Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 5758 Report Date: 18-Jul-95:17:56 Version: ********** Check-in Date: ********** 1.Proposal Title: WFPC2 IMAGING OF THE PROTOGALAXY CANDIDATE B2 0902+34 -LRF Observations ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID GALAXIES & CLUSTERS GO 5470 Sub Category DISTANT GALAXIES ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Peter R Eisenhardt JPL USA 818-354-4395 ------------------------------------------------------------------------------------ 7. Abstract We propose to obtain high spatial resolution imaging with WFPC2 of the continuum and Ly-alpha line emission from the distant radio galaxy B2 0902+34. This object appears to have the largest UV to optical (rest frame) flux ratio measured for a radio galaxy, and at z=3.395 is also among the most distant galaxies known. It is therefore an excellent candidate for a protogalaxy. Our objective is to obtain a clearer picture of the formation process in this galaxy. The proposed observations will reveal the distribution of star-forming regions and emission line gas, and the relationship between them, on a 1 kpc scale, as well as their relationship to the radio source structure. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 14.01 par: 0 10. Num targs pri: 1 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: WF/PC ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 5758 PI: Peter R Eisenhardt Proposal Title: WFPC2 IMAGING OF THE PROTOGALAXY CANDIDATE B2 0902+34 -LRF Observations ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Peter R Eisenhardt 2370 USA Simon Lilly 4664 CANADA Nanyao Y Lu 2370 USA Mark Dickinson 3470 USA ------------------------------------------------------------------------------------ 3. Description of proposed observations. This is a continuation of proposal 5470 (which used the Planetary Camera and F622W to measure the rest frame UV continuum in B2 0902+34.) Here we propose to obtain a total of 6.1 hours of integration with the linear ramp filter, placing B2 0902+34 as close as possible to the 5341 Angstrom position while keeping the target at least 3.5 arcsec from the edge of the WF4 array, to measure the redshifted Ly alpha morphology. Because of misalignment between the LRF and WFPC2 detectors, the best way to achieve this without significant changes in WFPC2 operations is to use a +15 degree SOFA rotation and position B2 0902+34 at 5324 Angstroms on ramp 2 of FR533N of the LRF. This places B2 0902+34 at pixel 763, 574, about 3.7 arcsec above the bottom of WF4. The integration times of 22000 seconds through the LRF will be broken into three groups, separated by integer numbers of WF4 pixels to avoid bad pixels, each group with 3 or 4 2200 second exposures. We use 2200 seconds as our estimate for the maximum available unocculted time per orbit, but because all of our observations will be read-noise limited, we hope that the actual per orbit exposure time can be adjusted to its maximum allowable length (within the constraint of the total spacecraft time allocation) in order to maximize our resulting S/N. The three exposures taken within each FGS lock position will suffice to allow cosmic ray removal, thus we set CRSPLIT=NO. The exposures taken through each filter should be obtained on consecutive orbits. ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. Figure 2 of section 2 of our Phase I proposal illustrates deep (hours of KPNO 4m time) subarcsec imaging in narrow and broadband filters of B2 0902+34. We have also obtained deep optical and near IR spectra, which confirm the corrections for line emssion to the continuum flux, and result in a flat, line-free continuum characteristic of a protogalaxy. Both the flat (young) SED and figure 2 suggest there is complex structure within the central 2 " of the source, corresponding to roughly 14 kpc. Detecting whether there are two subcomponents or many (many subcomponents are plausible for a dynamically young object) requires significantly better spatial resolution than Figure 2 provides, or is currently feasible from the ground, while HST's ability to resolve 1kpc scales is well matched to the expected substructure. We will propose to obtain space IR measurements of this object from ISO and SIRTF, when they become available. Page 3 ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. Our original proposal (GO 5470) to image the redshift 3.4 protogalaxy candidate B2 0902+34 in the UV continuum and in redshifted Lyman alpha at 5341 Angstroms has encountered difficulties due to misalignments in the WFPC2 linear ramp filter (LRF), which cause certain wavelength positions on the LRF to miss the WFPC detectors. This misalignment leads to gaps in the LRF wavelength coverage and 5341 Angstroms is unfortunately near the center of the largest gap. These gaps were not known at the time of cycle 4 proposals, but are summarized in Table 3.8 of