14751( 8) - 07-Feb-2017 15:26:21 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 14751 Version: 8 Check-in Time: 07-Feb-2017 15:26:21 STScI Edit Number: 4 Title Resolving Fe-rich Neutral ISM in a Massive Quiescent Galaxy at z~0.4 ------------------------------------------------------------------------------------ Type Cycle GO 24 ------------------------------------------------------------------------------------ Investigators Contact? PI: Mr. Fakhri S Zahedy University of Chicago Y CoI: Prof. Hsiao-Wen Chen University of Chicago Y CoI: Prof. Ann Zabludoff University of Arizona N CoI: Dr. Michael Rauch Carnegie Institution of Washington N ------------------------------------------------------------------------------------ Abstract Roughly 40% of elliptical galaxies are found to contain cool gas but exhibit no on-going star formation, indicating that some feedback mechanisms are at work. While AGN feedback is commonly thought to be responsible for quenching star formation in massive halos, recent work has reiterated the importance of feedback from old stellar populations, including Type Ia supernovae (SNe Ia). In Zahedy et al. (2016), we reported detections of ultra-strong MgII absorption (>3.6 Ang) at 1-2 effective radii of a massive quiescent lensing galaxy at z=0.408. Strong MgII, FeII, MgI, and CaII absorption are found at the lens redshift along two lensed QSO sightlines separated by ~8 kpc. The absorbers are resolved into 15 components with line-of-sight velocity spread of ~600 km/s. The large observed ionic column densities, N>1e14 cm^-2 suggest large neutral hydrogen column densities N(HI)>1e18 cm^-2 and a significant neutral gas fraction. The most striking feature is the uniformly large Fe/Mg ratio across the full 600 km/s velocity range, suggesting a large contribution in chemical enrichment from SNe Ia (>20%). Here we propose QSO absorption-line spectroscopy of this unique system using STIS and the G140L grating with the slit oriented along the two lensed QSOs. The goal is to determine N(HI) from observations of the full Lyman absorption series and gas-phase metallicity of the interstellar medium at two locations separated by ~8 kpc in an elliptical galaxy beyond the local universe. With a modest investment of HST time, we will be able to examine the extent SNe Ia-driven feedback in a distant quiescent galaxy using this unique double-lens system. ------------------------------------------------------------------------------------ Observations Description ------------------------ We will obtain medium-resolution (R~1200) FUV spectra of the two images of the lensed QSO HE0047-1756 using the FUV-MAMA detector and the G140L grating in the Space Telescope Imaging Spectrograph (STIS). The primary goals of the proposed FUV spectroscopic observations are (1) to determine the neutral hydrogen column density, N(HI), and (2) constrain the metallicity of the cool gas found in the ISM of the lensing galaxy. Exposure Time Estimation: Based on our previous experience, we estimate that a signal-to-noise ratio (SNR) of >10 is necessary to place strong constraints on N(HI) and the metallicity of the gas. From GALEX observations of the field around HE 14751( 8) - 07-Feb-2017 15:26:21 - [ 2] 0047-1756, the combined (the two QSO images are unresolved in GALEX) FUV magnitude of the two images is FUV(AB) = 18.50. Using optical flux ratio of image A and B from Wisotzki et al. (2004) of 3.5:1, we estimate that the FUV magnitudes of images A and B of HE0047-1756 are FUV(AB)_A =18.77 and FUV(AB)_B = 20.13, respectively. Since the STIS long-slit mode will allow us to observe both images simultaneously, our exposure time estimate is determined by the required exposure time to reach the desired SNR for the fainter QSO image (image B). Using the latest STIS exposure time calculator with the FOS QSO spectral template redshifted to z_em = 1.676 and scaled to FUV(AB_)B = 20.13, we estimate that a total exposure time of 125 minutes (7.5 ks) is required to reach the desired mean SNR >10 for both QSO images using the G140L grating and the 52"x0.2" long slit. Observing Strategy: The observations will be performed in a single visit consisting of three HST orbits. We plan to observe both images of the lensed QSO HE0047-1756 simultaneously, which requires the STIS long slit to be aligned along the line connecting the two QSO images on the sky. This slit alignment corresponds to HST orientation (ORIENT) angles of 35.49 and 215.49 degrees. We allow a range of +/-0.5 degree in the ORIENT angles, which given the 0.2"-wide long slit, the 1.4" separation of the two QSO images, and the PSF profile of FUV-MAMA will still include more than 90% of the light from both QSO images in the slit. Using the Bright Object Tool, we have confirmed that all bright sources within the aperture are safe for observations with FUV-MAMA. Onboard target acquisition of the brighter QSO image (HE0047-1756A, the listed coordinates of