17444( 5) - 25-Jun-2024 19:14:20 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 17444 Version: 5 Check-in Time: 25-Jun-2024 19:14:20 STScI Edit Number: 1 Title Mapping the geometry of the new lensed quasar eRASS1 J050129.5-073309 using high resolution imaging of the lens and quasar host ------------------------------------------------------------------------------------ Type Cycle GO 31 ------------------------------------------------------------------------------------ Investigators Contact? PI: Mr. Dusan Tubin Leibniz-Institut f|*|r Astrophysik Potsdam Y (AIP) CoI: Dr. Georg Lamer Leibniz-Institut für Astrophysik Potsdam N (AIP) ------------------------------------------------------------------------------------ Abstract The newly discovered lensed quasar eRASS1 J050129.5-073309 at z = 2.47 represents a perfect laboratory to estimate the Hubble constant via time-delay cosmography, study ongoing microlensing effects, and also characterize the host galaxy properties of the quasar. The two lensed images show a time delay of 107.8 +- 8.5 days. This time-delay timescale, the brightness of the quasar, and the separation of the images make it a unique source for time-delay cosmography studies. Imaging and image modeling reveal both the lensing galaxy and tentatively the lensed image of the quasar host galaxy. We propose HST observations, with a resolution of ~0.1'', to investigate the mass profile of the lensing galaxy in order to obtain an accurate model of the lens, aiming to calculate the Hubble constant via time-delay cosmography. The high-resolution observation will also confirm the presence of lensed arcs which correspond to the host galaxy of the quasar, allowing us to constrain even more the mass distribution of the lensing galaxy. ------------------------------------------------------------------------------------ Observations Description ------------------------ The goal of this proposal is to obtain a reliable mass profile measurement of the lensing galaxy and confirm the presence of the quasar host galaxy lensed arcs in the newly discovered eRASS1 J050129.5-073309 lensed quasar. We request imaging of the lens system in the F814W and F606W filters. We choose the F814W broad filter because of the high transmission and wavelength coverage in the red bands where the lensing galaxy is brightest. This filter is ideal to map the lens which is likely an elliptical galaxy at redshift z ~ 0.7..1.0. The quasar host galaxy lensed arcs are significantly bluer in the LS DR10 images. The host galaxy dominates in the g and r band images which are covered by the ACS F606W filter. Hence the images in the two HST filters can be used to disentangle the two components in the lensed system. We use the ACS imaging exposure time calculator to deduce the exposure times for the proposed observations. GALFIT modeling of the lensing galaxy with a de-Vaucouleurs profile results in an effective radius of r = 2.7'' and Sloan magnitude of i = 19.16 for the lensing galaxy. Adopting this model, 6200 seconds of exposure time in F814W are required to reach a SNR=5.0 in a 2x2 pixel box at the effective radius of the galaxy, where the surface brightness is 24.7 mag/arcsec**2 in the i-band. Hence 2 orbits are sufficient to map the lensing galaxy with the full resolution of 0.1 arcsec out to its effective radius, well 17444( 5) - 25-Jun-2024 19:14:20 - [ 2] beyond the positions of the QSO images and the lensing arc. In the case of the filter F606W, where the lensing galaxy is fainter (r = 20.14) with the same exposure time we obtain SNR = 6 per 2x2 pixel box for a surface brightness of 24.5 mag/arcsec**2. This will be sufficient to map the profile of the lensing galaxy out to r ~ 1.5 arcsec. In the r and g bands the lensing arcs are brighter than the lensing galaxy and therefore it will be possible to image them lensed host galaxy arcs with the full resolution of HST. We note that the uncertainty on the redshift of the lens does not affect our exposure time calculation. The worst scenario is when the lensing galaxy is at z ~ 0.7. In this case, two orbits will provide images with SNR=4, which is still ideal to map and model the gravitational potential of the lensing galaxy. ------------------------------------------------------------------------------------ 17444( 5) - 