9421( 6) - 03/18/03 08:27 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9421 Version: 6 Check-in Date: 18-Mar-2003 08:26:14 1.Proposal Title: UV Observations of Hubble Flow Type Ia Supernovae ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 11 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Peter Nugent Lawrence Berkeley National Laboratory CoI: Dr. Greg Aldering Lawrence Berkeley Laboratory N CoI: Dr. Reynald Pain LPNHE, Universites Paris VI & VII N CoI: Dr. Saul Perlmutter Lawrence Berkeley Laboratory N CoI: Dr. Mark Phillips Carnegie Institution of Washington N CoI: Dr. Yulei Qui Beijing Observatory N CoI: Dr. Chris Smith NOAO N CoI: Dr. Nick Suntzeff NOAO N CoI: Mr. Michael Wood-Vasey Lawrence Berkeley Laboratory N ------------------------------------------------------------------------------------ 5. Abstract Two independent research groups have presented compelling evidence for an accelerating universe from the observation of high-redshift Type Ia supernovae (SNe Ia). These findings have such important ramifications for cosmology that every effort must be made to thoroughly test the calibrated standard candles on which they are based, improve upon our understanding of the underlying physics of the SN Ia explosion mechanism and attempt to constrain or determine their progenitors. Here we propose to obtain STIS UV spectra of five Hubble Flow SNe Ia. The spectra will be taken at weekly intervals over a range in time starting slightly before maximum light and extending to +30 days. These observations will accomplish the following three goals: (1) Calibration of the rest frame UV light curves of SNe Ia and an assessment of their potential use as distance indicators through UV light curve shape analyses. (2) Improvement in our understanding of the physics of SNe Ia, metallicity/evolutionary effects and correlations between peak brightness and UV spectral features. (3) Calibration of the SNe Ia previously observed by HST at high- redshift. For z > 0.8 SNe Ia discovered by the Supernova Cosmology Project, the High-Z Supernovae Search Team and future HST discovered SNe Ia (like SN 1997ff found in the HDF) this data is crucial for proper cross-filter K-corrections and calibration of the supernova photometry. ------------------------------------------------------------------------------------ 9421( 6) - 03/18/03 08:27 - [ 2] Observations Description ------------------------ In the Spring of 1999 several supernova search and asteroid search groups formed an alliance to find a large batch of nearby supernovae (see Aldering et al., 2000 and Nugent & Aldering 2000 and IAUC's 7109 , 7117 , 7122 , 7125 , 7128 , 7130 , 7131 , 7133 , 7134 , 7136 , 7138. The key element of the alliance was to run all of the supernova searches simultaneously so that the follow-up resources were used in a concentrated and complementary fashion. This provided us with the well sampled photometric (multiple times a week) and spectroscopic (weekly) follow-up required to yield the greatest scientific return. In total the alliance discovered 35 supernovae during the month of March, 1999. Twenty SNe Ia were caught before or at maximum light and were followed with UBVRI photometry and spectroscopy for over three months. In the Spring of 2001 we embarked on a successful campagin to provide HST with two SNe Ia in the Hubble flow to be observed under the Nugent et al. GO 8611 program. SNe 2001ay and 2001ba (both at 9000 km/s) were observed by HST just after maximum light. Unfortunately with the STIS failure the scheduled observations were cut short. Starting September 2001 we have expanded the search by making use of both the Palomar Schmidt Telescope and the NEAT/MSSS telescope at Haleakala to scan approximately 10, 000 sq.deg. every week down to 19th magnitude. Over 50 Gb of data is sent each night from the telescopes to the computers at the National Energy Research Supercomputing Center to be processed and searched for supernovae. Early success in this program has been seen in the pre-discovery observations of SNe 2001dd, 2001dy, and 2001ed ( IAUC's 7664, 7700 and 7706). The yield, based