We propose HST/WFC3 near-IR high-resolution imaging of five gravitational lens candidates produced by the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS). These sources are among the brightest sub-mm objects detected in H-ATLAS. Their spectral energy distribution, sub-mm colors and optical IDs are consistent with a gravitational lensing system where a low redshift (z<0.8) elliptical galaxy is acting as a lens on a dust-obscured high-redshift (z>1.5) galaxy. However, the background galaxy is predicted to be too faint in the optical/near-IR to be detectable in the ancillary SDSS and UKIDSS images, therefore our proposal for deep near-IR imaging with HST/WFC3. The discovery of gravitational lenses is one of the scientific goals of H-ATLAS and, if achieved, it will demonstrate the efficiency of blank wide-area sub-mm survey in producing unbiased and complete samples of gravitational lensing systems. Thanks to its sensitivity and unique spatial resolution HST/WFC3 will allow us to constrain the morphology of the brightest sub-mm sources detected by Herschel and therefore to eventually confirm their nature as gravitational lenses. In that case we will use HST/WFC3 images to reconstruct the intrinsic morphology of the background source and constrain the mass and matter profile of the lens.

The background source in each of these 5 lens systems is heavily obscured by dust. Therefore we propose near-IR WFC3/HST observations using the two broad filters F110W and the F160W. The combined observations at two different wavelengths will provide the color information needed to disentangle the lens from the background source, the former having a bluer spectrum than the latter. In particular we will use the F110W image to accurately fit the light profile of the lens and exploit the F160W image for the detection of the background source after performing the lens subtraction. We have used the on-line calculator to estimate the exposure time necessary to detect the background source with a signal-to-noise ratio (SNR) >8 in the WFC3/F160W image, after the lens subtraction. We have made the assumption that the background source is lensed into an Einstein ring (the worst case scenario) so the total flux is distributed over the largest area. The Einstein radius (theta_E) is estimated from the line-of-sight stellar velocity dispersion of the lensing galay as inferred from the Faber-Jackson relation between the velocity dispersion and the rest-frame B-band luminosity for elliptical galaxies. The latter is derived from the fit to the available UV/optical/near-IR data (i.e. from GALEX, SDSS and UKIDSS). We assume for the Einstein ring a thickness of 0.2 arcseconds. There is an important issue related to the contamination from the lens that acts as an extra source of background noise. In order to account for this effect we have fitted the light profile of the lens with GALFIT (assuming either a Sersic profile or a Sersic+exponential disc profile) and estimated its brightness at a distance equal to theta_E from the center of the lens. In practice this contamination can be significantly reduced by subtracting the GALFIT model for the lens from the F160W image (after re-scaling the profile of the lens to the value of the peak measured in the F160W image). We expect the residual contribution of the lens, after the subtraction of the best-fit GALFIT model, to be of the order of 1 per cent. Therefore we have calculated the exposure time using the value of the brightness of the lens at a distance theta_E from its center and rescaled by a factor of 0.01. We have checked that for the derived integration times for observations with the F160W filter the flux contributed by the lens is not going to saturate the CCD. In order to estimate the exposure time for observations with F110W we required the lens to be detected with a signal-to-noise ratio of at least several hundreds. This will allow us to accurately fit the light profile of the lens and efficiently subtract it from the F160W image. In all the exposure time calculations, the fluxes of the lensing galaxy and of the background source in the F110W and F160W filters have been estimated from the SED models of da Chuna et al. (2008, 2010) which best-fit the available UV/optical/near-IR photometric data. 2 HST orbits are used for each object. One orbit is