HERBIG-HARO FLOWS in OPHIUCHUS Randy L

Home , 41 Ophiuchi, Sigma Ophiuchi

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; mbarsony@stars.sfsu.edu 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 An alternative method for tracing outflow activity from Although the Ophiuchi molecular cloud core harbors the embedded young stellar objects (YSOs) is via imaging of nearest example of a currently forming stellar association, a shock-excited emission lines. Outflowing material from complete census of its bona fide members and their associated embedded YSOs may interact with the surrounding medium outflows has been elusive. and result in the development of shocks. The subsequent Great progress in the identification of association members cooling of the gas occurs via line radiation, for example, at H has been made over the past decade or so by combining large- or [S ii] in the optical. Extended regions radiating in these scale near-infrared (NIR) and mid-infrared (MIR) surveys, lines, but lacking continuum emission, are known as Herbig- bringing the known number of Ophiuchi cloud members to Haro (HH) objects. 200 (Wilking, Lada, & Young 1989; Barsony et al. 1997, The molecular bipolar outflows discovered in the late 1970s henceforth also BKLT; Bontemps et al. 2001). via mapping of the CO (J =1! 0) line and the highly Characterizing and enumerating the outflows present in the collimated optical HH flows discovered in the early 1980s via Ophiuchi cloud has proven even more challenging: the high their faint [S ii] emission were originally thought to be distinct source density, combined with the relatively poor angular phenomena, due to the apparent disagreement of more than an resolution of large-scale millimetric molecular line maps has order of magnitude in their momentum fluxes. This ‘‘mo- hampered progress in this area. To date, of the 11 molecular mentum problem’’ was resolved in the early 1990s, when the outflows with unambiguously identified exciting sources in possibility of intermittent ejection events was finally taken the Rho Ophiuchi clouds, 10 reside in the central L1688 dark seriously. Additionally, the advent of large-format CCD arrays cloud (Bontemps et al. 1996; Kamazaki et al. 2003). Of these, allowed for the detection, at large distances from their exciting only the two Class 0 sources, VLA 1623 and IRAS sources, of HH objects associated with the molecular outflows 162932422, have had their molecular outflows imaged in of highly embedded YSOs (Graham & Heyer 1990; Go´mez, their entirety (Dent, Matthews, & Walther 1995; Walker et al. Whitney, & Kenyon 1997; Bally et al. 1997). It is now 1986). generally accepted that the two types of outflow phenomena are intimately related. Several [S ii] surveys for HH flows have been undertaken in thecoreofthe Ophiuchi molecular cloud. Wilking et al. 1 Guest observer, Palomar Observatory, which is operated by the California (1997), using the 0.9 m Curtis Schmidt telescope at Cerro Institute of Technology. Tololo Inter-American Observatory and 45 minute [S ii] 2 On assignment to the National Science Foundation, 4201 Wilson Boulevard, Arlington, VA 22230. exposures, identified three new HH objects (HH 312, HH 313, 3 Participant, 2003 NASA Summer Faculty Fellowship Program at Ames and HH 314). They confirmed the presence of two HH Research Center. objects that had previously been identified (HH 79, Reipurth & 420 HERBIG-HARO FLOWS IN OPH 421

Graham 1988; HH 224, first reported by Wilking, Schwartz, 2. OBSERVATIONS AND DATA REDUCTIONS 4 & Blackwell 1987 and confirmed by Reipurth 1994). The Imaging data were acquired with the 1.5 m telescope at Wilking et al. (1997) data revealed that HH 224 had two Palomar Observatory, equipped with a 2048 2048 CCD components (HH 224N and HH 224S). Five candidate HH (CCD No. 13). A narrowband [S ii] filter (wavelength centered objects (C1, C3, C4N/S, C5, and C6 using the Wilking et al. at 6730 A˚ ,with36A˚ FWHM) and a nearby, narrowband designations) were also identified. continuum filter (wavelength centered at 6650 A˚ ,with100A˚ Go´mez, Whitney, & Wood (1998) undertook a similar [S ii] FWHM) were used for the observations. The resulting field of survey of the core of the Ophiuchi molecular cloud, using view was 12A5,withascaleof0B367 pixel1. The obser- the 1.2 m F. L. Whipple Observatory and 20 minute [S ii] vations (Table 1) spanned a number of nights over a 3 month exposures. The Go´mez et al. (1998) survey was not only of period. higher sensitivity than the Wilking et al. (1997) survey, but the ii B For each field, three 20 minute exposures in the [S ] data were also obtained using higher spatial resolution (0 63 vs. filter were co-added, and three 10 minute exposures in the 2B0pixel1). From their survey, Go´mez et al. (1998) were narrowband continuum filter were co-added, resulting in total able to recover the previously known HH objects and integration times of 60 minutes in [S ii] and 30 minutes in the confirmed four of the five Wilking et al. (1997) candidates continuum. By breaking the total integration times into three (C1 = HH 419, C3 = HH 224 NW2, C4N/S = HH 416N/S, separate exposures, it is possible to median-filter the set of and C5 = HH 420). Candidate C6 (=HH 420b) from the images to remove signals that result from randomly appearing Wilking et al. (1997) list was marginally detected, but could cosmic-ray events. not be confirmed using the Go´mez et al. (1998) data. Preliminary data processing was undertaken using tech- In addition, Go´mez et al. (1998) identified two new objects 5 niques described in the IRAF CCDPROC documentation. (HH 417 and HH 418) and additional components (HH 79b Zero-level corrections were determined by taking the median and HH 224 NW1) of known sources. Several other candidate of five zero-second exposure frames. Flat-field images were HH objects (A1, A2, A3, and A4a/b) using the designations in constructed by averaging five individual dome images, Go´mez et al. (1998) were also identified. obtained in each filter, using the sigma-clipping algorithm in Additionally, Wu et al. (2002), using the 60/90 cm Xinglong IRAF.The[Sii] and continuum frames for each field were Schmidt telescope, undertook an 11 deg2 [S ii] survey and separately co-added using the sigma-clipping routine in IRAF confirmed the previously known HH objects in the Ophiuchi to construct final images used for the identification of HH cloud core. These authors also identified seven new groups of objects in Ophiuchi. 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 3. RESULTS from the Ophiuchi cloud core. Our CCD survey for HH objects in the Ophiuchi molecular Most recently, Go´mez et al. (2003, hereafter GSWC03) cloud consists of 16 individual overlapping fields, each with present results from a NIR 2.12 m molecular hydrogen and observations in [S ii] and the nearby, narrowband continuum. [S ii] survey of a portion of the Ophiuchi region. The [S ii] Figure 1 shows our survey fields superposed on the Anglo- component of the survey used the WIYN 3.5 m telescope with Australian Observatory image of the entire Ophiuchi region, the MIMO Mini-Mosaic Imager to cover six areas, each kindly provided by D. Malin. Figure 2 shows our survey region 100 100 on a side. Using these data, Go´mez et al. (2003) relative to that surveyed by Go´mez et al. (1998). Figure 3 confirm the reality of candidate A2 (now HH 674) from the shows a mosaic of the survey regions, composed of the 16 Go´mez et al. (1998) study and identify four new objects individual fields that were observed. (HH 673, HH 675, HH 676, and HH 677). The H2 component Since regions containing shock-excited gas emit emission of the study used the ESO 3.6 m New Technology Telescope lines, HH objects are identified by comparing [S ii]images,in with the SOFI NIR spectrograph/imaging camera to cover which HH features will be seen if they are present, with off-line 0 0 three regions, each approximately 20 20 onaside.TheH2 continuum images in which they will not be visible. Figures 4– survey resulted in the detection of 13 NIR knots, some of 19 show each of the 12A5 12A5 fields as they appear through which appear to be connected to the optically revealed flows. either (1) the [S ii] filter or (2) the nearby continuum filter. In The Go´mez et al. (2003) survey, while providing deep optical each figure, HH objects and a variety of other sources are imaging and a NIR survey for flows for the first time, is labeled. As dust extinction in the optical is severe, it is difficult limited in its spatial coverage to only a portion of the cloud in nearly every case to associate a given HH object with its core. driving source based on the current data alone. Therefore, for Since surveys for HH objects at increasing sensitivities and the purposes of this paper, we will make an effort to identify HH improved pixel scales routinely reveal entirely new sources, object driving sources only in those cases where a possible new components of known flows, or greater detail in known association has previously been attempted, or when the new HH objects, we present a new, improved [S ii] and nearby data presented here are suggestive of an association. For narrowband continuum survey for HH flows in the purposes of the identification of outflow driving sources, the Ophiuchi cloud core. The purpose of this study is to con- data presented here will be most useful when combined with tribute to the eventual identification of all of the outflows and NIR studies, which can penetrate the dusty regions closer to the their exciting sources present in this nearby star-forming driving sources. cloud core.

