15470( 4) - 18-Dec-2018 14:44:08 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 15470 Version: 4 Check-in Time: 18-Dec-2018 14:44:08 STScI Edit Number: 1 Title SXDF308: challenging the Case-B assumption in Extreme Emission Line Galaxies ------------------------------------------------------------------------------------ Type Cycle GO 25 ------------------------------------------------------------------------------------ Investigators Contact? PI: Prof. Claudia Scarlata University of Minnesota - Twin Cities Y CoI: Vihang Mehta University of Minnesota - Twin Cities N CoI: Dr. Micaela Bagley University of Minnesota - Twin Cities N CoI: Prof. Matthew James Hayes Stockholm University N CoI: Prof. Nino Panagia Space Telescope Science Institute N ------------------------------------------------------------------------------------ Abstract We propose a comprehensive study of SXDF308, a compact, low-mass galaxy with extreme emission lines. The emission line spectrum of this objects shares many similarities with those of the most metal poor galaxies currently known (e.g., Skillman+2013) as well as with the Green Peas, the only galaxy population with confirmed substantial escape of Lyman Continuum ionizing radiation (Vanzella+2016, Izotov+2018, Jaskot+2018). However, critically, the Balmer decrement (Halpha/Hbeta) measured from ground-based spectroscopy suggests that the common Case B assumption often invoked to interpret emission line spectra may not be valid in this object. A low Halpha/Hbeta ratio may in fact be a common feature of extreme emission line galaxies: 32 out of 41 Green Pea galaxies in the Yang+(2017) sample have Halpha/Hbeta ratio smaller than Case-B. If the Case B assumption does not apply to EELGs, then that most of the intrinsic physical properties determined for these galaxies are severely incorrect! Here we request 3 orbits with COS-G140L and 2 orbits with WFC3-UVIS, with the goal of fully characterize: 1) the spatial distribution of the ionized gas and stars using the high resolution optical and UV WFCS/UVIS imaging, along with 2) the physical properties of the HII regions and the nature of the ionizing sources using COS FUV spectroscopy and thus, 3) confirm the validity and impact of the fundamental assumptions associated in the inference of physical properties of these galaxies. ------------------------------------------------------------------------------------ Observations Description ------------------------ This project will obtain two orbits of WFC3+UVIS multiband imaging of SXDF308. We will image the target in the F275W, F336W, F438W broad band filters and in the F547M, F621M, F689M and F763M medium band filters. To reduce overhead and minimize CTE effects we use the UVIS-C512C-SUB aperture for imaging. We add a POST-FLASH flux to each exposure, to ensure a minimum charge packet of 12 electrons (http://www.stsci.edu/hst/wfc3/ins_performance/CTE). The POST-FLASH was computed using the ETC. We will also observe the target for three orbits, with COS-G140L. We have added a time constraint to the COS visit, to observe it after the WFC3-UVIS visit has been executed. Once the UVIS observations are conducted we 15470( 4) - 18-Dec-2018 14:44:08 - [ 2] will immediately obtain the images from MAST, process them, and make the size and flux measurements in the F275W, to opitmize the exposure time of the COS acquisition image. We'll use ACQ/IMAGE for target acquisition, and then do four exposures of spectroscopy in the G140L grating with CENWAVE=1280. We'll use FP-POS = ALL to best remove fixed pattern noise. ------------------------------------------------------------------------------------ 15470( 4) - 18-Dec-2018 14:44:08 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 SXDF308 ISM, HII REGION RA=02H19M12.8590S +/- 0.1", J2000 V = 20.05 +/- 0.01 DEC=-04D30'17.65" +/- 0.1" Reference Frame: ICRS Extended: NO ------------------------------------------------------------------------------------------------------------------------------------ 15470( 4) - 18-Dec-2018 14:44:08 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-LINE-3PT Pattern_Purpose DITHER Number_Of_Points 3 Point_Spacing 0.135 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 46.84 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 15470( 4) - 18-Dec-2018 14:44:08 - [ 5] Visit: 01 (Imaging) 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 SXDF308 WFC3/UVI ACCUM UVIS2-C51 F621M FLASH=9 1 170 S (510 PATTERN 1 1-7 S 2C-SUB S) Comments: The ETC link shows how we determined the POST-FLASH value: we assumed a source with a magnitude of 40, to ensure only background flux was present. ------------------------------------------------------------------------------------------------------------------------------------ 2 SXDF308 WFC3/UVI ACCUM UVIS2-C51 F275W FLASH=11 1 450 S S 2C-SUB (1350 S) Comments: The