9099( 10) - 09/21/01 08:54 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9099 Version: 10 Check-in Date: 21-Sep-2001 08:53:22 1.Proposal Title: High Spatial Resolution Spectroscopy of the Massive Globular Cluster G1 ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 10 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: R. Rich University of California - Los Angeles CoI: Dr. Luis Ho The Observatories of the Carnegie N Institution of Washington CoI: Prof. Karl Gebhardt University of Texas at Austin N ------------------------------------------------------------------------------------ 5. Abstract We propose to obtain high spatial resolution, long-slit spectroscopy of the most luminous globular cluster in the Local Group, G1 in M31. The kinematic structure obtained with these data will provide a stringent test of whether a central black hole exists, thereby determining whether globular clusters share the same intimate connection that normal galaxies do with their black holes. The central surface brightness of the core of this cluster reaches 13.5 V mag arcsec^-2, and the core radius of the cluster is 0.9 pc; both these properties allow for detailed kinematic information using HST. If a black hole is present, and G1 falls on the black-hole mass/sigma correlation recently established for bulges and ellipticals, the mass should be 6*10^4M_\odot, and the velocity dispersion should rise to 36 km s^-1. Detection of a black hole in G1 would extend the black-hole mass/sigma relationship to masses 100 times lower than the lowest mass nuclear black hole currently known, and establish a solid connection between the formation of galaxies and globular clusters. The data will also provide the basis for an excellent dynamical model of G1 and a study of stellar population gradients in this unique cluster. Parallel imaging with WFPC2 will produce a very deep color-magnitude diagram of the M31 halo field stars adjacent to G1. Short exposures of the M31 halo hints at a possible intermediate-age population, which may be revealed in deeper parallels. ------------------------------------------------------------------------------------ 9099( 10) - 09/21/01 08:54 - [ 2] Observations Description ------------------------ We propose to obtain a long-slit spectrum using the 52X0.1 slit placed along the major axis of G1 (the cluster is elliptical; see Rich et al. 1996). The low dispersion of G1 dictates that we must achieve high S/N, since we are near the spectral resolution limit of STIS. Based on our extensive experience with STIS and detailed simulations, we can obtain the desired accuracy of better than 10\ dispersion with a S/N ~ 50 using the G750M grating to measure the calcium infrared triplets (~8500 Angstrom). We have used this setup successfully to measure the velocity dispersion in M33 to better than 10\ dispersion than G1, 21 km s^-1 compared to 25 km s^-1. Thus, we are confident that we can obtained the desired kinematic accuracy. From the STIS exposure time calculator and our simulations, we require 3.6 hours to reach S/N = 50 at 8500 Angstrom\ at V = 13.5 mag with the 52x0.1 slit. However, the dispersion profile out to around 1.0"\ is important for the dynamical analysis. Fortunately, we only require an accuracy of 15\ radius, which implies that we only need to attain S/N = 35. Given G1's brightness profile, we estimate that, by summing across four pixels, we need a total of 7 hours. We also require the long-slit, low-resolution spectroscopy to have good S/N in order to measure accurately any gradient in the strengths of the stellar absorption features. The exposure time calculator indicates that, for Mu = 15 mag arcsec^-2, an exposure time of 3614 s will give S/N = 25 at 4000 Angstrom\ with G430L. Using G750L, we reach S/N = 25 at 6500 Angstrom\ in 1219 s. In two orbits, a total of 4800 s of exposure time is available, just enough to get good data on population gradients from spectroscopy. The existing WFPC2 images have high enough S/N for photometric analysis of G1, and we do not require further imaging. The total time is, therefore, 500 minutes. Given the typical overhead, the total number of requested orbits is 12. Rich attempted to observe G1 with the nirspec infrared echelle spectrograph on Keck, using the Adaptive Optics camera. This is the only possibility for observing G1 from the ground. The AO loop was unable to close either on the cluster, or on the 2 bright stars near the cluster. The only hope to do this observation is with HST/STIS. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9099( 10) - 09/21/01 08:54 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 G1 EXT-CLUSTER RA=00H 32M 46.535S +/- 0.05S, J2000 V=-200 SURF(V) = 15 DEC=+39D 34' 41.13" +/- 0.5", B-V = 1 PLATE-ID=02S3 Coordinate Source: HST_IMAGE 9099( 10) - 09/21/01 08:54 - [ 4] Visit: 01 Visit Priority: Visit Requirements: PCS MODE F; ORIENT 140D TO 190D; ORIENT 320D TO 10D; On Hold Comments: Additional Comments: Parallel WFPC2 images will be used for stellar phot of M31 halo field. Try to keep all visits at same position and orient so WFPC2 coincides. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 G1 STIS/C ACQ F28X50L MIRROR ACQTYPE=DIFFUSE, 1 30 S CD P DIFFUSE-CENTER=FLUX-CENTROID, CHECKBOX=9 Comments: Acquire the target. ------------------------------------------------------------------------------------------------------------------------------------ 20 G1 STIS/C ACQ/PEA 52X0.1E MIRROR 1 30 S CD K 1 Comments: Peak-up on the target in the 0.1 slit ------------------------------------------------------------------------------------------------------------------------------------ 30 G1 STIS/C ACCUM 52X0.1E G750M 8561 CR-SPLIT=2 1 1600 S PAR 35 WITH 30 CD 1 ------------------------------------------------------------------------------------------------------------------------------------ 35 ANY WFPC2 IMAGE WFALL F606W CR-SPLIT=0.5 1 1400 S ------------------------------------------------------------------------------------------------------------------------------------ 36 CCDFLAT STIS/C ACCUM 52X0.1E G750M 8561 2 DEF CD 1 ------------------------------------------------------------------------------------------------------------------------------------ 40 G1 STIS/C ACCUM 52X0.1E G750M 8561 CR-SPLIT=2 1 2800 S POS TARG 0, 1.039; PAR 45 CD 1 WITH 40 ------------------------------------------------------------------------------------------------------------------------------------ 45 ANY WFPC2 IMAGE WFALL F606W CR-SPLIT=0.5 1 2500 S ------------------------------------------------------------------------------------------------------------------------------------ 46 CCDFLAT STIS/C ACCUM 52X0.1E G750M 8561 2 DEF CD 1 ------------------------------------------------------------------------------------------------------------------------------------ 50 G1 STIS/C ACCUM 52X0.1E G750M 8561 CR-SPLIT=2 1 2800 S POS TARG 0, -1.052; PAR CD 1 55 WITH 50 ------------------------------------------------------------------------------------------------------------------------------------ 55 ANY WFPC2 IMAGE WFALL F814W CR-SPLIT=0.5 1 2500 S ------------------------------------------------------------------------------------------------------------------------------------ 56 CCDFLAT STIS/C ACCUM 52X0.1E G750M 8561 2 DEF CD 1 ------------------------------------------------------------------------------------------------------------------------------------ 60 G1 STIS/C ACCUM 52X0.1E G750M 8561 CR-SPLIT=2 1 2800 S POS TARG 0, 1.052; PAR 65 CD 1 WITH 60 ------------------------------------------------------------------------------------------------------------------------------------ 65 ANY WFPC2 IMAGE WFALL F814W CR-SPLIT=0.5 1 2500 S ------------------------------------------------------------------------------------------------------------------------------------ 66 CCDFLAT STIS/C ACCUM 52X0.1E G750M 8561 2 DEF CD 1 ------------------------------------------------------------------------------------------------------------------------------------ 9099( 10) - 09/21/01 08:54 - [ 5] Visit: 02 Visit Priority: Visit Requirements: PCS MODE F; SAME ORIENT AS 1 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 ------------------------------------------------------------------------------------------------------------------------------------ 110 G1 STIS/C ACQ F28X50L MIRROR ACQTYPE=DIFFUSE, 1 30 S CD P DIFFUSE-CENTER=FLUX-CENTROID, CHECKBOX=9 Comments: Acquire the target. ------------------------------------------------------------------------------------------------------------------------------------ 120 G1 STIS/C ACQ/PEA 52X0.1E MIRROR 1 30 S CD K 1 Comments: Peak-up on the target in the 0.1 slit ------------------------------------------------------------------------------------------------------------------------------------ 130 G1 STIS/C ACCUM 52X0.1E G750M 8561 CR-SPLIT=2 1 1600 S PAR 135 WITH 130 CD 1 ------------------------------------------------------------------------------------------------------------------------------------ 135 ANY WFPC2 IMAGE WFALL F606W CR-SPLIT=0.5 1 1400 S ------------------------------------------------------------------------------------------------------------------------------------ 136 CCDFLAT STIS/C ACCUM 52X0.1E G750M 8561 2 DEF CD 1 ------------------------------------------------------------------------------------------------------------------------------------ 140 G1 STIS/C ACCUM 52X0.1E G750M 8561 CR-SPLIT=2 1 2800 S POS TARG 0, 0.52; PAR 145 CD 1 WITH 140 ------------------------------------------------------------------------------------------------------------------------------------ 145 ANY WFPC2 IMAGE WFALL F606W CR-SPLIT=0.5 1 2500 S ------------------------------------------------------------------------------------------------------------------------------------ 146 CCDFLAT STIS/C ACCUM 52X0.1E G750M 8561 2 DEF CD 1 ------------------------------------------------------------------------------------------------------------------------------------ 150 G1 STIS/C ACCUM 52X0.1E G750M 8561 CR-SPLIT=2 1 2800 S POS TARG 0, -0.52; PAR CD 1 155 WITH 150 ------------------------------------------------------------------------------------------------------------------------------------ 