5 IRAF is distributed by the National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in 4 Electronically published via anon.ftp to ftp.hq.eso.org, directory /pub/ Astronomy, Inc., under cooperative agreement with the National Science Catalogs/Herbig-Haro. Foundation. 422 PHELPS & BARSONY

TABLE 1 Observation Log

Seeing Seeing Field (J2000.0) (J2000.0) Filter Date (arcsec) Filter Date (arcsec)

Field 1 ...... 16 25 56.7 24 11 54.0 [S ii] 1997 May 7 1.3 Continuum 1997 May 7 1.3 Field 2 ...... 16 25 56.5 24 21 09.0 [S ii] 1997 May 6 1.3 Continuum 1997 May 6 1.3 Field 3 ...... 16 26 23.6 24 32 58.0 [S ii] 1997 May 5 1.6 Continuum 1997 May 5 1.6 Field 4 ...... 16 26 40.0 24 41 32.0 [S ii] 1997 May 4 1.5 Continuum 1997 May 4 1.5 Field 5 ...... 16 26 46.4 24 11 19.8 [S ii] 1997 May 7 1.3 Continuum 1997 May 7 1.3 Field 6 ...... 16 26 47.7 24 20 54.0 [S ii] 1997 May 6 1.3 Continuum 1997 May 6 1.3 Field 7 ...... 16 27 06.1 24 37 22.0 [S ii] 1997 Jul 6 2.0 Continuum 1997 Jul 6 2.0 Field 8 ...... 16 27 08.3 24 28 54.2 [S ii] 1997 Jul 7 1.2 Continuum 1997 Jul 7 1.2 Field 9 ...... 16 27 20.7 24 48 19.5 [S ii] 1997 May 4 1.5 Continuum 1997 May 4 1.5 Field 10 ...... 16 27 29.7 24 17 46.0 [S ii] 1997 Jul 8 2.0 Continuum 1997 Jul 8 2.0 Field 11 ...... 16 27 46.7 24 37 26.9 [S ii] 1997 Jul 6 2.0 Continuum 1997 Jul 6 2.0 Field 12 ...... 16 27 56.0 24 28 27.6 [S ii] 1997 Jul 8 2.0 Continuum 1997 Jul 7 1.2 Field 13 ...... 16 28 12.3 24 48 57.5 [S ii] 1997 Jul 5 1.3 Continuum 1997 Jul 5 1.3 Field 14 ...... 16 28 16.4 24 17 30.2 [S ii] 1997 Jul 9 1.8 Continuum 1997 Jul 9 1.8 Field 15 ...... 16 28 34.9 24 39 12.8 [S ii] 1997 May 8 1.4 Continuum 1997 May 8 1.4 Field 16 ...... 16 28 43.8 24 28 30.1 [S ii] 1997 Jul 10 2.0 Continuum 1997 Jul 10 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 as a bow shock pointing almost due east, with its location al- those of previously published surveys. For clarity, we have most due north of SR 21(=Elias 30), we can confidently assert divided the discussion into various sections. The first (x 3.1) that HH 711, at least, is not driven by SR 21. Candidate describes those HH objects that are known as a result of HH object O3, if confirmed to be a real feature, may be driven previously published surveys. Section 3.1 also includes newly by Elias 26 since the [S ii] feature is spatially coincident with detected components and previously suspected, and now the H2 bow shock structure, GSWC03 24a, which itself points confirmed, components of known HH objects. In x 3.2, we away from Elias 26. 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.

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 toasingleH2 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 Fig. 1.—Location of [S ii]surveyregion(boxes) relative to the Oph shock GSWC03 25a and 25b. Based on the morphology of region. The Anglo-Australian Observatory image is used with permission the NIR H2 emission associated with HH 711, which appears from D. Malin. Fig. 2.—Location of [S ii]surveyregion(boxes)relativetotheGo´mez 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)[Sii] image of ﬁeld 1. (b) Off-line image of ﬁeld 1.

