! Proposal 6496, submission 2
! PI: Ronald Buta
! Received Tue Apr  2 09:00:18 EST 1996
! From: sleiman@stsci.edu
Proposal_Information                          
              Title:  Nuclear Rings: Probing the Hearts of
                      Barred Galaxies
  Proposal_Category:  GO
Scientific_Category:  GALAXIES & CLUSTERS
             Cycle:    6

Investigators
     PI_name:         Ronald Buta
     PI_Institution:  University of Alabama

          CoI_Name:   Deborah Crocker
   CoI_Institution:   University of Alabama
           Contact:   N 

          CoI_Name:   Gene Byrd
   CoI_Institution:   University of Alabama
           Contact:   N 


Abstract:                                
    We propose to obtain multi-band PC1 images of two ``nuclear
    rings'' in barred galaxies, chosen on the basis of showing
    strong star formation and other characteristics in ground-
    based images. These small rings, less than 10'' in
    angular radius, are thought to trace the location of the
    inner Lindblad resonance (ILR), a 2:1 orbital resonance with
    the bar that is of great importance to the structure and
    evolution of disk galaxies.  We wish to map the detailed
    structure in and near these rings, such as dust lanes, shock
    fronts, and star-forming complexes, from the near-UV to the
    near-IR in order to examine the process of star formation in
    the resonance region and to connect the morphology to
    dynamics. We will use the data to address the following
    questions. (1) What is the rate of massive star formation in
    these rings? (2) Is the star formation in the rings continuous
    or episodic, occurring in periodic ``bursts''? (3) What is the
    luminosity function of star clusters and HII regions in the
    rings?  (4) How are dust lanes distributed around the rings,
    and what ``feeds'' the gas to the ring region? (5) How does
    the small-scale structure in the rings connect to periodic
    orbit characteristics, bar strength, pattern speed, central
    density, and the stellar distribution?  We will interpret the
    results in terms of sophisticated numerical models (including
    stars and gas) of the ILR region in a barred galaxy. The
    observations should have a significant impact on our understanding
    of nuclear activity, central starbursts, and galaxy morphology.
    The sample consists of the nuclear rings in NGC 1326 and ESO
    565-11. The former nuclear ring is about average in linear size and
    intrinsic shape, while the latter is unusually large in linear size
    and extremely oval in intrinsic shape. Together the two rings
    should provide complementary insights into the nuclear ring
    phenomenon.

Questions                       ! Free format text (please update)

     Observing_Description:

	 We will image the two nuclear rings in filters F255W (near
	 uv), F336W (Johnson U), F439W (Johnson B), F555W (Johnson V),
	 and F814W (Cousins I), and the ring of NGC 1326 in filter
	 F658N also. To deduce the required exposure times for U, B, V,
	 and I, we use surface brightnesses measured from ground-based
	 CCD images. Using these surface brightnesses, a background
	 sky brightness $\mu_V$ = 23.0 mag arcsec^-2 (both galaxies
	 have ecliptic latitudes of >30 degrees), a read noise of 5.2
	 electrons, a median dark count of 0.008/sec, and the
	 information in the WFPC2 handbook, we have deduced exposure
	 times that will allow us to get good signal-to-noise ratios in
	 the background star light in the ring regions. For filter
	 F255W, the exposure time is geared to get good signal-to-noise
	 in the associations, because the stellar background underlying
	 the rings is very faint in the near-uv. The times are contained
	 within three orbits for each galaxy.

	 The nuclear ring in NGC 1326 is very bright, and at an average
	 point (off the associations) has a surface brightness of 19.4,
	 19.0, 18.1, and 17.0 mag arcsec^-2 in U, B, V, and I,
	 respectively. Our adopted exposure times and signal-to-noise
	 ratios for these filters are:

	 F336W  23.3m  S/N per PC pix =  5.8
	 F439W  23.3m  S/N per PC pix =  8.3
	 F555W  10m    S/N per PC pix = 21.5
	 F814W  10m    S/N per PC pix = 29.5

	 The nucleus of NGC 1326 is very bright, and may saturate
	 in the split 10m exposures we have adopted for F555W and
	 F814W. We have added 60s exposures in these filters to
	 avoid any possible saturation.

