8621( 2) - 03/02/00 08:22 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8621 Version: 2 Check-in Date: 02-Mar-2000 08:20:58 1.Proposal Title: The Galactic Abundance Gradients of Boron and Iron ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 9 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: David Lambert University of Texas at Austin CoI: Dr. Robert Rolleston The Queen's University of Belfast Y CoI: Dr. Stephen Smartt Institute of Astronomy, Cambridge N CoI: Dr. Kim Venn Macalester College N CoI: Prof. Philip L. Dufton The Queen's University of Belfast N CoI: Dr. Francesca Matteucci University of Trieste N ------------------------------------------------------------------------------------ 5. Abstract This proposal aims to provide the first measurement of the Galactic abundance gradients for Boron and Iron. Boron abundances will be obtained for 5 B-type stars (with Galactocentric distances between 4-15 kpc) from the BIII 2066 Angstrom line. Optical spectroscopy of these (and other B-type) stars has yielded abundance gradients of -0.07 dex/kpc for N & the Alpha-elements (O, Mg, Si). Determination of Boron abundances require UV spectra and HST/STIS. It is significant that stellar nucleosynthesis which is the leading source of oxygen (via Type II SN) is unlikely to be a major contributor to B synthesis (spallation being the leading candidate). Hence, a measurement of the B abundance gradient provides novel information on the gradient of cosmic ray flux in the Galaxy. The same STIS spectra will also provide FeIII lines that will be used to obtain the first estimate of the present abundance gradient for iron (thought to originate predominantly in Type I SN). Recent advances in modelling the chemical evolution of the Galactic disk have led to definite predictions of the spatial variation of the Alpha/Fe ratio in competing Galaxy formation scenarios, viz. the biased infall and biased outflow models. This study should yield differential Fe abundances accurate to +/-0.1 dex -- which will allow a Alpha/Fe gradient to be compared directly with theory, as a critical test of formation models. ------------------------------------------------------------------------------------ 8621( 2) - 03/02/00 08:22 - [ 2] Observations Description ------------------------ We are requesting observations of the BIII 2066 Angstrom line in 5 young, B- type main-sequence stars over a range of galactocentric distances. These objects have chemical compositions that are representative of their progenitor interstellar material -- and hence, are suitable for tracing the present-day abundance gradients. Furthermore, they possess similar atmospheric parameters which will enable differential abundances to be determined to better than 0.1 dex. We will observe our targets using STIS + G230M grating with the 52x0.1 aperture. The moderate resolution of the G230M grating (~23 km/s) matches the observed projected rotational velocities of the stars (typically ~30 km/s, see Table 1). We have performed tests with synthetic spectra to estimate the S/N ratio that will be required to facilitate the reliable measurement of the BIII line-strengths. In Fig. a), we show our predictions for the outer and inner disk stars. Synthetic spectra have been generated using a model atmosphere with T_eff=25 000 K and log g=4.0 dex, and using metallicities and predicted Boron abundances appropriate for each case. These were convolved with a rotational broadening function of 30 km/s and rebinned to the pixel size obtained with the G230M grating. Our tests show that for a S/N~40, it will be possible to reliably measure the Boron line-strengths in all our targets. Furthermore, this spectral region (2050--2140 Angstroms) contains lines due to iron such as the FeIII multiplets at 2069, 2084, 2093 & 2117 Angstroms. The line-strengths of these features are comparable to (or exceed) that of the boron lines; hence, these observations will simultaneously allow us to determine the iron abundance gradient. The exposure time estimates presented in Table 1 have been obtained using the STIS exposure time calculator on the WWW. These have been calculated so as to provide a S/N~40 at 2065 Angstroms, assuming Kurucz model atmospheres with appropriate effective temperatures and surface gravities for the individual stars. Reddenings along the individual sight-lines have been taken from the literature and