The Astronomical Journal, 127:420–443, 2004 January
# 2004. The American Astronomical Society. All rights reserved. Printed in U.S.A.
HERBIG-HARO FLOWS IN OPHIUCHUS
Randy L. Phelps1,2
Department of Physics and Astronomy, California State University, Sacramento, 6000 J Street, Sacramento, CA 95819-6041; and Department of Physics,
University of California, Davis, 1 Shields Avenue, Davis, CA 95616; [email protected]
and
Mary Barsony1,3
Department of Physics and Astronomy, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132-4163; and Space Science Institute,
Suite A353, 3100 Marine Street, Boulder, CO 80303-1058; [email protected]
Received 2003 July 14; accepted 2003 September 30
ABSTRACT
We report the results of a new [S ii] and nearby off-line, narrowband continuum imaging survey of an
approximately 0.5 deg2 area of the Ophiuchi cloud core. Higher sensitivity and an improved pixel scale (0B37)
over previous surveys has increased the inventory of Herbig-Haro (HH) flows in the cloud core. We report 11
independently discovered HH objects or newly discovered components of known HH objects. Three previous
candidate HH objects have been confirmed, seven new highly probable, and an additional five possible
HH object candidates have been identified. The approximate number of independently driven outflows in the
Ophiuchi cloud core approaches 50 when the number of HH flows detected in the present study is combined
with the number of known CO outflows. The number of outflows exceeds the number of known Class I/Class 0
objects in the same area by at least a factor of 2, leading to the conclusion that Class II and Class III objects must
also be outflow drivers. There is direct evidence in these data for Class II and Class III HH flow drivers, although
the lack of detected emission down to the sources themselves precludes definitive identification of the great
majority of the driving sources.
Key words: ISM: Herbig-Haro objects — stars: formation — stars: winds, outflows
1. INTRODUCTION
1.2. Herbig-Haro Objects in the Ophiuchi Molecular Cloud
1.1. The Ophiuchi Molecular Cloud
Although the Ophiuchi molecular cloud core harbors the
nearest example of a currently forming stellar association, a
complete census of its bona fide members and their associated
outflows has been elusive.
Great progress in the identification of association members
has been made over the past decade or so by combining largescale near-infrared (NIR) and mid-infrared (MIR) surveys,
bringing the known number of Ophiuchi cloud members to
200 (Wilking, Lada, & Young 1989; Barsony et al. 1997,
henceforth also BKLT; Bontemps et al. 2001).
Characterizing and enumerating the outflows present in the
Ophiuchi cloud has proven even more challenging: the high
source density, combined with the relatively poor angular
resolution of large-scale millimetric molecular line maps has
hampered progress in this area. To date, of the 11 molecular
outflows with unambiguously identified exciting sources in
the Rho Ophiuchi clouds, 10 reside in the central L1688 dark
cloud (Bontemps et al. 1996; Kamazaki et al. 2003). Of these,
only the two Class 0 sources, VLA 1623 and IRAS
162932422, have had their molecular outflows imaged in
their entirety (Dent, Matthews, & Walther 1995; Walker et al.
1986).
An alternative method for tracing outflow activity from
embedded young stellar objects (YSOs) is via imaging of
shock-excited emission lines. Outflowing material from
embedded YSOs may interact with the surrounding medium
and result in the development of shocks. The subsequent
cooling of the gas occurs via line radiation, for example, at H
or [S ii] in the optical. Extended regions radiating in these
lines, but lacking continuum emission, are known as HerbigHaro (HH) objects.
The molecular bipolar outflows discovered in the late 1970s
via mapping of the CO (J = 1 ! 0) line and the highly
collimated optical HH flows discovered in the early 1980s via
their faint [S ii] emission were originally thought to be distinct
phenomena, due to the apparent disagreement of more than an
order of magnitude in their momentum fluxes. This ‘‘momentum problem’’ was resolved in the early 1990s, when the
possibility of intermittent ejection events was finally taken
seriously. Additionally, the advent of large-format CCD arrays
allowed for the detection, at large distances from their exciting
sources, of HH objects associated with the molecular outflows
of highly embedded YSOs (Graham & Heyer 1990; Gómez,
Whitney, & Kenyon 1997; Bally et al. 1997). It is now
generally accepted that the two types of outflow phenomena
are intimately related.
Several [S ii] surveys for HH flows have been undertaken in
the core of the Ophiuchi molecular cloud. Wilking et al.
(1997), using the 0.9 m Curtis Schmidt telescope at Cerro
Tololo Inter-American Observatory and 45 minute [S ii]
exposures, identified three new HH objects (HH 312, HH 313,
and HH 314). They confirmed the presence of two HH
objects that had previously been identified (HH 79, Reipurth &
1
Guest observer, Palomar Observatory, which is operated by the California
Institute of Technology.
2
On assignment to the National Science Foundation, 4201 Wilson
Boulevard, Arlington, VA 22230.
3
Participant, 2003 NASA Summer Faculty Fellowship Program at Ames
Research Center.
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HERBIG-HARO FLOWS IN OPH
Graham 1988; HH 224, first reported by Wilking, Schwartz,
& Blackwell 1987 and confirmed by Reipurth 1994).4 The
Wilking et al. (1997) data revealed that HH 224 had two
components (HH 224N and HH 224S). Five candidate HH
objects (C1, C3, C4N/S, C5, and C6 using the Wilking et al.
designations) were also identified.
Gómez, Whitney, & Wood (1998) undertook a similar [S ii]
survey of the core of the Ophiuchi molecular cloud, using
the 1.2 m F. L. Whipple Observatory and 20 minute [S ii]
exposures. The Gómez et al. (1998) survey was not only of
higher sensitivity than the Wilking et al. (1997) survey, but the
data were also obtained using higher spatial resolution (0B63 vs.
2B0 pixel1). From their survey, Gómez et al. (1998) were
able to recover the previously known HH objects and
confirmed four of the five Wilking et al. (1997) candidates
(C1 = HH 419, C3 = HH 224 NW2, C4N/S = HH 416N/S,
and C5 = HH 420). Candidate C6 (=HH 420b) from the
Wilking et al. (1997) list was marginally detected, but could
not be confirmed using the Gómez et al. (1998) data.
In addition, Gómez et al. (1998) identified two new objects
(HH 417 and HH 418) and additional components (HH 79b
and HH 224 NW1) of known sources. Several other candidate
HH objects (A1, A2, A3, and A4a/b) using the designations in
Gómez et al. (1998) were also identified.
Additionally, Wu et al. (2002), using the 60/90 cm Xinglong
Schmidt telescope, undertook an 11 deg2 [S ii] survey and
confirmed the previously known HH objects in the Ophiuchi
cloud core. These authors also identified seven new groups of
HH objects in the off-core region: HH 548, HH 549A–C,
HH 550, HH 551, HH 552, HH 553A–E, and HH 554, all of
which are concentrated in just three regions located 2–3 pc
from the Ophiuchi cloud core.
Most recently, Gómez et al. (2003, hereafter GSWC03)
present results from a NIR 2.12 m molecular hydrogen and
[S ii] survey of a portion of the Ophiuchi region. The [S ii]
component of the survey used the WIYN 3.5 m telescope with
the MIMO Mini-Mosaic Imager to cover six areas, each
100 100 on a side. Using these data, Gómez et al. (2003)
confirm the reality of candidate A2 (now HH 674) from the
Gómez et al. (1998) study and identify four new objects
(HH 673, HH 675, HH 676, and HH 677). The H2 component
of the study used the ESO 3.6 m New Technology Telescope
with the SOFI NIR spectrograph/imaging camera to cover
three regions, each approximately 200 200 on a side. The H2
survey resulted in the detection of 13 NIR knots, some of
which appear to be connected to the optically revealed flows.
