6812( 11) - 04/02/97 15:09 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6812 Version: 11 Check-in Date: 02-Apr-1997 14:11:55 1.Proposal Title: The Nature of Very Red Field Galaxies ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle COSMOLOGY GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: RICHARD ELSTON UNIVERSITY OF FLORIDA CoI: Peter Eisenhardt Jet Propulsion Laboratory N CoI: Adam Stanford Institute of Geophysics and Planetary N Physics ------------------------------------------------------------------------------------ 6. Abstract Near-IR selection is ideal for the study of distant galaxy evolution because it minimizes bias toward finding strongly evolving or star forming galaxies. We have just completed a large area (100 arcmin^2) deep near--IR survey detecting galaxies to K~ 22. We have estimated ``photometric redshifts'' for a sample of galaxies with accurate photometry and K<20 to identify the progenitors of early type galaxies at z > 1 by searching for objects with very red colors. A particulary interesting indicator of z > 1.5 galaxies is the J-K color which should be greater than 2. We find about 3 such galaxies per arcminute, which is similar to the total number of early type (E,S0 and Sa) L^* galaxies expected between 1 1 it would appear that most early type galaxies are already well formed by a redshift greater than 2 but that they do begin to have a substantial UV excess at z > 1.5. However, our color selection could be fooled by a population of very dusty galaxies or a population of red AGN. We want to obtain deep WFPC2 images in the F814W filter to study the morphology of these very red galaxies to test if these very distant galaxies already have the morphology of early type galaxies and are thus the progenitors of current day early type galaxies or if they are a distinct new population. If they are early type galaxies, we will use the Kormendy r_e--Mu_e relation to constrain their evolution and confirm their photometric redshifts. ------------------------------------------------------------------------------------ 6812( 11) - 04/02/97 15:09 - [ 2] Observations Description ------------------------ Our faintest red galaxies have I~ 24.5. Previous HST work by Driver et al. (1995, ApJ, 449, 23) and Dickinson (private communcations) have carried out morphological classification on such galaxies using HST images. We base our estimates of exposure times on our experience in working with these data. The F814W filter is the best choice. Even though its throughput is less than that of F606W and F702W, F814W provides the greatest sensitivity because of the very red colors of the galaxies. To provide a reasonable surface brightness profile of a z ~ 1.5 L^* galaxy (assuming no evolution) will require surface photometry at the Mu_I=25.4 mag arcsec^-2 isophote, taking into account (1+z)^4 surface brightness fading and k-corrections. A typical galaxy will be about 2 arcseconds in diameter at z = 1.5 at the Mu_I=25.4 mag arcsec^2 isophote. On the WFC the isophote will include about 50 pixels. Thus, to achieve an isophotal accuracy of 15\\\\\\\\%, which is needed to differentiate disk and r^frac14 surface brightness profiles, will require a 1 Sigma detection pixel^- 1. So an exposure time of about 24000 seconds will be needed. The average visibility for our targets is 54 minutes. Leaving time for guide star acquisitions and readouts, we will require 10 orbits per field. Cosmic-ray rejection is very good with ~5 exposures per field so we plan to dither the telescope every orbit to help with removal of bad pixels, CRs and to better sample with PSF with WFPC2 pixels. The exposures will provide accurate surface brightness profiles for the putative z~ 1.5 L^* galaxies, and basic morphological types for galaxies as faint as I~ 26. We choose our targets from our wide--field IR survey to be very red (R-K > 5 and J-K > 2) field galaxies brighter than K=20. For a statistical sample we need to observe 20--30 galaxies. Within two of the four survey fields we have identified two WFPC2-- size areas providing the largest number of very red objects per pointing. In the Lynx field one such area yields 14 objects, and in SA57 another area contains 16 objects. Thus we can obtain the necessary imaging for 30 objects in two pointings, yielding a total request of 20 orbits. Real Time Justification ----------------------- These HST observations will be of galaxies selected from a wide field Near-IR J and K band survey conducted using about 20 nights of KPNO 4m time. Additionally they use deep BRIz images collected on about 8 nights of KPNO 4m time. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 6812( 11) - 04/02/97 15:09 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 GAL- GALAXY RA=08H 48M 33.96S +/- 2000 V = 25.0+/-0.5 084835+44533 0.5S,DEC=44D 53' 52.2" +/- 1.0" B-V = 2.0+/-0.5 0 6812( 11) - 04/02/97 15:09 - [ 4] Visit: 01 Visit Requirements: ORIENT 94D TO 94D 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-084835+ WFPC2 IMAGE WFALL-F F814W CR-SPLIT=NO 1 2700 S POS TARG 0.0,0.0 445330 IX ------------------------------------------------------------------------------------------------------------------------------------ 2 GAL-084835+ WFPC2 IMAGE WFALL-F F814W CR-SPLIT=NO 1 2800 S POS TARG 0.0,0.0 445330 IX ------------------------------------------------------------------------------------------------------------------------------------ 3 GAL-084835+ WFPC2 IMAGE WFALL-F F814W CR-SPLIT=NO 1 2800 S POS TARG 0.0,0.0 445330 IX ------------------------------------------------------------------------------------------------------------------------------------ 4 GAL-084835+ WFPC2 IMAGE WFALL-F F814W CR-SPLIT=NO 1 2800 S POS TARG 0.0,0.0 445330 IX ------------------------------------------------------------------------------------------------------------------------------------ 5 GAL-084835+ WFPC2 IMAGE WFALL-F F814W CR-SPLIT=NO 1 2800 S POS TARG 0.0,0.0 445330 IX ------------------------------------------------------------------------------------------------------------------------------------ 6812( 11) - 04/02/97 15:09 - [ 5] Visit: 02 Visit Requirements: ORIENT 94D TO 94D On Hold Comments: Additional Comments: SAME ORIENT AS 01 Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 6 GAL-084835+ WFPC2 IMAGE WFALL-F F814W CR-SPLIT=NO 1 2700 S POS TARG 0.25,0.25 445330 IX ------------------------------------------------------------------------------------------------------------------------------------ 7 GAL-084835+ WFPC2 IMAGE WFALL-F F814W CR-SPLIT=NO 1 2800 S POS TARG 0.25,0.25 445330 IX ------------------------------------------------------------------------------------------------------------------------------------ 8 GAL-084835+ WFPC2 IMAGE WFALL-F F814W CR-SPLIT=NO 1 2800 S POS TARG 0.25,0.25 445330 IX ------------------------------------------------------------------------------------------------------------------------------------ 9 GAL-084835+ WFPC2 IMAGE WFALL-F F814W CR-SPLIT=NO 1 2800 S POS TARG 0.25,0.25 445330 IX ------------------------------------------------------------------------------------------------------------------------------------ 10 GAL-084835+ WFPC2 IMAGE WFALL-F F814W CR-SPLIT=NO 1 2800 S POS TARG 0.25,0.25 445330 IX ------------------------------------------------------------------------------------------------------------------------------------ 6812( 11) - 04/02/97 15:09 - [ 6] Summary Form for Proposal 6812 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category COSMOLOGY ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 94D TO 94D POS TARG 0.0,0.0 POS TARG 0.25,0.25 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names GAL-084835+445330 ------------------------------------------------------------------------------------------------------------------------------------