17133(  3) - 08-Jul-2022 19:15:48 - [  1]

                  HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 17133

Version:   3  Check-in Time: 08-Jul-2022 19:15:48       STScI Edit Number: 0     

Title
Mapping the morphology of the ionizing radiation from a LyC emitting galaxy at z=4.00
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Type             Cycle
GO               30       
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Investigators                                                                   
                                                                                     Contact?
    PI: Uros Mestric                      INAF-Osservatorio di Astrofisica e Scienza    Y 
                                          dello Spazio                                    
   CoI: Dr. Eros Vanzella                 INAF-Osservatorio di Astrofisica e Scienza    N 
                                          dello Spazio                                    
   CoI: Dr. Marc Rafelski                 Space Telescope Science Institute             Y 
   CoI: Prof. Mauro Giavalisco            University of Massachusetts - Amherst         N 
   CoI: Dr. Anita Zanella                 INAF - Osservatorio Astronomico di Padova     N 
   CoI: Dr. Gabriel Bartosch Caminha      Max Planck Institute for Astrophysics         N 
   CoI: Dr. Francesco Calura              INAF-Osservatorio di Astrofisica e Scienza    N 
                                          dello Spazio                                    
   CoI: Dr. Marco Castellano              INAF, Osservatorio Astronomico di Roma        N 
   CoI: Prof. Karina Caputi               Kapteyn Astronomical Institute                N 
   CoI: Dr. Andrea Comastri               INAF-Osservatorio di Astrofisica e Scienza    N 
                                          dello Spazio                                    
   CoI: Prof. Stefano Cristiani           INAF, Osservatorio Astronomico di Trieste     N 
   CoI: Dr. Guido Cupani                  INAF, Osservatorio Astronomico di Trieste     N 
   CoI: Dr. Roberto Gilli                 INAF-Osservatorio di Astrofisica e Scienza    N 
                                          dello Spazio                                    
   CoI: Dr. Claudio Grillo                University of Milan                           N 
   CoI: Mr. Zhiyuan Ji                    University of Massachusetts - Amherst         N 
   CoI: Dr. Massimo Meneghetti            INAF-Osservatorio di Astrofisica e Scienza    N 
                                          dello Spazio                                    
   CoI: Dr. Amata Mercurio                INAF, Osservatorio Astronomico di             N 
                                          Capodimonte                                     
   CoI: Dr. Marco Mignoli                 INAF-Osservatorio di Astrofisica e Scienza    N 
                                          dello Spazio                                    
   CoI: Dr. Mario Nonino                  INAF, Osservatorio Astronomico di Trieste     N 
   CoI: Piero Rosati                      University of Ferrara                         N 
   CoI: Dr. Eleonora Sani                 European Southern Observatory - Germany       N 

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Abstract

We propose multi-band WFC3 imaging of the ionizing radiation and non-ionizing       
continuum (F390W, F814W, and F140W) from the most distant and strongest Lyman       
continuum (LyC) emitting galaxy at z=4, dubbed Ion3. Available VLT/FORS2 and        
X-Shooter spectra reveal a strong LyC emission from 912 Ang down to 750 Ang, as well
as a multiple-peaked Lya profile. Unfortunately, no information on the sub-kpc      
morphology of Ion3 exist at any wavelengths. This information is vital to constrain 
the detailed mechanisms that regulate the emission of LyC radiation from            
star-forming galaxies, especially at 3<z<4, the highest redshift likely to yield    
direct observations of LyC and the closest to the Epoch of Reionization. With this  
program we will map the morphology and extent of the LyC and non-ionizing radiation 
(NUV and FUV) that emerge from Ion3. The HST imaging is essential to (1) investigate
                                                  17133(  3) - 08-Jul-2022 19:15:48 - [  2]

the size and light profile of the LyC emission, locate its centroid and study if it 
is co-spatial or off-centered with respect to the FUV and NUV emission; (2) measure 
the Balmer break, providing us with age estimates and insight into underlying old   
stellar population. The HST multi-band imaging will enable us to understand the     
physical properties of Ion3 and to compare it with those from other detected LyC    
emitters at high and lower redshift. This will provide the unique opportunity to    
unveil the mechanisms that regulate the escape of ionizing photons from the LyC     
galaxy that is the closest in time to those at the EoR.                             
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  Observations Description
  ------------------------

     This program images a Lyman continuum emitter at z~4 with the F390W, F814W, and
     F140W filters to obtain rest-frame FUV through NUV imaging data. Full orbit    
     integrations are obtained for F390W in order to minimize post-flash and        
     read-noise and maximize the total depth. We break up F390W observations into   
     three visits of 3 orbits to aid in scheduling, but emaphsize the necessity of  
     having 3 exposures per visit to be able to sufficiently clean cosmic rays for  
     alignment and combining all 9 exposures. F390W do not require post-flash to    
     reach sufficient background per pixel, but F814W requires 3e- due to 4         
     exposures in the 1 orbit to obtain a very clean image.                         
                                                                                    