The Gómez et al. (2003) survey, while providing deep optical
imaging and a NIR survey for flows for the first time, is
limited in its spatial coverage to only a portion of the cloud
core.
Since surveys for HH objects at increasing sensitivities and
improved pixel scales routinely reveal entirely new sources,
new components of known flows, or greater detail in known
HH objects, we present a new, improved [S ii] and nearby
narrowband continuum survey for HH flows in the
Ophiuchi cloud core. The purpose of this study is to contribute to the eventual identification of all of the outflows and
their exciting sources present in this nearby star-forming
cloud core.
4
Electronically published via anon.ftp to ftp.hq.eso.org, directory /pub/
Catalogs/Herbig-Haro.
421
2. OBSERVATIONS AND DATA REDUCTIONS
Imaging data were acquired with the 1.5 m telescope at
Palomar Observatory, equipped with a 2048 2048 CCD
(CCD No. 13). A narrowband [S ii] filter (wavelength centered
at 6730 Å, with 36 Å FWHM) and a nearby, narrowband
continuum filter (wavelength centered at 6650 Å, with 100 Å
FWHM) were used for the observations. The resulting field of
view was 12A5, with a scale of 0B367 pixel1. The observations (Table 1) spanned a number of nights over a 3 month
period.
For each field, three 20 minute exposures in the [S ii]
filter were co-added, and three 10 minute exposures in the
narrowband continuum filter were co-added, resulting in total
integration times of 60 minutes in [S ii] and 30 minutes in the
continuum. By breaking the total integration times into three
separate exposures, it is possible to median-filter the set of
images to remove signals that result from randomly appearing
cosmic-ray events.
Preliminary data processing was undertaken using techniques described in the IRAF5 CCDPROC documentation.
Zero-level corrections were determined by taking the median
of five zero-second exposure frames. Flat-field images were
constructed by averaging five individual dome images,
obtained in each filter, using the sigma-clipping algorithm in
IRAF. The [S ii] and continuum frames for each field were
separately co-added using the sigma-clipping routine in IRAF
to construct final images used for the identification of HH
objects in Ophiuchi.
3. RESULTS
Our CCD survey for HH objects in the Ophiuchi molecular
cloud consists of 16 individual overlapping fields, each with
observations in [S ii] and the nearby, narrowband continuum.
Figure 1 shows our survey fields superposed on the AngloAustralian Observatory image of the entire Ophiuchi region,
kindly provided by D. Malin. Figure 2 shows our survey region
relative to that surveyed by Gómez et al. (1998). Figure 3
shows a mosaic of the survey regions, composed of the 16
individual fields that were observed.
Since regions containing shock-excited gas emit emission
lines, HH objects are identified by comparing [S ii] images, in
which HH features will be seen if they are present, with off-line
continuum images in which they will not be visible. Figures 4–
19 show each of the 12A5 12A5 fields as they appear through
either (1) the [S ii] filter or (2) the nearby continuum filter. In
each figure, HH objects and a variety of other sources are
labeled. As dust extinction in the optical is severe, it is difficult
in nearly every case to associate a given HH object with its
driving source based on the current data alone. Therefore, for
the purposes of this paper, we will make an effort to identify HH
object driving sources only in those cases where a possible
association has previously been attempted, or when the new
data presented here are suggestive of an association. For
purposes of the identification of outflow driving sources, the
data presented here will be most useful when combined with
NIR studies, which can penetrate the dusty regions closer to the
driving sources.
5
IRAF is distributed by the National Optical Astronomy Observatory,
which is operated by the Association of Universities for Research in
Astronomy, Inc., under cooperative agreement with the National Science
Foundation.
422
PHELPS & BARSONY
TABLE 1
Observation Log
Field
Field
Field
Field
Field
Field
Field
Field
Field
Field
Field
Field
Field
Field
Field
Field
Field
1 ..........
2 ..........
3 ..........
4 ..........
5 ..........
6 ..........
7 ..........
8 ..........
9 ..........
10 ........
11 ........
12 ........
13 ........
14 ........
15 ........
16 ........
(J2000.0)
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
25
25
26
26
26
26
27
27
27
27
27
27
28
28
28
28
56.7
56.5
23.6
40.0
46.4
47.7
06.1
08.3
20.7
29.7
46.7
56.0
12.3
16.4
34.9
43.8
(J2000.0)
24 11 54.0
24 21 09.0
24 32 58.0
24 41 32.0
24 11 19.8
24 20 54.0
24 37 22.0
24 28 54.2
24 48 19.5
24 17 46.0
24 37 26.9
24 28 27.6
24 48 57.5
24 17 30.2
24 39 12.8
24 28 30.1
Date
Seeing
(arcsec)
Filter
1997 May 7
1997 May 6
1997 May 5
1997 May 4
1997 May 7
1997 May 6
1997 Jul 6
1997 Jul 7
1997 May 4
1997 Jul 8
1997 Jul 6
1997 Jul 8
1997 Jul 5
1997 Jul 9
1997 May 8
1997 Jul 10
1.3
1.3
1.6
1.5
1.3
1.3
2.0
1.2
1.5
2.0
2.0
2.0
1.3
1.8
1.4
2.0
Continuum
Continuum
Continuum
Continuum
Continuum
Continuum
Continuum
Continuum
Continuum
Continuum
Continuum
Continuum
Continuum
Continuum
Continuum
Continuum
Filter
[S
[S
[S
[S
[S
[S
[S
[S
[S
[S
[S
[S
[S
[S
[S
[S
ii]
ii]
ii]
ii]
ii]
ii]
ii]
ii]
ii]
ii]
ii]
ii]
ii]
ii]
ii]
ii]
Date
1997
1997
1997
1997
1997
1997
1997
1997
1997
1997
1997
1997
1997
1997
1997
1997
Seeing
(arcsec)
May 7
May 6
May 5
May 4
May 7
May 6
Jul 6
Jul 7
May 4
Jul 8
Jul 6
Jul 7
Jul 5
Jul 9
May 8
Jul 10
1.3
1.3
1.6
1.5
1.3
1.3
2.0
1.2
1.5
2.0
2.0
1.2
1.3
1.8
1.4
2.0
Note.—Units of right ascension are hours, minutes, and seconds, and units of declination are degrees, arcminutes, and arcseconds.
In the following, we compare and contrast our findings with
those of previously published surveys. For clarity, we have
divided the discussion into various sections. The first (x 3.1)
describes those HH objects that are known as a result of
previously published surveys. Section 3.1 also includes newly
detected components and previously suspected, and now
confirmed, components of known HH objects. In x 3.2, we
discuss new features, as well as previously suspected and now
confirmed sources that appear to be unrelated to previously
known HH objects.
At least two independent detections are required for an HH
object to be considered real, with multiple detections being
possible based on comparison of previous studies with the
current survey, or as a result of multiple detections that result
from having overlapping fields available in the current survey
alone. In many cases, single detections in the current survey
data resulted in the categorization of sources as candidate HH
objects, whether the emission was prominent or was only
marginally detected. These sources are discussed in x 3.3.
Finally, for completeness, candidate sources that are of
questionable reality, but deserve mention for various reasons,
are also discussed in x 3.3.
as a bow shock pointing almost due east, with its location almost due north of SR 21(=Elias 30), we can confidently assert
that HH 711, at least, is not driven by SR 21. Candidate
HH object O3, if confirmed to be a real feature, may be driven
by Elias 26 since the [S ii] feature is spatially coincident with
the H2 bow shock structure, GSWC03 24a, which itself points
away from Elias 26.