155 ANY WFPC2 IMAGE WFALL F814W CR-SPLIT=0.5 1 2500 S ------------------------------------------------------------------------------------------------------------------------------------ 156 CCDFLAT STIS/C ACCUM 52X0.1E G750M 8561 2 DEF CD 1 ------------------------------------------------------------------------------------------------------------------------------------ 160 G1 STIS/C ACCUM 52X0.1E G750M 8561 CR-SPLIT=2 1 2800 S POS TARG 0, -0.72; PAR CD 1 165 WITH 160 ------------------------------------------------------------------------------------------------------------------------------------ 165 ANY WFPC2 IMAGE WFALL F814W CR-SPLIT=0.5 1 2500 S ------------------------------------------------------------------------------------------------------------------------------------ 166 CCDFLAT STIS/C ACCUM 52X0.1E G750M 8561 2 DEF CD 1 ------------------------------------------------------------------------------------------------------------------------------------ 9099( 10) - 09/21/01 08:54 - [ 6] Visit: 03 Visit Priority: Visit Requirements: PCS MODE F; SAME ORIENT AS 1 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 ------------------------------------------------------------------------------------------------------------------------------------ 210 G1 STIS/C ACQ F28X50L MIRROR ACQTYPE=DIFFUSE, 1 30 S CD P DIFFUSE-CENTER=FLUX-CENTROID, CHECKBOX=9 Comments: Acquire the target. ------------------------------------------------------------------------------------------------------------------------------------ 220 G1 STIS/C ACQ/PEA 52X0.1E MIRROR 1 30 S CD K 1 Comments: Peak-up on the target in the 0.1 slit ------------------------------------------------------------------------------------------------------------------------------------ 230 G1 STIS/C ACCUM 52X0.1E G430L 4300 CR-SPLIT=2 1 1600 S PAR 235 WITH 230 CD 1 ------------------------------------------------------------------------------------------------------------------------------------ 235 ANY WFPC2 IMAGE WFALL F606W CR-SPLIT=0.5 1 1200 S ------------------------------------------------------------------------------------------------------------------------------------ 240 G1 STIS/C ACCUM 52X0.1E G430L 4300 CR-SPLIT=2 1 2800 S POS TARG 0, 0.3; PAR 245 CD 1 WITH 240 ------------------------------------------------------------------------------------------------------------------------------------ 245 ANY WFPC2 IMAGE WFALL F606W CR-SPLIT=0.5 1 2500 S ------------------------------------------------------------------------------------------------------------------------------------ 250 G1 STIS/C ACCUM 52X0.1E G750M 8561 CR-SPLIT=2 1 2600 S POS TARG 0, -0.3; PAR 255 CD 1 WITH 250 ------------------------------------------------------------------------------------------------------------------------------------ 255 ANY WFPC2 IMAGE WFALL F814W CR-SPLIT=0.5 1 2500 S ------------------------------------------------------------------------------------------------------------------------------------ 256 CCDFLAT STIS/C ACCUM 52X0.1E G750M 8561 2 DEF CD 1 ------------------------------------------------------------------------------------------------------------------------------------ 260 G1 STIS/C ACCUM 52X0.1E G750M 8561 CR-SPLIT=2 1 2800 S POS TARG 0, -0.4; PAR 265 CD 1 WITH 260 ------------------------------------------------------------------------------------------------------------------------------------ 265 ANY WFPC2 IMAGE WFALL F814W CR-SPLIT=0.5 1 2500 S ------------------------------------------------------------------------------------------------------------------------------------ 266 CCDFLAT STIS/C ACCUM 52X0.1E G750M 8561 2 DEF CD 1 ------------------------------------------------------------------------------------------------------------------------------------ 9099( 10) - 09/21/01 08:54 - [ 7] Summary Form for Proposal 9099 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 52X0.1E1 WFALL ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACQ/PEAK ACCUM IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=DIFFUSE DIFFUSE-CENTER=FLUX-CENTROID CHECKBOX=9 CR-SPLIT=2 CR-SPLIT=0.5 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PCS MODE F; ORIENT 140D TO 190D; ORIENT 320D TO 10D; PAR 35 WITH 30 POS TARG 0, 1.039; PAR 45 WITH 40 POS TARG 0, -1.052; PAR 55 WITH 50 POS TARG 0, 1.052; PAR 65 WITH 60 PCS MODE F; SAME ORIENT AS 1 PAR 135 WITH 130 POS TARG 0, 0.52; PAR 145 WITH 140 POS TARG 0, -0.52; PAR 155 WITH 150 POS TARG 0, -0.72; PAR 165 WITH 160 PAR 235 WITH 230 POS TARG 0, 0.3; PAR 245 WITH 240 POS TARG 0, -0.3; PAR 255 WITH 250 POS TARG 0, -0.4; PAR 265 WITH 260 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G750M F606W F814W G430L ------------------------------------------------------------------------------------------------------------------------------------ Target Names G1 ANY CCDFLAT ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 8561 4300 ------------------------------------------------------------------------------------------------------------------------------------