8212( 3) - 02/15/99 11:42 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8212 Version: 3 Check-in Date: 15-Feb-1999 11:41:21 1.Proposal Title: Reconciling the SBF and SNIa Distance Scales ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 8 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Edward Ajhar National Optical Astronomy Observatories CoI: Prof. John L. Tonry University of Hawaii N CoI: Dr. Brian P. Schmidt Mount Stromlo & Siding Spring N Observatories CoI: Dr. John P. Blakeslee California Institute of Technology N ------------------------------------------------------------------------------------ 5. Abstract We propose to use WFPC2 to measure surface brightness fluctuation (SBF) distances to host galaxies of well-measured type Ia supernovae (SNIa) in order to resolve the discrepancy between H_0 values determined from SBF distances and from SNIa distances. Currently, SBF distances yield H_0 ~ 80 km/s/Mpc, and SNIa distances yield H_0 ~ 60. While both of these distance estimators provide excellent internal error consistency (near 5 percent), some still unknown systematic errors are preventing these methods from providing consistent values for the Hubble parameter. Given that there are so few reliable methods for determining distances over large ranges, it is imperative that we understand the discrepancy between the SBF and SNIa methods. Only then can these methods converge on the true value of H_0. ------------------------------------------------------------------------------------ 8212( 3) - 02/15/99 11:42 - [ 2] Observations Description ------------------------ We will measure distances to these galaxies by obtaining high signal-to-noise images and observing their surface brightness fluctuations (SBF), the irreducible mottling of an otherwise smooth galaxy from the finite number of stars. This has been described in detail in Tonry (1991) and Jacoby et al. (1992). The fundamental idea is simply that the finite number of stars in a galaxy gives rise to a measurable bumpiness in its surface brightness, even though individual stars remain completely unresolved. The variance is the product of the galaxy brightness per pixel and what we refer to as the ``average luminosity'' of the stellar population, the ratio of the second moment of the stellar luminosity function to the first: Lbar = Sigma n_i L_i^2 / Sigma n_i L_i. Obviously, there are many sources of pixel-to-pixel noise (variance) in an image of a galaxy such as detector noise and photon statistics, roughness from patchy dust obscuration, spiral arms, and inhomogeneous stellar po pulation, bumpiness from globular clusters (GCs) or background galaxies, and finally the SBF mottling from the Poisson statistics of the finite number of stars in a pixel. Photon shot noise only grows as the square root of time, and the SBF signal becomes detectable when a source of Lbar contributes more than one photon in an image (i.e., when stellar counting statistics dominate photon counting statistics). We apply the SBF method primarily to E and S0 galaxies, which avoids problems with dust and spiral arms. Unraveling the third source of variance proceeds in two steps. First, we identify as many ``compact sources'' (stars, background galaxies, and primarily GCs) as possible and excise them from the image. Second, we fit a luminosity function to the sources which we found and integrate the extrapolation to fainter magnitudes to determine the residual variance left in the image from the unseen sources. The variance from the SBF of stars in the galaxy is then the differ en ce between that which is measured and the estimate of the residual. The fainter we can identify and remove sources, the smaller the residual correction. In practice, if our compact source completeness dies out two magnitudes brighter than the peak of the GC luminosity function, the resulting SBF measurement is quite uncertain because most of the variance in the image results from the (uncertain) residual variance. If we can identify sources all the way to the peak of the GC luminosity function, the residual variance is typically only 20 percent of the net variance, and it contributes negligible uncertainty. Removal of compact sources makes it critical that the images be as sharp as possible. Measurement of SBF is accurate and reliable at the distance of Virgo (1400 km/s) in 1" seeing but becomes difficult in 1.5" seeing. At a distance of about 4500 km/s, even the best seeing from the ground (0.5") becomes inadequate. We believe that our attempts to observe SBF at dist an ces of about 2500 km/s from the ground have been successful, but we have reservations about reliability when the seeing was barely adequate (0.75"). However, with HST we can identify GCs significantly fainter than the peak of the luminosity function. Moreover, we now have substantial experience measuring SBF distances with WFPC2 (Ajhar et al. 1997) and had no difficulty measuring SBF distances to 5000 km/s in Cycle 5 (Lauer et al. 1998) and are confident that the proposed measurements will be practically routine for us. A common concern about deriving distances from SBF measurements is the extent to which we can predict the absolute magnitudes Mbar which correspond to the mbar which we measure. We have found empirically that stellar populations of differing age and metallicity vary predictably with overall color, and this has been confirmed theoretically (Worthey 1993). The empirical SBF