15283( 3) - 06-Dec-2018 17:42:47 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 15283 Version: 3 Check-in Time: 06-Dec-2018 17:42:47 STScI Edit Number: 1 Title Witnessing the assembly of galaxies in an extended gas-rich structure at z~3.25 ------------------------------------------------------------------------------------ Type Cycle GO 25 ------------------------------------------------------------------------------------ Investigators Contact? PI: Mr. Ruari Mackenzie Durham Univ. Y CoI: Prof. Michele Fumagalli Durham Univ. N CoI: Mr. James Trayford Durham Univ. N CoI: Dr. Tom Theuns Durham Univ. N CoI: Dr. Lise Christensen University of Copenhagen, Niels Bohr N Institute CoI: Prof. Johan P. U. Fynbo University of Copenhagen, Niels Bohr N Institute CoI: Dr. Palle Moller European Southern Observatory - Germany N CoI: Dr. John M. O'Meara Saint Michaels College N CoI: Dr. Jason X. Prochaska University of California - Santa Cruz N CoI: Dr. Marc Rafelski Space Telescope Science Institute N CoI: Prof. Tom Shanks Durham Univ. N ------------------------------------------------------------------------------------ Abstract The direct study of star formation in Damped Lyman Alpha systems (DLAs), the reservoirs of the majority of neutral gas at high redshift, has previously been hampered by the lack of deep integral field spectroscopy for sensitive searches of faint host galaxies. Building on our successful HST "shot-in-the-dark" survey that has probed the in-situ star formation rate of z~2-3 DLAs, we have initiated a MUSE follow-up of 6 DLA signlines to overcome this bottleneck. In the first sightline we have studied, we have uncovered a ~40 kpc Lyman alpha emitting nebula, composed of two clumps within ~50 kpc of the DLA, suggestive of a merger or an extended protodisk. Within this structure, which is the largest nebula known to be associated with a z~3 DLA, we also found a compact continuum source with spectrophotometry consistent with a Lyman Break Galaxy at the same redshift. Aside from the LBG, the rest of the Lyman alpha structure has no continuum counterpart in deep UV and visible imaging. The LBG alone seems unable to power the Lyman alpha nebula and the morphology supports our conclusion that, most likely, this structure is powered by in-situ star formation below detection limit. However, from the Lyman alpha alone the origin of this incredible structure remains ambiguous. With this proposal, we aim to acquire high resolution, deep infrared imaging with HST to probe the rest-frame optical emission to search for the underlying stellar emission of this object and to infer the stellar mass of the LBG. With the powerful combination of HST and MUSE data, we will unravel the nature of this unique system. ------------------------------------------------------------------------------------ Observations Description ------------------------ We aim to detect the stellar light from a Lyman alpha emitting structure associated with a high column absorption line system at z~3 detected in a nearby QSO. Our main requirements are to minimize the impact of the QSO and a 15283( 3) - 06-Dec-2018 17:42:47 - [ 2] nearby bright star on the photometry of the structure. The QSO has H(AB)= 18.33 mag, several magnitude brighter compared to the targeted nebula counterparts which are estimated to be as faint as m(F160W, AB) = 27.56 mag at a separation of 2-6 arcsec. Given this magnitude contrast, it's critical the QSO isn't allowed to contaminate the structure either though diffraction spikes or by dithering the structure on to pixels affected by persistence from the bright quasar. To minimise the impact of diffraction spikes, we select only ORIENT angles which place the diffraction spikes away from the structure identified in Lyman alpha emission. Additionally, there is a bright star with H(AB)~9.0 mag at 45 arcsec away from the QSO and structure. The star is sufficiently bright that it would quickly saturate the detector and its extended PSF could contaminate the object of interest. We will offset the exposures from the default aperture such that the star falls outside the field of view. Because these offsets are in instrument coordinates we have also restricted the ORIENT angles to one single window so that there is no ambiguity in the direction of the offsets. To improve the spatial sampling and aid PSF subtraction, we dither between ramps. To control for persistence, we have adopted the LINE dither pattern to move along the line separating the QSO and the structure. This way the structure never falls on pixels which the QSO has fallen on in past exposures. We will use the longest wavelength wide filter F160W. In order to maximize the S/N for any faint counterparts of the Lyman alpha nebula we have chosen SPARS50 sample sequences with NSAMP=14. With this configuration we can get 4 exposures per orbit with dithers in between. Because we wish to do one dither pattern over the whole visit with a dither in between each exposure, we have selected only one sampling configuration. This leaves us with just 300s unused over the 3 orbits. This strategy gives us the desired S/N of 4.25 for our targeted F160W=27.56 depth. ------------------------------------------------------------------------------------ 15283( 3) - 06-Dec-2018 17:42:47 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 DLA-15H3 GALAXY, EMISSION LINE RA=02H55M18.7000S, J2000 Z = V = 20.00 +/- 0.1 