6822( 4) - 02/03/97 15:17 - [ 0] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6822 Version: 4 Check-in Date: 03-Feb-1997 15:13:30 1.Proposal Title: Ionized Gas with Broad Emission Lines in the Nuclei of Ellipticals ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle GALAXIES & CLUSTERS GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: PAUL GOUDFROOIJ SPACE TELESCOPE SCIENCE INSTITUTE CoI: Eric Emsellem European Southern Observatory, Germany N CoI: Frank van den Bosch Leiden Observatory, The Netherlands N ------------------------------------------------------------------------------------ 6. Abstract Ionized gas disks in the central regions of elliptical galaxies have proven to be a powerful tool for the determination of the true spatial shape and the central mass- to-light ratio of their host galaxies. We have obtained ground-based spectroscopic data which show that some of these ellipticals with ionized gas exhibit broad forbidden emission lines in their central regions. These might hint for the presence of either highly turbulent gas motions or a central dark mass. However, we are currently unable to distinguish between these two possibilities since we do not know the central distribution of the gas. We therefore propose to use WFPC2 to obtain V and I broad band images as well as narrow band images centered on the H-alpha+[N II] emission lines for 3 ellipticals in our sample: NGC 2325, NGC 2974, and NGC 3136. These galaxies are low radio emitters and show broad [N II] and [S II] emission lines. Detailed (photometric and dynamical) models will be constructed in an attempt to reproduce the observed surface brightness, flux distribution of the gas, and optical depth of the dust. Subsequently, we will derive theoretical line profiles of the ionized gas. These will be compared with our ground-based spectroscopy in order to constrain the mass of a possible central dark mass, and the amount of turbulence. ------------------------------------------------------------------------------------ Observations Description ------------------------ H-alpha+[N II] on-band images of each galaxy will be taken using the Linear Ramp Filter (LRF). To obtain the required wavelengths with the LRF, the FR680P15 configuration must be used with the galaxy centered at the appropriate place on the PC1 CCD (pixels of 0.046'' * 0.046''). The useful field of view will cover the entire line emitting region. To study the stellar mass distribution of each galaxy, Broad-band images will be taken of each galaxy, using the F547M and F814W filters. The broad-band images will be obtained with the galaxy centered on the PC1 CCD. For the redshifts of the galaxies in our sample, these filters will be free from emission lines, and will thus also serve as continuum images (to be scaled and subtracted from the on-band images, cf. Goudfrooij et al. 1994, A&AS 105, 341). Using two different broad-band filters provides a means to study the wavelength dependence of the dust (if present). Images will be split to facilitate cosmic ray removal. CHOICE OF FILTERS, TARGET POSITIONINGS AND EXPOSURE TIMES: The H-alpha+[N II] emission lines in the three galaxies in our sample are redshifted by an amount such that there is no suitable FxxxN narrow-band filter available with WFPC2 for studying them. We will therefore use the LRF as `on-band' filter. At the redshifts of the three galaxies in our sample, the H-alpha+[N II] emission lines will be positioned on the PC1 CCD (using the FR680P15 configuration). We aim to study the morphology of the central 10 arcsec of the emission-line region in the galaxies in our sample, so that the useful field of view of the LRF configuration is sufficient for our purposes. We will also obtain broad-band images with the F547M and F814W filters, with the galaxies centered on the PC1 CCD. We use these filters for the following reasons: (i) the wavelength regions covered by the F547M and F814W filters are free of emission lines at the redshifts of the three galaxies in our sample. The F547M and F814W images can thus serve to construct `continuum' (or `off-band') images which will have to be subtracted from the LRF images in order to obtain the distribution of H- alpha+[N II] emission in the nuclear regions of the galaxies (cf. Goudfrooij et al. 1994, A&AS 105, 341), (ii) it allows one to study the optical depth of the dust near the nuclei (at least NGC 2974 and NGC 3136 show dust absorption in ground-based images), (iii) the F814W filter is the best one to study the stellar light distribution -and hence the stellar mass distributions- near the nucleus of each galaxy, in view of the fact that the effect of dust absorption is least important in the far red. The exposure time per filter has been chosen so as to obtain sufficient S/N for a proper analysis for all images. We have used our flux-calibrated ground-based images in V, I, and H-alpha+[N II] to calculate the exposure times. For the broad-band imagery, we aim for a S/N = 10 (per pixel) detection of the surface brightness at a radius of 10 arcsec from the nucleus of each galaxy. For the LRF imagery, we aim for a S/N = 5 (per pixel) detection of the H-alpha+[N II] surface brightness at 5 