Free Access
Volume 496, Number 1, March II 2009
Page(s) 153 - 176
Section Interstellar and circumstellar matter
DOI https://doi.org/10.1051/0004-6361:200811096
Published online 14 January 2009

Online Material

Appendix A: Description of the H2 outflows in Orion A

Here we give a brief description of the H2 flows tabulated in Tables 2 and 3, relating each jet to its probable driving source and associated dense core (as listed in Tables 2 and 3). We focus on the newly-discovered ``DFS'' H2 flows, though we also discuss ``SMZ'' flows were our PM measurements and/or comparison with 1200 $\mu $m data help identify the driving source (see Sta02 for additional information on the SMZ jets).

In this section we also present continuum-subtracted H2 2.122 $\mu $m images for the DFS H2 flows (most of the SMZ jets are labelled in the figures in the main text; or see Sta02). Note that the micro-stepped WFCAM images have in these Appendix figures only been binned over 2 $\times$ 2 pixels, to a plate scale of 0.4 $^{\prime\prime}$, to improve signal-to-noise but also to retain spatial resolution. In each figure we mark the positions of Spitzer-identified protostars and label prominent HH objects.

A.1 OMC 2/3 and NGC 1977 (-4.3$^{\circ }$ ${> \delta >}$ -5.4$^{\circ }$)

A.1.1 SMZ 1 to SMZ 5 and DFS 101

At the northern end of Orion A, in addition to the five H2 flows identified by Sta02 (SMZ 1 to SMZ 5), we note the new, curving H2 flow, DFS 101, situated $\sim $15$^\prime $ to the northwest of Haro 5a/6a (Fig. A.1a). Although we have no (sub)millimetre observations in this region, the outflow source is clearly identified by Spitzer as a protostar. Indeed, Spitzer IRS sources are identified for all six H2 flows; the sources of jets SMZ 3, 4 and 5 are also associated with a chain of dust cores. SMZ 3 is particularly impressive and may in fact comprise multiple flows, driven by two or more of the Spitzer protostars in this region.

A.1.2 SMZ 6 to SMZ 10 and DFS 102

The prominent H2 jets labelled SMZ 6 and SMZ 9 by Sta02 are centred on MAMBO/SCUBA cores and a number of Spitzer protostars (see Figs. 2 and 3 in the main body of the paper). SMZ 6 is associated with the bipolar nebula and candidate Fu Ori source Haro 5a/6a. The western lobe of the flow is delineated by a faint H2 bow situated $\sim $3$^\prime $ to the west; the parsec-scale jet may also be associated with HH 41, HH 42, HH 128 and HH 129 (Reipurth et al. 1997). The reddened source of this outflow is partially visible to the east of the band of obscuration that separates the two lobes of the nebula.

IRS 10 is enveloped in a conical nebula that opens out toward the west. Although this source is well aligned with the SMZ 9 flow axis, high-resolution CO maps reveal a compact bipolar CO outflow centred on IRS 10 that is instead aligned with SMZ 10 (Yu et al. 2000; Williams et al. 2003). IRS 9 is perhaps the best candidate driving source for SMZ 9 (which is also associated with a high-velocity CO lobe). The PMs of the H2 knots in SMZ 9, which are generally moving westward with a velocity of 100-150 km s-1, certainly support this interpretation.

HH 42 lies about 5$^\prime $ east of Haro 5a/6a. Bright H2 emission is detected from this object. We also find a candidate outflow source along the flow axis (IRS 102), and therefore identify these features with a new H2 jet, DFS 102 (Fig. A.1c).

The PM of the nebulous, bow-shaped H2 feature SMZ 8 is unfortunately inconclusive, and this flow has no obvious progenitor. The faint though well-collimated SMZ 7 jet is associated with a faint conical nebula and Spitzer protostar (IRS 7).

\end{figure} Figure A.1:

Continuum-subtracted H2 2.122 $\mu $m images of DFS 101-105. Spitzer-identified young stars are marked with circles (protostars) and triangles (disc-excess sources).

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A.1.3 SMZ 11 to SMZ 20 and DFS 103

Based on PMs, the source of SMZ 11 (and SMZ 13) probably lies mid-way along this chain of H2 knots. A reddened protostar (IRS 11) is visible in the colour images in Fig. 2 which is also associated with a molecular core.

SMZ 14 and SMZ 16 may be the lobe and counter-lobe of another large flow. The PM of the outer conical bow in SMZ 14 is toward the north-northeast, as expected.

IRS 17 is a possible candidate for the spectacular H2 jet SMZ 17 - it coincides with the peak in the 1200 $\mu $m map and a dark lane in our colour image in Fig. 2 - although there are a number of candidate protostars in this nebulous region. SMZ 18 may be part of the same outflow, or may indeed be an unrelated finger or ``bullet''.

SMZ 12, SMZ 15, SMZ 19 and SMZ 20 are compact features or small chains of H2 knots. Sources are identified for each outflow.

DFS 103 is a pair of faint knots close to a Spitzer disc source (Fig. A.1d).

