Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 5308 Report Date: 18-Jul-95:17:07 Version: ********** Check-in Date: ********** 1.Proposal Title: HIGH RESOLUTION PC IMAGING OF A Z=2.4 GALAXY CYCLE4MEDIUM THE DEVELOPMENT OF R^1/4 LIGHT-PROFILES IN A YOUNG WEAK RADIO GALAXY ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID GALAXIES & CLUSTERS GO 1 Long Term yrs Sub Category EVOLUTION/COSMOLOGY ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Rogier A. Windhorst 1220 USA 1 602 965 7143 ------------------------------------------------------------------------------------ 7. Abstract We propose 12.0 hours with PC in F606W and F814W to image the best available candidate for a compact young elliptical galaxy that is apparently just finishing its initial collapse at z=2.390. Ground-based spectroscopy and 9-band spectrophotometry constrain its stellar population age to ~0.3 Gyr. Deep Cycle 1 WFC I-band images show a deVaucouleurs profile, and suggests that both its dynamical and stellar population age are ~<0.5 Gyr. These images are limited by the Cycle-1 PSF. The proposed Cycle 4 PC images will provide the crucial higher resolution and better PSF to resolve the following questions: (1) What is the sub-kpc morphology and surface brightness-distribution of this young elliptical galaxy candidate at z=2.4\? Did it already completely develop an r^1/4-profile in both filters\? Or is it still clumpy at scales ~360 pc\? (2) Does a young galaxy at z=2.4 have significant color gradients at (sub-)kpc scales\? How does this constrain its stellar population and halo collapse that is apparently in progress at z=2.4\? Do any subclumps have different ages\? (3) Does its weak AGN indeed contribute <20% of the total galaxy light\? (4) What is the nature of foreground galaxies (a serendipitous gE at z=0.469), and surrounding galaxies, possibly a forming group or proto-cluster at z=2.4\? ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 16.03 par: 0 10. Num targs pri: 1 par: 1 ------------------------------------------------------------------------------------ 11. Instruments requested: WF/PC ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 5308 PI: Rogier A. Windhorst Proposal Title: HIGH RESOLUTION PC IMAGING OF A Z=2.4 GALAXY CYCLE4MEDIUM THE DEVELOPMENT OF R^1/4 LIGHT-PROFILES IN A YOUNG WEAK RADIO GALAXY ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Rogier A. Windhorst 1220, ARIZONA STATE UNIV., DEPT. USA OF PHYSICS AND ASTRONOMY Steve Mutz 1220, ARIZONA STATE UNIV., DEPT. USA OF PHYSICS AND ASTRONOMY Paul Schmidtke 1220, ARIZONA STATE UNIV., DEPT. USA OF PHYSICS AND ASTRONOMY William Keel 1090, UNIV. OF ALABAMA, PHYSICS USA AND ASTR., TUSCALOOSA ------------------------------------------------------------------------------------ 3. Description of proposed observations. In order to ensure an optimal scientific return of the WFPC data, we adopt the following observing strategy: 1) Our experience with high resolution mapping from the ground -- both at radio and optical wavelengths -- has shown that an AVERAGE signal-to-noise of 10 is an absolute minimum to distinguish high and low surface brightness structures, to make morphological classifications, and to do surface photometry. The galaxy 53W002 will have S/N>100 in the center (and much higher in the central AGN pixel, but not saturated). We must achieve at least S/N=1 per 0.046" pixel in the outermost ring at r=25 pix=1.2". Our WFPC2 simulations described in section 4 show that this can be accomplished with 5-6 hour exposures per filter, each consisting of 7-9 2400 sec orbits. 2) We need high resolution images in at least two passbands in order to study color gradients and get a handle on internal reddening. We will use the widest possible filters with the highest QxT: F606W and F814W. These two filters cover the highest QE-part of the WFPC2 chips, without major wavelength gaps or overlap: 5350-6850 A and 7280-8810 A as measured at their half power points, respectively. These are quite similar to the F and N filters of the ground based photographic system and transform rather easily to Johnson V and I or Gunn gri (see W91). This will be crucial in our comparison of HST surface brightness in F606W and F814W to the Cycle 1 F555W and F785LP fluxes, and to the well-known ground-based "total flux" in V and I. The