! $Id: 5472,v 9.1 1994/07/27 18:23:23 pepsa Exp $ coverpage: title_1: THE COLLIMATION AND PROPAGATION OF JETS FROM YOUNG STARS sci_cat: INTERSTELLAR MEDIUM sci_subcat: HH OBJECTS proposal_for: GO pi_fname: THOMAS pi_mi: P pi_lname: RAY pi_inst: DUBLIN INSTITUTE FOR ADVANCED STUDIES pi_country: IRELAND pi_phone: +353 1 6621333 hours_pri: 3.50 num_pri: 1 wf_pc: Y off_fname: LUKE off_lname: DRURY off_title: PROFESSOR off_addr_1: SCHOOL OF COSMIC PHYSICS off_addr_2: DUBLIN INSTITUTE FOR ADVANCED STUDIES off_addr_3: 5 MERRION SQUARE off_city: DUBLIN off_zip: 2 off_country: IRELAND off_phone: +353 1 6621333 ! end of coverpage abstract: line_1: It is over ten years since the discovery of young stellar object (YSO) line_2: jets. Although clearly there is an association between these jets and line_3: YSO disks, their collimation mechanism is poorly understood. Moreover line_4: while radiative shocks are known to be the source of their emission, the line_5: origin of these shocks is uncertain. To address these problems, we propose to line_6: study the outflows in the vicinity of HL Tau, particularly the jets line_7: associated with HL Tau itself. With these images it should be possible line_8: to test, for the first time, two rival scenarios for the origin of the line_9: jet emission (oblique shocks versus internal working surfaces). We have line_10: found that jet opening angles visibly decrease with distance from line_11: their source. This argues strongly for models in which external pressure line_12: gradients (over scales less than several hundred AU) confine the jet. line_13: We wish now to examine the importance of such gradients even closer to line_14: the source (i.e. within a few arcseconds) to see whether they are the line_15: primary focussing mechanism. Our HST observations will obtain as a byproduct line_16: unprecedented information on the circumstellar environs of HL Tau, a YSO line_17: which is thought to possess a protoplanetary disk. The study will be line_18: carried out using the \[SII\]6717,6731, H ALPHA, \[OI\]6300 and F547M line_19: filters. This proposal was initially accepted for Cycle 1 but not retained after line_20: reassessment. ! ! end of abstract general_form_proposers: lname: RAY fname: TOM mi: P inst: DUBLIN INST. FOR ADVANCED STUDIES country: IRELAND esa: Y ! lname: DYSON fname: JOHN inst: 8046 country: UNITED KINGDOM esa: Y ! lname: INNES fname: DAVINA inst: 5540 country: GERMANY esa: Y ! lname: FALLE fname: SAM inst: 8038 country: UNITED KINGDOM esa: Y ! lname: MUNDT fname: REINHARD inst: 5541 country: GERMANY esa: Y ! lname: RAGA fname: ALEX inst: UNIV. OF MANCHESTER INST. FOR SC. AND TECH. country: UNITED KINGDOM esa: Y ! ! end of general_form_proposers block general_form_text: question: 3 section: 1 line_1: The knotty YSO jet associated with HL Tau will be observed with the WFPC2 using line_2: a [SII]6716/6731 filter (F673N) and the H alpha filter (F656N). Note that the line_3: jet from HL Tau is of quite low excitation and hence bright in [SII]. HL Tau line_4: should be observed for 60min (2x30min) with F673 and for a similar time line_5: with F656N to achieve sufficient signal to noise. These images will be used to line_6: determine the nature of the knots within the jet. By comparing the H alpha and line_7: [SII] images we hope to see evidence for differential cooling in the jet for line_8: the first time. In order to examine the collimation process close line_9: to the star we will image this region using the [OI]6300 (F631N) line_10: filter. Since the surface brightness of the jet is higher closer to the source line_11: a 30 min exposure (2X15mins) is sufficient in this case. line_12: In order to remove the contribution of the bright nebula around HL Tau, line_13: a continuum exposure is also necessary. Optimally this is done by choosing a line_14: continuum filter close to, in wavelength, but excluding the emission line under line_15: investigation. Thus our corresponding continuum exposure (2x7.5mins) will line_16: be through the F547M filter completing our observations of the HL Tau region. line_17: We would emphasize that the observations close to the star line_18: are being carried out using an [OI] filter rather than a [SII] filter because line_19: of the high electron densities expected near the source (>10e5cm-3). Since [OI] line_20: has a 500 times higher critical density than [SII]6731, it is therefore the most line_21: