8252( 7) - 09/21/99 14:46 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8252 Version: 7 Check-in Date: 21-Sep-1999 14:45:29 1.Proposal Title: Extinction Curves of Distant Galaxies ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 8 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Christopher Kochanek Harvard University CoI: Dr. Emilio Falco Smithsonian Astrophysical Observatory N CoI: Dr. Chris Impey University of Arizona N CoI: Dr. Hans-Walter Rix University of Arizona N CoI: Dr. Charles Keeton University of Arizona N CoI: Dr. Joseph Lehar Harvard-Center for Astrophysics N CoI: Dr. Brian McLeod Smithsonian Astrophysical Observatory N CoI: Dr. Jose Munoz Smithsonian Astrophysical Observatory N CoI: Mr. Chien Peng University of Arizona N ------------------------------------------------------------------------------------ 5. Abstract We propose to measure extinction curves in five external galaxies ranging in redshift from 0.039 to 0.96 using gravitational lenses that show differential extinction between the images. The program will more than double the number of galaxies in which extinction curves have been measured and it will provide the first such measurements far outside the local group, in early-type galaxies and at significantly different cosmic epochs. STIS spectroscopic observations will focus on the 2175Angstrom\ feature, combined with WFPC2 and STIS photometry to check for variability and extend the wavelength coverage. For the two systems in our sample that are radio quasars, we will be able to check for the presence of dust which is gray in the IR--UV spectral range. ------------------------------------------------------------------------------------ 8252( 7) - 09/21/99 14:46 - [ 2] Observations Description ------------------------ Our strategy is to use WFPC2 and STIS imaging to measure the flux ratios between the images for wavelengths away from the 2175Angstrom\ feature, and STIS spectroscopy to measure the flux ratios near the 2175Angstrom\ feature. Away from the feature the slow variation with wavelength Lambda of the extinction curve can be well determined from broad-band filters, but the rapid variation with Lambda near the feature would require suitable sets of narrow band filters, which are lacking in both WFPC2 and STIS. We are using the STIS spectra as a substitute for narrow band imaging. Note that we can use spectra with relatively low S/N per pixel, because we only need high S/N after averaging the spectra over 50- 100Angstrom\ wavelength bins. Spectra are always more efficient options because STIS obtains the data in parallel rather then sequentially. Our target S/N for the final photometric measurements is a maximum of 100 and a minimum of 30. The overlaps with existing WFPC2 images (see below) help to control systematic uncertainties. STIS exposure estimates include the ~ 1/3 orbit overheads to perform the required target acquisitions. We can obtain the spectra of two images simultaneously, so one spectrum is required for a two-image lens, and two spectra are required for a four-image lens. The lower wavelength limit for the data is set either by the quasar Lyman limit (LBQS 1009, HE 1104, Q 2237) or exposure time limits (B 0218, MG 0414). Figure 1 illustrates the spectral features, grating coverage, and filter locations for 3 of the 5 systems. (1) B 0218+357 -- We cannot observe the 2175Angstrom\ feature in finite time because the fainter image has I=21.8, V=23.4, U=24.2 mags. We will limit the determination to broadband IRVBU flux ratio measurements with WFPC2. The required exposure time to meet the S/N goals is 4 orbits. (2) MG 0414+0534 -- We cannot observe the 2175Angstrom\ feature in finite time because the faintest image has I=22.2 and R=24.3 mag. The extrapolated magnitudes are V=26.3 and B=28.2, so we can extend the extinction curve measurement to V in 2 orbits. The B flux ratios are impossible to measure unless the magnitude extrapolation is significantly in error. (3) LBQS 1009-- 0252 -- We can observe the 2175Angstrom\ feature using