0 Assigned ID: 4665 ----- Attempting Submission 1 (Wed May 24 21:25:04 GMT 2023) ----- 0 ----- Attempting Submission 1 (Wed Sep 13 22:52:56 GMT 2023) ----- ----- Attempting Submission 2 (Tue Jan 09 10:59:06 GMT 2024) ----- ----- Attempting Submission 3 (Fri Jan 12 15:53:48 GMT 2024) ----- 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. 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 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. D. Tubin (AIP, PI) has experience in X-ray variability of AGN, the identification of lensed QSOs and optical analysis of dual AGN and their host galaxies. G. Lamer (AIP) is deeply involved in the creation of the eROSITA catalogue and has longstanding experience with optical identification of X-ray sources. M. Krumpe (AIP) has a strong background in X-ray astronomy and AGN physics. T. Urrutia (AIP) has a strong background in optical spectroscopy and data reduction including HST data. D. Homan (AIP) has strong background in AGN in optical and X-ray data. A. Schwope (AIP) is head of the X-ray group at AIP and has longstanding experience in optical and X-ray data. R. Brogan (AIP) is a PhD student at AIP and with background in optical and X-ray analysis of changing look AGN. J. Comparat (MPE) has a leading role in the identification of X-ray sources with SDSS/SPIDERS. T. Liu (MPE) has a background in AGN and X-ray surveys. E. Bulbul (MPE) is head of the galaxy cluster group at MPE. M. Schramm (Saitama University) is very experienced with optical spectroscopy and has also worked on the identification of lensed and binary QSOs. M. Salvato (MPE) has strong background in optical and X-ray surveys. Galaxies Large Scale Structure of the Universe 6 false false false false false false false false SUPPORTED GALAXY ELLIPTICAL GRAVITATIONAL LENS QUASAR NO J2000 J2000 g=21.26, r=20.59, i=20.01, z=19.68 ACS/WFC Imaging No No F606W ACS/WFC Imaging No No F814W POS-TARG DITHER 0.2637 LINE 0.1856 false false 69.02 4 20.7 ACS-WFC-DITHER-BOX 2 false 1719342756757 /private/var/folders/b9/jx3rgsbx0tgf9j1xp52tw6km0005ml/T/OPVisit12713047364270109966.xml The scheduling data was generated by CASM 32.1.1. CASM was run in Phase II mode. 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