QSO H band = 18.33 NEBULA, HIGH REDSHIFT DEC=+00D48'49.31" 3.996 (AB) GALAXY, LYMAN ALPHA CLOUD, QUASAR Reference Frame: ICRS Extended: YES Comments: The target is a z~4.0 quasar (H_AB=18.33) which was observed to host a Damped Lyman Alpha system at z~3.25 seen in absorption against the QSO continuum. This DLA was followed up with deep imaging and MUSE integral field spectroscopy to reveal an extended Lyman alpha emitting nebula at the same redshift as the DLA. A compact galaxy (I_AB=25.3) also likely embedded in the same structure. The nebula extends 2'' to 6'' from the QSO, the compact galaxy is 2.5'' from the QSO. ------------------------------------------------------------------------------------------------------------------------------------ 51 DLA-15H3-HOP GALAXY, EMISSION LINE RA=02H55M19.9000S, J2000 Z = V = 20.00 +/- 0.1 QSO H band = 18.33 R NEBULA, HIGH REDSHIFT DEC=+00D48'57.31" 3.996 (AB) GALAXY, LYMAN ALPHA CLOUD, QUASAR Reference Frame: ICRS Extended: YES Comments: The coordiates given are offset from the actual target. This is to move a bright star further from the FoV to limit the diffraction spikes. The target is a z~4.0 quasar (H_AB=18.33) which was observed to host a Damped Lyman Alpha system at z~3.25 seen in absorption against the QSO continuum. This DLA was followed up with deep imaging and MUSE integral field spectroscopy to reveal an extended Lyman alpha emitting nebula at the same redshift as the DLA. A compact galaxy (I_AB=25.3) also likely embedded in the same structure. The nebula extends 2'' to 6'' from the QSO, the compact galaxy is 2.5'' from the QSO. ------------------------------------------------------------------------------------------------------------------------------------ 15283( 3) - 06-Dec-2018 17:42:47 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type LINE Pattern_Purpose DITHER Number_Of_Points 12 Point_Spacing 1.5 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 330 Angle_Between_Sides Center_Pattern NO Pattern_Comments: The purpose of this proposal is to search for a faint continuum counterpart to the Lyman alpha emitting nebula associated with a DLA and get photometry of the compact galaxy. Due to the bright QSO (H_AB=18.33) being in very close proximity to the Lyman alpha nebula (2'') it is critical that persistence from the bright QSO not be allowed to contaminate the photometry of the nebula and compact galaxy. For this reason we have chosen a LINE dither pattern where in each dither we move along the direction connecting the nebula and the QSO such that the nebula never falls on pixels which the QSO fell on in previous exposures. We require dithering to better sample the PSF for subtraction of the QSO. We have chosen dithers which are not an integer number of pixels for this reason. ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type LINE Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 1.5 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 330 Angle_Between_Sides Center_Pattern NO Pattern_Comments: The purpose of this proposal is to search for a faint continuum counterpart to the Lyman alpha emitting nebula associated with a DLA and get photometry of the compact galaxy. Due to the bright QSO (H_AB=18.33) being in very close proximity to the Lyman alpha nebula (2'') it is critical that persistence from the bright QSO not be allowed to contaminate the photometry of the nebula and compact galaxy. For this reason we have chosen a LINE dither pattern where in each dither we move along the direction connecting the nebula and the QSO such that the nebula never falls on pixels which the QSO fell on in previous exposures. We require dithering to better sample the PSF for subtraction of the QSO. We have chosen dithers which are not an integer number of pixels for this reason. ------------------------------------------------------------------------------------------------------------------------------------ 15283( 3) - 06-Dec-2018 17:42:47 - [ 5] Visit: 01 (Main Visit) Visit Requirements: ORIENT 267D TO 295 D On Hold Comments: Additional Comments: Due to the proximity of the bright QSO (H_AB=18.33) and the potentially very faint continuum counterparts to the Lyman alpha nebula (F160W=27.56) it is critical the PSF of the QSO not contaminate the nebula or continuum galaxy, particularly the diffraction spikes which means restricting orient ranges. Initially we identified 4 orient ranges which would stop the diffraction spikes from overlapping the nebula. Additionally there is a very bright star close by (45 arcsec, H_AB=9.0) which must be dealt with by placing it outside the field of view. To do this we have offset the target with POS TARG. However because these offsets are in instrument coordinates they would change with different orient angles, and hence we have ultimately restricted the observation to 1 single orient range, the one which maximizes the time over which the visit can be executed. 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 DLA-15H3 WFC3/IR MULTIAC IR F160W NSAMP=14, SAMP-SEQ=SPARS50 1 DEF POS TARG -18, 37.5; CUM (7835.258 PATTERN 1 1 S) Comments: The goal of this proposal is to search for faint continuum counterparts to the Lyman alpha nebula associated with a DLA and to estimate the stellar mass of the compact galaxy. To accomplish the latter we use the longest wavelength wide filter, F160W. In order to maximize the S/N for any faint counterparts of the Lyman alpha nebula we have chosen SPARS50 sample sequences with NSAMP=14. With this configuration we can get 4 exposures per orbit with dithers in between. Because we wish to do one dither pattern over the whole visit with a dither in between each exposure we have selected only one sampling configuration, this leaves us with just 300s unused over the 3 orbits. This strategy gives us a S/N of 4.25 for our targeted F160W=27.56 depth. ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ DLA-15H3 1 WFC3/IR MULTIAC IR F160W 1 none none none 1 N/A CUM DLA-15H3 1 WFC3/IR MULTIAC IR F160W 2 none none none 1 N/A CUM 15283( 3) - 06-Dec-2018 17:42:47 - [ 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 | ------------------------------------------------------------------------------------------------------------------------------------ DLA-15H3 1 WFC3/IR MULTIAC IR F160W 3 none none none 1 N/A CUM DLA-15H3 1 WFC3/IR MULTIAC IR F160W 4 none none none 1 N/A CUM DLA-15H3 1 WFC3/IR MULTIAC IR F160W 5 none none none 2 N/A CUM DLA-15H3 1 WFC3/IR MULTIAC IR F160W 6 none none none 2 N/A CUM DLA-15H3 1 WFC3/IR MULTIAC IR F160W 7 none none none 2 N/A CUM DLA-15H3 1 WFC3/IR MULTIAC IR F160W 8 none none none 2 N/A CUM DLA-15H3 1 WFC3/IR MULTIAC IR F160W 9 none none none 3 N/A CUM DLA-15H3 1 WFC3/IR MULTIAC IR F160W 10 none none none 3 N/A CUM DLA-15H3 1 WFC3/IR MULTIAC IR F160W 11 none none none 3 N/A CUM DLA-15H3 1 WFC3/IR MULTIAC IR F160W 12 none none none 3 N/A CUM 15283( 3) - 06-Dec-2018 17:42:47 - [ 7] Visit: 51 (HOPR Orbit) Visit Requirements: ORIENT 274D TO 280 D On Hold Comments: Additional Comments: This is a repeat of the final orbit of our only visit, which failed due to the lock with the guide star being lost. We are attempting to detect faint galaxies near a quasar (H_AB=18.33), and so we have resticted the ORIENT to prevent the diffraction spikes affecting our targets and to ensure persistence from the quasar does not affect the target. We have also moved the center of the pointing again to further reduce a the affect of a nearby bright star, which was previousllly just outside the field of view. Due to the proximity of the bright QSO (H_AB=18.33) and the potentially very faint continuum counterparts to the Lyman alpha nebula (F160W=27.56) it is critical the PSF of the QSO not contaminate the nebula or continuum galaxy, particularly the diffraction spikes which means restricting orient ranges. Initially we identified 4 orient ranges which would stop the diffraction spikes from overlapping the nebula. Additionally there is a very bright star close by (45 arcsec, H_AB=9.0) which must be dealt with by placing it outside the field of view. To do this we have offset the target with POS TARG. However because these offsets are in instrument coordinates they would change with different orient angles, and hence we have ultimately restricted the observation to 1 single orient range, the one which maximizes the time over which the visit can be executed. 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 DLA-15H3-HO WFC3/IR MULTIAC IR F160W NSAMP=14, SAMP-SEQ=SPARS50 1 DEF POS TARG -18., 37.5; PR CUM (2611.753 PATTERN 2 1 S) Comments: The goal of this proposal is to search for faint continuum counterparts to the Lyman alpha nebula associated with a DLA and to estimate the stellar mass of the compact galaxy. To accomplish the latter we use the longest wavelength wide filter, F160W. In order to maximize the S/N for any faint counterparts of the Lyman alpha nebula we have chosen SPARS50 sample sequences with NSAMP=14. With this configuration we can get 4 exposures per orbit with dithers in between. Because we wish to do one dither pattern over the whole visit with a dither in between each exposure we have selected only one sampling configuration, this leaves us with just 300s unused over the 3 orbits. This strategy gives us a S/N of 4.25 for our targeted F160W=27.56 depth. ------------------------------------------------------------------------------------------------------------------------------------ 15283( 3) - 06-Dec-2018 17:42:47 - [ 8] 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 | ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ DLA-15H3-HOPR 1 WFC3/IR MULTIAC IR F160W 1 none none none 1 N/A CUM DLA-15H3-HOPR 1 WFC3/IR MULTIAC IR F160W 2 none none none 1 N/A CUM DLA-15H3-HOPR 1 WFC3/IR MULTIAC IR F160W 3 none none none 1 N/A CUM DLA-15H3-HOPR 1 WFC3/IR MULTIAC IR F160W 4 none none none 1 N/A CUM 15283( 3) - 06-Dec-2018 17:42:47 - [ 9] Summary Form for Proposal 15283 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures IR ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/IR ------------------------------------------------------------------------------------------------------------------------------------ Opmodes MULTIACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters NSAMP=14, SAMP-SEQ=SPARS50 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 267D TO 295 D, ORIENT 274D TO 280 D, PATTERN 1 1, PATTERN 2 1, POS TARG -18, 37.5, POS TARG -18., 37.5 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F160W ------------------------------------------------------------------------------------------------------------------------------------ Target Names DLA-15H3, DLA-15H3-HOPR ------------------------------------------------------------------------------------------------------------------------------------