NIRSpec Multi-Object Spectroscopy of Distant Galaxies Pierre Ferruit & the NIRSpec GTO team & the NIRCam-NIRSpec galaxy assembly collaboration Proposal Planning Workshop STScI 15 May 2017 ESA UNCLASSIFIED - For Official Use
Contents of the presentation Introduction NIRSpec GTO program. Overview of the NIRCam-NIRSpec galaxy assembly program. More on the deep and medium MOS surveys. Some considerations (list of pay attention to points for when you will prepare proposals or participate to the tutorials). Conclusion ESA UNCLASSIFIED - For Official Use ESA 15/05/2017 Slide 2
Introduction NIRSpec GTO program In return for the provision of the NIRSpec spectrograph, the European Space Agency (ESA) has received a total allocation of 900 hours of JWST guaranteed time. Wall-clock time including direct and indirect overheads. Program managed by the ESA JWST project scientist and prepared by the NIRSpec GTO team. Team built around the NIRSpec Instrument Science Team. Program designed with two key objectives in mind: Scientific excellence (making good use JWST and of the GTO allocation) Probing key modes, observing strategies / regimes of NIRSpec http://www.cosmos.esa.int/web/jwst-nirspec-gto ESA UNCLASSIFIED - For Official Use ESA 15/05/2017 Slide 3
NIRCam-NIRSpec galaxy assembly survey The topic of galaxy formation and evolution is at the core of the NIRSpec GTO program MOS (deep, medium and wide) and IFS surveys. The deep and medium layers of the MOS survey are part of a combined NIRCam-NIRSpec imaging and spectroscopic survey. From P. Oesch et al. 2016 ESA UNCLASSIFIED - For Official Use ESA 15/05/2017 Slide 4
NIRCam-NIRSpec galaxy assembly survey Combining our JWST GTO time and the resources / expertise of our two teams to create a major program to study the physics of the assembly of galaxies. Combining time to be able to reach a critical size and maximize the scientific return of the survey. Combining imaging (NIRCam + MIRI) and spectroscopy (NIRSpec MOS). Designed to take advantage of NIRSpec-NIRCam coordinated parallels. ESA UNCLASSIFIED - For Official Use ESA 15/05/2017 Slide 5
NIRCam-NIRSpec galaxy assembly survey Studying the evolution of galaxies from its first steps (z>10), through the end of the dark ages (z=7-9) and the epoch of galaxy assembly (z=2-6). Pushing back the redshift frontier and understanding the very early stages of galaxy formation. Probing the epoch of reionization and the role of galaxies in the reionization. Tracking and understanding the build-up of stellar masses. Tracking and understanding the build-up of metals. Tracking and understanding the build-up of quiescent populations (feedback, quenching). Understanding the role of AGNs. And look for surprises ESA UNCLASSIFIED - For Official Use ESA 15/05/2017 Slide 6
NIRCam-NIRSpec galaxy assembly survey Key numbers for the deep imaging and spectroscopy layer: NIRCam imaging: area of 46 arcmin 2 centered on the HUDF/GOODS-S; depth of AB=29.8 (10 σ); at least 9 filters. 2 NIRSpec MOS pointings on the HUDF/GOODS-S; peak integration time of 100ks in CLEAR/PRISM; grating configurations targeting the emission lines. ESA UNCLASSIFIED - For Official Use ESA 15/05/2017 Slide 7
NIRCam-NIRSpec galaxy assembly survey Key numbers for the medium imaging and spectroscopy layer: NIRCam imaging: area of 190 arcmin 2 in GOODS-S and N; depth of AB=28.8 (10 σ); at least 9 filters. MIRI imaging: area of 14 arcmin 2 (deep area of 8 arcmin 2 ); depth of AB=26.7 in F770W. 24 NIRSpec MOS pointing in GOODS-S and N; peak integration time of 7ks (for 12 of the pointings) and 8.5ks (for 12 of the pointings) Caveat for both surveys: the actual integration times, total area and number of pointing may change as STScI updates the timing model for the overheads in the APT (we are working with a cap in hours). ESA UNCLASSIFIED - For Official Use ESA 15/05/2017 Slide 8