3.1. Previously Detected and Newly Discovered or Confirmed
Components of Known HH Objects
Table 2 summarizes the list of HH objects previously
known in the Ophiuchi molecular cloud. Discussion of these
HH objects, based on our data, follows.
HH 79/79b.—Figure 9 (field 6) shows the field containing
HH 79 and HH 79b, both of which are recovered in our
[S ii] data. Figure 20 shows close-ups of two portions of the
region. HH 79 itself corresponds to two separate H2 knots
(GSWC03 knots a1 and a2), whereas HH 79b corresponds
to a single H2 knot (GSWC03 knot b). The available data
cannot allow for a physical association of HH 79/79b to
be established. Two new objects, HH 711 and a candidate
HH object (O3) that is discussed in x 3.3, are also found in
the field. HH 711 is spatially coincident with the H2 bow
shock GSWC03 25a and 25b. Based on the morphology of
the NIR H2 emission associated with HH 711, which appears
Fig. 1.—Location of [S ii] survey region (boxes) relative to the Oph
region. The Anglo-Australian Observatory image is used with permission
from D. Malin.
Fig. 2.—Location of [S ii] survey region (boxes) relative to the Gómez et al. (1998) survey region (gray scale)
Fig. 3.—A [S ii] mosaic image of the current survey region
HERBIG-HARO FLOWS IN OPH
425
Fig. 4.—(a) [S ii] image of field 1. (b) Off-line image of field 1.
This is a very rich field of young sources. Among those that
are optically visible in Figure 9 are VSSG 24 (=BKLT
J162713241818), the binary SR21 (=Elias 30 = VSSG
23 = BKLT J162710241914 for the primary and BKLT
J162710241921 for the 6B5 separation companion), Elias 26
(=GSS 37 = VSSG 2 = BKLT J16264224203, a 1B44 separation binary YSO; Barsony, Koresko, & Matthews 2003a), S1
(=Elias 25 = GY 70 = BKLT J162634242330, one of the few
B stars in the Ophiuchi cluster, projected in front of the dust
lane—S1 is itself a 0B02 binary discovered by Simon et al.
1995), Elias 24 (=BKLT J162624241616), DoAr 24E
(=Elias 22 = GSS 31 = WSB 30 = BKLT J162623242101,
a well-known infrared companion binary system discovered by
Chelli et al. 1988), and Elias 23 (=GSS 32 = GY 23, which
forms a wide, 10B47 separation binary with GY 21; Haisch
et al. 2002).
Additionally, there are of order two dozen known or
suspected YSOs in this field that appear at NIR and longer
wavelengths. A detailed discussion of each is beyond the
scope of this paper, however, mention is made of a few that
may be good candidates for exciting the observed [S ii] features, and those that can be ruled out as exciting sources or
Fig. 5.—(a) [S ii] image of field 2. (b) Off-line image of field 2.
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PHELPS & BARSONY
Vol. 127
Fig. 6.—(a) [S ii] image of field 3. (b) Off-line image of field 3.
that have been mentioned by previous authors as possible
candidate exciting sources. In all cases, a possible association
is based mostly on geometrical considerations.
In Figure 9 (field 6), VSSG 3 (=LFAM18 = ROXs17 = GY
135 = BKLT J162649242005) is a K6 spectral type, Class III
YSO, seen through a visual extinction of AV = 16 (Luhman &
Rieke 1999). It is somewhat unusual in being a centimeter
continuum source (Leous et al. 1991). Furthermore, VSSG 3 is
less than 1 million years old, based on its location on pre–
main-sequence evolutionary tracks (Wilking et al. 2001). The
H2 knot (GSWC03 a1) that is associated with HH 79 points
away from VSSG 3 to the southwest, while the H2 knots
GSWC03 25a/b that are associated with HH 711 lie on the
opposite side of VSSG 3 and point away from VSSG 3 toward
the northeast. Since VSSG 3 lies on a line between these
sources, we suggest that VSSG 3 is the exciting source for
HH 711 and perhaps part of HH 79.
VSSG 27 (=LFAM9 = GY 51 = BKLT J162630242258)
is a 1B2 separation binary located at the apex of the large
diffuse nebulosity and dust structure that lies behind S1 (see
Fig. 7.—(a) [S ii] image of field 4. (b) Off-line image of field 4.
No. 1, 2004
HERBIG-HARO FLOWS IN OPH
427
Fig. 8.—(a) [S ii] image of field 5. (b) Off-line image of field 5.
Figs. 9 and 20). The brighter 2.2 m component is a Class II
object with a K3–M1 spectral type seen through a visual
extinction of AV = 22 (Luhman & Rieke 1999; Greene &
Meyer 1995). This object is also a centimeter continuum
emitter (Leous et al. 1991). It may be a candidate for the
emission observed in HH 79.
Two sources, SR 21 (=Elias 30 = VSSG 23) and VSSG 28
(=GSS 39 = Elias 27 = BKLT J162645242309), have previously been proposed as candidates for the exciting source of
HH 79b (Wilking et al. 1997; Gómez et al. 1998). Although
neither SR 21 (Class II, F4 spectral type) nor VSSG 28
(Class II K8 spectral type) can be ruled out as the exciting
source for HH 79b, the presence of other nearby NIR YSOs
suggests additional evidence is required for correct identification of the exciting source for HH 79b. In particular,
VSSG 7 (=GSS 41 = IRS 22 = BKLT J162655242030) is a
possible exciting source for HH 79b because of its proximity and alignment with the outflow. Other than being tentatively classified as a Class III object, very little is known
about this source (Bontemps et al. 2001). VSSG 11
Fig. 9.—(a) [S ii] image of field 6. (b) Off-line image of field 6.
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Vol. 127
Fig. 10.—(a) [S ii] image of field 7. (b) Off-line image of field 7.
(=IRS 19 = BKLT J162643241635), another nearby YSO,
is a Class III radio emitter of M3 spectral type, seen through
AV = 14, and judged to be have an age less than 1 106 yr
(Wilking et al. 2001), and is another candidate exciting source
for HH 79b.
For completeness, we also plot the location of GY 30 (BKLT
J162625242303) in field 9, since it was found to be the driver
of a recently discovered CO outflow in the region (Kamazaki
et al. 2003). Very little is known about GY 30, since it was too
faint to be included in NIR spectroscopic surveys (e.g.,
Luhman & Rieke 1999) and has not been detected at centimeter
(Leous et al. 1991), MIR (Bontemps et al. 2001), or X-ray
(Imanishi, Koyama, & Tsuboi 2001) wavelengths. Nevertheless, it is associated with a NIR reflection nebulosity, which
shares the CO outflow axis (Kamazaki et al. 2003). However,
the GY 30 outflow is directed along a northwest-southeast axis,
and thus cannot be responsible for any of the [S ii] emission
features seen in this field.
HH 224.—Figure 12 (field 9) shows the region containing
the HH 224 complex. All of the previously known substructure
Fig. 11.—(a) [S ii] image of field 8. (b) Off-line image of field 8.
No. 1, 2004
HERBIG-HARO FLOWS IN OPH
429
Fig. 12.—(a) [S ii] image of field 9. (b) Off-line image of field 9.
(HH 224 North, HH 224 South, HH 224 NW1, HH 224
NW2) has been recovered. Faint, diffuse [S ii] emission
extends from HH 224S to the northwest, as hinted by the
Gómez et al. (1998) data and suggested by them. Our data,
however, reveal northward extended emission (HH 714) in
the field just to the north in Figure 10 (field 7) and to the
west in Figure 7 (field 4) of Figure 12. This feature, HH 714,
extends through GY 194 and may be a component of HH
224 or a separate outflow, forming a ‘‘fork’’ in the emission
near GY 193. For this reason, it has been given a separate
HH designation. Figure 21 shows a close-up of the area,
constructed by combining portions of the above mentioned
three fields.