A.1.4 SMZ 21 to SMZ 28, DFS 104 and DFS 105

Moving southward through the OMC 2/3 region, as we approach the brighter regions in the Orion nebula, the identification of outflow source candidates becomes more difficult. Even so, reddened sources are identified for all of the H2 flows.

The chain of knots and bow-shocks that comprise SMZ 23 are likely driven by one of the protostars to the north, possibly the Spitzer source/dust core IRS 23. The leading bow in SMZ 23 does appear to be moving southward with a PM of $\sim $100 km s-1, consistent with its morphology and this interpretation.

Features SMZ 21 and SMZ 22 may be part of yet another H2 flow, driven by the disc-excess source IRS 21. Both have PMs directed southward.

SMZ 24 has well-defined PMs directed away from the protostar IRS 24; the tangential velocities of the features in SMZ 25 are imprecise, though IRS 25 remains a good source candidate.

SMZ 26-28 are H2 features identified by Sta02 that lie along the western edge of the Orion Nebula and may in some cases be ``Orion Bullets''; we are unable to identify candidate outflow sources or dust cores because of the bright emission associated with this region.

DFS 104 are faint H2 objects near a Spitzer disc source; DFS 105 is a faint arc located southwest of the ONC. Both have candidate driving sources and are shown in Fig. A.1.

\end{figure} Figure A.2:

Continuum-subtracted H2 2.122 $\mu $m images of DFS 106-110 and DFS 114. Protostars and disc-excess sources are marked. DFS 108 coincides with the irradiated jet features HH 541 and HH 882.

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A.2 The OMC 4/5 region (-5.4$^{\circ }$ ${> \delta >}$ -6.3$^{\circ }$)

A.2.1 SMZ 29 to SMZ 36 and DFS 106 to DFS 112

The H2 flow features just to the south of the ONC are generally faint and compact. The newly-identified outflows are shown in Figs. A.2-A.3.

DFS 106, DFS 107 and DFS 108 all have candidate driving source; DFS 109 comprises two well-defined bow shocks east of the chain of dense cores; DFS 110 is a cluster of H2 knots to the west of the main L 1641 ridge. DFS 110 is beyond the bounds of the MAMBO and SCUBA observations, though candidate sources are evident in the Spitzer data; this cluster of knots is also associated with the T Tauri star Haro 4-145 and a molecular outflow (Fig. A.2d).

DFS 111 and DFS 112 are compact, bow-shaped H2 features with candidate sources in the Spitzer sample (Figs. A.3a and b).

We have attempted to measure PMs for the knots in DFS 107, DFS 108, DFS 109 and DFS 111, as well as SMZ 31 to SMZ 36 (SMZ 29 and SMZ 30 are faint, diffuse features, though SMZ 29 is clearly driven by a nebulous K-band source, dust core and Spitzer protostar). The PM results are in many cases marginal since most of the features are rather faint and/or diffuse. Variability will also affect our PM measurements. This probably explains why only DFS 109, SMZ 31 and SMZ 35 have PMs that are consistent with them being driven by their identified progenitors (in this case IRS 109, IRS 31 and IRS 35, respectively).

A.2.2 SMZ 37 to SMZ 44, DFS 113 and DFS 114

Moving south through the NGC 1980 region toward OMC 5, there are a number of H2 knots around the three Spitzer protostars/molecular cores, IRS 38, IRS 39 and IRS 41 (Fig. 5). It seems likely that all three embedded sources have H2 flows. IRS 41 probably drives the distant bow shock SMZ 41 to the south; similarly, IRS 40 may drive the bow shock SMZ 40.

PMs for the H2 features in the orthogonal flows SMZ 38 and SMZ 39 confirm the proposed associations with their Spitzer protostars; the PMs of SMZ 37, SMZ 40 and SMZ 41 are unfortunately inconclusive or below the errors.

SMZ 42 represents a classic example of low-mass star formation (Fig. 5). It consists of a collimated, knotty H2 jet terminating in a sweeping H2 bow shock. A fainter bow equidistant from the source marks the end of the counter-lobe. The Spitzer-identified outflow source, IRS 42, is also coincident with a small dust core.

SMZ 43 is associated with the variable flare star V1296 Ori and a compact peak at 1200 $\mu $m; SMZ 43 may be a Photo-Dissociation Region (PDR) rather than an outflow. SMZ 44 is a faint H2 bow and cavity that we tentatively associated with the Spitzer disc source IRS 44.

DFS 113 is a very faint bow-shaped feature $\sim $3.5$^\prime $ south of IRS 113 (Fig. A.3c), while DFS 114 is a group of knots and filaments a few arcminutes west of DFS 110 and Haro 4-145 (labelled in Fig. A.2d).

\par\end{figure} Figure A.3:

Continuum-subtracted H2 2.122 $\mu $m images of DFS 111-113, DFS 115 and DFS 116 (better known as HH 33/40). Protostars and disc-excess sources are marked.

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\end{figure} Figure A.4:

Continuum-subtracted H2 2.122 $\mu $m images of DFS 117 (HH 83 and its distant counter bow-shock), DFS 118, DFS 119 and DFS 120. Protostars and disc-excess sources are marked.

