8193( 4) - 01/03/00 09:30 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8193 Version: 4 Check-in Date: 03-Jan-2000 09:28:47 1.Proposal Title: Comparing the Hosts of High-z Radio-Quiet Quasars to Lyman Break Galaxies ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 8 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Timothy Heckman The Johns Hopkins University CoI: Dr. Susan Ridgway The Johns Hopkins University N CoI: Dr. Daniela Calzetti Space Telescope Science Institute N CoI: Dr. Matthew Lehnert Leiden Observatory N ------------------------------------------------------------------------------------ 5. Abstract The underlying causes of the rapid cosmological evolution of the quasar population are a mystery around which are woven many different strands of contemporary cosmology. Progress on this problem would have important implications for understanding the early heating of the IGM, the formation and early evolution of galaxies, and of course the quasar phenomenon itself. We have begun a program with HST to image the host galaxies of a carefully-selected sample of five high- z (z ~ 2 to 3) radio-quiet quasars in order to compare the photometric and structural properties of the host galaxies to those of the field population of normal star- forming galaxies at similar redshifts (the `Lyman break' galaxies). We have already obtained deep H-band NICMOS (rest-frame visible) images of this sample, and find that the host galaxies are similar to the Lyman break galaxies in terms of their compact sizes and moderate luminosities. In the present proposal we request time to obtain WFPC2 images in order to extend this comparison into the crucial rest-UV spectral window, where the young stellar population can be most directly probed. This information is essential to begin to understand the long- hypothesized relationship between quasars and galaxy-building in the early universe. We emphasize that if the quasar host galaxies have UV sizes and luminosities similar to typical Lyman break galaxies, we will be able to detect them. ------------------------------------------------------------------------------------ 8193( 4) - 01/03/00 09:30 - [ 2] Observations Description ------------------------ As stated above, our observational goal is to use WFPC2 to detect host galaxies having the same (rest-frame) UV luminosities and sizes as the field population of UV-selected galaxies at comparable redshifts (the Lyman break galaxies). To do so, we request 4 orbits each for the two quasars in our sample at z ~ 2.7, 2 orbits each for the three quasars at z ~ 1.8, and one orbit to image a PSF star (15 orbits in total). We note that our targets are all at the extreme edge of the CVZ (11 to 15 total orbits per field over 12 months) and therefore we do not request using CVZ time. As we show below, for host galaxies with sizes and brightnesses similar to the Lyman break galaxies, both the ability to accurately subtract the quasar light and the sensitivity of the images are important limitations. Our observational strategy is as therefore follows: 1) Use the Planetary Camera because it is important to adequately sample the PSF. 2) Select the F606W filter because of its excellent sensitivity and because there is an adequate library of archival PSF stars that can be used to quantify the repeatibility (both temporally and spatially) of the PSF (see Wiggs et al 1997). 3) Request that the observations of each quasar be split into two visits separated by several months, so that the quasar will be imaged at two different roll angles. Thus, we will be able to distinguish between subtle PSF features (that will roll with the telescope and stay fixed in the detector coordinate system) and actual structures in the host galaxy (which will stay fixed in the sky coordinate system). 4) Dither the telescope in 2.5 pixel increments between exposures in a given visit. This both improves the spatial sampling and mitigates the effect of pixel-to-pixel variations in sensitivity. 5) Obtain sub -pixel-dithered observations of a PSF star that will placed on the same location on the PC as the quasars (at the center) and will be chosen to have the same blue (V-R) color as the quasars themselves. 6) Utilize several independent and complementary techniques to model the PSF, including the PSF star, TinyTim, and F606W PSF library stars. 7) Avoid placing the bright LyAlpha emission-line in the filter bandpass (accomplished with the F606W filter for our quasars). The z = 1.8 (2.7) quasars have the CIIILambda1909 (CIVLambda1549) lines in the F606W filter bandpass, but these lines are only 5 to 10\ LyAlpha in spatially-resolved nebulae associated with high-redshift AGN (McCarthy 1993; Heckman et al 1991). The light from our quasar hosts will thus be dominated by the UV continuum. Our aim is to get images whose sensitivity is adequate to detect typical Lyman break galaxies underlying the quasar. The Lyman break galaxy luminosity function (Dickinson 1998) can be adequately fit by a Schecter function with L_* = 3 * 10^44 erg s^-1. This luminosity is uncorrected for dust extinction, adjusted to H_0 = 75 and q_0 = 0.2, and represents nuP_Nu at a rest wavelength of 1500 Angstrom. Three of our