calibration for WFPC2 of Ajhar et al. (1997) ties WFPC2 SBF distances to the ground- b ased distances of SBF-I, which in turn are tied to the HST Cepheid distances. In addition, we plan to refine the Ajhar et al. calibration by including additional galaxies recently observed by HST and now available in the HST archive. In order to achieve full 5 percent accuracy, it is essential that the SBF signal significantly exceed the photon/read noise. Because we will have extremely good compact source rejection, past WFPC2 observations as well as ground-based observations indicate that we can get by with only 5 photons per star of magnitude m_Ibar but much less than this will seriously compromise the accuracy of the measurement. Through WFPC2's F814W I filter, the exposure time t scales with distance D (in km/s) such that t = 9300 s (D/3000 km/s)^2, where we have used the Ajhar et al. (1997) SBF calibration for a galaxy with a typical color V-I = 1.25 and tied to the Hubble flow assuming H_0 = 75 km/s/Mpc. Allowing time for target acquisition and dithered exposures, ea ch orbit will provide about 2500--2900 s (4800 s for CVZ) of exposure time depending on the object's declination. We will obtain ground-based images to determine the V-I color of each galaxy. Real Time Justification ----------------------- None. Calibration Justification ------------------------- None. Additional Comments ------------------- ------------------------------------------------------------------------------------ 8212( 3) - 02/15/99 11:42 - [ 3] Data Distribution Paper Products: YES Media: DAT Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 8212( 3) - 02/15/99 11:42 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC2258 GALAXY, LENTICULAR RA=6H 47M 46.08S +/- 1", DEC=74D J2000 V = 3995 SURF(V) = 21.4+/-0.3 28' 56.35" +/- 1", PLATE-ID=01KS 2 NGC2962 GALAXY, LENTICULAR RA=9H 40M 53.94S +/- 1", DEC=5D J2000 V = 1967 SURF(V) = 21.4+/-0.3 9' 56.94" +/- 1", PLATE-ID=01G7 3 NGC5308 GALAXY, LENTICULAR RA=13H 47M 0.25S +/- 1", DEC=60D J2000 V = 2041 SURF(V) = 21.4+/-0.3 58' 22.30" +/- 1", PLATE-ID=01R0 4 NGC6495 GALAXY, ELLIPTICAL RA=17H 54M 50.76S +/- 1", J2000 V = 3127 SURF(V) = 21.4+/-0.3 DEC=18D 19' 37.01" +/- 1", PLATE -ID=01LT 5 ESO352-G57 GALAXY, LENTICULAR RA=1H 22M 2.21S +/- 1", DEC=-34D J2000 V = 5575 SURF(V) = 21.4+/-0.3 11' 49.07" +/- 1", PLATE-ID=047Y 8212( 3) - 02/15/99 11:42 - [ 5] Visit: 01 Visit Priority: Visit Requirements: GROUP 01, 02 WITHIN 2 D 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 ------------------------------------------------------------------------------------------------------------------------------------ 101 NGC2258 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1300 S POS TARG 0.0, 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 102 NGC2258 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1400 S POS TARG 0.8969, 0.0946 ------------------------------------------------------------------------------------------------------------------------------------ 103 NGC2258 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1300 S POS TARG 1.0010, 0.8908 ------------------------------------------------------------------------------------------------------------------------------------ 104 NGC2258 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1400 S POS TARG 0.1052, 0.9954 ------------------------------------------------------------------------------------------------------------------------------------ 105 NGC2258 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1300 S POS TARG -0.8903, 1.1006 ------------------------------------------------------------------------------------------------------------------------------------ 106 NGC2258 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1400 S POS TARG -0.9965,-0.0940 ------------------------------------------------------------------------------------------------------------------------------------ 107 NGC2258 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1300 S POS TARG -1.1006,-0.8903 ------------------------------------------------------------------------------------------------------------------------------------ 108 NGC2258 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1400 S POS TARG -0.1052,-0.9954 ------------------------------------------------------------------------------------------------------------------------------------ 109 NGC2258 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1300 S POS TARG 1.0895,-1.1017 ------------------------------------------------------------------------------------------------------------------------------------ 110 NGC2258 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1400 S POS TARG 1.8857,-1.2058 ------------------------------------------------------------------------------------------------------------------------------------ 8212( 3) - 02/15/99 11:42 - [ 6] Visit: 02 Visit Priority: Visit Requirements: SAME ORIENT AS 01 GROUP 01, 02 WITHIN 2 D 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 ------------------------------------------------------------------------------------------------------------------------------------ 111 NGC2258 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1300 S POS TARG 1.9931, 0.1881 ------------------------------------------------------------------------------------------------------------------------------------ 112 NGC2258 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1400 