6703( 7) - 07/10/96 11:57 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6703 Version: 7 Check-in Date: 10-Jul-1996 11:51:03 1.Proposal Title: Weak radiogalaxies at z > 2: imaging a unique sample ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle AGN GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Steve Rawlings OXFORD UNIVERSITY CoI: Gary Hill McDonald Observatory, University of Texas, N CoI: Susan Ridgway University of Hawaii, N CoI: Steve Eales Astronomy, Cardiff University N CoI: Mark Lacy Astrophysics, Oxford University N CoI: Katherine Blundell Astrophysics, Oxford University N CoI: Duncan Law-Green NRAL, Manchester University N ------------------------------------------------------------------------------------ 6. Abstract Only the HST can deliver the resolution necessary to investigate the structure of galaxies at redshifts z > 2. To date, studies have focussed almost exclusively on galaxies of extreme radio luminosity, and their clumpy radio-aligned structures are an almost certain selection effect. The two radio-weak z>2 galaxies imaged by HST have recognisably `galaxy-like' envelopes, with weak or absent AGN, and little radio -aligned optical emission. A concerted HST study of high- z radio-weak galaxies is now vital, and our 7C redshift survey provides the first (and only) suitable sample. Its two key features are: (i) a flux limit 20-times fainter than 3C; and (ii) essentially complete spectroscopic redshifts. 7C galaxies at z ~ 2 are well matched in radio luminosity to 3C galaxies at z ~ 0.5 which optically are fairly normal ellipticals; 7C data together with existing 3C HST data can chart the redshift evolution of galaxy structure at a fixed, non-extreme radio luminosity. Moreover, 7C galaxies are 5--10 times less radio-luminous than previous HST targets at z > 2, allowing new studies of structure as a function of radio luminosity at a fixed, high redshift. We plan to image the 14 7C galaxies and 5 7C quasars at z>2, requiring 51 HST orbits for two colours. This is a substantial time investment, but is merited by the uniqueness of the 7C sample which provides the best hope of studying (relatively) normal galaxies at high redshift, and which can extract the maximum science from the existing HST database at high-z . ------------------------------------------------------------------------------------ 6703( 7) - 07/10/96 11:57 - [ 2] Observations Description ------------------------ We will use WFPC2, placing each 7C galaxy target near the centre of one of the Wide Field (~ 0.1 arcsec per pixel) CCDs, and each 7C quasar near the centre of the Planetary Camera (PC) CCD. This choice maximises the signal-to-noise ratio on resolved structures in the galaxies, as well as providing more sensitivity and field-size with which to study any companion objects. Better sampling of the PSF will be essential for the quasar targets, and the PC should be used. We will use two filters per target, following the strategy adopted by the Hubble Deep Field Project to obtain colour information with the loss of very little sensitivity (0.1-- 0.2 magnitudes). The filters have been chosen (F606W, F814W) on the basis of high throughput, and in the case of F814W because the targets are expected to have spectral energy distributions rising into the red. These filters also avoid contamination by the bright LyAlpha emission line at the redshifts of interest. Since the details of the optical structures are not yet known, we have opted for a single programme of exposing for similar times on all objects (there is no correlation between optical magnitude and redshift for our targets). Three jittered exposures per orbit will allow cosmic ray and hot pixel removal, as well as affording some improvement of PSF sampling: we will consult with HST experts at the Phase II stage to decide on the exact form of jittering to be used. We have simulated galaxy images on the assumption that a typical orbit allows 1800s exposure in total, and find that to satisfy all of our objectives we require 3600s in the F814W filter. We will add a further 1800s in the F606W to add colour information, and to add some margin for error in our signal-to-noise calculation (since we can stack the V and I images). Three orbits are therefore sufficient and necessary for most objects: fortunately, however, 6 of our targets lie in the CVZ so their required I- band exposure can be achieved in 1 orbit; a second orbit in the F606W filter will again be added. Details of our signal- to-noise calculations follow: we assumed that light from our galaxies will be dominated by the smooth envelope component seen in the Windhorst et al. and Giavalisco et al. studies. Following Windhorst et al. we adopted a de Vaucouleurs profile with an effective radius r_e= 5 kpc (H_0=50; Omega_0=1) and z ~ 2. We fixed the total magnitude to the faintest measured in our ground-based studies, e.g. V = 24; I = 23.0. Without smoothing it is still easy to discern the diffuse structure out to a radius of 6 or so pixels (~0.6 arcsec), which is sufficient and necessary to establish a smoothly varying (e.g. r^frac14) light profile. One gets similar results using the WFPC2 exposure time calculator. Spreading