16175( 5) - 02-Feb-2022 20:53:27 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 16175 Version: 5 Check-in Time: 02-Feb-2022 20:53:27 STScI Edit Number: 0 Title Can Very Massive Stars form at the low-metallicity threshold of the nearby Universe? ------------------------------------------------------------------------------------ Type Cycle GO 28 ------------------------------------------------------------------------------------ Investigators Contact? PI: Prof. Aida Wofford Universidad Nacional Autonoma de Mexico, Y Obs. Astron. Nac. CoI: Dr. Linda J. Smith Space Telescope Science Institute N CoI: Prof. Matthew James Hayes Stockholm University N ------------------------------------------------------------------------------------ Abstract Very massive stars (VMS, >100 Msun) dominate the ionization and mechanical feedback in star-forming regions for the first few Myr. Evidence for VMS has been found from UV observations of young (< 3 Myr), massive star clusters (>5x10^4 Msun), in the LMC and two nearby starbursts. Larger samples of these stars are needed in order to determine the upper mass limit of the IMF and complete our understanding of massive star evolution. In addition, since JWST will obtain numerous UV rest-frame spectra of young high redshift galaxies, it is essential that we investigate whether VMS are common in local, low metallicity analogs, while we still have access to the UV domain. SBS 0335-052E is one of the nearest most metal-poor analogs and contains several super star clusters (SSC) of 10^5 M_sun. From ground-based optical spectroscopy, candidate Wolf-Rayet (WR) have been found in cluster 3 of the galaxy (SSC3). Given its young age, large mass, and WR-like signatures, SSC3 could host VMS. We request co-spatial STIS G140L UV + G430L optical 52x0.2 long-slit spectroscopy of SSC3 in SBS 0335-052E. The requested observations will cover the high-ionization UV emission lines of C IV, He II, and O III], and the optical He II 4686 line. Dust attenuation will be obtained from the UV to optical He II ratio. We will use the co-spatial UV + optical data to test if WR stars alone can explain the observed properties of SSC3 or if VMS are necessary. The observations will provide important constraints to state-of-the-art spectral synthesis models of the kind that will be used to interpret rest-frame UV spectra of the most distant galaxies, with future large telescopes. ------------------------------------------------------------------------------------ Observations Description ------------------------ We will use 8 orbits of HST and the STIS 52"x0.2" long slit to observe super star cluster 3 in SBS 0335-052E. Two visits are requried because STIS/MAMA visits must not be more than 5 orbit. Orient. We request the same orient of the slit for visits 1 and 2. Target acquisition. An ACS WFC F435W image was used to locate a GSC2 star to use as offset. The offset to cluster 3 was measured from the offset star coordinates on the HST image. We will acquire the GSC2 star with the CCD F28x50LP configuration in ACQ mode. With an exposure time of 3 s, we can reach a SNR of 100 with the latter configuration. We will then offset from the star to cluster 3. Spectroscopy. We will use gratings G140L and G430L in ACCUM mode. 16175( 5) - 02-Feb-2022 20:53:27 - [ 2] Orbits. The Vega magnitudes of SSC3 in ACS HRC filters F435W and F220W are 20.85 and 18.79 mag, respectively. We use the latter magnitues in order to calculate the exposure times to reach a SNR of 10 in the continuum of 4686*(1+z) and SNR of 5 in the continuum of 1640*(1+z). For the G430L observations, we assume that the target is a point source with a power law index of -2.6 and a normalization in the Vega system of 20.85 mag in filter ACS/WFC1/F435W. For the G140L observations we normalize to 18.79 mag in filter WFC3/UVIS1/F225W. The redshift of SBS 0335-052E is z=0.0135. ------------------------------------------------------------------------------------ 16175( 5) - 02-Feb-2022 20:53:27 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 OFFSET-STAR STAR, F0-F2 RA=03H37M48.0200S +/- 0.1", J2000 V = 15.4 DEC=-05D02'8.95" +/- 0.1" Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 2 SBS0335-052E EXT-CLUSTER, KNOT, STAR RA-OFF=-0.0167708D, J2000 V = 20.98 -3 FORMING REGION DEC-OFF=-0.0081909D, FROM 1 ------------------------------------------------------------------------------------------------------------------------------------ 16175( 5) - 02-Feb-2022 20:53:27 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type STIS-ALONG-SLIT Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 0.5 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 90.0 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 16175( 5) - 02-Feb-2022 20:53:27 - [ 5] Visit: 01 (CCD) 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 OFFSET-STAR STIS/CCD ACQ F28X50LP MIRROR 1 3 S (3 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SBS0335-052 STIS/CCD ACQ/PEA 52X0.1 MIRROR 1 50 S (50 E-3 K S) ------------------------------------------------------------------------------------------------------------------------------------ 