A Project of the National Radio Astronomy Observatory
We have discovered and mapped a compact (= 80" in extent) outflow from the gas-rich protostar, S68N, with newly combined single-dish (Haystack) and interferometer (BIMA) data. The outflow momentum flux is =4.8x10-4 solar masses km s-1 yr-1, or about two orders of magnitude larger than the average momentum flux for Class I objects, and one order of magnitude larger than the average momentum flux for Class 0 objects (e.g., Bontemps et al. 1996). Such a high momentum flux is a newly-found indicator of the extreme youth of Class 0 protostars. Our new CS J=2~1 results, combined with previous H2CO data, suggest the simultaneous occurrence of infall and outflow in S68N (Hurt, Barsony, & Wootten 1996; McMullin et al. 1994).
We have also mapped the S68N region at 450microns & 850microns, with SCUBA on the JCMT with 7" and 14" resolutions, respectively. In addition to S68N, the SCUBA maps also detect swept-up dust associated with the redshifted outflow lobe, as well as the Class I source, SMM5, 45" to the East. We have discovered a new protostellar source 13" to the NE of S68N, but only marginally detected a previously known 1.1 mm continuum peak, associated with submillimeter H2CO emission, 27" NW of S68N (Casali, Eiroa, & Duncan 1993; Barsony, Wootten, & Hurt, unpublished data). This 1' region surrounding S68N in the Serpens cloud core (d=310 pc) contains a pre-protostellar core, a possible proto-binary, and a Class I protostar. We plan future line radiative transfer modelling, combined with higher resolution interferometric imaging of this source, to advance our understanding of cloud fragmentation processes leading to multiple system formation.
Observations of the J=2-1 line of CS have been combined (interferometric data from BIMA and single telescope data from Haystack) to form a color representation of S68N illustrating its outflow (top picture). A color map of the Haystack data on the outflow only, which is identical in scale (spatial extent) to the combined outflow image is shown in the bottom panel. Beamsizes are indicated. Positions marked include the H2O water maser, the CS peak determined from BIMA data alone, the position of S68N from the Hurt & Barsony HIRES paper, and the northern 1mm peak of Eiroa & Casali, which corresponds to a possible northern submm H2CO peak. In this representation, the blueshifted and redshifted intensities were integrated over the same velocity range as a previous outflow map based solely on Haystack data, namely from 2 - 6.5 km/s and 10.5 - 15 km/s. The picture on the bottom shows the combined Haystack and BIMA data.
A postscript l,v map of the Haystack data. The 0 position corresponds to the H2O maser, and the position angle is through the major axis of the outflow, as defined from the outflow lobes seen in the combined Haystack & BIMA data.
This map is interesting because it shows 4 features of interest seen in
the Haystack+BIMA outflow map:
There are two "fingers" of redshifted emission seen at 2 different velocities
(~ 11 & 12 km/s). The higher-velocity finger corresponds to the redshifted
emission closer to the H2O maser, and the lower-velocity finger corresponds
to the blob which is further away. The blueshifted emission is somewhat
different --- the two "fingers" are at essentially the same velocity (~5.5 km/s)
one is about 20" northwest of the H2O maser, and the other is about 40" along
the flow axis, right on top of the 1mm/H2CO peak labelled "1MM_N" in the
outflow map of the combined data.
This map makes use of the combined data (the first l,v map was produced
from the Haystack data alone). I didn't try this at first, since the BIMA
data are so noisy compared to the Haystack data, but if the velocity
resolution is 'degraded' to 1 km/s (which works fine for outflow), the map
is quite striking. You will notice a biconical shape to the outflow, similar
to some of the more recent wind-driven shell models (eg. Li & Shu 1996).
There are two velocity gradients, one steep, which would correspond to the
near side of the blue lobe and the far side of the red lobe, the other shallow,
which would correspond to the reverse. An alternative explanation would be two
outflow episodes, which might be more consistent with the combined position-
position map. In any case, the l,v plot doesn't really look much like synthetic
plots I've seen for the popular "jet-driven bow shock" models in
IAU 182
HH Flows & the Birth of Low Mass Stars --- the Chamonix conference last Jan.).
We have to be careful,
though, since these models have all been computed for CO, and the CS gas only
traces the densest parts of the outflow. It would be interesting to do for
CS what Cabrit & Bertout did for CO line formation in molecular outflows
several years back, perhaps not for this paper though. Claude Bertout mentioned
we might borrow their code and make the appropriate changes for CS. I thinl
the "dense gas tracers" hold some promise for helping to distinguish between
present outflow models.
The new JCMT 450m map is shown in the greens and reds, with the Kband image showing the DEOS described by Hodapp et al. ApJ 468, 861 (1996) in blues. On the east, IRS53 shows the appearance of the blue lobe of a bipolar flow (to our knowledge, molecular motion has not been defined in this region) just south of the submillimeter continuum knot known as SMM5.
The new JCMT 450m map is shown in greyscale on the left, with the Kband image showing the DEOS described by Hodapp et al. ApJ 468, 861 (1996) in greyscale on the right.
The new JCMT 450m map with three pointings of OVRO superposed--30" circles at pointing centers in email file. These are the pointings planned in 1998.
The JCMT 450m map with new suggested pointings of OVRO superposed--30" circles at pointing centers in email file. These are the pointings planned in 1999.
The IRAM 30m map of the integrated line center emission from the 145 GHz J=2 K=0 line with new suggested pointings of OVRO superposed--30" circles at pointing centers in email file. These are the pointings planned in 1999. While the line center is heavily self-absorbed, most of the emission lies in the center beam. The IRAM beam is 18" at 145 GHz. Unpublished data from Mangum and Wootten.
The CSO 10.6m map of the integrated line center emission from the 362 GHz J=5 K=0 line with new suggested pointings of OVRO superposed--30" circles at pointing centers in email file. These are the pointings planned in 1999. There is no self-absorption in this line; almost all of the emission lies in the center beam, which is 20" at 362 GHz. Unpublished data from Barsony, Hurt and Wootten.
The CSO 10.6m map of the integrated emission from the 365 GHz J=5 K=2 line with new suggested pointings of OVRO superposed--30" circles at pointing centers in email file. These are the pointings planned in 1999. There is no self-absoprtion in this high excitation line; almost all of the emission lies in the center beam, which is 20". Some emission may lie to the NW, but the significance of this apparent feature was not verified in JCMT dust maps. Unpublished data from Barsony, Hurtand Wootten.
| This is the figure for the BIMA proposal . |
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