8653( 8) - 08/07/01 10:04 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8653 Version: 8 Check-in Date: 07-Aug-2001 10:03:08 1.Proposal Title: Collimation and Physical Conditions Within the HH 30 Protostellar Jet ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 9 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Patrick Hartigan Rice University CoI: Dr. Jon Morse University of Colorado N ------------------------------------------------------------------------------------ 5. Abstract We propose to observe the protostellar jet HH 30 through a wide slit with STIS in order to determine the distance from the star that the jet becomes collimated, and to diagnose the density, temperature, shock structure, and ionization within the collimation region. The proposed observations will provide an image of the jet in each emission line across the entire optical spectrum with minimal contamination from the reflection nebula near the star, a marked improvement over existing narrowband images that cover only a few lines which emit over a limited range of densities and ionization states. Ratios of the new emission-line images will probe the physical conditions in the jet with HST spatial resolution and make it possible to observe the shape and location of any shocks in the flow, resolve the cooling layers behind these shocks, and trace the recombination of any ionized gas that emerges from the base of the jet. The proximity and brightness of HH 30 together with its favorable inclination angle make this an ideal object to study jet collimation. The new STIS spectra are precisely what are needed to test MHD models of jet collimation from accretion disks. Understanding how jets originate, become collimated, and form shocks has profound implications for the distribution of magnetic fields and angular momentum within accretion disks, which in turn control how stars and planets form. ------------------------------------------------------------------------------------ 8653( 8) - 08/07/01 10:04 - [ 2] Observations Description ------------------------ Procedure: As long as the grating dispersion is chosen so that different emission lines do not overlap spatially and the internal motions within the jet are unresolved spectrally, a spectrum through a wide slit gives an image of the jet at each emission line radiated in the flow (Fig. 2). With these data one can easily subtract any scattered light from the disk to leave only the image of the jet. Effectively the process gives the equivalent of a narrowband image at each wavelength with a bandpass equal to the spectral resolution. Our program requires the use of 4 separate spectral configurations. Observations with the low- resolution gratings are suitable provided that bright emission lines are not too close to one another in wavelength so that the images of the jet begin to overlap. The WFPC2 images of HH 30 show the jet to have a width of about 0.5^ , or about 10 STIS pixels, which corresponds to 49Angstrom\ for G750L and 27Angstrom\ for G430L. In the red, this dispersion is fine for the bright lines of O I Lambda6300, O ILambda5577, C I Lambda9850, and even NaD, but the G750L will merge the HAlpha and N II Lambda6583 images, and the S II Lambda6716 and S II Lambda6731 images. For this reason we also require spectra using G750M at Lambda_c = 6768Angstrom , which will separate these important diagnostic lines. The G750M grating has a dispersion of 25 kms\ per pixel, which for many jets would resolve the internal velocity structure within the flow. However, because the HH 30 flow is nearly in the plane of the sky and has no prominent bow shocks, the radial velocities are constant to within 10 kms\ along the inner part of the jet and the internal emission line widths are <=sssim 20 kms\ over this region^15. Hence, HH 30 is one of the few stellar jets for which wide slit observations with the G750M grating can be interpreted unambiguously. As a check to make certain that no large emission line widths have developed near the star recently, we also request one setting with a narrow slit that will detect any such features. In the blue, the low resolution of the G430L grating actually helps with images of close doublet lines such as N I 5199/5200 and O II 3727/3729. The lines are bright in low-excitation HH objects like HH 30, and each component of the doublet would be imaged onto a single spatial pixel at a dispersion of 2.7Angstrom\ per pixel. In this case, higher dispersion would ruin the observations by splitting the doublet into an overlapping image of each line. Other important blue lines include HBeta, HGamma and O III Lambda5007. These lines are sufficiently separated from other emission lines to give clear images. Together, these spectra suffice to image all emission lines of interest over the entire spectrum between 3000Angstrom\ and 1Mum, including at least three lines in the Balmer series, three ionization states of O, density tracers like the red S II lines, ionization tracers like N II/HAlpha, and high critical density transitions such as O I Lambda5577. Why HH 30? The need to resolve the jet closest to the star restricts this project to objects in the nearest dark clouds (e.g. Taurus, Lupus, Cha I, R CrA, each three times closer than Orion). For the wide-slit spectroscopy to work, the jet must not contain any bow shocks close