Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 4525c Report Date: 09-May-96:19:41 Version: ********** Check-in Date: ********** 1.Proposal Title: THE ABSORPTION CROSS-SECTIONS OF NEARBY GALAXIES -CYC3 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 Chris Blades STSCI USA ------------------------------------------------------------------------------------ 7. Abstract We wish to examine the hypothesis that low-redshift galaxies are surrounded by extended gaseous haloes and disks. Specifically, we propose using the GHRS to search for Mg II or C IV absorption lines in the haloes of four low-redshift galaxies lying fortuitously in front of background quasars. We aim to reach sensitive equivalent widths limits of 60 mA and 40 mA (2 sigma) for each of the ions, and hence to infer the chemical, ionization and kinematic conditions within the absorbing gas by accurately measuring column densities, doppler parameters, and the large-scale multicomponent structure of the lines. Comparisons of the absorption in nearby galaxies with the lines seen at higher redshifts in QSO spectra should help settle the issue of how the metal-line systems originate. Our recent Cycle 1 discovery of MgII and C~IV absorption in the spectrum of Mrk~205 from the intervening galaxy NGC~4319 demonstrates that the technique is a powerful tool for investigating the interstellar medium of intervening galaxies and provides a stimulating comparision to the systems seen at higher redshifts. We were allocated 20 hours in Cycle 1, and 15 hours in Cycle 2. We now wish to conclude our GHRS survey in cycle 3. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 13.95 par: 0 10. Num targs pri: 4 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: HRS ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 4525c PI: Chris Blades Proposal Title: THE ABSORPTION CROSS-SECTIONS OF NEARBY GALAXIES -CYC3 SUPPLEMENTAL ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Pi Chris Blades STSCI USA X David V. Bowen STSCI USA X ------------------------------------------------------------------------------------ 2. Scientific Justification. Page 3 ------------------------------------------------------------------------------------ 3. Description of proposed observations. We have selected 4 quasars based on their small separations from foreground galaxies, and on their brightness. QSOs with known UV fluxes are selected preferentially. Pairs in which the absorption line would be blended with local Galactic lines were excluded. An exhaustive search of the literature and examination of fields around QSOs with known UV flux shows that these are the brightest QSOs available with the smallest separations from galaxies. Details of the QSO-galaxy pairs selected are given below, except for 0026+129, whose observation is designed to complement a search for Mg~II in Cycle 2. We would use the G160M grating to observe C~IV and the G270M grating to search for Mg~II at the redshift of the galaxies listed below. The exception is 1116+215, whose flux is strong enough to permit observations with ECH-B. {\bf 0318$-$196 and NGC~1300:} Though the separation between the quasar and this nearby face-on galaxy is 44~kpc, the line-of-sight passes the disk within approximately three times the galaxy's optical radius, and within only twice the limit of the H~I distribution at a level of $5\times10^{19}$~cm$^{-2}$. Though the non-detection of Ca~II (Bowen~\etal\ 1991, Bothun, Margon \& Balick 1984) might be expected from a gas with an H~I column density less than this, we would expect Mg~II absorption from the disk and/or halo if there is no sharp cutoff in the H~I distribution. This pair was included in our successful Cycle 2 proposal, but uncertainty in the UV flux of the QSO forced us to omit the observation in Phase 2, despite the pairs obvious importance and suitability for this project. Since then, however, optim extraction and co-addition of spectra from the {\it IUE} archive by Lanzetta, Turnshek \& Sandoval (1992) demonstrates that the flux at 2800~\AA\ is quite sufficient to permit us to obtain high quality data, and we now consider this pair to be of highest priority. {\bf 3C232 and NGC 3067:} The spectrum of this famous QSO-galaxy pair was first shown to exhibit Ca~II absorption from the intervening galaxy by Boksenberg \& Sargent (1978). Recently, Carilli, van Gorkom \& Stocke (1989) showed that the absorption arose in gas distributed as a long tail extending from the center of the galaxy, across the QSO sightline. Extraction of IUE archive data by Kinney~\etal\ (1990) also showed Mg~II absorption (Bowen~\etal\ 1991a). Examination of the HST archive, and the planned Cycle 2 observations, reveals that no data were taken of this QSO in Cycle 1 and that only one group (Bachall \& Ratnatunga) will observe the sightline in Cycle 2 (augmentation), using the lower resolution of the {\it FOS}. As explained previously, data obtained with the {\it GHRS} will not only allow a more accurate determination of the physical conditions within the gas, but will also provide important information on its kinematics. We can then compare the velocity structure with that seen in similar resolution observations of Mg~II absorption at higher redshifts, and thereby ascertain