15082( 2) - 20-Jul-2017 15:38:26 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 15082 Version: 2 Check-in Time: 20-Jul-2017 15:38:26 STScI Edit Number: 0 Title Monsters on the move: Confirming gravitational wave recoiling supermassive black hole candidates ------------------------------------------------------------------------------------ Type Cycle GO 25 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Andrew Robinson Rochester Institute of Technology Y CoI: Yashashree Shirish Jadhav Rochester Institute of Technology Y CoI: Dr. Davide Lena Space Research Organization Netherlands N ------------------------------------------------------------------------------------ Abstract There is compelling evidence that supermassive black holes (SMBH) reside at the centers of all large galaxies and are the gravitational 'engines' of Active Galactic Nuclei (AGN). Mergers between galaxies are thought to have played a fundamental role in the growth and evolution of the largest galaxies in the nearby universe. Galaxy mergers lead to the formation of an SMBH binary, which eventually coalescences through the emission of gravitational waves and receives a recoil kick (~several 1000km/s). This recoil in turn causes the merged SMBH to oscillate (~1Gyr) in the gravitational potential well of the host galaxy. During this time, the recoiling SMBH may be observed as a 'displaced' AGN. These events are a strong test of gravitational physics and the merger frequency of binary SMBH. Due to the long damping time of the post recoil oscillations, displacements ~10-100pc may be expected even in nearby elliptical galaxies and can be measured as spatial offsets of AGN in high resolution optical or infrared images. In a preliminary study of 96 early type galaxies using archival HST/WFPC2 images we have identified 18 candidates that show a significant displacement between the SMBH (traced by the AGN) and the photocenter of the host galaxy, determined by isophotal analysis. However, it is necessary to confirm these displacements using IR images since diffuse galaxy scale and nuclear dust structures are common. Here we propose to obtain WFC3/IR F110W and F160W images of 6 of the 18 candidates for which no IR images are available in the HST archive. These observations will allow us to both confirm and improve the accuracy of the measured displacements. ------------------------------------------------------------------------------------ Observations Description ------------------------ We propose to obtain WFC3/IR F110W and F160W images of 5 nearby elliptical galaxies known to host AGN. We have previously identified these galaxies as hosting candidate gravitationally recoiling supermassive black holes, based on measurements of significant spatial displacements between the galaxy photocenter and the position of the AGN in archival HST images (typically WFPC2 images). However, as diffuse galaxy scale and nuclear dust structures can produce spurious displacements, we will repeat the analysis (as described below) with the new WFC3/IR F110W and F160W images in order to confirm that comparable displacements are also present at these longer wavelengths. Isophotal analysis of WFC3/IR images that are available in the archive for other candidate galaxies indicates that we require a SNR ~ 5-10 for accurate 15082( 2) - 20-Jul-2017 15:38:26 - [ 2] fitting of the outermost isophotes considered in the analysis. We will require one orbit for each object to obtain an exposure in each of the two filters. We will use a standard 2-point dither pattern to improve spatial sampling and mitigate the effects of hot pixels, cosmetic defects and cosmic rays. Using available HST images of our 5 target galaxies, we have used the HST WCS ETC with an elliptical galaxy spectrum to estimate the exposure times required to reach an SNR of at least 5 in the filters WFC3/IR F110W and F160W for the outermost isophotes, that is, the faintest included in our photometric modelling of the existing optical images (WFPC2 or ACS). At larger distances from the galaxy center the surface brightness is either too low for reliable isophote fitting and/or becomes significantly irregular. For our 5 objects the outer isophotes have radii of 6.75 to 20 arcsecs from the center of the galaxy. The typical surface brightness at these distances ranges from 3.84E-18 erg cm-2 s-1 A-1 arcsec-2 (at 5439 A) to 2.68E-19 erg cm-2 s-1 A-1 arcsec-2 (at 6919 A). We have also used the