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\end{figure} Figure A.5:

Continuum-subtracted H2 2.122 $\mu $m images of DFS 121 (HH 36), DFS 122 (HH 89), DFS 123 and DFS 124. Protostars and disc-excess sources are marked.

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A.3 L 1641-N and NGC 1999 (-6.3$^{\circ }$ ${> \delta >}$ -7.0$^{\circ }$)

L 1641-N and NGC 1999 are associated with many well-known HH objects (HH 1/2, HH33/40, HH 34, etc.), most of which are labelled in Figs. 6-8 in the main text.

A.3.1 SMZ 45 to SMZ 54, SMZ 57, SMZ 58, DFS 115 and DFS 118

Candidate H2 outflow sources are identified for SMZ 45 and SMZ 46, though not for the chain of diffuse knots in SMZ 47 (see Sta02 for details) or for the elongated knots in SMZ 48 (HH 299).

The parsec-scale H2 flow SMZ 49 is driven by a source in the L 1641-N cluster. There are five Spitzer protostars in L 1641-N (Fig. A.4b). IRS 49 is best aligned with SMZ 49 and with the PM vectors of features along this axis (Gålfalk & Olofsson 2007). However, IRS 49 is offset by $\sim $10 $^{\prime\prime}$ to the east-southeast of the brightest peak in 1200 $\mu $m emission, which coincides with a second source, IRS 53. This embedded protostar probably drives the H2/CO outflow SMZ 53 (see also Stanke & Williams 2007). The other sources in the cluster may also power some of the H2 features in L 1641-N.

SMZ 50 is possibly driven by the disc source IRS 50 and, like Gålfalk & Olofsson (2007), we associate SMZ 51 (HH 301) with another Spitzer source, the protostar IRS 51 (Figs. A.3d and A.4b). SMZ 52 is a faint arc, possibly part of the DFS 115 flow.

SMZ 58 is a nice example of a bright, bipolar H2 flow associated with a Spitzer protostar and a compact, dense core. SMZ 57 is a series of H2 knots with no obvious source; it is located $\sim $1.5$^\prime $ north of SMZ 58.

\end{figure} Figure A.6:

Continuum-subtracted H2 2.122 $\mu $m images of DFS 125 (HH 127), DFS 126, DFS 127 and DFS 128. Protostars and disc-excess sources are marked.

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Finally, we identify two other H2 flows in L 1641N, DFS 115 and DFS 118. DFS 118 comprises compact arcuate features that are associated with a bipolar CO outflow (Stanke & Williams 2007); this flow is driven by IRS 118 (Fig. A.4b). A small cluster of protostars $\sim $3$^\prime $ south of L 1641-N, known as Strom 11, includes the source of the other outflow, DFS 115 (Fig. A.3d).

A.3.2 HH 34 (SMZ 55 and SMZ 56), HH 33/40 (DFS 116) and HH 83/84 (DFS 117)

To the west of L 1641-N, three Spitzer protostars are identified in the vicinity of the archetypal jet HH 34. HH 34-IRS itself (IRS 55) coincides with the local peak in 1200 $\mu $m dust emission; a second source, IRS 56, also appears to drive a collimated molecular jet.

Roughly 10$^\prime $ to the north, HH 40 is also identified as a Spitzer protostar, which we label IRS 116. As noted in the main text, this source could be powering HH 33 and HH 40 (Fig. A.3e).

Further west, DFS 117 comprises a collimated optical jet (HH 83) and a group of arcuate H2 knots 10.5$^\prime $ to the south-east (HH 84). We note that HH 84 could be driven by a neighbouring protostar or disc source (Fig. A.4a). HH 83-IRS is outside the bounds of the SCUBA, MAMBO and two of the four Spitzer IRAC bands; in the remaining two bands, this object has a colour consistent with it being a disc-excess source.

A.3.3 HH 1/2, SMZ 59 to SMZ 65, DFS 119, DFS 121, and DFS 124

SMZ 59 is the well-known molecular outflow V380 Ori-NE (e.g. Davis et al. 2000); the source is associated with a compact molecular core and appears as a point source at 4.5 $\mu $m and 24 $\mu $m. However, it was rejected from the Spitzer YSO catalogues as a possible extragalactic contamination because it is rather faint. Even so, its colours are consistent with those of a protostar.

The outflows in the vicinity of HH 1/2 (SMZ 60-SMZ 65) are well documented (e.g. Hester et al. 1998; Reipurth et al. 2000). There are a number of Spitzer YSOs and dust cores in NGC 1999 (near HH 1/2); most of the SMZ flows likely have candidate driving sources. The VLA source known to drive HH 1/2 (SMZ 64) lies in the wings of a nearby, brighter source, and so does not appear in the Spitzer YSO catalogues. To the seven H2 flows identified by Sta02 in this region we add DFS 121 (HH 36), which is probably driven by the Spitzer protostar just to the south of the embedded HH 1/2 VLA source and its dense core (Fig. A.5a).