are also given in Table 1. Table 1: Target stars Object V E(B-V) SpT T_eff log g vsin i R_g t_EXP (K) (dex) (km/s) (kpc) (min) LS 5130 12.09 0.44 B1.5V 23 000 3.8 35 4.0 128 NGC 6231-295 9.41 0.44 B0.5V 27 500 4.1 30 6.9 11 NGC 884-2361 8.75 0.60 B1V 25 000 3.8 25 9.9 15 S285-6 12.05 0.56 B0.5V 27 500 4.0 20 12.3 252 S289-2 12.66 0.53 B0.5V 28 500 4.0 40 15.4 384 Orbit estimates have been determined from the exposure time estimates above, using the procedures outlined in the STIS manual, and including the relevant overhead requirements. Real Time Justification ----------------------- No special requirements for this proposal. Calibration Justification ------------------------- No special requirements for this proposal. Additional Comments ------------------- We already have extensive ground-based optical spectroscopy for the targets requested here, which have provided accurate stellar atmospheric parameters and reliable element abundances for C, N, O, Mg & Si. Furthermore, we have found that these stars are representative of the ISM at these Galactocentric distances. ------------------------------------------------------------------------------------ 8621( 2) - 03/02/00 08:22 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 LS5130 STAR, B0-B2 V-IV RA=18H 50M 7.07S +/- 0.02S, DEC= J2000 V = +111 V = 12.09+/-0.02 -13D 3' 29.6" +/- 0.3", PLATE- B-V = +0.24+/-0.05 ID=064C E(B-V) = 0.44+/-0.05 TYPE=B1.5IV 2 CD-41D11048 STAR, B0-B2 V-IV RA=16H 54M 6.78S +/- 0.02S, DEC= J2000 V = 9.41+/-0.02 -41D 50' 7.2" +/- 0.3", PLATE- B-V = +0.14+/-0.02 ID=06Q2 E(B-V) = 0.44+/-0.05 TYPE=B0.5V 3 HD14476 STAR, B0-B2 V-IV RA=02H 22M 16.96S +/- 0.5", J2000 V = 8.75+/-0.01 DEC=57D 16' 19.0" +/- 0.5" B-V = +0.38+/-0.02 E(B-V) = 0.60+/-0.05 TYPE=B1V 4 S285-6 STAR, B0-B2 V-IV RA=06H 55M 17.17S +/- 0.08S, J2000 V = +39 V = 12.05+/-0.02 DEC=-00D 33' 42.1" +/- 1.2", B-V = +0.26+/-0.04 PLATE-ID=00TW E(B-V) = 0.56+/-0.05 TYPE=B0.5V 5 S289-2 STAR, B0-B2 V-IV RA=06H 45M 45.62S +/- 0.02S, J2000 V = +35 V = 12.66+/-0.02 DEC=-07D 18' 26.2" +/- 0.3", B-V = +0.21+/-0.04 PLATE-ID=00F4 E(B-V) = 0.53+/-0.06 TYPE=B0.5V 8621( 2) - 03/02/00 08:22 - [ 4] 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 LS5130 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 1.0 S CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 LS5130 STIS/C ACQ/PEA 52X0.1 MIRROR 1 1.0 S CD K ------------------------------------------------------------------------------------------------------------------------------------ 3 LS5130 STIS/N ACCUM 52X0.1 G230M 2095 1 2125 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 4 LS5130 STIS/N ACCUM 52X0.1 G230M 2095 1 2880 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 5 LS5130 STIS/N ACCUM 52X0.1 G230M 2095 1 2880 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 6 LS5130 STIS/N ACCUM 52X0.1 G230M 2095 1 2880 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8621( 2) - 03/02/00 08:22 - [ 5] 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 CD-41D11048 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 0.1 S CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 CD-41D11048 STIS/C ACQ/PEA 52X0.1 MIRROR 1 0.1 S CD K ------------------------------------------------------------------------------------------------------------------------------------ 3 CD-41D11048 STIS/N ACCUM 52X0.1 G230M 2095 1 2260 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8621( 2) - 03/02/00 08:22 - [ 6] Visit: 03 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 HD14476 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 0.1 S CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 HD14476 STIS/C ACQ/PEA 52X0.1 MIRROR 1 0.1 S CD K ------------------------------------------------------------------------------------------------------------------------------------ 3 HD14476 STIS/N ACCUM 52X0.1 G230M 2095 1 2375 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8621( 2) - 03/02/00 08:22 - [ 7] Visit: 04 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 S285-6 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 1.0 S CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 S285-6 STIS/C ACQ/PEA 52X0.1 MIRROR 1 1.0 S CD K ------------------------------------------------------------------------------------------------------------------------------------ 3 S285-6 STIS/N ACCUM 52X0.1 G230M 2095 1 2125 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 