Proposal_Information ! Section 4 Title: DARK MATTER AT VERY LARGE RADII IN M31 Proposal_Category: GO Scientific_Category: Galaxies & Clusters Cycle: 5 Investigators PI_name: Prof. David A. Turnshek PI_Institution: University of Pittsburgh CoI_Name: Dr. Stefano Casertano CoI_Institution: STScI (ESA) Contact: N (designate at most one contact) Abstract: ! Free format text (please update) 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. Questions ! Free format text (please update) Observing_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). Real_Time_Justification: None Calibration_Justification: ! Move appropriate text from Real_Time_Justification Additional_Comments: Fixed_Targets ! Section 5.1 Target_Number: 1 Target_Name: Q0038+327 Alternate_Names: Description: GALAXY, QSO Position: RA= 00H 40M 43.54S +/- 1S, !Most common specification format is DEC= 32D 58' 33.15" +/- 1", ! RA=0H 0M 0.00S +/- 0S, PLATE-ID=01H5 Equinox: 2000 RV_or_Z: Z=0.179 RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch: 1950 Annual_Parallax: 0 Flux: V=18.25, ! Include at least V and B-V B-V=0.45 Comments: ! This is a template for a single visit containing a single exposure ! Repeat exposure and visit blocks as needed Visits ! Section 6 Visit_Number: 1 Visit_Requirements: ! Section 7.1 On_Hold_Comments: Exposure_number: 10 Target_Name: Q0038+327 Config: FOS/RD Opmode: ACQ/BINARY Aperture: 4.3 Sp_Element: MIRROR Wavelength: Optional_Parameters: Number_of_iterations: 1 Time_Per_Exposure: 39S Special_Requirements: ONBOARD ACQ FOR 20 Comments: Exposure_number: 20 Target_Name: Q0038+327 Config: FOS/RD Opmode: ACQ/PEAK Aperture: 0.25x2.0 Sp_Element: G270H Wavelength: Optional_Parameters: SCAN-STEP-X=.057, SEARCH-SIZE-X=9, SEARCH-SIZE-Y=1 Number_of_iterations: 1 Time_Per_Exposure: 28S Special_Requirements: ONBOARD ACQ FOR 30 Comments: Exposure_Number: 30 ! Section 6.5 Target_Name: Q0038+327 Config: FOS/RD Opmode: ACCUM Aperture: 0.25x2.0 Sp_Element: G270H Wavelength: 2700 Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 3040S Special_Requirements: ! Section 7.2 Comments: Exposure_Number: 40 ! Section 6.5 Target_Name: WAVE Config: FOS/RD Opmode: ACCUM Aperture: 0.25x2.0 Sp_Element: G270H Wavelength: 2700 Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: DEF Comments: NO GAP between expoure numbers 30 and 40 Data_Distribution ! Defaults indicated; change if desired Medium: 8MM ! 8MM or 6250BPI or 1600BPI Blocking_Factor: 10 ! 10 or 1 ! Only astronomers with very old 9- ! track tape drives should consider ! a blocking factor of 1 Ship_To: PI_Address ! STSCI or PI_Address or ! PI Address from Phase I is: ! ! Department of Physics and Astronomy ! Pittsburgh, PA 15260 ! ! Ship_Via: UPS ! UPS (2-day) or OVERNIGHT ! Overnight shipping done at PI expense Recipient_Email: ! Needed if Ship_To: is not PI_Address ! ! Let us know what you think of this template and software! ! Please send a list of your likes and dislikes to your Program Coordinator