9374( 3) - 07/15/02 14:02 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9374 Version: 3 Check-in Date: 15-Jul-2002 14:01:24 1.Proposal Title: The FUV Flux Irradiating the Surfaces of Protostellar Disks ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 11 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Edwin Bergin Smithsonian Institution Astrophysical Observatory CoI: Dr. Chunhua Qi Smithsonian Astrophysical Observatory N CoI: Dr. Nuria Calvet Smithsonian Astrophysical Observatory N ------------------------------------------------------------------------------------ 5. Abstract We propose to use STIS to determine the Far-Ultraviolet (FUV) radiation field in 3 proto-planetary disk systems. These systems: LkCa 15, GM Aur, and DM Tau, are among a handful of sources that can be subjected to detailed chemical studies with the current generation of millimeter-wave instruments. Such studies have found that the disks have a rich molecular chemistry, which appears to be controlled by the FUV radiation field (Qi 2001; Dutrey et al 1997; Kastner et al 1997). These observations will allow, for the first time, a firm characterization of the FUV radiation field impinging on the surfaces of circumstellar disks. Knowledge of the FUV field for each object will allow for theoretical chemical models to be created specific to each object and compared to observations. Since these objects will remain, for some time, the main templates for chemical studies of extra-solar disks this project will provide the real UV data required to push theory forward. Given that molecules are excellent probes of their environment, the new information will place better constraints on the virtually unknown vertical structure of proto-planetary disks. This project is unique in scope and will increase our limited understanding of disk chemical evolution, but also improve our knowledge of uncertain physical processes, such as the possible dissipation of outer disks by photo-evaporation and on the timescales of dust grain growth. ------------------------------------------------------------------------------------ 9374( 3) - 07/15/02 14:02 - [ 2] Observations Description ------------------------ We propose to use STIS/MAMA with grating G140L and an aperture of 52x2 to obtain the FUV flux of targets LKCA-15, GM-AUR, and DM-TAU. With the low resolution grating and the large aperture, we expect to get fluxes with signal to noise ratios (S/N) >= 10 over the entire the FUV region in reasonable exposure times. We also include one observation with grating G230L and similar aperture of the sources, to be able to obtain the NUV and so characterize the entire UV spectrum of the targets. We have estimated FUV flux levels assuming that the luminosity between 1100 Angstrom and 1600 Angstrom scales with the accretion luminosity as ~ 0.05 L_acc and that the spectrum is relatively flat, as suggested by STIS spectra of intermediate mass T Tauri stars (Calvet et al., in preparation). We get the accretion luminosity L_acc = G M \mdot / R from the measured mass accretion rate \mdot (Hartmann et al. 1998), and mass M and radius R from the position of the target in the HR diagram (using spectral types; luminosities are from Kenyon & Hartmann 1995). The reddening has been taken from Kenyon & Hartmann (1995) and Gullbring et al. (1998). To estimate the flux levels at the NUV we have used the accretion shock models of Calvet & Gullbring (1998) for given accretion luminosity, which reproduce the NUV IUE fluxes of T Tauri stars (Gullbring et al. 2001), and scaled them to the unreddened U magnitude of the targets. We have then reddened the model fluxes and used them as input spectra in the ETC calculator. For GW-AUR, with A_V = 0.3, the estimated FUV flux level is ~ 8 * 10^-15 erg cm^-2 s^-1 , A^-1, for L_acc = 0.07 L(sun). The ETC indicates that S/N ~ 26 at 1600 Angstrom can be achieved with a 60 minute exposure. For DM-TAU, with A_V = 0.9, the estimated FUV flux level is ~ 3 * 10^-15 erg cm^-2 s^-1 A , ^-1, for L_acc = 0.09 L(sun). The ETC indicates that S/N ~ 16 at 1600 Angstrom can be achieved with a 60 minute exposure. Input shock model spectra for the ETC, yield a S/N of 60 for GM-AUR and 40 for DM-TAU at 2400 Angstrom for 30 minute exposures. So, we are requesting 2 orbits for each one of these targets (assuming ~ 45 minutes of science exposure time per orbit). LKCA-15 has a factor of 5 lower accretion luminosity than the other two targets, and a moderate reddening, A_V = 0.6. Scaling from the accretion luminosity, we estimate an FUV flux level of ~ 4 * 10^-16 erg cm^-2 s^-1 A^-1, for L_acc = 0.02 L(sun). An exposure of 180 minutes yields S/N ~ 10 at 1600 Angstrom. The input shock model spectrum results in S/N ~ 20 at 2300 Angstrom for a 40 minute exposure. Therefore, we request 5 orbits for this target. Real Time Justification ----------------------- None None Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9374( 3) - 07/15/02 14:02 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 LKCA-15 STAR, T TAURI STAR RA=04H 39M 17.73S +/- 0.3", J2000 V = 12.4+/-0.5 DEC=22D 21' 3.8" +/- 0.3", U = 14.6+/-0.5 PLATE-ID=000L Coordinate Source: GUIDE_STAR_CATALOG 2 GM-AUR STAR RA=4H 55M 10.97S +/- 0.2", J2000 V = 12+/-0.5 DEC=30D 21' 59.7" +/- 0.2", U = 13+/-1 PLATE-ID=02TR Coordinate Source: GUIDE_STAR_CATALOG 3 DM-TAU STAR, T TAURI STAR RA=4H 33M 48.72S +/- 0.2", J2000 V = 14+/-0.5 DEC=18D 10' 10.1" +/- 0.2", U = 15+/-1 PLATE-ID=000P Coordinate Source: GUIDE_STAR_CATALOG 9374( 3) - 07/15/02 14:02 - [ 4] Visit: 01 Visit Priority: Visit Requirements: BETWEEN 01-Feb-2003 AND 15-Feb-2003 BETWEEN 01-Jul-2003 AND 31-Dec-2005 On Hold Comments: Additional Comments: The BETWEEN requirement is included to coordinate with ground based mid- infrared observations of the target Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 LKCA-15 STIS/C ACQ F28X50O MIRROR 1 15 S CD III ------------------------------------------------------------------------------------------------------------------------------------ 20 LKCA-15 STIS/N ACCUM 52X2 G230L 2376 1 45 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 30 LKCA-15 STIS/F ACCUM 52X2 G140L 1425 1 45 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 40 LKCA-15 STIS/F ACCUM 52X2 G140L 1425 1 45 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 50 LKCA-15 STIS/F ACCUM 52X2 G140L 1425 1 45 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 51 LKCA-15 STIS/F ACCUM 52X2 G140L 1425 1 45 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 9374( 3) - 07/15/02 14:02 - [ 5] Visit: 02 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 GM-AUR STIS/C ACQ F28X50O MIRROR 1 10 S CD III ------------------------------------------------------------------------------------------------------------------------------------ 20 GM-AUR STIS/N ACCUM 52X2 G230L 2376 1 10 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 30 GM-AUR STIS/F ACCUM 52X2 G140L 1425 1 25 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 40 GM-AUR STIS/F ACCUM 52X2 G140L 1425 1 45 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 9374( 3) - 07/15/02 14:02 - [ 6] Visit: 03 Visit Priority: Visit Requirements: BETWEEN 01-Feb-2003 AND 15-Feb-2003 BETWEEN 01-Jul-2003 AND 31-Dec-2005 On Hold Comments: Additional Comments: The BETWEEN requirement is included to coordinate with ground based mid- infrared observations of the target Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 DM-TAU STIS/C ACQ F28X50O MIRROR 1 30 S CD III ------------------------------------------------------------------------------------------------------------------------------------ 20 DM-TAU STIS/N ACCUM 52X2 G230L 2376 1 10 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 30 DM-TAU STIS/F ACCUM 52X2 G140L 1425 1 18 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 40 DM-TAU STIS/F ACCUM 52X2 G140L 1425 1 45 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 9374( 3) - 07/15/02 14:02 - [ 7] Summary Form for Proposal 9374 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50OIII 52X2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/NUV-MAMA STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 01-Feb-2003 AND 15-Feb-2003 BETWEEN 01-Jul-2003 AND 31-Dec-2005 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G230L G140L ------------------------------------------------------------------------------------------------------------------------------------ Target Names LKCA-15 GM-AUR DM-TAU ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 2376 1425 ------------------------------------------------------------------------------------------------------------------------------------