4 S285-6 STIS/N ACCUM 52X0.1 G230M 2095 1 2895 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 5 S285-6 STIS/N ACCUM 52X0.1 G230M 2095 1 2895 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 6 S285-6 STIS/N ACCUM 52X0.1 G230M 2095 1 2465 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7 S285-6 STIS/C ACQ/PEA 52X0.1 MIRROR 1 1.0 S CD K ------------------------------------------------------------------------------------------------------------------------------------ 8 S285-6 STIS/N ACCUM 52X0.1 G230M 2095 1 2895 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8621( 2) - 03/02/00 08:22 - [ 8] Visit: 05 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 S285-6 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 1.0 S CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 S285-6 STIS/C ACQ/PEA 52X0.1 MIRROR 1 1.0 S CD K ------------------------------------------------------------------------------------------------------------------------------------ 3 S285-6 STIS/N ACCUM 52X0.1 G230M 2095 1 2125 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 4 S285-6 STIS/N ACCUM 52X0.1 G230M 2095 1 2895 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 5 S285-6 STIS/N ACCUM 52X0.1 G230M 2095 1 2895 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8621( 2) - 03/02/00 08:22 - [ 9] Visit: 06 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 S289-2 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 1.0 S CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 S289-2 STIS/C ACQ/PEA 52X0.1 MIRROR 1 2.0 S CD K ------------------------------------------------------------------------------------------------------------------------------------ 3 S289-2 STIS/N ACCUM 52X0.1 G230M 2095 1 2115 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 4 S289-2 STIS/N ACCUM 52X0.1 G230M 2095 1 2895 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 5 S289-2 STIS/N ACCUM 52X0.1 G230M 2095 1 2895 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 6 S289-2 STIS/N ACCUM 52X0.1 G230M 2095 1 2450 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7 S289-2 STIS/C ACQ/PEA 52X0.1 MIRROR 1 2.0 S CD K ------------------------------------------------------------------------------------------------------------------------------------ 8 S289-2 STIS/N ACCUM 52X0.1 G230M 2095 1 2895 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8621( 2) - 03/02/00 08:22 - [ 10] Visit: 07 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 S289-2 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 1.0 S CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 S289-2 STIS/C ACQ/PEA 52X0.1 MIRROR 1 2.0 S CD K ------------------------------------------------------------------------------------------------------------------------------------ 3 S289-2 STIS/N ACCUM 52X0.1 G230M 2095 1 2115 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 4 S289-2 STIS/N ACCUM 52X0.1 G230M 2095 1 2895 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 5 S289-2 STIS/N ACCUM 52X0.1 G230M 2095 1 2895 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8621( 2) - 03/02/00 08:22 - [ 11] Visit: 08 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 S289-2 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 1.0 S CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 S289-2 STIS/C ACQ/PEA 52X0.1 MIRROR 1 2.0 S CD K ------------------------------------------------------------------------------------------------------------------------------------ 3 S289-2 STIS/N ACCUM 52X0.1 G230M 2095 1 2115 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 4 S289-2 STIS/N ACCUM 52X0.1 G230M 2095 1 2895 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 5 S289-2 STIS/N ACCUM 52X0.1 G230M 2095 1 2895 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8621( 2) - 03/02/00 08:22 - [ 12] Summary Form for Proposal 8621 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 52X0.1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACQ/PEAK ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G230M ------------------------------------------------------------------------------------------------------------------------------------ Target Names LS5130 CD-41D11048 HD14476 S285-6 S289-2 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 2095 ------------------------------------------------------------------------------------------------------------------------------------