photometric WFPC filters are too narrow and would take too much time. Since 53W002's V-surface brightness is expected to be lowest (see Fig. 2), we need also 90 min with WF3 in F606W to get ~2x better sky-noise per arcsec^-2, and push the V-profiles to beyond r=25 pix. Page 3 ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. We must image spatial scales <0.5 kpc to study the nucleus and light-profiles of this young galaxy at z=2.39. Hence we need the PC pixel scale of 0.046" (<360 pc for Ho>50 and qo=0.5). We cannot achieve this resolution from the ground because of atmospheric seeing, no matter how good the site. Although one could conceivably do better than 0.4" for brief time periods with ground-based image stabilization systems, it will be impossible to reach the required 0.05" FWHM from the ground. Without the PC resolution, we will not be able to understand the sub-kpc structure of these very high redshift ellipticals-to-be. The lower sky- background at HST's altitude is also a big advantage compared to the ground. In Cycle 1, we measured the following sky-brightness at the NEP: 23.30+/-0.2 mag/arcsec^2 in V and 22.30+/-0.2 in I (W92a). THIS PROJECT THUS MAKES OPTIMAL USE OF HST. During the last 10 years, we have done from the ground what we could to define our LBDS sample, using the world's largest radio and optical telescopes, but for this high resolution imaging project we need HST/PC. Compared to WFPC-1, the WFPC2+F785LP filter is ~1.0 mag down in sensitivity, and the V sensitivity is down by about0.6 mag. Because the F606W and F814 filters are considerably wider (although not overlapping) and a bit further to the red, they have 0.35-0.4 mag better throughput and lower sky background, which is imperative to make up for the lost QxT in WFPC2. The somewhat shorter baseline in F606W- F814W color of WFPC-2 compared to the canonical F555W-F791W color of WFPC-1 is thus more than made up for by the higher S/N in both F606W and F814W. Our morphological study requires an AVERAGE S/N of at least 10 per pixel in each independent elliptical pixel-ring out to a radius of 25 pixels. Given the relative colors and surface brightnesses of object and sky, this can actually be reached for 4.7 hours in F814W (7 orbits) and 6.0 hours in F606W. The F606W exposure will provide -- when properly resampled and stacked with the PC exposure -- ~2x better surface brightness sensitivity than the PC exposure alone -- and is thus needed to push the V-profile out to r_e>1.2" (25pix). The object is in the Hercules field, which is only 16 degrees from the NEP and close to HST's continuous viewing zone. If all the requested time is granted and observed successively, only one acquisition would be needed, during which the the two- filter exposures could be done. The 7-9 successive orbits give us a sufficient number of independent exposures to do careful CR-filtering, even with the steep slope of the CR-counts in space (which goes as N(mag)= c mag^0.6). The total observing time requested is 12.0 hours with minimal overhead. The efficiency is thus very high: 12.0/16.03=75%. ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. We need 2x5 full-orbit exposures (2150-2175 sec) in the R(F606W)+I(F814W) filters with the object 53W002 at two positions A and B about 3.903" apart in the most sensitive PC1 area. These are in CCD (NOT POS TARG) coordinates at: CCD_XY of POS_A=(340,365), POS_B=(280,305). These are thus 2.760" (or 60.0 PC1-pixels) apart in both CCD X and Y, and at a quadratic distance of 2.760*SQRT(2)=3.9032". I strongly desire to expose 53W002 on POS_A AND POS_B AT THE SAME ORIENT IN EACH FILTER. However, I like, but DO NOT NEED TO HAVE BOTH FILTERS AT THE SAME ORIENT. I DO NOT WANT BOTH FILTERS AT THE SAME ORIENT IF THAT PREVENTS YOU FROM SCHEDULING. Exposure times may be adjusted from 2150-2175 sec to fit into one orbit, as long as they do not get smaller than about 2000-2200 sec (unless you are willing to give me 6 orbits of 1800 sec for each POS and each filter). We also need 1x2 2150sec exposures in the R filter alone at the most sensitive WF3 spot at CCD (NOT POS TARG) coordinates CCD_XY=(295,320). Avoid the bad WF3 spot at XY=(319,303). 