! File: 4536C.PROP ! Database: PEPDB ! Date: 22-FEB-1994:16:40:35 coverpage: title_1: THE DISTANCE OF HIGH-VELOCITY CLOUDS title_2: CYC3-HIGH sci_cat: INTERSTELLAR MEDIUM sci_subcat: ABSORPTION LINES proposal_for: GO pi_title: DR. pi_fname: B. pi_mi: P. pi_lname: WAKKER pi_inst: UNIVERSITY OF ILLINOIS pi_country: USA pi_phone: 217-244-4207 hours_pri: 7.00 num_pri: 3 hrs: Y funds_amount: 57353 funds_length: 9 funds_date: OCT-93 pi_position: POSTDOC off_fname: HARVEY off_lname: STAPLETON off_title: SECR. RESEARCH BOARD off_inst: UNIVERSITY OF ILLINOIS off_addr_1: 506 SOUTH WRIGHT STREET off_city: URBANA off_state: IL off_zip: 61801 off_country: USA off_phone: 217-333-0037 ! end of coverpage abstract: line_1: We request time on the HST to obtain high-resolution (20 km/s) spectra line_2: around the 2800A MgII doublet of two stars and one quasar which lie line_3: projected toward the high-velocity HI cloud complex A. The prime purpose line_4: of this project is to determine the distance to complex A. Using these line_5: spectra we will be able to derive for the first time a firm upper or line_6: lower distance limit of 2.5 kpc for a HVC, which allows us to exclude line_7: several of the many proposed explanations. If we find that the object is line_8: beyond 2.5 kpc this will have important implications for the line_9: understanding of the structure of the Galaxy, especially for the energy line_10: balance and dynamics of interstellar matter and the exchange of line_11: material between the halo and the disk. A byproduct of the observations line_12: will be the first measurement of the MgII abundance in a HVC. Metal line_13: abundances are important for the problem of the origin of HVCs. line_14: We discuss the principle and problems of the method used to estimate line_15: distances and describe the current status of knowledge. Ground-based line_16: observations have been limited by sensitivity and ST allows us to reach line_17: stars faint enough so that a clear answer can be found. ! ! end of abstract general_form_proposers: lname: WAKKER fname: B. title: PI mi: P. inst: UNIVERSITY OF ILLINOIS country: USA ! lname: DANLY fname: L. title: CO-I inst: SPACE TELESCOPE SCIENCE INSTITUTE country: USA ! lname: SCHWARZ fname: U. title: CO-I mi: J. inst: KAPTEYN LABORATORIUM, UNIVERSITY OF GRONINGEN country: NETHERLANDS esa: Y ! lname: VAN WOERDEN fname: H. title: CO-I inst: KAPTEYN LABORATORIUM, UNIVERSITY OF GRONINGEN country: NETHERLANDS esa: Y ! ! end of general_form_proposers block general_form_text: question: 3 section: 1 line_1: Below we list the selected objects. For each probe we want to get one line_2: around the 2800 A MgII doublet, a strong resonance transition from a line_3: species with high abundance in the ISM. The current state of the GHRS line_4: makes this the optimal line. line_5: Listed are estimated fluxes at 2800 A, in erg/cm^2/s/A. They were line_6: derived by assuming Teff=25000 K, a typical temperature for the cooler line_7: in the list of Moehler et al. (1990), who derived Teff from a detailed line_8: analysis. We used a Kurucz model with this temperature to find the line_9: ratio of fluxes between B magnitude and 2800 A. We can justify this line_10: method because IUE spectra we obtained earlier for a few other, line_11: brighter, sdB stars from the PG list fit the Kurucz distribution well. line_12: The spectral resolution we need is determined by the width of the line_13: emission