NIRCam-NIRSpec galaxy assembly survey NIRCam NIRCam MIRI MIRI GOODS-S GOODS-N NIRSpec NIRSpec NIRSpec NIRSpec ESA UNCLASSIFIED - For Official Use ESA 15/05/2017 Slide 9
NIRSpec MOS observations - DEEP Two deep pointings on HUDF/GOODS-S with identical exposure parameters but different target sets. DEEP/HST: target set coming from existing catalogs, i.e. with most sources coming from HST imaging programs. Can be executed independently of any NIRCam observation. DEEP/JWST: target set coming for the NIRCam deep and medium imaging surveys. Same-cycle follow-up of JWST imaging. Very interesting capability offered by STScI (available for GTOs and GOs, not ERS) ESA UNCLASSIFIED - For Official Use ESA 15/05/2017 Slide 10
NIRSpec MOS observations - DEEP NIRSpec ( prime ) NIRCam ( parallels ) CAUTION: exposure list and times are indicative as the NIRCam-NIRSpec coordinated parallels template is not yet available in the APT. SW arm LW arm Instrument) Configuration) Number) of) Photon) collecting) Exposure)type) exposures) time) NIRSpec( CLEAR/PRISM( 72( 27.7(h( NRSIRS2(ng=19( NIRSpec( F070LP/G140M( 18( 6.9(h( NRSIRS2(ng=19( NIRSpec( F170LP/G235M( 18( 6.9(h( NRSIRS2(ng=19( NIRSpec( F290LP/G395M( 18( 6.9(h( NRSIRS2(ng=19( NIRSpec( F290LP/G395H( 18( 6.9(h( NRSIRS2(ng=19( ( ( ( Matched exposures ( ( NIRCam(SW( F090W( 36( 13.8(h( DEEP8(ng=7( NIRCam(SW( F115W( 48( 18.3(h( DEEP8(ng=7( NIRCam(SW( F150W( 36( 13.8(h( DEEP8(ng=7( NIRCam(SW( F200W( 24( 9.2(h( DEEP8(ng=7( ( ( ( ( ( NIRCam(LW( F277W( 30( 11.5(h( DEEP8(ng=7( NIRCam(LW( F335M( 18( 6.9(h( DEEP8(ng=7( NIRCam(LW( F356W( 24( 9.2(h( DEEP8(ng=7( NIRCam(LW( F410M( 36( 13.8(h( DEEP8(ng=7( NIRCam(LW( F444W( 36( 13.8(h( DEEP8(ng=7( ( ESA UNCLASSIFIED - For Official Use ESA 15/05/2017 Slide 11
NIRSpec MOS observations - DEEP Observation strategy the 3-shutter nodding pattern Why is the number of NIRSpec exposures in the tables always a multiple of 3? Mini-slits made of 3 open microshutters Spectral direction The baseline observation strategy is to nod i.e. to move the object in each shutter in three consecutive exposures. è 3-shutter nodding pattern. This is the building block for our survey observations. If we repeat this 3-shutter nodding pattern at a different location on the micro-shutter array for the same set of sources, we say we dither. For the deep, we dither 3 times. ESA UNCLASSIFIED - For Official Use ESA 15/05/2017 Slide 12
NIRSpec MOS observations - DEEP We are planning to make a systematic use of NIRCam-NIRSpec coordinated parallels. Efficient use of JWST. Allows to get scientifically interesting imaging in parallels to the MOS observations at a small cost in terms of overheads. The NIRCam [imaging] NIRSpec [MOS] coordinated parallels template is not yet available in the APT (will be in the next version). à No tutorial during this proposal planning workshop (tool not yet ready) BUT I strongly recommend to consider using NIRCam in parallel whenever you plan to use NIRSpec. ESA UNCLASSIFIED - For Official Use ESA 15/05/2017 Slide 13
NIRSpec MOS observations - DEEP CAUTION: the fields of view of NIRCam and NIRSpec have different orientations on the sky. ESA UNCLASSIFIED - For Official Use ESA 15/05/2017 Slide 14
NIRSpec MOS observations - DEEP CLEAR/PRISM: continuum and emission-lines (some will be blended); highest sensitivity; simultaneous coverage of the complete wavelength range. M-gratings: emission-lines; line ratios and centroids; spectra are allowed to overlap to be able to observe the same objects as in CLEAR/ PRISM. H-grating: emission-lines; line centroids & profiles (probing the kinematics of the objects, outflows ); spectra are allowed to be truncated; spectra are allowed to overlap. ESA UNCLASSIFIED - For Official Use ESA 15/05/2017 Slide 15
