! Proposal 6503, submission 2 ! PI: Tony Tyson ! Received Thu Apr 10 13:40:37 EDT 1997 ! From: sleiman@stsci.edu ! Hubble Space Telescope Cycle 6 (1996) Phase II Proposal Template ! $Id: 6503,v 4.1 1997/04/10 17:45:23 pepsa Exp $ ! Hubble Space Telescope Cycle 6 (1996) Phase II Proposal Template ! $Id: 6503,v 4.1 1997/04/10 17:45:23 pepsa Exp $ ! ! Refer to the HST Phase II Proposal Instructions to fill this out ! ! Anything after a "!" is ignored, and may be deleted ! ! All keywords with multiple entries are comma delimited except the ! Visit_Requirements and Special_Requirements keywords which can be ! delimited with carriage returns or semi-colons, but not commas ! ! For help call your Program Coordinator: Sleiman ! Phone: 410-338-4753 , E-mail: sleiman@stsci.edu ! ! This partially completed template was generated from a Phase I proposal. ! Name of Phase I Proposal: archive-0303.tyson.prop ! Date generated: Fri Dec 22 18:13:10 EST 1995 ! Proposal_Information ! Section 4 Title: The Enigma Lens Q2345+007: Early Assembly of Dark Matter? Proposal_Category: GO Scientific_Category: COSMOLOGY Cycle: 6 Investigators PI_name: Tony Tyson PI_Institution: AT&T Bell Laboratories CoI_Name: Phil Fischer CoI_Institution: University of Michigan Contact: ! Y or N (designate at most one contact) CoI_Name: Ian Dell'Antonio CoI_Institution: AT&T Bell Laboratories Contact: ! Y or N (designate at most one contact) CoI_Name: Greg Kochanski CoI_Institution: AT&T Bell Laboratories Contact: ! Y or N (designate at most one contact) CoI_Name: Raja Guhathakurta CoI_Institution: Lick Observatory Contact: ! Y or N (designate at most one contact) CoI_Name: Marc Davis CoI_Institution: UC Berkeley Contact: ! Y or N (designate at most one contact) Abstract: ! Free format text (please update) We propose to carry out deep imaging with the WFPC2 of the double QSO Q2345+007. The current evidence suggests that this double QSO results from the gravitational lensing effects of a large compact mass at z = 1.49. If so, this early formation of compact structure is not compatible with many forms of dark matter. With the improved resolution of the HST we will be able to test the lensing hypothesis by a) measuring the morphologies and colors of the candidate cluster galaxies (including a previously identified galaxy projected 1.5"\ from the fainter QSO image image) and b) searching for statistical distortions among faint blue background galaxies. These new data will let us significantly improve our arc selection and ellipticity measurements, thus enabling construction of a reliable weak lensing mass map. Because this lens is at cosmological redshift, this will be a strong test of mass assembly scenarios and the nature of dark matter. Questions ! Free format text (please update) Observing_Description: We require surface photometry of faint arclets at ~29 B mag arcsec^-2. The problem is that the lens redshift is so high that the area density of arclets, compared with foreground faint galaxies, is down by factors of 3-5 from lenses at low redshift. We will do 2 color imaging with WFPC2, obtaining other colors from our ground-based data. The HST WFC2 filters best suited to do this are the F555W and F814W filters. HST MDS and other surveys find that there is a range of angular scale lengths for faint galaxies; in particular, there are many small (< 0.5"\ half light radius) galaxies, which require the resolution of HST. We need to see morphological details of the lensed galaxies at sufficiently high S/N and sufficiently far from the galaxy center that they can be classified and accurate ellipticities and position angles obtained. For a typical galaxy with half-light radius ~0.3 arcsec, this means achieving a 