9155( 2) - 02/16/01 14:59 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9155 Version: 2 Check-in Date: 16-Feb-2001 14:58:59 1.Proposal Title: The Cepheid Distance to NGC 1637: A Direct Comparison with the EPM Distance to SN 1999em ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 10 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Douglas Leonard Five Colleges, Inc. CoI: Prof. Shashi Kanbur University of Massachusetts at Amherst N CoI: Dr. Nial Tanvir University of Hertfordshire N ------------------------------------------------------------------------------------ 5. Abstract Opportunities to directly compare distances estimated by two primary extragalactic distance indicators are rare. The appearance of supernova 1999em, a bright, extremely well- observed type II plateau (II-P) event in the nearby SBc galaxy NGC 1637 (v = 717 km s^-1), offers the best chance to test the consistency of the Expanding Photosphere Method (EPM) of supernova distance determination with that derived from Cepheid variable stars. Although EPM distances have been measured to 18 type II supernovae out to 180 Mpc and used to determine Hubble's constant independent of the Cepheid distance scale (H_o = 73 +/- 7 km s^-1 Mpc^-1 Schmidt et al. 1994a), there have never been any measurements of Cepheids in a galaxy that has hosted a normal type II-P supernova, the classic variety of core-collapse event to which EPM-derived distances are most robust. We thus propose to determine the distance to NGC 1637 through the discovery and analysis of its Cepheid variable stars. Since previous distance estimates to NGC 1637 exist using the Tully-Fisher relation (d = 8.9 Mpc) and the galaxy's brightest red supergiants (d = 7.8 Mpc), a Cepheid distance will further refine the calibration of these secondary distance indicators as well. Cycle 10 observations of NGC 1637 will also provide rare late- time light curve measurements of a type II-P supernova more than two years after explosion. ------------------------------------------------------------------------------------ 9155( 2) - 02/16/01 14:59 - [ 2] Observations Description ------------------------ The goal of the observations is to detect Cepheid variables in the host galaxy of SN 1999em, NGC 1637 (d ~ 8 Mpc; Sohn & Davidge 1998; Tully 1988), and to determine their mean magnitudes and periods to estimate their distance. We also wish to include the fading SN 1999em in the field of view, in order to study its late-time lightcurve and stellar environment. We wish to follow, as closely as possible, the well-tested observing strategy used by the HST Key Project (KP) on the Extragalactic Distance Scale in their discovery and analysis of Cepheids in galaxies extending out to 25 Mpc. Similar to KP studies involving galaxies at distances comparable to NGC 1637 (e.g., Graham et al. 1997; Rawson et al. 1997), our approach is to observe at 12 optimally spaced epochs within a single 60 day observing window in the F555W V-band, and on 6 occasions to also obtain F814W I-band images; this will allow us to best sample Cepheids with periods from 10 to 60 days (see, e.g., Freedman et al. 1994). Optimal spacing consists of having 12 observations with a range of separations scheduled within a single 60 day observing window. The V-band photometry allows identification of variables and characterization of period and light curve shape; the I-band photometry allows correction for extinction (foreground and internal to NGC 1637) based on the colors of the Cepheids themselves (a detailed discussion of this method is given in Tanvir 1999). A 60 day observation window will allow us to find long period Cepheids while also preserving a constant telescope orientation to facilitate analysis. Our target Cepheids should have 23.2 < m_V < 25.3, well within the magnitude limit of the Cepheids detected by the KP using the same approach (generally about 26.5 mag). The low declination of NGC 1637 (Delta =-02 degrees) limits its regular visibility to 52 minutes per orbit (Table 6.1 of the HST Cycle 10 Primer). Accounting for overhead, this should allow for sequences of two 1000 - 1500 second observations (i.e., 1 CR-splint 2300 second image) per orbit, sufficiently deep