to the source that have large velocity dispersions. Also, the jet should be nearly in the plane of the sky to minimize projection effects and radial velocity variability in the jet. Ideally, the star would be obscured somewhat by the disk so that it does not saturate the CCD, but the disk must allow the jet to be traced right up to the star. The jet should be relatively bright and well-defined. HH 30 satisfies all of the above criteria except that it can currently be traced to only 0.25" from the star with existing images(Fig 1). This limit should be improved with the better continuum subtraction, longer exposure times, and more emission lines covered by the new observations. Exposure Times: The HH 30 jet has a typical low- excitation spectrum like that observed in other jets and many HH objects. The exposure times below are based on fluxes observed with ground-based spatial resolution^15, previous HST images, shock models^13, and spectra of other low- excitation HH objects. Archival images of HH 30 in S II Lambda6731 and HAlpha show that the jet has a flux of about 1* 10^-15 -- 1* 10^-16 erg, cm^-2s^-1 in these lines close to the star. To image the important lines such as O I Lambda5577 in HH 30 requires a limit of ~ 10^-17 erg, cm^-2s^-1. The STIS exposure time calculator gives an exposure time of 3.0* 10^4 seconds to achieve a S/N = 5 for this line. This time amounts to 12 orbits, taking into account target visibility and overhead. These images will go some ten times deeper than the archival image in Fig. 1, which had an exposure time of 2700 seconds. The G750M setting is the most useful for measuring jet collimation, because it is here that the brightest lines of HAlpha, S II Lambda6716 and S II Lambda6731 are imaged. Because extinction in the red is lower than in the blue, it should be possible to trace the jet closest to the star with this setting. We are aiming for the same order of magnitude level of improvement over existing images as with the G750L setting, which amounts to about 10 orbits. Quantitatively, for the G750M images to achieve the same limit of 10^-17 erg, cm^-2s^-1 and S/N = 12 we need 2.4* 10^4 seconds, or 9 orbits. This limit is also set by the need to image the crucial N II Lambda6583 line throughout the jet. The 52x0.2 observations will search for any broad line profiles near HH 30 that have escaped detection from the ground. For this setting, a S/N = 3 for detection of a high velocity component at a level of 1\ flux (10^-17 erg, cm^- 2s^- 1) satisfies the intent of the observations, and amounts to one orbit. In the blue, a sensitivity level of 10^-17 erg, cm^-2s^-1 is required to image lines like O II Lambda3727. For the 430L-grating and a S/N = 5 this amounts to 2.2* 10^4 seconds, or 8 orbits. We plan to do fractional pixel dithering in order to maximize the spatial resolution. Real Time Justification ----------------------- none. none Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 8653( 8) - 08/07/01 10:04 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HH30 ISM, HERBIG-HARO RA=04H 31M 37.522S +/- 0.2", J2000 F-LINE(6563)=5+/-2e-16 OBJECT, JET, SHOCK DEC=18D 12' 24.67" +/- 0.2", FRONT, STAR FORMING PLATE-ID=000P REGION, EMISSION LINE Coordinate Source: HST_IMAGE Comments: none 8653( 8) - 08/07/01 10:04 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type STIS-CCD-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.0567 Coordinate_Frame POS-TARG Pattern_Orient 26.56 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 8653( 8) - 08/07/01 10:04 - [ 5] Visit: 01 Visit Priority: Visit Requirements: ORIENT 29D TO 33D ORIENT 254D TO 258D 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 ------------------------------------------------------------------------------------------------------------------------------------ 110 HH30 STIS/C ACQ F28X50L MIRROR ACQTYPE=DIFFUSE,CHECKBOX=21, 1 10 S CD P DIFFUSE-CENTER=FLUX-CENTROID ------------------------------------------------------------------------------------------------------------------------------------ 111 HH30 STIS/C ACCUM 52X2 G750L 7751 CR-SPLIT=2 1 39 M PATTERN 1 111 CD ------------------------------------------------------------------------------------------------------------------------------------ 113 CCDFLAT STIS/C ACCUM 52X0.1 G750L 7751 2 DEF CD Comments: Fringe Flat ------------------------------------------------------------------------------------------------------------------------------------ 8653( 8) - 08/07/01 10:04 - [ 6] Visit: 02 Visit Priority: Visit Requirements: ORIENT 29D TO 33D ORIENT 254D TO 258D 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 ------------------------------------------------------------------------------------------------------------------------------------ 210 HH30 STIS/C ACQ F28X50L MIRROR ACQTYPE=DIFFUSE,CHECKBOX=21, 1 10 S CD P DIFFUSE-CENTER=FLUX-CENTROID ------------------------------------------------------------------------------------------------------------------------------------ 211 HH30 STIS/C ACCUM 52X2 G750M 6581 CR-SPLIT=2 1 39 M PATTERN 1 211 CD ------------------------------------------------------------------------------------------------------------------------------------ 8653( 8) - 08/07/01 10:04 - [ 7] Visit: 03 Visit Priority: Visit Requirements: ORIENT 29D TO 33D ORIENT 254D TO 258D 