on the rates observed to date, will be 1 SN Ia every night with a z < 0.1 on the rising portion of its light curve. This puts us in the unique position of being able to produce nearby supernovae on demand for observation by the HST. While still a TOO proposal, we will be able to schedule the exact dates of discovery and followup months in advance, with only the precise location of the supernova unknown until one week before observation by the HST. This type of TOO is much easier to schedule and has minimal impact on HST scheduling. This proposal requests time to obtain STIS UV spectra of five nearby (0.03 < z < 0.08) SNe Ia at six epochs. The spectra will be taken at weekly intervals over a range in time starting slightly before maximum light and extending to +30 days. For the first three epochs near maximum the spectra must have sufficient signal-to-noise to distinguish spectral features which vary with metallicity and change with epoch down to ~ 2850 Angstrom\ in the rest-frame (see Figure refmetal). The iron-peak blends (Co and Fe of varying ionizations) at ~2890 and 3165 Angstrom\ have FWHM of ~100 Angstrom\ and shift by 60 Angstrom\ when going from 0.1 solar to 10 times solar metallicity. The measurement of this shift is an extinction-independent diagnostic of metallicity. The amplitudes (measured relative to the spectrum around 3600 Angstrom) of these features vary by 75\ metallicity indicator is only slightly dependent upon the extinction. Using an available UV spectrum of an unreddened, normal luminosity SN Ia near maximum light and the spectra we observed in GO 8611, we estimate that 2 orbits are required to achieve signal-to- noise > 10 per 5.5 Angstrom\ resolution element (with the 430L grating and STIS binned 2X in the dispersion axis). Our observations of SN 2001ay and 2001ba bear these numbers out. With this exposure the critical spectral features discussed above can be measured to estimate the metallicity to better than 0.2 dex, even for intrinsically subluminous SNe Ia or those which suffer mild host galaxy extinction. In order to aid in the calibration of the highest redshift SNe Ia (z > 1.2) we request a single spectrum taken with STIS/NUV-MAMA with the 230L grating. Given the fluxes observed for SNe 2001ay and 2001ba, combined with an extrapolation based on very nearby SNe Ia observed with IUE, similar S/N ratios as above can be obtained in 2 orbits (all calculations were carried out on the STIS exposure time calculator). Thus at maximum light we will have a flux 9421( 6) - 03/18/03 08:27 - [ 3] calibrated spectrum from 2000 Angstrom\ redward with sufficient S/N to calibrate even the highest redshift supernovae discovered by HST. For the final three epochs the signal-to-noise will be too low to measure these metallicity features with such precision. However, we will still be able to perform synthetic UV photometry from the spectra which will be used to construct template UV light curves and calibrate the stretch luminosity relationship in the UV. The spectra will also have sufficient signal-to-noise (~ 1 per 5.5 Angstrom\ resolution element) to calculate K-corrections for the extant HST observations of high-z SNe Ia. Note that the 2x binning puts us in the dark current limited regime and that the sky background is relatively small. This also allows us to use a 0.5'' slit which will result in only small losses making absolute spectrophotometry possible. These targets will be optically bright and will have ground-based astrometry with-respect-to HST guide stars to better than 0.2''. Using the STIS Acquisition ETC we find acquisition times less than 1 minute for all epochs and redshifts. Real Time Justification ----------------------- This is a TOO proposal to observe time-evolving SNe Ia near maximum light in the UV. Unlike other TOO proposals we will be able to schedule the exact dates for each visit by HST months in advance (see description of the SNe Ia search located above). What we will not know until one week before HST needs to acquire the target is it's precise location on the sky. After discovery SNe Ia coordinates will be know for all