     The target is placed at the CTE optimized location (near readout on Chip C) via
     the CTE aperture for F390W and F814W. For F140W we keep the target in the      
     center. Given the possiple orientations of the WFC3/UVIS observations, the     
     fraction of overlap of the WFC3/UVIS and WFC3/IR could vary a lot. We add an   
     additional POSTARG to the WFC3/IR observations to overlap the WFC3/UVIS and    
     WFC3/IR data and avoid the bright star. Lastly, we allow the ORIENT for the    
     F814W and F140W visits to vary by +-5 degrees to ensure overlap but aid in     
     scheduling of the observations.                                                
                                                                                    
     Each filter utilizes a different dither pattern. The two WFC3/UVIS visits use a
     larger than default pattern to help minimize the blotchy pattern observed in   
     F336W imaging (i.e., similar to that seen in Rafelski et al. 2015, AJ, 150 31, 
     Figure 15) and to dither over the chip gap. For F390W, we use three 3-point    
     dither patterns with each visit offset from the other two by 3" in both x and  
     y. The 3 point dither pattern point spacing is increased by a factor of 9. For 
     F814W, we use the standard 4-point box pattern with the point and line spacing 
     multiplied by a factor of 19.                                                  
                                                                                    
     We tie the orient of the different visits to each other as stated in the phase 
     I special requirements. We also specify an orient range to avoid placing the   
     bright v_mag=8.5 star on the detector, and try to keep the bright star         
     sufficiently far away from the detector to minimize dragon's breath.           
                                                                                    
     Our program is not significantly affected by the possibility of one gyro mode. 
     While we do have an orient constraint, we could place the target on a different
     part of the detector if necessary to support a different orient while avoiding 
     the bright star. This is not ideal, but would enable more flexibility in one   
     gyro mode.                                                                     
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                                                  17133(  3) - 08-Jul-2022 19:15:48 - [  3]

TARGET LIST    Fixed Targets
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Tar|   Target   |         Target        |            Target              |Coord   | Radial |             Flux data
No |    Name    |       Description     |           Position             |Eqnx    |  Vel.  |
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1   ION3         GALAXY, HIGH REDSHIFT   RA=22H48M56.7140S,               J2000             V = 24.96 +/- 0.10 R-band=23.72+/-0.05; 
                 GALAXY                  DEC=-44D34'46.10"                                  I-band= 23.91+/-0.05                    
    Reference Frame: ICRS    Extended: YES
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                                                  17133(  3) - 08-Jul-2022 19:15:48 - [  4]

Patterns
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Pattern_Number: 1

                    Primary_Pattern                   Secondary_Pattern                
Pattern_Type        WFC3-UVIS-DITHER-BOX                                               
Pattern_Purpose     DITHER                                                             
Number_Of_Points    4                                                                  
Point_Spacing       3.287                                                              
Line_Spacing        2.128                                                              
Coordinate_Frame    POS-TARG                                                           
Pattern_Orient      23.884                                                             
Angle_Between_Sides 81.785                                                             
Center_Pattern      NO                                                                 
Pattern_Comments:     Multiplied spacing by 19 to have a wide dither pattern                                     

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Pattern_Number: 2

                    Primary_Pattern                   Secondary_Pattern                
Pattern_Type        WFC3-IR-DITHER-BOX-MIN                                             
Pattern_Purpose     DITHER                                                             
Number_Of_Points    4                                                                  
Point_Spacing       0.572                                                              
Line_Spacing        0.365                                                              
Coordinate_Frame    POS-TARG                                                           
Pattern_Orient      18.528                                                             
Angle_Between_Sides 74.653                                                             
Center_Pattern      NO                                                                 

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Pattern_Number: 3

                    Primary_Pattern                   Secondary_Pattern                
Pattern_Type        WFC3-UVIS-DITHER-LINE-3PT                                          
Pattern_Purpose     DITHER                                                             
Number_Of_Points    3                                                                  
Point_Spacing       1.215                                                              
Line_Spacing        <none>                                                             
Coordinate_Frame    POS-TARG                                                           
Pattern_Orient      46.84                                                              
Angle_Between_Sides <none>                                                             
Center_Pattern      NO                                                                 

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                                                  17133(  3) - 08-Jul-2022 19:15:48 - [  5]