WFC3 ETC to make sure that the exposure times are well within the saturation limits for the center of the galaxy. The typical central flux of the galaxies ranges between 2.60E-16 erg cm-2 s-1 A-1 arcsec-2 (at 9054.8 A) and 1.27E-17 erg cm-2 s-1 A-1 arcsec-2 (at 6919 A). For NGC 3998, NGC5419 and NGC5920 we use one exposure in each filter to obtain an SNR of ~5 for NGC5920, ~13 for NGC3998 and ~57 for NGC5419 in the outer isophotes, without reaching saturation in the center. Since M89 and NGC4473 are relatively bright sources, similar exposures would result in saturation at the center of the galaxy as the exposure ramps up. Therefore, to avoid persistence effects we will use 2 iterations of shorter exposures in each filter to obtain an SNR of ~24 for M89 and SNR of ~26 for NGC4473. For optimal utilization of each orbit, we have used SPARS100 and NSAMP = 9 (for F160W) and NSAMP = 6 (for F110W) for NGC5419 and NGC5920. We use SPARS50 and NSAMP = 9 for F160W, and SPARS25 and NSAMP = 10 for F110W for each of the 2 iterations for both M89 and NGC4473. We use SPARS100 and NSAMP = 10 (for F160W), and SPARS50 and NSAMP = 12 (for F110W) for NGC3998. These images will allow us to conduct isophotal analysis to confirm the photocenter-AGN displacements measured in the initial study. Measurements from both WFC3/IR images will be combined to obtain a robust weighted average displacement. The analysis methodology has been developed and tested during the preliminary study. Each galaxy was modelled by fitting elliptical isophotes to the HST image, outside the break radius at which the surface brightness profile flattens off. Within this core the ellipse fits are likely to be distorted by the nuclear PSF and possibly by intrinsic asymmetries. The global photocenter position is then computed as the mean value of the ellipse centers, weighted by the surface brightness. The position of the AGN was obtained by fitting the nuclear point source after applying an unsharp mask to the same image. The two positions are then compared to determine a displacement vector for spatial offsets. The interpercentile range of the distribution of individual isophote centers gives a conservative estimate of the uncertainty of the photocenter 15082( 2) - 20-Jul-2017 15:38:26 - [ 3] position. This method shall be applied for the obtained WFC3 images to confirm and study the displacements between the photocenter and the AGN. ------------------------------------------------------------------------------------ 15082( 2) - 20-Jul-2017 15:38:26 - [ 4] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 M-89 GALAXY, ELLIPTICAL RA=12H35M39.8000S, J2000 V = 9.75 DEC=+12D33'23.00" Reference Frame: Other: SIMBAD Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC-5419 GALAXY, ELLIPTICAL RA=14H03M38.7710S, J2000 V = 11.33 DEC=-33D58'42.20" Reference Frame: Other: SIMBAD Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. ------------------------------------------------------------------------------------------------------------------------------------ 3 NGC-5920 GALAXY, ELLIPTICAL RA=15H21M51.8700S, J2000 V = 14.7 DEC=+07D42'31.97" Reference Frame: Other: SIMBAD Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. ------------------------------------------------------------------------------------------------------------------------------------ 4 NGC-4473 GALAXY, ELLIPTICAL RA=12H29M48.8780S, J2000 V = 10.2 DEC=+13D25'45.55" Reference Frame: Other: SIMBAD Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. ------------------------------------------------------------------------------------------------------------------------------------ 5 NGC-3998 GALAXY, ELLIPTICAL RA=11H57M56.1333S, J2000 V = 12.1 DEC=+55D27'12.92" Reference Frame: Other: SIMBAD Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. ------------------------------------------------------------------------------------------------------------------------------------ 15082( 2) - 20-Jul-2017 15:38:26 - [ 5] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-IR-DITHER-LINE Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 0.636 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 41.788 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 15082( 2) - 20-Jul-2017 15:38:26 - [ 6] Visit: 01 (M-89) 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 M-89 WFC3/IR MULTIAC IR F160W SAMP-SEQ=SPARS50, NSAMP=9 2 DEF PATTERN 1 1-2 CUM (1611.744 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 