the Version 2.0 WFPC2 Instrument handbook distributed for Cycle 5. I have discussed this problem at some length both with my collaborators and with Dr. Robin Evans of JPL, who is the expert on the LRF for the JPL WFPC2 team. To summarize: ************************************************************ * We request that the observation be made by positioning * * B2 0902+34 at the 5324 Angstrom position on the LRF when * * rotated to +15 degrees. * ************************************************************ Enabling the +15 degree LRF rotation would plug the single largest gap in the LRF wavelength coverage, and thus could be expected to benefit other proposals as well. We therefore believe this request is consistent with existing policy as stated in both versions 1.0 and 2.0 of the WFPC2 instrument handbook: "...the linear ramp filters require partial rotation of the SOFA wheels to -18 and -33 degrees from their nominal positions, to recover wavelength regions which would fall on the PC camera or otherwise be lost." The +15 degree rotation of the SOFA wheels is supported for the polarizer quad filter as shown in Table 3.10 of version 2.0 of the handbook, placing it in the same category as -18 and -33 degrees. My collaborators and I agree that the scientific importance of the Lyman alpha image is very high and that we should attempt to obtain it if at all possible. The observed equivalent width of the line is roughly 1000 Angstroms, and its spatial distribution is of great interest both as a tracer of the material available for star formation and of the ionizing continuum. The Lyman alpha morphology is known to be complex from groundbased imaging obtained by Mark Dickinson and Hy Spinrad (see Figure 1 of Eisenhardt and Dickinson, Ap.J. Letters 399, L47). The spatial extent of the higher surface brightness Lyman emission is about 7 arcsec in diameter, as shown in that figure. This spatial extent means that we need to position B2 0902+34 at least 3.5 arcsec onto the WFPC (this is a bare minimum as astrometric uncertainties as well as residual uncertainty about the LRF position of order one arcsec are present). With this criterion the closest available LRF wavelength without the +15 degree rotation is at 5377 Angstroms (on LRF ramp 3 at 0 degrees rotation), Which Dr. Evans calculates will fall at pixel 762, 292 on the WF4 chip, 3.8 arcsec from the bottom of the chip.Dr. Evans calculates the transmission of the LRF at this position to 5341 Angstrom light will be one half of the value which we based our exposure time calculations. Lyman alpha regions further away from the edge of WF4 will have lower transmission -only 25% of the peak value at points 7 arcsec from the chip edge.This will lead to a compromised Lyman alpha observation which is difficult to calibrate and interpret. However, with a +15 degree rotation (a SOFA rotation analagous to -18 or -33 in that it is supported for the polarizer quad filter) B2 0902+34 could be positioned at 5324 Angstroms on ramp 2 of FR533N of the LRF, falling at pixel 763, 574, about 3.7 arcsec above the bottom of WF4. The Lyman alpha transmission in this case would be about 93% of the peak value, falling to about 80% 7 arcsec from the chip edge. This Lyman alpha observation would be quite satisfactory. An option we rejected was to use F547M, which is the narrowest standard filter which includes 5341. Because F547M has a FWHM of 600 Angstroms it would be very difficult to disentangle the UV continuum contribution from the Lyman alpha emission in this filter. Page 4 ------------------------------------------------------------------------------------ 7. Data reduction and analysis plans. The major hurdle in reducing HST data prior to Cycle 4, i.e correcting for the degraded PSF function, will not be necessary with WFPC2. Following pipeline processing, we will devote special attention in the reduction process to cosmic ray (CR) removal. CR detection will be aided by the triply redundant images at each array location, and in the case of the continuum observations with the Planetary Camera by the distinct unresolved character of the CR PSF. We have developed software within IRAF specifically designed to detect and remove CR's from deep ground based exposures. We also have experience in accurately determining sky levels (crucial in IR photometry) and have dveloped software for this purpose as well. The Lya image will need to be corrected for continuum in the 1% bandpass of the LRF. We will scale our continuum filter image for this purpose, a procedure we have used successfully on similar groundbased data. If only a few compact well detected sources are evident at this point, we will attempt to fit and subtract PSF's to search for fainter neighboring components. We will perform surface brightness analysis on prominent components in a fashion simlar to that used by Windhorst et al. (1992). All data reduction and