S POS TARG 2.0982, 1.1835 ------------------------------------------------------------------------------------------------------------------------------------ 8212( 3) - 02/15/99 11:42 - [ 7] Visit: 03 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 ------------------------------------------------------------------------------------------------------------------------------------ 201 NGC2962 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1100 S POS TARG 0.0, 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 202 NGC2962 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1200 S POS TARG 0.8969, 0.0946 ------------------------------------------------------------------------------------------------------------------------------------ 203 NGC2962 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1100 S POS TARG 1.0010, 0.8908 ------------------------------------------------------------------------------------------------------------------------------------ 204 NGC2962 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1200 S POS TARG 0.1052, 0.9954 ------------------------------------------------------------------------------------------------------------------------------------ 205 NGC2962 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1100 S POS TARG -0.8903, 1.1006 ------------------------------------------------------------------------------------------------------------------------------------ 206 NGC2962 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1200 S POS TARG -0.9965,-0.0940 ------------------------------------------------------------------------------------------------------------------------------------ 8212( 3) - 02/15/99 11:42 - [ 8] Visit: 04 Visit Priority: Visit Requirements: CVZ 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 ------------------------------------------------------------------------------------------------------------------------------------ 301 NGC5308 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1000 S POS TARG 0.0, 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 302 NGC5308 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1000 S POS TARG 0.8969, 0.0946 ------------------------------------------------------------------------------------------------------------------------------------ 303 NGC5308 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1000 S POS TARG 1.0010, 0.8908 ------------------------------------------------------------------------------------------------------------------------------------ 304 NGC5308 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1000 S POS TARG 0.1052, 0.9954 ------------------------------------------------------------------------------------------------------------------------------------ 8212( 3) - 02/15/99 11:42 - [ 9] Visit: 05 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 ------------------------------------------------------------------------------------------------------------------------------------ 401 NGC6495 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1100 S POS TARG 0.0, 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 402 NGC6495 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1200 S POS TARG 0.8969, 0.0946 ------------------------------------------------------------------------------------------------------------------------------------ 403 NGC6495 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1100 S POS TARG 1.0010, 0.8908 ------------------------------------------------------------------------------------------------------------------------------------ 404 NGC6495 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1200 S POS TARG 0.1052, 0.9954 ------------------------------------------------------------------------------------------------------------------------------------ 405 NGC6495 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1100 S POS TARG -0.8903, 1.1006 ------------------------------------------------------------------------------------------------------------------------------------ 406 NGC6495 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1200 S POS TARG -0.9965,-0.0940 ------------------------------------------------------------------------------------------------------------------------------------ 407 NGC6495 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1100 S POS TARG -1.1006,-0.8903 ------------------------------------------------------------------------------------------------------------------------------------ 408 NGC6495 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1200 S POS TARG -0.1052,-0.9954 ------------------------------------------------------------------------------------------------------------------------------------ 8212( 3) - 02/15/99 11:42 - [ 10] Visit: 06 Visit Priority: Visit Requirements: GROUP 06, 07 WITHIN 2 D 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 ------------------------------------------------------------------------------------------------------------------------------------ 501 ESO352-G57 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1100 S POS TARG 0.0, 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 502 ESO352-G57 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1200 S POS TARG 0.8969, 0.0946 ------------------------------------------------------------------------------------------------------------------------------------ 503 ESO352-G57 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1200 