NIRSpec MOS observations - DEEP CLEAR/PRISM: continuum and emission-lines (some will be blended); highest sensitivity; simultaneous coverage of the complete wavelength range. M-gratings: emission-lines; line ratios and centroids; spectra are allowed to overlap to be able to observe the same objects as in CLEAR/ PRISM. H-grating: emission-lines; line centroids & profiles (probing the kinematics of the objects, outflows ); spectra are allowed to be truncated; spectra are allowed to overlap. ESA UNCLASSIFIED - For Official Use ESA 15/05/2017 Slide 16
NIRSpec MOS observations - DEEP Allowing spectra to overlap? In the medium and high spectral resolution configurations, the spectra are long and can cross the complete detector. ESA UNCLASSIFIED - For Official Use ESA 15/05/2017 Slide 17
NIRSpec MOS observations - DEEP Allowing spectra to overlap? This is possible but think carefully before doing it and limit the number of possible overlaps. NIRSpec is not a slitless spectrograph, NIRISS and NIRCam do offer real, well designed slitless spectroscopy modes. The pipeline will not flag pixels where spectra overlap so you will have to do it yourself. Can still be worth the effort in some science cases. In our case, we decided to limit the overlap to typically <= 4 objects, allowing to observe the same objects at low, medium, high spectral resolution. ESA UNCLASSIFIED - For Official Use ESA 15/05/2017 Slide 18
NIRSpec MOS observations - DEEP Dec (J2000) 27 : 40 : 00.0 45 : 00.0 50 : 00.0 55 : 00.0 NIRCam Compact NIRCam Border NIRSpec Deep NIRSpec Medium/JWST NIRSpec Medium/HST MIRI NIRCam and NIRSpec GTO GOODS-S Coverage CANDELS region ACS UDF region Layout of the DEEP observations and of the associated parallels. NIRCam observations in parallel to the two DEEP pointings Two DEEP pointings Dec (J2000) NIRCam Compact NIRCam Border NIRSpec Deep NIRSpec Medium/JWST NIRSpec Medium/HST 27 : 40 : 00.0 MIRI 45 : 00.0 50 : 00.0 55 : 00.0 NIRCam and NIRSpec GTO GOODS-S Coverage CANDELS region ACS UDF region 33 : 00.00 40.00 20.00 32 : 00.00 3 : 31 : 40.00 RA (J2000) 33 : 00.00 40.00 20.00 32 : 00.00 3 : 31 : 40.00 RA (J2000) CAUTION: we did not really rotate the telescope, we are just observing at different times during the year! ESA UNCLASSIFIED - For Official Use ESA 15/05/2017 Slide 19
NIRSpec MOS observations - MEDIUM Like for the DEEP, the pointings can be divided in two categories: MEDIUM/HST: target set coming from existing catalogs, i.e. with most sources coming from HST imaging programs. Are executed in parallel to the main NIRCam MEDIUM observations (i.e. the pointings determined by the needs of the NIRCam survey). MEDIUM/JWST: target set coming for the NIRCam medium imaging surveys. Same-cycle follow-up of JWST imaging. NIRSpec is the real prime for these observations. ESA UNCLASSIFIED - For Official Use ESA 15/05/2017 Slide 20
NIRSpec MOS observations - MEDIUM NIRSpec ( prime ) NIRCam ( parallels ) CAUTION: exposure list and times are indicative as the NIRCam-NIRSpec coordinated parallels template is not yet available in the APT. SW arm LW arm Instrument) Configuration) Number) of) Photon) Exposure)type) exposures) collecting)time) NIRSpec( CLEAR/PRISM( 9( (8.5(ks)(2.37(h( NRSIRS2(ng=13( NIRSpec( F070LP/G140M( 9( (8.5(ks)(2.37(h( NRSIRS2(ng=13( NIRSpec( F170LP/G235M( 9( (8.5(ks)(2.37(h( NRSIRS2(ng=13( NIRSpec( F290LP/G395M( 9( (8.5(ks)(2.37(h( NRSIRS2(ng=13( NIRSpec( F290LP/G395H( 9( (8.5(ks)(2.37(h( NRSIRS2(ng=13( ( ( ( ( ( NIRCam(SW( F070W( 6( (5.7(ks)(1.58(h( DEEP8(ng=5( NIRCam(SW( F090W( 12( (11.3(ks)(3.15(h( DEEP8(ng=5( NIRCam(SW( F115W( 12( (11.3(ks)(3.15(h( DEEP8(ng=5( NIRCam(SW( F150W( 9( (8.5(ks)(2.36(h( DEEP8(ng=5( NIRCam(SW( F200W( 6( (5.7(ks)(1.58h( DEEP8(ng=5( ( ( ( ( ( NIRCam(LW( F277W( 9( (8.5(ks)(2.36(h( DEEP8(ng=5( NIRCam(LW( F335M( 6( (5.7(ks)(1.58(h( DEEP8(ng=5( NIRCam(LW( F356W( 6( (5.7(ks)(1.58(h( DEEP8(ng=5( NIRCam(LW( F410M( 12( (11.3(ks)(3.15(h( DEEP8(ng=5( NIRCam(LW( F444W( 12( (11.3(ks)(3.15(h( DEEP8(ng=5( ( ESA UNCLASSIFIED - For Official Use ESA 15/05/2017 Slide 21