entirely dedicated to the imaging in the F160W filter (with a 4-dither patter to sample the PSF) to obtain the highest detection for the background source, typically with a signal-to-noise ratio >5 after the lens is subtracted off. The other orbit is split into 2 sets of exposures: one set in the F110W filter (with a 4-dither patter to sample the PSF) is meant to allow the detection of the lensing galaxy with a signal-to-noise ratio >400; a second set in the F160W filter (with a 2-dither pattern) is meant instead to improve the detection of the background source once the data are combined with those collected in the other orbit. COSMOLOGY 12 false 0.0 0.0 false false false false false false SUPPORTED GALAXY ELLIPTICAL GRAVITATIONAL LENS HIGH REDSHIFT GALAXY ULTRALUMINOUS IR GAL Gravitational lensing system. Redshift of the lensing galaxy: z=0.2999±0.0002 Redshift of the background source: z=3.042±0.001 Estimated Einstein radius: theta_E=1.62 arcsec The fluxes quoted above are for the lensing galaxy. The lensing galaxy extends over an area of 3.05 square arcseconds, and its light profile has FWHM=1.23 arcsec F(10200) = 9.3+/-1.4 E-17, F(12200) = 8.5+/-1.3 E-17, F(16300) = 5.5+/-0.8 E-17, F(21900) = 3.9+/-0.6 E-17, SIZE=1.23+/-0.18 HATLAS-J090311.6+003906 J2000 09 03 11.6090 +00 39 6.73 J2000 GALAXY ELLIPTICAL GRAVITATIONAL LENS HIGH REDSHIFT GALAXY ULTRALUMINOUS IR GAL Gravitational lensing system. Redshift of the lensing galaxy: z=0.2201±0.002 Redshift of the background source: z=2.6260±0.0003 Estimated Einstein radius: theta_E=0.59 arcsec The fluxes quoted above are for the lensing galaxy. The lensing galaxy extends over an area of 3.02 square arcseconds, and its light profile has FWHM=1.17 arcsec F(10200) = 5.4+/-0.8 E-17, F(12200) = 5.4+/-0.8 E-17, F(16300) = 3.8+/-0.6 E-17, F(21900) = 2.5+/-0.4 E-17, SIZE=1.17+/-0.59 HATLAS-J091305.0-005343 J2000 09 13 4.9510 -00 53 43.75 J2000 GALAXY ELLIPTICAL GRAVITATIONAL LENS HIGH REDSHIFT GALAXY ULTRALUMINOUS IR GAL Gravitational lensing system. Redshift of the lensing galaxy: z=0.679±0.057 Redshift of the background source: z=1.577±0.008 Estimated Einstein radius: theta_E=0.67 arcsec The fluxes quoted above are for the lensing galaxy. The lensing galaxy extends over an area of 2.50 square arcseconds, and its light profile has FWHM=1.16 arcsec F(10200) = 9.5+/-1.4 E-18, F(12200) = 8.3+/-1.2 E-18, F(16300) = 8.5+/-1.3 E-18, F(21900) = 6.7+/-1.0 E-18, SIZE=1.16+/-0.17 HATLAS-J090740.0-004200 J2000 09 07 40.0000 -00 42 0.18 J2000 GALAXY ELLIPTICAL GRAVITATIONAL LENS HIGH REDSHIFT GALAXY ULTRALUMINOUS IR GAL Gravitational lensing system. Redshift of the lensing galaxy: z=0.7932±0.0012 Redshift of the background source: z=1.786±0.005 Estimated Einstein radius: theta_E=0.75 arcsec The fluxes quoted above are for the lensing galaxy. The lensing galaxy extends over an area of 3.55 square arcseconds, and its light profile has FWHM=1.41 arcsec F(10200) = 1.3+/-0.2 E-17, F(12200) = 1.3+/-0.2 E-17, F(16300) = 1.2+/-0.2 E-17, F(21900) = 1.1+/-0.2 E-17, SIZE=1.41+/-0.21 HATLAS-J091043.1-000321 J2000 09 10 43.0900 -00 03 21.88 J2000 GALAXY ELLIPTICAL GRAVITATIONAL LENS HIGH REDSHIFT GALAXY ULTRALUMINOUS IR GAL Gravitational lensing system. Redshift of the lensing galaxy: z=0.77±0.13 Redshift of the background source: z=2.308±0.011 Assumedd Einstein radius: theta_E=0.70 arcsec The fluxes quoted above are for the lensing galaxy. The lensing galaxy extends over an area of 7.20 square arcseconds, and its light profile has FWHM=2.48 arcsec F(10200) = 1.0+/-0.2 E-17, F(12200) = 8.9+/-1.3 E-18, F(16300) = 8.0+/-1.2 E-18, F(21900) = 6.9+/-1.0 E-18, SIZE=2.48+/-0.37 HATLAS-J090302.9-014127 J2000 09 03 2.9000 -01 41 27.57 J2000 WFC3/IR Imaging No No F110W WFC3/IR Imaging No No F160W WFC3/IR Imaging No No F110W WFC3/IR Imaging No No F160W WFC3/IR Imaging No No F110W WFC3/IR Imaging No No F160W WFC3/IR Imaging No No F110W WFC3/IR Imaging No No F160W WFC3/IR Imaging No No F110W WFC3/IR Imaging No No F160W POS-TARG DITHER 0.572 LINE 0.365 false false 74.653 4 18.528 WFC3-IR-DITHER-BOX-MIN 1 false POS-TARG DITHER 0.636 LINE false false 2 41.788 WFC3-IR-DITHER-LINE 2 false The scheduling data was generated by CASM 18.3.1. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12194 :visit-id "01" :proposal-version -1 :trans-version "20100505" :date "09-Jul-2010 13:24:36.