the G430L grating and the 52" * 0arcs2 slit. In 5 orbits we obtain S/N>10 over most of the spectral range based on the STIS QSO spectrum normalized by the magnitude of the faintest image (V=20.5 mag). One WFPC2 orbit will complement the spectrum with IRVB flux ratios. (4) HE 1104--1805 -- We can observe the 2175Angstrom\ feature using the G430L grating and the 52" * 0arcs2 slit. In 2 orbits we obtain S/N>10 over most of the spectral range based on the STIS QSO spectrum normalized by the magnitude of the faintest image (V=18.6 mag). One WFPC2 orbit will measure the IRVB flux ratios, and one STIS imaging orbit with the NUV/MAMA and the long pass filter (F25SRF2) will add a (rest frame) far UV point. (5) Q 2337+0305 -- We can observe the 2175Angstrom\ feature using the G230L grating, the MAMA, and the 52" * 0arcs1 slit. It requires 2 orbits with the slit on the bright A/B image pair and 5 orbits for the fainter C/D image pair. The extinction curve determination requires both pairs. The lens galaxy is bright (B=15 mag) and is nearby, at z_l=0.04, so we use the narrow slit to minimize the effect of galaxy contamination. Two WFPC2 imaging orbits can determine the IRVBU flux ratios. NOTE: because of the limited number of orbits the TAC awarded in this case (10), and their request to demonstrate our method, we have dropped the STIS observations and switched to only WFPC2 multi-band imaging (as approved by ST). Real Time Justification ----------------------- The WFPC2 observations of each object in different filters must be taken in successive orbits to minimize the introduction of systematic errors in the extinction curve determinations due to variability. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 8252( 7) - 09/21/99 14:46 - [ 3] Data Distribution Paper Products: NO Media: ELECTRONIC Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 8252( 7) - 09/21/99 14:46 - [ 4] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 B0218+357 GALAXY, GRAVITATIONAL RA=02H 21M 05.60S +/- 0.06S, J2000 V = 20.00 LENS DEC=+35D 56' 11.90" +/- 1.0", V-I = 1.80 PLATE-ID=031L Comments: QSO V=20, sep=0.3". Lens V=20. No saturation. 2 LBQS1009- GALAXY, GRAVITATIONAL RA=10H 12M 15.84S +/- 0.06S, J2000 V = 17.00 0252 LENS DEC=-03D 07' 03.98" +/- 1.0", V-I = -0.60 PLATE-ID=02NC Comments: QSO V=17, sep=1.5". Lens V=23. Saturates in 300s. 3 Q2237+0305 GALAXY, GRAVITATIONAL RA=22H 40M 30.34S +/- 0.06S, J2000 V = 17.00 LENS DEC=+03D 21' 28.79" +/- 1.0", V-I = 1.00 PLATE-ID=04M8 Comments: QSO V=17, sep=1.7". Lens V=16. Saturates in 300s. 8252( 7) - 09/21/99 14:46 - [ 5] Visit: 01 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: V=20, no saturation Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 11 B0218+357 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO,ATD-GAIN=7 1 120 S ------------------------------------------------------------------------------------------------------------------------------------ 12 B0218+357 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO,ATD-GAIN=7 1 120 S POS TARG 0.3535, 0.3535 ------------------------------------------------------------------------------------------------------------------------------------ 13 B0218+357 WFPC2 IMAGE PC1 F675W CR-SPLIT=NO,ATD-GAIN=7 1 180 S SAME POS AS 12 ------------------------------------------------------------------------------------------------------------------------------------ 14 B0218+357 WFPC2 IMAGE PC1 F675W CR-SPLIT=NO,ATD-GAIN=7 1 180 S ------------------------------------------------------------------------------------------------------------------------------------ 15 B0218+357 WFPC2 IMAGE PC1 F555W CR-SPLIT=NO,ATD-GAIN=7 1 230 S POS TARG 0.3535, 0.3535 ------------------------------------------------------------------------------------------------------------------------------------ 16 B0218+357 WFPC2 IMAGE PC1 F555W CR-SPLIT=NO,ATD-GAIN=7 1 230 S SEQ 0011-0016 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 17 B0218+357 WFPC2 IMAGE PC1 F439W CR-SPLIT=NO,ATD-GAIN=7, 1 700 S DITHER-TYPE=LINE, DITHER-LINE-STEPS=3 ------------------------------------------------------------------------------------------------------------------------------------ 18 B0218+357 WFPC2 IMAGE PC1 F380W CR-SPLIT=DEF,ATD-GAIN=7, 1 2600 S DITHER-TYPE=LINE, DITHER-LINE-STEPS=3 ------------------------------------------------------------------------------------------------------------------------------------ 8252( 7) - 09/21/99 14:46 - [ 6] Visit: 02 Visit Priority: Visit Requirements: SAME ORIENT AS 1 SEQ 1-2 WITHIN 8.04H On Hold Comments: Additional Comments: V=20, no saturation Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 19 B0218+357 WFPC2 IMAGE PC1 F300W CR-SPLIT=NO,ATD-GAIN=7, 1 700 S DITHER-TYPE=LINE, DITHER-LINE-STEPS=3 ------------------------------------------------------------------------------------------------------------------------------------ 8252( 7) - 09/21/99 14:46 - [ 7] Visit: 03 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: V=17, saturates in 300s. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 21 LBQS1009-02 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO,ATD-GAIN=7 1 60 S 52 ------------------------------------------------------------------------------------------------------------------------------------ 22 LBQS1009-02 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO,ATD-GAIN=7 1 60 S POS TARG 0.3535, 0.3535 52 ------------------------------------------------------------------------------------------------------------------------------------ 23 LBQS1009-02 WFPC2 IMAGE PC1 F675W CR-SPLIT=NO,ATD-GAIN=7 1 60 S SAME POS AS 22 52 ------------------------------------------------------------------------------------------------------------------------------------ 24 LBQS1009-02 WFPC2 IMAGE PC1 F675W CR-SPLIT=NO,ATD-GAIN=7 1 60 S 52 ------------------------------------------------------------------------------------------------------------------------------------ 25 LBQS1009-02 WFPC2 IMAGE PC1 F555W CR-SPLIT=NO,ATD-GAIN=7 1 60 S SAME POS AS 24 52 ------------------------------------------------------------------------------------------------------------------------------------ 26 LBQS1009-02 WFPC2 IMAGE PC1 F555W CR-SPLIT=NO,ATD-GAIN=7 1 60 S POS TARG 0.3535, 0.3535 52 ------------------------------------------------------------------------------------------------------------------------------------ 27 LBQS1009-02 WFPC2 IMAGE PC1 F439W CR-SPLIT=NO,ATD-GAIN=7 1 180 S SAME POS AS 26 52 ------------------------------------------------------------------------------------------------------------------------------------ 28 LBQS1009-02 WFPC2 IMAGE PC1 F439W CR-SPLIT=NO,ATD-GAIN=7 1 180 S 52 ------------------------------------------------------------------------------------------------------------------------------------ 29 LBQS1009-02 WFPC2 IMAGE PC1 F380W CR-SPLIT=NO,ATD-GAIN=7 1 350 S POS TARG 0.3535, 0.3535 52 ------------------------------------------------------------------------------------------------------------------------------------ 30 LBQS1009-02 WFPC2 IMAGE PC1 F380W CR-SPLIT=NO,ATD-GAIN=7 1 350 S 52 ------------------------------------------------------------------------------------------------------------------------------------ 31 LBQS1009-02 WFPC2 IMAGE PC1 F336W CR-SPLIT=NO,ATD-GAIN=7 1 500 S SAME POS AS 30 52 ------------------------------------------------------------------------------------------------------------------------------------ 32 LBQS1009-02 WFPC2 IMAGE PC1 F336W CR-SPLIT=NO,ATD-GAIN=7 1 500 S POS TARG 0.3535, 0.3535 52 ------------------------------------------------------------------------------------------------------------------------------------ 8252( 7) - 09/21/99 14:46 - [ 8] Visit: 04 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: V=17, saturates in 300s Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 41 Q2237+0305 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO,ATD-GAIN=7 1 60 S ------------------------------------------------------------------------------------------------------------------------------------ 42 