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 ------------------------------------------------------------------------------------------------------------------------------------ 310 HH30 STIS/C ACQ F28X50L MIRROR ACQTYPE=DIFFUSE,CHECKBOX=21, 1 10 S CD P DIFFUSE-CENTER=FLUX-CENTROID ------------------------------------------------------------------------------------------------------------------------------------ 311 HH30 STIS/C ACCUM 52X2 G750M 6581 CR-SPLIT=2 1 39 M PATTERN 1 311 CD ------------------------------------------------------------------------------------------------------------------------------------ 8653( 8) - 08/07/01 10:04 - [ 8] Visit: 04 Visit Priority: Visit Requirements: ORIENT 29D TO 33D ORIENT 254D TO 258D 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 ------------------------------------------------------------------------------------------------------------------------------------ 410 HH30 STIS/C ACQ F28X50L MIRROR ACQTYPE=DIFFUSE,CHECKBOX=21, 1 10 S CD P DIFFUSE-CENTER=FLUX-CENTROID ------------------------------------------------------------------------------------------------------------------------------------ 411 HH30 STIS/C ACCUM 52X2 G430L 4300 CR-SPLIT=2 1 39 M PATTERN 1 411 CD ------------------------------------------------------------------------------------------------------------------------------------ 8653( 8) - 08/07/01 10:04 - [ 9] Visit: 05 Visit Priority: Visit Requirements: ORIENT 29D TO 33D ORIENT 254D TO 258D 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 ------------------------------------------------------------------------------------------------------------------------------------ 510 HH30 STIS/C ACQ F28X50L MIRROR ACQTYPE=DIFFUSE,CHECKBOX=21, 1 10 S CD P DIFFUSE-CENTER=FLUX-CENTROID ------------------------------------------------------------------------------------------------------------------------------------ 511 HH30 STIS/C ACCUM 52X0.2 G750M 6581 CR-SPLIT=2 1 37 M CD ------------------------------------------------------------------------------------------------------------------------------------ 512 HH30 STIS/C ACCUM 52X2 G430L 4300 CR-SPLIT=2 1 43 M CD ------------------------------------------------------------------------------------------------------------------------------------ 8653( 8) - 08/07/01 10:04 - [ 10] Visit: 11 Visit Priority: Visit Requirements: ORIENT 29D TO 33D ORIENT 254D TO 258D 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 ------------------------------------------------------------------------------------------------------------------------------------ 110 HH30 STIS/C ACQ F28X50L MIRROR ACQTYPE=DIFFUSE,CHECKBOX=21, 1 10 S CD P DIFFUSE-CENTER=FLUX-CENTROID ------------------------------------------------------------------------------------------------------------------------------------ 111 HH30 STIS/C ACCUM 52X2 G750M 6581 CR-SPLIT=2 1 39 M PATTERN 1 111 CD ------------------------------------------------------------------------------------------------------------------------------------ 8653( 8) - 08/07/01 10:04 - [ 11] Visit: 12 Visit Priority: Visit Requirements: ORIENT 29D TO 33D ORIENT 254D TO 258D 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 ------------------------------------------------------------------------------------------------------------------------------------ 210 HH30 STIS/C ACQ F28X50L MIRROR ACQTYPE=DIFFUSE,CHECKBOX=21, 1 10 S CD P DIFFUSE-CENTER=FLUX-CENTROID ------------------------------------------------------------------------------------------------------------------------------------ 211 HH30 STIS/C ACCUM 52X2 G750M 6581 CR-SPLIT=2 1 39 M PATTERN 1 211 CD ------------------------------------------------------------------------------------------------------------------------------------ 8653( 8) - 08/07/01 10:04 - [ 12] Visit: 14 Visit Priority: Visit Requirements: ORIENT 29D TO 33D ORIENT 254D TO 258D 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 ------------------------------------------------------------------------------------------------------------------------------------ 410 HH30 STIS/C ACQ F28X50L MIRROR ACQTYPE=DIFFUSE,CHECKBOX=21, 1 10 S CD P DIFFUSE-CENTER=FLUX-CENTROID ------------------------------------------------------------------------------------------------------------------------------------ 412 HH30 STIS/C ACCUM 52X2 G430L 4300 CR-SPLIT=2 1 39 M PATTERN 1 412 CD ------------------------------------------------------------------------------------------------------------------------------------ 8653( 8) - 08/07/01 10:04 - [ 13] Summary Form for Proposal 8653 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 52X2 52X0.1 52X0.2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=DIFFUSE CHECKBOX=21 DIFFUSE-CENTER=FLUX-CENTROID CR-SPLIT=2 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 29D TO 33D ORIENT 254D TO 258D PATTERN 1 111 PATTERN 1 211 PATTERN 1 311 PATTERN 1 411 PATTERN 1 412 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G750L G750M G430L ------------------------------------------------------------------------------------------------------------------------------------ Target Names HH30 CCDFLAT ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 7751 6581 4300 ------------------------------------------------------------------------------------------------------------------------------------