the target) will be performed using STIS/CCD and the F28X50LP filter in the first orbit of the visit. We have confirmed that there is no brighter point source within a 5" radius from HE0047-1756A. Following guide star acquisition and target acquisition (or guide star reacquisition for subsequent orbits), we request 2 sub-exposures for each orbit, corresponding to 2 dither positions of the STIS-ALONG-SLIT dither pattern. To ensure that all spectra taken in different orbits will fall on different areas of the FUV-MAMA detector, we will employ a 6-point dither pattern with a separation of 0.4" between steps. ------------------------------------------------------------------------------------ 14751( 8) - 07-Feb-2017 15:26:21 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HE0047-1756A GALAXY, GRAVITATIONAL RA=00H50M27.8030S +/- 0.25", J2000 Z = 1.67 V = 17.57 est. GALEX FUV(AB) = 18.77 B LENS, QSO DEC=-17D40'8.80" +/- 0.25" (A), 20.13 (B) Reference Frame: ICRS Comments: Listed coordinates are for image A (the brighter lensed QSO image). ------------------------------------------------------------------------------------------------------------------------------------ 2 HE0047-1756A GALAXY, GRAVITATIONAL RA=00H50M27.8030S +/- 0.25", J2000 Z = 1.67 V = 17.57 est. GALEX FUV(AB) = 18.77 B-COPY LENS, QSO DEC=-17D40'8.80" +/- 0.25" (A), 20.13 (B) Reference Frame: ICRS Comments: Listed coordinates are for image A (the brighter lensed QSO image). ------------------------------------------------------------------------------------------------------------------------------------ 14751( 8) - 07-Feb-2017 15:26:21 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type STIS-ALONG-SLIT Pattern_Purpose DITHER Number_Of_Points 6 Point_Spacing 0.4 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 90.0 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type STIS-ALONG-SLIT Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 0.4 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 90.0 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 14751( 8) - 07-Feb-2017 15:26:21 - [ 5] Visit: 01 Visit Requirements: ORIENT 214.99D TO 215.99 D; ORIENT 34.99D TO 35.99 D 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 HE0047-1756 STIS/CCD ACQ F28X50LP MIRROR ACQTYPE=POINT 1 10 S (10 AB S) ------------------------------------------------------------------------------------------------------------------------------------ 2 HE0047-1756 STIS/FUV ACCUM 52X0.2 G140L 1425 1 1000 S PATTERN 1 2 AB -MAMA see below (7689 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 | ------------------------------------------------------------------------------------------------------------------------------------ HE0047-1756AB 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A HE0047-1756AB 2 STIS/FUV ACCUM 52X0.2 G140L 1425 1 none none none 1 1128.0 S -MAMA HE0047-1756AB 2 STIS/FUV ACCUM 52X0.2 G140L 1425 2 none none none 1 1109.0 S -MAMA HE0047-1756AB 2 STIS/FUV ACCUM 52X0.2 G140L 1425 3 none none none 2 1363.0 S -MAMA HE0047-1756AB 2 STIS/FUV ACCUM 52X0.2 G140L 1425 4 none none none 2 1363.0 S -MAMA HE0047-1756AB 2 STIS/FUV ACCUM 52X0.2 G140L 1425 5 none none none 3 1363.0 S -MAMA HE0047-1756AB 2 STIS/FUV ACCUM 52X0.2 G140L 1425 6 none none none 3 1363.0 S -MAMA 14751( 8) - 07-Feb-2017 15:26:21 - [ 6] Visit: 02 Visit Requirements: ORIENT 214.99D TO 215.99 D; ORIENT 34.99D TO 35.99 D 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 HE0047-1756 STIS/CCD ACQ F28X50LP MIRROR ACQTYPE=POINT 1 10 S (10 GS ACQ SCENARIO BASE1B3 AB-COPY S) ------------------------------------------------------------------------------------------------------------------------------------ 2 HE0047-1756 STIS/FUV ACCUM 52X0.2 G140L 1425 1 1000 S GS ACQ SCENARIO BASE1B3; AB-COPY -MAMA see below PATTERN 2 2 (2237 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 | ------------------------------------------------------------------------------------------------------------------------------------ HE0047-1756AB-COPY 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A HE0047-1756AB-COPY 2 STIS/FUV ACCUM 52X0.2 G140L 1425 1 none none none 1 1128 S -MAMA HE0047-1756AB-COPY 2 STIS/FUV ACCUM 52X0.2 G140L 1425 2 none none none 1 1109 S -MAMA 14751( 8) - 07-Feb-2017 15:26:21 - [ 7] Summary Form for Proposal 14751 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 52X0.2, F28X50LP ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD, STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, ACQ ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements GS ACQ SCENARIO BASE1B3, ORIENT 214.99D TO 215.99 D, ORIENT 34.99D TO 35.99 D, PATTERN 1 2, PATTERN 2 2 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G140L, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names HE0047-1756AB, HE0047-1756AB-COPY ------------------------------------------------------------------------------------------------------------------------------------