6576( 28) - 03/18/98 15:35 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6576 Version: 28 Check-in Date: 18-Mar-1998 15:34:40 1.Proposal Title: HST imaging of the two most distant radio galaxies ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 6 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: MARK LACY UNIVERSITY OF OXFORD CoI: Hyron Spinrad University of California, Berkeley N CoI: Arjun Dey University of California, Berkeley N CoI: Steve Rawlings Astrophysics, Oxford University N ------------------------------------------------------------------------------------ 5. Abstract The recent discovery of two radio galaxies at z>4, 8C1435+635 (z=4.25) and 6C0140+326 (z=4.41) has allowed us to investigate spatially resolved objects within the first Gyr of the lifetime of a closed Universe. We require high-resolution imaging of these objects with the HST in LyAlpha and continuum. In conjuction with ground based data, HST images will allow us to study the neutral gas and dust content of these galaxies, and constrain the UV emission mechanism and the LyAlpha ionisation mechanism. In the case of 6C0140+326, LyAlpha falls within the narrow- band F658N filter, facilitating a deep narrow-band search of the field for companion galaxies. Such a search will be highly sensitive to small scale-size sub-units of star-forming gas which will later merge into more massive galaxies. A candidate emission- line object has already been found using ground-based observations; this can be observed at the same pointing as the radio galaxy itself. ------------------------------------------------------------------------------------ 6576( 28) - 03/18/98 15:35 - [ 2] Observations Description ------------------------ Target observations: 1)8C1435+635: We require observations with the Wide-Field Camera (WFC) through filter F814W to study the structure of the galaxy in continuum and F622W to study the LyAlpha emission. The fact that 8C1435+635 falls very near the centre of the CVZ means that we can make very good use of the observing time to obtain deep images, exposing for 3X1500s per orbit for 5 orbits per filter. The exposure times required to achieve a given signal-to- noise ratio will depend on the sizes of the optical structures, which of course we do not know at present. By analogy with the previous highest-z galaxy, 4C41.17 though, we might expect much of the emission to come from barely resolved knots or clumps. Nevertheless, to enhance our surface brightness sensitivity we have decided to use the WFC. We have estimated our exposure times and limiting magnitudes based on measurements from actual, very long WFPC2 exposures (Dickinson private communication), and the WFPC2 exposure time calculator. With 15X1500s exposures through the F814W filter, we anticipate a 5 sigma point source detection limit of AB=27.8, which will allow us to detect any unresolved (<~ 1 kpc^2) features having > 3% of the total I-band flux. Our corresponding 5 sigma surface brightness limit is AB=26.4 mag in an aperture of 1 arcsec^2. If the light is smoothly spread over an area of 3 arcsec^2 (the approximate size as measured from our I-band Keck image), we will achieve an approx 5 sigma detection of flux in every 3X3 pixel (approx 0.3X0.3 arcsec^2) box within this area. Imaging in LyAlpha is hampered by the lack of a suitable narrow-band filter. The LRF has a break in coverage at 6402A, just beyond the peak of our 40A -wide LyAlpha line at 6399A. Nevertheless, the high EW of the LyAlpha line (approx 1000A ), and the factor of four continuum discontinuity across LyAlpha will allow us to use the F622W filter to obtain an image which will be dominated by the line contribution with only an approx 5% contribution from the continuum, albeit at the expense of additional noise from the sky. If the line and continuum structures are seen to be very different, we can subtract a scaled version of the I-band image to obtain a pure line-emission image. Again, we expect much of the emission to be clumpy, and 15X1500s observations through the F622W filter and WFC will enable us to obtain a 5 sigma point source detection limit of 2 X 10^-17 ergs^-1cm^-2, allowing detection of any unresolved clump of emission with > 5% of the total LyAlpha flux of the galaxy. Our 5 sigma surface brightness sensitivity will be 6.0X10^- 17 ergs^-1cm^-2 in 1 arcsec^2. If the source is smoothly spread out over an area of 3 arcsec^2, then we will achieve a 5 sigma detection of the flux in each 5X5 pixel box. 