	 For filter F255W, we assume that normal ``super star
	 clusters'' are in the ring. These have an absolute V-band
	 magnitude of -12.5 after allowing for 1.5 magnitudes of
	 typical extinction. At the distance of 16.9 Mpc, the apparent
	 magnitudes would be about V=18.5 and our adopted exposure time
	 of 1000s would yield a point source signal-to-noise ratio of
	 about 6.

	 NGC 1326 will also be observed with the F658N filter to
	 detect the HII regions in the ring. The faintest ones
	 detected in ground-based Halpha imaging have an Halpha
	 flux of 1.0e-16 ergs cm^-2 s^-1. Treating these as 
	 point sources, the signal-to-noise that would be reached
	 relative to the bright continuum background would be
	 7.5 in our adopted exposure time of 20m.

	 The nuclear ring of ESO 565-11 has brighter associations than
	 in NGC 1326, but the ring is physically larger and the
	 background continuum star light is fainter. The surface
	 brightness of the continuum star light underlying the ring is
	 21.1, 21.0, 20.2, and 19.2 mag arcsec^-2 for U, B, V, and I
	 respectively. Our adopted exposure times and signal-to-noise
	 ratios for these filters are:

         F336W  25m    S/N per PC pix = 1.0
	 F439W  33.3m  S/N per PC pix = 2.7 
	 F555W  10m    S/N per PC pix = 6.9
	 F814W  10m    S/N per PC pix = 7.8

	 These exposure times may saturate the brightest associations
	 in the nuclear ring, which have B=18.3, B-V=0.04, and V-I
	 =0.41. In case they are point sources, we have incorporated 
	 short exposures in F439W, F555W, and F814W to avoid this 
	 possible saturation.

	 The signal-to-noise ratio for the U-band stellar background is
	 low, but the associations in the ring would be point sources
	 for which the ratio would be much higher. The fainter of these
	 associations in the ring have a B-band magnitude of 20, and in
	 23.3M the signal-to-noise ratio would be ~70 for an estimated
	 color excess of E(B-V)=0.3 and assuming an intrinsic color
	 similar to a B0 star.

	 For the F255W filter, the signal-to-noise ratio was also
	 computed by assuming the fainter associations are point sources 
	 having B = 20 and the intrinsic color of a B0 star. For our 
	 adopted 23.3m exposure time, the signal-to-noise ratio would be 
	 ~25.

	 The radial velocity of ESO 565-11 is large enough to preclude
	 observations at Halpha with the available filters.

   Real_Time_Justification:
         None

	 Supporting optical and Fabry-Perot ground-based observations
	 of ESO 565-11 have already been obtained (Buta et al.  1995b).
	 Optical broad-band and \halpha\ images of NGC 1326 have been
	 obtained by Garcia-Barreto et al.  (1991) and Crocker et al.
	 (1995). For each galaxy, the main complementary ground-based
	 data we plan to obtain are near-IR JHK observations and
	 estimates of extinction via the H\alpha to H\beta ratio.
	 These observations will be obtained at the Cerro Tololo
	 Inter-American Observatory. The JHK observations have already
	 been scheduled for the nights of Feb. 7-8, 1996 at CTIO.

Calibration_Justification:            

      Additional_Comments:



Fixed_Targets                           ! Section 5.1
  Target_Number: 1
    Target_Name: NGC1326
Alternate_Names: ESO357-26
    Description: GALAXY,STARBURST,RING,BAR,NUCLEUS,
       Position: RA=3H 23M 56.37S +/- 0.15S,DEC=-36D 27' 51.3" +/- 2.0",PLATE-ID=02IW 
        Equinox: J2000
          RA_PM:
         Dec_PM:
          Epoch:
        RV_or_Z: V = 1362 
           Flux: V=10.5+/-0.1
		 B-V=0.88+/-0.05
		 SURF(U)=19.4+/-0.3
		 SURF(B)=19.0+/-0.3
		 SURF(V)=18.1+/-0.3
		 SURF(I)=17.0+/-0.3
		 SURF(6563)=5+/-2e-15
		 E(B-V)=0.03+/-0.02
       Comments:

