Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 5472 Report Date: 18-Jul-95:17:28 Version: ********** Check-in Date: ********** 1.Proposal Title: THE COLLIMATION AND PROPAGATION OF JETS FROM YOUNG STARS ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID INTERSTELLAR MEDIUM GO Sub Category HH OBJECTS ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Thomas P Ray DUBLIN INSTITUTE FOR ADVANCE IRELAND +353 1 6621333 ------------------------------------------------------------------------------------ 7. Abstract It is over ten years since the discovery of young stellar object (YSO) jets. Although clearly there is an association between these jets and YSO disks, their collimation mechanism is poorly understood. Moreover while radiative shocks are known to be the source of their emission, the origin of these shocks is uncertain. To address these problems, we propose to study the outflows in the vicinity of HL Tau, particularly the jets associated with HL Tau itself. With these images it should be possible to test, for the first time, two rival scenarios for the origin of the jet emission (oblique shocks versus internal working surfaces). We have found that jet opening angles visibly decrease with distance from their source. This argues strongly for models in which external pressure gradients (over scales less than several hundred AU) confine the jet. We wish now to examine the importance of such gradients even closer to the source (i.e. within a few arcseconds) to see whether they are the primary focussing mechanism. Our HST observations will obtain as a byproduct unprecedented information on the circumstellar environs of HL Tau, a YSO which is thought to possess a protoplanetary disk. The study will be carried out using the \[SII\]6717,6731, H ALPHA, \[OI\]6300 and F547M filters. This proposal was initially accepted for Cycle 1 but not retained after reassessment. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 3.50 par: 0 10. Num targs pri: 1 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: WF/PC ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 5472 PI: Thomas P Ray Proposal Title: THE COLLIMATION AND PROPAGATION OF JETS FROM YOUNG STARS ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Tom P Ray DUBLIN INST. FOR ADVANCED IRELAND X STUDIES John Dyson 8046 UNITED KING X Davina Innes 5540 GERMANY X Sam Falle 8038 UNITED KING X Reinhard Mundt 5541 GERMANY X Alex Raga UNIV. OF MANCHESTER INST. FOR UNITED KING X SC. AND TECH. ------------------------------------------------------------------------------------ 3. Description of proposed observations. The knotty YSO jet associated with HL Tau will be observed with the WFPC2 using a [SII]6716/6731 filter (F673N) and the H alpha filter (F656N). Note that the jet from HL Tau is of quite low excitation and hence bright in [SII]. HL Tau should be observed for 60min (2x30min) with F673 and for a similar time with F656N to achieve sufficient signal to noise. These images will be used to determine the nature of the knots within the jet. By comparing the H alpha and [SII] images we hope to see evidence for differential cooling in the jet for the first time. In order to examine the collimation process close to the star we will image this region using the [OI]6300 (F631N) filter. Since the surface brightness of the jet is higher closer to the source a 30 min exposure (2X15mins) is sufficient in this case. In order to remove the contribution of the bright nebula around HL Tau, a continuum exposure is also necessary. Optimally this is done by choosing a continuum filter close to, in wavelength, but excluding the emission line under investigation. Thus our corresponding continuum exposure (2x7.5mins) will be through the F547M filter completing our observations of the HL Tau region. We would emphasize that the observations close to the star are being carried out using an [OI] filter rather than a [SII] filter because of the high electron densities expected near the source (>10e5cm-3). Since [OI] has a 500 times higher critical density than [SII]6731, it is therefore the most suitable low excitation line. A H alpha filter is inappropriate in this case because of the very bright H alpha emission from the source. Finally we add that at the same time we will be studying HL Tau, our FOV also includes several other optical outflows including XZ Tau and part of HH30. This region is thus particularly suited as a target. ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. While jets themselves have lengths of half an arc minute or longer, their diameters close to the source (i.e. within a few arcseconds) are less than or equal to 1 arcsecond . Moreover the structures we wish to observe (the internal working surfaces/oblique shocks) are on comparable or even smaller scales. Deconvolution techniques help but typically only give a factor of two or so improvement in resolution. Because of the faintness and extended size of YSO jets, speckle interferometry is of little use.The targetted objects has been observed by us under very good seeing conditions (approximately 0.8 arcseconds) and we have managed to obtain a resolution of about half this using image reconstruction techniques. It is unlikely that much improved ground based observations of the HL Tau outflow, and those associated with nearby YSOs, can be done in the foreseeable future. ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. Page 3 ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. ------------------------------------------------------------------------------------ 8. Additional comments or special requests. As mentioned in the abstract, this is a reincarnation of a previously approved Cycle 1 proposal that was not retained after reassessment. HH30, our original target is still partially studied in the existing program but we now include HL Tau and XZ Tau as these are adjacent and no longer on the GTO target list. ------------------------------------------------------------------------------------ 9. Description of previous HST work. ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). Data analysis facilities (MIDAS and IRAF) are available at DIAS, the Max Planck Institute for Astronomy in Heidelberg and the University of Manchester. We have also installed STSDAS at DIAS. ------------------------------------------------------------------------------------ 11. Address Information Name: Thomas P Ray Category: PI Institution: Dublin Institute for Advanced Stu Address: School of Cosmic Physics Dublin Institute for Advanced Studies 5 Merrion Square City: Dublin State: Zip Code: 2 Country: Ireland Telephone: +353 1 6621333 Telex (or e-mail): tr@cp.dias.ie (Intet) ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 5472 [ 4] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial |Acqui|FLX| Flux data No | Name | Description | Position |Eqnx | Vel. |Prblm|REF| | | | | | | | | ------------------------------------------------------------------------------------------------------------------------------------ 1 HLTAU A,156,907,G,501,514 RA = 04H 31M 38.47S +/- 2000 1 V=14.6 0.2S, 2 B=16.0 DEC = +18D 13' 50" +/- 2.0" 3 B-V=1.4 4 SURF-LINE(6563) = 2.5 +/- 1 E-15 5 W-LINE(6563)=1.0 +/- 0.5 6 SURF-LINE(6717) = 2.5 +/- 1 E-15 7 W-LINE(6717)=1.0 +/- 0.5 8 SURF-LINE(6300) = 3.5 +/- 1 E-15 9 W-LINE(6300)=1.0 +/- 0.5 Comments: HL TAU WILL BE CENTRED ON PC1. XZ TAU 10 SURF-CONT(5470)= 1 +/-0.5 E-15 WHICH LIES TO ITS EAST WILL ALSO BE VISIBLE. FLUXVAL_10 BASED ON NEBULA. ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5472 [ 5] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HLTAU WFPC2 IMAGE PC1 F656N 6563.0 CR-SPLIT=NO 2 1800S 20 4 2 CYCLE 4 5 SAME POS FOR 2.0- 4.0 AS 1.0 GROUP 1.0-4.0 NO GAP ORIENT 75D +/-5D ------------------------------------------------------------------------------------------------------------------------------------ 2 HLTAU WFPC2 IMAGE PC1 F673N 6732.0 CR-SPLIT=NO 3 900S 20 6 1 CYCLE 4 7 ------------------------------------------------------------------------------------------------------------------------------------ 3 HLTAU WFPC2 IMAGE PC1 F631N 6283.0 CR-SPLIT=NO 2 900S 20 8 1 CYCLE 4 9 10 ------------------------------------------------------------------------------------------------------------------------------------ 4 HLTAU WFPC2 IMAGE PC1 F547M 5479.0 CR-SPLIT=NO 2 500S 20 10 1 CYCLE 4 ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 5472 [ 6] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 3.50 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category INTERSTELLAR MEDIUM ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category HH OBJECTS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CYCLE 4; SAME POS FOR 2.0-4.0 AS 1.0; GROUP 1.0-4.0 NO GAP; ORIENT 75D +/-5D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F656N F673N F631N F547M ------------------------------------------------------------------------------------------------------------------------------------ Target Names HLTAU ------------------------------------------------------------------------------------------------------------------------------------