at 21 cm. In complex A the widths vary with angular resolution line_14: and can be as narrow as 5 km/s FWHM (Wakker Schwarz 1991). However, line_15: this width is for the cooler gas in this HVC. Most of the emission line_16: comes from gas with widths of about 10-15 km/s. Thus, our instrument of line_17: choice is the medium-resolution spectrograph in the GHRS, combined with line_18: the large aperture, giving a resolution of 20 km/s at 2800 A. ! question: 4 section: 1 line_1: The determination of the distance to high-velocity clouds has been an line_2: unsolved problem for almost 30 years. Recent progress shows that it is line_3: likely that HVCs are a few kpc distant (see Wakker, 1991a). So far, all line_4: attempts to determine distances directly via absorption-line studies line_5: have failed to give conclusive results. Songaila et al. (1988) and line_6: Lilienthal et al. (1990) showed complex A has D>300 pc. Schwarz et al. line_7: (1992) failed to detect absorption in PG0832+676 (B=14.3) at the level line_8: of 24 mA, with 5h integration. The distance is about 1.5 kpc [or 31 kpc line_9: if the analysis by Brown et al. is correct]. line_10: Since no absorptions have been found in nearby stars, it has become line_11: necessary to observe more distant stars. Unfortunately, only a few line_12: stellar types are usable as probes, and so we have to observe faint line_13: stars. Assuming a Ca^+ abundance of 3E-8 for HVCs, integration times line_14: for 5 sigma detections on 4-m class telescopes turn out to be about 100 line_15: hours. With HST we have the following advantanges: 1) the probes have line_16: larger fluxes in the UV than in the blue, 2) we can use the more line_17: sensitive lines of MgII, 3) HST is more sensitive in the UV than ground line_18: based telescopes in the violet, 4) no light is lost due to seeing. line_19: Our project would produce spectra of three probe stars at distances line_20: larger than 1 kpc with 20 km/s velocity resolution and S/N of 15 or line_21: better. If we find a detection, an upper limit to the distance to the line_22: HVC complex A will be known. If we do not find a detection in a stellar line_23: probe the spectrum of the quasar MK 106 will give us the Mg/H ratio. ! question: 4 section: 2 line_1: The HI column densities toward our targets are in the range E19-E20. line_2: For solar abundances (Spitzer 1978), this implies an Mg^+ column line_3: density of 3E14 /cm^2 (Mg^+ is the dominant ionization stage for Mg in line_4: neutral gas). Observations of IVCs indicate that most of the line_5: refractory elements are in the gas phase. However, even if the gas is line_6: depleted as heavily as is found in dense interstellar clouds, the line_7: predicted Mg^+ column density is still 1E13 /cm^2. line_8: Exposure times were calculated to achieve a S/N of 15 in the line_9: continuum at 2800 A. This permits a 5 sigma detection of a 35 mA line, line_10: corresponding to a MgII column density of 7E11 /cm^2, much lower than line_11: the expected column density. Only if the abundances are significantly line_12: less than in dense interstellar clouds (i.e. by at least a factor of line_13: 10), may the detection of HVCs at MgII become difficult. The proposed line_14: S/N ratio is therefore more than sufficient to detect Mg^+ absorption line_15: associated with the HVC, if the probe stars are more distant. line_16: Given the required S/N ratio, we calculated the exposure