Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 5429 Report Date: 18-Jul-95:17:22 Version: ********** Check-in Date: ********** 1.Proposal Title: IMAGING POLARIMETRY OF EXTENDED UV EMISSION IN RADIO GALAXIES CYCLE 4; MEDIUM ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID QUASARS & AGN GO 1 Long Term yrs Sub Category RADIO GALAXIES ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Wil Jm Van breugel 2460 USA 510-422-7195 ------------------------------------------------------------------------------------ 7. Abstract z > 1 radio galaxies (RGs) have spatially extended, multi-component rest-frame UV continua which are aligned with their associated radio source axes. HST observations of two of the most distant RGs have shown that similar elongated and clumpy structures also exist on angular scales well below 1". Ground-based optical imaging polarimetry of a few radio galaxies has shown that the off- nuclear optical continuum light is highly (~10%) polarized, suggesting that the alignment effect is caused by scattering of anisotropic, nuclear light off thermal electrons or dust along the radio sources axes. We propose to employ the unique capabilities of HST (high res. , UV sensitivity, dark constant sky) to determine the nature of the aligned rest-frame UV continua in RGs using imaging polarimetry. We will observe 1 high-z RG (3C368) through the F555W filter using the WFPC2 in polarimetry mode in order to study the detailed structure of the clumpy off-nuclear scattering medium. This data will allow us 1) to determine the cloud parameters (sizes,distribution,covering fraction)which constrain the energetics of the nuclear source, and with ground-based imaging polarimetry at longer wavelengths, 2) to determine the nature of the scattering medium (dust or electrons). These observations will also yield high resolution, high s/n UV continuum images of the target, and should provide crucial information about the aligned UV continua in RGs to help interpret the much fainter (and harder to observe) structures seen at z>2. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 9.78 par: 0 10. Num targs pri: 1 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: WF/PC ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 5429 PI: Wil Jm Van breugel Proposal Title: IMAGING POLARIMETRY OF EXTENDED UV EMISSION IN RADIO GALAXIES CYCLE 4; MEDIUM ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Pi Wil Jm Van Breugel 2460 USA Robert Antonucci 1570 USA Arjun Dey 1500 USA ------------------------------------------------------------------------------------ 3. Description of proposed observations. The aim of this proposal is to study the rest-frame near-UV continuum polarization of the aligned high-z radio galaxy 3C368 using the WFPC2+QPOL+F555W instrument configuration. We will image the target in two separate observing sessions, each with the instrument in a different orientation (i.e. telescope in a different roll angle). The relative orientation angle between the two obs- erving sessions must be 45+/-3D -- this is a crucial requirement of our project. In addition, we request that the orientation during the first observing session be 150D and that during the second observing session be 105D, since these angles exclude a bright (11.1 mag.) star from the FOV of the WF CCDs. We also require that the orientation be held constant for the length of each observing session. During each observing session we will take 4 exposures (each 2200S long) with the target centered on WF4 and then 4 exposures (each 2200S long) with the target centered on WF2. The CCDs sample orthogonal polarization states and each observing session will allow us to construct one linear Stokes parameter. We request that the two observing sessions be scheduled in early July and late August since this appears to be optimal for our requirements. We also request that the two observing sessions be scheduled as close together in time as is possible, in order to avoid any temporal instrumental variations. The bright star that must be avoided lies roughly 103"E and 19"S of our target. We request that it not fall on any of the WFPC2 CCDs to avoid image blooming and any residual images on the CCDs since we will be using both WF2 and WF4 to image our target. ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. The aim of this proposal is to investigate the rest-frame UV continuum polarization properties of the high-redshift radio galaxy 3C368. Ground-based observations have shown that low-redshift radio galaxies have UV continuum emitting regions that appear to be clumped on kpc scales. In addition, HST observations of high-z radio galaxies also have clumpy continuum morphologies. As a result HST's high spatial resolution is crucial in order to understand the origin of the continuum emission of radio galaxies at high-z. In addition, ground -based polarimetry observations are generally hampered by systematic errors due to a spatially and temporally variable sky background. Even small amounts of cirrus can cause a detectable polarization which results in systematic errors in the measured percent polarization. HST sees a dark, constant sky and is therefore free of these problems. Page 3 ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. We request that all the