DFS 119 is a compact knot associated with a Spitzer protostar, (Fig. A.4c). DFS 124 is a bow-shaped feature $\sim $6$^\prime $ south of HH 2 (Fig. A.5c). It has a PM consistent with IRS 124 being the driving source.

A.3.4 DFS 120, DFS 122, DFS 123, DFS 125 and DFS 126

Five new H2 flows are identified to the southeast and southwest of HH 1/2. DFS 120 is a faint compact feature with no Spitzer source (Fig. A.4d). DFS 122 and DFS 125 are associated with HH 89 and HH 127, respectively (Figs. A.5b and A.6a); the former is driven by a nebulous Spitzer protostar, IRS 122

DFS 123 is a remarkable new H2 flow, though it has no HH counterpart nor candidate driving source (Fig. A.5d). DFS 123 extends over at least 8.5$^\prime $.

The bright H2 bow in DFS 126 (Fig. A.6d; see also Fig. 11) could be an extension of the HH 38/43/68 flow, although the orientation of the bow shock and the location of the protostar labelled IRS 126 suggests the presence of a new flow.

Unfortunately these five outflows are beyond the bounds of the MAMBO and SCUBA observations.

\end{figure} Figure A.7:

Continuum-subtracted H2 2.122 $\mu $m images of DFS 129, DFS 130, DFS 131 and DFS 132. Protostars and disc-excess sources are marked.

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A.4 L 1641-C ( ${-7.0^\circ > \delta > -7.5^\circ }$)

A.4.1 SMZ 66 and HH 38/43/64 (SMZ 67 and SMZ 68)

In H2 emission we detect only one jet associated with the young cluster L 1641-C (Fig. 10). Based on morphology alone, SMZ 66 is probably driven by the protostar labelled IRS 66, which is the only source in the region that is associated with a sizable dust core.

SMZ 67 is better known as the parsec-scale flow HH 38/43/64 (Fig. 11). The source of this flow, and the neighbouring jet SMZ 68, are both retrieved from the Spitzer data. IRS 67 and IRS 68 are also associated with molecular cores. If we include DFS 126 in the HH 38/43/64 flow (though see the comments in the previous section), the total length of this system is a remarkable 25$^\prime $ (3.3 pc at a distance of 450 pc).

A.4.2 SMZ 69, SMZ 70, DFS 127, DFS 128 and DFS 129

Approximately 6$^\prime $-8$^\prime $ south of L 1641-C, SMZ 69, SMZ 70, and DFS 129 (previously identified as the eastern end of SMZ 69; see Fig. A.7d) are driven by three of the young stars in the region.

DFS 127 and DFS 128 are faint, compact H2 features off the main L 1641 axis (Figs. A.6b and c). DFS 127 is associated with a Spitzer protostar, IRS 127.

A.4.3 SMZ 71 to SMZ 76 and DFS 130 to DFS 133

SMZ 71 is a faint, knotty H2 jet $\sim $10$^\prime $ northwest of Haro 4-255 (midway between L 1641-C and L 1641-S). The central source is recovered by Spitzer.

SMZ 72 and SMZ 73 are orthogonal outflows in the vicinity of Haro 4-255 (Fig. 12). They appear to be associated with HH objects 469 and 470, respectively (Aspin & Reipurth 2000). Two candidate sources for SMZ 72/HH 469 are detected in the Spitzer data. These coincide with a dense molecular core. However, although IRS 72a is better aligned with the peak of the 1200 $\mu $m emission, IRS 72b coincides with the only bright VLA source in the region, Haro 4-255 FIR (Anglada et al. 1998). We therefore associate IRS 72b with SMZ 72, though add that both sources may contribute to the excitation of the HH/H2 features. SMZ 73/HH 470 is almost certainly driven by the bright K-band source/T Tauri star Haro 4-255. Haro 4-255 is associated with a compact optical jet (Aspin & Reipurth 2000) and faint 1200 $\mu $m dust continuum emission.

SMZ 74 and SMZ 75 are compact groups of H2 knots 6$^\prime $-8$^\prime $ north of Re50. Their morphologies and PMs suggest that they are powered by one of a number of Spitzer protostars located 7$^\prime $-8$^\prime $ to the southwest, although precise associations are difficult to make.

SMZ 76 is a spectacular curving H2 flow a few arcminutes north of Re50. The PMs of the two elongated arcs of H2 emission that comprise SMZ 76 are generally directed towards the east, again as one would expect if they were being driven by a source situated to the west or west-southwest. Stanke et al. (2000) discuss this region in detail, and identify a millimetre peak (which they label L 1641-S3 MMS1) as the location of the likely source. This embedded source was detected by MAMBO and Spitzer and is identified as a candidate protostar (IRS 76).

Roughly 20$^\prime $ southwest of SMZ 76 we discover a similarly large H2 feature, DFS 132 (Figs. 12 and A.7d). The overall morphology of this feature suggests motion away from IRS 76. If SMZ 76 and DFS 132 are part of the same flow, then the total length is at least 35$^\prime $ (4.6 pc). However, without proper motion data or, preferably, a large-scale (sub)millimetre outflow map in CO, this association remains uncertain.