This is a very rich ﬁeld of young sources. Among those that (=Elias 22 = GSS 31 = WSB 30 = BKLT J162623242101, are optically visible in Figure 9 are VSSG 24 (=BKLT a well-known infrared companion binary system discovered by J162713241818), the binary SR21 (=Elias 30 = VSSG Chelli et al. 1988), and Elias 23 (=GSS 32 = GY 23, which 23 = BKLT J162710241914 for the primary and BKLT forms a wide, 10B47 separation binary with GY 21; Haisch J162710241921 for the 6B5 separation companion), Elias 26 et al. 2002). (=GSS 37 = VSSG 2 = BKLT J16264224203, a 1B44 sepa- Additionally, there are of order two dozen known or ration binary YSO; Barsony, Koresko, & Matthews 2003a), S1 suspected YSOs in this ﬁeld that appear at NIR and longer (=Elias 25 = GY 70 = BKLT J162634242330, one of the few wavelengths. A detailed discussion of each is beyond the B stars in the Ophiuchi cluster, projected in front of the dust scope of this paper, however, mention is made of a few that lane—S1 is itself a 0B02 binary discovered by Simon et al. may be good candidates for exciting the observed [S ii]fea- 1995), Elias 24 (=BKLT J162624241616), DoAr 24E tures, and those that can be ruled out as exciting sources or

Fig. 5.—(a)[Sii] image of ﬁeld 2. (b) Off-line image of ﬁeld 2. 426 PHELPS & BARSONY Vol. 127

Fig. 6.—(a)[Sii] image of ﬁeld 3. (b) Off-line image of ﬁeld 3.

that have been mentioned by previous authors as possible H2 knot (GSWC03 a1) that is associated with HH 79 points candidate exciting sources. In all cases, a possible association away from VSSG 3 to the southwest, while the H2 knots is based mostly on geometrical considerations. GSWC03 25a/b that are associated with HH 711 lie on the InFigure9(ﬁeld6),VSSG3(=LFAM18=ROXs17=GY opposite side of VSSG 3 and point away from VSSG 3 toward 135 = BKLT J162649242005) is a K6 spectral type, Class III the northeast. Since VSSG 3 lies on a line between these YSO, seen through a visual extinction of AV = 16 (Luhman & sources, we suggest that VSSG 3 is the exciting source for Rieke 1999). It is somewhat unusual in being a centimeter HH 711 and perhaps part of HH 79. continuum source (Leous et al. 1991). Furthermore, VSSG 3 is VSSG 27 (=LFAM9 = GY 51 = BKLT J162630242258) less than 1 million years old, based on its location on pre– is a 1B2 separation binary located at the apex of the large main-sequence evolutionary tracks (Wilking et al. 2001). The diffuse nebulosity and dust structure that lies behind S1 (see

Fig. 7.—(a)[Sii] image of ﬁeld 4. (b) Off-line image of ﬁeld 4. No. 1, 2004 HERBIG-HARO FLOWS IN OPH 427

Fig. 8.—(a)[Sii] 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 neither SR 21 (Class II, F4 spectral type) nor VSSG 28 object with a K3–M1 spectral type seen through a visual (Class II K8 spectral type) can be ruled out as the exciting extinction of AV = 22 (Luhman & Rieke 1999; Greene & source for HH 79b, the presence of other nearby NIR YSOs Meyer 1995). This object is also a centimeter continuum suggests additional evidence is required for correct identi- emitter (Leous et al. 1991). It may be a candidate for the fication of the exciting source for HH 79b. In particular, emission observed in HH 79. VSSG 7 (=GSS 41 = IRS 22 = BKLT J162655242030) is a Two sources, SR 21 (=Elias 30 = VSSG 23) and VSSG 28 possible exciting source for HH 79b because of its proxim- (=GSS 39 = Elias 27 = BKLT J162645242309), have pre- ity and alignment with the outflow. Other than being tenta- viously been proposed as candidates for the exciting source of tively classified as a Class III object, very little is known HH 79b (Wilking et al. 1997; Go´mez et al. 1998). Although about this source (Bontemps et al. 2001). VSSG 11

Fig. 9.—(a)[Sii] image of ﬁeld 6. (b) Off-line image of ﬁeld 6. 428 PHELPS & BARSONY Vol. 127

Fig. 10.—(a)[Sii] image of ﬁeld 7. (b) Off-line image of ﬁeld 7.

(=IRS 19 = BKLT J162643241635), another nearby YSO, Luhman & Rieke 1999) and has not been detected at centimeter is a Class III radio emitter of M3 spectral type, seen through (Leous et al. 1991), MIR (Bontemps et al. 2001), or X-ray 6 AV = 14, and judged to be have an age less than 1 10 yr (Imanishi, Koyama, & Tsuboi 2001) wavelengths. Never- (Wilking et al. 2001), and is another candidate exciting source theless, it is associated with a NIR reflection nebulosity, which for HH 79b. shares the CO outflow axis (Kamazaki et al. 2003). However, For completeness, we also plot the location of GY 30 (BKLT the GY 30 outflow is directed along a northwest-southeast axis, J162625242303) in field 9, since it was found to be the driver and thus cannot be responsible for any of the [S ii]emission of a recently discovered CO outflow in the region (Kamazaki features seen in this field. et al. 2003). Very little is known about GY 30, since it was too HH 224.—Figure 12 (field 9) shows the region containing faint to be included in NIR spectroscopic surveys (e.g., the HH 224 complex. All of the previously known substructure

Fig. 11.—(a)[Sii] image of ﬁeld 8. (b) Off-line image of ﬁeld 8. No. 1, 2004 HERBIG-HARO FLOWS IN OPH 429

Fig. 12.—(a)[Sii] image of ﬁeld 9. (b) Off-line image of ﬁeld 9.

(HH 224 North, HH 224 South, HH 224 NW1, HH 224 constructed by combining portions of the above mentioned NW2) has been recovered. Faint, diffuse [S ii] emission three fields. extends from HH 224S to the northwest, as hinted by the Wilking et al. (1997) and Go´mez et al. (1998) discuss the Go´mez et al. (1998) data and suggested by them. Our data, possible driving source for HH 224, indicating SR 24 as a however, reveal northward extended emission (HH 714) in candidate, based on its YSO characteristics, even though it is thefieldjusttothenorthinFigure10(field7)andtothe clearly not aligned with the flow. SR 24, therefore, can be west in Figure 7 (field 4) of Figure 12. This feature, HH 714, ruled out as the driving source for the outflow. The spatial extends through GY 194 and may be a component of HH alignment of GY 193 with most of the HH 224 emission 224 or a separate outflow, forming a ‘‘fork’’ in the emission suggests it remains a candidate for the driving source, as near GY 193. For this reason, it has been given a separate discussed by both Wilking et al. (1997) and Go´mez et al. HH designation. Figure 21 shows a close-up of the area, (1998). However, the newly detected forked emission

Fig. 13.—(a) [S ii] image of ﬁeld 10. (b) Off-line image of ﬁeld 10. 430 PHELPS & BARSONY Vol. 127

Fig. 14.—(a)[Sii] image of ﬁeld 11. (b) Off-line image of ﬁeld 11.

