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The total number of Primary Orbits used in all Cycles must equal the total number of Primary Orbits specified on all the Observations. (Compare totals reported on the first and second pages of the PDF Preview.)0Assigned ID: 1309
----- Attempting Submission 1 (Tue Dec 29 14:42:26 GMT 2020) -----joint0----- Attempting Submission 1 (Fri Jan 29 12:28:03 GMT 2021) -----A Hunt for Binary Supermassive Black Holes with the VLBA and HSTWe propose 162.2 hours (including overheads) of Q-band observations with the VLBA in order to explore the underlying nature of eight peculiar active galactic nuclei (AGN). These eight objects originate from a sample of 88 SDSS quasars identified as having broad emission lines that are velocity-offset (>1000~km/s) from the host galaxy (Eracleous et al., 2012), potentially indicating a binary supermassive black hole (SMBH). However, there are two other leading models for such shifts: a recoiling post-merger SMBH, or a broad line region (BLR) gas outflow caused by a jet or accretion disk wind. We have previously followed up all 88 objects from Eracleous et al. (2012) with VLA X-band observations. We then followed up the brightest VLA-detected objects with VLBA X-band observations. Our proposed Q-band observations of the eight brightest objects will provide a critical 5-fold increase in angular resolution over the previous VLBA X-band observations, and test the binary hypothesis down to sub-pc separations in all cases. In addition, we request 9 orbits with the HST in order to determine the SMBH masses, assess the host galaxies for any evidence of recent major galaxy mergers, and measure the photometric centers that will allow more precise determination of radio/optical offsets.The overall scientific goals of this proposal are two-fold: image the faint morphological structures of the quasar host galaxies for any indications of a recent merger (such as tidal tails); and photometricly model the bulge of the host galaxy in order to precisely determine its light center, along with measuring the bulge luminosity for determining a black hole mass. The precise measuement of the bulge's photocenter is necessary for comparison with the VLBI radio core position to determine if there are any offset AGN which may be indicative of a recoiling black hole. Given these requirements, we need a good description of the PSF in the F125W filter, for the optical quasar subtraction and photometric analysis of the host. Hence, we are observing the white dwarf star to get a picture of the PSF with same instrument configuration, and we are using a 4-point (box) dithering pattern to better sample the PSF. Since the expected host galaxies are faint, we chose the WFC3 IR camera in order to readout exposures in a STEP sequence (recommended for high dynamic range imaging), alllowing us to build up sensitivity to low surface brightness features. Our estimated necessary exposure times are all within the time allowed during a single orbit. However, since our stratgey is to observe one target per orbit, we intend to use all of the possible time during the orbit towards the target exposure to maximize our sensitivity. To this end, we adjust the number of readout samples to be within the constraints allowed for a single orbit.n/a6falsefalsefalsefalsefalsefalsefalseSUPPORTEDGALAXYQUASARThis object was generated by the targetselector and retrieved from the SIMBAD database.2MASS-J09503674+5128382J2000B=18.74GALAXYQUASARYESThis object was generated by the targetselector and retrieved from the SIMBAD database.7C-101803.39+453837.00J2000B=18.34GALAXYQUASARYESThis object was generated by the targetselector and retrieved from the SIMBAD database.2MASSI-J1052031+240505J2000B=18.5GALAXYQUASARYESThis object was generated by the targetselector and retrieved from the SIMBAD database.7C-151247.00+370154.00J2000B=16.79CALIBRATIONPOINT SPREAD FUNCTIONNOThis object was generated by the targetselector and retrieved from the SIMBAD database.GRW+70D5824J2000WFC3/IRImagingNoNoF125WWFC3/IRImagingNoNoF125WWFC3/IRImagingNoNoF125WWFC3/IRImagingNoNoF125WPOS-TARGDITHER0.572LINE0.365falsefalse74.653418.528WFC3-IR-DITHER-BOX-MIN1falseThe scheduling data was generated by CASM 29.0.CASM was run in Phase II mode.1618583937000141.41074324235137(Tic-Visit
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