Q2237+0305 WFPC2 IMAGE PC1 F814W CR-SPLIT=NO,ATD-GAIN=7 1 60 S POS TARG 0.3535, 0.3535 ------------------------------------------------------------------------------------------------------------------------------------ 43 Q2237+0305 WFPC2 IMAGE PC1 F675W CR-SPLIT=NO,ATD-GAIN=7 1 60 S SAME POS AS 42 ------------------------------------------------------------------------------------------------------------------------------------ 44 Q2237+0305 WFPC2 IMAGE PC1 F675W CR-SPLIT=NO,ATD-GAIN=7 1 60 S POS TARG 0.3535, 0.3535 ------------------------------------------------------------------------------------------------------------------------------------ 45 Q2237+0305 WFPC2 IMAGE PC1 F555W CR-SPLIT=NO,ATD-GAIN=7 1 60 S ------------------------------------------------------------------------------------------------------------------------------------ 46 Q2237+0305 WFPC2 IMAGE PC1 F555W CR-SPLIT=NO,ATD-GAIN=7 1 60 S POS TARG 0.3535, 0.3535 ------------------------------------------------------------------------------------------------------------------------------------ 47 Q2237+0305 WFPC2 IMAGE PC1 F439W CR-SPLIT=NO,ATD-GAIN=7 1 120 S POS TARG 0.3535, 0.3535 ------------------------------------------------------------------------------------------------------------------------------------ 48 Q2237+0305 WFPC2 IMAGE PC1 F439W CR-SPLIT=NO,ATD-GAIN=7 1 120 S SEQ 0041-0048 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 49 Q2237+0305 WFPC2 IMAGE PC1 F336W CR-SPLIT=NO,ATD-GAIN=7 1 60 S ------------------------------------------------------------------------------------------------------------------------------------ 50 Q2237+0305 WFPC2 IMAGE PC1 F336W CR-SPLIT=NO,ATD-GAIN=7 1 60 S POS TARG 0.3535, 0.3535 ------------------------------------------------------------------------------------------------------------------------------------ 51 Q2237+0305 WFPC2 IMAGE PC1 F300W CR-SPLIT=NO,ATD-GAIN=7 1 120 S SAME POS AS 50 ------------------------------------------------------------------------------------------------------------------------------------ 52 Q2237+0305 WFPC2 IMAGE PC1 F300W CR-SPLIT=NO,ATD-GAIN=7 1 120 S ------------------------------------------------------------------------------------------------------------------------------------ 53 Q2237+0305 WFPC2 IMAGE PC1 F255W CR-SPLIT=NO,ATD-GAIN=7 1 160 S POS TARG 0.3535, 0.3535 ------------------------------------------------------------------------------------------------------------------------------------ 54 Q2237+0305 WFPC2 IMAGE PC1 F255W CR-SPLIT=NO,ATD-GAIN=7 1 160 S ------------------------------------------------------------------------------------------------------------------------------------ 55 Q2237+0305 WFPC2 IMAGE PC1 F218W CR-SPLIT=NO,ATD-GAIN=7 1 180 S SAME POS AS 54 ------------------------------------------------------------------------------------------------------------------------------------ 56 Q2237+0305 WFPC2 IMAGE PC1 F218W CR-SPLIT=NO,ATD-GAIN=7 1 180 S POS TARG 0.3535, 0.3535 ------------------------------------------------------------------------------------------------------------------------------------ 8252( 7) - 09/21/99 14:46 - [ 9] Summary Form for Proposal 8252 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PC1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ATD-GAIN=7 DITHER-LINE-STEPS=3 DITHER-TYPE=LINE ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements POS TARG 0.3535, 0.3535 SAME POS AS 12 SEQ 0011-0016 NON-INT SAME ORIENT AS 1 SEQ 1-2 WITHIN 8.04H SAME POS AS 22 SAME POS AS 24 SAME POS AS 26 SAME POS AS 30 SAME POS AS 42 SEQ 0041-0048 NON-INT SAME POS AS 50 SAME POS AS 54 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F814W F675W F555W F439W F380W F300W F336W F255W F218W ------------------------------------------------------------------------------------------------------------------------------------ Target Names B0218+357 LBQS1009-0252 Q2237+0305 ------------------------------------------------------------------------------------------------------------------------------------