15433( 4) - 06-Dec-2018 19:51:47 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 15433 Version: 4 Check-in Time: 06-Dec-2018 19:51:47 STScI Edit Number: 0 Title The first UV emission line spectrum of a strong low-z Lyman continuum leaker - a key to studying the sources of cosmic reionization ------------------------------------------------------------------------------------ Type Cycle GO 25 ------------------------------------------------------------------------------------ Investigators Contact? PI: Prof. Daniel Schaerer Observatoire de Geneve Y CoI: Dr. Yuri I. Izotov Ukrainian National Academy of Sciences, N BITP CoI: Prof. Trinh Xuan Thuan The University of Virginia N CoI: Dr. Anne Verhamme Observatoire de Geneve N CoI: Dr. Gabor Worseck Universitat Potsdam N CoI: Dr. John Chisholm University of California - Santa Cruz N CoI: Dr. Kimihiko Nakajima University of Copenhagen, Niels Bohr N Institute ------------------------------------------------------------------------------------ Abstract Few UV templates of low-z star-forming galaxies covering all major UV emission lines between 1200 and 2000 Ang (i.e. Lyman-alpha, HeII, CIV, CIII], OIII], and others) exist and most importantly none for galaxies with known Lyman continuum (LyC) leakage. Selecting for high [OIII]/[OII]>4 optical line ratios and compactness, our team has recently achieved a breakthrough in the identification of Lyman continuum leaking galaxies with high escape fraction (fesc=6-13%), which currently represent the best analogs of the sources of cosmic reionization. In recent (20-21 july 2017) COS/HST observations we discovered a new LyC leaker showing very strong Lyman continuum flux, with an escape fraction fesc=46+-3%, the highest LyC escape fractions observed so far in low-z galaxies. We here request STIS spectroscopy of this unique source to measure the complete UV spectrum, including all of the above UV lines. The proposed observations will provide for the first time an empirical UV emission line spectrum of Lyman continuum leakers, which are rare at low redshift but whose properties are very similar to those of common high-z star-forming galaxies. Obtaining rest-UV spectra of Lyman continuum leakers, currently the best analogs of the sources of cosmic reionization, is both crucial and urgent for upcoming studies with the JWST and the largest ground-based facilities. ------------------------------------------------------------------------------------ Observations Description ------------------------ So far, we have observed the Lyman continuum and the Ly-alpha line with COS, using the G140L and G160M grisms in the FUV channel, which is in practice limited to wavelengths shorter than 2000 A. At z > 0.3 the UV lines of interest here (primarily C iv 1550, He ii 1640, O iii] 1661, 1666, C iii] 1907, 1909) are at 2000-2600 A, a range which is in principle observable with the NUV channel of COS or with STIS. STIS observations are preferred for this spectral range, since the NUV channel of COS is not well calibrated, STIS is more sensitive in the 1700-3200 A domain, and has no spectral gaps. Our goal is to obtain spatially integrated flux measurements for the emission lines. A low 15433( 4) - 06-Dec-2018 19:51:47 - [ 2] spectral resolution is thus sufficient. The G230L (MAMA) has a higher throughput than the G230LB (CCD) at < 2250. Since most lines (C iv 1550, He ii 1640, O iii]1661, 1666) are at observed wavelengths 2000-2160 A and C iii] 1907, 1909 is likely the strongest, we prefer G230L (MAMA). Our objects are very compact (by selection), both from ground-based imaging (SDSS) and from the COS FUV acquisition images, where the objects show UV surface brightness profiles with exponential scale heights of 0.6-1.4 kpc, corresponding to 0.13-0.32 arcsec. Observations with the 0.5 arcsec slit will thus capture most of the emission line flux, even if it was somewhat more extended than the UV continuum. The wider slit (2 arcsec) is not optimal because it would degrade the spectral resolution and reduce the contrast of narrow nebular lines against the continuum, making them harder to detect. The exposure time was determined to reach a S/N=3 for weak lines of EWrest=1 A to place also strong constraints on the emission lines in case of non-detection. C iii] 1908 equivalent widths of 5-15 A are not uncommon in normal star-forming galaxies with low metallicities. The other targetted lines (C iv 1550, He ii 1640, and O iii] 1666) are normally considerably weaker. We used the STIS ETC using the known continuum flux (from COS spectra and/or GALEX photometry) at 2000 A rest-frame. We adopted the extended object option with 0.5 arcsec in diameter. The required time corresponds to 8 orbits. The observations will be split into two visits, 4 orbits each. Our object is sufficiently bright and compact for standard target acquisition with short overheads. ------------------------------------------------------------------------------------ 15433( 4) - 06-Dec-2018 19:51:47 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 J1154+2443 GALAXY, DWARF COMPACT, RA=11H54M48.8500S +/- 0.4", J2000 Z = V = 21.77 +/- 0.05 FUV=22.10+/-0.26, EMISSION LINE NEBULA, DEC=+24D43'33.02" +/- 0.4" 0.369 NUV=21.57+/-0.24, acq=870s, STARBURST