Wilking et al. (1997) and Gómez et al. (1998) discuss the
possible driving source for HH 224, indicating SR 24 as a
candidate, based on its YSO characteristics, even though it is
clearly not aligned with the flow. SR 24, therefore, can be
ruled out as the driving source for the outflow. The spatial
alignment of GY 193 with most of the HH 224 emission
suggests it remains a candidate for the driving source, as
discussed by both Wilking et al. (1997) and Gómez et al.
(1998). However, the newly detected forked emission
Fig. 13.—(a) [S ii] image of field 10. (b) Off-line image of field 10.
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Fig. 14.—(a) [S ii] image of field 11. (b) Off-line image of field 11.
(HH 714) extending beyond GY 193 toward the north and
the additional emission continuing beyond GY 193 toward the
northwest complicates this interpretation. In fact, the type of
major bow shock formed by HH 224 and its associated shock
features strongly point to a very young embedded source
farther to the northwest, as pointed out by B. Reipurth
(2003, private communication). It has also been suggested
that the Class I protostar, IRS 43 (=YLW 15), might be
responsible for the emission from HH 224 NW1 (Grosso et al.
2001). For this reason, we have plotted the location of IRS 43
in both Figure 10 (field 7) and Figure 21, which clearly shows
that IRS 43 is not the driving source for any component of HH
224. For reference, we have also plotted the positions of a few
nearby near-infrared YSOs: GY 224 (a Class I/flat-spectrum
protostar), IRS 42 (a flat-spectrum protostar) and GY 253 (a
Class III source).
Although the exciting source of the extended HH 224
flow remains to be identified, the extent of the HH 224
emission can now be traced to roughly 0 . 15, which at a
distance of 125 pc (de Geus, de Zeeuw, & Lub 1989; de
Fig. 15.—(a) [S ii] image of field 12. (b) Off-line image of field 12.
No. 1, 2004
HERBIG-HARO FLOWS IN OPH
431
Fig. 16.—(a) [S ii] image of field 13. (b) Off-line image of field 13.
Geus 1992) for Ophiuchi, corresponds to a linear extent
of 1/3 pc.
HH 312.—Figure 5 (field 2) and Figure 22 show the
region containing the jetlike chain of knotty emission associated with HH 312. Our data reveal at least five knots of
emission, in somewhat better detail than previous studies.
As discussed by both Wilking et al. (1997) and Gómez et al.
(1998), the spatial coincidence of the HH 312 flow with SR 4
suggests it is a candidate for the driving source. The terminus of the flow axis, however, is offset significantly to
the north of SR 4 itself. HH 312 is in rough alignment
with an H2 emission knot, GWSC 2003 8a. However, no H2
counterpart to the optical flow is found, suggesting the exciting
source may actually be at some distance from the optically
visible flow.
We suggest that BKLT J162532241754, which is also in
rough alignment with the HH 312 flow, is a possible exciting
source, although this source too is not in direct alignment
with HH 312 (see Fig. 5a). The possibility of a precessing
flow, and the lack of emission down to SR 4, preclude a
Fig. 17.—(a) [S ii] image of field 14. (b) Off-line image of field 14.
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PHELPS & BARSONY
Fig. 18.—(a) [S ii] image of field 15. (b) Off-line image of field 15.
definitive assignment of the driving source using the current
data.
HH 313.—Figure 5 (field 2) also shows the region containing
HH 313. A close-up view is shown in Figure 23. HH 313 is
associated with the VLA 1623 outflow. Our data confirm the
HH nature of the source and its association with an H2 emission
knot, H5 (Dent et al. 1995) or A (Davis & Eisloffel 1995), as
first pointed out by Wilking et al. (1997). Furthermore, our data
show that HH 313 is somewhat to the northwest of the H2
emission knot, A3 (Davis et al. 1999), as expected from their
analysis of knots A1, A3, and A4 as forming a curved, C-type
bow-shock moving toward the observer, within the CO outflow
powered by the Class 0 protostar, VLA 1623.
HH 314.—Figure 7 (field 4) shows the region containing
HH 314, while Figure 24 shows a close-up view of the source.
From their data, Gómez et al. (1998) describe HH 314 as a
well-defined [S ii] knot, while our data reveal HH 314 to be
composed of two diffuse, extended [S ii] components extending toward the northwest and southeast of a pointlike [S ii]
source. Intriguingly, HH 314 is aligned with the portion of
Fig. 19.—(a) [S ii] image of field 16. (b) Off-line image of field 16.
TABLE 2
Previously Known HH Objects in the Ophiuchi Molecular Cloud
Source
Component
Discovery
Remarks
HH 79 .........
...
b
South
North
NW2
NW1
...
...
...
South
North
...
...
...
...
...
A–C
...
...
...
A–E
...
RG88
GWK98
R94
WSFF97
WSFF97
GWK98
WSFF97
WSFF97
WSFF97
WSFF97
WSFF97
GWK98
GWK98
WSFF97
WSFF97
WWYDC02
WWYDC02
WWYDC02
WWYDC02
WWYDC02
WWYDC02
WWYDC02
RG88 = Reipurth & Graham 1988
GWK98 = Gómez et al. 1998
R94 = Wilking et al. 1987
WSFF97 = Wilking et al. 1997
WSFF97 source C3, conBrmed by GWK98
Emission connects 224 NW1, 224 NW2, 224 North and 224 South
Jetlike series of knots
HH 224 .......
HH
HH
HH
HH
312 .......
313 .......
314 .......
416 .......
HH
HH
HH
HH
HH
HH
HH
HH
HH
HH
HH
417 .......
418 .......
419 .......
420 .......
548 .......
549 .......
550 .......
551 .......
552 .......
553 .......
554 .......
WSFF97 source C4 South, conBrmed by GWK98
WSFF97 source C4 North, conBrmed by GWK98
WSFF97 source C1, conBrmed by GWK98
WSFF97 source C5, conBrmed by GWK98
WWYDC02 = Wu et al. 2002
Fig. 20.—[S ii] images showing the HH 79 region, including close-up views of HH 79/9b, HH 711, and O3
Fig. 21.—[S ii] image of the HH 224 region, revealed from a composite of mosaic images
Fig. 22.—[S ii] image of a portion of the HH 312 region
Fig. 23.—[S ii] image of a portion of the HH 313 region
HERBIG-HARO FLOWS IN OPH
Fig. 24.—[S ii] image of HH 314
HH 224 NW2 that extends through the candidate driving
source GY 193. This suggests at least the possibility that HH
314 and the HH 224 complex are related bipolar flows from
GY 193. Based on proximity arguments, GY 93, a Class II
source (Greene & Lada 1997), is also a candidate for driving
the HH 314 outflow.
HH 416N/S.—Figure 12 (field 9) shows the region
containing the feature, HH 416N/S. Figure 25 shows a closeup view of the sources. HH 416N is also visible in Figure 16
(field 13). Wilking et al. (1997) suggested WSB 58, shown in
Figure 16, is the driving source, although the northeast/
southwest alignment of HH 416N/S and the location of WSB
58 to the east precludes this association. Gómez et al. (1998)
suggest IRS 54 as an alternative. IRS 54, however, is quite
distant from HH 416N/S, as revealed in Figure 15 (field 12).
HH 416N has a morphology resembling a bow shock moving
to the northeast, while HH 416S has a diffuse jetlike flow of
gas, toward the southwest of HH 416N, that terminates at a
point source visible in the continuum image. It is likely that this
point source (BKLT J162743244923) is the driving source
for HH 416N/S.