an I=23 galaxy uniformally over 2 arcsec^2 (reasonable both from the model assumed above, and from the ground-based images) leads to a signal-to-noise (s:n) ratio of 2 (splitting a 3600s F814W integration into 6 exposures) per WFPC2 pixel. Assuming instead an r^frac14 law for the surface brightness (and r_e=5 kpc), the s:n in the outermost of a set of concentric aperture rings drops to ~ 1 at a radius of ~ 0.7 arcsec (estimated from our simulation, but see also Fig. 2\\ of Giavalisco et al. for a similar result on real HST data for a similar magnitude object). We are therefore confident that even in our faintest targets we will have the s:n to detect and characterise smoothly varying light profiles. Additionally, of course, we will be extremely sensitive to unresolved sources, such as those associated with an AGN, compact sub-clumps and/or knots aligned with the radio axis. Our 3 Sigma point source sensitivity will be around I = 27, more than adequate to detect quasars buried by A_V ~ 7 if they are intrinsically as bright as those already known in the 7C sample. Real Time Justification ----------------------- 6 targets in our complete sample lie in the region of the CVZ, and we request CVZ status for these to allow longer object exposures. Follow-up of the 7C redshift survey is an important part of the Oxford programme of research on high-z galaxies. Several supporting projects have already been awarded time on UK and US telescopes. Three-frequency polarization-calibrated VLA observations were made this summer of all the HST targets with a best resolution of ~ 0.2 arcsec at 8.4 GHz; 132 hours of MERLIN observations will provide even higher resolution images (~ 0.1 arcsec resolution at 1.6 GHz) later this year. Deep R- band images will be obtained over 4 nights at the McDonald 107-inch this November (to complement existing data); deep K-band imaging, and near-infrared spectroscopy will be completed in 7 nights awarded on the UKIRT during Jan. 1996; and finally, deep, and hopefully ~ 0.5 arcsec resolution, ground-based images will be obtained through V and I filters over 5 nights on the NOT telescope in Jan. 1996. If seeing conditions permit, these latter observations will help recover information on the structures of the galaxies on scales larger than those to which WFPC2 is sensitive. We also plan searches for companion galaxies (and potential foreground gravitational lensing structures) using three techniques: LyAlpha imaging in the optical at the WHT; OIII and HAlpha imaging in the near-infrared at the UKIRT; and multi-colour optical/near -infrared searches for the 4000 Angstrom break. Needless to say, the proposed HST observations are pivotal to the overall success of the programme. vspace*0.2in The observing team. We have constructed an observing team with the expertise and manpower necessary to expedite this large project. In addition to the team behind the original 7C survey (Rawlings, GH, SE, ML), we have added experts on each aspect of the high resolution programme, e.g. VLA mapping (KB), MERLIN mapping (DLG) and WFPC2 imaging (Ridgway). Ridgway is a vital member of the team given her vast experience analysing data from the Stockton 3C campaign on HST (proposal 5401) -- she will be moving to Oxford in November 1995. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 6703( 7) - 07/10/96 11:57 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6703( 7) - 07/10/96 11:57 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 GAL- Galaxy RA = 02H 25M 16.73S +/- 0.1S, J2000 Z = 2.98 V = 22.5+/-0.5 0225+3118 DEC = +31D 18' 57.9" +/- 1.0" 2 GAL- Galaxy RA = 08H 12M 19.27S +/- 0.1S, J2000 Z = 2.43 V = 23.0+/-0.5 0812+2630 DEC = +26D 30' 15.6" +/- 1.0" 3 GAL- Galaxy RA = 08H 28M 38.95S +/- 0.1S, J2000 Z = 2.22 V = 23.1+/-0.5 0828+2528 DEC = +25D 28' 26.5" +/- 1.0" 4 GAL- Galaxy RA = 17H 58M 46.60S +/- 0.1S, J2000 Z = 2.70 V = 23.0+/-0.5 1758+6720 DEC = +67D 20' 07.9" +/- 1.0" 6703( 7) - 07/10/96 11:57 - [ 5] Visit: 01 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 GAL-0225+31 WFPC2 IMAGE WFALL F702W CR-SPLIT = NO 2 800 S LOW-SKY 18 ------------------------------------------------------------------------------------------------------------------------------------ 2 GAL-0225+31 WFPC2 IMAGE WFALL F702W CR-SPLIT = NO 1 500 S LOW-SKY 18 ------------------------------------------------------------------------------------------------------------------------------------ 3 GAL-0225+31 WFPC2 IMAGE WFALL F702W CR-SPLIT = NO 2 800 S POSition TARGet 0.50,0.25 18 LOW-SKY ------------------------------------------------------------------------------------------------------------------------------------ 4 GAL-0225+31 WFPC2 IMAGE WFALL F702W CR-SPLIT = NO 1 600 S SAME POSition AS 3 18 LOW-SKY ------------------------------------------------------------------------------------------------------------------------------------ 5 GAL-0225+31 WFPC2 IMAGE WFALL F702W CR-SPLIT = NO 2 800 S POSition TARGet 0.25,0.50 18 LOW-SKY ------------------------------------------------------------------------------------------------------------------------------------ 6 GAL-0225+31 WFPC2 IMAGE WFALL F702W CR-SPLIT = NO 1 600 S SAME POSition AS 