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "30" :si-bright-earth-limb-angle 20.0 :data-volume 2054256 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12194 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12194 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2870 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3234 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12194 :visit-id "01" :orbit-number 2 :pcs-time 222 :si-vis-utilization 2840 :al-overhead-at-end 0 :internal-dur-at-end 502 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3234 :pcs-gap 0 ) true 2 0 4-dither pattern. total time = 177.936x4 sec (for 1024x1024 image size) This gives SNR = 1,176.97 (4 frames) and a Time to Saturation (for a single exposure) = 2,225.53 seconds (Exposure ID: WFC3.A329203) Input values for ETC: Diameter of the source = 1.97 arcsec (this is the diameter of a circle that has the same area of the source light profile) Radius of the extraction region = 0.615 arcsec (this is equal to half of the FWHM of the source light profile) 2-dither pattern. total time = 902.935x2 sec (for 1024x1024 image size) This gives SNR = 57.23 (2 frames), corresponding to an effective SNR = 8.0 and a Time to Saturation (for a single exposure) = 66,251.33 seconds (Exposure ID: WFC3.A329218) Time to Saturation for the lens (for a single exposure) = 3892 seconds Input values for ETC: Diameter of the source = 1.62 arcsec (this is the diameter of a circle that has the same area of the assumed Einstein ring) Radius of the extraction region = 0.81 arcsec (this is equal to half of the diameter of the source) The effective signal-to-noise ratio, SNR_eff, is estimated as SNR_eff = 1/(1/SNR_etc + B_L*0.01/B_S) where - SNR_etc is the signal-to-noise ratio returned by the exposure time calculator for the input exposure time; - B_L is the surface brightness of the lensing galaxy at a distance theta_E (i.e. the Einstein radius) from its center; - B_S is the surface density of the background source (assumed to be lensed into an Einstein ring). The adopted values for B_L and B_S are: B_L = 13.7 microJy per square arcseconds B_S = 1.28 microJy per square arcseconds 4-dither pattern. total time = 652.938x4 sec (for 1024x1024 image size) This gives SNR = 66.53 (4 frames), corresponding to an effective SNR = 8.2 and a Time to Saturation (for a single exposure) = 66,251.33 seconds (Exposure ID: WFC3.A329227) Time to Saturation for the lens (for a single exposure) = 3892 seconds Input values for ETC: Diameter of the source = 1.62 arcsec (this is the diameter of a circle that has the same area of the assumed Einstein ring) Radius of the extraction region = 0.81 arcsec (this is equal to half of the diameter of the source) The effective signal-to-noise ratio, SNR_eff, is estimated as SNR_eff = 1/(1/SNR_etc + B_L*0.01/B_S) where - SNR_etc is the signal-to-noise ratio returned by the exposure time calculator for the input exposure time; - B_L is the surface brightness of the lensing galaxy at a distance theta_E (i.e. the Einstein radius) from its center; - B_S is the surface density of the background source (assumed to be lensed into an Einstein ring). The adopted values for B_L and B_S are: B_L = 13.7 microJy per square arcseconds B_S = 1.28 microJy per square arcseconds The scheduling data was generated by CASM 18.3.1. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12194 :visit-id "02" :proposal-version -1 :trans-version "20100505" :date "09-Jul-2010 13:24:40.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "30" :si-bright-earth-limb-angle 20.0 :data-volume 2054256 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12194 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12194 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2870 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3234 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12194 :visit-id "02" :orbit-number 2 :pcs-time 222 :si-vis-utilization 2840 :al-overhead-at-end 0 :internal-dur-at-end 502 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3234 :pcs-gap 0 ) true 2 0 4-dither pattern. total time = 177.936x4 sec (for 1024x1024 image size) This gives SNR = 875.49 (4 frames) and a Time to Saturation (for a single exposure) = 3,357.51 seconds (Exposure ID: WFC3.A329241) Input values for ETC: Diameter of the source = 