S POS TARG 1.0010, 0.8908 ------------------------------------------------------------------------------------------------------------------------------------ 504 ESO352-G57 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1200 S POS TARG 0.1052, 0.9954 ------------------------------------------------------------------------------------------------------------------------------------ 505 ESO352-G57 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1200 S POS TARG -0.8903, 1.1006 ------------------------------------------------------------------------------------------------------------------------------------ 506 ESO352-G57 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1200 S POS TARG -0.9965,-0.0940 ------------------------------------------------------------------------------------------------------------------------------------ 507 ESO352-G57 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1200 S POS TARG -1.1006,-0.8903 ------------------------------------------------------------------------------------------------------------------------------------ 508 ESO352-G57 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1200 S POS TARG -0.1052,-0.9954 ------------------------------------------------------------------------------------------------------------------------------------ 509 ESO352-G57 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1200 S POS TARG 1.0895,-1.1017 ------------------------------------------------------------------------------------------------------------------------------------ 510 ESO352-G57 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1200 S POS TARG 1.8857,-1.2058 ------------------------------------------------------------------------------------------------------------------------------------ 8212( 3) - 02/15/99 11:42 - [ 11] Visit: 07 Visit Priority: Visit Requirements: SAME ORIENT AS 06 GROUP 06, 07 WITHIN 2 D 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 ------------------------------------------------------------------------------------------------------------------------------------ 511 ESO352-G57 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1100 S POS TARG 1.9931, 0.1881 ------------------------------------------------------------------------------------------------------------------------------------ 512 ESO352-G57 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1200 S POS TARG 2.0982, 1.1835 ------------------------------------------------------------------------------------------------------------------------------------ 513 ESO352-G57 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1200 S POS TARG 2.2044, 2.1693 ------------------------------------------------------------------------------------------------------------------------------------ 514 ESO352-G57 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1200 S POS TARG 1.1969, 2.0753 ------------------------------------------------------------------------------------------------------------------------------------ 515 ESO352-G57 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1200 S POS TARG 0.2093, 1.9818 ------------------------------------------------------------------------------------------------------------------------------------ 516 ESO352-G57 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1200 S POS TARG -1.1891, 1.8872 ------------------------------------------------------------------------------------------------------------------------------------ 517 ESO352-G57 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1200 S POS TARG -1.8857, 1.7820 ------------------------------------------------------------------------------------------------------------------------------------ 518 ESO352-G57 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1200 S POS TARG -1.9931, 0.7833 ------------------------------------------------------------------------------------------------------------------------------------ 519 ESO352-G57 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1200 S POS TARG -2.0983,-0.1890 ------------------------------------------------------------------------------------------------------------------------------------ 520 ESO352-G57 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO 1 1200 S POS TARG -2.2045,-1.3110 ------------------------------------------------------------------------------------------------------------------------------------ 8212( 3) - 02/15/99 11:42 - [ 12] Summary Form for Proposal 8212 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PC1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements GROUP 01, 02 WITHIN 2 D POS TARG 0.0, 0.0 POS TARG 0.8969, 0.0946 POS TARG 1.0010, 0.8908 POS TARG 0.1052, 0.9954 POS TARG -0.8903, 1.1006 POS TARG -0.9965,-0.0940 POS TARG -1.1006,-0.8903 POS TARG -0.1052,-0.9954 POS TARG 1.0895,-1.1017 POS TARG 1.8857,-1.2058 SAME ORIENT AS 01 GROUP 01, 02 WITHIN 2 D POS TARG 1.9931, 0.1881 POS TARG 2.0982, 1.1835 CVZ GROUP 06, 07 WITHIN 2 D SAME ORIENT AS 06 GROUP 06, 07 WITHIN 2 D POS TARG 2.2044, 2.1693 POS TARG 1.1969, 2.0753 POS TARG 0.2093, 1.9818 POS TARG -1.1891, 1.8872 POS TARG -1.8857, 1.7820 POS TARG -1.9931, 0.7833 POS TARG -2.0983,-0.1890 POS TARG -2.2045,-1.3110 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC2258 NGC2962 NGC5308 NGC6495 ESO352-G57 ------------------------------------------------------------------------------------------------------------------------------------