NIRSpec MOS observations - MEDIUM Spectral direction This sequence is repeated for each of the MEDIUM pointing. The observation strategy for a single MOS MEDIUM pointing is very similar to the one for the DEEP. The total integration times and therefore the number of exposures is significantly lower. 2 dither positions for each set of sources instead of 3 for the DEEP. Remember, the bars are real. The filling factor of a shutter is only 62%. ESA UNCLASSIFIED - For Official Use ESA 15/05/2017 Slide 22
27 : 40 : 00.0 45 : 00.0 NIRCam Compact NIRCam Border NIRSpec Deep NIRSpec Medium/JWST NIRSpec Medium/HST MIRI NIRSpec MOS observations - MEDIUM Layout of the MEDIUM observations GOODS-S NIRCam and NIRSpec GTO GOODS-S Coverage CANDELS region ACS UDF region GOODS-S NIRCam Compact NIRCam Border NIRSpec Deep NIRSpec Medium/JWST NIRSpec Medium/HST 27 : 40 : 00.0 MIRI 45 : 00.0 NIRCam and NIRSpec GTO GOODS-S Coverage CANDELS region ACS UDF region NIRCam observations in parallel to the MEDIUM/JWST pointings Dec (J2000) 50 : 00.0 Dec (J2000) 50 : 00.0 NIRCam and NIRSpec GTO GOODS-S Coverage NIRCam Compact CANDELS region NIRCam Border ACS UDF region NIRSpec Deep NIRSpec Medium/JWST NIRSpec Medium/HST 27 : 40 : 00.0 MIRI 45 : 00.0 55 : 00.0 55 : 00.0 33 : 00.00 40.00 20.00 RA (J2000) MEDIUM/JWST 32 : 00.00 3 : 31 : 40.00 50 : 00.0 MEDIUM/HST 55 : 00.0 33 : 00.00 40.00 20.00 32 : 00.00 3 : 31 : 40.00 RA (J2000) 33 : 00.00 40.00 20.00 32 : 00.00 3 : 31 : 40.00 RA (J2000) Again different orientations correspond to different scheduling times (i.e. be careful before constraining the orientation!) ESA UNCLASSIFIED - For Official Use ESA 15/05/2017 Slide 23 Dec (J2000)
Some considerations In the early stages of the preparation of your proposal, think to take a look at the visibility of your targets. See the tutorial on the General Target Visibility Tool (GTVT). Get familiar with visibility constraints of JWST. At high ecliptic latitudes, constraining the orientation = constraining when your object can be observed. At low ecliptic latitudes, there will be strong constraints on the range of available orientations. Do not constrain the orientation if you do not need to, but check what is available. ESA UNCLASSIFIED - For Official Use ESA 15/05/2017 Slide 24
Some considerations Do not forget that NIRSpec MOS mode is unlike any other MOS mode. The grid of apertures is fixed. Preparing an observation implies picking the best matches between this fixed grid of apertures and the fixed grid of objects on the sky. A specific tool has been developed by STScI to help you doing just that: the MOS preparation tool = MPT, which is part of the APT for NIRSpec. See NIRSpec MOS related tutorials all along this workshop. ESA UNCLASSIFIED - For Official Use ESA 15/05/2017 Slide 25
Some considerations You will not be able to generate your final MOS observations with the final set of observed objects and micro-shutter array (MSA) configurations before 2019! Matching apertures with objects requires a very accurate knowledge of the JWST+NIRSpec distortion / plate scale and to know the orientation assigned to your observations. Representative mapping is available in the MPT and should be used to construct representative observations to assess in particular how many objects you can observe per pointing. Do not hesitate to play with the orientation also. ESA UNCLASSIFIED - For Official Use ESA 15/05/2017 Slide 26