3 SBS0335-052 STIS/CCD ACCUM 52X0.2 G430L 4300 1 2566 S PATTERN 1 3 E-3 see below (3952 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 | ------------------------------------------------------------------------------------------------------------------------------------ OFFSET-STAR 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A SBS0335-052E-3 2 STIS/CCD ACQ/PEA 52X0.1 MIRROR none none none none 1 N/A K SBS0335-052E-3 3 STIS/CCD ACCUM 52X0.2 G430L 4300 1 none none 1 1 687.0 S SBS0335-052E-3 3 STIS/CCD ACCUM 52X0.2 G430L 4300 1 none none 2 1 687.0 S SBS0335-052E-3 3 STIS/CCD ACCUM 52X0.2 G430L 4300 2 none none 1 2 1289.0 S SBS0335-052E-3 3 STIS/CCD ACCUM 52X0.2 G430L 4300 2 none none 2 2 1289.0 S 16175( 5) - 02-Feb-2022 20:53:27 - [ 6] Visit: 02 (MAMA) Visit Requirements: SAME ORIENT AS 01 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 OFFSET-STAR STIS/CCD ACQ F28X50LP MIRROR 1 3 S (3 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SBS0335-052 STIS/CCD ACQ/PEA 52X0.1 MIRROR 1 50 S (50 E-3 K S) ------------------------------------------------------------------------------------------------------------------------------------ 3 SBS0335-052 STIS/FUV ACCUM 52X0.2 G140L 1425 1 2725 S PATTERN 1 3 E-3 -MAMA see below (4118 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 SBS0335-052 STIS/FUV ACCUM 52X0.2 G140L 1425 1 2725 S PATTERN 1 4 E-3 -MAMA see below (2676 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 | ------------------------------------------------------------------------------------------------------------------------------------ OFFSET-STAR 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A SBS0335-052E-3 2 STIS/CCD ACQ/PEA 52X0.1 MIRROR none none none none 1 N/A K SBS0335-052E-3 3 STIS/FUV ACCUM 52X0.2 G140L 1425 1 none none none 1 1393.0 S -MAMA SBS0335-052E-3 3 STIS/FUV ACCUM 52X0.2 G140L 1425 2 none none none 2 N/A -MAMA SBS0335-052E-3 4 STIS/FUV ACCUM 52X0.2 G140L 1425 1 none none none 3 1338.0 S -MAMA SBS0335-052E-3 4 STIS/FUV ACCUM 52X0.2 G140L 1425 2 none none none 3 1338.0 S -MAMA 16175( 5) - 02-Feb-2022 20:53:27 - [ 7] Visit: 03 (MAMA) 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 OFFSET-STAR STIS/CCD ACQ F28X50LP MIRROR 1 3 S (3 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SBS0335-052 STIS/CCD ACQ/PEA 52X0.1 MIRROR 1 50 S (50 E-3 K S) ------------------------------------------------------------------------------------------------------------------------------------ 3 SBS0335-052 STIS/FUV ACCUM 52X0.2 G140L 1425 1 2725 S PATTERN 1 3 E-3 -MAMA see below (4118 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 SBS0335-052 STIS/FUV ACCUM 52X0.2 G140L 1425 1 2725 S PATTERN 1 4 E-3 -MAMA see below (2676 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 | ------------------------------------------------------------------------------------------------------------------------------------ OFFSET-STAR 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A SBS0335-052E-3 2 STIS/CCD ACQ/PEA 52X0.1 MIRROR none none none none 1 N/A K SBS0335-052E-3 3 STIS/FUV ACCUM 52X0.2 G140L 1425 1 none none none 1 1393.0 S -MAMA SBS0335-052E-3 3 STIS/FUV ACCUM 52X0.2 G140L 1425 2 none none none 2 N/A -MAMA SBS0335-052E-3 4 STIS/FUV ACCUM 52X0.2 G140L 1425 1 none none none 3 1338.0 S -MAMA SBS0335-052E-3 4 STIS/FUV ACCUM 52X0.2 G140L 1425 2 none none none 3 1338.0 S -MAMA 16175( 5) - 02-Feb-2022 20:53:27 - [ 8] Visit: 04 (MAMA - Repeat) 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 OFFSET-STAR STIS/CCD ACQ F28X50LP MIRROR 1 3 S (3 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SBS0335-052 STIS/CCD ACQ/PEA 52X0.1 MIRROR 1 50 S (50 E-3 K S) ------------------------------------------------------------------------------------------------------------------------------------ 3 SBS0335-052 STIS/FUV ACCUM 52X0.2 G140L 1425 1 2725 S PATTERN 1 3 E-3 -MAMA see below (4118 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 | ------------------------------------------------------------------------------------------------------------------------------------ OFFSET-STAR 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A SBS0335-052E-3 2 STIS/CCD ACQ/PEA 52X0.1 MIRROR none none none none 1 N/A K SBS0335-052E-3 3 STIS/FUV ACCUM 52X0.2 G140L 1425 1 none none none 1 1393.0 S -MAMA SBS0335-052E-3 3 STIS/FUV ACCUM 52X0.2 G140L 1425 2 none none none 2 N/A -MAMA 16175( 5) - 02-Feb-2022 20:53:27 - [ 9] Summary Form for Proposal 16175 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 52X0.1, 52X0.2, F28X50LP ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD, STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, ACQ, ACQ/PEAK ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 1 3, PATTERN 1 4, SAME ORIENT AS 01 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G140L, G430L, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names OFFSET-STAR, SBS0335-052E-3 ------------------------------------------------------------------------------------------------------------------------------------