HH 417.—Figure 19 (field 16) shows the Y-shaped
morphology of HH 417, which is highlighted in the close-up
view shown in Figure 26. Gómez et al. (1998) associate
HH 417 with SR 13, although the axis of HH 417 does not
point directly toward that source. By contrast, the jetlike
component of HH 417 ends directly on the NIR source, BKLT
J162825242800. We suggest this is the exciting source for at
least this component of HH 417. The curved component of
HH 417 may either be excited by the same NIR source or may
be the result of a superposition of HH flows powered by
nearby, but as of yet unidentified driving sources.
HH 418.—Figure 7 (field 4) also shows the presence of
HH 418, which Gómez et al. (1998) describe as a nebular
object. A close-up view is shown in Figure 27. Our data reveal
435
Fig. 26.—[S ii] image of HH 417
HH 418 to be an extended, nebular feature, although its
location near the edge of a single frame in our survey limits
further interpretation of the object. An additional feature
(object O2) may be associated with HH 418, but as discussed
below, its reality awaits confirmation. It is even possible that
O2 and HH 418 are part of the HH 224 flow.
HH 419.—Figure 6 (field 3) shows the region containing HH
419, a diffuse feature first identified by Wilking et al. (1997) and
confirmed by Gómez et al. (1998). Figure 28 shows a close-up
of the feature. Faint extensions of HH 419 appear to the
northwest and are given the designations O1a and O1b, pending
confirmation by future observations. Together HH 419, O1a,
and O1b form an arc, concave toward the southwest, that leads
toward DoAr 21(=GSS 23), a weak-lined T Tauri star (WTTS)
as classified by Bouvier & Appenzeller (1992). Diffuse emission, seen in both the [S ii] and continuum images, also extends
toward the northwest of DoAr 21. Although classified as a
WTTS, DoAr 21 lies above the 1 Myr isochrone (Wilking et al.
2001) and possesses a gas-phase disk (Bary, Weintraub, &
Kastner 2002). We therefore consider DoAr 21 to be a candidate
for the HH 419/O1a/O1b outflow.
HH 420/420b.—Figure 18 (field 15) reveals the presence of
the diffuse feature, HH 420. Gómez et al. (1998) were unable
to confirm the reality of HH 420b (candidate C6 in Wilking
et al. 1997), but our data do establish its reality since the
feature is visible in [S ii], but not in the continuum, in both
Figure 18 (field 15) and Figure 19 (field 16). Additionally, a
feature (O5) that may be associated with HH 420b is found in
field 15. Its absence in the overlapping field 16 leaves its
reality in need of confirmation, although its proximity to the
bright star SAO 184412 may simply have made its detection
difficult. A close-up of the region is shown in Figure 29.
HH 548–HH 554.—These features, detected by Wu et al.
(2002) are outside of our survey region.
3.2. Confirmed and Independently Discovered HH Objects
Table 3 summarizes the list of new HH objects that are
confirmed or independently discovered as a result of our
Fig. 25.—[S ii] image of the double component source, HH 416 N/S
Fig. 27.—[S ii] image of HH 418
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Fig. 28.—[S ii] image of the region containing HH 419, including a close-up of HH 419 and its candidate components O1a and O1b
current survey. At least two detections are required for the
source to be considered real. Multiple detections are possible
using identifications from previous studies combined with the
current survey or by using overlapping fields in only the
current survey.
HH 420b.—The reality of HH 420b is confirmed with the
current data, as discussed above.
HH 673.—Figure 6 (field 3), Figure 7 (field 4), and Figure 10
(field 7) reveal the presence of a two-component feature seen in
[S ii] but not the continuum in three separate overlapping
frames, and hence they are considered to be true HH objects.
One feature was independently discovered by Gómez et al.
(2003) and given the designation HH 673 in that study. We
therefore designate the second component HH 673b. The
position of the infrared YSO, WL 18, is indicated in the closeup view of HH 673/673b presented in Figure 30. WL 18
is a 3B55 separation binary, with the secondary being at
P.A. = 293 relative to the primary (WL 18S) at K (Barsony
et al. 2003a). Only the primary is detected at mid-infrared
wavelengths (Barsony, Ressler, & Marsh 2003b). Given the
symmetry of the locations of HH 673 and HH 673b about
the position of WL 18, it is highly likely that WL 18 is the
driver of this flow, as proposed by Gómez et al. (2003).
Furthermore, based on its infrared properties, it is most likely
that it is the primary, WL 18S, that drives the observed
outflow.
HH 674.—Gómez et al. (1998) describe their candidate A2
as a small nebular [S ii] emission object. The feature has been
confirmed by the Gómez et al. (2003) study, in which it was
given the designation HH 674 and GSWC03 7d based on an
associated H2 detection. Figure 10 (field 7) and Figure 14
(field 11) reveal the presence of this feature in our [S ii] images
but not in the continuum, thus providing an independent
Fig. 29.—[S ii] image of the HH 420/HH 420b region
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HERBIG-HARO FLOWS IN OPH
437
TABLE 3
Confirmed and Independently Discovered HH Objects
Source
HH
HH
HH
HH
HH
HH
HH
HH
HH
HH
HH
HH
HH
420 ................
673 ................
674 ................
675 ................
676 ................
677 ................
708 ................
709 ................
710 ................
714 ................
711.................
712 ................
713 ................
Component
b
...
...
...
...
...
...
...
...
...
...
...
...
Discovery
WSFF97
GSWC03,
GWK98
GSWC03,
GSWC03,
GSWC03,
GWK98
GWK98
PB03
PB03
PB03
PB03
PB03
PB03
PB03
PB03
PB03
Comments
WSFF97 source C6, conBrmed by PB03; PB03 = Phelps & Barsony (2003), this paper
Detected in three overlapping frames
GWK98 candidate A2, conBrmed by GSWC03, PB03
Detected in two overlapping frames
Detected in two overlapping frames
Single detection in PB03, but detected by GSWC03
GWK98 candidate A1, conBrmed by PB03
GWK98 candidate A4a, conBrmed by PB03
Detected in two overlapping frames
Possible forked branch of HH 224NW2 extending to the northwest
Detected in two overlapping frames
Detected in two overlapping frames
Detected in two overlapping frames
confirmation of its reality. Figure 31 shows a close-up of the
HH 674 region. As discussed by Gómez et al. (1998), there are
13 YSO sources within 50 of HH 674 (A2 in that study).
Gómez et al. (2003) list IRS 44 (=GY 269), a Class I source
located 7600 away, as the likely driving source for HH 674.
However, given the proximity to HH 674 of several NIR
YSOs in the region, no definitive identification of the driving
source for this feature is possible with the existing data.
HH 675.—Figure 12 (field 9) and Figure 14 (field 11) reveal
a feature, independently detected by Gómez et al. (2003), and
given the designation HH 675 in that study. HH 675 is in the
general vicinity of HH 674 (Fig. 31). The infrared YSOs
IRS 51, IRS 53, and GY 301, have been proposed as possible
driving sources for HH 675 (Gómez et al. 2003). We propose
that other nearby YSOs in the region also be considered as
possible exciting sources for HH 675.
HH 676.—Figure 13 (field 10) and Figure 15 (field 12)
reveal a feature, also found independently by Gómez et al.
(2003) and given the designation HH 676 in that study. A
close-up view of HH 676 is shown in Figure 32. Exciting
sources for HH 676 could be any of Elias 34, Elias 35, Elias 36,
or even SR 10. Note that both Elias 34 and Elias 36 are
subarcsecond binaries (see Barsony et al. 2003a and references
therein).
