6124( 0) - 07/18/95 20:12 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6124 Version: ********** Check-in Date: ********** 1.Proposal Title: `Spotting' Iron-Rich SN Ia Remnants in NGC 5253 ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle Interstellar Medium GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Robert Fesen Dartmouth College CoI: Andrew Hamilton University of Colorado N ------------------------------------------------------------------------------------ 6. Abstract We propose to detect 100 -- 1000 yr old Type Ia supernova remnants in the central region of NGC 5253 by means of obscuration spots due to Fe-rich ejecta resonance line absorptions. Absorption line studies of young supernova remnants represent new and potentially powerful tools for exploring the properties of the freely expanding, iron-rich ejecta expected in SN Ia remnants. , We request WFPC2+F255W images of the amorphous starburst galaxy NGC 5253. Two of the brightest historic Type Ia supernovae occurred here, SN 1895B (= Z Cen) and SN 1972E. By imaging NGC 5253 in the rich ultraviolet Fe I + Fe II resonance line region (2300--3000 Angstrom), 100 - - 1000 yr old SN Ia remnants with V_ exp = 5 - 10 * 10^3 km/s located in NGC 5253's facing nuclear region will be detected as 0.05'' - 0.50'' x (D/4 Mpc) diameter dark `spots'. SN 1895B which exploded just 25'' from the center, is a prime candidate for such iron absorption detection. Older and subsequently larger SN Ia remnants which lie in the galaxy's nuclear region will be detected as well. These detections can place strong constraints on the mass and expansion velocity of iron ejecta in Type Ia SNe and this galaxy's SN Ia rate. ------------------------------------------------------------------------------------ 6124( 0) - 07/18/95 20:12 - [ 2] Observations Description ------------------------ The orbital visibility of NGC 5253 (Dec = --31 deg) is 53 minutes. In order to detect an Fe I/II absorption signal, we need a S/N of at least 4 for the faintest, outer parts of the nuclear region we intend to search for SN Ia absorption spots. SN 1895B lies 25'' off the nucleus and therefore represents the faint end of possible detections and one that we consider a prime SN Ia target for Fe I/II absorption study. We therefore will use it as a basis to calculate the necessary WFPC2 exposure times. For the SN 1895B position, we estimate a NGC 5253 surface brightness of U=20.4 mag/sq. arcsec, from the V surface brightness and B-V and U-B colors of NGC 5253 from Caldwell & Phillips' surface brightness vs. radius plot, and B-V and U-B images. The galaxy is sufficiently blue that it may not be appreciably fainter at 3000 Angstrom\ compared to U (3500 Angstrom). Therefore using m = 20.6 mag, equation 6.1 in the WFPC2 handbook, and intQT dLambda/Lambda = 0.00085 for the F255W filter, we estimate N = 0.013 ct/pixel sec for the region near SN 1895B. In a 600 sec exposurethis means we'll detect 8 e^-. This is comparable to the 0.016 cts dark current at --77 C (Table 4.2; WFPC hdbk) and the 5 e^- of the WFPC's readout noise and means that a 600 sec exposure will then have a S/N = 1.25. To reach a S/N >= 4, requires about 80 cts or ten of these (= 100 minutes). With 53 minutes orbital visibility minus the 12 minutes needed for GS Acquisition, that leaves 41 min for exposures and overhead. We can fit three 10 min exposures plus 8 minutes overhead in this first orbit. In a second and third orbits, which have only a 6 min GS re-acq., we can fit two 18 min CR-SPLIT exposures each with 5 min OH, completely filling the orbit. Thus, in three orbits, the total exposure time will be 30 + 36 + 36 = 102 minutes, enough to give us a S/N = 4 for the SN 1895B and much better than this over the inner 20'' * 40'' nuclear region of the galaxy. Real Time Justification ----------------------- None. We plan U and B CCD images of the NGC 5253 galaxy using the 2.4 m telescope at MDM Observatory, Arizona. We will employ a 1024 x 1024 Tek CCD with 0.25'' pixels with the goal of obtaining deep blue images of the galaxy to compare with the F255W image taken with HST for SN Ia remnant detection. We plan also to examine any archival HST images that may help confirm our detections. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6124( 0) - 07/18/95 20:12 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 001 NGC5253 GALAXY,STARBURST RA=13H 37M 5.25S +/- 0.1S, DEC=- B1950.0 SURF(V)=20+/- 2.0 31D 23' 15" +/- 5" Comments: This galaxy has been classified as an amorphous starburst spiral/irregular. It has had two Type Ia SNe (SN 1895B and SN 1972E). This program consists of three independent images dithered so that we can co- add them to obtain the best S/N and effective resolution. 6124( 0) - 07/18/95 20:12 - [ 4] Visit: 01 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 ------------------------------------------------------------------------------------------------------------------------------------ 11 NGC5253 WFPC2 IMAGE WF3-FIX F255W 2553 CR-SPLIT=NO 1 700S ------------------------------------------------------------------------------------------------------------------------------------ 12 NGC5253 WFPC2 IMAGE WF3-FIX F255W 2553 CR-SPLIT=NO 1 700S ------------------------------------------------------------------------------------------------------------------------------------ 13 NGC5253 WFPC2 IMAGE WF3-FIX F255W 2553 CR-SPLIT=NO 1 700S ------------------------------------------------------------------------------------------------------------------------------------ 21 NGC5253 WFPC2 IMAGE WF3-FIX F255W 2553 CR-SPLIT=NO 1 800S POS TARG -0.50,0.50 ------------------------------------------------------------------------------------------------------------------------------------ 22 NGC5253 WFPC2 IMAGE WF3-FIX F255W 2553 CR-SPLIT=NO 1 800S POS TARG -0.50,0.50 ------------------------------------------------------------------------------------------------------------------------------------ 23 NGC5253 WFPC2 IMAGE WF3-FIX F255W 2553 CR-SPLIT=NO 1 800S POS TARG -0.50,0.50 ------------------------------------------------------------------------------------------------------------------------------------ 31 NGC5253 WFPC2 IMAGE WF3-FIX F255W 2553 CR-SPLIT=NO 1 800S POS TARG 0.50,0.50 ------------------------------------------------------------------------------------------------------------------------------------ 32 NGC5253 WFPC2 IMAGE WF3-FIX F255W 2553 CR-SPLIT=NO 1 800S POS TARG 0.50,0.50 ------------------------------------------------------------------------------------------------------------------------------------ 33 NGC5253 WFPC2 IMAGE WF3-FIX F255W 2553 CR-SPLIT=NO 1 800S POS TARG 0.50,0.50 ------------------------------------------------------------------------------------------------------------------------------------ 6124( 0) - 07/18/95 20:12 - [ 5] Summary Form for Proposal 6124 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category Interstellar Medium ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements POS TARG -0.50,0.50 POS TARG 0.50,0.50 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F255W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC5253 ------------------------------------------------------------------------------------------------------------------------------------