2)6C0140+326: For this galaxy, we originally requested images through the F814W filter to study the continuum and F658N to study the line emission. We wished expose for 2X1000s per orbit for 10 orbits per band. Following the Phase I allocation and report of the TAC we have decided to observe this object for two orbits in the F658N filter and a continuum filter to obtain a LyAlpha image of the radio galaxy. For the LyAlpha image of the galaxy the FWHM of the LyAlpha emission is >~1-arcsec and the LyAlpha flux is 8.7X10^-16 ergs^-1cm^-2 giving 3 sigma per pixel in the WFC if the flux is smoothly spread out. We plan to observe at different pointings per orbit to allow the identification and removal of hot pixels. By separating our pointings by offsets corresponding to non-integer numbers of pixels we hope to improve the effective sampling of the PSF. Parallel observations with the FOC: In order to maximize the potential of HST for serendipitous discoveries, we request parallel UV imaging observations with the FOC and the F220W, F275W and F342W filters. Although the field of view of the F/96 relay is small, our integration times will be very long and should reach interestingly faint flux limits. The ``faint blue galaxy'' population seen (e.g.) in Tyson's deep field imaging data is numerous and presumably UV--bright, and we should have a reasonable chance of obtaining ultraviolet photometry and perhaps morphologies for several such objects. The cost in terms of telescope overhead is negligible, and the opportunity for chance discovery using HST's unique ultraviolet capabilities is worth the additional effort. We wish to maintain the same telescope ORIENT angle throughout these observations, both to minimize interpolations necessary for stacking the WFPC2 images, and to maintain the field of the FOC at the same pointing for the parallel observations. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 6576( 28) - 03/18/98 15:35 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 6576( 28) - 03/18/98 15:35 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 GAL- GALAXY,RADIO RA=14H 35M 27.6S +/- 1950 Z=4.25 SURF(I) = 26+/-1 1436+6319 GALAXY,HIGH REDSHIFT 0.1S,DEC=63D 32' 12.5" +/- 1" GALAXY Comments: V>26 2 GAL- GALAXY,RADIO RA=01H 40M 51.51S +/- 1950 Z=4.41 SURF(I) = 26+/-1 0143+3253 GALAXY,HIGH REDSHIFT 0.1S,DEC=32D 38' 45.6" +/- 1" GALAXY Comments: V>26 6576( 28) - 03/18/98 15:35 - [ 5] Visit: 01 Visit Priority: Visit Requirements: PCS MODE FINE CVZ SAME ORIENT AS 02 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 GAL-1436+63 WFPC2 IMAGE WFALL F814W 3 1400 S PAR 15 WITH 10 19 ------------------------------------------------------------------------------------------------------------------------------------ 15 ANY FOC/96 IMAGE 512X102 F220W PIXEL=50x25 2 2100 S 4 ------------------------------------------------------------------------------------------------------------------------------------ 20 GAL-1436+63 WFPC2 IMAGE WFALL F814W 3 1400 S POS TARG 0.5,0.25 PAR 25 19 WITH 20 ------------------------------------------------------------------------------------------------------------------------------------ 25 ANY FOC/96 IMAGE 512X102 F220W PIXEL=50x25 2 2100 S 4 ------------------------------------------------------------------------------------------------------------------------------------ 30 GAL-1436+63 WFPC2 IMAGE WFALL F814W 3 1400 S POS TARG 0.75,0.75 PAR 35 19 WITH 30 ------------------------------------------------------------------------------------------------------------------------------------ 35 ANY FOC/96 IMAGE 512X102 F220W PIXEL=50x25 2 2100 S 4 ------------------------------------------------------------------------------------------------------------------------------------ 40 GAL-1436+63 WFPC2 IMAGE WFALL F814W 3 1400 S POS TARG 0.25,0.5 PAR 45 19 WITH 40 ------------------------------------------------------------------------------------------------------------------------------------ 45 ANY FOC/96 IMAGE 512X102 F220W PIXEL=50x25 2 2100 S 4 ------------------------------------------------------------------------------------------------------------------------------------ 6576( 28) - 03/18/98 15:35 - [ 6] Visit: 02 Visit Priority: Visit Requirements: PCS MODE FINE CVZ SAME ORIENT AS 01 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 ------------------------------------------------------------------------------------------------------------------------------------ 50 GAL-1436+63 WFPC2 IMAGE WFALL F622W 3 1300 