HH 677.—There is a convincing detection of two features in
the [S ii] portion of Figure 15 (field 12), but not in the continuum
images. One of these features was independently detected by
Gómez et al. (2003) and given the designation HH 677. They
list the Class II source SR 10, located 2900 away, as a possible
driving source. A close-up view of HH 677 is shown in
Figure 33. The lack of overlapping frames, allowing for
multiple detections, led us to classify the second feature,
designated O4, as a candidate HH object (see x 3.3). However,
Fig. 30.—[S ii] image of the HH 673 region
the proximity to HH 677 strongly suggests its reality, with SR 10
being a candidate driving source for both HH 677 and O4.
HH 708.—Gómez et al. (1998) report a faint, filamentary,
candidate HH object (their object A1) near the sources,
ROXs 20A (=WSB 45B KLT J162714245132) and
ROXs 20B (=WSB 46B KLT J162715245137), which they
identify as possible driving source. Figure 12 (field 9) and
Figure 34 show our data for this source. Its presence in the [S ii]
image but not in the continuum, coupled with the detection by
Gómez et al. (1998), confirms its HH nature. Our data do not
allow for a more definitive identification of the driving source.
HH 709.—Gómez et al. (1998) also list two candidate HH
objects, A4a and A4b. Figure 16 (field 13) shows our survey
images for the region containing these candidates, while
Figure 35 shows a close-up of the region. Candidate A4a is
apparent in the [S ii] images, but not in the continuum, which
when coupled with the detection by Gómez et al. (1998),
confirms its reality as an HH object (now designated HH 709).
Gómez et al. (1998) candidate A4b, however, is resolved into
stars in both our [S ii] and continuum images, and hence it is
ruled out as an HH object.
HH 710.—Figure 5 (field 2) and Figure 4 (field 1) reveal a
newly detected feature, HH 710, interior to the prominent dust
ring seen in both figures. A close-up view is shown in Figure 36.
Fig. 31.—[S ii] image of the HH 674/ HH 675 region
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Fig. 34.—[S ii] image of HH 708
Fig. 32.—[S ii] image of the HH 676 and HH 712 region
That HH 710 is seen in [S ii] but not the continuum, and that the
feature is found in two overlapping CCD frames, confirms its
nature as an HH object. No definitive association with a driving
source can be made using the current data.
HH 711.—Figure 9 (field 6) and Figure 13 (field 10) reveal
a new HH object (HH 711). A close-up view of the feature is
presented in Figure 37. That the feature is found in two
overlapping fields (fields 6 and 10), and seen in [S ii] but not
the continuum, confirms its reality. Further discussion of
HH 711 is presented along with HH 79/79b in x 3.1.
HH 712.—Figure 13 (field 10) and Figure 17 (field 14)
reveal a newly detected feature, HH 712. It is found in the same
general region as HH 676 (Fig. 32). Its presence in two
separate frames, along with its detection in the [S ii] images but
not in the continuum, indicate it is a real feature. Candidate
driving sources for HH 712 include SR 21 and Elias 34.
HH 713.—Figure 14 (field 11) and Figure 15 (field 12)
reveal a newly detected feature, HH 713, in the [S ii] images
but not in the continuum, confirming its reality. A close-up is
shown in Figure 38. The driving source remains unidentified,
although several infrared sources (BKLT J162812243207,
BKLT J162813243128, BKLT J162813243139 and BKLT
J162813243249) are located nearby.
HH 714.—HH 714 may be a forked extension of the HH
224 complex, or a separate flow, and is discussed with HH 224
in x 3.1.
3.3. Candidate HH Objects
Objects that are considered to be likely candidates are given
the designation ‘‘O.’’ In all cases, these features show up
prominently in the [S ii] images but not in the continuum
images. In most cases, however, there is only a single detection due to lack of overlapping frames in our survey mosaic.
Fig. 33.—[S ii] image of the region containing HH 677 and candidate HH
object O4.
Pending confirmation, these features, listed in Table 4, are
listed only as candidate HH objects.
O1a/b.—As discussed in x 3.1, apparent extensions of
HH 419 in Figure 6 (field 3) appear to the northwest of that
feature in [S ii] but not in the continuum in the only survey
frame that covers that region. A composite view of the HH
419/O1 region is shown in Figure 28. Pending confirmation,
these features are given the designations O1a and O1b,
although their connection to HH 419 suggests a high likelihood they are real features. We propose DoAr 21 as the
candidate driving source for the HH 419/O1 complex, as discussed in x 3.1.
O2.—A single field, shown in Figure 7 (field 4), reveals the
presence of a probable [S ii] feature, which is not seen in the
continuum image. A close-up view is shown in Figure 27.
Given the detection in only a single frame, because of the lack
of overlap of that field in the survey, confirmation of the
reality of O2 is required. However, its location near a known
object (HH 418) is suggestive of its HH nature. Little can be
said about the driving source based on our current data.
O3.—This feature, shown in Figure 9 (field 6) and in a
close-up view in Figure 20, appears only in this field, which
had no overlap with other fields in our survey. Its appearance
in the [S ii] image but not in the continuum image, coupled
with its location in a region containing several other HH
objects (HH 79/79b and HH 711), suggests it is a likely HH
object. Additionally, as discussed in x 3.1 with HH 79/79b, O3
is positionally coincident with a H2 bow-shock feature imaged
by Gómez et al. (2003), whose axis of symmetry and morphology point back to Elias 26 as the exciting source.
O4.—There is a convincing detection of a feature in the
[S ii] portion of Figure 15 (field 12) but not in the continuum
images. This feature, which is also present in the [S ii] image
of Gómez et al. (2003), appears to be associated with HH 677.
SR10, a Class II object according to Bontemps et al. (2001), is
a likely exciting source for both HH 677 and O4 (See x 3.2 on
HH 677). The lack of overlapping frames in our survey,
allowing for multiple detections, coupled with its omission in
the list of detected features in Gómez et al. (2003) leads us to
classify O4 as a candidate HH object pending confirmation.
Fig. 35.—[S ii] image of the HH 709 region
No. 1, 2004
HERBIG-HARO FLOWS IN OPH
439
Fig. 36.—[S ii] image of HH 710
O5.—As discussed in x 3.1, a feature near HH 420b is
found in Figure 18 (field 15) and Figure 29. The absence of
O5 in Figure 19, which shows the overlapping field (field 16)
in which it would be expected to be seen, means that the
reality of the feature cannot be confirmed. Its proximity to the
bright star SAO 184412, however, may simply make detection
of O5 in Figure 19 difficult, and hence confirmation for the
reality of O5 is needed.
Objects that are considered to be marginal candidates are
given the designation ‘‘P.’’ In many cases, the nature of their
detections is similar to the candidate HH objects discussed
above, but the detection was considered to be less convincing.
In other cases, a second detection failed to materialize as
expected, resulting in questionable reliability of the initial
detection.
P1.—A marginal [S ii] feature is detected in Figure 10
(field 7) but not in the continuum image. A close-up is shown
in Figure 39. The marginal nature of the single detection,
because of the lack of overlapping images of the region, leads
to the designation of P1 as a candidate HH object in need of
confirmation.
P2.—Similarly, a marginal feature is detected in [S ii] but
not the continuum, as revealed in Figure 11 (field 8). A closeup is shown in Figure 40. No overlapping fields are available
to confirm its detection, hence it is designated as a candidate
HH object in need of confirmation. If confirmed as an HH
object, however, object P2 may be powered by GY 264.
P3.—A marginal [S ii] feature is also detected in Figure 8
(field 5), but not in the continuum image. A close-up of the
region is shown in Figure 41. No overlapping images of the
region are available, leading to a single detection and hence
the designation of P3 as a candidate HH object in need of
confirmation.
