9460( 2) - 02/14/02 12:12 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9460 Version: 2 Check-in Date: 14-Feb-2002 12:11:38 1.Proposal Title: Irradiated Jets and Proto-Planetary Disks in the Outer Orion Nebula ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 11 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: John Bally University of Colorado at Boulder CoI: Dr. Bo Reipurth University of Colorado N CoI: Dr. Mark McCaughrean Astrophysikalisches Institut Potsdam N ------------------------------------------------------------------------------------ 5. Abstract We propose to acquire high resolution ACS H-alpha , [N II] , and [O III] images in four outlying portions of the Orion Nebula that will sample the type of environment in which most members of the Trapezium cluster stars are located. We seek to understand the properties of outflows and protoplanetary disks `proplyds' located more than 4'\ (0.5 pc) from the core of the Orion Nebula as a function of the radiation field intensity. Two of our target fields contain recently identified externally irradiated jets that suffer large C-shaped bends. The Orion jets are ionized by external UV radiation. Thus, the structures of the target flows can be directly determined from images without recourse to non-linear shock models. High resolution images of their shocks will be used to distinguish between several possible models of jet deflection and to directly compare with 3D numerical models of jets in side- winds. Two other fields contain large proplyd candidates and large numbers of young stars formed from the Orion molecular ridge. These young stars are in less irradiated environments than the well studied proplyds in the nebular core. We will search for new proplyds surrounding these stars to see if the lower radiation field implies a better chance of disk survival. These observations will serve to constrain the properties of protoplanetary disks in lower radiation environments than those in the nebular core. ------------------------------------------------------------------------------------ 9460( 2) - 02/14/02 12:12 - [ 2] Observations Description ------------------------ In this program, we will use ACS/WFC to obtain deep full orbit images (CR- SPLIT) of the target sources in four filters; three narrow-band filters that cover the O Iii , H- alpha , and N Ii line, and one medium band filter that will be used to measure the continuum. Previous HST observations with WFPC2 have indicated that circumstellar disks are most easily detected in the O Iii line which is nearly as bright as H-alpha\ in the inner Orion Nebula. Since the proplyds ionization fronts tend to be relatively faint in this line, disks tend to be seen as dark silhouette objects seen agains the bright O Iii background. The proplyd ionization fronts, on the other hand, tend to be brightest in the H -alpha\ line. The intensity of this line can be directly converted into the emission measure, which with an estimate of the depth of the emitting plasma (estimated from the source structure), can be directly converted into an electron density. Thus, we will use images obtained with the N Ii filter to remove the contribution of this line to the flux measured with the F658N filter that transmits both H-alpha\ and N Ii emission. The F550M filter will be used to measure the continuum light in the nebula produced by scattering by dust grains and to subtract this (and stellar) continua from the narrow-band images. For each narrow-band filter, we need a total exposure time of about 500 to 1, 000 seconds per pointing per each filter. This estimate comes from our previous WFPC2 observations of objects up to 4'\ from the Trapezium stars. We have used our 4 meter KPNO images to scale the H-alpha surface brightness of the nebula from this region to the four target fields. The O Iii line is about a factor of two fainter than H-alpha\ in the outer nebula, and will require a correspondingly longer exposure. N Ii emission is typically three times fainter than H-alpha . This experience suggest that we need to split one orbit between H-alpha\ and O Iii , and another orbit between a long N Ii exposure and a short set of continuum exposures. Thus, each field requires two orbits and 8 orbits are needed to observe the four fields. Ground-based data indicates that the H- alpha\ emission from HH 502 and HH 505 reach surface brightness levels of I( H- alpha ) = 2 * 10^-14 erg^-1 s^-1 arcsec^-2 and that the background nebular emission can reach levels of I( H-alpha ) = 11 * 10^-14 erg^-1 s^-1 arcsec^-2. The fainter jet components are about a factor of 10 to 20 times fainter than the brightest jet parts. The