Visit: 01 (F390W)
     Visit Requirements:  ORIENT 70D TO 260 D                                                                         
     On Hold Comments:    <none>                                                                                      
     Additional Comments: <none>                                                                                      


Exposures
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Exp |   Target  | Instr  | Oper. | Aper    |Spectral|Central|           Optional           |Num|   Time   |       Special
Num |    Name   | Config | Mode  | or FOV  |Element |Waveln.|          Parameters          |Exp|  (Total) |     Requirements
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1    ION3        WFC3/UVI ACCUM   UVIS2-C1K F390W                                           1   2838 S     PATTERN 3 1              
                 S                1C-CTE                                                        (8514 S)                            
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Sub Exposures
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Target             | Exp |Instr   | Oper. |  Aper  |Spectral|Cent.|Primary     |Secondary   |Iteration |CR-SPLIT  |Orbit  |Duration
Name               | Num |Config  | Mode  | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num       |Num       |Number |
------------------------------------------------------------------------------------------------------------------------------------
ION3                1     WFC3/UVI ACCUM   UVIS2-C1 F390W          1            none         none       none       1       N/A      
                          S                K1C-CTE                                                                                  
ION3                1     WFC3/UVI ACCUM   UVIS2-C1 F390W          2            none         none       none       2       N/A      
                          S                K1C-CTE                                                                                  
ION3                1     WFC3/UVI ACCUM   UVIS2-C1 F390W          3            none         none       none       3       N/A      
                          S                K1C-CTE                                                                                  
                                                  17133(  3) - 08-Jul-2022 19:15:48 - [  6]

Visit: 02 (F390W)
     Visit Requirements:  SAME ORIENT AS 01                                                                           
     On Hold Comments:    <none>                                                                                      
     Additional Comments: <none>                                                                                      


Exposures
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Exp |   Target  | Instr  | Oper. | Aper    |Spectral|Central|           Optional           |Num|   Time   |       Special
Num |    Name   | Config | Mode  | or FOV  |Element |Waveln.|          Parameters          |Exp|  (Total) |     Requirements
------------------------------------------------------------------------------------------------------------------------------------
1    ION3        WFC3/UVI ACCUM   UVIS2-C1K F390W                                           1   2838 S     POS TARG 3, 3; PATTERN 3 
                 S                1C-CTE                                                        (8514 S)   1                        
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Sub Exposures
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Target             | Exp |Instr   | Oper. |  Aper  |Spectral|Cent.|Primary     |Secondary   |Iteration |CR-SPLIT  |Orbit  |Duration
Name               | Num |Config  | Mode  | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num       |Num       |Number |
------------------------------------------------------------------------------------------------------------------------------------
ION3                1     WFC3/UVI ACCUM   UVIS2-C1 F390W          1            none         none       none       1       N/A      
                          S                K1C-CTE                                                                                  
ION3                1     WFC3/UVI ACCUM   UVIS2-C1 F390W          2            none         none       none       2       N/A      
                          S                K1C-CTE                                                                                  
ION3                1     WFC3/UVI ACCUM   UVIS2-C1 F390W          3            none         none       none       3       N/A      
                          S                K1C-CTE                                                                                  
                                                  17133(  3) - 08-Jul-2022 19:15:48 - [  7]

Visit: 03 (F390W)
     Visit Requirements:  SAME ORIENT AS 01                                                                           
     On Hold Comments:    <none>                                                                                      
     Additional Comments: <none>                                                                                      


Exposures
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Exp |   Target  | Instr  | Oper. | Aper    |Spectral|Central|           Optional           |Num|   Time   |       Special
Num |    Name   | Config | Mode  | or FOV  |Element |Waveln.|          Parameters          |Exp|  (Total) |     Requirements
------------------------------------------------------------------------------------------------------------------------------------
1    ION3        WFC3/UVI ACCUM   UVIS2-C1K F390W                                           1   2838 S     POS TARG -3, -3; PATTERN 
                 S                1C-CTE                                                        (8514 S)   3 1                      
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Sub Exposures
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Target             | Exp |Instr   | Oper. |  Aper  |Spectral|Cent.|Primary     |Secondary   |Iteration |CR-SPLIT  |Orbit  |Duration
Name               | Num |Config  | Mode  | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num       |Num       |Number |
------------------------------------------------------------------------------------------------------------------------------------
ION3                1     WFC3/UVI ACCUM   UVIS2-C1 F390W          1            none         none       none       1       N/A      
                          S                K1C-CTE                                                                                  
ION3                1     WFC3/UVI ACCUM   UVIS2-C1 F390W          2            none         none       none       2       N/A      
                          S                K1C-CTE                                                                                  
ION3                1     WFC3/UVI ACCUM   UVIS2-C1 F390W          3            none         none       none       3       N/A      
                          S                K1C-CTE                                                                                  
                                                  17133(  3) - 08-Jul-2022 19:15:48 - [  8]