1-Sigma surface brightness sensitivity of ~27 in V. Our simulations show that for a typical faint (M~27) galaxy with true ellipticity e=0.3, we can measure the ellipticity with an uncertainty of ~0.06 and the position angle to ~15\deg. The faint blue galaxies which we wish to image have a spectrum in the optical similar to an F0 star (as expected from galaxy evolution models). We will image the faint blue cluster members at z=1.5 at B magnitudes of 24 - 27. The colors of the faint blue galaxies imply from Table 6.1 of the WFPC2 handbook an AB correction of 0.00 magnitudes at 540nm. The seeing-deconvolved CFHT data and the HST MDS data give a mean half-light radius of 0.4" for galaxies around magnitude B=24--25 with at least 50\% scatter. We need to detect galaxies (arclets) with typical scale-lengths \rs~eq0.4" at least 2 scale-lengths out into the wings with a minimum S/N~simeq0.4 per pixel in order to accurately determine the shape parameters. From the WFPC2 exposure time calculator, we estimate that this will require 35200s exposure (16 orbits). We calculate signal-to-noise per pixel since we are doing surface photometry. However, ellipse fitting effectively averages pixels and increases the S/N, allowing for a ~3-Sigma detection. of the isophote at two scale radii. With this exposure, we will reach a 1-Sigma SB limit of 27.2 at F555W (which corresponds to 1.8e/pixel/2000s). Our Cycle 4 data on CL0024 (E. Turner, PI), which has faint arclets in addition to the famous bright arcs, suggest we may get a useful faint arclet inversion with 16 orbits in F555W. We will also spend 4 orbits (9000s) observing in F814W, in order to obtain integrated (not surface) photometry for the galaxies to a total magnitude limit of V ~ 27. We need this observation in order to get sufficiently accurate color data to distinguish galaxy types in the region close to the QSO images where the ground-based color data is compromised. This will allow us to push the arclet search much closer to the center of the lens. The QSO images will be modeled and subtracted using new software developed for this purpose on our ground-based data. We will combine the HST data with the best ground-based data (as a support function) using a modified Hook-Lucy algorithm, producing a very high resolution ultra-deep color image of the QSO vicinity. Real_Time_Justification: None Calibration_Justification: \n bullet Ground-based spectroscopy: We intend to pursue Keck spectroscopy of the brighter faint blue objects near the QSO position (the cluster candidates and the brighter arc candidates). We will take advantage of the a priori knowledge of accurate coordinates of the HST galaxy cores from WFPC2 astrometry using the measured on-orbit astrometric transformation coefficients. Because the median scale-length of HST galaxies is 0.3--0.4", we can use 0.5-- 0.75" slits in good seeing to optimize the multi-slit spectrograph through-put. Candidate high-z ellipticals, found from UBVRIK protometry (see below), will be followed up with Keck LRIS spectroscopy to confirm if they do indeed reside in a z=1.5 cluster. \n bullet Ground-based UBRIK imaging: We have the deepest ground-based imaging on this field: 31\ mag\ arcsec^-2 in B and 30\ mag\ arcsec^-2 in R. We will use these data for additional color information on these faint galaxies and arclets, forming a rough redshift indicator. We will optimally combine the HST WFC2 images with the ground- based imaging in areas not compromised by scattered QSO light, providing good S/N at all spatial frequencies 0.1--- 1.0", using a Lucy-Hook variant. Combined with UBVRIK multi- color photometry from HST and the ground (4m, WIYN, CFHT and Keck) this will allow us to study the weak