quasars are at z ~ 1.8 and two are at z ~ 2.7. The predicted fluxes of an L_* Lyman break galaxy at a mean observed wavelength of 5935 Angstrom\ (F606W) are then 3.7 microJy at z = 1.8 and 1.2 microJy at z = 2.7. Typical half-light radii (r_e) of Lyman break galaxies range from 0.15 to 0.3 arcsec, so we take r_e = 0.22 arcsec. This results in total count rates of 9 s^-1 from the host (4.5 s^-1 inside r_e) for z = 1.8. For z = 2.7 the corresponding rates are 3 s^-1 from the host (1.5 s^-1 inside r_e). Summed over the 78 PC pixels inside r_e (0.22 arcsec), the sky background contributes 1.6 s^-1, the dark current contributes 0.3 s^-1, and the quasar will contribute about 18 s^-1. For the z = 2.7 (1.8) quasars, the total signal- to-noise for the host galaxy inside r_e would be 24 (45) for four (two) 1200 sec exposures (no CR-SPLIT) in two (one) orbits. Combining images at the two roll angles would then yield a signal-to-noise of about 34 (63). This means that we will have a signal-to-noise ratio of 15 for 4 (16) spatial sub-regions within r_e for the z = 2.7 (1.8) hosts. The z = 2.7 (1.8) host provides about 8\ the quasar in this region. Thus, in the z = 2.7 case, we need to be able to reliably subtract the quasar light at a level of a few percent. Our experience in modeling the HST+WFPC2 PSF as part of our analysis of `quasar fuzz' in other HST programs shows that is possible with care (see the contributions by Remy et al; Suchkov & Casertano; and Surdej et al; in `The 1997 HST Calibration Workshop' Eds. S. Casertano et al 1997). We will place the quasar at the center of the PC field and use a combination of TinyTim, our own PSF star, and library PSF stars that are both close to the same location on the PC as the quasar and which were obtained with a similar telescope focus position (see Suchkov & Casertano 1997). Because detection of the inner part of the host galaxy is challenging, we need to insure that we have adequate sensitivity to also detect the outer part of the host, where removing the contamination by quasar light is more tractable. In the 628 pixels in the annulus from 1 to 3 r_e (0.22 to 0.66 arcsec), we would detect 1.3 (4.0) s^-1 from the z = 2.7 (1.8) host galaxy, 1.4 s^-1 from the quasar, 12.6 s^-1 from the sky, and 2.5 s^-1 from the dark current. The signal-to- noise for the z = 2.7 (1.8) host galaxy summed over this annulus is then 16 (33) in four (two) 1200 sec exposures, or 24 (48) summed over both roll angles. We could thus divide the outer region of the z = 2.7 (1.8) host galaxy into 2 (9) separate spatial regions with a signal-to- noise of 15 in each. As noted above, our team has a considerable amount of experience in analyzing data of this kind. We have developed a number of techniques for estimating the amount of extended light around quasars. These techniques include unconstrained (using the data reducer's own judgement) and constrained (relying on specific quantitative fitting criteria) PSF subtraction (see Lehnert et al 1992; Ridgway & Stockton 1997). Specific techniques we have used (and will use on these new data) include: 1) comparing the one dimensional radial surface-brightness profiles of the quasar and PSF 2) fitting the one- dimensional radial surface-brightness profiles with a model consisting of a point source plus a galaxy (r^1/4-law or exponential disk), and 3) using a two- dimensional cross-correlation estimation technique (see Boyce et al 1993; Phillips & Davies 1991) that compares the 2-d structure of the quasar image with that of the PSF and a large series of galaxy models. The last of these appears to be especially robust and gives excellent agreement with simple iterative PSF subtraction but removes subjectivity or relying on less-robust goodness- of-fit criteria from the analysis. Our experience shows that standard Chi^2 or similar difference minimization methods are very sensitive to `defects' in the image (cosmic rays, charge transfer problems, scattered light, bad pixels, poorly flat-fielded pixels and data, etc) and not very sensitive to fitting the much lower signal-to-noise areas which is where much of the evidence for the quasar host lies. In general, our philosophy has been (and will be) to analyze the data with several independent techniques, as an empirical test of robustness. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 8193( 4) - 01/03/00 09:30 - [ 3] Data Distribution Paper Products: NO Media: ELECTRONIC Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 8193( 4) - 01/03/00 09:30 - [ 4] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 MZZ4935 GALAXY, QSO RA=03H 16M 36.25S +/- 0.1S, DEC= J2000 Z=1.876 B = 21.9 -55D 9' 32.22" +/- 1", PLATE- ID=039H Comments: Assuming alpha = 0.6, F(6000A)=8.92E-29 ergs/cm^2/sec/hz (R about 21.2) F(H) = 3.5 E-6 Jy from Nicmos 2 MZZ11408 Galaxy, QSO RA=03H 15M 34.10S +/- 0.1S, DEC= J2000 Z=1.735 B = 22.0 -55D 30' 4.83" +/- 1", PLATE- ID=039H Comments: F(H)=5.6E-6 Jy (from Nicmos) 3 MZZ1558 Galaxy, QSO RA=03H 14M 51.48S +/- 0.1S, DEC= J2000 Z=1.829 B = 21.64 -54D 57' 14.45" +/- 1", PLATE- ID=039H Comments: F(H) = 2.4E-5 Jy from Nicmos 4 MZZ9592 Galaxy, QSO RA=03H 14M 4.94S +/- 0.1S, DEC=- J2000 Z=2.710 B = 21.85 55D 20' 50.94" +/- 1", PLATE- ID=039H Comments: F(H) = 1.7E-5 Jy 5 MZZ9744 GALAXY, QSO RA=03H 13M 38.33S +/- 0.1S, DEC= J2000 Z=2.735 B = 21.87 -55D 21' 37" +/- 1", PLATE- ID=039H Comments: F(H) = 1.12E-5 Jy from Nicmos; gives alpha = 0.3 6 GS8496701 CALIBRATION, POINT RA=03H 16M 29.13S +/- 0.1S, DEC= J2000 B = 14.27 SPREAD FUNCTION -55D 11' 6.9" +/- 1", PLATE- H = 12.0+/-0.2 ID=039H Comments: PSF star of MZZ4935, B-H is about 2.3, therefore assume stellar type G5. (If G2, B-H= 2.07. If stellar type is K0, B-H=2.6. If stellar type is F0, B-H=1.06). 