8213( 5) - 03/01/00 07:00 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8213 Version: 5 Check-in Date: 01-Mar-2000 06:58:59 1.Proposal Title: Globular Clusters of Low Surface Brightness Galaxies ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 8 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Bryan Miller Sterrewacht Leiden CoI: Dr. Mike Fall Space Telescope Science Institute N CoI: Dr. Markus Kissler-Patig University of California Santa Cruz N CoI: Dr. Patricia Knezek The Johns Hopkins University N CoI: Dr. Stacy McGaugh University of Maryland N CoI: Dr. Brad Whitmore Space Telescope Science Institute N ------------------------------------------------------------------------------------ 5. Abstract We propose to investigate globular cluster (GC) systems in giant low surface brightness (LSB) galaxies. The primary goals of the project are to determine the number of GCs in two nearby LSB galaxies and to estimate their ages. LSB spirals tend to be more isolated, more gas rich, and have had more quiescent star formation than their high surface brightness (HSB) cousins. LSB galaxies have either been forming stars very slowly for a Hubble time or have formed within the last few Gyr. Thus, their star formation histories may be very different from those of HSB galaxies. We will use the ages of the GCs to estimate the cluster formation histories of LSBs. The colors and magnitudes of their GCs will allow us to date the clusters and put constraints on when the galaxies started to form. Thus, we may be able to distinguish whether they are very slowly evolving or very young. We will also compare the specific globular cluster frequency (number per unit luminosity) and the shap e of the GC luminosity function in LSBs with those quantities for GCs in HSB spirals. The results of this project will have important implications for galaxy and GC formation. ------------------------------------------------------------------------------------ 8213( 5) - 03/01/00 07:00 - [ 2] Observations Description ------------------------ WFPC2 images through filters F555W and F814W will be used to investigate the globular cluster systems of low surface brightness galaxies for the first time. The standard F555W and F814W bandpasses are optimal for this program since they have high sensitivity to red objects, they have accurate transformations to the Johnson-Cousins V and I system, and they will allow us to distinguish clusters from stars and OB associations. These filters have become standard for globular cluster and stellar population work. The goals of the project require the detection of cluster candidates down to the turnover of the ``universal'' old globular cluster luminosity function at M_V=-7.3. A S/N of about 10 in each bandpass at the apparent magnitude of the turnover, will give us accurate colors of the brightest clusters and confident detections down to the turnover. Because of its proximity and the expected lower number of clusters, we will go about 0.5 deeper in UGC 5981 in order to find mo re GCs and to measure the shape of the GCLF. Exposure times have been estimated using the WFPC2 exposure time calculator from STEIS and comparing them with our measurements of cluster systems in merger remnants from Cycle 4 observations (Schweizer et al. 1996; Miller et al. 1997; Whitmore et al. 1997). The table below gives distance moduli (for H_0=75), V magnitude at our desired S/N, S/N, the estimated integration time for F555W in the PC, and the resulting number of orbits for each target. The calculations assume a galaxy background of Mu_V=23 mag arcsec^ -2 and that the object is centered in the corner of the pixel. The F814W images will have the same exposure time as the F555W images. Therefore, the total time required is 2 orbits for UGC 5981 and 8 orbits for UGC 6614. Galaxy (m- M)_0 m_V S/N (sec) N_orbits^F555W UGC 5981 32.9 26.0 10 2400 1 UGC 6614 34.6 27.3 10 9600 4 Long exposures, needed to reach the turnover in the old cluster population, will be CR-SPLIT to facilitate cosmic ray removal. Short, 100 sec, exposures will also be taken of UGC 6614 since the nucleus is likely to saturate in the long exposures. For the most distant galaxy, UGC 6614, it is more likely that hot pixels will be confused with faint clusters. Therefore, for this galaxy we will also use a sub-pixel dithering scheme to improve the resolution, make it easier to remove hot pixels, and increase the sensitivity. The clusters should be concentrated towards the galaxies' nuclei