1. Margaret Meixner (STScI, JHU) March 7, 2013
Hubble Science Briefing
Selecting the best targets for JWST: My personal journey as a MIRI team scientist
Margaret Meixner
(STScI, JHU)
March 7, 2013
In this talk I will describe my own personal journey to think up projects for this amazing observatory.
Hubble Science Briefing - Margaret Meixner
7 March 2013

2. Outline of Talk My personal story as a JWST/MIRI science team member
Astronomers prepare now to use the power of JWST (James Webb Space Telescope)
Spitzer and Herschel space observatories find thousands of forming stars in the Magellanic Clouds
Large Magellanic Cloud (LMC)
Small Magellanic Cloud (SMC)
My JWST programs on star formation in the Magellanic Clouds
How JWST will discover more forming stars in nearby, but more distant galaxies
7 March 2013
Hubble Science Briefing – Margaret Meixner 2

3. Margaret Meixner: Member of the JWST/MIRI Science Team
I got on the JWST/MIRI science team by writing a scientific proposal to study the Magellanic Clouds and dusty disks of forming stars. I have been allocated 60 hours of time on the
JWST observatory to pursue these ideas. I have been on this science team for a decade, and the serious scientific program development work is starting now.
7 March 2013
Hubble Science Briefing – Margaret Meixner 3

4. JWST Sensitivity: -typically detects at an order of magnitude fainter than recent and current observatories -lower is better!
This sensitivity plot is why I am inspired to start now to come up with appropriately vetted target lists for JWST.
Here I show the limiting flux density of a point source, measured at 10 sigma in 10,000 seconds of integration for some current, past and future observatories. JWST will be able to observe at typically an order of magnitude fainter than recent and current observatories. Not only that but the lower flux saturation limit for JWST means that many of the targets that could be observed with Spitzer or Hubble will be too bright… so we are talking about getting whole new target lists. It’s not just more of the same, it’s a whole new realm.
7 March 2013
Hubble Science Briefing – Margaret Meixner 4

5. JWST Sensitivity JWST launches in 2018;
appropriate target lists must be developed now…
And time is running out. JWST is launching in 2018: the time to develop appropriate target lists is now.
7 March 2013
Hubble Science Briefing – Margaret Meixner 5

6. James Webb Space Telescope (JWST)
7 March 2013
Hubble Science Briefing – Margaret Meixner 6

7. James Webb Space Telescope (JWST)
7 March 2013
Hubble Science Briefing – Margaret Meixner 7

8. James Webb Space Telescope (JWST)
Integrated Science Instrument Module
7 March 2013
Hubble Science Briefing – Margaret Meixner 8

9. Integrated Science Instrument Module (ISIM)
7 March 2013
Hubble Science Briefing – Margaret Meixner 9

10. Integrated Science Instrument Module (ISIM)
7 March 2013
Hubble Science Briefing – Margaret Meixner 10

11. James Webb Space Telescope: Webb ~2018
NIRSpec
NIRCam
MIRI
NIRISS
7 March 2013 11

12. The Mid-InfraRed Instrument (MIRI)
spectrograph
The instruments are being delivered. This is the Mid-Infrared Instrument or MIRI: the top part is the spectrograph and the bottom the imager.
MIRI was delivered in 2012.
Imager
7 March 2013
Hubble Science Briefing – Margaret Meixner 12

13. MIRI detector
7 March 2013
Hubble Science Briefing – Margaret Meixner 13

14. MIRI Arrives at Goddard
To Goddard Space flight center in Greenbelt, MD.
7 March 2013
Hubble Science Briefing – Margaret Meixner 14

15. MIRI Inspected at Goddard
MIRI has been carefully inspected and has passed its delivery requirements.
7 March 2013
Hubble Science Briefing – Margaret Meixner 15

16. MIRI Team
A very large team of people were needed to design, construct and test MIRI. This picture shows just the scientists involved, led by our fearless leaders, George Rieke and Gillian Wright. And here I am one of the many MIRI scientists on the stairs at the Ringberg Castle. As a member of the MIRI team I have some guaranteed time, and I am actively thinking of how to use it optimally.
7 March 2013
Hubble Science Briefing – Margaret Meixner 16