whether similar galactic structures could be responsible for QSO absorption lines at earlier epochs. {\bf 1116+215 and Leo II:} The local dwarf galaxy Leo II lies 1.56 degrees from 1116+215. Despite the large angular separation, if the distance to Leo II is 230 kpc, then the sightline to the quasar intercepts the galaxy at only 6.2 kpc Zaritsky~\etal\ (1989) who found \vh$\:=\:70\pm4$~km/s , agreeing well with previous determinations (e.g. Olszewski, Peterson \& Aaronson 1986 and refs. therein) of $\simeq\:95\pm25$~km/s . The precision with which this number is known is important because the expected absorption from Leo II must not fall in the strong local Mg~II lines. This should not be a problem for two reasons: {\it a)} calculation of the absorption from gas corotating with the Galaxy shows that for an infinitely sized halo, the maximum corotation velocity is 60~km/s . For more reasonable scale heights ($\simeq\:2$~kpc) the maximum velocity is $<\:40$~km/s . Our three Cycle 1 observations show that the distribution of Mg~II components follows Galactic corotation closely. {\it b)} The QSO is bright enough to use ECH-B for the Mg~II absorption. This will not only give us sufficient resolution to resolve any absorption from Leo~II but will permit one of the first observations of absorption from the Milky Way towards an {\it extragalactic} sightline (that is, through the entire length of the halo) using ECH-B. Page 4 ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. The study of absorption by low-redshift galactic haloes in the {\it same} ions observed at higher redshifts is arguably the most important step in understanding the nature of the absorbing galaxies in the early universe. Mg~II lines can only be observed for $z\:\apg\:0.2$ and C~IV above $z\:\apg\: 1.2$ in the optical. These are therefore only accessible at lower redshifts with the {\it International Ultraviolet Explorer (IUE)}. {\it IUE} has a small aperture which permits detection of only strong ($1-2$~\AA ) lines in the brightest quasar spectra and is unsuitable for detecting lines at the equivalent width limits (0.25~\AA ) of the higher redshift absorption line surveys. The {\it GHRS} plus {\it HST} is ideal for this study. The instrument is sensitive enough to detect weak Mg~II and C~IV lines in bright quasars, and, with the intermediate- dispersion gratings, data can be obtained with a resolution which discerns the large-scale velocity structure of the absorption-line profiles. This in turn permits a more accurate determination of column densities and doppler parameters, and leads to a more detailed analysis of the chemical, ionization and kinematics of the absorbing gas. For these two reasons, the {\it GHRS} is more suitable for studying the physics of galactic haloes than the {\it FOS}. All our exposure times are aimed at obtaining a uniform signal-to-noise ratio---and hence equivalent width limit---for all the spectra. We have adopted a background count of 0.012~\cds\ for Detector 2 and set all the exposure times to reach a signal- to-noise---for half-stepped data---of 7 per pixel for Mg~II lines and 5 per pixel for C~IV. The one exception is 1116+215, whose flux is high enough for us to reach a S/N of 9 with ECH-B in 1.6 hours. From our experience with Cycle 1 and 2 {\it GHRS} data, we have found these values to be sufficient to allow fitting of theoretical absorption line profiles. If the resolution of the spectrograph can be characterised by the FWHM of the PSF given by Duncan (1992), about 2.3 pixels for half-stepped data, then we achieve resolutions of $\simeq\:15$~km/s with the 270M and 20~km/s with the 160M grating. We then reach equivalent width limits of $\simeq\:30$~m\AA\ at Mg~II and at C~IV ($2\sigma$), and will be able to resolve components within the absorption line. Where the line is weak or undetected, rebinning the spectra from the G270M grating would improve the equivalent width limit by $\approx\:15$\%. We base our exposure times on the sensitivity curves in v3.0 of the ``{\it GHRS} Instrument Handbook''. The flux is known for all of our objects from {\it IUE} archive data compiled by Kinney~\etal\ (1991) or by Lanzetta, Turnshek \& Sandoval (1992). The accuracy of the anticipated count rates also depends on the variability of the quasar, but we expect variations of $< \pm 2$ based on the the values found by Kinney~\etal . ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. We expect any MgII absorption from LeoII toward 1116+215 to be just resolved from the local MgII absorption. Current estimates of the velocities of stars within the dwarf are very precise, of order of a few km/s, and we would wish to match any absorption features seen with these velocities. We therefore require a wavelength accuracy better than the $\pm1$ diode (half a resolution element) normally available, and will need spectral calibration lamps taken after the exposure, as suggested in the {\it GHRS} manual. ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. None ------------------------------------------------------------------------------------ 7. Data reduction and analysis plans. All the data should be reducible using standard IRAF and STSDAS reduction packages. For absorption lines in which we resolve components, we have profile fitting routines available for subjective fits to the data, plus automatic routines which produce a best fit based on minimizing chi-squared. One of us (DVB) will work full time on the data reduction and analysis. Page 5 ------------------------------------------------------------------------------------ 8. Additional comments or special requests. ------------------------------------------------------------------------------------ 9. Description of previous HST work. ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). ------------------------------------------------------------------------------------ 11. Address Information Name: CHRIS BLADES Category: PI Institution: STScI Address: 3700 SAN MARTIN DRIVE City: BALTIMORE State: MD Zip Code: 21218 Country: USA Telephone: 410-338-4805 Telex (or e-mail): blades@stsci.edu ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 4525c [ 6] ------------------------------------------------------------------------------------------------------------------------------------ 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 0318-196 E,313,314 RA= 3H 20M 21.15S +/- 0.3", 2000 Z=0.104 1 V=14.9 DEC= -19D 26' 32" +/- 0.3", 2 F-CONT(2800)=4E-15 PLATE-ID=014E ------------------------------------------------------------------------------------------------------------------------------------ 2 0955+326 E,313,314 RA= 9H 58M 21.03S +/- 0.3", 2000 Z=0.533 1 V=15.8 DEC= 32D 24' 1.5" +/- 0.3", 2 F-CONT(2800)=5E-15 PLATE-ID=01RS ------------------------------------------------------------------------------------------------------------------------------------ 3 0026+129 E,313,314 RA= 0H29M13.75S +/- 0.3", 2000 Z=0.142 1 V=15.4 DEC= 13D16'3.7" +/- 0.3", 2 F-CONT(1500)=1.8E-14 PLATE-ID=028X ------------------------------------------------------------------------------------------------------------------------------------ 4 1116+215 E,313,314 RA= 11H 19M 8.72S +/- 0.3", 2000 Z=0.177 1 V=15.0 DEC= 21D 19' 18.1" +/- 0.3", 2 F-CONT(2800)=3.0E-14 PLATE-ID=01TL ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 4525c [ 7] ------------------------------------------------------------------------------------------------------------------------------------ 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 0318-196 HRS ACQ 2.0 MIRROR-N2 SEARCH-SIZE=3 1 9S 1 1 CYCLE 3 BRIGHT=RETURN ONBOARD ACQ FOR 2 DARK TIME ------------------------------------------------------------------------------------------------------------------------------------ 2 0318-196 HRS ACCUM 2.0 G270M 2807.3 COMB=FOUR 9 1080S 7 2 1 CYCLE 3 FP-SPLIT=FOUR 9720S STEP-PATT=4 ------------------------------------------------------------------------------------------------------------------------------------ 3 0955+326 HRS ACQ 2.0 MIRROR-N2 SEARCH-SIZE=3 1 9S 1 1 CYCLE 3 BRIGHT=RETURN ONBOARD ACQ FOR 4 DARK TIME ------------------------------------------------------------------------------------------------------------------------------------ 4 0955+326 HRS ACCUM 2.0 G270M 2807.1 COMB=FOUR 6 1080S 7 2 1 CYCLE 3 FP-SPLIT=FOUR 6480S STEP-PATT=DEF ------------------------------------------------------------------------------------------------------------------------------------ 5 0026+129 HRS ACQ 2.0 MIRROR-N2 SEARCH-SIZE=3 1 9S 1 1 CYCLE 3 BRIGHT=RETURN ONBOARD ACQ FOR 6 DARK TIME ------------------------------------------------------------------------------------------------------------------------------------ 6 0026+129 HRS ACCUM 2.0 G160M 1557.0 COMB=FOUR 12 1170S 5 2 1 CYCLE 3 FP-SPLIT=FOUR 3.9H STEP-PATT=4 ------------------------------------------------------------------------------------------------------------------------------------ 7 1116+215 HRS ACQ 2.0 MIRROR-N2 SEARCH-SIZE=3 1 9S 1 1 CYCLE 3 BRIGHT=RETURN ONBOARD ACQ FOR 6 DARK TIME ------------------------------------------------------------------------------------------------------------------------------------ 8 1116+215 HRS ACCUM 2.0 ECH-B 2799.6 COMB=FOUR 5 1166S 9.1 2 2 CYCLE 3 FP-SPLIT=FOUR 5832S STEP-PATT=6 ------------------------------------------------------------------------------------------------------------------------------------ 9 WAVE HRS ACCUM SC2 ECH-B 2799.6 COMB=FOUR 1 60S 2 CALIB FOR 8.0 FP-SPLIT=FOUR SEQ 8.0-9.0 NO GAP STEP-PATT=6 CYCLE 3 ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 4525c [ 8] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SEARCH-SIZE=3 BRIGHT=RETURN COMB=FOUR FP-SPLIT=FOUR STEP-PATT=4 STEP-PATT=DEF STEP-PATT=6 ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 13.95 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category QUASARS & AGN ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category QUASAR ABSORPTION ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CYCLE 3; ONBOARD ACQ FOR 2; DARK TIME CYCLE 3 ONBOARD ACQ FOR 4; ONBOARD ACQ FOR 6; CALIB FOR 8.0; SEQ 8.0-9.0 NO GAP; ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR-N2 G270M G160M ECH-B ------------------------------------------------------------------------------------------------------------------------------------ Target Names 0318-196 0955+326 0026+129 1116+215 ------------------------------------------------------------------------------------------------------------------------------------