(HH 714) extending beyond GY 193 toward the north and in both Figure 10 (field 7) and Figure 21, which clearly shows the additional emission continuing beyond GY 193 toward the that IRS 43 is not the driving source for any component of HH northwest complicates this interpretation. In fact, the type of 224. For reference, we have also plotted the positions of a few major bow shock formed by HH 224 and its associated shock nearby near-infrared YSOs: GY 224 (a Class I/flat-spectrum features strongly point to a very young embedded source protostar), IRS 42 (a flat-spectrum protostar) and GY 253 (a farther to the northwest, as pointed out by B. Reipurth Class III source). (2003, private communication). It has also been suggested Although the exciting source of the extended HH 224 that the Class I protostar, IRS 43 (=YLW 15), might be flow remains to be identified, the extent of the HH 224 responsible for the emission from HH 224 NW1 (Grosso et al. emission can now be traced to roughly 0 .15, which at a 2001). For this reason, we have plotted the location of IRS 43 distance of 125 pc (de Geus, de Zeeuw, & Lub 1989; de

Fig. 15.—(a)[Sii] image of ﬁeld 12. (b) Off-line image of ﬁeld 12. No. 1, 2004 HERBIG-HARO FLOWS IN OPH 431

Fig. 16.—(a)[Sii] image of ﬁeld 13. (b) Off-line image of ﬁeld 13.

Geus 1992) for Ophiuchi, corresponds to a linear extent the north of SR 4 itself. HH 312 is in rough alignment of 1/3 pc. with an H2 emission knot, GWSC 2003 8a. However, no H2 HH 312.—Figure 5 (field 2) and Figure 22 show the counterpart to the optical flow is found, suggesting the exciting region containing the jetlike chain of knotty emission asso- source may actually be at some distance from the optically ciated with HH 312. Our data reveal at least five knots of visible flow. emission, in somewhat better detail than previous studies. We suggest that BKLT J162532241754, which is also in As discussed by both Wilking et al. (1997) and Go´mez et al. rough alignment with the HH 312 flow, is a possible exciting (1998), the spatial coincidence of the HH 312 flow with SR 4 source, although this source too is not in direct alignment suggests it is a candidate for the driving source. The termi- with HH 312 (see Fig. 5a). The possibility of a precessing nus of the flow axis, however, is offset significantly to flow, and the lack of emission down to SR 4, preclude a

Fig. 17.—(a)[Sii] image of ﬁeld 14. (b) Off-line image of ﬁeld 14. 432 PHELPS & BARSONY

Fig. 18.—(a)[Sii] image of field 15. (b) Off-line image of field 15. definitive assignment of the driving source using the current analysis of knots A1, A3, and A4 as forming a curved, C-type data. bow-shock moving toward the observer, within the CO outflow HH 313.—Figure 5 (field 2) also shows the region containing powered by the Class 0 protostar, VLA 1623. HH 313. A close-up view is shown in Figure 23. HH 313 is HH 314.—Figure 7 (field 4) shows the region containing associated with the VLA 1623 outflow. Our data confirm the HH 314, while Figure 24 shows a close-up view of the source. HH nature of the source and its association with an H2 emission From their data, Go´mez et al. (1998) describe HH 314 as a knot, H5 (Dent et al. 1995) or A (Davis & Eisloffel 1995), as well-defined [S ii] knot, while our data reveal HH 314 to be first pointed out by Wilking et al. (1997). Furthermore, our data composed of two diffuse, extended [S ii] components extend- show that HH 313 is somewhat to the northwest of the H2 ing toward the northwest and southeast of a pointlike [S ii] emission knot, A3 (Davis et al. 1999), as expected from their source. Intriguingly, HH 314 is aligned with the portion of

Fig. 19.—(a)[Sii] 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 ...... RG88 RG88 = Reipurth & Graham 1988 b GWK98 GWK98 = Go´mez et al. 1998 HH 224 ...... South R94 R94 = Wilking et al. 1987 North WSFF97 WSFF97 = Wilking et al. 1997 NW2 WSFF97 WSFF97 source C3, conBrmed by GWK98 NW1 GWK98 Emission connects 224 NW1, 224 NW2, 224 North and 224 South HH 312 ...... WSFF97 Jetlike series of knots HH 313 ...... WSFF97 HH 314 ...... WSFF97 HH 416 ...... South WSFF97 WSFF97 source C4 South, conBrmed by GWK98 North WSFF97 WSFF97 source C4 North, conBrmed by GWK98 HH 417 ...... GWK98 HH 418 ...... GWK98 HH 419 ...... WSFF97 WSFF97 source C1, conBrmed by GWK98 HH 420 ...... WSFF97 WSFF97 source C5, conBrmed by GWK98 HH 548 ...... WWYDC02 WWYDC02 = Wu et al. 2002 HH 549 ...... A–C WWYDC02 HH 550 ...... WWYDC02 HH 551 ...... WWYDC02 HH 552 ...... WWYDC02 HH 553 ...... A–E WWYDC02 HH 554 ...... WWYDC02