Fixed_Targets                           ! Section 5.1
  Target_Number: 2
    Target_Name: ESO565-11
Alternate_Names: MCG-3-34-12
    Description: GALAXY,STARBURST,RING,BAR,NUCLEUS,
       Position: RA=9H 29M 16.28S +/- 0.15S,DEC=-20D 22' 44.4" +/- 2.0",PLATE-ID=04LT 
        Equinox: J2000
          RA_PM:
         Dec_PM:
          Epoch:
        RV_or_Z: V = 4775
           Flux: V=13.0+/-0.1
		 B-V=0.85+/-0.05
		 SURF(U)=21.1+/-0.3
		 SURF(B)=21.0+/-0.3
		 SURF(V)=20.2+/-0.3
		 SURF(I)=19.2+/-0.3
		 E(B-V)=0.05+/-0.02
       Comments:

! This is a template for a single visit containing a single exposure
! Repeat exposure and visit blocks as needed

Visits                                  
      Visit_Number: 1

     Exposure_Number: 1 
         Target_Name: NGC1326
              Config: WFPC2
              Opmode: IMAGE
            Aperture: PC1-FIX
          Sp_Element: F439W
          Wavelength: 4300
 Optional_Parameters: CR-SPLIT=DEF
Number_of_Iterations: 1
   Time_Per_Exposure: 1400S

     Exposure_Number: 2 
         Target_Name: NGC1326
              Config: WFPC2
              Opmode: IMAGE
            Aperture: PC1-FIX
          Sp_Element: F555W
          Wavelength: 5398
 Optional_Parameters: CR-SPLIT=NO
Number_of_Iterations: 1
   Time_Per_Exposure: 60S

     Exposure_Number: 3 
         Target_Name: NGC1326
              Config: WFPC2
              Opmode: IMAGE
            Aperture: PC1-FIX
          Sp_Element: F555W
          Wavelength: 5398
 Optional_Parameters: CR-SPLIT=0.5,CR-TOLERANCE=0.1
Number_of_Iterations: 1
   Time_Per_Exposure: 600S

     Exposure_Number: 4 
         Target_Name: NGC1326
              Config: WFPC2
              Opmode: IMAGE
            Aperture: PC1-FIX
          Sp_Element: F336W
          Wavelength: 3342
 Optional_Parameters: CR-SPLIT=DEF
Number_of_Iterations: 1
   Time_Per_Exposure: 1400S

     Exposure_Number: 5 
         Target_Name: NGC1326
              Config: WFPC2
              Opmode: IMAGE
            Aperture: PC1-FIX
          Sp_Element: F814W
          Wavelength: 7921
 Optional_Parameters: CR-SPLIT=NO
Number_of_Iterations: 1
   Time_Per_Exposure: 60S

     Exposure_Number: 6 
         Target_Name: NGC1326
              Config: WFPC2
              Opmode: IMAGE
            Aperture: PC1-FIX
          Sp_Element: F814W
          Wavelength: 7921
 Optional_Parameters: CR-SPLIT=0.5,CR-TOLERANCE=0.1
Number_of_Iterations: 1
   Time_Per_Exposure: 600S

     Exposure_Number: 7 
         Target_Name: NGC1326
              Config: WFPC2
              Opmode: IMAGE
            Aperture: PC1-FIX
          Sp_Element: F658N
          Wavelength: 6590
 Optional_Parameters: CR-SPLIT=DEF
Number_of_Iterations: 1
   Time_Per_Exposure: 1200S

     Exposure_Number: 8 
         Target_Name: NGC1326
              Config: WFPC2
              Opmode: IMAGE
            Aperture: PC1-FIX
          Sp_Element: F255W
          Wavelength: 2586
 Optional_Parameters: CR-SPLIT=DEF
Number_of_Iterations: 1
   Time_Per_Exposure: 1000S