5 18 LOW-SKY ------------------------------------------------------------------------------------------------------------------------------------ 6703( 7) - 07/10/96 11:57 - [ 6] Visit: 02 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 GAL-0812+26 WFPC2 IMAGE WFALL F702W CR-SPLIT = NO 2 800 S LOW-SKY 30 ------------------------------------------------------------------------------------------------------------------------------------ 2 GAL-0812+26 WFPC2 IMAGE WFALL F702W CR-SPLIT = NO 1 500 S LOW-SKY 30 ------------------------------------------------------------------------------------------------------------------------------------ 3 GAL-0812+26 WFPC2 IMAGE WFALL F702W CR-SPLIT = NO 2 800 S POSition TARGet 0.50,0.25 30 LOW-SKY ------------------------------------------------------------------------------------------------------------------------------------ 4 GAL-0812+26 WFPC2 IMAGE WFALL F702W CR-SPLIT = NO 1 600 S SAME POSition AS 3 30 LOW-SKY ------------------------------------------------------------------------------------------------------------------------------------ 5 GAL-0812+26 WFPC2 IMAGE WFALL F702W CR-SPLIT = NO 2 800 S POSition TARGet 0.25,0.5 30 LOW-SKY ------------------------------------------------------------------------------------------------------------------------------------ 6 GAL-0812+26 WFPC2 IMAGE WFALL F702W CR-SPLIT = NO 1 600 S SAME POSition AS 5 30 LOW-SKY ------------------------------------------------------------------------------------------------------------------------------------ 6703( 7) - 07/10/96 11:57 - [ 7] Visit: 03 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 GAL-0828+25 WFPC2 IMAGE WFALL F702W CR-SPLIT = NO 2 800 S LOW-SKY 28 ------------------------------------------------------------------------------------------------------------------------------------ 2 GAL-0828+25 WFPC2 IMAGE WFALL F702W CR-SPLIT = NO 1 500 S LOW-SKY 28 ------------------------------------------------------------------------------------------------------------------------------------ 3 GAL-0828+25 WFPC2 IMAGE WFALL F702W CR-SPLIT = NO 2 800 S POSition TARGet 0.50,0.25 28 LOW-SKY ------------------------------------------------------------------------------------------------------------------------------------ 4 GAL-0828+25 WFPC2 IMAGE WFALL F702W CR-SPLIT = NO 1 600 S SAME POSition AS 3 28 LOW-SKY ------------------------------------------------------------------------------------------------------------------------------------ 5 GAL-0828+25 WFPC2 IMAGE WFALL F702W CR-SPLIT = NO 2 800 S POSition TARGet 0.25,0.5 28 LOW-SKY ------------------------------------------------------------------------------------------------------------------------------------ 6 GAL-0828+25 WFPC2 IMAGE WFALL F702W CR-SPLIT = NO 1 600 S SAME POSition AS 5 28 LOW-SKY ------------------------------------------------------------------------------------------------------------------------------------ 6703( 7) - 07/10/96 11:57 - [ 8] Visit: 04 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 GAL-1758+67 WFPC2 IMAGE WF3-FIX F702W CR-SPLIT = NO 2 800 S LOW-SKY 20 ------------------------------------------------------------------------------------------------------------------------------------ 2 GAL-1758+67 WFPC2 IMAGE WF3-FIX F702W CR-SPLIT = NO 1 400 S LOW-SKY 20 ------------------------------------------------------------------------------------------------------------------------------------ 3 GAL-1758+67 WFPC2 IMAGE WF3-FIX F702W CR-SPLIT = NO 2 800 S POSition TARGet 0.5,0.25 20 LOW-SKY ------------------------------------------------------------------------------------------------------------------------------------ 4 GAL-1758+67 WFPC2 IMAGE WF3-FIX F702W CR-SPLIT = NO 1 500 S SAME POSition AS 3 20 LOW-SKY ------------------------------------------------------------------------------------------------------------------------------------ 5 GAL-1758+67 WFPC2 IMAGE WF3-FIX F702W CR-SPLIT = NO 2 800 S POSition TARGet 0.25,0.5 20 LOW-SKY ------------------------------------------------------------------------------------------------------------------------------------ 6 GAL-1758+67 WFPC2 IMAGE WF3-FIX F702W CR-SPLIT = NO 1 500 S SAME POSition AS 5 20 LOW-SKY ------------------------------------------------------------------------------------------------------------------------------------ 6703( 7) - 07/10/96 11:57 - [ 9] Summary Form for Proposal 6703 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT = NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category AGN ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements LOW-SKY POSition TARGet 0.50,0.25 LOW-SKY SAME POSition AS 3 LOW-SKY POSition TARGet 0.25,0.50 LOW-SKY SAME POSition AS 5 LOW-SKY POSition TARGet 0.25,0.5 LOW-SKY POSition TARGet 0.5,0.25 LOW-SKY ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F702W ------------------------------------------------------------------------------------------------------------------------------------ Target Names GAL-0225+3118 GAL-0812+2630 GAL-0828+2528 GAL-1758+6720 ------------------------------------------------------------------------------------------------------------------------------------