subsequent epochs. This should allow normal scheduling of all but the first epoch HST observations. Due to our discovery rate of a few per week in the Hubble flow we can easily accommodate the HST schedulers to group or break apart the any or all of the observations. Ground based UBVRIJHK photometry and optical/IR spectroscopy will be obtained every few days for these SNe Ia. No scheduling constraints are placed on HST by these observations. As we did in GO 8611 we will apply for time at the following telescopes: Las Campanas: We will ask for spectroscopic time on the 2.5-m, and infrared imaging time on the 1.0-m and 2.5-m. Lick Observatory: We will ask for spectroscopic time on the 3.0-m and optical imaging on the 1.0m. Keck: We will apply for a night to do spectropolarimetry of a subset of our candidates. UH 2.2-m: Here we have a small amount of dedicated time for spectroscopic follow- up. In this joint proposal for NOAO observations we make a request for 48 hrs on the queue scheduled YALO telescope. Based on our search and followup in Apr- Jun 2001 for GO 8611 of SNe 2001ay and 2001ba the YALO telescope was the perfect instrument for providing optical photometric follow-up. If necessary, and depending on the instruments available at the time we conduct the search, we will submit other NOAO proposals. Our YALO allocation reuest is based on our with this instrument in the study of SNe. For SNe Ia in the middle of our range in redshift (z=0.05), they have a B-band magnitude of 17.5 at peak (19-20 in the tail). Three dithered sets of BVI photometry of 180s each will provide us with a S/N of 50 at peak and 20 in the tail of the light curve. Observing every 3 nights to obtain a high- quality light curve would require 35 min (including overheads) per SN. For 5 SNe over a 7 week period this 48 hrs of time (6 effective nights). We will also make use of the IR capabilities at YALO to acquire simultaneous H-band data. Calibration Justification ------------------------- Real_Time_Justification Additional Comments ------------------- 9421( 6) - 03/18/03 08:27 - [ 4] ------------------------------------------------------------------------------------ 9421( 6) - 03/18/03 08:27 - [ 5] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NSNF1 EXT-STAR, SUPERNOVA RA= 8H 08M 26.34S +/- 0.01S, J2000 Z = 0.05 V = 17.0+/-1.0 TYPE IA DEC=12D 19' 56.13" +/- 0.5" B-V = 0.25+/-0.25 Coordinate Source: Other_Source: The rabbit from the hat... 2 NSNF2 EXT-STAR, SUPERNOVA RA= 8H 08M 26.34S +/- 0.01S, J2000 Z = 0.05 V = 17.0+/-1.0 TYPE IA DEC=12D 19' 56.13" +/- 0.5" B-V = 0.25+/-0.25 Coordinate Source: Other_Source: The rabbit from the hat... 3 NSNF3 EXT-STAR, SUPERNOVA RA= 10H 55M 22.47S +/- 0.01S, J2000 Z = 0.05 V = 17.0+/-1.0 TYPE IA DEC=-07D 39' 12.45" +/- 0.5" B-V = 0.25+/-0.25 Coordinate Source: Other_Source: The rabbit from the hat... 4 NSNF4 EXT-STAR, SUPERNOVA RA= 8H 08M 26.34S +/- 0.01S, J2000 Z = 0.05 V = 17.0+/-1.0 TYPE IA DEC=12D 19' 56.13" +/- 0.5" B-V = 0.25+/-0.25 Coordinate Source: Other_Source: The rabbit from the hat... 5 NSNF5 EXT-STAR, SUPERNOVA RA= 14H 0M 31.45S +/- 0.01S, J2000 Z = 0.05 V = 17.0+/-1.0 TYPE IA DEC=-28D 52' 32.70" +/- 0.5" B-V = 0.25+/-0.25 Coordinate Source: Other_Source: The rabbit from the hat... 9421( 6) - 03/18/03 08:27 - [ 6] Visit: 01 Visit Priority: Visit Requirements: SCHED 100% BETWEEN 10-Mar-2003 AND 11-Mar-2003 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 NSNF1 STIS/C ACQ 50CCD MIRROR ACQTYPE=POINT 1 10.0 S CD ------------------------------------------------------------------------------------------------------------------------------------ 2 NSNF1 STIS/C ACCUM 52X0.2E G430L 4300 CR-SPLIT=2,BINAXIS1=2 1 35 M EXPAND MAX DUR 200% CD 1 ------------------------------------------------------------------------------------------------------------------------------------ 3 NSNF1 STIS/N ACCUM 52X0.2 G230L 2376 1 2600 S MAX DUR 150% UV-MAM A Comments: fill orbit #2 ------------------------------------------------------------------------------------------------------------------------------------ 9421( 6) - 03/18/03 08:27 - [ 7] Visit: 02 Visit