14490( 2) - 21-Mar-2016 20:08:08 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 14490 Version: 2 Check-in Time: 21-Mar-2016 20:08:08 STScI Edit Number: 0 Title Pop III material found 6 Gyr after the Big Bang? COS constraints on the lowest-metallicity gas at z<1 ------------------------------------------------------------------------------------ Type Cycle GO 23 ------------------------------------------------------------------------------------ Investigators Contact? PI: Prof. J. Christopher Howk University of Notre Dame Y CoI: Dr. John M. O'Meara Saint Michaels College Y CoI: Dr. Nicolas Lehner University of Notre Dame N CoI: Mr. Christopher Wotta University of Notre Dame N CoI: Prof. Joseph Ribaudo Utica College N CoI: Dr. Jason X. Prochaska University of California - Santa Cruz N ------------------------------------------------------------------------------------ Abstract The explosions of Population III stars provided the first metal pollution of the Universe. These stars eventually polluted their own and other nearby halos with sufficient metals to allow the formation of a more normal, less top-heavy population of stars. The subsequent Pop II stars produced the majority of the metals seen in the Universe today. However, is that pollution complete? While some ultra-metal poor stars in the Galactic halo may be fossils of the Pop III epoch, are there regions of the Universe that remain untouched by Pop II metal pollution at low redshift? We have identified a z~0.9 Lyman limit system - a dense stream of gas likely associated with a galaxy halo - with [Mg/H] < -2.4 on the basis of a low-resolution COS snapshot observation. We propose a 5 orbit COS NUV program to attempt to determine the metallicity of this gas through the very strong C III 977 Ang transition, pushing our sensitivity to [C/H] < -3.3, i.e., into the regime of Pop III-only enrichment at metallicities comparable to the z~4 IGM. We will also use these data to confirm our H I column density and study the temperature and kinematics of the gas using Lyman series absorption. With our statistical sample of metallicities in 60 LLSs, these observations will allow us to determine the fraction of high over-density gas at z<1 that remains relatively pristine, perhaps unenriched since the Pop III epoch. ------------------------------------------------------------------------------------ Observations Description ------------------------ We have recently identified a Lyman limit system (LLS) - a dense stream of gas with H I column density log N(HI) ~ 17.2 - at z<1 that may have been unenriched since the epoch of Population III stars. This system was chosen from a sample of LLSs identified in a Cycle 18 snapshot survey and is H I selected. Our proposed observations will target the z=0.89759 LLS toward J1500+4836 using the COS G185M grating with central wavelength setting 1850. This setting fortuitously provides coverage of most of the Lyman series lines for this absorber (spanning strengths from Ly -betathrough Ly-20) plus metal lines C II 1036, C III 977, and O VI 1031. Given the metallicity limits for this absorber, we do not expect to detect C II, but it provides a consistency check on our models. In 5 orbits we will obtain S/N~8 per resolution element for the metal 14490( 2) - 21-Mar-2016 20:08:08 - [ 2] transitions and S/N~6 for the higher-order Lyman series lines ------------------------------------------------------------------------------------ 14490( 2) - 21-Mar-2016 20:08:08 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 SDSSJ1500+48 GALAXY, QSO RA=15H00M31.7900S +/- 0.1", J2000 Z = V = 16.74 +/- 0.02 36 DEC=+48D36'46.85" +/- 0.1" 1.02848 Reference Frame: ICRS Extended: NO ------------------------------------------------------------------------------------------------------------------------------------ 14490( 2) - 21-Mar-2016 20:08:08 - [ 4] Visit: 01 (J1500 Spectroscopy) 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 SDSSJ1500+4 COS/NUV ACQ/IMA PSA MIRRORB 1 90 S (90 836 GE S) Comments: Used as input for the ETC a model of the observed spectrum. This uses a Telfer composite continuum absorbed by the Lyman limit systems we have fit along this sight line. The use of the model allows us to extend the flux to longer wavelengths as needed for the imaging. ------------------------------------------------------------------------------------------------------------------------------------ 2 SDSSJ1500+4 COS/NUV TIME-TA PSA G185M 1850 BUFFER-TIME=1600, FP-POS=1 1 2500 S 836 G (2500 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 SDSSJ1500+4 COS/NUV TIME-TA PSA G185M 1850 BUFFER-TIME=1600, FP-POS=2 1 3100 S 836 G (3100 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 SDSSJ1500+4 COS/NUV TIME-TA PSA G185M 1850 BUFFER-TIME=1600, FP-POS=3 1 3100 S 836 G (3100 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 | ------------------------------------------------------------------------------------------------------------------------------------ SDSSJ1500+4836 1 COS/NUV ACQ/IMA PSA MIRRORB none none none none 1 N/A GE SDSSJ1500+4836 2 COS/NUV TIME-TA PSA G185M 1850 none none none none 1 N/A G SDSSJ1500+4836 3 COS/NUV TIME-TA PSA G185M 1850 none none none none 2 N/A G SDSSJ1500+4836 4 COS/NUV TIME-TA PSA G185M 1850 none none none none 3 N/A G 14490( 2) - 21-Mar-2016 20:08:08 - [ 5] Visit: 02 (J1500 Spectroscopy) 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 SDSSJ1500+4 COS/NUV ACQ/IMA PSA MIRRORB 1 90 S (90 836 GE S) Comments: Used as input for the ETC a model of the observed spectrum. This uses a Telfer composite continuum absorbed by the Lyman limit systems we have fit along this sight line. The use of the model allows us to extend the flux to longer wavelengths as needed for the imaging. ------------------------------------------------------------------------------------------------------------------------------------ 2 SDSSJ1500+4 COS/NUV TIME-TA PSA G185M 1850 BUFFER-TIME=1600, FP-POS=1 1 2500 S 836 G (2500 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 SDSSJ1500+4 COS/NUV TIME-TA PSA G185M 1850 BUFFER-TIME=1600, FP-POS=4 1 3100 S 836 G (3100 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 | ------------------------------------------------------------------------------------------------------------------------------------ SDSSJ1500+4836 1 COS/NUV ACQ/IMA PSA MIRRORB none none none none 1 N/A GE SDSSJ1500+4836 2 COS/NUV TIME-TA PSA G185M 1850 none none none none 1 N/A G SDSSJ1500+4836 3 COS/NUV TIME-TA PSA G185M 1850 none none none none 2 N/A G 14490( 2) - 21-Mar-2016 20:08:08 - [ 6] Summary Form for Proposal 14490 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PSA ------------------------------------------------------------------------------------------------------------------------------------ Configurations COS/NUV ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/IMAGE, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=1600, FP-POS=1, FP-POS=2, FP-POS=3, FP-POS=4 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G185M, MIRRORB ------------------------------------------------------------------------------------------------------------------------------------ Target Names SDSSJ1500+4836 ------------------------------------------------------------------------------------------------------------------------------------