7730( 8) - 05/14/98 13:53 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 7730 Version: 8 Check-in Date: 14-May-1998 13:52:30 1.Proposal Title: DARK MATTER AT VERY LARGE RADII IN M31 ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO/CAR 5 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: DAVID A. TURNSHEK UNIVERSITY OF PITTSBURGH CoI: Dr. Stefano Casertano STScI (ESA) N ------------------------------------------------------------------------------------ 5. Abstract We propose to probe the dark matter distribution of M31 far from the center by observing intervening absorption from the MgII doublet (lambda 2800) in the spectrum of one background QSO located in a geometrically optimal position. HST observations are required because this feature is in a wavelength range not accessible from the ground, and the QSO magnitudes and expected strength of absorption make IUE observations unfeasible. Other ground-accessible features, notably CaII, are expected to be too weak for detection. With these observations, we will extend the rotation curve of M31 to about 6 Holmberg radii, a factor of 4 farther than the HI rotation curve obtained for M31 itself and 2.5 times farther than has been obtained from the ground for any bright galaxy. This observation will open a new territory in the study of the dark matter distribution for galaxies, and specifically address the question of where the dark matter halo around individual galaxies stops: whether it ends just beyond the range of deep HI observations or it continues a factor of several further out. In the latter case, halos of individual galaxies may be responsible for a larger fraction of the dark matter found on larger scales than otherwise believed. ------------------------------------------------------------------------------------ 7730( 8) - 05/14/98 13:53 - [ 2] Observations Description ------------------------ We propose to obtain an FOS-G270H spectrum of 1 QSO. The goal is to detect and measure the velocity of any MgII absorption lines from foreground material at essentially zero redshift. We expect an equivalent width > 0.2 Angstrom; for a > 3-sigma detection, a S/N of 30 per detection element is therefore required. The exposure time has been calculated by extrapolating the observed visual magnitude into the UV with a nu^-1 power law, with the result that 2 orbits should be required to get a S/N=30 spectrum of Q0038+327 (V=18.06, z=0.179). The expected accuracy of the velocity for the rotation curve is approximately 0.1 diode (or 0.4 1/4-substepped pixels) which is 22 km/s (1-sigma). This is adequate for dynamical calculations. Target has now been selected from 1 of 3 QSOs as Q0038+327 (P. Stanley 28 Dec 95). Spectrum will now be obtained using STIS-G230LB (E. Monier for D. Turnshek 8 Aug 97). Real Time Justification ----------------------- None Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 7730( 8) - 05/14/98 13:53 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 Q0038+327 GALAXY, QSO RA= 00H 40M 43.54S +/- 1S, DEC= 2000 Z=0.179 V = 18.25 32D 58' 33.15" +/- 1", PLATE- B-V = 0.45 ID=01H5 7730( 8) - 05/14/98 13:53 - [ 4] 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 Q0038+327 STIS/C ACQ F28X50L MIRROR 1 15 S ONBOARD ACQ FOR 20 CD P ------------------------------------------------------------------------------------------------------------------------------------ 20 Q0038+327 STIS/C ACCUM 52X0.2 G230MB 2836 CR-SPLIT=NO 1 2400 S CD ------------------------------------------------------------------------------------------------------------------------------------ 40 WAVE STIS/C ACCUM 52X0.2 G230MB 2836 1 DEF CD ------------------------------------------------------------------------------------------------------------------------------------ 60 Q0038+327 STIS/C ACCUM 52X0.2 G230MB 2836 CR-SPLIT=NO 1 2400 S EXPAND; POS TARG 0.0,+1.0 CD ------------------------------------------------------------------------------------------------------------------------------------ 7730( 8) - 05/14/98 13:53 - [ 5] Summary Form for Proposal 7730 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 52X0.2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO/CAR ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 20 EXPAND; POS TARG 0.0,+1.0 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G230MB ------------------------------------------------------------------------------------------------------------------------------------ Target Names Q0038+327 WAVE ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 2836 ------------------------------------------------------------------------------------------------------------------------------------