DFS 133 is a faint, twisting chain of H2 emission features between SMZ 76 and DFS 132 (Fig. A.8a). First noted by Stanke (2000), it is possibly driven by the protostar/dust core to the north labelled IRS 133.

Two additional H2 flows, DFS 130 and DFS 131, are presented in Figs. A.7b and c. DFS 130 is a well-defined bow shock with no identified driving source. DFS 131 is a chain of knots to the south of SMZ 76 that may represent an independent system. The PMs of these knots are well aligned along an axis that links DFS 131 with a MAMBO dust core and its associated Spitzer protostar IRS 131.

A.5 L 1641-S ( ${-7.5^\circ > \delta > -8.3^\circ }$)

A.5.1 DFS 134 to DFS 142

Finally, the region at the southern end of L 1641 is abundant with Spitzer-identified young stars and newly discovered H2 flows. We identify nine possible outflows, most of which have candidate Spitzer sources (note that the MAMBO and SCUBA observations do not extend this far south in L 1641).

DFS 138 is the most spectacular flow, comprising a collimated, bipolar jet and features that delineate sweeping bow shocks (Fig. A.9a). The outflow extends over 13.4$^\prime $ (1.8 pc) and appears to be driven by a Spitzer protostar.

Sources are also identified for DFS 136, DFS 137, DFS 141 and DFS 143 (see Figs. A.8 and A.10). DFS 135 is a collimated jet and bow shock that seems to be driven by a bright, near-IR source, though this star is not in our list of Spitzer disc sources or protostars (Fig. A.8c). DFS 139 is a faint, curving wisp of line emission - possibly a collimated jet (Fig. A.9b). DFS 143 is an extremely faint flow, though it is associated with a protostar (Fig. A.10a).

The remaining H2 features in the region are: the compact arcs that comprise DFS 134, the knotty feature DFS 142, and the parallel ``fingers'' of emission collectively labelled DFS 140 (Figs. A.8-A.10). However, none of these objects have an obvious Spitzer source.

\end{figure} Figure A.8:

Continuum-subtracted H2 2.122 $\mu $m images of DFS 133 to DFS 137. Protostars and disc-excess sources are marked.

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\end{figure} Figure A.9:

Continuum-subtracted H2 2.122 $\mu $m images of DFS 138, DFS 139 and DFS 140. Protostars and disc-excess sources are marked.

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\end{figure} Figure A.10:

Continuum-subtracted H2 2.122 $\mu $m images of DFS 141, DFS 142 and DFS 143. Protostars and disc-excess sources are marked.

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Appendix B: Proper motion measurements

The proper motions (PMs) of selected bright H2 knots have been measured. PMs are listed in Table B.1, where we use the knot nomenclature of Sta02 when referring to features within each SMZ or DFS outflow. An extensive catalogue of images, with the individual features labelled, is also available from Stanke (2000); an on-line version is available at http://www.eso.org/~tstanke/thesis/.

Although we did not measure PMs for every outflow common to the Sta02 data and the new WFCAM images, the number of objects analysed is considerable and therefore the sample represents a relatively unbiased survey of H2 knot PMs in low mass protostellar outflows.

Table B.1:   Proper Motions of H2 features.

The first and second epoch images were obtained with different instruments. Hence, the first epoch images were converted to the same pixel size as the WFCAM data; all results are therefore with respect to the WFCAM pixel scale of 0.2 $^{\prime\prime}$.

The PMs of knots and stars were measured using a cross-correlation method. For each region the first epoch image was registered with the corresponding second epoch image using a third-order polynomial fit to all detected stars in the field (the IRAF routines geomap and geotran were employed). Typical root-mean-square (rms) values for the fit were below 0.5 pixels, i.e. <0.1 $^{\prime\prime}$. The first epoch image was then shifted relative to the second epoch image in steps of 0.25 pixels (0.05 $^{\prime\prime}$) about a 5 $\times$ 5 pixel grid. At each position the total flux in a rectangular box surrounding a star or knot was determined from the product of the second and shifted-first epoch images. This total flux was recorded as the cross-correlation coefficient for a given star or knot at each relative shift between the images. The sizes of boxes around target features were manually determined in order to enclose the entire flux from each object. The process yields a set of correlation coefficients for each object ( $ccf=f({\rm shift}x, {\rm shift}y)$). We then determined manually the position of the maximum correlation coefficient using the center/moment command in the European Southern Observatory's MIDAS package. This position was recorded as the PM of the individual object. Finally, to determine the PM of the outflow knots, we subtracted the average PM of adjacent field stars. This ensures that any systematic effects (i.e. problems with the mosaicing in the 1st epoch images) were minimised.

The random errors, i.e. the uncertainties in the determination of the individual PMs of stars and bright knots, is very low. For reasonably bright stars the center/moment command determined the PM to an accuracy of up to 1/30th of a pixel (0.007 $^{\prime\prime}$). Even for faint stars, accuracies better than 0.1 pixels were attained. For extended and low signal-to-noise knots, the uncertainties can be slightly larger (0.1 pixel; 0.02 $^{\prime\prime}$). In situations where the position of the maximum correlation coefficient was uncertain, the center/moment command could not be used. These objects are flagged with status F = 2 in Table B.1, and should be viewed with caution.