Visit: 04 (F814W)
     Visit Requirements:  ORIENT -5D TO 5D FROM 01                                                                    
     On Hold Comments:    <none>                                                                                      
     Additional Comments: <none>                                                                                      


Exposures
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Exp |   Target  | Instr  | Oper. | Aper    |Spectral|Central|           Optional           |Num|   Time   |       Special
Num |    Name   | Config | Mode  | or FOV  |Element |Waveln.|          Parameters          |Exp|  (Total) |     Requirements
------------------------------------------------------------------------------------------------------------------------------------
1    ION3        WFC3/UVI ACCUM   UVIS2-C1K F814W            FLASH=3                        1   612 S      PATTERN 1 1              
                 S                1C-CTE                                                        (2448 S)                            
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Sub Exposures
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Target             | Exp |Instr   | Oper. |  Aper  |Spectral|Cent.|Primary     |Secondary   |Iteration |CR-SPLIT  |Orbit  |Duration
Name               | Num |Config  | Mode  | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num       |Num       |Number |
------------------------------------------------------------------------------------------------------------------------------------
ION3                1     WFC3/UVI ACCUM   UVIS2-C1 F814W          1            none         none       none       1       N/A      
                          S                K1C-CTE                                                                                  
ION3                1     WFC3/UVI ACCUM   UVIS2-C1 F814W          2            none         none       none       1       N/A      
                          S                K1C-CTE                                                                                  
ION3                1     WFC3/UVI ACCUM   UVIS2-C1 F814W          3            none         none       none       1       N/A      
                          S                K1C-CTE                                                                                  
ION3                1     WFC3/UVI ACCUM   UVIS2-C1 F814W          4            none         none       none       1       N/A      
                          S                K1C-CTE                                                                                  
                                                  17133(  3) - 08-Jul-2022 19:15:48 - [  9]

Visit: 05 (F140W)
     Visit Requirements:  ORIENT -5D TO 5D FROM 01                                                                    
     On Hold Comments:    <none>                                                                                      
     Additional Comments: <none>                                                                                      


Exposures
------------------------------------------------------------------------------------------------------------------------------------
Exp |   Target  | Instr  | Oper. | Aper    |Spectral|Central|           Optional           |Num|   Time   |       Special
Num |    Name   | Config | Mode  | or FOV  |Element |Waveln.|          Parameters          |Exp|  (Total) |     Requirements
------------------------------------------------------------------------------------------------------------------------------------
1    ION3        WFC3/IR  MULTIAC IR        F140W            NSAMP=14, SAMP-SEQ=SPARS50     1   DEF        POS TARG -55, -45;       
                          CUM                                                                   (2611.753  PATTERN 2 1              
                                                                                                S)                                  
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Sub Exposures
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Target             | Exp |Instr   | Oper. |  Aper  |Spectral|Cent.|Primary     |Secondary   |Iteration |CR-SPLIT  |Orbit  |Duration
Name               | Num |Config  | Mode  | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num       |Num       |Number |
------------------------------------------------------------------------------------------------------------------------------------
ION3                1     WFC3/IR  MULTIAC IR       F140W          1            none         none       none       1       N/A      
                                   CUM                                                                                              
ION3                1     WFC3/IR  MULTIAC IR       F140W          2            none         none       none       1       N/A      
                                   CUM                                                                                              
ION3                1     WFC3/IR  MULTIAC IR       F140W          3            none         none       none       1       N/A      
                                   CUM                                                                                              
ION3                1     WFC3/IR  MULTIAC IR       F140W          4            none         none       none       1       N/A      
                                   CUM                                                                                              
                                                  17133(  3) - 08-Jul-2022 19:15:48 - [ 10]

            Summary Form for Proposal  17133

  Item                         Used in this proposal                                                                              
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  Apertures                    IR, UVIS2-C1K1C-CTE                                                                                 
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  Configurations               WFC3/IR, WFC3/UVIS                                                                                  
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  Opmodes                      ACCUM, MULTIACCUM                                                                                   
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  Optional Parameters          FLASH=3, NSAMP=14, SAMP-SEQ=SPARS50                                                                 
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  Special Requirements         ORIENT -5D TO 5D FROM 01, ORIENT 70D TO 260 D, PATTERN 1 1, PATTERN 2 1, PATTERN 3 1, POS TARG -3,  
                               -3, POS TARG -55, -45, POS TARG 3, 3, SAME ORIENT AS 01                                             
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  Spectral Elements            F140W, F390W, F814W                                                                                 
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  Target Names                 ION3                                                                                                
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