to give 10% photometry. This will allow us to obtain mean PL relations in V and I. For NGC 1637, the necessity of maintaining a constant telescope orientation throughout a 60 day window restricts the available telescope orientations to 2 rather narrow ranges centered near 65 and 278 degrees for WFPC2. The orientation of 278 degrees best satisfies our primary scientific objective of including the outer regions of NGC 1637 (including both spiral arms) while also including SN 1999em within the total field of view (though not on the PC chip, since getting the maximum amount of the outer spiral arms necessitates placing SN 1999em on WF4). Real Time Justification ----------------------- The observations are not time-critical. As explained above, however, to be useful the observations must be spaced as close to the requested optimal spacing as possible, in order to properly sample the lightcurves of the Cepheids we find and exclude aliasing. This will provide us with good precision in estimating the mean magnitudes and the periods. While there is some flexibility in the date for the first observation (we have allowed for a small range of orientation angles in order to provide flexibility in the scheduling), once the observations have started we request that the program proceed as close as possible to the optimal spacings. This is critical for obtaining the most uniform phase coverage for the Cepheids. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9155( 2) - 02/16/01 14:59 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC1637 EXT-STAR, CEPHEID, RA = 04H41M26.72S +/- 1.0", DEC J2000 V = +717 SURF(B) = 22.34+/-0.49 SUPERNOVA TYPE II, = -02D51'8.26" +/- 1.0", PLATE- E(B-V) = 0.04 GALAXY, SPIRAL ID = 044N Coordinate Source: GUIDE_STAR_CATALOG Comments: VTT Generated target from DSS image. 9155( 2) - 02/16/01 14:59 - [ 4] Visit: 01 Visit Priority: Visit Requirements: ORIENT 275D TO 282D SCHED 100% On Hold Comments: Additional Comments: The orientation must be the same for all visits. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC1637 WFPC2 IMAGE PC1-FIX F555W 1 2300 S ------------------------------------------------------------------------------------------------------------------------------------ 20 NGC1637 WFPC2 IMAGE PC1-FIX F814W 1 2300 S ------------------------------------------------------------------------------------------------------------------------------------ 9155( 2) - 02/16/01 14:59 - [ 5] Visit: 02 Visit Priority: Visit Requirements: SAME ORIENT AS 01 AFTER 01 BY 7.86 D TO 9.46 D SCHED 100% 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC1637 WFPC2 IMAGE PC1-FIX F555W 1 2300 S ------------------------------------------------------------------------------------------------------------------------------------ 20 NGC1637 WFPC2 IMAGE PC1-FIX F814W 1 2300 S ------------------------------------------------------------------------------------------------------------------------------------ 9155( 2) - 02/16/01 14:59 - [ 6] Visit: 03 Visit Priority: Visit Requirements: SAME ORIENT AS 01 AFTER 01 BY 18.44 D TO 19.04 D SCHED 100% 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC1637 WFPC2 IMAGE PC1-FIX F555W 1 2300 S ------------------------------------------------------------------------------------------------------------------------------------ 9155( 2) - 02/16/01 14:59 - [ 7] Visit: 04 Visit Priority: Visit Requirements: SAME ORIENT AS 01 AFTER 01 BY 21.02 D TO 21.62 D SCHED 100% 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC1637 WFPC2 IMAGE PC1-FIX F555W 1 2300 S ------------------------------------------------------------------------------------------------------------------------------------ 9155( 2) - 02/16/01 14:59 - [ 8] Visit: 05 Visit Priority: Visit Requirements: SAME ORIENT AS 01 AFTER 01 BY 23.93 D TO 24.53 D SCHED 100% 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC1637 WFPC2 IMAGE PC1-FIX F555W 1 2300 S ------------------------------------------------------------------------------------------------------------------------------------ 20 NGC1637 WFPC2 IMAGE PC1-FIX F814W 1 2300 S ------------------------------------------------------------------------------------------------------------------------------------ 