Priority: Visit Requirements: SCHED 100% BETWEEN 17-Mar-2003 AND 18-Mar-2003 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 NSNF2 STIS/C ACQ 50CCD MIRROR ACQTYPE=POINT 1 10.0 S CD ------------------------------------------------------------------------------------------------------------------------------------ 2 NSNF2 STIS/C ACCUM 52X0.2E G430L 4300 CR-SPLIT=2,BINAXIS1=2 1 35 M EXPAND MAX DUR 200% CD 1 ------------------------------------------------------------------------------------------------------------------------------------ 3 NSNF2 STIS/N ACCUM 52X0.2 G230L 2376 1 2600 S MAX DUR 150% UV-MAM A Comments: fill orbit #2 ------------------------------------------------------------------------------------------------------------------------------------ 9421( 6) - 03/18/03 08:27 - [ 8] Visit: 03 Visit Priority: Visit Requirements: SCHED 100% BETWEEN 17-Mar-2003 AND 18-Mar-2003 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 NSNF3 STIS/C ACQ 50CCD MIRROR ACQTYPE=POINT 1 10.0 S CD ------------------------------------------------------------------------------------------------------------------------------------ 2 NSNF3 STIS/C ACCUM 52X0.2E G430L 4300 CR-SPLIT=2,BINAXIS1=2 1 35 M EXPAND MAX DUR 200% CD 1 ------------------------------------------------------------------------------------------------------------------------------------ 3 NSNF3 STIS/N ACCUM 52X0.2 G230L 2376 1 2600 S MAX DUR 150% UV-MAM A Comments: fill orbit #2 ------------------------------------------------------------------------------------------------------------------------------------ 9421( 6) - 03/18/03 08:27 - [ 9] Visit: 04 Visit Priority: Visit Requirements: SCHED 100% BETWEEN 24-Mar-2003 AND 25-Mar-2003 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 NSNF4 STIS/C ACQ 50CCD MIRROR ACQTYPE=POINT 1 10.0 S CD ------------------------------------------------------------------------------------------------------------------------------------ 2 NSNF4 STIS/C ACCUM 52X0.2E G430L 4300 CR-SPLIT=2,BINAXIS1=2 1 35 M EXPAND MAX DUR 200% CD 1 ------------------------------------------------------------------------------------------------------------------------------------ 3 NSNF4 STIS/N ACCUM 52X0.2 G230L 2376 1 2600 S MAX DUR 150% UV-MAM A Comments: fill orbit #2 ------------------------------------------------------------------------------------------------------------------------------------ 9421( 6) - 03/18/03 08:27 - [ 10] Visit: 05 Visit Priority: Visit Requirements: SCHED 100% BETWEEN 24-Mar-2003 AND 25-Mar-2003 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 NSNF5 STIS/C ACQ 50CCD MIRROR ACQTYPE=POINT 1 10.0 S CD ------------------------------------------------------------------------------------------------------------------------------------ 2 NSNF5 STIS/C ACCUM 52X0.2E G430L 4300 CR-SPLIT=2,BINAXIS1=2 1 35 M EXPAND MAX DUR 200% CD 1 ------------------------------------------------------------------------------------------------------------------------------------ 3 NSNF5 STIS/N ACCUM 52X0.2 G230L 2376 1 2600 S MAX DUR 150% UV-MAM A Comments: fill orbit #2 Coordinator ------------------------------------------------------------------------------------------------------------------------------------ 9421( 6) - 03/18/03 08:27 - [ 11] Summary Form for Proposal 9421 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 50CCD 52X0.2E1 52X0.2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT BINAXIS1=2 CR-SPLIT=2 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements SCHED 100% BETWEEN 10-Mar-2003 AND 11-Mar-2003 EXPAND MAX DUR 200% MAX DUR 150% SCHED 100% BETWEEN 17-Mar-2003 AND 18-Mar-2003 SCHED 100% BETWEEN 24-Mar-2003 AND 25-Mar-2003 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G430L G230L ------------------------------------------------------------------------------------------------------------------------------------ Target Names NSNF1 NSNF2 NSNF3 NSNF4 NSNF5 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 4300 2376 ------------------------------------------------------------------------------------------------------------------------------------