16749( 3) - 30-Jul-2021 17:55:34 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 16749 Version: 3 Check-in Time: 30-Jul-2021 17:55:34 STScI Edit Number: 0 Title Direct imaging of CGM substructure with 50 parsec resolution ------------------------------------------------------------------------------------ Type Cycle GO 29 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Nikki Nielsen Swinburne University of Technology Y CoI: Dr. Deanne B Fisher Swinburne University of Technology N CoI: Dr. Glenn G. Kacprzak Swinburne University of Technology N CoI: Dr. John Chisholm University of Texas at Austin N CoI: Dr. Christopher Martin California Institute of Technology N ------------------------------------------------------------------------------------ Abstract Starbursting galaxies present the best laboratory to study the CGM since they are likely undergoing strong accretion events which trigger intense star formation-driven outflows. However, very few observations exist that have directly imaged their CGM and quantified the fine-scale substructure. Recent ultra-deep Keck/KCWI observations have mapped optical emission lines in the CGM to a distance of over 30 kpc from IRAS08, a nearby starbursting galaxy with evidence for an ongoing accretion event. These KCWI observations contain bright emission line knots with sizes of order hundreds of parsecs and no evidence of stellar continuum, implying a lack of stars. The properties of these emission knots are consistent with cool, condensing clouds in recent simulations. However, the sizes from KCWI are near the seeing limit, and the continuum measurement is hampered by sky subtraction uncertainties. We aim to use HST to zoom in on this substructure in the CGM of IRAS08 and test hypotheses explaining the sub-kiloparsec features. We propose for 5 orbits of WFC3/UVIS to obtain the Halpha+[NII] (F665N) and broad-band starlight (F467M & F775W) to measure the sizes and fluxes of the CGM emission knots. These data will allow us to differentiate between three possible scenarios giving rise to these knots, including the cool condensing clouds predicted in high resolution simulations, external HII regions, and dwarf galaxies. These observations are part of a larger program to directly image the optical emission lines of the CGM in starbursting galaxies. This HST imaging will therefore be a Rosetta Stone for interpreting future data as we move into the new era of direct imaging of the CGM. ------------------------------------------------------------------------------------ Observations Description ------------------------ Narrowband filter F665N: Using the faintest CGM knot from the KCWI observations, we estimate an Halpha surface brightness by converting the knot's Hbeta surface brightness from KCWI to Halpha assuming no extinction. This gives an Halpha surface brightness of ~1x10^-17 erg s^-1 cm^-2 arcsec^-2. For SNR=10, the WFC3 UVIS ETC requires an exposure time of 1334 s (22.2 min), including a post flash of 16 electrons/pix to reach the recommended threshold of 20 electrons/pix to avoid poor CTE. The orbit visibility of our target is ~58 minutes, which allows for 46.8 min of exposure time per orbit, or two 23 min exposures, given typical overheads of 11.2 min. We opt to increase our exposure times by a factor of 2x in order to identify fainter emission peaks that may 16749( 3) - 30-Jul-2021 17:55:34 - [ 2] have been washed out due to poor spatial resolution in the KCWI data, which will allow us to measure knot sizes. This will increase our S/N to 15 on the nominal CGM knot measurement and serve to help make more robust observations. The F665N filter is likely to have very significant problems with low background, and is our most important filter for characterizing