lensing (and any strong lensing arcs), leading to an understanding of the mass distribution in this early overdensity. The HST V & I data are crucial for identifying very red galaxies in the vicinity of 2345+007, and these will be complemented by deep Keck J data in the near future. Relatively red V-I and very red I-J colors are expected for high redshift cluster ellipticals; we will isolate such galaxies in the z=1.5 cluster that is likely the primary lens in the foreground of the QSO pair. \n bullet Long-Term Ground-based monitoring: We have been granted queue observing time with the WIYN to continue a 12 year old monitoring program of this QSO to determine the timing delay (see Fig. 1 of Fischer Etal 1995 - ``Dark Matter'' AIP conference proceedings 336, p342) We are now sampling the 2345+007 field in Bj and R several times per season to 25th magnitude. Additional_Comments: Fixed_Targets ! Section 5.1 Target_Number: 1 Target_Name: 2345+007 Alternate_Names: Q2345+007B Description: CLUSTER OF GALAXIES, Gravitational lens, High Redshift Cluster Position: RA=23H 48M 18.70S +/- 0.03S, DEC=00D 57' 16.7" +/- 0.5" Equinox: J2000 RV_or_Z: Z = 2 ! Estimated redshift of background galaxies RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch: Annual_Parallax: Flux: SURF(V) = 25 +/- 4 ! Include at least V and B-V B-V = 0 Comments: Both galaxies in the foreground cluster at z=1.49 as well as background galaxies. All are very blue. Chip 3 centered on qso-bm which has V=21.0 and is at z=2.15 Target_Number: 2 Target_Name: 2345+007x Alternate_Names: Q2345+007B Description: CLUSTER OF GALAXIES, Gravitational lens, High Redshift Cluster Position: RA=23H 48M 18.70S +/- 0.03S, DEC=00D 57' 21.9" +/- 0.5" Equinox: J2000 RV_or_Z: Z = 2 ! Estimated redshift of background galaxies RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch: Annual_Parallax: Flux: SURF(V) = 25 +/- 4 ! Include at least V and B-V B-V = 0 Comments: Both galaxies in the foreground cluster at z=1.49 as well as background galaxies. All are very blue. Chip 3 centered on qso-bm which has V=21.0 and is at z=2.15 Target_Number: 3 Target_Name: 2345+007y Alternate_Names: Q2345+007B Description: CLUSTER OF GALAXIES, Gravitational lens, High Redshift Cluster Position: RA=23H 48M 18.79S +/- 0.03S, DEC=00D 57' 24.8" +/- 0.5" Equinox: J2000 RV_or_Z: Z = 2 ! Estimated redshift of background galaxies RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch: Annual_Parallax: Flux: SURF(V) = 25 +/- 4 ! Include at least V and B-V B-V = 0 Comments: Both galaxies in the foreground cluster at z=1.49 as well as background galaxies. All are very blue. Chip 3 centered on qso-bm which has V=21.0 and is at z=2.15 Solar_System_Targets ! Section 5.2 Generic_Targets ! Section 5.3 Scan_Data ! Appendix B Visits ! Section 6 Visit_Number: 1 Visit_Requirements: ! Section 7.1 ORIENT 56D TO 56D !NO SOL'N OUTSIDE THIS RANGE ! Uncomment or copy visit level special requirements needed ! Most of these requirements (including ORIENT) will limit scheduling ! PCS MODE [Fine | Gyro] ! GUIDing TOLerance ! DROP TO GYRO IF NECESSARY [NO REACQuisition] ! ORIENTation TO ! ORIENTation TO FROM ! ORIENTation TO FROM NOMINAL ! SAME ORIENTation AS On_Hold_Comments: Visit_Comments: Exposure_Number: 1 ! Section 6.5 Target_Name: 2345+007 Config: WFPC2 Opmode: IMAGE Aperture: WF3-FIX Sp_Element: F555W Wavelength: Optional_Parameters: CR-SPLIT=NO Number_of_Iterations: 1 Time_Per_Exposure: 1100S Special_Requirements: ! Section 7.2 LOW-SKY MAX DUR 140% ! Uncomment or copy exposure level special requirements needed ! ONBOARD ACQuisition FOR ! SAVE OFFSET ! USE OFFSET ! POSition TARGet , ! SAME POSition AS ! RT ANALYSIS [FOR ] ! END ORBIT ! LOW-SKY ! MAXimum DURation [