The random motions of field stars represent the most significant source of error. We found that in most cases, between the two epochs, the PMs of the stars in our images was of the order of 0.35 pixels (0.07 $^{\prime\prime}$), i.e. much larger than the random errors associated with our method. With our epoch difference of 8-9 years, the PM of the field stars translates to almost 0.01 $^{\prime\prime}$/year (a typical value for field star PMs). The errors for the measured PMs of outflow knots therefore depends on the number of adjacent field stars used as a control sample, and the assumption that on average those stars move in random directions. We adopt a 1$\sigma $ error for the PMs of outflow features of 0.07 $^{\prime\prime}$$/\sqrt(N)$ (the contribution from the field stars) added in quadrature with 0.02 $^{\prime\prime}$ (the contribution from our method). Since a similar number of field stars were used in each region (between 8 and 20), the 3$\sigma $ error is typically 0.09 $^{\prime\prime}$ ($\pm$0.015 $^{\prime\prime}$) or 21 km s-1($\pm$3 km s-1).

The above assumes that H2 knot brightnesses and morphologies do not change between first and second-epoch observations: in many features this is clearly not the case. The contribution to the actual PM is difficult to determine generally, since it depends on the percentage increase of flux from the knot and where it occurs. Also, adjacent objects can influence the PM measurements, when the shifting of the first epoch image moves a knot onto a neighbouring object. If this object is brighter, then the actual distance to the neighbouring object is measured as the PM. We have therefore not measured PMs for targets that are within 2 $^{\prime\prime}$ of other objects. Finally, a gradient in the background emission can also lead to a measured PM which is not real. This can occur in regions with spatially variable nebulous emission or close to very bright stars. Hence, any PM pointing along the slope of the background emission should be treated with caution.

Below we briefly interpret the results outlined in Table B.1. We split the H2 outflows up into five sections, B.1 to B.5; PM vectors are drawn onto contour plots of most of the outflows in the corresponding five figures, Figs. B.1-B.5 (note that figures are not presented for all H2 flows).

B.1 OMC 3

The PMs of SMZ 8 to SMZ 18 are displayed in Fig. B.1.

B.1.1 SMZ 8

1-14A is the main H2 feature in this object, which we resolve into four peaks (A, An, A-s and Aw). However, the tangential velocities of these four peaks are randomly orientated so no overall PM is identified. 1-14B is a faint arc $\sim $50 $^{\prime\prime}$ southwest of A which appears to be moving eastward.

B.1.2 SMZ 9

1-18A and B are the brightest of many H2 knots (A-J) that comprise the SMZ 9 outflow. A and B are bow shocks at the western end of the flow that do indeed move westward. Features D-J are bright knots within bows midway between bows 1-18A/B and the proposed source, IRS 9. Although there is some scatter in PMs and velocities are low, all again appear to be moving westward, as expected.

B.1.3 SMZ 10

On morphological grounds 1-16A and 1-16B+C seem to be sections of bow shocks driven by IRS 10 toward the northeast; both knots are associated with a bipolar CO outflow. The modest PMs displayed in Fig. B.1 do not support this interpretation, however.

B.1.4 SMZ 11/13

This H2 flow comprises a north-south twisting chain of knots 1-22A to 1-22D that extends $\sim $1$^\prime $ northward to include knot 1-19A. 1-22A and 1-22B are the brightest features with the best-defined PMs; these move southward away from the protostar IRS 11, located midway between A and D. 1-22 C and D also move roughly southward, although these PMs are relatively uncertain. 1-19A appears to be moving northward away from IRS 11, so could certainly be part of the SMZ 11 flow.

B.1.5 SMZ 14

Knots 1-20A and 1-20B are possibly outer bows in a flow driven by IRS 14 (with SMZ 16 as the counter-lobe). Fainter features (1-25, 1-28 and 1-29) exist closer to the source, though we have no PM measurements for these objects. The PMs for 1-20 are roughly northward, as expected, though they are relatively uncertain.

B.1.6 SMZ 17/18

This spectacular flow comprises a bright outer bow 1-27A and a curving filament 1-27C+D. These delineate the northern and western edges of a cavity, respectively. 1-27B is a bright knot on the eastern side of the cavity that may be associated with a second flow (SMZ 18). The PMs of these features support excitation by one of the protostars to the south; we identify IRS 17 as the best candidate (see Fig. 2 and main text).

B.2 OMC 2 and OMC 4

The PMs of H2 features in OMC 2 (SMZ 21 to SMZ 25) are displayed in Fig. B.2; values for the remaining H2 flows in this section, SMZ 31-SMZ 36 and DFS 107, 108, 109 and 111, all of which are located in the OMC 4 region (south of OMC 1), are given in Table B.1.