P4 and P5.—Marginal features are found in the [S ii]
images in Figure 14 (field 11) but not in the continuum image.
They are located in the vicinity of HH 674 (Fig. 31). The
marginal nature of the single detections, resulting from
the lack of overlapping images of the region, leads to the
Fig. 38.—[S ii] image of HH 713
designation of P4 and P5 as candidate HH objects, in need of
confirmation.
3.4. Unlikely HH Objects
For completeness, several features that have been proposed
as candidate HH objects, but are unlikely to be real are discussed. For those that were considered initially during our
current survey, the designation ‘‘U’’ is given to indicate the
unlikely reality of the feature. A summary of these features is
given in Table 5.
A3.—Gómez et al. (1998) describe their candidate A3 as a
[S ii] nebular object in need of confirmation. The location of
A3 is shown in our Figure 18 (field 15). No feature is present
in either the [S ii] or continuum filters, and we cannot,
therefore, confirm its reality with the current data.
A4b.—As discussed above, and shown in Figure 16
(field 13), Gómez et al. (1998) candidate A4b is resolved
into stars in both our [S ii] and continuum images and hence is
ruled out as an HH object.
U1 and U2.—As indicated in Figure 11 (field 8), two
features labeled U1 and U2 are identified in the [S ii] image,
but do not appear in the continuum. However, they should
also appear in the [S ii] image shown in Figure 10 (field 7) and
do not. The lack of detection in field 7 results in their
classification as unlikely candidates, but for completeness in
the event of future HH searches in Ophiuchi, they are
presented here.
4. DISCUSSION
The coordinates of the HH objects are listed in Table 6.
Table 7 lists the coordinates of the candidate HH objects, both
those that are likely and those with marginal detections. The
Digitized Sky Survey was used to obtain the coordinates
for reference stars, while a Web-based astrometry routine
(Simoneti 2002)6 was used to determine the transformation
between pixel coordinates and right ascension and declination
for the HH objects themselves. Typical positional coordinates
are 100 –200 . The lack of reference stars in some fields resulted
in uncertain coordinates for several candidate HH objects, and
for these the greater uncertainty (estimates to be up to 500 ) is
indicated by the colon.
4.1. Census of Outflows and their Drivers
The increased resolution and sensitivity of our [S ii] survey
of the Oph cloud core, compared with previous optical
studies, has allowed for the identification and/or confirmation
Fig. 37.—[S ii] image of HH 711
6
Available at http://www.phys.vt.edu/~jhs/SIP/astrometrycalc.html.
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TABLE 4
Candidate HH Objects
Source
Component
Discovery
Comments
O1a, O1b........
O2...................
O3...................
O4...................
O5...................
P1 ...................
P2 ...................
P3 ...................
P4 ...................
P5 ...................
...
...
...
...
...
...
...
...
...
...
PB03
PB03
PB03
PB03
PB03
PB03
PB03
PB03
PB03
PB03
Extended emission northeast of HH 419
Possible extension of HH 418
No overlapping frames, prominent in [S ii]
No overlapping frames, prominent in [S ii]
Likely component of HH 420b
No overlapping frames, marginal [S ii]
No overlapping frames, marginal [S ii]
No overlapping frames, marginal [S ii] near field edge
Marginal [S ii], possibly associated with HH 674
Marginal [S ii], possibly associated with HH 674
of 33 HH objects or components of HH objects (Table 6) and
11 candidate HH objects or components of HH objects
(Table 7). In total, 44 distinct regions of shocked gas have
been traced by [S ii] emission. A number of these features can
be grouped together as likely belonging to a single outflow:
e.g., the five knots of HH 312, at least four components
of HH 224, the three components of the HH 419/O1a/O1b
outflow, and pairs of objects such as HH 416N/S, HH 673/
673b, and HH 79/711. Furthermore, of the 15 known CO
outflows in the cloud core (Bontemps et al. 1996; Sekimoto
et al. 1997; Kamazaki et al. 2003), we detect the optical
manifestations from only one (HH 313 of the VLA 1623
outflow).
It is challenging, and often impossible, to identify the
exciting source for a given HH object from only the data
presented here. This is a consequence of the fact the optically
visible HH objects often appear far from their exciting
sources, where the extinction is low enough to allow them to
be detected. Furthermore, flows are not necessarily straight:
the HH 224 complex shows a bending, as does the HH 419/
O1a/O1b flow and the famous VLA1623 CO flow (Dent et al.
1995)—intriguingly, the curvature for all three of these largescale flows is concave toward the southwest, possibly a result
of shaping by the ambient magnetic field within the cloud as
discussed by Dent et al. (1995). Finally, a single HH object
may have many possible candidate exciting sources. There are
exceptions, however, such as the case of WL 18 (see Fig. 30),
which is symmetrically placed between two HH objects,
HH 673/673b.
A comprehensive enumeration and evaluation of known
YSOs as drivers for each of the HH objects here presented
Fig. 39.—[S ii] image of the marginal candidate HH object P1.
is beyond the scope of this work. Making the realistic, yet
conservative, approach of assuming that each feature/component listed in Tables 6 and 7 with the same primary numerical
designation is part of a single flow results in an estimate of 32
[S ii] outflows. There are, therefore, of order 50 or so known
outflows in the Ophiuchi cloud core, when the present [S ii]
and published CO outflow data are combined. This number is
a lower limit, in the sense that yet more outflows await
discovery through large-scale near-infrared H2 mapping (e.g.,
Gomez et al. 2003).
4.2. Driver Characteristics
The number of outflows in Ophiuchi exceeds the number
of known Class 0 and Class I objects (of order two dozen) by
a factor of 2, if not 3 (Bontemps et al. 2001). Assuming that
all, or nearly all Class 0 and Class I sources have been found,
this leads to the inevitable conclusion that Class II and possibly Class III objects must necessarily be outflow drivers as
well.
In fact, two of the three CO outflow searches toward
Ophiuchi to date have been biased against finding outflows
driven by Class II or Class III objects. The most comprehensive CO outflow search toward Ophiuchus, surveying
14 YSOs, was targeted exclusively toward Class I and Class 0
objects (Bontemps et al. 1996). The Sekimoto et al. (1997) CO
outflow search of five objects was aimed toward hard X-ray
emitters, which are preferentially found among Class I objects,
although one of the four outflow drivers in their survey was
a Class II object. Only the most recent CO outflow search
Fig. 40.—[S ii] image of the marginal candidate HH object P2.
No. 1, 2004
HERBIG-HARO FLOWS IN OPH
Fig. 41.—[S ii] image of the marginal candidate HH object P3.
toward Ophiuchi was unbiased in that the survey region did
not depend on the spectral energy distribution (SED) classification of the possible driving source (Kamazaki et al.
2003). As a result of their unbiased search and high spatial
resolution, three CO outflows with either Class II or Class III
driving sources were found.
In our present [S ii] outflow survey, which is also unbiased
with respect to the SED classification of outflow drivers, we
find that among the most secure candidates for outflow drivers
there are Class II and Class III objects. Examples are WL 18, a
Class II object driving HH 673/673b (see Fig. 30), and
DoAr 21, a Class III object, driving HH 419/O1a/O1b (see
Fig. 28).
4.3. Open Questions and Future Work
The results of this study have brought into sharp focus the
question of when bipolar outflows turn off during YSO evolution. There is now ample evidence of bipolar outflow activity among the earliest protostellar (Class 0) stage (André,
Ward-Thompson, & Barsony 2000), as well as the later ‘‘selfembedded’’ (Class I) stage (e.g., Bontemps et al. 1996 and
Sekimoto et al. 1997). Our current study, as well as future
high-sensitivity, high angular resolution studies (especially
imaging in the near-infrared H2 shock-emission lines) will
allow unbiased searches for outflows driven by pre–mainsequence stars with optically thick (Class II) or optically thin
(Class III) disks for the first time.