53W002 is a faint (V=23 mag) galaxy with a weak variable central AGN THAT WE CAN ABSOLUTELY NOT TOLERATE ON A CCD-DEFECT. I prefer if you schedule ALL as follows, but NOT if this prevents scheduling: REQ4 SEQ 1-5 NO GAP VERY IMPORTANT: Call Rogier Windhorst at 602 965 7143 or 602 965 3561 or at 410 516 4194 before scheduling. Thank you very much. Page 4 ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. ------------------------------------------------------------------------------------ 8. Additional comments or special requests. ------------------------------------------------------------------------------------ 9. Description of previous HST work. HST program numbers P2405,P3545: Windhorst (PI) ,Keel (Co-PI), et al. This Cycle 1 project is scientifically related in that it performed WFC and FOC imaging in Cycle 1 on three LBDS radio galaxies at z=0.3-2.4, and FOS spectroscopy and WFC or FOS parallel imaging on 7 weak radio galaxies with z=0.1- 0.6 in Cycle 2. The end result will be homogeneous FOS spectroscopy and WFC imaging for 10 weak radio galaxies out to z-0.6 by the end of Cycle 2. These Cycle 1+2 projects will have done the essential preparation for this project. P3917: Windhorst (Co-PI; Griffiths PI). The HST Medium Deep Survey (MDS) images several dozen random fields per year at high Galactic Latitude using HST/WFPC or FOC in parallel mode to get high-resolution images of faint field galaxies. This project is complementary to Windhorst's weak radio galaxy project in that it provides high-resolution images of field galaxies (the surface density of radio sources is not high enough to be effectively covered by the MDS). The data reduction and deconvolution techniques are similar between the two surveys. Super sky-flats, bad pixel maps, and deconvolution algorithms are constantly being exchanged. The MDS has been operational for about a year now, and first results are described by, e.g., Griffiths, et al (1993a, 199b, 1993c, and Windhorst et al 1993). The main findings are that the deconvolved scale lengths of V=18-24 mag field galaxies are rather small (~0.3-0.5"). At ASU, Windhorst runs the two projects separately, and has two small groups of students involved in each project. ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). a) MANPOWER: At ASU, two graduate students are available to work with the PI on this project, together with a half-time programmer. The other Co-I's in our team will also work with their graduate students on this project. b) COMPUTERS: Windhorst has dedicated microVAX and two DEC5000 workstations at ASU with image display systems and 2 Gbytes of diskspace. In addition, ASU has a supercomputer network on campus available for the CPU-intensive image deconvolution algorithms, if needed. Keel has access to IRAF, STSDAS, and additional analysis software on VAX, SUN and SGI workstations, plus the CRAY of the Alamaba Supercomputer Network. c) SOFTWARE: Our group has considerable experience in direct and spectroscopic CCD data reduction and has all the necessary software (STSDAS, IRAF, MIDAS, CASSANDRA, various deconvolution algorithms) in-house to calibrate and further reduce the HST data as well as to perform the scientific analysis. Specifically, we extensively tested and optimized the multi-resolution photon- preserving deconvolution algorithm, and various other algorithms to deconvolve direct HST images. If needed, we will apply these to the WFPC2 data, as well as our galaxy modeling software to extend the radial range over which the parameter space in light-profiles can be explored. d) GROUND-BASED TELESCOPES: Windhorst has access to Steward Observatory, Mount Hopkins, and soon also the 6.5 meter MMT upgrade. e) REDUCTION AND INTERPRETATION OF THE DATA: Windhorst (PI) and Keel (Co-PI) will be responsible for the Pipeline data reduction (direct and spectroscopic), image deconvolution and analysis as well as the combined direct- spectroscopic data interpretation. All collaborators will be involved in various stages of the data reduction process. According to expertise, Windhorst and Keel will CR-filter, stack, and, if needed in Cycle 4, photometrically deconvolve all images and measure galaxy light-profiles. ------------------------------------------------------------------------------------ 11. Address Information Page 5 Name: Rogier A. Windhorst Category: PI Institution: 1220 Address: Department of Physics and Astronomy, Arizona State Tempe, AZ 85287-1504, USA