0Assigned ID: 438
----- Attempting Submission 1 (Fri Apr 10 12:04:42 GMT 2015) -----0----- Attempting Submission 1 (Thu Jul 23 21:47:36 GMT 2015) -----
----- Attempting Submission 2 (Fri Jul 24 18:33:11 GMT 2015) -----
----- Attempting Submission 4 (Tue Mar 22 16:44:14 GMT 2016) -----
HST Phase II Proposal 14165 (14165.apt) successfully submitted.
Receipt: # 14165-4
----- Attempting Submission 5 (Tue Mar 22 21:53:09 GMT 2016) -----
----- Attempting Submission 6 (Wed Apr 27 18:15:58 GMT 2016) -----Revealing the largest gravitational lens PLCK G287.0+32.9We propose to investigate the peculiar and extremely large gravitational lens PLCK G287.0+32.9, discovered as one of the most massive objects in SZ measurements by Planck. Our follow-up of the cluster with optical WFI ground based imaging shows evident strong lensing features in the cluster core. The outer arcs, confirmed at z=1.167 from our recent VIMOS observations, is at a distanceof ~85" from the brightest and centrally located galaxy of the cluster, which makes PLCK G287.0+32.9 a candidate for the largest strong lens in the sky. If confirmed, this would significantly add to the tension of observed Einstein radii with predictions from Lambda-CDM. To this end, we require high resolution spatial imaging of the cluster to verify its large lensing features and further investigate its properties. Our goal is to use the HST photometry with our recent VLT/VIMOS spectroscopic datasets to perform a robust and detailed strong lensing analysis of this cluster. We aim to trace the total mass distribution of PLCK G287.0+32.9 by combining the strong lensing features with our WFI weak lensing analysis.According to our science project, we require observations of the core of the galaxy cluster PLCKG287.0+32.9 in 3 ACS/WFC filters (F475W,F606W and F814W) and 1 WFC3/IR filter (F110W). The rationale for using these filters is as follows. In order to detect arcs and their faint counter images we need filters with high throughput. Lensing is achromatic, which is why measuring at least one colour with good signal-to-noise ratio is essential for multiple images confirmation. Finally we want to be sensitive to lensed galaxies with various SED properties in a large redshift range. Having F110W band as the reddest filter, in addition allows us to detect F814W dropouts, which are candidate for magnified galaxies at redshift z > 7.
The ACS/WFC filters F475W and F606W will be essential to photometrically select cluster members which we need to include in the strong lensing model to accurately trace the total mass distribution of the galaxy cluster. These two filters will be used to select candidate cluster members from the cluster red sequence, in combination with information from the sample of spectroscopically confirmed members from the VLT/VIMOS program. In addition, for the lens modelling of the galaxies in the cluster we need to relate the luminosity to the depth of their potential (using the Faber-Jackson and Fundamental Plane relations, see e.g. Faber et al. 1976, 1987, Bender et al. 1992). According to our previous experience, the F814W and F110W filters provide the smaller scatter estimate for the halo potential depth (i.e. velocity dispersion). Taking together, our set of 4 filters covers the entire wavelength range from 3800 to 14000 A. This will allow us to identify optical dropout candidates at z = [4:8; 6:8] robustly. If a multiply imaged galaxy is found only in the F110W filter, it could have a redshift up to 10. This could then be confirmed through the strong lensing model, following the procedure in Zitrin et al. (2014).
In addition to allowing for the identification of multiply imaged objects and high redshift galaxies, the chosen filter set will help us to characterize the cluster galaxy population. For example, the F475W filter allows us to investigate whether galaxies which have elliptical morphology have undergone recent star formation triggered by the ongoing merger of the galaxy cluster.
Exposure time estimations: Concerning the depths of the observations, the dithered pattern and cosmic rays split, we will follow our successful strategy from CLASH. Thus we require the following exposure time per filter:
F475W 4x500s = 2000s (1700-2200s) "1 orbit"
F606W 4x500s = 2000s (1700-2200s) "1 orbit"
F814W 8x500s = 4000s (3900-4200s) "2 orbits"
F110W 10x500s = 5000s (4900-5100s) "2 orbits".
These exposures will give us the following depths (5 magnitude limits for a point source):
F475W: 27.5 mag
F606W: 27.6 mag
F814W: 27.0 mag
F110W: 28.2 mag
For the mean cluster redshift in CLASH (zcl ~ 0:4) such a depth allowed for a robust identification of 10 to 20 multiply imaged systems over a broad redshift range per cluster, which is needed for a precise strong lensing model. We have already identified several strong lensing features spread over 160" in diameter. We can cover them with one pointing for the case of ACS/WFC, but need two pointings with the WFC3/IR. We have outlined roughly our pointing strategy in Fig. 3. By allowing the overlap of the WFC3/IR pointings in the central region of the cluster we will get even deeper there. This will help us to find central images for high-z lensed systems. Such a detection would make the case for high redshift galaxies even stronger, see Monna et al. (2014). The brightest star in the proposed pointings is comparable to the bright star in the core of the CLASH cluster MACS 0416, and still fainter than the brightest stars in the COSMOS field. Hence, it will not cause technical problems in the observations.COSMOLOGY12falsefalsefalsefalsefalsefalseSUPPORTEDCLUSTER OF GALAXIESGRAVITATIONAL LENSJ2000J2000CLUSTER OF GALAXIESGRAVITATIONAL LENSJ2000J2000CLUSTER OF GALAXIESGRAVITATIONAL LENSJ2000J2000ACS/WFCImagingNoNoF475WACS/WFCImagingNoNoF606WACS/WFCImagingNoNoF814WWFC3/IRImagingNoNoF110WPOS-TARGDITHER3.06806LINE6.06746falsefalse174.21599485.38230ACS-WFC-DITHER-BOX1falsePOS-TARGDITHER5.183LINE0.365falsefalse74.653418.528WFC3-IR-DITHER-BOX-MIN2falseThe scheduling data was generated by CASM 24.0.CASM was run in Phase II mode./private/var/folders/p0/5z19pd1n5_xgqqggpdkq_14w0005_3/T/OPVisit1913512041854099449.xml(Tic-Visit
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