so we will center all the galaxies in the PC chip. This has the added benefit of allowing us to correlate the properties of the nuclei (luminosity profile, color, dust, etc.) with the properties of the cluster systems. To make efficient use of HST will will also take images in parallel with the STIS CCD. By imaging through both the clear aperture and the longpass filter, we can measure color s similar to (B-I) for the detected objects (Gregg & Minniti 1997). In 50 minutes of exposure time we can expect to reach V~ 27 (STIS handbook). The offset field of STIS will give us a better handle on background/foreground contamination in the WFPC2 images. This is very important for statistical calculations of the number of GCs in a galaxy (see Miller et al. 1997). Real Time Justification ----------------------- None. Calibration Justification ------------------------- None. Additional Comments ------------------- None. ------------------------------------------------------------------------------------ 8213( 5) - 03/01/00 07:00 - [ 3] Data Distribution Paper Products: NO Media: DAT Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 8213( 5) - 03/01/00 07:00 - [ 4] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 UGC5981 GALAXY, LSB RA=10H 52M 3.9S +/- 0.1S, J2000 V = 2720 B = 12.3 DEC=10D 8' 54.1" +/- 0.5", PLATE -ID=0258 Comments: SA(s)c 2 UGC6614 GALAXY, LSB RA=11H 39M 14.8S +/- 0.1S, J2000 V = 6351 B = 14.4 DEC=17D 8' 37.1" +/- 0.5", PLATE -ID=019N Comments: (R)SA(r)a? 8213( 5) - 03/01/00 07:00 - [ 5] Visit: 01 Visit Priority: Visit Requirements: PCS MODE FINE 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 UGC6614 WFPC2 IMAGE PC1 F555W ATD-GAIN=7,CR-SPLIT=NO 1 1200 S PAR 3 WITH 1-2 NO SPLIT ------------------------------------------------------------------------------------------------------------------------------------ 2 UGC6614 WFPC2 IMAGE PC1 F555W ATD-GAIN=7,CR-SPLIT=NO 1 1300 S NO SPLIT SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 3 ANY STIS/C ACCUM 50CCD MIRROR 1 2600 S CD Comments: parallel ------------------------------------------------------------------------------------------------------------------------------------ 4 UGC6614 WFPC2 IMAGE PC1 F555W ATD-GAIN=7,CR-SPLIT=0.5 1 2600 S POS TARG 0.5, 0.25 PAR 5 WITH 4 ------------------------------------------------------------------------------------------------------------------------------------ 5 ANY STIS/C ACCUM 50CCD MIRROR 1 2700 S CD Comments: parallel ------------------------------------------------------------------------------------------------------------------------------------ 6 UGC6614 WFPC2 IMAGE PC1 F555W ATD-GAIN=7,CR-SPLIT=0.5 1 2600 S POS TARG 0.75, 0.75 PAR 7 WITH 6 ------------------------------------------------------------------------------------------------------------------------------------ 7 ANY STIS/C ACCUM 50CCD MIRROR 1 2700 S CD Comments: parallel ------------------------------------------------------------------------------------------------------------------------------------ 8 UGC6614 WFPC2 IMAGE PC1 F555W ATD-GAIN=7,CR-SPLIT=NO 1 1100 S POS TARG 0.25, 0.5 PAR 11 WITH 8-10 NO SPLIT ------------------------------------------------------------------------------------------------------------------------------------ 9 UGC6614 WFPC2 IMAGE PC1 F555W ATD-GAIN=7,CR-SPLIT=NO 1 1200 S NO SPLIT SAME POS AS 8 ------------------------------------------------------------------------------------------------------------------------------------ 10 UGC6614 WFPC2 IMAGE PC1 F555W ATD-GAIN=7,CR-SPLIT=NO 1 100 S NO SPLIT SAME POS AS 8 ------------------------------------------------------------------------------------------------------------------------------------ 11 ANY STIS/C ACCUM 50CCD MIRROR 1 2700 S CD Comments: parallel ------------------------------------------------------------------------------------------------------------------------------------ 8213( 5) - 03/01/00 07:00 - [ 6] Visit: 02 Visit Priority: Visit Requirements: PCS MODE FINE SAME ORIENT AS 01 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 ------------------------------------------------------------------------------------------------------------------------------------ 12 UGC6614 WFPC2 IMAGE PC1 F814W ATD-GAIN=7,CR-SPLIT=NO 1 1200 S PAR 14 WITH 12-13 NO SPLIT ------------------------------------------------------------------------------------------------------------------------------------ 13 UGC6614 WFPC2 IMAGE PC1 F814W ATD-GAIN=7,CR-SPLIT=NO 1 1300 S NO SPLIT SAME