Visits                                  
      Visit_Number: 2

     Exposure_Number: 1 
         Target_Name: ESO565-11
              Config: WFPC2
              Opmode: IMAGE
            Aperture: PC1-FIX
          Sp_Element: F439W
          Wavelength: 4300
 Optional_Parameters: CR-SPLIT=NO
Number_of_Iterations: 1
   Time_Per_Exposure: 100S

     Exposure_Number: 2 
         Target_Name: ESO565-11
              Config: WFPC2
              Opmode: IMAGE
            Aperture: PC1-FIX
          Sp_Element: F439W
          Wavelength: 4300
 Optional_Parameters: CR-SPLIT=DEF
Number_of_Iterations: 1
   Time_Per_Exposure: 1000S

     Exposure_Number: 3 
         Target_Name: ESO565-11
              Config: WFPC2
              Opmode: IMAGE
            Aperture: PC1-FIX
          Sp_Element: F439W
          Wavelength: 4300
 Optional_Parameters: CR-SPLIT=DEF
Number_of_Iterations: 1
   Time_Per_Exposure: 900S

     Exposure_Number: 4 
         Target_Name: ESO565-11
              Config: WFPC2
              Opmode: IMAGE
            Aperture: PC1-FIX
          Sp_Element: F336W
          Wavelength: 3342
 Optional_Parameters: CR-SPLIT=DEF
Number_of_Iterations: 1
   Time_Per_Exposure: 1400S

     Exposure_Number: 5 
         Target_Name: ESO565-11
              Config: WFPC2
              Opmode: IMAGE
            Aperture: PC1-FIX
          Sp_Element: F555W
          Wavelength: 5398
 Optional_Parameters: CR-SPLIT=NO
Number_of_Iterations: 1
   Time_Per_Exposure: 60S

     Exposure_Number: 6 
         Target_Name: ESO565-11
              Config: WFPC2
              Opmode: IMAGE
            Aperture: PC1-FIX
          Sp_Element: F555W
          Wavelength: 5398
 Optional_Parameters: CR-SPLIT=0.5,CR-TOLERANCE=0.1
Number_of_Iterations: 1
   Time_Per_Exposure: 600S

     Exposure_Number: 7 
         Target_Name: ESO565-11
              Config: WFPC2
              Opmode: IMAGE
            Aperture: PC1-FIX
          Sp_Element: F255W
          Wavelength: 2586
 Optional_Parameters: CR-SPLIT=DEF
Number_of_Iterations: 1
   Time_Per_Exposure: 1400S

     Exposure_Number: 8 
         Target_Name: ESO565-11
              Config: WFPC2
              Opmode: IMAGE
            Aperture: PC1-FIX
          Sp_Element: F814W
          Wavelength: 7921
 Optional_Parameters: CR-SPLIT=NO
Number_of_Iterations: 1
   Time_Per_Exposure: 60S

     Exposure_Number: 9 
         Target_Name: ESO565-11
              Config: WFPC2
              Opmode: IMAGE
            Aperture: PC1-FIX
          Sp_Element: F814W
          Wavelength: 7921
 Optional_Parameters: CR-SPLIT=0.5,CR-TOLERANCE=0.1
Number_of_Iterations: 1
   Time_Per_Exposure: 600S

Data_Distribution                       ! Defaults indicated; change if desired

         Medium:        8MM             ! 8MM or 6250BPI or 1600BPI
Blocking_Factor:        10              ! 10 or 1
                                        ! Only astronomers with very old 9-
                                        ! track tape drives should consider
                                        ! a blocking factor of 1

        Ship_To:        University of Alabama, Box 870324, Tuscaloosa, AL 35487-0324      ! STSCI or PI_Address or <free-text>
                                        ! PI Address from Phase I is:
                                        !
                                                 !  Box 870324
                                                 !  Tuscaloosa
                                                 !  35406
                                        !
                                        !
       Ship_Via:        UPS             ! UPS (2-day) or OVERNIGHT
                                        ! Overnight shipping done at PI expense

Recipient_Email: buta@sarah.astr.ua.edu ! Needed if Ship_To: is not PI_Address
                                        ! <free-text>

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! Please send a list of your likes and dislikes to your Program Coordinator