time using line_17: the fluxes found in Sect. 4a and the updated sensitivity curves for the line_18: G270M grating listed in "Updated Technical Information", 23 May, 1991. line_19: The value of counts/sec/diode was compared to the instrumental line_20: background (0.012 cnts/sec/diode for the red detector) to ensure that line_21: the resultant spectrum would not be dominated by system noise. ! question: 5 section: 1 line_1: Wave calibrations are requested for all spectra. ! question: 6 section: 1 line_1: Wave calibrations are required for all spectra. This was not included line_2: in the Phase I proposal, but is now recognized as essential. Absolute line_3: velocity calibration to about 2-3 km/s is required. Each wave line_4: calibration must be performed with no gap immediately preceeding each line_5: spectral exposure. ! question: 7 section: 1 line_1: The reduction of the HST data will consist of two stages. First Danly line_2: will identify features and measure velocities and equivalent widths, line_3: using STScI software. Further analysis will proceed with Danly's line_4: profile fitting software. The interpretation will be done during visits line_5: of Wakker to ST and of Danly to Illinois. This analysis will use the line_6: accompanying HI maps and the stellar spectroscopic data that were line_7: obtained to determine good distances. It consists of deriving HI column line_8: densities and Mg^+/H ratios or upper limits for the different probes. line_9: Comparison of these values will yield the distance of HVC complex A. ! question: 8 section: 1 line_1: Time has already been allocated at Westerbork to map the several line_2: probe fields in the 21 cm line. line_3: The probes will also be included in the ongoing program of line_4: spectroscopic distance determinations on which our collaborators in line_5: Germany (K.S. de Boer and others) are working, using a number of line_6: telescopes including those at Calar Alto in Spain and at La Silla in line_7: Chile. ! question: 9 section: 1 line_1: unrelated: 2644 - The environment of starburst galaxies: absorption line_2: line studies of galactic outflows; PI C.Norman, Co-Is C.Blades, line_3: L.Danly, T. Heckman line_4: 3606 - The nature of gaseous loops in the Milky Way halo; PI L. Danly, line_5: Co-Is R. Benjamin, K. Kuntz, C.E. Albert, P. Shapiro ! question: 10 section: 1 line_1: We expect that most of the HSR datareduction will be done at STScI, line_2: by Danly in collaboration with Wakker. For the reduction of the radio line_3: and further analysis a workstation for Wakker is requested. ! !end of general form text general_form_address: lname: WAKKER fname: B. mi: P. title: DR. category: PI inst: UNIVERSITY OF ILLINOIS addr_1: ASTRONOMY DEPARTMENT addr_2: 1002 W. GREEN ST. city: URBANA state: IL zip: 61801 country: USA phone: 217-244-4207 telex: NA, FAX 217-244-7638 from_date: 28-JAN-90 ! ! end of general_form_address records fixed_targets: targnum: 1 name_1: MK106 descr_1: E,313,G,509 pos_1: RA = 9H 19M 55.236S +/- 0.5S, pos_2: DEC= +55D 21' 36.66" +/- 0.5", equinox: 2000 comment_1: FLUXNUM: 1=V; 2=BPG; 3=B-V; 4=U-B comment_2: 5=CONT; 6=F-LINE; 7-W-LINE comment_3: DETECTION LIMIT FOR LINE FROM comment_4: F-LINE=F-CONT*0.25; W-LINE=0.14 fluxnum_1: 1 fluxval_1: V = 16.15 fluxnum_2: 3 fluxval_2: B-V = 0.39 fluxnum_3: 4 fluxval_3: U-B = -0.94 fluxnum_4: 5 fluxval_4: F-CONT(2800) = 4.4 E-14 fluxnum_5: 6 fluxval_5: F-LINE(2795) = 4.4 E-14 fluxnum_6: 7 