ETC link shows how we determined the POST-FLASH value: we assumed a source with a magnitude of 40, to ensure only background flux was present. ------------------------------------------------------------------------------------------------------------------------------------ 3 SXDF308 WFC3/UVI ACCUM UVIS2-C51 F547M FLASH=11 1 100 S (300 S 2C-SUB S) Comments: The ETC link shows how we determined the POST-FLASH value: we assumed a source with a magnitude of 40, to ensure only background flux was present. ------------------------------------------------------------------------------------------------------------------------------------ 4 SXDF308 WFC3/UVI ACCUM UVIS2-C51 F438W FLASH=11 1 200 S (600 S 2C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 5 SXDF308 WFC3/UVI ACCUM UVIS2-C51 F763M FLASH=11 1 100 S (300 S 2C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 6 SXDF308 WFC3/UVI ACCUM UVIS2-C51 F689M FLASH=11 1 100 S (300 S 2C-SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 7 SXDF308 WFC3/UVI ACCUM UVIS2-C51 F336W FLASH=11 1 260 S S 2C-SUB see below (909 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 | ------------------------------------------------------------------------------------------------------------------------------------ SXDF308 1 WFC3/UVI ACCUM UVIS2-C5 F621M 1 none none none 1 N/A S 12C-SUB 15470( 4) - 18-Dec-2018 14:44:08 - [ 6] 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 | ------------------------------------------------------------------------------------------------------------------------------------ SXDF308 1 WFC3/UVI ACCUM UVIS2-C5 F621M 2 none none none 1 N/A S 12C-SUB SXDF308 1 WFC3/UVI ACCUM UVIS2-C5 F621M 3 none none none 2 N/A S 12C-SUB SXDF308 2 WFC3/UVI ACCUM UVIS2-C5 F275W 1 none none none 1 N/A S 12C-SUB SXDF308 2 WFC3/UVI ACCUM UVIS2-C5 F275W 2 none none none 1 450.0 S S 12C-SUB SXDF308 2 WFC3/UVI ACCUM UVIS2-C5 F275W 3 none none none 2 N/A S 12C-SUB SXDF308 3 WFC3/UVI ACCUM UVIS2-C5 F547M 1 none none none 1 N/A S 12C-SUB SXDF308 3 WFC3/UVI ACCUM UVIS2-C5 F547M 2 none none none 1 N/A S 12C-SUB SXDF308 3 WFC3/UVI ACCUM UVIS2-C5 F547M 3 none none none 2 N/A S 12C-SUB SXDF308 4 WFC3/UVI ACCUM UVIS2-C5 F438W 1 none none none 1 N/A S 12C-SUB SXDF308 4 WFC3/UVI ACCUM UVIS2-C5 F438W 2 none none none 2 N/A S 12C-SUB SXDF308 4 WFC3/UVI ACCUM UVIS2-C5 F438W 3 none none none 2 N/A S 12C-SUB SXDF308 5 WFC3/UVI ACCUM UVIS2-C5 F763M 1 none none none 1 N/A S 12C-SUB SXDF308 5 WFC3/UVI ACCUM UVIS2-C5 F763M 2 none none none 2 N/A S 12C-SUB SXDF308 5 WFC3/UVI ACCUM UVIS2-C5 F763M 3 none none none 2 N/A S 12C-SUB SXDF308 6 WFC3/UVI ACCUM UVIS2-C5 F689M 1 none none none 1 N/A S 12C-SUB SXDF308 6 WFC3/UVI ACCUM UVIS2-C5 F689M 2 none none none 2 N/A S 12C-SUB SXDF308 6 WFC3/UVI ACCUM UVIS2-C5 F689M 3 none none none 2 N/A S 12C-SUB SXDF308 7 WFC3/UVI ACCUM UVIS2-C5 F336W 1 none none none 1 280.0 S S 12C-SUB SXDF308 7 WFC3/UVI ACCUM UVIS2-C5 F336W 2 none none none 2 310.0 S S 12C-SUB SXDF308 7 WFC3/UVI ACCUM UVIS2-C5 F336W 3 none none none 2 319.0 S S 12C-SUB 15470( 4) - 18-Dec-2018 14:44:08 - [ 7] Visit: 02 (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 SXDF308 COS/NUV ACQ/IMA PSA MIRRORA 1 100 S (100 GE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SXDF308 COS/FUV TIME-TA PSA G140L 1280 FP-POS=ALL, BUFFER-TIME=22000, 1 1395 S G FLASH=YES, SEGMENT=BOTH see below (7736 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 | ------------------------------------------------------------------------------------------------------------------------------------ SXDF308 1 COS/NUV ACQ/IMA PSA MIRRORA none none none none 1 N/A GE SXDF308 2 COS/FUV TIME-TA PSA G140L 1280 none none none 1 1 2290.0 S G SXDF308 2 COS/FUV TIME-TA PSA G140L 1280 none none none 2 2 1335.0 S G SXDF308 2 COS/FUV TIME-TA PSA G140L 1280 none none none 3 2 1335.0 S G SXDF308 2 COS/FUV TIME-TA PSA G140L 1280 none none none 4 3 2776.0 S G 15470( 4) - 18-Dec-2018 14:44:08 - [ 8] Summary Form for Proposal 15470 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PSA, UVIS2-C512C-SUB ------------------------------------------------------------------------------------------------------------------------------------ Configurations COS/FUV, COS/NUV, WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, ACQ/IMAGE, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=22000, FLASH=11, FLASH=9, FLASH=YES, FP-POS=ALL, SEGMENT=BOTH ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 1 1-7 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F275W, F336W, F438W, F547M, F621M, F689M, F763M, G140L, MIRRORA ------------------------------------------------------------------------------------------------------------------------------------ Target Names SXDF308 ------------------------------------------------------------------------------------------------------------------------------------