6464( 3) - 02/12/96 10:09 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6464 Version: 3 Check-in Date: 12-Feb-1996 10:00:23 1.Proposal Title: RESOLVING STARS AROUND THE NEAREST KNOWN SEYFERT 1 NUCLEUS ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle AGN GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Dante Minniti Lawrence Livermore National Laboratory CoI: Pascale Jablonka Observatoire de Paris Meudon N CoI: Alex Filippenko University of California, Berkeley N CoI: Robert Fosbury Hubble Space Telescope, European N Coordinating Facility CoI: Joseph Shields Steward Observatory N ------------------------------------------------------------------------------------ 6. Abstract NGC 4395 is the least luminous and nearest known Seyfert 1 galaxy, serendipitously discovered by Filippenko & Sargent (1989). We propose to obtain deep BVI images of the nuclear region of this galaxy with the WFPC2, in order to make color- magnitude and color-color diagrams of the surrounding stars. These will allow us to determine: 1) the distance to NGC 4395, 2) the ages of the young populations around the Seyfert nucleus, 3) the ages of the old populations, and 4) their metal abundances. Our overall goal is to study how an AGN influences the circumnuclear stellar population, as well as stellar influences on nuclear activity. NGC 4395 is an important target for study since it is nearby, is almost face on, does not have a bulge, and apparently is subject to little extinction by dust in its central region. This proposal focuses on the stellar content around the active nucleus, an aspect yet unstudied, that will be complemented with the following ground and space based observations: 1) HST pre- repair optical imaging and UV spectroscopy 2) ISO emission - line spectroscopy, 3) Lick imaging and spectroscopy, and 4) Keck high resolution spectroscopy. Using the superb resolution of WFPC2 we would be able to directly test the effects of an active nucleus on the star formation history of an otherwise normal galaxy. ------------------------------------------------------------------------------------ 6464( 3) - 02/12/96 10:09 - [ 2] Observations Description ------------------------ The proposed images need to be deep enough in V and I to resolve the RGB tip (I_0 = -4.0) for the old stellar component, and photometry in B must be go sufficiently faint to measure the brightness of the blue main sequence with ages younger than ~ 10^8 yr (B_0 ~ -5). The corresponding limiting apparent magnitudes depend on the distance adopted, and for purposes of this proposal we conservatively adopt the large distance of Sandage (1988), D = 6.5 Mpc. The limiting magnitudes (S/N = 10) that we want to reach are thus B=24.1, V=26.6, and I = 25.1, corresponding to total exposure times of 10500, 2700, and 2400 sec for these bandpasses, respectively. These exposure times, computed using the new WFPC2 time calculator, add up to a total of 6 orbits., We have observed distant galaxies (D=1.5--2 Mpc) with the ESO NTT under superb seeing conditions, resolving at the limit the stars in the RGB tip (Minniti & Zijlstra 1995). However, our experience with these data indicate that similar observations of the nuclear region of NGC 4395 would not resolve the individual stars due to crowding. We have computed the expected number of tip red giant branch stars per unit area corresponding to the observed surface brightness in this region, following the procedure outlined by Renzini (1992). The resulting ~1 star/arcsec^2 determines that only HST can achieve the required resolution., In order to obtain the best possible sampling and photometry, we will use the dithering techniques developed at ST-ECF and STScI (e.g. Dickinson & Fosbury 1995, Adorf 1995). We will use DAOPHOT II, and APPHOT to do the photometric measurements, deciding from their comparative performances which one is best in this case., References, Adorf, H.-M. 1995, ST-ECF Newsletter No. 23, p. 19 Dickinson, M., & Fosbury, R. 1995, ST-ECF Newsletter No. 22, p. 14 Minniti, D., & Zijlstra, A. 1995, ApJ, to be submitted Renzini, A. 1992, in IAU Symp. 153 ``Galactic Bulges", eds. H. Dejonghe & H. Habing (Dordrecht: Kluwer), p. 151 Sandage, A. 1988, ApJ, 331, 605 Real Time Justification ----------------------- None. This proposal focuses on the stellar content around the active nucleus, an aspect yet unstudied, that will be complemented with the following ground and space based observations: 1) HST pre-repair imaging and spectroscopy, 2) ISO observations, 3) Lick imaging and spectroscopy, and 4) Keck spectroscopy. We will probably request deep K band photometry with HST + NICMOS in the next cycles. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 6464( 3) - 02/12/96 10:09 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: L.L.N.L.*MS L 413*P.O. Box 808*Livermore*CA 94550 Ship Via: UPS Email: dminniti@igpp.llnl.gov , ------------------------------------------------------------------------------------ 6464( 3) - 02/12/96 10:09 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC4395 Galaxy,Seyfert RA=12H 25M 48.80S +/- 0.1S, J2000 V=+317 V = 17.0+/-0.5 DEC=33D 32' 47.8" +/- 1" B-V = 0.36+/-0.2 Comments: Magnitude and color of the Seyfert nucleus listed. 6464( 3) - 02/12/96 10:09 - [ 5] Visit: 01 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 NGC4395 WFPC2 IMAGE PC1-FIX F555W 1 1000S ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC4395 WFPC2 IMAGE PC1-FIX F555W 1 1100S ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC4395 WFPC2 IMAGE PC1-FIX F555W 1 500S ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC4395 WFPC2 IMAGE PC1-FIX F814W DITHER- 1 80S TYPE=LINE ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC4395 WFPC2 IMAGE PC1-FIX F439W 1 1100S ------------------------------------------------------------------------------------------------------------------------------------ 6 NGC4395 WFPC2 IMAGE PC1-FIX F814W DITHER- 1 1000S TYPE=LINE ------------------------------------------------------------------------------------------------------------------------------------ 7 NGC4395 WFPC2 IMAGE PC1-FIX F439W DITHER- 1 1000S TYPE=LINE ------------------------------------------------------------------------------------------------------------------------------------ 8 NGC4395 WFPC2 IMAGE PC1-FIX F439W DITHER- 1 1000S TYPE=LINE ------------------------------------------------------------------------------------------------------------------------------------ 9 NGC4395 WFPC2 IMAGE PC1-FIX F439W DITHER- 1 1000S TYPE=LINE ------------------------------------------------------------------------------------------------------------------------------------ 6464( 3) - 02/12/96 10:09 - [ 6] Summary Form for Proposal 6464 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters DITHER-TYPE=LINE ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category AGN ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F555W F814W F439W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC4395 ------------------------------------------------------------------------------------------------------------------------------------