Some considerations The centering of your targets in the apertures will vary from one target to the next (by design). Depending on how well you know the position of your targets with respect to the target acquisition reference targets, your science targets may not end up where planned. Hence the recommendation of a relative accuracy of 10 mas between the science and reference targets. BUT depending on your science case, you may not need such an accurate positioning. ESA UNCLASSIFIED - For Official Use ESA 15/05/2017 Slide 27
Some considerations Do not hesitate to tailor catalogs to each of your pointings. In particular for the type of observations I described where one wants to cover area on the sky, it is worth restricting the footprint of the catalog when working on a given pointing. Leave enough room to accommodate different orientations and to allow MPT to optimize the pointing.! We have typically used a circle of 3-arcmin radius around a nominal pointing position. ESA UNCLASSIFIED - For Official Use ESA 15/05/2017 Slide 28
Some considerations Anticipate that only a potentially small fraction of your catalog will be observable for a given pointing. Pointing = set of dithers (made of noddings) over which you want to observe one set of sources. A fixed grid of apertures means that you cannot get all your objects correctly centered, where correctly is defined by the type of targets and the science needs 62% base fill factor ~86% operability ESA UNCLASSIFIED - For Official Use ESA 15/05/2017 Slide 29
Some considerations Overlap between spectra may further restrict which objects can be observed at the same time. Avoiding overlap between spectra means that some objects in your catalog will not be compatible with each other. ESA UNCLASSIFIED - For Official Use ESA 15/05/2017 Slide 30
Some considerations Taking into account all these factors in a statistical way one can estimate NIRSpec MOS multiplex levels. To end up with a close to optimal MOS filling factor you need a high-density of targets. saturation ESA UNCLASSIFIED - For Official Use ESA 15/05/2017 Slide 31
Some considerations Potentially only a small fraction of your catalog will be observable for a given pointing.! this has policy consequences. We anticipate that you will be allowed to put more objects in your submission catalogs that you will be able to observe at the end of the day. Objects that you do not observe will be released and available to other proposals. Exact (duplication) policy rules are being written down and will be available at the time of calls for proposals. ESA UNCLASSIFIED - For Official Use ESA 15/05/2017 Slide 32
Some considerations Same-cycle MOS follow-up of JWST imaging is allowed [great!]. Recommended minimum distance between the imaging and the spectroscopic follow-up of 60 days out of which 28 days are allocated to STScI checks and scheduling. Actual minimum distance of 42 but in this case only 14 days are available for you to extract the sources from the NIRCam data and the preparation of the MOS observation. Can be much larger (less stress!) and you need to look at the visibility constraints on your objects to see what is possible! [again] ESA UNCLASSIFIED - For Official Use ESA 15/05/2017 Slide 33
Conclusion Like the other instruments, NIRSpec will be very powerful. There is a lot of things to think about when preparing a NIRSpec proposal so, start now! (preaching to the converted as you are attending this workshop ) Plenty of hands-on time during this workshop Likely Frenglish Thanks for your attention ESA UNCLASSIFIED - For Official Use ESA 15/05/2017 Slide 34