0Assigned ID: 1662
----- Attempting Submission 1 (Thu Apr 08 17:30:29 GMT 2021) -----
HST Phase I Proposal 1662 successfully submitted.
Receipt: # 1662-1
----- Attempting Submission 2 (Fri Apr 09 17:13:12 GMT 2021) -----
HST Phase I Proposal 1662 successfully submitted.
Receipt: # 1662-2
----- Attempting Submission 3 (Fri Apr 09 20:13:25 GMT 2021) -----0----- Attempting Submission 1 (Thu Jul 15 18:00:25 GMT 2021) -----Quasars with small proximity zones: gravitationally lensed or exceptionally young?The existence of luminous quasars hosting supermassive black holes (SMBHs) within the first billion years of cosmic history challenges our understanding of black hole growth. However, much of our understanding relies on the assumption that the observed luminosities are intrinsic to the quasars themselves. It has long been predicted that a large fraction of high-redshift quasars should be gravitationally lensed, but to date only one lensed quasar above z>5 has been confirmed despite considerable observational efforts. We propose to search for this long sought-after population of lensed quasars with HST/ACS, targeting six objects at z~6 whose rest-frame UV spectra exhibit exceptionally small proximity zones. These quasars are excellent candidates for being gravitationally lensed objects, because the local ionizing flux implied by their small proximity zones is far below the expectation from their observed UV luminosities. We aim to apply a two-fold observing strategy using imaging both in the near-IR to search for multiple quasar images, as well as in the optical regime to target foreground lensing galaxies using the intergalactic medium as a natural long-pass filter to avoid the quasar light, in order to improve the success rate of this lensing search. In case we do not find evidence for lensing, the quasars' small proximity zones could be explained by very short UV-luminous lifetimes of less than 10,000 years, requiring either super-Eddington accretion rates or highly obscured black hole growth phases, in order to explain the concomitant SMBH growth. Thus either outcome of our proposed observations promises new insights into the formation and growth of the first SMBHs.We aim to tagert six quasars at z~6 with ACS/WFC in two different filters, i.e. F892N and F555W. Data taken with the F892N filter will capture the quasarrest-frame UV continuum emission and will search for multiple images of the quasar at small angular separations. Observations with the wide F555W filter will search the foreground of the quasars for potential lensing galaxies along the quasar sightline without any contamination from the quasar itself, since the filter is chosen to be at lower wavelengths than the Lyman-limit.
We aim to observe each quasar for 2 orbits, one orbit for each filter (apart from target 02, i.e. SDSSJ1335+3533, which has already archival HST data with the filter F105W on WFC3-IR, program ID: #12184, resulting in a similar angular resolution). This implies that each visit consists of 1-2 orbits, ensuring easy schedulability of the program. We split each orbit into 4 exposures applying the dither pattern ACS-WFC-DITHER-BOX, which was selected as a minimally compact arrangement that provides half-integer pixel dither steps that will allow for an improved PSF reconstruction in the drizzled stack. The exposure time of ~520s per dither position is chosen to maximize the orbital visibilities used. This will allow us to detect any foreground galaxies down to a magnitude of m_AB~28 mag (~95% completeness) with >4.3 sigma significance. The chosen longer wavelength filter F892N with a central wavelength of lambda = 8915 A will image the rest-frame UV continuum emission of the quasar and enable the detection of multiple quasar images with an diffraction-limited angular resolution of approximately 0.076''.
We chose the aperture WFC1, since it is in the middle of one of the two detectors avoiding potential issues with the detector gap, but nevertheless capturing all potentially lensing foreground galaxies at impact parameters of <100 arcsec from the quasar sightline, which is far more than required.
We have no orientation or timing requirements.The team is lead by PI Eilers, who is an expert in the analysis of high-redshift quasars, their proximity zones and the growth of supermassive black holes in the early universe.
Co-Is Simcoe and Hennawi have extensive expertise with ground- and space-based observations of high-redshift quasars, and co-I Davies has recently published an analysis on gravitational lensing constraints based on the quasars' proximity zones (Davies et al. 2020, ApJL, 904, 32), which builds the theoretical framework for this proposal.
Co-Is Mason and Munoz are experts in gravitational lensing models, whereas co-Is Tacchella and Nelson both have extensive experience with analyzing HST data of high-redshift galaxies and quasars. Co-I Belli is an expert in the analysis of galaxies and their evolution.Supermassive Black Holes and Active Galaxies6falsefalsefalsefalsefalsefalsefalseSUPPORTEDGALAXYQSOQUASARJ2000J2000z_AB = 20.82+-0.07GALAXYQSOQUASARJ2000J2000z_AB = 20.10+-0.11GALAXYQSOQUASARJ2000J2000z_AB = 19.44+-0.08GALAXYQSOQUASARJ2000J2000z_AB = 22.35+-0.09GALAXYQSOQUASARJ2000J2000z_AB = 22.03+-0.05GALAXYQSOQUASARJ2000J2000z_AB = 20.66+-0.02ACS/WFCImagingNoNoF892NACS/WFCImagingNoNoF555WACS/WFCImagingNoNoF555WACS/WFCImagingNoNoF892NACS/WFCImagingNoNoF555WACS/WFCImagingNoNoF892NACS/WFCImagingNoNoF555WACS/WFCImagingNoNoF892NACS/WFCImagingNoNoF555WACS/WFCImagingNoNoF892NACS/WFCImagingNoNoF555WPOS-TARGDITHER0.262LINE0.192falsefalse68.14418.39ACS-WFC-DITHER-BOX1false/System/Volumes/Data/solaris/user1/csoto/OP-cache/16756-v01.xmlThe scheduling data was generated by CASM 29.2.CASM was run in Phase II mode.163705797000096.12203677658613(Tic-Visit
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