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 435

Fig. 26.—[S ii] image of HH 417 Fig. 24.—[S ii] image of HH 314

HH 418 to be an extended, nebular feature, although its HH 224 NW2 that extends through the candidate driving location near the edge of a single frame in our survey limits source GY 193. This suggests at least the possibility that HH further interpretation of the object. An additional feature 314 and the HH 224 complex are related bipolar flows from (object O2) may be associated with HH 418, but as discussed GY 193. Based on proximity arguments, GY 93, a Class II below, its reality awaits confirmation. It is even possible that source (Greene & Lada 1997), is also a candidate for driving O2 and HH 418 are part of the HH 224 flow. the HH 314 outflow. HH 419.—Figure 6 (field 3) shows the region containing HH HH 416N/S.—Figure 12 (field 9) shows the region 419, a diffuse feature first identified by Wilking et al. (1997) and containing the feature, HH 416N/S. Figure 25 shows a close- confirmed by Go´mez et al. (1998). Figure 28 shows a close-up up view of the sources. HH 416N is also visible in Figure 16 of the feature. Faint extensions of HH 419 appear to the (field 13). Wilking et al. (1997) suggested WSB 58, shown in northwest and are given the designations O1a and O1b, pending Figure 16, is the driving source, although the northeast/ confirmation by future observations. Together HH 419, O1a, southwest alignment of HH 416N/S and the location of WSB and O1b form an arc, concave toward the southwest, that leads 58 to the east precludes this association. Go´mez et al. (1998) toward DoAr 21(=GSS 23), a weak-lined T Tauri star (WTTS) suggest IRS 54 as an alternative. IRS 54, however, is quite as classified by Bouvier & Appenzeller (1992). Diffuse emis- distant from HH 416N/S, as revealed in Figure 15 (field 12). sion, seen in both the [S ii] and continuum images, also extends HH 416N has a morphology resembling a bow shock moving toward the northwest of DoAr 21. Although classified as a to the northeast, while HH 416S has a diffuse jetlike flow of WTTS, DoAr 21 lies above the 1 Myr isochrone (Wilking et al. gas, toward the southwest of HH 416N, that terminates at a 2001) and possesses a gas-phase disk (Bary, Weintraub, & point source visible in the continuum image. It is likely that this Kastner 2002). We therefore consider DoAr 21 to be a candidate point source (BKLT J162743244923) is the driving source for the HH 419/O1a/O1b outflow. for HH 416N/S. HH 420/420b.—Figure 18 (field 15) reveals the presence of HH 417.—Figure 19 (field 16) shows the Y-shaped the diffuse feature, HH 420. Go´mez et al. (1998) were unable morphology of HH 417, which is highlighted in the close-up to confirm the reality of HH 420b (candidate C6 in Wilking view shown in Figure 26. Go´mez et al. (1998) associate et al. 1997), but our data do establish its reality since the HH 417 with SR 13, although the axis of HH 417 does not feature is visible in [S ii], but not in the continuum, in both point directly toward that source. By contrast, the jetlike Figure 18 (field 15) and Figure 19 (field 16). Additionally, a component of HH 417 ends directly on the NIR source, BKLT feature (O5) that may be associated with HH 420b is found in J162825242800. We suggest this is the exciting source for at field 15. Its absence in the overlapping field 16 leaves its least this component of HH 417. The curved component of reality in need of confirmation, although its proximity to the HH 417 may either be excited by the same NIR source or may bright star SAO 184412 may simply have made its detection be the result of a superposition of HH flows powered by difficult. A close-up of the region is shown in Figure 29. nearby, but as of yet unidentified driving sources. HH 548–HH 554.—These features, detected by Wu et al. HH 418.—Figure 7 (field 4) also shows the presence of (2002) are outside of our survey region. HH 418, which Go´mez et al. (1998) describe as a nebular object. A close-up view is shown in Figure 27. Our data reveal 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 418 436 PHELPS & BARSONY Vol. 127

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 HH 674.—Go´mez et al. (1998) describe their candidate A2 source to be considered real. Multiple detections are possible as a small nebular [S ii] emission object. The feature has been using identifications from previous studies combined with the confirmed by the Go´mez et al. (2003) study, in which it was current survey or by using overlapping fields in only the given the designation HH 674 and GSWC03 7d based on an current survey. associated H2 detection. Figure 10 (field 7) and Figure 14 HH 420b.—The reality of HH 420b is confirmed with the (field 11) reveal the presence of this feature in our [S ii]images current data, as discussed above. but not in the continuum, thus providing an independent 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 Go´mez 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 close- up 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 Go´mez 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. Fig. 29.—[S ii] image of the HH 420/HH 420b region No. 1, 2004 HERBIG-HARO FLOWS IN OPH 437

TABLE 3 Confirmed and Independently Discovered HH Objects

Source Component Discovery Comments

HH 420 ...... b WSFF97 WSFF97 source C6, conBrmed by PB03; PB03 = Phelps & Barsony (2003), this paper HH 673 ...... GSWC03, PB03 Detected in three overlapping frames HH 674 ...... GWK98 GWK98 candidate A2, conBrmed by GSWC03, PB03 HH 675 ...... GSWC03, PB03 Detected in two overlapping frames HH 676 ...... GSWC03, PB03 Detected in two overlapping frames HH 677 ...... GSWC03, PB03 Single detection in PB03, but detected by GSWC03 HH 708 ...... GWK98 GWK98 candidate A1, conBrmed by PB03 HH 709 ...... GWK98 GWK98 candidate A4a, conBrmed by PB03 HH 710 ...... PB03 Detected in two overlapping frames HH 714 ...... PB03 Possible forked branch of HH 224NW2 extending to the northwest HH 711...... PB03 Detected in two overlapping frames HH 712 ...... PB03 Detected in two overlapping frames HH 713 ...... PB03 Detected in two overlapping frames

the proximity to HH 677 strongly suggests its reality, with SR 10 confirmation of its reality. Figure 31 shows a close-up of the being a candidate driving source for both HH 677 and O4. HH 674 region. As discussed by Go´mez et al. (1998), there are HH 708.—Go´mez et al. (1998) report a faint, filamentary, 13 YSO sources within 50 of HH 674 (A2 in that study). candidate HH object (their object A1) near the sources, Go´mez et al. (2003) list IRS 44 (=GY 269), a Class I source ROXs 20A (=WSB 45B KLT J162714 245132) and located 7600 away, as the likely driving source for HH 674. ROXs 20B (=WSB 46B KLT J162715 245137), which they However, given the proximity to HH 674 of several NIR YSOs in the region, no definitive identification of the driving identify as possible driving source. Figure 12 (field 9) and Figure 34 show our data for this source. Its presence in the [S ii] source for this feature is possible with the existing data. image but not in the continuum, coupled with the detection by HH 675.—Figure 12 (field 9) and Figure 14 (field 11) reveal Go´mez et al. (1998), confirms its HH nature. Our data do not a feature, independently detected by Go´mez et al. (2003), and allow for a more definitive identification of the driving source. given the designation HH 675 in that study. HH 675 is in the HH 709.—Go´mez et al. (1998) also list two candidate HH general vicinity of HH 674 (Fig. 31). The infrared YSOs objects, A4a and A4b. Figure 16 (field 13) shows our survey IRS 51, IRS 53, and GY 301, have been proposed as possible images for the region containing these candidates, while driving sources for HH 675 (Go´mez et al. 2003). We propose Figure 35 shows a close-up of the region. Candidate A4a is that other nearby YSOs in the region also be considered as apparent in the [S ii] images, but not in the continuum, which possible exciting sources for HH 675. when coupled with the detection by Go´mez et al. (1998), HH 676.—Figure 13 (field 10) and Figure 15 (field 12) confirms its reality as an HH object (now designated HH 709). reveal a feature, also found independently by Go´mez et al. Go´mez et al. (1998) candidate A4b, however, is resolved into (2003) and given the designation HH 676 in that study. A ii close-up view of HH 676 is shown in Figure 32. Exciting stars in both our [S ] and continuum images, and hence it is ruled out as an HH object. sources for HH 676 could be any of Elias 34, Elias 35, Elias 36, HH 710.—Figure 5 (field 2) and Figure 4 (field 1) reveal a or even SR 10. Note that both Elias 34 and Elias 36 are newly detected feature, HH 710, interior to the prominent dust subarcsecond binaries (see Barsony et al. 2003a and references ring seen in both figures. A close-up view is shown in Figure 36. 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 Go´mez 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 Fig. 31.—[S ii] image of the HH 674/ HH 675 region 438 PHELPS & BARSONY Vol. 127