exposure time calculator (ETC) indicates that to reach this fainter emission, and to get the high S/N data on the brighter knots required for comparison with our numerical models, at least half-orbit integrations (CR-SPLIT) in the narrow-band filters are needed. One prior WFPC2 H-alpha\ image (GO 8324) that contains knot N3 in HH 502 in a corner of WFPC2 confirms these estimates. Below, we discuss observations of each field. HH 502 -- Field 1: This is our highest radiation environment. Located several arc minutes south of Orion's bar, the HH 502 pointing covers the field containing the Herbig-Haro objects HH 502 and HH 400 (Bally & Reipurth 2001; Bally et al. 2001). This entire flow will fit nicely into the ACS aperture. Additionally, a dozen young stars, and several shocks unrelated to the HH 502 flow will be imaged. During the GO 6603 campaign on the Orion Nebula, a WFPC2 parallel observation in the H-alpha\ filter (STIS was prime) caught the northern edge of the HH 502 flow in a 180 second exposure. The tip of the bow shock N3 was recorded with a signal to noise ratio of about 5:1. This demonstrates that a half-orbit integration (CR-SPLIT) in each of the narrow-band filters are sufficient to record high quality images of this outflow system. The ground based spectra (Bally & Reipurth 2000) show that in HH 502, the Lambda6583Angstrom\ N Ii line is very bright near the tips of the major bow shocks and near the base of the jet. Therefore, for this source a deep nearly full orbit image in N Ii will be an excellent tracer of the small-scale structure of the bow shocks shown in Figure 1. When combined with our ground- based spectra, this image will help constrain the density and excitation conditions in the neutral core of the jet prior to it becoming completely ionized. We will also obtain short exposures with the ACS/WFC F550M filter which does not transmit any bright nebular lines. These images will be obtained during either the beginning or the end of each orbit where they can be used to pad the ACS exposure times to make full use of the available on-source time without affecting the much longer narrow-band exposures. This data will be used to measure the continuum light due to dust scattering in the nebula and to measure the stellar fluxes. HH 505 -- Field 2: HH 505 is a remarkable one sided jet enveloped in a bow shaped cocoon that has been modeled in detail by Masciadri & Raga (2001 -- see Figure 2) as a jet in a side-wind. The ACS pointing will completely cover the object, along with another wind bubble, a dozen young stars, and some interesting shock structures within the Orion Nebula. This field is located about twice as far from the Trapezium as Field 1. M 43 West -- Field 3: This is a soft- UV dominated environment lit up by the O9.5 star NU Ori that excited the small HII region M43. Our ground based images show a giant proplyd near the western rim of M43, along with more than a dozen low mass stars. Previous pointings with HST towards the eastern portion of M 43 (obtained as coordinated parallel observations during Bally's and O'Dell's programs) reveal the presence of many young stars and some large proplyds (O'Dell 2001; Bally & Reipurth 2001). M 42 North -- Field 4: This pointing lies along the northern rim of the M 42 HII region and represents the lowest radiation field environment in our study. This field lies towards the Orion Molecular Ridge and our ground-based data shows dozens of young stars within the ACS aperture. These four fields together probe the full radiation environment encountered in the Orion Nebula region. These observations will give a good indication of the proplyd and protostellar jet discovery rate that a comlete survey of the Orion Nebula would likely yield, thereby evaluating the feasibility of such a wide- field survey in the future. But more importantly, these four pointings will provide a statistically valid sample of young stars located in more weakly irradiated environments than the core of the Nebula, the only region that has been studied so far with 0.1"\ or better resolution. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9460( 2) - 02/14/02 12:12 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 ORION-HH502 ISM, HII REGION, STAR, RA=05H 35M 27.13S +/- 0.05S, 2000 V = 17 T TAURI STAR DEC=-5D 29' 56.0" +/- 0.5" F-LINE(6563)=2+/-1e-14 Coordinate Source: OTHER_SOURCE Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.0 0.0 0.0 2 ORION-HH505 ISM, HII REGION, STAR, RA=05H 34M 39.23S +/- 0.05S, 2000 V = +17 T TAURI STAR DEC=-5D 23' 12.0" +/- 0.5" F-LINE(6563)=2+/-1e-14 Coordinate Source: OTHER_SOURCE Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.0 0.0 0.0 3 ORION-M43 ISM, HII REGION, STAR, RA=05H 35M 22.64S +/- 0.05S, 2000 V = 17 T TAURI STAR DEC=-5D 16' 09.0" +/- 0.5" F-LINE(6563)=2+/-1e-14 Coordinate Source: OTHER_SOURCE Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.0 0.0 0.0 4 ORION-M42N ISM, HII REGION, STAR, RA=05H 35M 20.51S +/- 0.05S, 2000 V = 17 T TAURI STAR DEC=-5D 11' 16.6" +/- 0.5" F-LINE(6563)=3+/-1e-15 Coordinate Source: OTHER_SOURCE Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.0 0.0 0.0 9460( 2) - 02/14/02 12:12 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type ACS-WFC-DITHER-LINE Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 3.011 Coordinate_Frame POS-TARG Pattern_Orient 85.28 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 9460( 2) - 02/14/02 12:12 - [ 5] Visit: 01 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 ORION-HH502 ACS/WF ACCUM WFC F658N CR-SPLIT=NO 1 500 S PATTERN 1 C ------------------------------------------------------------------------------------------------------------------------------------ 2 ORION-HH502 ACS/WF ACCUM WFC F660N CR-SPLIT=NO 1 500 S PATTERN 1 C ------------------------------------------------------------------------------------------------------------------------------------ 3 ORION-HH502 ACS/WF ACCUM WFC F550M CR-SPLIT=NO 1 30 S C ------------------------------------------------------------------------------------------------------------------------------------ 4 ORION-HH502 ACS/WF ACCUM WFC F502N CR-SPLIT=NO 2 500 S PATTERN 1 C ------------------------------------------------------------------------------------------------------------------------------------ 9460( 2) - 02/14/02 12:12 - [ 6] Visit: 02 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 5 ORION-HH505 ACS/WF ACCUM WFC F658N CR-SPLIT=NO 1 500 S PATTERN 1 C ------------------------------------------------------------------------------------------------------------------------------------ 6 ORION-HH505 ACS/WF ACCUM WFC F660N CR-SPLIT=NO 1 500 S PATTERN 1 C ------------------------------------------------------------------------------------------------------------------------------------ 7 ORION-HH505 ACS/WF ACCUM WFC F550M CR-SPLIT=NO 1 30 S C ------------------------------------------------------------------------------------------------------------------------------------ 8 ORION-HH505 ACS/WF ACCUM WFC F502N CR-SPLIT=NO 2 500 S PATTERN 1 C ------------------------------------------------------------------------------------------------------------------------------------ 9460( 2) - 02/14/02 12:12 - [ 7] Visit: 03 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 9 ORION-M43 ACS/WF ACCUM WFC F658N CR-SPLIT=NO 1 500 S PATTERN 1 C ------------------------------------------------------------------------------------------------------------------------------------ 10 ORION-M43 ACS/WF ACCUM WFC F660N CR-SPLIT=NO 1 500 S PATTERN 1 C ------------------------------------------------------------------------------------------------------------------------------------ 11 ORION-M43 ACS/WF ACCUM WFC F550M CR-SPLIT=NO 1 30 S C ------------------------------------------------------------------------------------------------------------------------------------ 12 ORION-M43 ACS/WF ACCUM WFC F502N CR-SPLIT=NO 2 500 S PATTERN 1 C ------------------------------------------------------------------------------------------------------------------------------------ 9460( 2) - 02/14/02 12:12 - [ 8] Visit: 04 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 13 ORION-M42N ACS/WF ACCUM WFC F658N CR-SPLIT=NO 2 500 S PATTERN 1 C ------------------------------------------------------------------------------------------------------------------------------------ 14 ORION-M42N ACS/WF ACCUM WFC F550M CR-SPLIT=NO 1 30 S C ------------------------------------------------------------------------------------------------------------------------------------ 15 ORION-M42N ACS/WF ACCUM WFC F660N CR-SPLIT=NO 2 500 S PATTERN 1 C ------------------------------------------------------------------------------------------------------------------------------------ 9460( 2) - 02/14/02 12:12 - [ 9] Summary Form for Proposal 9460 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WFC ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 1 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F658N F660N F550M F502N ------------------------------------------------------------------------------------------------------------------------------------ Target Names ORION-HH502 ORION-HH505 ORION-M43 ORION-M42N ------------------------------------------------------------------------------------------------------------------------------------