B.2.1 SMZ 21/22

The knots 1-37A, B and C, previously identified with two separate H2 flows SMZ 21 and SMZ 22, probably form part of a single outflow. All three features have well-defined PMs to the south, away from IRS 21.

\end{figure} Figure B.1:

H2 image of OMC 3 with proper motion vectors marked for SMZ 8 (1-14), SMZ 9 (1-18), SMZ 10 (1-16), SMZ 11/13 (1-22), SMZ 14 (1-20) and SMZ 17/18 (1-27). The knot nomenclature follows Sta02 (see also Table B.1). Candidate outflow sources are labelled.

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B.2.2 SMZ 23

This H2 flow comprises a pointed, knotty bow (1-38A) and a collimated chain of much fainter knots (1-38B to E). Motion to the south is certainly implied by the flow morphology. However, the measured PMs are relatively uncertain, being heavily influenced by gradients in the background nebulosity. Even so, the source could still be near IRS 23, which is very well aligned with the flow axis.

B.2.3 SMZ 24

The PMs of the H2 knots along this collimated flow (1-40 A,B,C) clearly point to IRS 24 being the driving source; all features are essentially moving towards the southwest. 1-40A is the brightest and most compact feature; it is more-or-less coincident with the IRS source. 1-40A1 is the cap of a bow situated $\sim $20 $^{\prime\prime}$ south-west of the source, respectively. 1-40B and 1-40C comprise a knotty bow a further arcminute downwind.

B.2.4 SMZ 25

This flow comprises an outer bow shock (1-32A) and an H2 arc (1-39A) that presumably traces the eastern edge of a second bow located closer to the source. Knots B and C in each object are fainter sub-components. 1-39A has a PM consistent with motion towards 1-32A, so both are almost certainly part of the same outflow, with the source situated to the south-southeast. The remaining features in 1-32 and 1-39 exhibit low and/or random motions, so overall the results for this flow are inconclusive.

B.2.5 SMZ 31

3-9A and 3-9B are H2 knots in the northern lobe of a compact, bipolar flow centred on IRS 31. Both features seem to be moving toward the north-northwest, consistent with this association.

B.2.6 SMZ 32

The PMs of the faint H2 knots in this flow (3-8 north and south, and 3-10) are rather uncertain, although they do suggest that these features are part of the same north-south flow. The source location is uncertain.

B.2.7 SMZ 33

Knots 3-12A and 3-12C are compact H2 features with PMs roughly to the north/northwest. The association with IRS 33 is tentative.

\par\end{figure} Figure B.2:

H2 image of OMC 2 with proper motion vectors marked for SMZ 21/22 (1-37), SMZ 23 (1-38), SMZ 24 (1-40) and SMZ 25 (1-32, 1-39).

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\end{figure} Figure B.3:

H2 image of jets SMZ 37 (3-16, 3-17), SMZ 38 (4-1, 4-2, 4-3) and SMZ 39 (4-4 to 4-7) with proper motion vectors marked.

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\par\end{figure} Figure B.4:

Left: H2 images of features SMZ 40 (4-9), SMZ 41 (4-10) and DFS 124 (6-16) with PMs indicated. Right: H2 images of portions of the SMZ 49 outflow south of L 1641-N (5-23 and 6-4) with PM vectors marked.

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\end{figure} Figure B.5:

H2 images of features SMZ 74 (9-1, 9-2), SMZ 75 (9-3), SMZ 76 (9-4, 9-6) and DFS 131 (9-7) with proper motion vectors marked.

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B.2.8 SMZ 34

3-13A has a PM directed roughly northward, consistent with its association with the much fainter knot 3-13B.

B.2.9 SMZ 35

Knot 3-14 is a very compact feature $\sim $1$^\prime $ east-northeast of IRS 35. Its modest eastward PM is not inconsistent with this Spitzer protostar being the exciting source.

B.2.10 SMZ 36

This H2 flow comprises three very faint knots in a compact group, 3-15A, 3-15B and 3-15C; A is the brightest. They are aligned along a roughly northeast-southwest axis, although their PMs are inconclusive and Spitzer revealed no obvious candidate driving source.

B.2.11 DFS 107

This flow consists of a very faint though well-collimated H2 jet (3-7A) that points to a bright knot (3-7B). The protostar IRS 107 lies on the same axis, although the PM of 3-7B is toward this source (Table B.1), rather than away from it.

B.2.12 DFS 108

3-1A is a bright H2 knot in a region of diffuse nebulosity which may well influence the PM measurement. This probably explains why its PM appears to be to the east, ``toward'' the nearest Spitzer protostar (IRS 108).

B.2.13 DFS 109

The brightest H2 feature in this faint, collimated flow is knot 3-5. This bow-shaped knot has a well-defined PM to the east, consist with the Spitzer source/MAMBO core IRS 109 being the driving source.

B.2.14 DFS 111

Knot 3-11 appears to be a small H2 bow situated 10 $^{\prime\prime}$-20 $^{\prime\prime}$ northeast of a Spitzer disc source and a protostar. However, its relatively well-defined PM is towards both sources, so the association with either is questionable.

