levels of 4 K km s-1 for both transitions. The outflow contributions are calculated by only including emission greater or smaller than +/-1.5 km s-1 from the central velocity. The right-most image at the top row shows the 12CO spectra at the central position. |
Open with DEXTER | |
In the text |
![]() |
Figure 2: Maps of CO 6-5 ( top row) and CO 7-6 ( bottom row) of L 1551 IRS 5. The left-most image shows the total integrated intensity over the line. The middle figures show the outflow contributions from the red ( dashed lines) and blue ( solid lines) outflow. Contours are in increasing levels of 0.5 K km s-1 for both transitions. The outflow contributions are calculated by only including emission greater or smaller than +/-1.5 km s-1 from the central velocity. The right-most image at the top row shows the 12CO spectra at the central position. |
Open with DEXTER | |
In the text |
![]() |
Figure 3: Maps of CO 6-5 ( top row) and CO 7-6 ( bottom row) of TMR 1. The left-most image shows the total integrated intensity over the line. The middle figures show the outflow contributions from the red ( dashed lines) and blue ( solid lines) outflow. Contours are in increasing levels of 1 K km s-1 for both transitions.The outflow contributions are calculated by only including emission greater or smaller than +/-1.5 km s-1 from the central velocity. The right-most image at the top row shows the 12CO spectra at the central position, while the right-most image at the bottom row shows the spectra of the observed isotopologues and [C I] 2-1 at the central position. |
Open with DEXTER | |
In the text |
![]() |
Figure 4: CO 6-5 ( left) CO 7-6 ( middle) maps and spectra of the central position of HH 46. The left-most image shows the total integrated intensity over the line. The middle figures show the outflow contributions from the red ( dashed lines) and blue ( solid lines) outflow. Contours are in increasing levels of 2 K km s-1 for CO 6-5 and 3 K km s-1 for CO 7-6. The outflow contributions are calculated by only including emission greater or smaller than +/-1.5 km s-1 from the central velocity. The right-most image at the top row shows the 12CO spectra at the central position, while the right-most image at the bottom row shows the spectra of the observed isotopologues and [C I] 2-1 at the central position (see also Paper I). |
Open with DEXTER | |
In the text |
![]() |
Figure 5: Maps of CO 6-5 ( top row) and CO 7-6 ( bottom row) of Ced 110 IRS 4. The left-most image shows the total integrated intensity over the line. The middle figures show the outflow contributions from the red ( dashed lines) and blue ( solid lines) outflow. Contours are in increasing levels of 3 K km s-1 for both transitions. The outflow contributions are calculated by only including emission greater or smaller than +/-1.5 km s-1 from the central velocity. The right-most image at the top row shows the 12CO spectra at the central position, while the right-most image at the bottom row shows the spectra of the observed isotopologues and [C I] 2-1 at the central position. |
Open with DEXTER | |
In the text |
![]() |
Figure 6: Maps of CO 6-5 ( top row) and CO 7-6 ( bottom row) of BHR 71. The left-most image shows the total integrated intensity over the line. The middle figures show the outflow contributions from the red ( dashed lines) and blue ( solid lines) outflow. Contours are in increasing levels of 10 K km s-1 for CO 6-5 and 5 K km s-1 for CO 7-6. The outflow contributions are calculated by only including emission greater or smaller than +/-1.5 km s-1 from the central velocity. The right-most image at the top row shows the 12CO spectra at the central position, while the right-most image at the bottom row shows the spectra of the observed isotopologues and [C I] 2-1 at the central position. |
Open with DEXTER | |
In the text |
![]() |
Figure 7: Maps of CO 6-5 ( top row) and CO 7-6 ( bottom row) of IRAS 12496-7650. The left-most image shows the total integrated intensity over the line. The middle figures show the outflow contributions from the red ( dashed lines) and blue ( solid lines) outflow. Contours are in increasing levels of 3 K km s-1 for both transitions. The outflow contributions are calculated by only including emission greater or smaller than +/-1.5 km s-1 from the central velocity. The right-most image at the top row shows the 12CO spectra at the central position, while the right-most image at the bottom row shows the spectra of the observed isotopologues and [C I] 2-1 at the central position. |
Open with DEXTER | |
In the text |
![]() |
Figure 8: Maps of CO 6-5 ( top row) and CO 7-6 ( bottom row) of RCrA IRS 7a. The left-most image shows the total integrated intensity over the line. The middle figures show the outflow contributions from the red ( dashed lines) and blue ( solid lines) outflow. Contours are in increasing levels of 10 K km s-1 for both transitions. The outflow contributions are calculated by only including emission greater or smaller than +/-8 km s-1 from the central velocity. The right-most image at the top row shows the 12CO spectra at the central position. |
Open with DEXTER | |
In the text |
![]() |
Figure 9:
Spectra of 12CO 6-5 over an area of
|
Open with DEXTER | |
In the text |
![]() |
Figure 10:
Spectra of 12CO 6-5 over an area of
|
Open with DEXTER | |
In the text |
![]() |
Figure 11:
Spectra of 12CO 6-5 over an area of
|
Open with DEXTER | |
In the text |
![]() |
Figure 12:
Spectra of 12CO 6-5 over an area of
|
Open with DEXTER | |
In the text |
![]() |
Figure 13: 13CO 6-5 integrated intensity maps of BHR 71 ( upper left), Ced 110 IRS 4 ( upper middle), HH 46 ( upper right), IRAS 12496-7650 ( lower left) and TMR 1 ( lower middle). |
Open with DEXTER | |
In the text |
![]() |
Figure 14: [C I] 2-1 integrated intensity maps of Ced 110 IRS 4 ( left) and TMR 1 ( right). Note that the TMR 1 data suffer from a de-rotation problem in the calibrator data and are subject to change. |
Open with DEXTER | |
In the text |
![]() |
Figure 15:
The SEDs and radial profiles at 850 |
Open with DEXTER | |
In the text |
![]() |
Figure 16:
The contribution of the envelope to CO lines at the source position
with |
Open with DEXTER | |
In the text |
![]() |
Figure 17:
|
Open with DEXTER | |
In the text |
![]() |
Figure 18: Line wings of CO 6-5 ( solid) and CO 3-2 ( dashed) for HH 46 (red wing at central position and in the red outflow), Ced 110 IRS 4 (blue at the central position), RCrA IRS 7A (red and blue at the central position). |
Open with DEXTER | |
In the text |
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