Once a significant number of outflow driver identifications
will have been made among the Class II and Class III populations, correlation of stellar parameters (such as rotational
speed, magnetic field strength), disk parameters, and outflow
properties can be advanced via high-resolution, near-infrared
spectroscopy of the driving sources.
5. SUMMARY
Our survey highlights the advantage of improved sensitivity
and angular resolution when undertaking optical HH surveys.
Prior to this study, 15 numbered HH features, some with
multiple components, were known in the Ophiuchi cloud
core. The current study increases by 15 the number of new HH
objects, or components of known HH objects, and confirms
the reality of three suspected features. An additional five likely
candidate HH features and five possible candidate features
have been identified.
441
Our new data improve the identification of possible driving
sources for the flows. GY 193, a Class III object, is identified
as a likely driver of the HH 224 complex (and perhaps HH
314 and HH 418 as well). DoAr 21, another Class III object, is
identified as the most likely powering source for the HH 419/
O1a/O1b complex. WL 18, a Class II object, is identified as
the driver of the HH 673/673b pair of HH objects. BKLT
J162743244923 is identified as the driving source for HH
416. The lack of detected emission down to the sources
themselves, however, precludes definitive identification of the
great majority of the driving sources.
Combining the results of this [S ii] survey with those of
existing CO molecular outflow surveys leads to the conclusion
that the number of detected outflows in the Ophiuchi cloud
core exceeds the number of Class 0/Class I objects by a factor
of 2, if not 3. Thus, it is clear that Class II and Class III objects
are outflow drivers, as well.
Optical studies of HH objects are limited by the presence of
dust, which precludes the identification of the driving sources
of the outflows. Complementary near-infrared surveys, covering a similarly large area on the sky, along with additional
sensitive, high angular resolution optical data are needed to
connect heavily embedded outflows with those seen in the
optical. In this way, the driving sources for the outflows can be
identified, and correlations between YSO properties and the
outflows they create, can be established.
The [S ii] and continuum filters were kindly loaned by Jeff
Hester. An allocation of telescope time from the Carnegie
Observatories, which made this research possible, is also
gratefully acknowledged. Special thanks goes to David Malin
for providing the Ophiuchi image used in Figure 1 and
providing permission to use it in our paper. Appreciation is
also extended to Bo Reipurth for assigning HH numbers to our
newly detected features and for providing useful comments on
the paper. Partial support for R. L. P. was provided by NSF
grant AST 98-00126, a Research and Creative Activities grant
from the California State University, Sacramento, and International Travel and Small Research Grants from the American
Astronomical Society. M. B. would especially like to acknowledge Chandra Award Number AR1-2005A and AR12005B issued by Chandra X-Ray Observatory Center, which
is operated by the Smithsonian Astrophysical Observatory on
behalf of NASA under contract NAS8-390073. Additional
support for M. B. was provided by NSF grant AST 02-06146.
This research has made use of the NASA/IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with
the National Aeronautics and Space Administration, the
SIMBAD database, operated at CDS, Strasbourg, France, and
NASA’s Astrophysics Data System.
TABLE 5
Unlikely HH Objects
Source
Component
A3.....................................
A4.....................................
U1.....................................
U2.....................................
...
b
...
...
Discovery
GWK98
GWK98
PB03
PB03
Comments
Not apparent in PB03 images
Resolved stars in PB03 images
Not apparent in an overlapping frame
Not apparent in an overlapping frame
TABLE 6
Confirmed HH Objects in the Ophiuchi Core
Object
HH
HH
HH
HH
HH
HH
HH
HH
HH
HH
HH
HH
HH
HH
HH
HH
HH
HH
HH
HH
HH
HH
HH
HH
HH
HH
HH
HH
HH
HH
HH
HH
HH
79 .....................
79b ...................
224 South.........
224 North.........
224 NW1 .........
224 NW2 .........
312 (knot 1) .....
312 (knot 2) .....
312 (knot 3) .....
312 (knot 4) .....
312 (knot 5) .....
313 ...................
314 ...................
416 South.........
416 North.........
417 ...................
418 ...................
419 ...................
420 ...................
420b .................
673 ...................
673b .................
674 ...................
675 ...................
676 ...................
677 ...................
708 ...................
709 ...................
710 ...................
711....................
712 ...................
713 ...................
714 ...................
B1950.0
16 23 45.0
16 23 43.1
16 24 20.6
16 24 18.0
16 24 15.3
16 24 07.2
16 23 00.6
16 22 59.9
16 22 59.0
16 22 58.2
16 22 57.5
16 23 18.1
16 23 37.2
16 24 41.4
16 24 44.0
16 25 25.4
16 23 11.6
16 23 22.9
16 25 35.6
16 25 53.4
16 23 46.2
16 23 50.1
16 24 30.0
16 24 43.5
16 24 45.4
16 24 56.1
16 24 17.0
16 25 00.8
16 22 54.8
16 24 08.9
16 24 48.0
16 25 03.4
16 24 02.2
B1950.0
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
19 48
13 25
42 13
41 17
39 23
37 15
14 37
14 31
14 25
14 18
14 10
15 42
34 09
42 42
42 08
21 24
34 15
23 46
30 32
27 44
31 33
31 54
31 54
35 43
17 06
19 21
45 26
46 24
11 01
11 02
12 21
26 12
35 17
J2000.0
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
16
26
26
27
27
27
27
26
26
26
25
25
26
26
27
27
28
26
26
28
28
26
26
27
27
27
27
27
28
25
27
27
28
27
46.5
44.4
22.6
20.0
17.2
09.1
01.9
01.2
00.3
59.5
58.8
18.9
39.0
43.4
46.0
27.0
13.3
24.4
37.4
55.1
47.9
51.8
31.8
45.4
46.9
57.6
19.0
02.9
56.0
10.2
49.4
05.1
04.0
J2000.0
24 26 31
24 20 07
24 48 54
24 47 57
24 46 04
24 43 56
24 21 23
24 21 17
24 21 11
24 21 04
24 20 56
24 23 06
24 40 52
24 49 21
24 48 46
24 27 59
24 41 00
24 30 30
24 37 07
24 34 18
24 38 16
24 38 37
24 38 34
24 42 22
24 23 45
24 25 59
24 52 06
24 53 01
24 17 47
24 17 43
24 19 00
24 32 49
24 41 58
TABLE 7
Candidate HH Objects in the Observed Ophiuchi Cloud Core
Object
O1a.......................
O1b.......................
O2.........................
O3.........................
O4.........................
O5.........................
P1 .........................
P2: ........................
P3 .........................
P4: ........................
P5: ........................
B1950.0
16
16
16
16
16
16
16
16
16
16
16
23
23
23
23
24
25
24
24
23
24
24
16.3
21.5
16.8
37.1
54.4
58.3
13.1
23.9
54.7
32.9
39.6
B1950.0
24
24
24
24
24
24
24
24
24
24
24
20
22
34
11
19
27
31
19
58
32
31
51
15
15
52
59
34
24
32
40
11
52
J2000.0
16
16
16
16
16
16
16
16
16
16
16
26
26
26
26
27
29
27
27
26
27
27
17.8
23.0
18.5
38.3
55.9
00.0
14.8
25.4
55.7
34.7
41.4
J2000.0
24
24
24
24
24
24
24
24
24
24
24
27
28
41
18
26
34
38
26
05
38
38
35
59
00
36
37
08
04
12
22
51
31
HERBIG-HARO FLOWS IN OPH
443
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