7 GS8495550 CALIBRATION, POINT RA=03H 13M 56.44S +/- 0.1S, DEC= J2000 B = 14.21 SPREAD FUNCTION -55D 21' 21.0" +/- 1", PLATE- H = 12.45+/-0.2 ID=039H Comments: PSF star of MZZ9592, from Nicmos B-H = 1.8. Assume stellar type around G0. (Stellar type G2, B-H=2.07 . If stellar type is K0, B-H=2.6. If stellar type is F0, B-H=1.06). 8 STAR-0315- CALIBRATION, POINT RA=03H 15M 33.38S +/- 0.1S, DEC= J2000 B = 16.97 5529 SPREAD FUNCTION -55D 29' 30.3" +/- 1", PLATE- ID=039H Comments: PSF star of MZZ11408; assume G5 for saturation avoidance 9 STAR-0314- CALIBRATION, POINT RA=03H 14M 54.43S +/- 0.1S, DEC= J2000 B = 15.74 5458 SPREAD FUNCTION -54D 58' 09.7" +/- 1", PLATE- ID=039H Comments: PSF star of MZZ1558 10 STAR-0313- CALIBRATION, POINT RA=03H 13M 44.95S +/- 0.1S, DEC= J2000 B = 14.53 5522 SPREAD FUNCTION -55D 22' 49.5" +/- 1", PLATE- ID=039H Comments: PSF star of MZZ9744 8193( 4) - 01/03/00 09:30 - [ 5] Visit: 01 Visit Priority: Visit Requirements: ORIENT 226D TO 72D On Hold Comments: Additional Comments: orient to avoid bright star in PC stray light region Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 MZZ4935 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 1 2500 S POS TARG 0, 0 ------------------------------------------------------------------------------------------------------------------------------------ 2 GS8496701 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 1 2 S SEQ 1-2 NON-INT POS TARG 0, 0 ------------------------------------------------------------------------------------------------------------------------------------ 3 MZZ4935 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 1 2500 S POS TARG 0.253, 0.506 ------------------------------------------------------------------------------------------------------------------------------------ 4 GS8496701 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 1 2 S SEQ 3-4 NON-INT POS TARG 0.253, 0.506 ------------------------------------------------------------------------------------------------------------------------------------ 5 MZZ4935 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 1 2500 S POS TARG -0.506,-0.253 ------------------------------------------------------------------------------------------------------------------------------------ 6 GS8496701 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 1 2 S SEQ 5-6 NON-INT POS TARG -0.506,-0.253 ------------------------------------------------------------------------------------------------------------------------------------ 8193( 4) - 01/03/00 09:30 - [ 6] Visit: 02 Visit Priority: Visit Requirements: 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 MZZ11408 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 1 2500 S POS TARG 0, 0 ------------------------------------------------------------------------------------------------------------------------------------ 2 STAR-0315-5 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 1 23 S SEQ 1-2 NON-INT POS TARG 529 0, 0 ------------------------------------------------------------------------------------------------------------------------------------ 3 MZZ11408 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 1 2600 S POS TARG 0.253, 0.506 ------------------------------------------------------------------------------------------------------------------------------------ 4 STAR-0315-5 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 1 23 S SEQ 3-4 NON-INT POS TARG 529 0.253, 0.506 ------------------------------------------------------------------------------------------------------------------------------------ 5 MZZ11408 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 1 2600 S POS TARG -0.506,-0.253 ------------------------------------------------------------------------------------------------------------------------------------ 6 STAR-0315-5 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 1 23 S SEQ 5-6 NON-INT POS TARG 529 -0.506,-0.253 ------------------------------------------------------------------------------------------------------------------------------------ 8193( 4) - 01/03/00 09:30 - [ 7] Visit: 03 Visit Priority: Visit Requirements: ORIENT 233D TO 80D On Hold Comments: Additional Comments: orient keeps brightish star out of PC stray light regions Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 MZZ1558 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 1 2500 S POS TARG 0, 0 ------------------------------------------------------------------------------------------------------------------------------------ 2 STAR-0314-5 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 1 10 S SEQ 1-2 NON-INT POS TARG 458 0, 0 ------------------------------------------------------------------------------------------------------------------------------------ 3 MZZ1558 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 1 2500 S POS TARG 0.253, 0.506 ------------------------------------------------------------------------------------------------------------------------------------ 4 STAR-0314-5 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 1 10 S SEQ 3-4 NON-INT POS TARG 458 0.253, 0.506 ------------------------------------------------------------------------------------------------------------------------------------ 5 MZZ1558 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 1 2500 S POS TARG -0.506,-0.253 ------------------------------------------------------------------------------------------------------------------------------------ 6 STAR-0314-5 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 1 10 S SEQ 5-6 NON-INT POS TARG 458 -0.506,-0.253 ------------------------------------------------------------------------------------------------------------------------------------ 8193( 4) - 01/03/00 09:30 - [ 8] Visit: 04 Visit Priority: Visit Requirements: ORIENT 304D TO 187D On Hold Comments: Additional Comments: orient keeps pair of bright stars from PC stray light regions Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 MZZ9592 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 1 2500 S POS TARG 0, 0 ------------------------------------------------------------------------------------------------------------------------------------ 2 GS8495550 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 1 3 S SEQ 1-2 NON-INT POS TARG 0, 0 ------------------------------------------------------------------------------------------------------------------------------------ 3 MZZ9592 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 1 2500 S POS TARG 0.253, 0.506 ------------------------------------------------------------------------------------------------------------------------------------ 4 GS8495550 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 1 3 S SEQ 3-4 NON-INT POS TARG 0.253, 0.506 ------------------------------------------------------------------------------------------------------------------------------------ 5 MZZ9592 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 1 2500 S POS TARG -0.506,-0.253 ------------------------------------------------------------------------------------------------------------------------------------ 6 GS8495550 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 1 3 S SEQ 5-6 NON-INT POS TARG -0.506,-0.253 ------------------------------------------------------------------------------------------------------------------------------------ 8193( 4) - 01/03/00 09:30 - [ 9] Visit: 05 Visit Priority: Visit Requirements: ORIENT 290D TO 124D ORIENT 161D TO 222D On Hold Comments: Additional Comments: Orient ranges to keep two bright stars out of PC stray light regions Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 MZZ9744 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 1 2500 S POS TARG 0, 0 ------------------------------------------------------------------------------------------------------------------------------------ 2 STAR-0313-5 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 1 3 S SEQ 1-2 NON-INT POS TARG 522 0, 0 ------------------------------------------------------------------------------------------------------------------------------------ 3 MZZ9744 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 1 2500 S POS TARG 0.253, 0.506 ------------------------------------------------------------------------------------------------------------------------------------ 4 STAR-0313-5 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 1 3 S SEQ 3-4 NON-INT POS TARG 522 0.253, 0.506 ------------------------------------------------------------------------------------------------------------------------------------ 5 MZZ9744 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 1 2500 S POS TARG -0.506,-0.253 ------------------------------------------------------------------------------------------------------------------------------------ 6 STAR-0313-5 WFPC2 IMAGE PC1 F606W CR-SPLIT=NO 1 3 S SEQ 5-6 NON-INT POS TARG 522 -0.506,-0.253 ------------------------------------------------------------------------------------------------------------------------------------ 8193( 4) - 01/03/00 09:30 - [ 10] Summary Form for Proposal 8193 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PC1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 226D TO 72D POS TARG 0, 0 SEQ 1-2 NON-INT POS TARG 0, 0 POS TARG 0.253, 0.506 SEQ 3-4 NON-INT POS TARG 0.253, 0.506 POS TARG -0.506,-0.253 SEQ 5-6 NON-INT POS TARG -0.506,-0.253 ORIENT 233D TO 80D ORIENT 304D TO 187D ORIENT 290D TO 124D ORIENT 161D TO 222D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W ------------------------------------------------------------------------------------------------------------------------------------ Target Names MZZ4935 GS8496701 MZZ11408 STAR-0315-5529 MZZ1558 STAR-0314-5458 MZZ9592 GS8495550 MZZ9744 STAR-0313-5522 ------------------------------------------------------------------------------------------------------------------------------------