16507( 2) - 22-Mar-2021 15:57:37 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 16507 Version: 2 Check-in Time: 22-Mar-2021 15:57:37 STScI Edit Number: 0 Title Identifying a Gravitationally Lensed Quasar or A Close Quasar Pair at z=5.66 ------------------------------------------------------------------------------------ Type Cycle GO 28 ------------------------------------------------------------------------------------ Investigators Contact? PI: Minghao Yue University of Arizona Y CoI: Prof. Xiaohui Fan University of Arizona N CoI: Dr. Jinyi Yang University of Arizona N CoI: Dr. Feige Wang University of Arizona N ------------------------------------------------------------------------------------ Abstract We propose high-resolution ACS imaging to resolve the nature of a newly discovered double quasar system at z=5.66, J2037-4537, which could be either a close quasar pair or a gravitationally lensed quasar. Ground-based observations show that J2037-4537 consists of two point sources separated by 1.26", both of which have a spectrum of a z=5.66 quasar. However, limited by the seeing, it is uncertain whether the lens galaxy exists. The two components are either a physical quasar pair or lensed images of the same quasar. In the former case, J2037-4537 will be the highest redshift quasar pair, which will place strong constraints on the model of AGN formation and evolution, and will enable follow-up observations to study galaxy mergers that trigger quasar activity, to probe the kpc-scale structure of the intergalactic medium at z>5.5 for the first time, and to search for protocluster traced by the quasar pair. In the latter case, J2037-4537 will be the second lensed quasar discovered at z>5 and will be an excellent case study for the high-z SMBH population, aided by lensing magnification. With an Einstein ring size of 1.26", J2037-4537 will provide the best chance to detect the stellar light from a quasar host galaxy at high-z. The key to distinguishing the two scenarios is to detect the lens galaxy. However, the lens galaxy is likely only 0.3" away from the fainter quasar image, which is impossible to get resolved from the ground. Here we propose to use ACS/WFC to confirm (or rule out) the presence of the foreground lens galaxy. With a modest request of 1 orbit, we will identify J2037-4537 as either a lensing system or a close quasar pair and prepare for follow-up observations. ------------------------------------------------------------------------------------ Observations Description ------------------------ This program will perform high-resolution ACS/WFC imaging of a pair of quasar images at z=5.66, which could be either a physical quasar pair or gravitationally lensed images of the same quasar. We will use the F850LP filter. The observation is awarded one orbit which can be finished in one visit. We will do dithering to improve the image sampling. Since we only need one orbit in one visit, we do not expect that the reduced gyro mode will have a significant impact on this project. ------------------------------------------------------------------------------------ 16507( 2) - 22-Mar-2021 15:57:37 - [ 2] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 J2037-4537 GALAXY, QSO, QUASAR RA=20H37M21.2688S, J2000 DES z = 19.6 DEC=-45D37'48.47" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 16507( 2) - 22-Mar-2021 15:57:37 - [ 3] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type ACS-WFC-DITHER-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.262 Line_Spacing 0.192 Coordinate_Frame POS-TARG Pattern_Orient 18.39 Angle_Between_Sides 68.14 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 16507( 2) - 22-Mar-2021 15:57:37 - [ 4] Visit: 01 Visit Requirements: On Hold Comments: Additional Comments: 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 J2037-4537 ACS/WFC ACCUM WFC1-CTE F850LP 1 500 S PATTERN 1 1 see below (2208 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ J2037-4537 1 ACS/WFC ACCUM WFC1-CTE F850LP 1 none none none 1 552.0 S J2037-4537 1 ACS/WFC ACCUM WFC1-CTE F850LP 2 none none none 1 552.0 S J2037-4537 1 ACS/WFC ACCUM WFC1-CTE F850LP 3 none none none 1 552.0 S J2037-4537 1 ACS/WFC ACCUM WFC1-CTE F850LP 4 none none none 1 552.0 S 16507( 2) - 22-Mar-2021 15:57:37 - [ 5] Summary Form for Proposal 16507 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WFC1-CTE ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F850LP ------------------------------------------------------------------------------------------------------------------------------------ Target Names J2037-4537 ------------------------------------------------------------------------------------------------------------------------------------