Fig. 34.—[S ii] image of HH 708

Pending confirmation, these features, listed in Table 4, are listed only as candidate HH objects. Fig. 32.—[S ii] image of the HH 676 and HH 712 region O1a/b.—As discussed in x 3.1, apparent extensions of HH 419 in Figure 6 (field 3) appear to the northwest of that ThatHH710isseenin[Sii] but not the continuum, and that the feature in [S ii] but not in the continuum in the only survey feature is found in two overlapping CCD frames, confirms its frame that covers that region. A composite view of the HH nature as an HH object. No definitive association with a driving 419/O1 region is shown in Figure 28. Pending confirmation, source can be made using the current data. these features are given the designations O1a and O1b, HH 711.—Figure 9 (field 6) and Figure 13 (field 10) reveal although their connection to HH 419 suggests a high like- a new HH object (HH 711). A close-up view of the feature is lihood they are real features. We propose DoAr 21 as the presented in Figure 37. That the feature is found in two candidate driving source for the HH 419/O1 complex, as dis- overlapping fields (fields 6 and 10), and seen in [S ii] but not cussed in x 3.1. the continuum, confirms its reality. Further discussion of O2.—A single field, shown in Figure 7 (field 4), reveals the HH 711 is presented along with HH 79/79b in x 3.1. presence of a probable [S ii] feature, which is not seen in the HH 712.—Figure 13 (field 10) and Figure 17 (field 14) continuum image. A close-up view is shown in Figure 27. reveal a newly detected feature, HH 712. It is found in the same Given the detection in only a single frame, because of the lack general region as HH 676 (Fig. 32). Its presence in two of overlap of that field in the survey, confirmation of the separate frames, along with its detection in the [S ii] images but reality of O2 is required. However, its location near a known not in the continuum, indicate it is a real feature. Candidate object (HH 418) is suggestive of its HH nature. Little can be driving sources for HH 712 include SR 21 and Elias 34. said about the driving source based on our current data. HH 713.—Figure 14 (field 11) and Figure 15 (field 12) O3.—This feature, shown in Figure 9 (field 6) and in a reveal a newly detected feature, HH 713, in the [S ii]images close-up view in Figure 20, appears only in this field, which but not in the continuum, confirming its reality. A close-up is had no overlap with other fields in our survey. Its appearance shown in Figure 38. The driving source remains unidentified, in the [S ii] image but not in the continuum image, coupled although several infrared sources (BKLT J162812243207, with its location in a region containing several other HH BKLT J162813243128, BKLT J162813243139 and BKLT objects (HH 79/79b and HH 711), suggests it is a likely HH J162813243249) are located nearby. object. Additionally, as discussed in x 3.1 with HH 79/79b, O3 HH 714.—HH 714 may be a forked extension of the HH is positionally coincident with a H2 bow-shock feature imaged 224 complex, or a separate flow, and is discussed with HH 224 by Go´mez et al. (2003), whose axis of symmetry and mor- in x 3.1. phology point back to Elias 26 as the exciting source. O4.—There is a convincing detection of a feature in the 3.3. Candidate HH Objects [S ii] portion of Figure 15 (field 12) but not in the continuum ii Objects that are considered to be likely candidates are given images. This feature, which is also present in the [S ]image the designation ‘‘O.’’ In all cases, these features show up of Go´mez et al. (2003), appears to be associated with HH 677. prominently in the [S ii] images but not in the continuum SR10, a Class II object according to Bontemps et al. (2001), is images. In most cases, however, there is only a single detec- a likely exciting source for both HH 677 and O4 (See x 3.2 on tion due to lack of overlapping frames in our survey mosaic. 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 Go´mez et al. (2003) leads us to classify O4 as a candidate HH object pending confirmation.

Fig. 33.—[S ii] image of the region containing HH 677 and candidate HH object O4. 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) Fig. 38.—[S ii] image of HH 713 in which it would be expected to be seen, means that the reality of the feature cannot be confirmed. Its proximity to the designation of P4 and P5 as candidate HH objects, in need of bright star SAO 184412, however, may simply make detection confirmation. of O5 in Figure 19 difficult, and hence confirmation for the reality of O5 is needed. 3.4. Unlikely HH Objects Objects that are considered to be marginal candidates are For completeness, several features that have been proposed given the designation ‘‘P.’’ In many cases, the nature of their as candidate HH objects, but are unlikely to be real are dis- detections is similar to the candidate HH objects discussed cussed. For those that were considered initially during our above, but the detection was considered to be less convincing. current survey, the designation ‘‘U’’ is given to indicate the In other cases, a second detection failed to materialize as unlikely reality of the feature. A summary of these features is expected, resulting in questionable reliability of the initial giveninTable5. detection. A3.—Go´mez et al. (1998) describe their candidate A3 as a P1.—A marginal [S ii] feature is detected in Figure 10 [S ii] nebular object in need of confirmation. The location of (field 7) but not in the continuum image. A close-up is shown A3 is shown in our Figure 18 (field 15). No feature is present in Figure 39. The marginal nature of the single detection, in either the [S ii] or continuum filters, and we cannot, because of the lack of overlapping images of the region, leads therefore, confirm its reality with the current data. to the designation of P1 as a candidate HH object in need of A4b.—As discussed above, and shown in Figure 16 confirmation. (field 13), Go´mez et al. (1998) candidate A4b is resolved P2.—Similarly, a marginal feature is detected in [S ii]but intostarsinbothour[Sii] and continuum images and hence is not the continuum, as revealed in Figure 11 (field 8). A close- ruled out as an HH object. up is shown in Figure 40. No overlapping fields are available U1 and U2.—As indicated in Figure 11 (field 8), two to confirm its detection, hence it is designated as a candidate features labeled U1 and U2 are identified in the [S ii]image, HH object in need of confirmation. If confirmed as an HH but do not appear in the continuum. However, they should object, however, object P2 may be powered by GY 264. also appear in the [S ii] image shown in Figure 10 (field 7) and P3.—A marginal [S ii] feature is also detected in Figure 8 do not. The lack of detection in field 7 results in their (field 5), but not in the continuum image. A close-up of the classification as unlikely candidates, but for completeness in region is shown in Figure 41. No overlapping images of the the event of future HH searches in Ophiuchi, they are region are available, leading to a single detection and hence presented here. the designation of P3 as a candidate HH object in need of confirmation. 4. DISCUSSION P4 and P5.—Marginal features are found in the [S ii] images in Figure 14 (field 11) but not in the continuum image. The coordinates of the HH objects are listed in Table 6. They are located in the vicinity of HH 674 (Fig. 31). The Table 7 lists the coordinates of the candidate HH objects, both marginal nature of the single detections, resulting from those that are likely and those with marginal detections. The the lack of overlapping images of the region, leads to 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 Ophcloudcore,comparedwithpreviousoptical 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. 440 PHELPS & BARSONY Vol. 127