City: Tempe State: AZ Zip Code: 852871504 Country: USA Telephone: 1 602 965 7143/3561 Telex (or e-mail): 1 602 965 7954 E_MAIL:"RAW@COSMOS.LA.ASU. ------------------------------------------------------------------------------------ Name: Category: CON Institution: Address: City: State: Zip Code: Country: Telephone: Telex (or e-mail): ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 5308 [ 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 53W002 E, RA = 17H 12M 59.860S +/- 1950.0 Z = BKG 1 R = 22.45 +/- 0.15 315,322,325 0.3", 2.390 2 SURF(R) = 24.3 +/- 0.5 DEC = +50D 18' 51.30" +/- 3 I = 22.0 +/- 0.10 0.3" 4 SURF(I) = 23.9 +/- 0.5 5 U = 23.1 +/- 0.10 6 SURF(U) = 25.0 +/- 0.5 7 V = 22.8 +/- 0.15 8 SURF(R) = 24.7 +/- 0.15 Comments: WE NEED 2X5 EXP IN THE R+I FILTERS WITH 53W002 ON TWO POSTNS: A,B 3.9" APART IN THE MOST SENSITIV PC1 AREA ALSO NEED 1X2 EXP IN R AT THE MOST SENSITIVE WF3 SPOT CCD_XY=(295,320) AVOID BAD WF3 SPOT AT XY=(319,303). ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5308 [ 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 53W002 WFPC2 IMAGE PC1-FIX F606W 5957 SUM=1X1 6 1700S 10 1 1 CYCLE 4 / 1-5 READ=YES 2100S POS TARG -1.61,- CR-SPLIT=NO 1.82 CR- SEQ 1-5 WITHIN 14D TOLERANCE=0.1 SAME ORIENT FOR 2- CLOCKS=NO 5 AS 1 Comments: EXPOSE 53W002 ON POS_A AND ATD-GAIN=7 DARK TIME / 1-5 POS_B AT SAME ORIENT IN EACH FILTER. CCD_XY OF POS_A=(340, 365), POS_B=(280,305), 3.90" APART. I LIKE, BUT DON'T NEED TO HAVE BOTH FILTERS AT SAME ORIENT. CALL 602 965 7143 OR 410 516 4194. ------------------------------------------------------------------------------------------------------------------------------------ 2 53W002 WFPC2 IMAGE PC1-FIX F606W 5957 SUM=1X1 6 1700S 10 1 1 POS TARG -2.76,- READ=YES 2100S 1.61 CR-SPLIT=NO CR- TOLERANCE=0.1 CLOCKS=NO Comments: EXPOSE 53W002 ON POS_A AND ATD-GAIN=7 POS_B AT SAME ORIENT IN EACH FILTER. CCD_XY OF POS_A=(340, 365), POS_B=(280,305), 3.90" APART. I LIKE, BUT DON'T NEED TO HAVE BOTH FILTERS AT SAME ORIENT. CALL 602 965 7143 OR 410 516 4194. ------------------------------------------------------------------------------------------------------------------------------------ 3 53W002 WFPC2 IMAGE PC1-FIX F814W 7940 SUM=1X1 6 1700S 10 3 1 POS TARG -1.61,- READ=YES 2100S 1.82 CR-SPLIT=NO CR- TOLERANCE=0.1 CLOCKS=NO Comments: EXPOSE 53W002 ON POS_A AND ATD-GAIN=7 POS_B AT SAME ORIENT IN EACH FILTER. CCD_XY OF POS_A=(340, 365), POS_B=(280,305), 3.90" APART. I LIKE, BUT DON'T NEED TO HAVE BOTH FILTERS AT SAME ORIENT. CALL 602 965 7143 OR 410 516 4194. ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5308 [ 8] ------------------------------------------------------------------------------------------------------------------------------------ 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 53W002 WFPC2 IMAGE PC1-FIX F814W 7940 SUM=1X1 6 1700S 10 3 1 POS TARG -2.76,- READ=YES 2100S 1.61 CR-SPLIT=NO CR- TOLERANCE=0.1 CLOCKS=NO Comments: EXPOSE 53W002 ON POS_A AND ATD-GAIN=7 POS_B AT SAME ORIENT IN EACH FILTER. CCD_XY OF POS_A=(340, 365), POS_B=(280,305), 3.90" APART. I LIKE, BUT DON'T NEED TO HAVE BOTH FILTERS AT SAME ORIENT. CALL 602 965 7143 OR 410 516 4194. ------------------------------------------------------------------------------------------------------------------------------------ 5 53W002 WFPC2 IMAGE WF3-FIX F606W 5957 SUM=1X1 4 1700S 10 7 2 POS TARG +4.15, READ=YES 1800S +3.45 CR-SPLIT=NO CR- TOLERANCE=0.1 CLOCKS=NO Comments: NEED 53002 AT MOST SENSITIVE ATD-GAIN=7 WF3 SPOT ON CCD_XY=(295,320). AVOID BAD SPOT ON CCD_XY=(319, 303). ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 5308 [ 9] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SUM READ CR-SPLIT CR-TOLERANCE CLOCKS ATD-GAIN ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 16.03 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category GALAXIES & CLUSTERS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category EVOLUTION/COSMOLOGY ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CYCLE 4 / 1-5; POS TARG -1.61,-1.82; SEQ 1-5 WITHIN 14D; SAME ORIENT FOR 2-5 AS 1; DARK TIME / 1-5; POS TARG -2.76,-1.61; POS TARG +4.15,+3.45; ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names 53W002 ------------------------------------------------------------------------------------------------------------------------------------