suitable low excitation line. A H alpha filter is inappropriate in this case line_22: because of the very bright H alpha emission from the source. Finally we add that line_23: at the same time we will be studying HL Tau, our FOV also includes several other ! question: 3 section: 2 line_1: optical outflows including XZ Tau and part of HH30. This region is thus line_2: particularly suited as a target. ! question: 4 section: 1 line_1: While jets themselves have lengths of half an arc minute or longer, their line_2: diameters close to the source (i.e. within a few arcseconds) are less than or line_3: equal to 1 arcsecond . Moreover the structures we wish to observe line_4: (the internal working surfaces/oblique shocks) are on comparable or even smaller line_5: scales. Deconvolution techniques help but typically only give a factor of two or line_6: so improvement in resolution. Because of the faintness and extended size of YSO line_7: jets, speckle interferometry is of little use.The targetted objects has been line_8: observed by us under very good seeing conditions (approximately 0.8 arcseconds) line_9: and we have managed to obtain a resolution of about half this using image line_10: reconstruction techniques. It is unlikely that much improved ground based line_11: observations of the HL Tau outflow, and those associated with nearby YSOs, line_12: can be done in the foreseeable future. ! question: 5 section: 1 line_1: ! question: 6 section: 1 line_1: ! ! question: 8 section: 1 line_1: As mentioned in the abstract, this is a reincarnation of a previously line_2: approved Cycle 1 proposal that was not retained after reassessment. line_3: HH30, our original target is still partially studied in the existing line_4: program but we now include HL Tau and XZ Tau as these are line_5: adjacent and no longer on the GTO target list. ! question: 9 section: 1 line_1: ! question: 10 section: 1 line_1: Data analysis facilities (MIDAS and IRAF) are available at DIAS, the Max Planck line_2: Institute for Astronomy in Heidelberg and the University of Manchester. We have line_3: also installed STSDAS at DIAS. ! !end of general form text general_form_address: lname: Ray fname: Thomas mi: P category: PI inst: Dublin Institute for Advanced Studies addr_1: School of Cosmic Physics addr_2: Dublin Institute for Advanced Studies addr_3: 5 Merrion Square city: Dublin zip: 2 country: Ireland phone: +353 1 6621333 telex: tr@cp.dias.ie (Intet) ! ! end of general_form_address records fixed_targets: targnum: 1 name_1: HLTAU descr_1: A,156,907,G,501,514 pos_1: RA = 04H 31M 38.47S +/- 0.2S, pos_2: DEC = +18D 13' 50" +/- 2.0" equinox: 2000 comment_1: HL TAU WILL BE CENTRED ON PC1. comment_2: XZ TAU WHICH LIES TO ITS comment_3: EAST WILL ALSO BE VISIBLE. comment_4: FLUXVAL_10 BASED ON NEBULA. fluxnum_1: 1 fluxval_1: V=14.6 fluxnum_2: 2 fluxval_2: B=16.0 fluxnum_3: 3 fluxval_3: B-V=1.4 fluxnum_4: 4 fluxval_4: SURF-LINE(6563) = 2.5 +/- 1 E-15 fluxnum_5: 5 fluxval_5: W-LINE(6563)=1.0 +/- 0.5 fluxnum_6: 6 fluxval_6: SURF-LINE(6717) = 2.5 +/- 1 E-15 fluxnum_7: 7 fluxval_7: W-LINE(6717)=1.0 +/- 0.5 fluxnum_8: 8 fluxval_8: SURF-LINE(6300) = 3.5 +/- 1 E-15 fluxnum_9: 9 fluxval_9: W-LINE(6300)=1.0 +/- 0.5 fluxnum_10: 10 fluxval_10: SURF-CONT(5470)= 1 +/-0.5 E-15 ! ! end of fixed targets ! No solar system records found ! No generic target records found exposure_logsheet: linenum: 1.000 targname: HLTAU config: WFPC2 opmode: IMAGE aperture: PC1 sp_element: F656N wavelength: 6563.0 num_exp: 2 time_per_exp: 1800S s_to_n: 20 fluxnum_1: 4, fluxnum_2: 5 priority: 2 param_1: CR-SPLIT=NO req_1: CYCLE 4; req_2: SAME POS FOR 2.0-4.0 AS 1.0; req_3: GROUP 1.0-4.0 NO GAP; req_4: ORIENT 75D +/-5D ! linenum: 2.000 targname: HLTAU config: WFPC2 opmode: IMAGE aperture: PC1 sp_element: F673N wavelength: 6732.0 num_exp: 3 time_per_exp: 900S s_to_n: 20 fluxnum_1: 6, fluxnum_2: 7 priority: 1 param_1: CR-SPLIT=NO req_1: CYCLE 4; ! linenum: 3.000 targname: HLTAU config: WFPC2 opmode: IMAGE aperture: PC1 sp_element: F631N wavelength: 6283.0 num_exp: 2 time_per_exp: 900S s_to_n: 20 fluxnum_1: 8, fluxnum_2: 9 fluxnum_3: 10 priority: 1 param_1: CR-SPLIT=NO req_1: CYCLE 4; ! linenum: 4.000 targname: HLTAU config: WFPC2 opmode: IMAGE aperture: PC1 sp_element: F547M wavelength: 5479.0 num_exp: 2 time_per_exp: 500S s_to_n: 20 fluxnum_1: 10 priority: 1 param_1: CR-SPLIT=NO req_1: CYCLE 4; ! ! end of exposure logsheet ! No scan data records found