the morphology and size of the knots. We therefore opt to readout a subset of the pixels in the WFC3 array. We will use the 1k x 1k subarray, and use 3 separate pointings centered on the knots, one pointing per orbit. For each orbit we will use the WFC-UVIS-DITHER-LINE-3PT dither pattern. Thus we require 3 orbits with F665N to cover all CGM knots. Broadband filters F467M and F775W: In nearby spiral galaxies the median globular cluster luminosity is M_V~-7.5 mag (Harris 1991). Werk et al (2008) finds that external HII regions are comprised of associations of clusters. Those associations have magnitudes of M_V~-8 mag and sizes of 50-70 pc, which is similar to our resolution limit. If we consider a point source with M_V~-8 AB mag (apparent magnitude of 26 mag) at the distance of IRAS08, we can make a 5 sigma detection in F467M just under 1 orbit of HST time (including overheads). We can obtain a similar detection limit in F775W. We will use a full orbit for each filter with the WFC3-UVIS-DITHER-LINE-3PT dither pattern. To mitigate the CTE, the broadband filters require lower levels of post-flash, and therefore we can readout the entire field. Reduced-gyro operations are likely to have minimal impact given the small number of orbits requested and minimal adjustments in each orbit. ------------------------------------------------------------------------------------ 16749( 3) - 30-Jul-2021 17:55:34 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 2MASX-J08382 GALAXY, STARBURST RA=08H38M21.6251S, J2000 V = 14.16 309+6507160 DEC=+65D07'3.86" Reference Frame: Other: SIMBAD Comments: This object was generated by the target selector and retrieved from the SIMBAD database. We have offset the target coordinates slightly from SIMBAD to ensure the central disk is not in the CCD gap with the UVIS-CENTER aperture and to allow for a wider orient range for schedulability. Using the UVIS aperture reduces the available orient range. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2015.5 0.0 0.0 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 2 IRAS08339+65 EXT-MEDIUM, DAMPED RA=08H38M20.2804S, J2000 10^-16 erg s^-1 cm^-2 arcsec^-2 17CGM1 LYMAN ALPHA CLOUD, DEC=+65D07'40.56" EMISSION LINE NEBULA, HII REGION, IGM, KNOT Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 3 IRAS08339+65 EXT-MEDIUM, DAMPED RA=08H38M17.7760S, J2000 10^-16 erg s^-1 cm^-2 arcsec^-2 17CGM2 LYMAN ALPHA CLOUD, DEC=+65D08'1.08" EMISSION LINE NEBULA, HII REGION, IGM, KNOT Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 4 IRAS08339+65 EXT-MEDIUM, DAMPED RA=08H38M28.5740S, J2000 10^-16 erg s^-1 cm^-2 arcsec^-2 17CGM3 LYMAN ALPHA CLOUD, DEC=+65D07'44.22" EMISSION LINE NEBULA, HII REGION, IGM, KNOT Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 16749( 3) - 30-Jul-2021 17:55:34 - [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 16749( 3) - 30-Jul-2021 17:55:34 - [ 5] Visit: 01 (IRAS08 Wide bands) Visit Requirements: ORIENT 135D TO 150 D; ORIENT 315D TO 330 D On Hold Comments: Additional Comments: We have offset the target coordinates slightly from SIMBAD to ensure the central disk is not in the CCD gap with the UVIS-CENTER aperture and to allow for a wider orient range for schedulability. Using the UVIS aperture reduces the available orient range. 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 2MASX-J0838 WFC3/UVI ACCUM UVIS-CENT F467M FLASH=16 1 900 S PATTERN 1 1 2309+650716 S ER see below 0 (2820 S) Comments: Post-flash added to get the background levels to the new recommendation of 20 electrons/pix. ------------------------------------------------------------------------------------------------------------------------------------ 2 2MASX-J0838 WFC3/UVI ACCUM UVIS-CENT F775W FLASH=4 1 900 S PATTERN 1 2 2309+650716 S ER see below 0 (2820 S) Comments: Post-flash added to get the background levels to the new recommendation of 20 electrons/pix. ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ 2MASX-J08382309+650 1 WFC3/UVI ACCUM UVIS-CEN F467M 1 none none none 1 940 S 7160 S TER 2MASX-J08382309+650 1 WFC3/UVI ACCUM UVIS-CEN F467M 2 none none none 1 940 S 7160 S TER 2MASX-J08382309+650 1 WFC3/UVI ACCUM UVIS-CEN F467M 3 none none none 1 940 S 7160 S TER 2MASX-J08382309+650 2 WFC3/UVI ACCUM UVIS-CEN F775W 1 none none none 2 940 S 7160 S TER 2MASX-J08382309+650 2 WFC3/UVI ACCUM UVIS-CEN F775W 2 none none none 2 940 S 7160 S TER 2MASX-J08382309+650 2 WFC3/UVI ACCUM UVIS-CEN F775W 3 none none none 2 940 S 7160 S TER 16749( 3) - 30-Jul-2021 17:55:34 - [ 6] Visit: 02 (CGM Knots) Visit Requirements: ORIENT 345D TO 30 D; ORIENT 165D TO 210 D; ORIENT 250D TO 290 D; ORIENT 70D TO 110 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 IRAS08339+6 WFC3/UVI ACCUM UVIS2-C1K F665N FLASH=17 1 940 S PATTERN 1 1 517CGM1 S 1C-SUB see below (2901 S) Comments: Post-flash added to get the background levels to the new recommendation of 20 electrons/pix. ------------------------------------------------------------------------------------------------------------------------------------ 2 IRAS08339+6 WFC3/UVI ACCUM UVIS2-C1K F665N FLASH=17 1 950 S PATTERN 1 2 517CGM2 S 1C-SUB see below (2892 S) Comments: Post-flash added to get the background levels to the new recommendation of 20 electrons/pix. ------------------------------------------------------------------------------------------------------------------------------------ 3 IRAS08339+6 WFC3/UVI ACCUM UVIS2-C1K F665N FLASH=17 1 950 S PATTERN 1 3 517CGM3 S 1C-SUB see below (2892 S) Comments: Post-flash added to get the background levels to the new recommendation of 20 electrons/pix. ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ IRAS08339+6517CGM1 1 WFC3/UVI ACCUM UVIS2-C1 F665N 1 none none none 1 967.0 S S K1C-SUB IRAS08339+6517CGM1 1 WFC3/UVI ACCUM UVIS2-C1 F665N 2 none none none 1 967.0 S S K1C-SUB IRAS08339+6517CGM1 1 WFC3/UVI ACCUM UVIS2-C1 F665N 3 none none none 1 967.0 S S K1C-SUB IRAS08339+6517CGM2 2 WFC3/UVI ACCUM UVIS2-C1 F665N 1 none none none 2 964.0 S S K1C-SUB IRAS08339+6517CGM2 2 WFC3/UVI ACCUM UVIS2-C1 F665N 2 none none none 2 964.0 S S K1C-SUB IRAS08339+6517CGM2 2 WFC3/UVI ACCUM UVIS2-C1 F665N 3 none none none 2 964.0 S S K1C-SUB IRAS08339+6517CGM3 3 WFC3/UVI ACCUM UVIS2-C1 F665N 1 none none none 3 964.0 S S K1C-SUB 16749( 3) - 30-Jul-2021 17:55:34 - [ 7] 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 | ------------------------------------------------------------------------------------------------------------------------------------ IRAS08339+6517CGM3 3 WFC3/UVI ACCUM UVIS2-C1 F665N 2 none none none 3 964.0 S S K1C-SUB IRAS08339+6517CGM3 3 WFC3/UVI ACCUM UVIS2-C1 F665N 3 none none none 3 964.0 S S K1C-SUB 16749( 3) - 30-Jul-2021 17:55:34 - [ 8] Summary Form for Proposal 16749 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS-CENTER, UVIS2-C1K1C-SUB ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=16, FLASH=17, FLASH=4 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 135D TO 150 D, ORIENT 165D TO 210 D, ORIENT 250D TO 290 D, ORIENT 315D TO 330 D, ORIENT 345D TO 30 D, ORIENT 70D TO 110 D, PATTERN 1 1, PATTERN 1 2, PATTERN 1 3 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F467M, F665N, F775W ------------------------------------------------------------------------------------------------------------------------------------ Target Names 2MASX-J08382309+6507160, IRAS08339+6517CGM1, IRAS08339+6517CGM2, IRAS08339+6517CGM3 ------------------------------------------------------------------------------------------------------------------------------------