8123( 7) - 03/14/00 06:38 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8123 Version: 7 Check-in Date: 14-Mar-2000 06:36:54 1.Proposal Title: Testing the Stellar Dynamics of Nested Bars in NGC 5728 ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 8 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Isaac Shlosman University of Kentucky CoI: Dr. David Axon Space Telescope Science Insitute N CoI: Dr. Johan Knapen University of Hertfordshire N CoI: Dr. Francoise Combes Paris Observatory N ------------------------------------------------------------------------------------ 5. Abstract NIR images of the barred galaxy NGC 5728 revealed the existence of an inner bar, twisted by a large angle, sim63^degrees relative to the primary bar. Similar bars within bars have been found in nearby galaxies, their existence in large numbers is of interest to understanding of barred galaxy dynamics and of the fueling of nuclear starbursts and AGNs. Three theoretical schemes were developed to explain this phenomena. Two require the gas self-gravity to stabilize the inner bar and have it rotating in the same direction as the primary bar at the same pattern speed or decoupled, so it rotates faster. The third supposes that the inner bar is decoupled but counter rotates relative to the primary, and alleviates the need for large gas masses required by the former models. The predicted rotational properties and velocity dispersion radial profiles of inner bars are radically different in all three cases and can be tested using longslit absorption-line spectroscopy. As yet no meaningful confrontation between the models and real galaxies was carried out, as inner bars are confined to small physical (1 kpc) and angular scales (5-7^'') and can only be well resolved with HST. We propose to acquire absorption-line spectra along the inner bar of NGC 5728 with STIS and the G750M grating at the Calcium triplet (Lambda 8498, 8542, 8662) to study its stellar dynamics. Our results will be significant in understanding host galaxy-to-central activity connection. ------------------------------------------------------------------------------------ 8123( 7) - 03/14/00 06:38 - [ 2] Observations Description ------------------------ We propose to acquire absorption-line spectra along the inner bar of NGC 5728 (PA=85^degrees), and parallel to its primary bar (PA=22^degrees), with STIS and the G750M grating at the Calcium Triplet (Lambda 8498, 8542, 8662) to investigate its stellar dynamics. At these wavelngths the HST has the major observational advantage of not suffering from the heavy night sky contamination which hampers calcium triplet studies from the ground. The HST provides us with sufficient spatial resolution to obtain between 20 to 30 independent velocity and velocity dispersion measurements along the inner bar, compared with only 3 or 4 from the ground. This enables a clean separation between the inner and outer bars in the subsequent model building. We shall use an 0.2^''-wide slit which will give us more than adequate spectral resolution of 100 kms. We have estimated our integration time both from our ground-based data, from optical spectra taken from the literature, and from archival HST F718M band imaging of the galaxy. We calculate that we shall need 4 orbits ~10, 000 secs per slit position to yield a S/N >10 (typically between 10 and 30) and thus easily measurable velocity and velocity dispersion fields at spatial resolutions between 0.2^'' and 0.5^'' per bin. With the high resolution bins in the central 3 arcseconds, in the high surface brightness part of the bar, and increasingly larger bins in the outer-parts. The estimated surface brightness in the region of interest in Fig. 1 ranges from 2.310^-15 to 2.10^-16\ erg\ cm^-2\ s^-1 A^-1\ arsec^-2. The strength of the stellar contribution to the integrated light in the center of NGC 5728 is confirmed by independent (low dispersion) emission- line spectra undertaken for another project (Axon & Robinson 1996). These data show clearly deep absorption features from Ca H &\ K Mgb and the Ca triplet from the dominant old star population in the central regions. However, such spectra have only ~5Angstrom\ resolution and are totally inadequate for the stellar dynamics test we propose to undertake here. Even so, we do not anticipate complications resulting from any nonstellar contribution within the central regions of this system. Because we will be working in a wavelength range in which fringing is important we will devote 2 minutes per orbit (including overhead) to obtain a fringe flat. On orbit experience with STIS shows that excellent fringe removal can then be accomplished. A scaled-down program concentrating purely on the inner bar is also scientifically viable. But we strongly prefer to get the data at a matched spatial scale on the primary bar as well, as its dynamical properties in the inner parts will be confused by seeing with the secondary bar in the ground-based data. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 8123( 7) - 03/14/00 06:38 - [ 3] Data Distribution Paper Products: YES Media: ELECTRONIC Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 8123( 7) - 03/14/00 06:38 - [ 4] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC5728 GALAXY, SPIRAL RA=14H 39M 36.8S +/- 1", DEC=- B1950 V = V = 11.45+/-0.22 17D 2' 26.0" +/- 1" +2788 B-V = 0.92+/-0.02 SURF(8500)=1.2+/-1e-15 SURF-LINE(8500)=2+/-0.5e-15 8123( 7) - 03/14/00 06:38 - [ 5] Visit: 01 Visit Priority: Visit Requirements: ORIENT 126D TO 136D ORIENT 306D TO 316D SCHED 50% On Hold Comments: Additional Comments: Inner bar Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC5728 STIS/C ACQ F28X50L MIRROR 1 10 S ONBOARD ACQ FOR 20, 30, CD P 40, 60, 80, 100 ------------------------------------------------------------------------------------------------------------------------------------ 20 NGC5728 STIS/C ACQ/PEA 52X0.1 MIRROR 1 20 S ONBOARD ACQ FOR 30, 40, CD K 60, 80, 100 ------------------------------------------------------------------------------------------------------------------------------------ 30 NGC5728 STIS/C ACCUM 52X0.1 G750M 6581 CR-SPLIT=2,PATTERN=PERP-TO-SLIT, 1 510 S POS TARG -0.25, 0 CD NUM-POS=3,STEP-SIZE=0.25, PATTERN-DIRECTION=PLUS ------------------------------------------------------------------------------------------------------------------------------------ 40 NGC5728 STIS/C ACCUM 52X0.1 G750M 8561 PATTERN=ALONG-SLIT,NUM-POS=2, 1 1400 S POS TARG 0, 0 CD STEP-SIZE=0.507, PATTERN-DIRECTION=PLUS, CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ 50 CCDFLAT STIS/C ACCUM 52X0.1 G750M 8561 2 DEF CD ------------------------------------------------------------------------------------------------------------------------------------ 60 NGC5728 STIS/C ACCUM 52X0.1 G750M 8561 PATTERN=ALONG-SLIT,NUM-POS=2, 1 1400 S CD STEP-SIZE=0.507, PATTERN-DIRECTION=MINUS, CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ 70 CCDFLAT STIS/C ACCUM 52X0.1 G750M 8561 2 DEF CD ------------------------------------------------------------------------------------------------------------------------------------ 80 NGC5728 STIS/C ACCUM 52X0.1 G750M 8561 PATTERN=ALONG-SLIT,NUM-POS=2, 1 1400 S CD STEP-SIZE=0.507, PATTERN-DIRECTION=PLUS, CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ 90 CCDFLAT STIS/C ACCUM 52X0.1 G750M 8561 2 DEF CD ------------------------------------------------------------------------------------------------------------------------------------ 100 NGC5728 STIS/C ACCUM 52X0.1 G750M 8561 PATTERN=ALONG-SLIT,NUM-POS=2, 1 1400 S CD STEP-SIZE=0.507, PATTERN-DIRECTION=MINUS, CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ 110 CCDFLAT STIS/C ACCUM 52X0.1 G750M 8561 2 DEF CD ------------------------------------------------------------------------------------------------------------------------------------ 8123( 7) - 03/14/00 06:38 - [ 6] Visit: 02 Visit Priority: Visit Requirements: ORIENT 126D TO 136D ORIENT 306D TO 316D SCHED 50% On Hold Comments: Additional Comments: Inner bar Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 NGC5728 STIS/C ACQ F28X50L MIRROR 1 10 S CD P ------------------------------------------------------------------------------------------------------------------------------------ 20 NGC5728 STIS/C ACCUM 52X0.2 G750M 8561 CR-SPLIT=NO,BINAXIS1=2,BINAXIS2=2 1 2280 S POS TARG 0,-1.5213 MAX CD DUR 100% ------------------------------------------------------------------------------------------------------------------------------------ 30 CCDFLAT STIS/C ACCUM 52X0.2 G750M 8561 BINAXIS1=2,BINAXIS2=2 2 DEF CD ------------------------------------------------------------------------------------------------------------------------------------ 40 NGC5728 STIS/C ACCUM 52X0.2 G750M 8561 CR-SPLIT=NO,BINAXIS1=2,BINAXIS2=2 1 1400 S POS TARG 0,-0.76065 CD ------------------------------------------------------------------------------------------------------------------------------------ 50 NGC5728 STIS/C ACCUM 52X0.2 G750M 8561 CR-SPLIT=NO,BINAXIS1=2,BINAXIS2=2 1 1400 S POS TARG 0, 0 CD ------------------------------------------------------------------------------------------------------------------------------------ 60 CCDFLAT STIS/C ACCUM 52X0.2 G750M 8561 BINAXIS1=2,BINAXIS2=2 2 DEF CD ------------------------------------------------------------------------------------------------------------------------------------ 70 NGC5728 STIS/C ACCUM 52X0.2 G750M 8561 CR-SPLIT=NO,BINAXIS1=2,BINAXIS2=2 1 1400 S POS TARG 0, 0.76065 CD ------------------------------------------------------------------------------------------------------------------------------------ 80 NGC5728 STIS/C ACCUM 52X0.2 G750M 8561 CR-SPLIT=NO,BINAXIS1=2,BINAXIS2=2 1 1400 S POS TARG 0, 1.5213 CD ------------------------------------------------------------------------------------------------------------------------------------ 90 CCDFLAT STIS/C ACCUM 52X0.2 G750M 8561 BINAXIS1=2,BINAXIS2=2 2 DEF CD ------------------------------------------------------------------------------------------------------------------------------------ 8123( 7) - 03/14/00 06:38 - [ 7] Summary Form for Proposal 8123 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 52X0.1 52X0.2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACQ/PEAK ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=2 PATTERN=PERP-TO-SLIT NUM-POS=3 STEP-SIZE=0.25 PATTERN-DIRECTION=PLUS CR-SPLIT=NO PATTERN-DIRECTION=MINUS STEP-SIZE=0.507 NUM-POS=2 BINAXIS2=2 BINAXIS1=2 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 126D TO 136D ORIENT 306D TO 316D SCHED 50% ONBOARD ACQ FOR 20, 30, 40, 60, 80, 100 ONBOARD ACQ FOR 30, 40, 60, 80, 100 POS TARG -0.25, 0 POS TARG 0, 0 POS TARG 0,-1.5213 MAX DUR 100% POS TARG 0,-0.76065 POS TARG 0, 0.76065 POS TARG 0, 1.5213 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G750M ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC5728 CCDFLAT ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 6581 8561 ------------------------------------------------------------------------------------------------------------------------------------