M-89 WFC3/IR MULTIAC IR F110W SAMP-SEQ=SPARS25, NSAMP=10 2 DEF CUM (911.748 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 | ------------------------------------------------------------------------------------------------------------------------------------ M-89 1 WFC3/IR MULTIAC IR F160W 1 none 1 none 1 N/A CUM M-89 1 WFC3/IR MULTIAC IR F160W 1 none 2 none 1 N/A CUM M-89 1 WFC3/IR MULTIAC IR F160W 2 none 1 none 1 N/A CUM M-89 1 WFC3/IR MULTIAC IR F160W 2 none 2 none 1 N/A CUM M-89 2 WFC3/IR MULTIAC IR F110W 1 none 1 none 1 N/A CUM M-89 2 WFC3/IR MULTIAC IR F110W 1 none 2 none 1 N/A CUM M-89 2 WFC3/IR MULTIAC IR F110W 2 none 1 none 1 N/A CUM M-89 2 WFC3/IR MULTIAC IR F110W 2 none 2 none 1 N/A CUM 15082( 2) - 20-Jul-2017 15:38:26 - [ 7] Visit: 02 (NGC-3998) 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 NGC-3998 WFC3/IR MULTIAC IR F160W SAMP-SEQ=SPARS100, NSAMP=10 1 DEF PATTERN 1 1-2 CUM (1805.87 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC-3998 WFC3/IR MULTIAC IR F110W SAMP-SEQ=SPARS50, NSAMP=12 1 DEF CUM (1105.875 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-3998 1 WFC3/IR MULTIAC IR F160W 1 none none none 1 N/A CUM NGC-3998 1 WFC3/IR MULTIAC IR F160W 2 none none none 1 N/A CUM NGC-3998 2 WFC3/IR MULTIAC IR F110W 1 none none none 1 N/A CUM NGC-3998 2 WFC3/IR MULTIAC IR F110W 2 none none none 1 N/A CUM 15082( 2) - 20-Jul-2017 15:38:26 - [ 8] Visit: 03 (NGC-5419) 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 NGC-5419 WFC3/IR MULTIAC IR F160W SAMP-SEQ=SPARS100, NSAMP=9 1 DEF PATTERN 1 1-2 CUM (1605.87 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC-5419 WFC3/IR MULTIAC IR F110W SAMP-SEQ=SPARS100, NSAMP=6 1 DEF CUM (1005.868 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-5419 1 WFC3/IR MULTIAC IR F160W 1 none none none 1 N/A CUM NGC-5419 1 WFC3/IR MULTIAC IR F160W 2 none none none 1 N/A CUM NGC-5419 2 WFC3/IR MULTIAC IR F110W 1 none none none 1 N/A CUM NGC-5419 2 WFC3/IR MULTIAC IR F110W 2 none none none 1 N/A CUM 15082( 2) - 20-Jul-2017 15:38:26 - [ 9] Visit: 04 (NGC-5920) 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 NGC-5920 WFC3/IR MULTIAC IR F160W SAMP-SEQ=SPARS100, NSAMP=9 1 DEF PATTERN 1 1-2 CUM (1605.87 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC-5920 WFC3/IR MULTIAC IR F110W SAMP-SEQ=SPARS100, NSAMP=6 1 DEF CUM (1005.868 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-5920 1 WFC3/IR MULTIAC IR F160W 1 none none none 1 N/A CUM NGC-5920 1 WFC3/IR MULTIAC IR F160W 2 none none none 1 N/A CUM NGC-5920 2 WFC3/IR MULTIAC IR F110W 1 none none none 1 N/A CUM NGC-5920 2 WFC3/IR MULTIAC IR F110W 2 none none none 1 N/A CUM 15082( 2) - 20-Jul-2017 15:38:26 - [ 10] Visit: 05 (NGC-4473) 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 NGC-4473 WFC3/IR MULTIAC IR F160W SAMP-SEQ=SPARS50, NSAMP=9 2 DEF PATTERN 1 1-2 CUM (1611.744 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC-4473 WFC3/IR MULTIAC IR F110W SAMP-SEQ=SPARS25, NSAMP=10 2 DEF CUM (911.748 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC-4473 1 WFC3/IR MULTIAC IR F160W 1 none 1 none 1 N/A CUM NGC-4473 1 WFC3/IR MULTIAC IR F160W 1 none 2 none 1 N/A CUM NGC-4473 1 WFC3/IR MULTIAC IR F160W 2 none 1 none 1 N/A CUM NGC-4473 1 WFC3/IR MULTIAC IR F160W 2 none 2 none 1 N/A CUM NGC-4473 2 WFC3/IR MULTIAC IR F110W 1 none 1 none 1 N/A CUM NGC-4473 2 WFC3/IR MULTIAC IR F110W 1 none 2 none 1 N/A CUM NGC-4473 2 WFC3/IR MULTIAC IR F110W 2 none 1 none 1 N/A CUM NGC-4473 2 WFC3/IR MULTIAC IR F110W 2 none 2 none 1 N/A CUM 15082( 2) - 20-Jul-2017 15:38:26 - [ 11] Summary Form for Proposal 15082 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures IR ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/IR ------------------------------------------------------------------------------------------------------------------------------------ Opmodes MULTIACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters NSAMP=10, NSAMP=12, NSAMP=6, NSAMP=9, SAMP-SEQ=SPARS100, SAMP-SEQ=SPARS25, SAMP-SEQ=SPARS50 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 1 1-2 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F110W, F160W ------------------------------------------------------------------------------------------------------------------------------------ Target Names M-89, NGC-3998, NGC-4473, NGC-5419, NGC-5920 ------------------------------------------------------------------------------------------------------------------------------------