! Proposal 6578, submission 1 ! PI: Ethan J. Schreier ! Received Tue Mar 12 09:26:52 EST 1996 ! From: dctaylor@stsci.edu Proposal_Information ! Section 4 Title: Optical Morphology of NGC 5128: X-ray Ridges and the Geometry of the Dust Lane Proposal_Category: GO Scientific_Category: GALAXIES & CLUSTERS Cycle: 6 Investigators PI_name: Ethan J. Schreier PI_Institution: Space Telescope Science Institute CoI_Name: Alessandro Capetti CoI_Institution: Space Telescope Science Institute Contact: ! Y or N (designate at most one contact) CoI_Name: Duccio Macchetto CoI_Institution: Space Telescope Science Institute Contact: ! Y or N (designate at most one contact) Abstract: ! Free format text (please update) We propose the first observations of NGC 5128 with WF/PC-2 to study the detailed morphology of the dust lane. We will resolve the stellar associations and determine the number, luminosities and spectral types of the sources seen along the edge of the dust lane in earlier observations with WF/PC-I. We will quantitatively check the interpretation that the X-ray ridges parallel to the dust lane are caused by massive X-ray binaries associated with young stars. Simultaneously, we will study the disk itself -- mapping the position of the stars and stellar associations along both north and south edges of the disk, possibly observing a significant number within the dust lane, and comparing the source distribution with the observed dust lane morphology, we will determine if the clustering of the bright sources is a projection of sources evenly distributed in or on a warped disk, or caused by interaction between the disk and the galaxy. Simultaneously, the possible scattering cloud near the nucleus will be studied using HST's highest available resolution in V and I. Questions ! Free format text (please update) Observing_Description: For the primary observations, we will use WF/PC-2 with three different filters, F336W, F555W and F814W. First, we will center the PC on a region of the northern edge of the dust lane so as to include a significant number of the bright sources seen by WF/PC-I. We will be able simultaneously to observe several arcminutes of the southern edge of the dust lane along the two diagonal WF chips. A second observation will include the nucleus and a region of the southern edge of the dust lane in the aperture of the PC while simultaneously observing several arcminutes of the northern edge of the dust lane in the WF chips. Note that both the north and south ridges will be observed, since there is evidence from infrared, X-ray and optical observations (and the models) that they differ. The PC provides the highest (0.046") resolution for determining the number of individual stars and cluster shapes in the crowded regions, while the WF observations will provide the necessary larger field of view. By cross-comparing these observations, we will be able to extrapolate the high resolution results to the larger FOV. The selected filters will provide the widest reasonable color range for discriminating the young blue objects, hypothesized to explain the X-ray emission, from older populations of objects. A color-color reddening-free diagram will be obtained in order to obtain spectral information independent of the dust absorption, which appears to be significant in the regions of interest. The exposure time is calculated to allow the detection of isolated stars of spectral type B3 or earlier. Given the distance modulus of Cen A, 27.7 mag assuming a distance of 3.5 Mpc, the magnitudes of a B3 star are 25.3, 26.1 and 26.3 in the U, V and I standard filters respectively. To reach these brightness limits two orbits are required with F336W, while one orbit is needed for each of the F555W and F814W filters. Thus, four orbits are required for each of the two different primary pointings, a total of 8 orbits. Real_Time_Justification: None. None. Calibration_Justification: Additional_Comments: Fixed_Targets ! Section 5.1 Target_Number: 1 Target_Name: NGC5128-RIDGEN Alternate_Names: CEN-A Description: GALAXY,Elliptical,Radio Galaxy Position: RA=13H 25M 30.3S +/- 0.1S, DEC= -43D 00' 51" +/- 1" Equinox: 2000 RV_or_Z: V = 550 RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch: Annual_Parallax: Flux: V = 7.8 +/- 0.1 Comments: Target_Number: 11 Target_Name: NGC5128-RIDGES Alternate_Names: CEN-A Description: GALAXY,Elliptical,Radio Galaxy Position: RA=13H 25M 27.8S +/- 0.1S, DEC= -43D 01' 07" +/- 1" Equinox: 2000 RV_or_Z: V = 550 RA_PM: ! Units are seconds of time per year Dec_PM: ! Units are seconds of arc per year Epoch: Annual_Parallax: Flux: V = 7.8 +/- 0.1 Comments: Visits ! Section 6 Visit_Number: 1 Visit_Requirements: ORIENT 115D TO 135D On_Hold_Comments: Visit_Comments: Exposure_Number: 11 Target_Name: NGC5128-RIDGES Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F336W Wavelength: Optional_Parameters: CR-SPLIT=0.75 Number_of_Iterations: 2 Time_Per_Exposure: 2420S Special_Requirements: Exposure_Number: 21 Target_Name: NGC5128-RIDGES Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F555W Wavelength: Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 300S Special_Requirements: Exposure_Number: 22 Target_Name: NGC5128-RIDGES Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F555W Wavelength: Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 2020S Special_Requirements: Exposure_Number: 31 Target_Name: NGC5128-RIDGES Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F814W Wavelength: Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 300S Special_Requirements: Exposure_Number: 32 Target_Name: NGC5128-RIDGES Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F814W Wavelength: Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 2020S Special_Requirements: Visit_Number: 2 Visit_Requirements: ORIENT 179D TO 181D FROM 1 On_Hold_Comments: Visit_Comments: Exposure_Number: 11 Target_Name: NGC5128-RIDGEN Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F336W Wavelength: Optional_Parameters: CR-SPLIT=0.75 Number_of_Iterations: 2 Time_Per_Exposure: 2600S Special_Requirements: Exposure_Number: 21 Target_Name: NGC5128-RIDGEN Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F555W Wavelength: Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 300S Special_Requirements: Exposure_Number: 22 Target_Name: NGC5128-RIDGEN Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F555W Wavelength: Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 2200S Special_Requirements: Exposure_Number: 31 Target_Name: NGC5128-RIDGEN Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F814W Wavelength: Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 300S Special_Requirements: Exposure_Number: 32 Target_Name: NGC5128-RIDGEN Config: WFPC2 Opmode: IMAGE Aperture: PC1-FIX Sp_Element: F814W Wavelength: Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 2200S Special_Requirements: Data_Distribution ! Defaults indicated; change if desired Medium: 8MM ! 8MM or 6250BPI or 1600BPI Blocking_Factor: 10 ! 10 or 1 Ship_To: PI_Address ! STSCI or PI_Address or Ship_Via: UPS ! UPS (2-day) or OVERNIGHT Recipient_Email: ! Needed if Ship_To: is not PI_Address