TABLE 4 Candidate HH Objects

Source Component Discovery Comments

O1a, O1b...... PB03 Extended emission northeast of HH 419 O2...... PB03 Possible extension of HH 418 O3...... PB03 No overlapping frames, prominent in [S ii] O4...... PB03 No overlapping frames, prominent in [S ii] O5...... PB03 Likely component of HH 420b P1 ...... PB03 No overlapping frames, marginal [S ii] P2 ...... PB03 No overlapping frames, marginal [S ii] P3 ...... PB03 No overlapping frames, marginal [S ii] near field edge P4 ...... PB03 Marginal [S ii], possibly associated with HH 674 P5 ...... PB03 Marginal [S ii], possibly associated with HH 674 of 33 HH objects or components of HH objects (Table 6) and is beyond the scope of this work. Making the realistic, yet 11 candidate HH objects or components of HH objects conservative, approach of assuming that each feature/compo- (Table 7). In total, 44 distinct regions of shocked gas have nent listed in Tables 6 and 7 with the same primary numerical been traced by [S ii] emission. A number of these features can designation is part of a single flow results in an estimate of 32 be grouped together as likely belonging to a single outflow: [S ii] outflows. There are, therefore, of order 50 or so known e.g., the five knots of HH 312, at least four components outflows in the Ophiuchi cloud core, when the present [S ii] of HH 224, the three components of the HH 419/O1a/O1b and published CO outflow data are combined. This number is outflow, and pairs of objects such as HH 416N/S, HH 673/ a lower limit, in the sense that yet more outflows await 673b, and HH 79/711. Furthermore, of the 15 known CO discovery through large-scale near-infrared H2 mapping (e.g., outflows in the cloud core (Bontemps et al. 1996; Sekimoto Gomez et al. 2003). et al. 1997; Kamazaki et al. 2003), we detect the optical manifestations from only one (HH 313 of the VLA 1623 4.2. Driver Characteristics outflow). It is challenging, and often impossible, to identify the The number of outflows in Ophiuchi exceeds the number exciting source for a given HH object from only the data of known Class 0 and Class I objects (of order two dozen) by presented here. This is a consequence of the fact the optically a factor of 2, if not 3 (Bontemps et al. 2001). Assuming that visible HH objects often appear far from their exciting all, or nearly all Class 0 and Class I sources have been found, sources, where the extinction is low enough to allow them to this leads to the inevitable conclusion that Class II and pos- be detected. Furthermore, flows are not necessarily straight: sibly Class III objects must necessarily be outflow drivers as the HH 224 complex shows a bending, as does the HH 419/ well. O1a/O1b flow and the famous VLA1623 CO flow (Dent et al. In fact, two of the three CO outflow searches toward 1995)—intriguingly, the curvature for all three of these large- Ophiuchi to date have been biased against finding outflows scale flows is concave toward the southwest, possibly a result driven by Class II or Class III objects. The most compre- of shaping by the ambient magnetic field within the cloud as hensive CO outflow search toward Ophiuchus, surveying discussed by Dent et al. (1995). Finally, a single HH object 14 YSOs, was targeted exclusively toward Class I and Class 0 may have many possible candidate exciting sources. There are objects (Bontemps et al. 1996). The Sekimoto et al. (1997) CO exceptions, however, such as the case of WL 18 (see Fig. 30), outflow search of five objects was aimed toward hard X-ray which is symmetrically placed between two HH objects, emitters, which are preferentially found among Class I objects, HH 673/673b. although one of the four outflow drivers in their survey was A comprehensive enumeration and evaluation of known a Class II object. Only the most recent CO outflow search YSOs as drivers for each of the HH objects here presented

Fig. 39.—[S ii] image of the marginal candidate HH object P1. Fig. 40.—[S ii] image of the marginal candidate HH object P2. No. 1, 2004 HERBIG-HARO FLOWS IN OPH 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/ Fig. 41.—[S ii] image of the marginal candidate HH object P3. O1a/O1b complex. WL 18, a Class II object, is identified as the driver of the HH 673/673b pair of HH objects. BKLT toward Ophiuchi was unbiased in that the survey region did J162743244923 is identified as the driving source for HH not depend on the spectral energy distribution (SED) clas- 416. The lack of detected emission down to the sources sification of the possible driving source (Kamazaki et al. themselves, however, precludes definitive identification of the 2003). As a result of their unbiased search and high spatial great majority of the driving sources. resolution, three CO outflows with either Class II or Class III Combining the results of this [S ii] survey with those of driving sources were found. existing CO molecular outflow surveys leads to the conclusion In our present [S ii] outflow survey, which is also unbiased that the number of detected outflows in the Ophiuchi cloud with respect to the SED classification of outflow drivers, we core exceeds the number of Class 0/Class I objects by a factor find that among the most secure candidates for outflow drivers of 2, if not 3. Thus, it is clear that Class II and Class III objects there are Class II and Class III objects. Examples are WL 18, a are outflow drivers, as well. Class II object driving HH 673/673b (see Fig. 30), and Optical studies of HH objects are limited by the presence of DoAr 21, a Class III object, driving HH 419/O1a/O1b (see dust, which precludes the identification of the driving sources Fig. 28). of the outflows. Complementary near-infrared surveys, cover- ing a similarly large area on the sky, along with additional 4.3. Open Questions and Future Work sensitive, high angular resolution optical data are needed to connect heavily embedded outflows with those seen in the The results of this study have brought into sharp focus the optical. In this way, the driving sources for the outflows can be question of when bipolar outflows turn off during YSO evo- identified, and correlations between YSO properties and the lution. There is now ample evidence of bipolar outflow ac- outflows they create, can be established. tivity among the earliest protostellar (Class 0) stage (Andre´, Ward-Thompson, & Barsony 2000), as well as the later ‘‘self- embedded’’ (Class I) stage (e.g., Bontemps et al. 1996 and ii Sekimoto et al. 1997). Our current study, as well as future The [S ] and continuum filters were kindly loaned by Jeff high-sensitivity, high angular resolution studies (especially Hester. An allocation of telescope time from the Carnegie Observatories, which made this research possible, is also imaginginthenear-infraredH2 shock-emission lines) will allow unbiased searches for outflows driven by pre–main- gratefully acknowledged. Special thanks goes to David Malin sequence stars with optically thick (Class II) or optically thin for providing the Ophiuchi image used in Figure 1 and (Class III) disks for the first time. providing permission to use it in our paper. Appreciation is Once a significant number of outflow driver identifications also extended to Bo Reipurth for assigning HH numbers to our will have been made among the Class II and Class III pop- newly detected features and for providing useful comments on ulations, correlation of stellar parameters (such as rotational the paper. Partial support for R. L. P. was provided by NSF speed, magnetic field strength), disk parameters, and outflow grant AST 98-00126, a Research and Creative Activities grant properties can be advanced via high-resolution, near-infrared from the California State University, Sacramento, and Inter- spectroscopy of the driving sources. national Travel and Small Research Grants from the American Astronomical Society. M. B. would especially like to ac- knowledge Chandra Award Number AR1-2005A and AR1- 5. SUMMARY 2005B issued by Chandra X-Ray Observatory Center, which Our survey highlights the advantage of improved sensitivity is operated by the Smithsonian Astrophysical Observatory on and angular resolution when undertaking optical HH surveys. behalf of NASA under contract NAS8-390073. Additional Prior to this study, 15 numbered HH features, some with support for M. B. was provided by NSF grant AST 02-06146. multiple components, were known in the Ophiuchi cloud This research has made use of the NASA/IPAC Infrared Sci- core. The current study increases by 15 the number of new HH ence Archive, which is operated by the Jet Propulsion Labo- objects, or components of known HH objects, and confirms ratory, California Institute of Technology, under contract with the reality of three suspected features. An additional five likely the National Aeronautics and Space Administration, the candidate HH features and five possible candidate features SIMBAD database, operated at CDS, Strasbourg, France, and have been identified. NASA’s Astrophysics Data System.

