Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 4512c Report Date: 09-May-96:19:40 Version: ********** Check-in Date: ********** 1.Proposal Title: NGC 628: COULD IT BE A PROTOTYPE "QSO ABSORPTION-LINE SYSTEM" - CYCLE 3 SUPPLEMENTAL ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID QUASARS & AGN GO Sub Category QUASAR ABSORPTION ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Frank H Briggs 3170 U.S.A. ------------------------------------------------------------------------------------ 7. Abstract The ScI galaxy NGC 628 is embedded in a giant, warped disk of neutral gas whose size nearly matches the cross-section inferred for the intervening absorbers identified in the spectra of high redshift QSOs. The galaxy may resemble the narrow, low- ionization systems identified by the MgII doublet 2796,2802 and the other common ISM lines of FeII, SiII, CII, OI, etc. Fortuitously, a background QSO lies behind the the most extended part of the gas distribution, and the QSO continuum can be used to probe the gas for the presence of metals by searching for the MgII doublet in absorption at the known redshift of this fore-ground galaxy. The observation will place strict constraints on the history of stellar populations and metal enrichment of these galactic outskirts that are not detectable in optical emission but comprise one tenth of the galaxy's neutral gas content. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 4.58 par: 0 10. Num targs pri: 1 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: FOS ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 4512c PI: Frank H Briggs Proposal Title: NGC 628: COULD IT BE A PROTOTYPE "QSO ABSORPTION-LINE SYSTEM" - CYCLE 3 SUPPLEMENTAL ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Pi Frank H Briggs UNIVERSITY OF PITTSBURGH U.S.A. David A Turnshek UNIVERSITY OF PITTSBURGH U.S.A. ------------------------------------------------------------------------------------ 2. Scientific Justification. ------------------------------------------------------------------------------------ 3. Description of proposed observations. This request is for a single FOS G270H spectrum of a QSO at resolution R=1000 yielding a signal-to-noise ratio of 30 per resolution element. The 1 arcsec FOS aperture will be used. The exposure time will be 275M. ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. The only way to observe the spectrum of this background QSO at the expected position of the MgII2800 absorption doublet is to obtain observations in the UV. This region of the UV is not accessible from the ground. This QSO is not bright enough for this observation to be performed with IUE. Using the FOS G270H mode and 1 arcsec aperture, an exposure time of 275M is required to obtain a spectrum with a signal-to-noise ratio of 30 per resolution element at the expected position of the MgII2800 doublet. With the aperture we propose to use the resolution will be R=1000 which is 5 pixels in 1/4-diode substepping mode (or 2.8 Angstroms resolution). The 1-sigma error in an absorption line equivalent width measurement will be approximately 0.1 Angstrom. (This sensitivity is high enough to insure that MgII with "depleted abundances" typical of neutral clouds in the Milky Way would be detected at the 5-sigma level; a non-detection would imply that the abundance of MgII is less than 1/300 solar-abundance with 95% confidence.) This exposure time was determined using the FOS simulator software on SCIVAX at STScI. ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. Page 3 ------------------------------------------------------------------------------------ 7. Data reduction and analysis plans. The data will be reduced and processed on SUN workstations using the software available in IRAF/STSDAS when possible. The spectra will be examined for the presence of MgII (and MgI) absorption. A continuum level will be fit to the spectrum and the equivalent widths of the MgII lines measured. The lines will be interpreted in the context of the curve of growth in Figure 2. If the lines are substantially stronger than predicted, then there must be an additional high- velocity-dispersion component of halo clouds present and a range of more complex models will be considered. If no detection is made, limits will be placed on the metal abundances in the gas. The constraints on the history of this outlying material will help in deciphering the dynamics at work in this galaxy: The absence of metals could indicate a very real possibility of accretion of primordial material from outside the galaxy or perhaps that stars have never formed in this outlying gas. The detection of metals implies that star formation and evolution have already occured, either in an early burst of star formation in the outer part of NGC628 or in a gas-rich dwarf galaxy that has been captured and tidally dispersed as it is assimilated into the disk of NGC 628. Clearly, even a crude knowlege of the metal abundances in this material would restrict the range of possible scenarios. ------------------------------------------------------------------------------------ 8. Additional comments or special requests. ------------------------------------------------------------------------------------ 9. Description of previous HST work. For PI Briggs: No HST time or archival data has been received. For co-I Turnshek: The GTO program 1146 entitled "Spectroscopic Studies of Several High Redshift BAL QSOs" has been reduced in scope due to the problems with HST. However, FOS G270H observations of one BAL QSO have been made (Korista et al. 1992) and an FOS G190H observation is scheduled. The program is a collaboration between Weymann (PI), Burbidge, Cohen, Foltz, Hartig, Junkkarinen, Morris, and Turnshek. This program is not directly