1.96 arcsec (this is the diameter of a circle that has the same area of the source light profile) Radius of the extraction region = 0.585 arcsec (this is equal to half of the FWHM of the source light profile) 2-dither pattern. total time = 902.935x2 sec (for 1024x1024 image size) This gives SNR = 522.96 (2 frames), corresponding to an effective SNR = 64.6 and a Time to Saturation (for a single exposure) = 13,412.60 seconds (Exposure ID: WFC3.A329248) Time to Saturation for the lens (for a single exposure) = 5430 seconds Input values for ETC: Diameter of the source = 0.97 arcsec (this is the diameter of a circle that has the same area of the assumed Einstein ring) Radius of the extraction region = 0.49 arcsec (this is equal to half of the diameter of the source) The effective signal-to-noise ratio, SNR_eff, is estimated as SNR_eff = 1/(1/SNR_etc + B_L*0.01/B_S) where - SNR_etc is the signal-to-noise ratio returned by the exposure time calculator for the input exposure time; - B_L is the surface brightness of the lensing galaxy at a distance theta_E (i.e. the Einstein radius) from its center; - B_S is the surface density of the background source (assumed to be lensed into an Einstein ring). The adopted values for B_L and B_S are: B_L = 53.2 microJy per square arcseconds B_S = 39.2 microJy per square arcseconds 4-dither pattern. total time = 652.938x4 sec (for 1024x1024 image size) This gives SNR = 623.67 (4 frames), corresponding to an effective SNR = 65.9 and a Time to Saturation (for a single exposure) = 13,412.60 seconds (Exposure ID: WFC3.A329252) Time to Saturation for the lens (for a single exposure) = 5430 seconds Input values for ETC: Diameter of the source = 0.97 arcsec (this is the diameter of a circle that has the same area of the assumed Einstein ring) Radius of the extraction region = 0.49 arcsec (this is equal to half of the diameter of the source) The effective signal-to-noise ratio, SNR_eff, is estimated as SNR_eff = 1/(1/SNR_etc + B_L*0.01/B_S) where - SNR_etc is the signal-to-noise ratio returned by the exposure time calculator for the input exposure time; - B_L is the surface brightness of the lensing galaxy at a distance theta_E (i.e. the Einstein radius) from its center; - B_S is the surface density of the background source (assumed to be lensed into an Einstein ring). The adopted values for B_L and B_S are: B_L = 53.2 microJy per square arcseconds B_S = 39.2 microJy per square arcseconds The scheduling data was generated by CASM 18.3.1. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12194 :visit-id "03" :proposal-version -1 :trans-version "20100505" :date "09-Jul-2010 13:24:44.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "30" :si-bright-earth-limb-angle 20.0 :data-volume 2123888 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12194 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12194 :visit-id "03" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2870 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3234 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12194 :visit-id "03" :orbit-number 2 :pcs-time 222 :si-vis-utilization 2840 :al-overhead-at-end 0 :internal-dur-at-end 331 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3234 :pcs-gap 0 ) true 2 0 4-dither pattern. total time = 352.935x4 sec (for 1024x1024 image size) This gives SNR = 456.92 (4 frames) and a Time to Saturation (for a single exposure) = 12,620.38 seconds (Exposure ID: WFC3.A329260) Input values for ETC: Diameter of the source = 1.79 arcsec (this is the diameter of a circle that has the same area of the source light profile) Radius of the extraction region = 0.58 arcsec (this is equal to half of the FWHM of the source light profile) 2-dither pattern. total time = 552.937x2 sec (for 1024x1024 image size) This gives SNR = 40.38 (2 frames), corresponding to an effective SNR = 13.0 and a Time to Saturation (for a single exposure) = 61,848.38 seconds (Exposure ID: WFC3.A329262) Time to Saturation for the lens (for a single exposure) = 18,804 seconds Input values for ETC: Diameter of the source = 1.03 arcsec (this is the diameter of a circle that has the same area of the assumed Einstein ring) Radius of the extraction region = 0.52 arcsec (this is equal to half of the diameter of the source) The effective signal-to-noise ratio, SNR_eff, is estimated as SNR_eff = 1/(1/SNR_etc + B_L*0.01/B_S) where - SNR_etc is the signal-to-noise ratio returned by the exposure time calculator for the input exposure time; - B_L is the surface brightness of the lensing galaxy at a distance theta_E (i.e. the Einstein radius) from its center; - B_S is the surface density of the background source (assumed to be lensed into an Einstein ring). The adopted values for B_L and B_S are: B_L = 10.1 microJy per square arcseconds B_S = 1.93 microJy per square arcseconds 4-dither pattern. total time = 652.938x4 sec (for 1024x1024 image size) This gives SNR = 63.31 (4 frames), corresponding to an effective SNR = 14.7 and a Time to Saturation (for a single exposure) = 61,848.38 seconds (Exposure ID: WFC3.A329264) Time to Saturation for the lens (for a single exposure) = 18,804 seconds Input values for ETC: Diameter of the source = 1.03 arcsec (this is the diameter of a circle that has the same area of the assumed Einstein ring) Radius of the extraction region = 0.52 arcsec (this is equal to half of the diameter of the source) The effective signal-to-noise ratio, SNR_eff, is estimated as SNR_eff = 1/(1/SNR_etc + B_L*0.01/B_S) where - SNR_etc is the signal-to-noise ratio returned by the exposure time calculator for the input exposure time; - B_L is the surface brightness of the lensing galaxy at a distance theta_E (i.e. the Einstein radius) from its center; - B_S is the surface density of the background source (assumed to be lensed into an Einstein ring). The adopted values for B_L and B_S are: B_L = 10.1 microJy per square arcseconds B_S = 1.93 microJy per square arcseconds The scheduling data was generated by CASM 18.3.1. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12194 :visit-id "04" :proposal-version -1 :trans-version "20100505" :date "09-Jul-2010 13:24:47.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "30" :si-bright-earth-limb-angle 20.0 :data-volume 2123888 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12194 :visit-id "04" :obset-id "04" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12194 :visit-id "04" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2870 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3234 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12194 :visit-id "04" :orbit-number 2 :pcs-time 222 :si-vis-utilization 2840 :al-overhead-at-end 0 :internal-dur-at-end 331 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3234 :pcs-gap 0 ) true 2 0 4-dither pattern. total time = 352.935x4 sec (for 1024x1024 image size) This gives SNR = 585.10 (4 frames) and a Time to Saturation (for a single exposure) = 11,982.17 seconds (Exposure ID: WFC3.A329266) Input values for ETC: Diameter of the source = 2.12 arcsec (this is the diameter of a circle that has the same area of the source light profile) Radius of the extraction region = 0.705 arcsec (this is equal to half of the FWHM of the source light profile) 2-dither pattern. total time = 552.937x2 sec (for 1024x1024 image size) This gives SNR = 177.95 (2 frames), corresponding to an effective SNR = 54.7 and a Time to Saturation (for a single exposure) = 34,482.63 seconds (Exposure ID: WFC3.A329268) Time to Saturation for the lens (for a single exposure) = 17,214 seconds Input values for ETC: Diameter of the source = 1.09 arcsec (this is the diameter of a circle that has the same area of the assumed Einstein ring) Radius of the extraction region = 0.55 arcsec (this is equal to half of the diameter of the source) The effective signal-to-noise ratio, SNR_eff, is estimated as SNR_eff = 1/(1/SNR_etc + B_L*0.01/B_S) where - SNR_etc is the signal-to-noise ratio returned by the exposure time calculator for the input exposure time; - B_L is the surface brightness of the lensing galaxy at a distance theta_E (i.e. the Einstein radius) from its center; - B_S is the surface density of the background source (assumed to be lensed into an Einstein ring). The adopted values for B_L and B_S are: B_L = 12.9 microJy per square arcseconds B_S = 10.2 microJy per square arcseconds 4-dither pattern. total time = 652.938x4 sec (for 1024x1024 image size) This gives SNR = 276.91 (4 frames), corresponding to an effective SNR = 61.5 and a Time to Saturation (for a single exposure) = 34,482.63 seconds (Exposure ID: WFC3.A329271) Time to Saturation for the lens (for a single exposure) = 17,214 seconds