TABLE 5 Unlikely HH Objects

Source Component Discovery Comments

A3...... GWK98 Not apparent in PB03 images A4...... b GWK98 Resolved stars in PB03 images U1...... PB03 Not apparent in an overlapping frame U2...... PB03 Not apparent in an overlapping frame TABLE 6 Confirmed HH Objects in the Ophiuchi Core

Object B1950.0 B1950.0 J2000.0 J2000.0

HH 79 ...... 16 23 45.0 24 19 48 16 26 46.5 24 26 31 HH 79b ...... 16 23 43.1 24 13 25 16 26 44.4 24 20 07 HH 224 South...... 16 24 20.6 24 42 13 16 27 22.6 24 48 54 HH 224 North...... 16 24 18.0 24 41 17 16 27 20.0 24 47 57 HH 224 NW1 ...... 16 24 15.3 24 39 23 16 27 17.2 24 46 04 HH 224 NW2 ...... 16 24 07.2 24 37 15 16 27 09.1 24 43 56 HH 312 (knot 1) ..... 16 23 00.6 24 14 37 16 26 01.9 24 21 23 HH 312 (knot 2) ..... 16 22 59.9 24 14 31 16 26 01.2 24 21 17 HH 312 (knot 3) ..... 16 22 59.0 24 14 25 16 26 00.3 24 21 11 HH 312 (knot 4) ..... 16 22 58.2 24 14 18 16 25 59.5 24 21 04 HH 312 (knot 5) ..... 16 22 57.5 24 14 10 16 25 58.8 24 20 56 HH 313 ...... 16 23 18.1 24 15 42 16 26 18.9 24 23 06 HH 314 ...... 16 23 37.2 24 34 09 16 26 39.0 24 40 52 HH 416 South...... 16 24 41.4 24 42 42 16 27 43.4 24 49 21 HH 416 North...... 16 24 44.0 24 42 08 16 27 46.0 24 48 46 HH 417 ...... 16 25 25.4 24 21 24 16 28 27.0 24 27 59 HH 418 ...... 16 23 11.6 24 34 15 16 26 13.3 24 41 00 HH 419 ...... 16 23 22.9 24 23 46 16 26 24.4 24 30 30 HH 420 ...... 16 25 35.6 24 30 32 16 28 37.4 24 37 07 HH 420b ...... 16 25 53.4 24 27 44 16 28 55.1 24 34 18 HH 673 ...... 16 23 46.2 24 31 33 16 26 47.9 24 38 16 HH 673b ...... 16 23 50.1 24 31 54 16 26 51.8 24 38 37 HH 674 ...... 16 24 30.0 24 31 54 16 27 31.8 24 38 34 HH 675 ...... 16 24 43.5 24 35 43 16 27 45.4 24 42 22 HH 676 ...... 16 24 45.4 24 17 06 16 27 46.9 24 23 45 HH 677 ...... 16 24 56.1 24 19 21 16 27 57.6 24 25 59 HH 708 ...... 16 24 17.0 24 45 26 16 27 19.0 24 52 06 HH 709 ...... 16 25 00.8 24 46 24 16 28 02.9 24 53 01 HH 710 ...... 16 22 54.8 24 11 01 16 25 56.0 24 17 47 HH 711...... 16 24 08.9 24 11 02 16 27 10.2 24 17 43 HH 712 ...... 16 24 48.0 24 12 21 16 27 49.4 24 19 00 HH 713 ...... 16 25 03.4 24 26 12 16 28 05.1 24 32 49 HH 714 ...... 16 24 02.2 24 35 17 16 27 04.0 24 41 58

TABLE 7 Candidate HH Objects in the Observed Ophiuchi Cloud Core

Object B1950.0 B1950.0 J2000.0 J2000.0

O1a...... 16 23 16.3 24 20 51 16 26 17.8 24 27 35 O1b...... 16 23 21.5 24 22 15 16 26 23.0 24 28 59 O2...... 16 23 16.8 24 34 15 16 26 18.5 24 41 00 O3...... 16 23 37.1 24 11 52 16 26 38.3 24 18 36 O4...... 16 24 54.4 24 19 59 16 27 55.9 24 26 37 O5...... 16 25 58.3 24 27 34 16 29 00.0 24 34 08 P1 ...... 16 24 13.1 24 31 24 16 27 14.8 24 38 04 P2: ...... 16 24 23.9 24 19 32 16 27 25.4 24 26 12 P3 ...... 16 23 54.7 24 58 40 16 26 55.7 24 05 22 P4: ...... 16 24 32.9 24 32 11 16 27 34.7 24 38 51 P5: ...... 16 24 39.6 24 31 52 16 27 41.4 24 38 31 HERBIG-HARO FLOWS IN OPH 443

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