analysis will be done within IRAF/SDAS with which we have extensive experience. ------------------------------------------------------------------------------------ 9. Description of previous HST work. 4575 "WF/PC Observations of the Most Luminous Galaxy in the Universe; the IRAS Source FSC 10214+4724", Peter Eisenhardt coI 1229 - "OPTICAL AND ULTRAVIOLET IMAGING OF LARGE REDSHIFT RADIO GALAXIES " S.Lilly coI 2365 - "HST IMAGING OF GROUND-BASED ULTRA-DEEP SURVEY FIELDS Simon J. Lilly PI 2684-KP - "HST MEDIUM- DEEP SURVEY: CYCLE 1 OBSERVATIONS S.Lilly coI (continuations in 4018, 4029, 4105, 4106) 2695 - "MORPHOLOGY OF PKS 1614+051, A QUASAR-GALAXY PAIR AT Z=3.21 M.Dickinson coI 2698 - "LYMAN-ALPHA IMAGING OF YOUNG AND FORMING GALAXIES AT LARGE REDSHIFTS " M.Dickinson coI 3543 - "THE DEEP ULTRAVIOLET SKY ", Simon J. Lilly PI 3654 - "HIGH RESOLUTION MORPHOLOGIES AND COLORS IN DISTANT RADIO GALAXIES "M.Dickinson coI None are directly related to this proposal. No results have yet been published. ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). Sun workstations at JPL, U of Toronto, and UC Berkeley. However we expect to need one additional SPARCstation LX and 1GB disk drive and have budgeted 50% of this cost to STScI, with the remainder coming from JPL funds. Op We have IRAF/SDAS installed and have developed numerous software routines relevant to the data reduction and analysis which we will apply (see Section 7.) ------------------------------------------------------------------------------------ 11. Address Information Name: Peter R Eisenhardt Category: PI Institution: 2370 Address: MS 169-327 Jet Propulsion Laboratory 4800 Oak Grove Drive City: Pasadena State: CA Zip Code: 91109 Country: USA Telephone: 818-354-4395 Telex (or e-mail): prme@kromos.jpl.nasa.gov ------------------------------------------------------------------------------------ Name: Category: CON Institution: Address: City: State: Zip Code: Country: Telephone: Telex (or e-mail): ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 5758 [ 5] ------------------------------------------------------------------------------------------------------------------------------------ 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 B20902+34 E,315,322,325 RA = 9H 2M 24.80S +/- 0.03S, 1950 Z = 1 R=28.5 DEC = +34D 19' 57.0" +/- 3.395 2 F-LINE(5342)=30 +/- 5 E-18 0.3" Comments: OBSERVED R AND 5342 FLUXES 100 TIMES LARGER BUT EXTENDED OVER SEVERAL ARCSEC. GOAL IS S/N=5 ON UNRESOLVED STRUCTURES WITH 1% OF OBSERVED TOTAL FLUXES. OUR GROUNDBASED IMAGES SHOW MUCH SUBSTRUCTURE IN THIS OBJECT. ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5758 [ 6] ------------------------------------------------------------------------------------------------------------------------------------ 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 ------------------------------------------------------------------------------------------------------------------------------------ 4 B20902+34 WFPC2 IMAGE LRF LRF 5341 CR-SPLIT=NO 4 2200.00 5 2 1 GROUP 4-6 NO GAP 18000S POS TARG +0.00, +0.10 CYCLE 4 / 4-6 Comments: ADJUST EXP TIME +INFINITY/-10% TO FIT IN AN ALIGNMENT. 3 EXP/ POS FOR CR DETECTION, UNINTERRUPTED EXPOSURES NEEDED TO ACHIEVE DESIRED S/N. POS TARG SEQUENCE WITH INTEGER PIXEL SHIFTS TO AVOID PATTERN NOISE. ------------------------------------------------------------------------------------------------------------------------------------ 5 B20902+34 WFPC2 IMAGE LRF LRF 5341 CR-SPLIT=NO 3 2200.00 5 2 1 POS TARG -0.200, - 18000S 0.100 Comments: ADJUST EXP TIME +INFINITY/-10% TO FIT IN AN ALIGNMENT. SECOND POS TO AVOID PATTERN NOISE. FOR ALL 3 POS USE SAME OPTIMUM CENTER BUT NOTE THAT POS TARG REQT DOES NOT IMPLY A NEED FOR ABSOLUTE POINTING ACCURACY < 1" ------------------------------------------------------------------------------------------------------------------------------------ 6 B20902+34 WFPC2 IMAGE LRF LRF 5341 CR-SPLIT=NO 3 2200.00 5 2 1 POS TARG +0.100, - 18000S 0.200 Comments: ADJUST EXP TIME +INFINITY/-10% TO FIT IN AN ALIGNMENT. THIRD POS TO AVOID BLEMISHES ALWAYS USE +15 DEG SOFA ROT. ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 5758 [ 7] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 14.01 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category GALAXIES & CLUSTERS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category DISTANT GALAXIES ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements GROUP 4-6 NO GAP; POS TARG +0.00, +0.10; CYCLE 4 / 4-6; POS TARG -0.200, -0.100 POS TARG +0.100, -0.200 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements LRF ------------------------------------------------------------------------------------------------------------------------------------ Target Names B20902+34 ------------------------------------------------------------------------------------------------------------------------------------