Input values for ETC: Diameter of the source = 1.09 arcsec (this is the diameter of a circle that has the same area of the assumed Einstein ring) Radius of the extraction region = 0.55 arcsec (this is equal to half of the diameter of the source) The effective signal-to-noise ratio, SNR_eff, is estimated as SNR_eff = 1/(1/SNR_etc + B_L*0.01/B_S) where - SNR_etc is the signal-to-noise ratio returned by the exposure time calculator for the input exposure time; - B_L is the surface brightness of the lensing galaxy at a distance theta_E (i.e. the Einstein radius) from its center; - B_S is the surface density of the background source (assumed to be lensed into an Einstein ring). The adopted values for B_L and B_S are: B_L = 12.9 microJy per square arcseconds B_S = 10.2 microJy per square arcseconds The scheduling data was generated by CASM 18.3.1. CASM was run in Phase II mode. (Tic-Visit :proposal-id 12194 :visit-id "05" :proposal-version -1 :trans-version "20100505" :date "09-Jul-2010 13:24:50.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "30" :si-bright-earth-limb-angle 20.0 :data-volume 2123888 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12194 :visit-id "05" :obset-id "05" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12194 :visit-id "05" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2870 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3234 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12194 :visit-id "05" :orbit-number 2 :pcs-time 222 :si-vis-utilization 2840 :al-overhead-at-end 0 :internal-dur-at-end 331 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3234 :pcs-gap 0 ) true 2 0 4-dither pattern. total time = 352.935x4 sec (for 1024x1024 image size) This gives SNR = 465.63 (4 frames) and a Time to Saturation (for a single exposure) = 21,929.71 seconds (Exposure ID: WFC3.A329278) Input values for ETC: Diameter of the source = 3.03 arcsec (this is the diameter of a circle that has the same area of the source light profile) Radius of the extraction region = 1.24 arcsec (this is equal to half of the FWHM of the source light profile) 2-dither pattern. total time = 552.937x2 sec (for 1024x1024 image size) This gives SNR = 26.68 (2 frames), corresponding to an effective SNR = 9.8 and a Time to Saturation (for a single exposure) = 66,596.33 seconds (Exposure ID: WFC3.A329279) Time to Saturation for the lens (for a single exposure) = 35,741.23 seconds Input values for ETC: Diameter of the source = 1.06 arcsec (this is the diameter of a circle that has the same area of the assumed Einstein ring) Radius of the extraction region = 0.53 arcsec (this is equal to half of the diameter of the source) The effective signal-to-noise ratio, SNR_eff, is estimated as SNR_eff = 1/(1/SNR_etc + B_L*0.01/B_S) where - SNR_etc is the signal-to-noise ratio returned by the exposure time calculator for the input exposure time; - B_L is the surface brightness of the lensing galaxy at a distance theta_E (i.e. the Einstein radius) from its center; - B_S is the surface density of the background source (assumed to be lensed into an Einstein ring). The adopted values for B_L and B_S are: B_L = 7.80 microJy per square arcseconds B_S = 1.20 microJy per square arcseconds 4-dither pattern. total time = 652.938x4 sec (for 1024x1024 image size) This gives SNR = 41.88 (4 frames), corresponding to an effective SNR = 11.3 and a Time to Saturation (for a single exposure) = 66,596.33 seconds (Exposure ID: WFC3.A329281) Time to Saturation for the lens (for a single exposure) =35,741.23 seconds Input values for ETC: Diameter of the source = 1.06 arcsec (this is the diameter of a circle that has the same area of the assumed Einstein ring) Radius of the extraction region = 0.53 arcsec (this is equal to half of the diameter of the source) The effective signal-to-noise ratio, SNR_eff, is estimated as SNR_eff = 1/(1/SNR_etc + B_L*0.01/B_S) where - SNR_etc is the signal-to-noise ratio returned by the exposure time calculator for the input exposure time; - B_L is the surface brightness of the lensing galaxy at a distance theta_E (i.e. the Einstein radius) from its center; - B_S is the surface density of the background source (assumed to be lensed into an Einstein ring). The adopted values for B_L and B_S are: B_L = 7.80 microJy per square arcseconds B_S = 1.20 microJy per square arcseconds