POS AS 12 ------------------------------------------------------------------------------------------------------------------------------------ 14 ANY STIS/C ACCUM F28X50L MIRROR 1 2600 S CD P Comments: parallel ------------------------------------------------------------------------------------------------------------------------------------ 15 UGC6614 WFPC2 IMAGE PC1 F814W ATD-GAIN=7,CR-SPLIT=0.5 1 2600 S POS TARG 0.5, 0.25 PAR 16 WITH 15 ------------------------------------------------------------------------------------------------------------------------------------ 16 ANY STIS/C ACCUM F28X50L MIRROR 1 2700 S CD P Comments: parallel ------------------------------------------------------------------------------------------------------------------------------------ 17 UGC6614 WFPC2 IMAGE PC1 F814W ATD-GAIN=7,CR-SPLIT=0.5 1 2600 S POS TARG 0.75, 0.75 PAR 18 WITH 17 ------------------------------------------------------------------------------------------------------------------------------------ 18 ANY STIS/C ACCUM F28X50L MIRROR 1 2700 S CD P Comments: parallel ------------------------------------------------------------------------------------------------------------------------------------ 19 UGC6614 WFPC2 IMAGE PC1 F814W ATD-GAIN=7,CR-SPLIT=NO 1 1100 S POS TARG 0.25, 0.5 PAR 22 WITH 19-21 NO SPLIT ------------------------------------------------------------------------------------------------------------------------------------ 20 UGC6614 WFPC2 IMAGE PC1 F814W ATD-GAIN=7,CR-SPLIT=NO 1 1200 S SAME POS AS 19 NO SPLIT ------------------------------------------------------------------------------------------------------------------------------------ 21 UGC6614 WFPC2 IMAGE PC1 F814W ATD-GAIN=7,CR-SPLIT=NO 1 100 S SAME POS AS 19 ------------------------------------------------------------------------------------------------------------------------------------ 22 ANY STIS/C ACCUM F28X50L MIRROR 1 2700 S CD P Comments: parallel ------------------------------------------------------------------------------------------------------------------------------------ 8213( 5) - 03/01/00 07:00 - [ 7] Visit: 03 Visit Priority: Visit Requirements: PCS MODE FINE 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 ------------------------------------------------------------------------------------------------------------------------------------ 23 UGC5981 WFPC2 IMAGE PC1 F555W ATD-GAIN=7,CR-SPLIT=NO 1 1200 S PAR 25 WITH 23-24 NO SPLIT ------------------------------------------------------------------------------------------------------------------------------------ 24 UGC5981 WFPC2 IMAGE PC1 F555W ATD-GAIN=7,CR-SPLIT=NO 1 1300 S NO SPLIT ------------------------------------------------------------------------------------------------------------------------------------ 25 ANY STIS/C ACCUM 50CCD MIRROR 1 2600 S CD Comments: parallel ------------------------------------------------------------------------------------------------------------------------------------ 26 UGC5981 WFPC2 IMAGE PC1 F814W ATD-GAIN=7,CR-SPLIT=0.5 1 2600 S PAR 27 WITH 26 ------------------------------------------------------------------------------------------------------------------------------------ 27 ANY STIS/C ACCUM F28X50L MIRROR 1 2700 S CD P Comments: parallel ------------------------------------------------------------------------------------------------------------------------------------ 8213( 5) - 03/01/00 07:00 - [ 8] Summary Form for Proposal 8213 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PC1 50CCD F28X50LP ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 STIS/CCD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ATD-GAIN=7 CR-SPLIT=NO CR-SPLIT=0.5 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PCS MODE FINE PAR 3 WITH 1-2 NO SPLIT NO SPLIT SAME POS AS 1 POS TARG 0.5, 0.25 PAR 5 WITH 4 POS TARG 0.75, 0.75 PAR 7 WITH 6 POS TARG 0.25, 0.5 PAR 11 WITH 8-10 NO SPLIT NO SPLIT SAME POS AS 8 PCS MODE FINE SAME ORIENT AS 01 PAR 14 WITH 12-13 NO SPLIT NO SPLIT SAME POS AS 12 POS TARG 0.5, 0.25 PAR 16 WITH 15 POS TARG 0.75, 0.75 PAR 18 WITH 17 POS TARG 0.25, 0.5 PAR 22 WITH 19-21 NO SPLIT SAME POS AS 19 NO SPLIT SAME POS AS 19 PAR 25 WITH 23-24 NO SPLIT NO SPLIT PAR 27 WITH 26 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F555W MIRROR F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names UGC6614 ANY UGC5981 ------------------------------------------------------------------------------------------------------------------------------------