related to the project proposed here. The GTO program 1145 entitled "Imaging and Spectroscopy of the Low Redshift BAL QSO PG 1700+518" has been deferred until the imaging capabilities of HST are fully restored (estimated Cycle 5). This program is not related to the project proposed here. The GO key project program 2424 (and continuation 3353) entitled "Quasar Absorption Line Survey" is a collaboration between Bahcall (PI), Bergeron, Boksenberg, Hartig, Jannuzi, Sargent, Savage, Schneider, Turnshek, Weymann, and Wolfe. This Cycle 1, 2, and 3 program is designed to redshifted QSO absorption line systems that are selected in the observations of bright QSOs. It is program that is complementary to the current proposal but fundamentally different in goals and approach. The GO program 2649 entitled "Spectrophotometry of the Lensed Clover Leaf BAL QSO 1413+11" is a collaboration between Turnshek (PI) and Lupie. This Cycle 1 program is not related to the project proposed here. The GO program 3660 entitled "The Level of Ionization and Chemical Composition of QSO BAL Region Gas" is a collaboration between Turnshek (PI), Espey, and Weymann. This Cycle 2 program is not related to the project proposed here. "HST-FOS and Ground-Based Observations of the BAL Quasar 0226-1024" by Korista, Weymann, Morris, Kopko, Turnshek, Hartig, Foltz, Burbidge, and Junkkarinen, ApJ, in press, 1992. "The HST Quasar Absorption Line Key Project I. First Observational Results Including Lyman -ALPHA and Lyman-Limit Systems" by Bahcall, Bergeron, Boksenberg, Hartig, Jannuzi, Kirhakos, Sargent, Savage, Schneider, Turnshek, Weymann, and Wolfe, ApJ, in press, 1992. "The HST Quasar Absorption Line Key Project II. Data Calibration and Absorption Line Selection" by Schneider, Hartig, Jannuzi, Kirhakos, Saxe, Weymann, Bahcall, Bergeron, Boksenberg, Sargent, Savage, Turnshek, and Wolfe, ApJ, submitted, 1992. Page 4 ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). Institutional support includes academic salary for the PI and co-I. The University of Pittsburgh will also supply routine secretarial assistance, administrative support, and the office space required for this project. In addition, the University has a pool of graduate and undergraduate research assistants who can be called upon to perform work for this project, providing that the work can be charged to project funds. The Department of Physics and Astronomy operates a SUN SPARC2 which acts as a file server for client workstations owned by various research groups. Other departmental facilities include a laser printer, a CD reader, and an exabyte 8mm tape drive. The department pays for a maintenance contract on its computer hardware. However, the departmental computing facilities are not generally used by the various physics and astronomy research groups (except for the file server capability). Their primary purpose is as an educational tool. However, they would prove to be a good backup in the event that, for example, the computing facilities of the astronomy/astrophysics group go down. Research groups must purchase and maintain their computing facilities with project funds. ------------------------------------------------------------------------------------ 11. Address Information Name: Frank H Briggs Category: PI Institution: UNIVERSITY OF PITTSBURGH Address: Department of Physics and Astronomy Allen Hall ALLEGHANY OBSERVATORY City: Pittsburgh State: PA Zip Code: 15260 Country: U.S.A. Telephone: 412-624-9026/9000 Telex (or e-mail): None ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 4512c [ 5] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial |Acqui|FLX| Flux data No | Name | Description | Position |Eqnx | Vel. |Prblm|REF| | | | | | | | | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC628Q1 E,313 RA = 01H 36M 03.9S +/- 0.1S, 2000 Z = 1 V = 19.0 DEC = +15D 37' 58" +/- 1.0" 2.149 2 F-CONT(2700) = 1.3 E-16 ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 4512c [ 6] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC628Q1 FOS/RD ACQ/ 4.3 MIRROR SEARCH-SIZE-X=1 1 12.0S 30 1 1 CYCLE 3 / 1-2 PEAK SEARCH-SIZE-Y=3 ONBOARD ACQ FOR SCAN-STEP-Y=1.4 1.1 ------------------------------------------------------------------------------------------------------------------------------------ 1.1 NGC628Q1 FOS/RD ACQ/ 1.0 MIRROR SEARCH-SIZE-X=6 1 20.0S 30 1 1 ONBOARD ACQ FOR PEAK SCAN-STEP-X=0.7 1.2 SEARCH-SIZE-Y=2 SCAN-STEP-Y=0.7 ------------------------------------------------------------------------------------------------------------------------------------ 1.2 NGC628Q1 FOS/RD ACQ/ 0.5 MIRROR SEARCH-SIZE-X=3 1 40.0S 30 1 1 ONBOARD ACQ FOR 2 PEAK SCAN-STEP- X=0.35 SEARCH-SIZE-Y=3 SCAN-STEP- Y=0.35 ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC628Q1 FOS/RD ACCUM 1.0 G270H 1 271M 30 2 1 ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 4512c [ 7] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOS/RD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/PEAK ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SEARCH-SIZE-X=1 SEARCH-SIZE-Y=3 SCAN-STEP-Y=1.4 SEARCH-SIZE-X=6 SCAN-STEP-X=0.7 SEARCH-SIZE-Y=2 SCAN-STEP-Y=0.7 SEARCH-SIZE-X=3 SCAN-STEP-X=0.35 SCAN-STEP-Y=0.35 ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 4.58 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category QUASARS & AGN ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category QUASAR ABSORPTION ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CYCLE 3 / 1-2; ONBOARD ACQ FOR 1.1 ONBOARD ACQ FOR 1.2 ONBOARD ACQ FOR 2 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G270H ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC628Q1 ------------------------------------------------------------------------------------------------------------------------------------