fluxval_6: W-LINE(2795) = 0.14 ! targnum: 2 name_1: PG0859+593 descr_1: A,130,G,509 pos_1: RA = 9H 03M 03.161S +/- 0.5S, pos_2: DEC = +59D 11' 17.86" +/- 0.5", equinox: 2000 comment_1: FLUXNUM: 1=V; 2=BPG; 3=B-V; 4=U-B comment_2: 5=CONT; 6=F-LINE; 7-W-LINE comment_3: DETECTION LIMIT FOR LINE FROM comment_4: F-LINE=F-CONT*0.25; W-LINE=0.14 fluxnum_1: 2 fluxval_1: B = 15.87 fluxnum_2: 5 fluxval_2: F-CONT(2800) = 1.9 E-14 fluxnum_3: 6 fluxval_3: F-LINE(2795) = 1.9 E-14 fluxnum_4: 7 fluxval_4: W-LINE(2795) = 0.14 ! targnum: 3 name_1: PG0906+597 descr_1: A,118,G,509 pos_1: RA = 9H 10M 21.410S +/- 0.5S, pos_2: DEC = +59D 30' 33.85" +/- 0.5", equinox: 2000 comment_1: FLUXNUM: 1=V; 2=BPG; 3=B-V; 4=U-B comment_2: 5=CONT; 6=F-LINE; 7-W-LINE comment_3: DETECTION LIMIT FOR LINE FROM comment_4: F-LINE=F-CONT*0.25; W-LINE=0.14 fluxnum_1: 2 fluxval_1: B = 15.17 fluxnum_2: 5 fluxval_2: F-CONT(2800) = 1.0 E-14 fluxnum_3: 6 fluxval_3: F-LINE(2795) = 1.0 E-14 fluxnum_4: 7 fluxval_4: W-LINE(2795) = 0.14 ! ! end of fixed targets ! No solar system records found ! No generic target records found exposure_logsheet: linenum: 1.100 targname: MK106 config: HRS opmode: ACQ aperture: 2.0 sp_element: MIRROR-N2 wavelength: 2800 num_exp: 1 time_per_exp: 240S priority: 1 req_1: CYCLE 3; req_2: ONBOARD ACQ FOR 1.2,1.3; req_3: SEQ 1.1-1.2 NO GAP ! linenum: 1.200 targname: WAVE config: HRS opmode: ACCUM aperture: SC2 sp_element: G270M wavelength: 2800 num_exp: 1 time_per_exp: DEF priority: 1 param_1: STEP-PATT=5 req_1: CYCLE 3; req_2: CALIB FOR 1.3; req_3: SEQ 1.2-1.3 NO GAP ! linenum: 1.300 targname: MK106 config: HRS opmode: ACCUM aperture: 2.0 sp_element: G270M wavelength: 2800 num_exp: 17 time_per_exp: 500S s_to_n: 20 fluxnum_1: 5 fluxnum_2: 6 fluxnum_3: 7 priority: 10 param_1: FP-SPLIT=STD param_2: STEP-PATT=5 param_3: CENSOR=YES param_4: DOPPLER=ON req_1: CYCLE 3; ! linenum: 2.100 targname: PG0859+593 config: HRS opmode: ACQ aperture: 2.0 sp_element: MIRROR-N2 wavelength: 2800 num_exp: 1 time_per_exp: 240S priority: 1 req_1: CYCLE 3; req_2: ONBOARD ACQ FOR 2.2,2.3; req_3: SEQ 2.1-2.2 NO GAP ! linenum: 2.200 targname: WAVE config: HRS opmode: ACCUM aperture: SC2 sp_element: G270M wavelength: 2800 num_exp: 1 time_per_exp: DEF priority: 1 param_1: STEP-PATT=5 req_1: CYCLE 3; req_2: CALIB FOR 2.3; req_3: SEQ 2.2-2.3 NO GAP ! linenum: 2.300 targname: PG0859+593 config: HRS opmode: ACCUM aperture: 2.0 sp_element: G270M wavelength: 2800 num_exp: 8 time_per_exp: 500S s_to_n: 20 fluxnum_1: 5 fluxnum_2: 6 fluxnum_3: 7 priority: 1 param_1: FP-SPLIT=STD param_2: STEP-PATT=5 param_3: CENSOR=YES param_4: DOPPLER=ON req_1: CYCLE 3; ! linenum: 3.100 targname: PG0906+597 config: HRS opmode: ACQ aperture: 2.0 sp_element: MIRROR-N2 wavelength: 2800 num_exp: 1 time_per_exp: 240S priority: 1 req_1: CYCLE 3; req_2: ONBOARD ACQ FOR 3.2,3.3; req_3: SEQ 3.1-3.2 NO GAP ! linenum: 3.200 targname: WAVE config: HRS opmode: ACCUM aperture: SC2 sp_element: G270M wavelength: 2800 num_exp: 1 time_per_exp: DEF priority: 1 param_1: STEP-PATT=5 req_1: CYCLE 3; req_2: CALIB FOR 3.3; req_3: SEQ 3.2-3.3 NO GAP ! linenum: 3.300 targname: PG0906+597 config: HRS opmode: ACCUM aperture: 2.0 sp_element: G270M wavelength: 2800 num_exp: 7 time_per_exp: 500S s_to_n: 20 fluxnum_1: 5 fluxnum_2: 6 fluxnum_3: 7 priority: 50 param_1: FP-SPLIT=STD param_2: STEP-PATT=5 param_3: CENSOR=YES param_4: DOPPLER=ON req_1: CYCLE 3; ! ! end of exposure logsheet ! No scan data records found