9155( 2) - 02/16/01 14:59 - [ 9] Visit: 06 Visit Priority: Visit Requirements: SAME ORIENT AS 01 AFTER 01 BY 27.23 D TO 27.83 D SCHED 100% 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC1637 WFPC2 IMAGE PC1-FIX F555W 1 2300 S ------------------------------------------------------------------------------------------------------------------------------------ 20 NGC1637 WFPC2 IMAGE PC1-FIX F814W 1 2300 S ------------------------------------------------------------------------------------------------------------------------------------ 9155( 2) - 02/16/01 14:59 - [ 10] Visit: 07 Visit Priority: Visit Requirements: SAME ORIENT AS 01 AFTER 01 BY 30.88 D TO 31.68 D SCHED 100% 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC1637 WFPC2 IMAGE PC1-FIX F555W 1 2300 S ------------------------------------------------------------------------------------------------------------------------------------ 9155( 2) - 02/16/01 14:59 - [ 11] Visit: 08 Visit Priority: Visit Requirements: SAME ORIENT AS 01 AFTER 01 BY 35.16 D TO 35.96 D SCHED 100% 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC1637 WFPC2 IMAGE PC1-FIX F555W 1 2300 S ------------------------------------------------------------------------------------------------------------------------------------ 9155( 2) - 02/16/01 14:59 - [ 12] Visit: 09 Visit Priority: Visit Requirements: SAME ORIENT AS 01 AFTER 01 BY 39.95 D TO 40.95 D SCHED 100% 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC1637 WFPC2 IMAGE PC1-FIX F555W 1 2300 S ------------------------------------------------------------------------------------------------------------------------------------ 9155( 2) - 02/16/01 14:59 - [ 13] Visit: 10 Visit Priority: Visit Requirements: SAME ORIENT AS 01 AFTER 01 BY 45.47 D TO 46.67 D SCHED 100% 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC1637 WFPC2 IMAGE PC1-FIX F555W 1 2300 S ------------------------------------------------------------------------------------------------------------------------------------ 20 NGC1637 WFPC2 IMAGE PC1-FIX F814W 1 2300 S ------------------------------------------------------------------------------------------------------------------------------------ 9155( 2) - 02/16/01 14:59 - [ 14] Visit: 11 Visit Priority: Visit Requirements: SAME ORIENT AS 01 AFTER 01 BY 51.93 D TO 53.13 D SCHED 100% 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC1637 WFPC2 IMAGE PC1-FIX F555W 1 2300 S ------------------------------------------------------------------------------------------------------------------------------------ 9155( 2) - 02/16/01 14:59 - [ 15] Visit: 12 Visit Priority: Visit Requirements: SAME ORIENT AS 01 AFTER 01 BY 59.3 D TO 60.7 D SCHED 100% 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC1637 WFPC2 IMAGE PC1-FIX F555W 1 2300 S ------------------------------------------------------------------------------------------------------------------------------------ 20 NGC1637 WFPC2 IMAGE PC1-FIX F814W 1 2300 S ------------------------------------------------------------------------------------------------------------------------------------ 9155( 2) - 02/16/01 14:59 - [ 16] Summary Form for Proposal 9155 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PC1-FIX ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 275D TO 282D SCHED 100% SAME ORIENT AS 01 AFTER 01 BY 7.86 D TO 9.46 D SCHED 100% SAME ORIENT AS 01 AFTER 01 BY 18.44 D TO 19.04 D SCHED 100% SAME ORIENT AS 01 AFTER 01 BY 21.02 D TO 21.62 D SCHED 100% SAME ORIENT AS 01 AFTER 01 BY 23.93 D TO 24.53 D SCHED 100% SAME ORIENT AS 01 AFTER 01 BY 27.23 D TO 27.83 D SCHED 100% SAME ORIENT AS 01 AFTER 01 BY 30.88 D TO 31.68 D SCHED 100% SAME ORIENT AS 01 AFTER 01 BY 35.16 D TO 35.96 D SCHED 100% SAME ORIENT AS 01 AFTER 01 BY 39.95 D TO 40.95 D SCHED 100% SAME ORIENT AS 01 AFTER 01 BY 45.47 D TO 46.67 D SCHED 100% SAME ORIENT AS 01 AFTER 01 BY 51.93 D TO 53.13 D SCHED 100% SAME ORIENT AS 01 AFTER 01 BY 59.3 D TO 60.7 D SCHED 100% ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F555W F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC1637 ------------------------------------------------------------------------------------------------------------------------------------