25-Jun-2024 19:14:20 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 ERASS1J05012 GALAXY, ELLIPTICAL, RA=05H01M29.4480S +/- 0.01189", J2000 V = 21.26 +/- 0.02 g=21.26, r=20.59, 9.5-073309 GRAVITATIONAL LENS, DEC=-07D33'5.76" +/- 0.01111" i=20.01, z=19.68 QUASAR Reference Frame: ICRS Extended: NO Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 0.0 0.0 0.0 0 ------------------------------------------------------------------------------------------------------------------------------------ 17444( 5) - 25-Jun-2024 19:14:20 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type ACS-WFC-DITHER-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.2637 Line_Spacing 0.1856 Coordinate_Frame POS-TARG Pattern_Orient 20.7 Angle_Between_Sides 69.02 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 17444( 5) - 25-Jun-2024 19:14:20 - [ 5] 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 ERASS1J0501 ACS/WFC ACCUM WFC2 F606W 1 350 S PATTERN 2 1 29.5-073309 see below (1404 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 ERASS1J0501 ACS/WFC ACCUM WFC2 F606W 1 50 S 29.5-073309 see below (371 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 ERASS1J0501 ACS/WFC ACCUM WFC2 F814W 1 350 S PATTERN 2 3 29.5-073309 see below (1428 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 ERASS1J0501 ACS/WFC ACCUM WFC2 F814W 1 73 S 29.5-073309 see below (377 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 | ------------------------------------------------------------------------------------------------------------------------------------ ERASS1J050129.5-073 1 ACS/WFC ACCUM WFC2 F606W 1 none none none 1 351.0 S 309 ERASS1J050129.5-073 1 ACS/WFC ACCUM WFC2 F606W 2 none none none 1 351.0 S 309 ERASS1J050129.5-073 1 ACS/WFC ACCUM WFC2 F606W 3 none none none 1 351.0 S 309 ERASS1J050129.5-073 1 ACS/WFC ACCUM WFC2 F606W 4 none none none 1 351.0 S 309 ERASS1J050129.5-073 2 ACS/WFC ACCUM WFC2 F606W none none none none 1 371.0 S 309 ERASS1J050129.5-073 3 ACS/WFC ACCUM WFC2 F814W 1 none none none 2 357.0 S 309 ERASS1J050129.5-073 3 ACS/WFC ACCUM WFC2 F814W 2 none none none 2 357.0 S 309 ERASS1J050129.5-073 3 ACS/WFC ACCUM WFC2 F814W 3 none none none 2 357.0 S 309 ERASS1J050129.5-073 3 ACS/WFC ACCUM WFC2 F814W 4 none none none 2 357.0 S 309 ERASS1J050129.5-073 4 ACS/WFC ACCUM WFC2 F814W none none none none 2 377.0 S 309 17444( 5) - 25-Jun-2024 19:14:20 - [ 6] Visit: 02 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 ERASS1J0501 ACS/WFC ACCUM WFC2 F606W 1 350 S PATTERN 2 1 29.5-073309 see below (1420 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 ERASS1J0501 ACS/WFC ACCUM WFC2 F606W 1 50 S 29.5-073309 see below (355 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 ERASS1J0501 ACS/WFC ACCUM WFC2 F814W 1 350 S PATTERN 2 3 29.5-073309 see below (1424 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 ERASS1J0501 ACS/WFC ACCUM WFC2 F814W 1 73 S 29.5-073309 see below (379 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 | ------------------------------------------------------------------------------------------------------------------------------------ ERASS1J050129.5-073 1 ACS/WFC ACCUM WFC2 F606W 1 none none none 1 355.0 S 309 ERASS1J050129.5-073 1 ACS/WFC ACCUM WFC2 F606W 2 none none none 1 355.0 S 309 ERASS1J050129.5-073 1 ACS/WFC ACCUM WFC2 F606W 3 none none none 1 355.0 S 309 ERASS1J050129.5-073 1 ACS/WFC ACCUM WFC2 F606W 4 none none none 1 355.0 S 309 ERASS1J050129.5-073 2 ACS/WFC ACCUM WFC2 F606W none none none none 1 355.0 S 309 ERASS1J050129.5-073 3 ACS/WFC ACCUM WFC2 F814W 1 none none none 2 356.0 S 309 ERASS1J050129.5-073 3 ACS/WFC ACCUM WFC2 F814W 2 none none none 2 356.0 S 309 ERASS1J050129.5-073 3 ACS/WFC ACCUM WFC2 F814W 3 none none none 2 356.0 S 309 ERASS1J050129.5-073 3 ACS/WFC ACCUM WFC2 F814W 4 none none none 2 356.0 S 309 ERASS1J050129.5-073 4 ACS/WFC ACCUM WFC2 F814W none none none none 2 379.0 S 309 17444( 5) - 25-Jun-2024 19:14:20 - [ 7] Summary Form for Proposal 17444 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WFC2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 2 1, PATTERN 2 3 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names ERASS1J050129.5-073309 ------------------------------------------------------------------------------------------------------------------------------------