7762( 2) - 07/27/99 14:08 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 7762 Version: 2 Check-in Date: 29-Aug-1997 17:21:18 1.Proposal Title: The Gaseous Environment of the Ursa Minor Dwarf Spheroidal Galaxy ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 7 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Edward Olszewski University of Arizona CoI: Dr. Jill Bechtold Steward Observatory, University of Arizona N ------------------------------------------------------------------------------------ 5. Abstract We propose to probe the interstellar gas content of the Ursa Minor dwarf spheroidal galaxy. We have discovered a V=18.66 QSO at approximately 1 core radius from the center of UMi. We will use the FOS to look for EUV absorption lines from gas in UMi. This technique complements previous unsuccessful searches for gas in dSph. These galaxies should have large reservoirs of gas: some of them ( e.g. Carina and Leo I), made a significant second generation of stars a few Gyr ago, and since their gravitational potential is dominated by dark matter, they should be able to retain an observable amount of gas, built up through infall or stellar mass loss. We intend to use the G270H grating, which allows us to observe the Mg II doublet, Mg I, Fe II lines, and weak Fe I, Al I, Mn II, and Ti II lines. Because of the patchy nature of the Milky Way high velocity halo gas, we will also observe a brighter, nearby QSO (2^degrees away) to ensure that we can ascribe any detections to UMi. Finally we will take a low resolution, G160L, spectrum to see if the UMi QSO is clear of optically thick Lyman limits for future spectroscopy of more highly ionized species. ------------------------------------------------------------------------------------ 7762( 2) - 07/27/99 14:08 - [ 2] Observations Description ------------------------ def\nhi =1.0truecm Exposure times were estimated using the STSDAS SYNPHOT software in IRAF, normalizing a power law spectrum of slope +1 to the measured B magnitude. We used the published QSO Key Project spectra (Bahcall et al. 1993) obtained from the archives to calculate the S/N needed to attain a given equivalent-width limit: one needs S/N~30 per DIODE to get an equivalent-width limit of ~0.2Angstrom\ (3- Sigma). We will use the 1^'' aperture since the resolution is little affected for point sources, and the overhead for acquisition is less. We note that scattered light will be negligible, since the central surface brightness of UMi is 25.1 mag arcsec^-2, and there are no objects as bright as the QSO within 25 arcsec. \oneskip 1.underlineUMI-COS253 = QSO 1508+673: nhi10920 sec (182 min) actual exposure with FOS/RD, G270H and 1.0^'' aperture. This will cover the 2225 - 3280 Angstrom\ spectrum at about 100 km/sec resolution, to look for absorption lines from the ISM of UMi, at v(helio) = -250 km/sec. Lines of Mg II, Mg I, Fe II, and Mn II are expected. An equivalent width limit of about 0.2 Angstrom will be achieved. (It will take 5 orbits to achieve this exposure time: see below.) 2.underline B2 1503+691: nhi2700 sec (45 min) exposure with FOS/RD, G270H and 1.0^'' aperture. This brighter (V = 17) QSO will be used to look for absorption from Galactic gas, particularly high velocity gas in the Galactic halo, in the direction of UMi. Signal-to-noise will be comparable to UMI-COS253 spectrum. (2 orbits: see below.) 3.underlineUMI-COS253 = QSO 1508+673: nhi2760 sec (46 min)exposure with FOS/BL, G160L and 4.3^'' circular aperture. This low dispersion spectrum, covering 1150 - 2400 Angstrom will be used to look for optically thick Lyman limits from intervening metal-line systems for wavelengths short of 1550 Angstrom. This low resolution spectrum will also be used to estimate exposure times of follow-up high dispersion spectroscopy. We estimate using SYNPHOT that we will achieve 27 counts at 1250 Angstrom\ and 190 counts at 2200 Angstrom adequate for finding the strong Lyman limits features. (2 orbits: see below.) \oneskip We calculated orbits as follows: indentFirst object, UMi QSO, red side: Guidestar acq 8m; aperture acq 41m; 2m exposure; 6 m readout; end of orbit 1. Orbit 2--5: reacq 6m; 45m exposure; 6m readout. 182 m=10, 920 sec total exposure. This will give 1000 counts/diode at Mg II. Start change to blue side, using all 39 m of occulted time indentChange sides of FOS: need 6m of unocculted time to finish the side change of FOS; guidestar reacq 6m; 41 min of aperture acquisition; end orbit 1. Then Orbit 2: 6 m reacq; 45m exposure; 6m readout. Begin change back to red side while moving telescope, using all 39m of occulted time. ControlQSO: 6 m to finish change to red side; 8 m to acquire guidestar; 41 m of aperture acq; end of orbit 1. Orbit 2: 6m of reacq; 46m exposure; 6m readout. This will give 1000 counts/diode at Mg II. Real Time Justification ----------------------- None. We will supplement these observations with high dispersion optical spectroscopy at Ca II H&K obtained at the Multiple Mirror Telescope. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 7762( 2) - 07/27/99 14:08 - [ 3] Data Distribution Paper Products: Media: DAT Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 7762( 2) - 07/27/99 14:08 - [ 4] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 QSO1508+673 GALAXY, QSO RA=15H 08M 40.41S +/- 0.1S, J2000 Z=1.7 V = 18.6+/-0.5 DEC=+67D 17' 47.52" +/- 0.5", B-V = 0.2+/-0.1 PLATE-ID=00A9 2 QJ0640-5031 GALAXY, QSO RA=06H 40M 56.00S +/- 0.1S, DEC= J2000 Z=0.2 V = 16.7+/-0.5 -50D 31' 46.0" +/- 0.5", PLATE- B-V = 0.2+/-0.1 ID=01W3 7762( 2) - 07/27/99 14:08 - [ 5] Visit: 01 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 QSO1508+673 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 6.0 S ONBOARD ACQ FOR 2 CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 QSO1508+673 STIS/F ACCUM 52X0.5 G140L 1425 1 40.0 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7762( 2) - 07/27/99 14:08 - [ 6] 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 QJ0640-5031 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 2.5 S ONBOARD ACQ FOR 2-4 CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 QJ0640-5031 STIS/C ACQ/PEA 0.2X0.2 MIRROR 1 2.5 S ONBOARD ACQ FOR 3-4 CD K ------------------------------------------------------------------------------------------------------------------------------------ 3 QJ0640-5031 STIS/F ACCUM 0.2X0.2 E140M 1425 1 32.0 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 4 QJ0640-5031 STIS/F ACCUM 0.2X0.2 E140M 1425 3 45.0 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7762( 2) - 07/27/99 14:08 - [ 7] Visit: 03 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 QJ0640-5031 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 2.5 S ONBOARD ACQ FOR 2-4 CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 QJ0640-5031 STIS/C ACQ/PEA 0.2X0.2 MIRROR 1 2.5 S ONBOARD ACQ FOR 3-4 CD K ------------------------------------------------------------------------------------------------------------------------------------ 3 QJ0640-5031 STIS/F ACCUM 0.2X0.2 E140M 1425 1 32.0 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 4 QJ0640-5031 STIS/F ACCUM 0.2X0.2 E140M 1425 2 45.0 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7762( 2) - 07/27/99 14:08 - [ 8] Summary Form for Proposal 7762 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 52X0.5 0.2X0.2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ACQ/PEAK ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 2 ONBOARD ACQ FOR 2-4 ONBOARD ACQ FOR 3-4 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G140L E140M ------------------------------------------------------------------------------------------------------------------------------------ Target Names QSO1508+673 QJ0640-5031 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 1425 ------------------------------------------------------------------------------------------------------------------------------------