spectrum=23000s, http://etc.stsci.edu/etc/results/STIS.s p.1026387 Reference Frame: ICRS Extended: NO Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.0 0.0 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 15433( 4) - 06-Dec-2018 19:51:47 - [ 4] Visit: 01 (J1154+2443visit1) 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 J1154+2443 STIS/CCD ACQ F28X50LP MIRROR ACQTYPE=POINT 1 180 S (180 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 J1154+2443 STIS/NUV TIME-TA 52X0.5 G230L 2376 BUFFER-TIME=1014.0 1 2300.0 S -MAMA G see below (1579 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 J1154+2443 STIS/NUV TIME-TA 52X0.5 G230L 2376 BUFFER-TIME=1014.0 1 2300.0 S -MAMA G see below (2967 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 J1154+2443 STIS/NUV TIME-TA 52X0.5 G230L 2376 BUFFER-TIME=1014.0 1 2300.0 S -MAMA G see below (2944 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 J1154+2443 STIS/NUV TIME-TA 52X0.5 G230L 2376 BUFFER-TIME=1014.0 1 2300.0 S -MAMA G see below (2944 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 | ------------------------------------------------------------------------------------------------------------------------------------ J1154+2443 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A J1154+2443 2 STIS/NUV TIME-TA 52X0.5 G230L 2376 none none none none 1 1579.0 S -MAMA G J1154+2443 3 STIS/NUV TIME-TA 52X0.5 G230L 2376 none none none none 2 2967.0 S -MAMA G J1154+2443 4 STIS/NUV TIME-TA 52X0.5 G230L 2376 none none none none 3 2944.0 S -MAMA G J1154+2443 5 STIS/NUV TIME-TA 52X0.5 G230L 2376 none none none none 4 2944.0 S -MAMA G 15433( 4) - 06-Dec-2018 19:51:47 - [ 5] Visit: 02 (J1154+2443visit2) Visit Requirements: SAME ORIENT AS 01 On Hold Comments: Additional Comments: Same orientation as in visit J1154+2443visit1. 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 J1154+2443 STIS/CCD ACQ F28X50LP MIRROR ACQTYPE=POINT 1 180 S (180 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 J1154+2443 STIS/NUV TIME-TA 52X0.5 G230L 2376 BUFFER-TIME=1014.0 1 2300.0 S -MAMA G see below (1579 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 J1154+2443 STIS/NUV TIME-TA 52X0.5 G230L 2376 BUFFER-TIME=1014.0 1 2300.0 S -MAMA G see below (2967 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 J1154+2443 STIS/NUV TIME-TA 52X0.5 G230L 2376 BUFFER-TIME=1014.0 1 2300.0 S -MAMA G see below (2944 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 J1154+2443 STIS/NUV TIME-TA 52X0.5 G230L 2376 BUFFER-TIME=1014.0 1 2300.0 S -MAMA G see below (2944 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 | ------------------------------------------------------------------------------------------------------------------------------------ J1154+2443 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A J1154+2443 2 STIS/NUV TIME-TA 52X0.5 G230L 2376 none none none none 1 1579.0 S -MAMA G J1154+2443 3 STIS/NUV TIME-TA 52X0.5 G230L 2376 none none none none 2 2967.0 S -MAMA G J1154+2443 4 STIS/NUV TIME-TA 52X0.5 G230L 2376 none none none none 3 2944.0 S -MAMA G J1154+2443 5 STIS/NUV TIME-TA 52X0.5 G230L 2376 none none none none 4 2944.0 S -MAMA G 15433( 4) - 06-Dec-2018 19:51:47 - [ 6] Visit: 52 (J1154+2443visit2) Visit Requirements: On Hold Comments: Additional Comments: Duplicate of failed visit 02 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 J1154+2443 STIS/CCD ACQ F28X50LP MIRROR ACQTYPE=POINT 1 180 S (180 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 J1154+2443 STIS/NUV TIME-TA 52X0.5 G230L 2376 BUFFER-TIME=1014.0 1 2300.0 S -MAMA G see below (1579 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 J1154+2443 STIS/NUV TIME-TA 52X0.5 G230L 2376 BUFFER-TIME=1014.0 1 2300.0 S -MAMA G see below (2967 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 J1154+2443 STIS/NUV TIME-TA 52X0.5 G230L 2376 BUFFER-TIME=1014.0 1 2300.0 S -MAMA G see below (2944 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 J1154+2443 STIS/NUV TIME-TA 52X0.5 G230L 2376 BUFFER-TIME=1014.0 1 2300.0 S -MAMA G see below (2944 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 | ------------------------------------------------------------------------------------------------------------------------------------ J1154+2443 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A J1154+2443 2 STIS/NUV TIME-TA 52X0.5 G230L 2376 none none none none 1 1579.0 S -MAMA G J1154+2443 3 STIS/NUV TIME-TA 52X0.5 G230L 2376 none none none none 2 2967.0 S -MAMA G J1154+2443 4 STIS/NUV TIME-TA 52X0.5 G230L 2376 none none none none 3 2944.0 S -MAMA G J1154+2443 5 STIS/NUV TIME-TA 52X0.5 G230L 2376 none none none none 4 2944.0 S -MAMA G 15433( 4) - 06-Dec-2018 19:51:47 - [ 7] Summary Form for Proposal 15433 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 52X0.5, F28X50LP ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD, STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT, BUFFER-TIME=1014.0 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements SAME ORIENT AS 01 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G230L, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names J1154+2443 ------------------------------------------------------------------------------------------------------------------------------------