arcsec from the nucleus of each galaxy. MINIMIZING ARTIFACTS DUE TO BRIGHT STARS NEAR THE TARGETS: We have studied ground-based V-band, I-band, and on-band (H-alpha+[N II]) CCD images of the three targets. The CCD images have a field of view of 5 * 5 arcmin. The magnitudes and positions of all stars in the field were measured. In all three cases, there are stars with V < 14 within 1.5 arcmin from the nuclei of the galaxies in our sample, which can cause artifacts in the data. To overcome artifacts associated with the presence of these stars, we have identified the telescope ORIENTations in which the positions of these stars avoid: (i) the area covered by the PC1 CCD (which is the CCD of interest for this programme), (ii) the "PC ghost regions", and (iii) the "Dragon's Breath Region" (cf. "Field Guide to WFPC2 Image Anomalies"). These telescope ORIENTations are given below for each target as Special Requirements. When the exact ORIENTations have been determined for each visit, we request that the PI be informed about them so that we can update the POS TARG optional parameters for the visits. EXPOSURE STRATEGY (COSMIC RAYS; HOT PIXELS; GAIN SETTING): To ensure that we will be able to identify and remove all cosmic ray hits, we will obtain at least two exposures with each filter. For the I and LRF filters, one of the exposures will be obtained with the target shifted by a small integer number of pixels. This allows the identification of hot pixels during the data reduction stage. We expect less than 3000 photons from the galaxies in all PC1 images, which ensures that no problems related to ADC saturation are expected to occur. We will therefore use the low gain setting (ATD-GAIN = 7) for all exposures. OPEN ISSUES: When the exact ORIENTations have been determined for each visit, we request that the PI be informed about them so that we can update the POS TARG optional parameters for the visits. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- NO MODIFICATIONS OF ANY KIND SHOULD BE MADE TO THIS PROGRAM WITHOUT CONSULTING THE PI FIRST. ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6822( 4) - 02/03/97 15:17 - [ 1] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NGC2325 GALAXY, Elliptical, RA = 7H 2M 40.20S +/- 0.02S, DEC J2000 V = SURF(B) = 19.4+/-0.2 Liner = -28D 41' 50.3" +/- 0.3", PLATE +2248 SURF(V) = 18.0+/-0.2 -ID = 04J5 SURF-LINE(6583)=44+/-5e-16 Comments: Surface brightness values are those measured in the nucleus from ground-based CCD images and spectra. 2 NGC2974 GALAXY, Elliptical, RA = 9H 42M 33.24S +/- 0.02S, J2000 V = SURF(B) = 17.7+/-0.2 Liner DEC = -03D 41' 56.9" +/- 0.3", +2011 SURF(V) = 16.3+/-0.2 PLATE-ID = 04MZ SURF-LINE(6583)=244+/-25e-16 Comments: Surface brightness values are those measured in the nucleus from ground-based CCD images and spectra. 3 NGC3136 GALAXY, Elliptical, RA = 10H 5M 46.20S +/- 0.02S, J2000 V = SURF(B) = 17.9+/-0.2 Liner DEC = -67D 22' 40.5" +/- 0.3", +1696 SURF(V) = 16.4+/-0.2 PLATE-ID = 060U SURF-LINE(6583)=103+/-10e-16 Comments: Surface brightness values are those measured in the nucleus from ground-based CCD images and spectra. 6822( 4) - 02/03/97 15:17 - [ 2] Visit: 01 Visit Requirements: ORIENT 315D TO 15D On Hold Comments: Additional Comments: ORIENT chosen so as to avoid the presence of bright, nearby stars in the "ghost regions" of the PC1 CCD, and still keeping an acceptable schedulability. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 11 NGC2325 WFPC2 IMAGE PC1-FIX F547M CR-SPLIT=0.3,CR-TOLERANCE=0.1 1 1600 S POS TARG 0.0,0.0 Comments: POS TARG to be updated by PI after exact ORIENT for visit is known. 435 e-/pix expected on galaxy nucleus in 1100 sec. ------------------------------------------------------------------------------------------------------------------------------------ 13 NGC2325 WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 100 S POS TARG 0.0,0.0 Comments: 136 e-/pix expected on galaxy nucleus. ------------------------------------------------------------------------------------------------------------------------------------ 14 NGC2325 WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 300 S POS TARG 0.506,0.0 Comments: Target position shifted by 11 PC1 pixels with respect to position of exp. 13. 420 e-/pix expected on galaxy nucleus. POS TARG to be updated by PI after exact ORIENT for visit is known. ------------------------------------------------------------------------------------------------------------------------------------ 15 NGC2325 WFPC2 IMAGE LRF LRF 6625 CR-SPLIT=NO 1 2700 S POS TARG 0.0,0.0 Comments: In 2700 s, we estimate 192 e-/pix from galaxy continuum, and 48 e-/pix from line emission in the galaxy nucleus. POS TARG to be updated by PI after exact ORIENT for visit is known. ------------------------------------------------------------------------------------------------------------------------------------ 17 NGC2325 WFPC2 IMAGE LRF LRF 6625 CR-SPLIT=0.3,CR-TOLERANCE=0.1 1 2600 S POS TARG -0.506,-0.138 Comments: POS TARG represents 0.524 arcsec offset relative to POS TARG of exp. 15; offset is in direction of constant LRF wavelength. POS TARG to be updated by PI after exact ORIENT for visit is known. ------------------------------------------------------------------------------------------------------------------------------------ 6822( 4) - 02/03/97 15:17 - [ 3] Visit: 02 Visit Requirements: ORIENT 325D TO 125D On Hold Comments: Additional Comments: ORIENT chosen so as to avoid the presence of a bright, nearby star in the "ghost region" of the PC1 CCD. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 21 NGC2974 WFPC2 IMAGE PC1-FIX F547M CR-SPLIT=0.3,CR-TOLERANCE=0.1 1 1500 S Comments: 1895 e-/pix expected on galaxy nucleus in 1000 s. ------------------------------------------------------------------------------------------------------------------------------------ 23 NGC2974 WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 200 S POS TARG 0.0,0.0 Comments: 1391 e-/pix expected on galaxy nucleus. ------------------------------------------------------------------------------------------------------------------------------------ 24 NGC2974 WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 300 S POS TARG 0.506,0.0 Comments: Target position shifted by 11 PC1 pixels with respect to position of exp. 23. 2087 e-/pix expected on galaxy nucleus. ------------------------------------------------------------------------------------------------------------------------------------ 25 NGC2974 WFPC2 IMAGE LRF LRF 6620 CR-SPLIT=NO 1 2700 S POS TARG 0.0,0.0 Comments: 935 continuum e-/pix and 146 emission-line e-/pix expected on galaxy nucleus. ------------------------------------------------------------------------------------------------------------------------------------ 27 NGC2974 WFPC2 IMAGE LRF LRF 6620 CR-SPLIT=0.3,CR-TOLERANCE=0.1 1 2500 S POS TARG -0.506,-0.138 Comments: POS TARG represents 0.524 arcsec offset relative to POS TARG of exp. 25; offset is in direction of constant LRF wavelength. ------------------------------------------------------------------------------------------------------------------------------------ 6822( 4) - 02/03/97 15:17 - [ 4] Visit: 03 Visit Requirements: ORIENT 55D TO 285D CVZ On Hold Comments: Additional Comments: ORIENT chosen so as to avoid the presence of bright, nearby stars (V < 14) in the "ghost regions" of the PC1 CCD. Exact POS TARGs for the different exposures to be updated by the PI after exact ORIENT for this visit is known. Target is in CVZ, and we require the use of the CVZ to obtain high enough S/N within 2 orbits. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 31 NGC3136 WFPC2 IMAGE PC1-FIX F547M CR-SPLIT=0.3,CR-TOLERANCE=0.1 1 1400 S POS TARG 0.0,0.0 Comments: Exact POS TARG to be updated by the PI after exact ORIENT for the visit is known. 1553 e-/pix expected on galaxy nucleus in 900 s. ------------------------------------------------------------------------------------------------------------------------------------ 33 NGC3136 WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 100 S POS TARG 0.0,0.0 Comments: 741 e-/pix expected on galaxy nucleus. ------------------------------------------------------------------------------------------------------------------------------------ 34 NGC3136 WFPC2 IMAGE PC1-FIX F814W CR-SPLIT=NO 1 300 S POS TARG 0.506,0.0 Comments: Target position shifted by 11 PC1 pixels from position of exp. 33. Exact POS TARG to be updated by the PI after exact ORIENT for the visit is known. 2224 e-/pix expected on galaxy nucleus. ------------------------------------------------------------------------------------------------------------------------------------ 35 NGC3136 WFPC2 IMAGE LRF LRF 6612 CR-SPLIT=NO 1 2300 S POS TARG 0.0,0.0 Comments: Exact POS TARG to be updated by the PI after exact ORIENT for the visit is known. 753 continuum e-/pix and 49 emission-line e-/pix expected on galaxy nucleus. ------------------------------------------------------------------------------------------------------------------------------------ 36 NGC3136 WFPC2 IMAGE LRF LRF 6612 CR-SPLIT=NO 1 2500 S SAME POS AS 35 Comments: 818 continuum e-/pix and 54 emission-line e-/pix expected on galaxy nucleus. ------------------------------------------------------------------------------------------------------------------------------------ 37 NGC3136 WFPC2 IMAGE LRF LRF 6612 CR-SPLIT=NO 1 2700 S POS TARG -0.506,-0.138 Comments: POS TARG shifted by 0.544 arcsec from exp. 35 , in direction of constant LRF wavelength. Exact POS TARG to be updated by PI after exact ORIENT for visit is known. ------------------------------------------------------------------------------------------------------------------------------------ 6822( 4) - 02/03/97 15:17 - [ 5] Summary Form for Proposal 6822 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=0.3 CR-TOLERANCE=0.1 CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category GALAXIES & CLUSTERS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 315D TO 15D POS TARG 0.0,0.0 POS TARG 0.506,0.0 POS TARG -0.506,-0.138 ORIENT 325D TO 125D ORIENT 55D TO 285D CVZ SAME POS AS 35 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F547M F814W LRF ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC2325 NGC2974 NGC3136 ------------------------------------------------------------------------------------------------------------------------------------