8297( 4) - 03/27/00 10:51 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8297 Version: 4 Check-in Date: 27-Mar-2000 10:50:20 1.Proposal Title: The Physical State of the Starburst Outflow in NGC1705 ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 8 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Claus Leitherer Space Telescope Science Institute CoI: Dr. Du'\i lia de Mello Space Telescope Science Institute N CoI: Prof. Tim Heckman The Johns Hopkins University N CoI: Dr. Crystal Martin Space Telescope Science Institute N CoI: Dr. Gerhardt Meurer The Johns Hopkins University N CoI: Dr. Ken Sembach The Johns Hopkins University N ------------------------------------------------------------------------------------ 5. Abstract We propose STIS echelle M mode spectroscopy from 1200 Angstrom\ to 3000 Angstrom\ of the nearby starburst galaxy NGC1705. Our selected sightline towards the super star cluster NGC1705-1 probes the physical conditions in the starburst- driven galactic superwind. The resolution of ~10 kms\ is a factor-of-30 improvement over existing HST data and allows a study of the complex outflow kinematics. Multiple supershells are expected to be resolved. Together with FUSE data, the proposed observations will constrain the energetics of the cold and hot gas and help determine if the outflow material can escape from the galaxy. Several weak lines will be measured at sufficiently high S/N to derive column densities and abundances. Previous suggestions of an Alpha-element/Fe enhancement will be verified or rejected using weak Si II, S II, Cr II and Zn II lines. Dust depletion in the outflow will be studied with Fe II lines. No other starburst-driven outflow can be observed with STIS at even remotely similar resolution and S /N. The chosen sightline will allow us to generalize our results to the overall properties of the galaxy outflow, to search for implications for similar galaxies at cosmological distances, and to add to our understanding of QSO absorption lines. We will reduce the proprietary period to six months to allow the community rapid access to these template spectra. ------------------------------------------------------------------------------------ 8297( 4) - 03/27/00 10:51 - [ 2] Observations Description ------------------------ We will observe NGC1705-1 with the echelle gratings E140M and E230M and the 0.2x0.2 aperture. This will allow us to study the gas kinematics at about 7 kms\ resolution. Since the existing GHRS G140L data were taken with the SSA, which has almost exactly the same size as the 0.2x0.2 aperture, a precise S/N estimate can be made. We used the GHRS spectrum to estimate the exposure time for the E140M observations. For E230M we extrapolated the GHRS flux to longer wavelengths using the spectral shape information from an existing IUE spectrum. HST UV spectra of starbursts have been obtained and analyzed by us repeatedly (e.g., Leitherer et al. 1996; Conti et al. 1996; Heckman & Leitherer 1997). Past experience suggests an optimum S/N in the range 10 to 20. Lower S/N makes it difficult to define the continuum level in regions with heavy line- blanketing. Even higher values are of course desirable but the additional information gain would not justify the observational cost. Our strate gy for the proposed observations i s to aim for S/N = 15. We used the observed G140L spectrum of NGC1705-1 to compute the required exposure time with the STIS exposure time calculator. An exposure time of 15, 000 s will give S/N = 15 per resolution element in dispersion direction at 1400 Angstrom. Peak counts are around 1300 Angstrom, where S/N = 18 is reached. At 1200 and 1600 Angstrom, towards the extremes of the free wavelength range, the S/N drops to about 10. The same E230M observations for the same S/N are shorter, despite the lower flux of NGC1705-1 at longer wavelengths. 6000 s and 3600 s are required for S/N = 15 at a central wavelength of 1978 Angstrom\ and 2707 Angstrom, respectively. Six orbits are required for a total integration time of 15, 000 s with E140M. We would prefer to complete the full E140M exposure during one visit. Should SAA impact make it difficult to obtain six contiguous orbits, we will split the E140M observations in two visits, the first with five orbits and the second with one . The one orbit visit will be comb i ned with the four orbits of the E230M visit (see below), with no additional overhead. NGC1705-1 is visible during 3400 s of each orbit so that 6 orbits have a total of 20, 400 s. We will perform a standard target acquisition. No peak-up is required. The total overhead in the first orbit is about 20 minutes. This includes the guide-star and target acquisition and the initial MAMA overhead. Subsequent orbits have each about 10 minutes of overhead, depending on how efficiently we can hide the autowavecals and the STIS buffer dump in occulted time. Therefore the total overhead in all six orbits is 4200 s, leaving 16, 200 s for actual photon collection with E140M. The E230M observations can all be done in one visit. The science exposures for both grating settings last for a total of 9600 s. Allowing for overhead, we find that four orbits are required for E230M. Therefore we request a total of ten orbits, six for E140M and four for E230M. Real Time Justification ----------------------- We have no special requirements. No supporting/coordinated observations are planned. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 8297( 4) - 03/27/00 10:51 - [ 3] Data Distribution Paper Products: Media: ELECTRONIC Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 8297( 4) - 03/27/00 10:51 - [ 4] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC1705-1 EXT-CLUSTER, GLOBULAR RA=04H 54M 13.4S +/- 0.1S, DEC=- J2000 F(1500)=1.0e-13 CLUSTER 53D 21' 38.9" +/- 1.0" F(2300)=3.0e-14 V = 14.9 Comments: Flux from existing GHRS spectrum 8297( 4) - 03/27/00 10:51 - [ 5] 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 NGC1705-1 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 2 S CD P ------------------------------------------------------------------------------------------------------------------------------------ 20 NGC1705-1 STIS/F ACCUM 0.2X0.2 E140M 1425 1 42 M UV-MAM A Comments: Orbit 1 ------------------------------------------------------------------------------------------------------------------------------------ 30 NGC1705-1 STIS/F ACCUM 0.2X0.2 E140M 1425 1 45 M UV-MAM A Comments: Orbit 2 ------------------------------------------------------------------------------------------------------------------------------------ 40 NGC1705-1 STIS/F ACCUM 0.2X0.2 E140M 1425 1 45 M UV-MAM A Comments: Orbit 3 ------------------------------------------------------------------------------------------------------------------------------------ 45 NGC1705-1 STIS/C ACQ/PEA 0.2X0.2 MIRROR 1 10 S CD K Comments: Peak-up to recenter after 3 orbits ------------------------------------------------------------------------------------------------------------------------------------ 50 NGC1705-1 STIS/F ACCUM 0.2X0.2 E140M 1425 1 50 M UV-MAM A Comments: Orbit 4 ------------------------------------------------------------------------------------------------------------------------------------ 60 NGC1705-1 STIS/F ACCUM 0.2X0.2 E140M 1425 1 50 M UV-MAM A Comments: Orbit 5 ------------------------------------------------------------------------------------------------------------------------------------ 8297( 4) - 03/27/00 10:51 - [ 6] Visit: 02 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 NGC1705-1 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 2 S CD P ------------------------------------------------------------------------------------------------------------------------------------ 20 NGC1705-1 STIS/F ACCUM 0.2X0.2 E140M 1425 1 42 M UV-MAM A Comments: Orbit 6 of E140M ------------------------------------------------------------------------------------------------------------------------------------ 30 NGC1705-1 STIS/N ACCUM 0.2X0.2 E230M 1978 1 50 M UV-MAM A Comments: Orbit 2 ------------------------------------------------------------------------------------------------------------------------------------ 40 NGC1705-1 STIS/N ACCUM 0.2X0.2 E230M 1978 1 43 M UV-MAM A Comments: Orbit 3 ------------------------------------------------------------------------------------------------------------------------------------ 45 NGC1705-1 STIS/C ACQ/PEA 0.2X0.2 MIRROR 1 10 S CD K Comments: Peak-up to recenter after 3 orbits ------------------------------------------------------------------------------------------------------------------------------------ 47 NGC1705-1 STIS/N ACCUM 0.2X0.2 E230M 1978 1 33 M UV-MAM A Comments: Orbit 3 ------------------------------------------------------------------------------------------------------------------------------------ 50 NGC1705-1 STIS/N ACCUM 0.2X0.2 E230M 2707 1 15 M UV-MAM A Comments: Orbit 4 ------------------------------------------------------------------------------------------------------------------------------------ 60 NGC1705-1 STIS/N ACCUM 0.2X0.2 E230M 2707 1 48 M UV-MAM A Comments: Orbit 5 ------------------------------------------------------------------------------------------------------------------------------------ 8297( 4) - 03/27/00 10:51 - [ 7] Summary Form for Proposal 8297 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 0.2X0.2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/FUV-MAMA STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ACQ/PEAK ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR E140M E230M ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC1705-1 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 1425 1978 2707 ------------------------------------------------------------------------------------------------------------------------------------