observations required for this project be taken in two observing sessions. In the first observing session we will observe the target first on WF4 and then on WF2 in order to obtain the orthogonal polarization images. These exposures must be consecutive to minimize any possible temporal changes in the camera and the instrument must be in the same orientation for the length of the first observing session. We request that ORIENT=150D+/-5D since this avoids a bright (11.1 mag) star falling on one of the CCDs. In the second observing session we will repeat this sequence (first WF4 exposures, then WF2) but with the instrument in an orien- tation that is -45D+/-3D from the orientation of the first observing session, i.e. ORIENT=105. We estimate that the optimal time of year for the 150D and 105D orientations are around Jul 11 and Aug 28. We would like the two observing sessions to be as close in time as possible but are limited by the position of the bright star. For the times requested here, the sun is at ecliptic longitudes roughly 162D and 156D whereas the target is at ecliptic longitude 271.5D. Thus, the observations requested here are optimal for our program. We also request that the sequence in each observing session be first the WF4 pointing and then the WF2 pointing. The reason for this is that in the event that the telescope roll angle is different from that requested here, then the SEQuence requested images the target on WF4 BEFORE this CCD is exposed to the bright star. If the observations were taken in the reverse order (first WF2, then WF4) the star may leave a residual image on the WF4 CCD which would contaminate the observation of the target with this CCD. ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. We request that calibration images of a polarization position angle standard (chosen from the list compiled by Schmidt, Elston and Lupie, A.J. 104:1563) be observed in all the instrument configurations requested here. We require an accuracy of <1% in the measurement of the percent polarization and an accuracy of ~1 degree in the measurement of the polarization position angle. For the standard star BD+59389, V=9.07, this requires an exposure time of 1s per polarization filter position. Since flat fielding is important for this project (because we are using 2 different CCDs for the 2 orthogonal rays) we request flat fields taken as close to our observing sessions as possible. ------------------------------------------------------------------------------------ 8. Additional comments or special requests. Page 4 ------------------------------------------------------------------------------------ 9. Description of previous HST work. Van Breugel is collaborating with Miley on 'A Study of the Most Distant Galaxies ' (No. 2438, Miley P.I., van Breugel and Chambers co-I). These data have been analyzed. Antonucci has worked with the FOS-team on a broad range of AGN and Quasar GTO data, with H. Ford and M. Burbidge as P.I.'s., and with Kinney is involved in a number of GO projects. He has finished his HST UV spectroscopic study of OI287 (No. 2123). Spectropolarimetry observations of NGC 1068 (No.2077) are being analyzed, and a UV spectrum of Cygnus A (No. 2177) has just been received. Antonucci has received some pre-CoStar HST FOC polarization data of the central regions of radio galaxies (No. 3790, 4539), and further data is expected depending on the schedule of the HST servicing mission. The HST observations by Miley et al on the most distant radio galaxies showed that high redshift radio galaxies have compact, high surface brightness knots, which implies that HST is well suited for imaging studies of objects like 3C368. Antonucci's HST studies are all related to the investigation of various aspects of AGN `Unification' models for Seyferts and radio galaxies. His FOC imaging polarimetry of a radio galaxies is aimed at finding evidence for scattering in their central regions. They were not selected in order to study the alignment effect in high-z radio galaxies. His observations may shed light on the issue of scattered light from radio AGNs, but the exposures were very short (30 min total per object), and deconvolution of the aberrated images will not be possible with good s/n. There is no overlap in the samples. 'HST imaging of distant galaxies: 4C 41.17 at z = 3.8, Miley, Chambers, van Breugel, and Macchetto, Ap.J.Lett. 401, L69 (1992). 'Distant Galaxies', Miley, in Proc. ST-ECF / STScI Workshop "Science with the Space Telescope" eds. P. Benevenuti and E. Schreier, ESO Conf. and Workshop Proc. No. 44, p1 (1993). Antonucci is (co-)-author on the following papers using HST data: 'FOS spectroscopy of resolved structure in the nucleus of NGC 1068', (Caganoff et al., Ap.J.Lett. 377, L9 1991). 'HST imaging of the inner 3 arcseconds of NGC 1068 in the light of [OIII]5007', Evans et al. Ap.J.Lett. 369, L27 (1991). 'Far UV spectroscopy of the QSO UM 675 with the FOS and HST', Beaver et al. Ap.J.Lett. 377, L1 (1991). 'FOS observations of CSO 251', Cohen et al., in the First year of Observations wit the HST (1991; Kinney and Blades eds.). 'The optical jet in Mk 463', Uomoto et al. AJ 105, 1308 (1993). 'HST UV spectroscopy of the highly polarized but quiescent quasar OI 287', Antonucci, Kinney and Hurt, Ap.J. (in press). ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). Van Breugel (IGPP/LLNL) and Antonucci (UCSB) have workstations which support a variety of data analyses packages, including SDAS/IRAF, as well as normal institutional support. Some support for graduate students at UCSB and UC Berkeley is available. It would be very desirable to involve more of our students and post -docs if STScI funding were available. ------------------------------------------------------------------------------------ 11. Address Information Name: WIL JM VAN BREUGEL Category: PI Institution: 2460 Address: INST. OF GEOPHYSICS & PLANETARY PHYSICS LAWRENCE LIVERMORE NATIONAL LABORATORY P.O. BOX 808, L-413 City: LIVERMORE State: CA Zip Code: 94550 Country: USA Telephone: (510) 422-7195 Telex (or e-mail): wil@sundial.llnl.gov ------------------------------------------------------------------------------------ Page 5 Name: ARJUN DEY Category: CON Institution: 1500 Address: 601 CAMPBELL HALL UNIVERSITY OF CALIFORNIA AT BERKELEY City: BERKELEY State: CA Zip Code: 94720 Country: USA Telephone: (510) 642-3163 Telex (or e-mail): dey@bigz.berkeley.edu, FAX:(510)642-3411 ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 5429 [ 6] ------------------------------------------------------------------------------------------------------------------------------------ 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 3C368 E,315,325 RA = 18H 02M 45.6S +/- 0.1S, 1950 Z=1.132 1 SURF-CONT(5500)=1.0E-18,SIZE=0.225 DEC = +11D 01' 15.0" +/- 2 F(5500)=1.2E-19 0.5" Comments: THE EXPOSURE TIMES AND S/N LISTED BELOW WERE ESTIMATED FOR A SURFACE BRIGHT. DETECTION THRESHOLD OF 1 MICROJY/[]" IN AN AREA OF 0.16 SQ. ARCSEC AND A POINT SOURCE DETECTION THRESHOLD OF 0.12 MICROJY SINCE WE EXPECT THE TARGET TO BE CLUMPED. FLUXNUM_2 AND FLUXVAL_2 CORRESPOND TO THE EXPECTED CLUMP PARAMETERS. ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5429 [ 7] ------------------------------------------------------------------------------------------------------------------------------------ 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 3C368 WFPC2 IMAGE WF4 F555W, SUM=1X1 1 1900S 20 1 1 CYCLE 4 / 1-4.1 POLQ CR-SPLIT=NO 8800S 2 SEQ 1-2.1 WITHIN READ=YES 14D ORIENT 150D +/- 5D Comments: POL PA=0; TELESCOPE ROLL ANGLE MUST BE THE SAME FOR EXPOSURE LINES 1-2.1 THE S/N AND EXP TIME ARE FOR AN EXT. SOURCE OF 1 MICROJY/SQ.ASEC IN A 0.16 SQ.ASEC. AREA AND A 0.12 MICROJY POINT SOURCE CLUMP. ------------------------------------------------------------------------------------------------------------------------------------ 1.1 3C368 WFPC2 IMAGE WF4 F555W, SUM=1X1 3 2300S 20 1 1 SAME ORIENT FOR POLQ CR-SPLIT=NO 8800S 2 1.1-2.1 AS 1 READ=YES ------------------------------------------------------------------------------------------------------------------------------------ 2 3C368 WFPC2 IMAGE WF2 F555W, SUM=1X1 1 1900S 20 1 1 POLQ CR-SPLIT=NO 8800S 2 READ=YES ------------------------------------------------------------------------------------------------------------------------------------ 2.1 3C368 WFPC2 IMAGE WF2 F555W, SUM=1X1 3 2300S 20 1 1 POLQ CR-SPLIT=NO 8800S 2 READ=YES ------------------------------------------------------------------------------------------------------------------------------------ 3 3C368 WFPC2 IMAGE WF4 F555W, SUM=1X1 1 1900S 20 1 1 SEQ 3-4.1 WITHIN POLQ CR-SPLIT=NO 8800S 2 14D READ=YES ORIENT -45D +/- 3D FROM 1 AFTER 2 BY 60D +/- 60D Comments: POL PA=0+45; TELESCOPE ROLL ANGLE MUST BE THE SAME FOR EXPOSURE LINES 3-4.1 THE S/N AND EXP TIME ARE FOR AN EXT. SOURCE OF 1 MICROJY/SQ.ASEC IN A 0.16 SQ.ASEC. AREA AND A 0.12 MICROJY POINT SOURCE CLUMP. ------------------------------------------------------------------------------------------------------------------------------------ 3.1 3C368 WFPC2 IMAGE WF4 F555W, SUM=1X1 3 2300S 20 1 1 SAME ORIENT FOR POLQ CR-SPLIT=NO 8800S 2 3.1-4.1 AS 3 READ=YES ------------------------------------------------------------------------------------------------------------------------------------ 4 3C368 WFPC2 IMAGE WF2 F555W, SUM=1X1 1 1900S 20 1 1 POLQ CR-SPLIT=NO 8800S 2 READ=YES ------------------------------------------------------------------------------------------------------------------------------------ 4.1 3C368 WFPC2 IMAGE WF2 F555W, SUM=1X1 3 2300S 20 1 1 POLQ CR-SPLIT=NO 8800S 2 READ=YES ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 5429 [ 8] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SUM=1X1 CR-SPLIT=NO READ=YES ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 9.78 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category QUASARS & AGN ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category RADIO GALAXIES ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CYCLE 4 / 1-4.1; SEQ 1-2.1 WITHIN 14D; ORIENT 150D +/- 5D; SAME ORIENT FOR 1.1-2.1 AS 1 SEQ 3-4.1 WITHIN 14D; ORIENT -45D +/- 3D FROM 1; AFTER 2 BY 60D +/- 60D SAME ORIENT FOR 3.1-4.1 AS 3; ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F555W,POLQ ------------------------------------------------------------------------------------------------------------------------------------ Target Names 3C368 ------------------------------------------------------------------------------------------------------------------------------------