S PAR 55 WITH 50 19 ------------------------------------------------------------------------------------------------------------------------------------ 55 ANY FOC/96 IMAGE 512X102 F220W PIXEL=50x25 2 1500 S 4 ------------------------------------------------------------------------------------------------------------------------------------ 60 GAL-1436+63 WFPC2 IMAGE WFALL F622W 3 1300 S POS TARG 0.5,0.25 PAR 65 19 WITH 60 ------------------------------------------------------------------------------------------------------------------------------------ 65 ANY FOC/96 IMAGE 512X102 F220W PIXEL=50x25 2 2100 S 4 ------------------------------------------------------------------------------------------------------------------------------------ 70 GAL-1436+63 WFPC2 IMAGE WFALL F622W 3 1300 S POS TARG 0.75,0.75 PAR 75 19 WITH 70 ------------------------------------------------------------------------------------------------------------------------------------ 75 ANY FOC/96 IMAGE 512X102 F275W PIXEL=50x25 2 2100 S 4 ------------------------------------------------------------------------------------------------------------------------------------ 80 GAL-1436+63 WFPC2 IMAGE WFALL F622W 3 1300 S POS TARG 0.25,0.5 PAR 85 19 WITH 80 ------------------------------------------------------------------------------------------------------------------------------------ 85 ANY FOC/96 IMAGE 512X102 F275W PIXEL=50x25 3 1400 S 4 ------------------------------------------------------------------------------------------------------------------------------------ 87 GAL-1436+63 WFPC2 IMAGE WFALL F622W 1 1100 S POS TARG 0.25,0.5 PAR 88 19 WITH 87 ------------------------------------------------------------------------------------------------------------------------------------ 88 ANY FOC/96 IMAGE 512X102 F342W PIXEL=50x25 1 1200 S 4 ------------------------------------------------------------------------------------------------------------------------------------ 6576( 28) - 03/18/98 15:35 - [ 7] Visit: 03 Visit Priority: Visit Requirements: PCS MODE FINE On Hold Comments: Additional Comments: Any orient angle is OK, provided it is maintained throughout the visit Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 101 GAL-0143+32 WFPC2 IMAGE WFALL F675W 2 1000 S SEQ 101,120,126 NON-INT 53 PAR 105 WITH 101 ------------------------------------------------------------------------------------------------------------------------------------ 105 ANY FOC/96 IMAGE 512X102 F275W PIXEL=50x25 2 1140 S 4 ------------------------------------------------------------------------------------------------------------------------------------ 120 GAL-0143+32 WFPC2 IMAGE WFALL F658N 1 1400 S PAR 125 WITH 120 53 ------------------------------------------------------------------------------------------------------------------------------------ 125 ANY FOC/96 IMAGE 512X102 F275W PIXEL=50x25 1 1640 S 4 ------------------------------------------------------------------------------------------------------------------------------------ 126 GAL-0143+32 WFPC2 IMAGE WFALL F658N CR-SPLIT=NO 1 700 S PAR 127 WITH 126 53 ------------------------------------------------------------------------------------------------------------------------------------ 127 ANY FOC/96 IMAGE 512X102 F342W PIXEL=50x25 1 700 S 4 ------------------------------------------------------------------------------------------------------------------------------------ 6576( 28) - 03/18/98 15:35 - [ 8] Summary Form for Proposal 6576 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 FOC/96 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters PIXEL=50x25 CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PCS MODE FINE CVZ SAME ORIENT AS 02 PAR 15 WITH 10 POS TARG 0.5,0.25 PAR 25 WITH 20 POS TARG 0.75,0.75 PAR 35 WITH 30 POS TARG 0.25,0.5 PAR 45 WITH 40 PCS MODE FINE CVZ SAME ORIENT AS 01 PAR 55 WITH 50 POS TARG 0.5,0.25 PAR 65 WITH 60 POS TARG 0.75,0.75 PAR 75 WITH 70 POS TARG 0.25,0.5 PAR 85 WITH 80 POS TARG 0.25,0.5 PAR 88 WITH 87 PCS MODE FINE SEQ 101,120,126 NON-INT PAR 105 WITH 101 PAR 125 WITH 120 PAR 127 WITH 126 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F814W F220W F622W F275W F342W F675W F658N ------------------------------------------------------------------------------------------------------------------------------------ Target Names GAL-1436+6319 ANY GAL-0143+3253 ------------------------------------------------------------------------------------------------------------------------------------