B.3 OMC 5 (the NGC 1980 region)

The PMs of the H2 features that comprise SMZ 37, SMZ 38 and SMZ 39 are displayed in Fig. B.3.

B.3.1 SMZ 37

3-16 (A,B) and 3-17 (A,B,C) are located near a pair of dust cores and two Spitzer sources, although they do not appear to be driven by either source. Sta02 associate these two groups of knots with flow SMZ 37. However, the features are not well aligned, and the northward PMs of 3-17A, B and C suggest an association with SMZ 38.

B.3.2 SMZ 38

This is a long, curving flow comprising H2 objects 4-1, 4-2 (A,B), 4-3 and possibly parts of 4-5 and (to the north) 3-17. The flow is associated with a cold dust core and the Spitzer protostar IRS 38. The PMs of the many H2 knots along this flow are consistent with this interpretation; the bright knots in the northern lobe in particular (4-1, 4-2 and possibly also 3-17) are clearly moving northward. The situation in the southern counter-lobe, where SMZ 38 crosses the orthogonal flow SMZ 39 near features 4-5, 4-6 and 4-7, is less clear.

B.3.3 SMZ 39

This flow crosses SMZ 38 in the vicinity of knots 4-5, 4-6 and 4-7. The flow is driven by IRS 39 (not shown in Fig. B.3) and its associated dust core, and includes knots that comprise 4-4 $\sim $3$^\prime $ to the northeast. The PMs of 4-4 sub-features A, B and D clearly support this interpretation. Object 4-6 is also probably part of this flow, as is 4-5A, 4-5B and 4-5D. The arcuate knot 4-5C is probably part of SMZ 38, described in the previous section. The association of knot 4-7 is unclear.

B.4 L 1641-N

The PMs of a few unrelated H2 knots, and some of the features in the huge SMZ 49 flow, are displayed in Fig. B.4. These are discussed in this section.

B.4.1 SMZ 40

The PMs of the components that comprise the bright though compact H2 object 4-9 are unclear, so the association of this object with the nearby Spitzer young star IRS 40 (labelled in Fig. 5) is again tentative.

B.4.2 SMZ 41

The morphology of 4-10 certainly suggests motion to the south, away from the dusty core and Spitzer protostar IRS 41 (labelled in Fig. 5). However, the PMs of the components that comprise this H2 feature are inconclusive.

B.4.3 SMZ 49

The southern lobe of the giant SMZ 49 outflow comprises a number of large, sweeping bow shocks. The shapes of these features cast little doubt on their direction of motion away from L 1641-N. However, some of the brightest H2 features in SMZ 49 have more complex morphologies that suggest a possible association with other outflows. We have therefore measured the PMs of two groups of features, 5-23G (situated $\sim $14$^\prime $ south of L 1641-N) and 6-4A and B (found a further 6$^\prime $-8$^\prime $ downwind/to the south) - see Fig. B.4. Feature 5-23G in particular has a shape that hints at excitation from a source to the southeast (perhaps V380 Ori-NE). Even so, we find that, overall, the H2 knots in both regions are moving southward, and thus confirm the association of 5-23G, 6-4A and 6-4B with the rest of the SMZ 49 outflow.

B.4.4 DFS 124

6-16 is a bright, bow shaped H2 feature $\sim $48$^\prime $ south of HH 1/2. However, there is a Spitzer protostar that is much closer and is arguably the more likely driving source. The PMs of the two main knots in 6-16 support this association (though of course HH 1/2 and its source are also to the north): 6-16 is not only moving away from IRS 124, but appears to be spreading outwards.

B.5 L 1641-C/Re 50

The molecular outflows SMZ 74-SMZ 76 and DFS 131 are displayed in Fig. B.5, with PM vectors marked.

B.5.1 SMZ 74

Objects 9-1 and 9-2 could form part of one long flow, although these compact features are very faint and their PMs are generally rather uncertain. 9-1C, at the northeastern end of this object, has the best-defined PM: it appears to be moving towards the north-northeast. No source candidate was identified nearby in the Spitzer data.

B.5.2 SMZ 75

The PMs of the bow-shaped H2 features 9-3A and 9-3B (and fainter sub-components A1, A2, A3 and B1, B2, B3) are all directed toward the northeast, consistent with these two groups of features being part of the same flow, driven by one of the Spitzer protostars found 5$^\prime $-6$^\prime $ to the southwest.

B.5.3 SMZ 76

SMZ 76 comprises two large, complex arcs, denoted 9-4 and 9-6 by Sta02. Although the sub-components exhibit considerable scatter in their PMs, and measurements for individual H2 knots are influenced in some cases by neighbouring features, overall, 9-4 and 9-6 both appear to be moving towards the east or north-east, consistent with them being part of the same flow that is driven by one of the many Spitzer sources to the south-west. IRS 76 and its associated dense core is the best candidate.

B.5.4 DFS 131

The three compact H2 knots that comprise feature 9-7 are probably not part of the large SMZ 76 outflow. Instead, their well-defined PMs to the east/north-east suggest a driving source to the west: IRS 131, which is also coincident with a dust core, is the best candidate (see Fig. 12).

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