17. Why the Magellanic Clouds?
They act as a good astrophysical laboratory:
They are nearby: ~50 kpc (LMC) and ~60 kpc (SMC) [the Andromeda Galaxy is about 16 times farther away]
Mean metallicity (Z)* is similar to metallicity of the interstellar medium during Universe’s peak star formation epoch (z**~1.5)
LMC: Z~0.5 x Z
SMC: Z~0.2 x Z
Known tidal interactions between LMC and SMC, possibly the Milky Way
Long History of Studies & used as a proving ground:
Ideal Case study for galaxy evolution
*metallicity (Z) = percent of elements other than hydrogen and helium
**z = redshift
Among the nearby galaxies, the Large Magellanic Cloud (LMC) is the best astrophysical laboratory for such studies, because its proximity (~50 kpc, Feast 1999) and its favorable viewing angle (35, van der Marel & Cioni 2001) permits studies of the resolved stellar populations and ISM clouds. The LMC has a metallicity that is similar to the average galaxy’s metallicity during the peak star formation epoch (z~1.5) of the Universe. It has known tidal interactions with the Small Magellanic Cloud and Milky Way. It has a long history of studies and is used as a proving ground for many astrophysical techniques.
For all these reasons, it offers a well constrained case of one galaxy’s evolution for modelers.
Note:
Models based on physical laws help us gain an understanding of the physical universe.  When we get better information from observations, we can use those results to improve the models, making them more accurate.  With accurate models, we can make predictions about the physical universe, and test those predictions with observations.  The process is circular, as models and observations inform each other. 
7 March 2013
Hubble Science Briefing – Margaret Meixner 17

18. Spitzer Survey of the Large Magellanic Cloud (LMC):
Surveying the Agents of Galaxy Evolution (SAGE)
LMC, SAGE- MIPS: 70 m
JWST has a similar wavelength coverage as Spitzer and HST, but will operate more like HST in that it will be better at pointed, deep observations, instead of the large many-degree field of view surveys performed by Spitzer. So the many large surveys we have been pursuing - with Spitzer, Herschel, to some degree HST and ground-based observatories - will be critical to identify regions for follow up with JWST. A large focus of my research has been centered on surveys of the Large Magellanic Cloud with Spitzer SAGE, mapping the main disk of the LMC in all IRAC and MIPS bands.
This IRAC and MIPS composite, which was featured in Time magazine, shows visually the three key science targets of the SAGE survey in the LMC:
3.6 microns in blue reveals the old, evolved stellar population,
24 microns in red highlights the areas of new massive star formation, and
8.0 microns in green shows the choppy waves of dust emission from the diffuse ISM.
[IRAC = Infrared Array Camera; MIPS = Multiband Imaging Photometer for Spitzer]
The SAGE survey’s 100x better areal resolution and 1000x better point source sensitivity allows us to detect and separate the dusty stars from the diffuse ISM emission in a much better way than previously possible.
IRAC 3.6 m: old (evolved) stellar populations IRAC 8.0 m: dust emission from ISM MIPS 24 m: new massive star formation
SAGE team
Meixner et al. 2006
7 March 2013
Hubble Science Briefing – Margaret Meixner 18
Meixner et al. 2006

19. Spitzer wavelengths detect dust, stars & gas
This cartoon of the whole electromagnetic spectrum shows the wavelengths in microns. The Spitzer Space Telescope covers 3.6 to 160 microns which detected dust, stars and with the spectrograph, atomic and molecular gas line emission. JWST will cover the near-IR and Mid-IR, so stars and dust and gas. Hubble covers the Visible and Near-IR so mostly stars, and gas. In the next slide I will show a Herschel image which starts in the far-IR and extends to longer wavelengths known as submillimeter.
From
7 March 2013
JWST briefing - Margaret Meixner 19

20. LMC: Herschel Inventory of The Agents of Galaxy Evolution (HERITAGE)
SPIRE 250 m
PACS 160 m
PACS 100 m
And with Herschel HERITAGE mapping the LMC in 5 bands with PACS and SPIRE combined.
[PACS = Photodetecting Array Camera and Spectrometer; SPIRE = Spectral and Photometric Imaging Receiver]
This three color image of the LMC Herschel data highlights these difference:
white is hot dust
green-yellow is intermediate
red is the cooler dust emission, closest to the edge
HERITAGE Team;
Meixner et al.
submitted
7 March 2013
Hubble Science Briefing – Margaret Meixner 20

21. SAGE-SMC: Spitzer IRAC & MIPS Imaging of Small Magellanic Cloud (SMC)
We have also pursued mapping surveys of the SMC. Spitzer-SAGE is shown here, and the Herschel HERITAGE image was on the title slide.
Here is the same type of color composite with blue evolved stars, red massive star formation regions and green ISM (InterStellar Medium)
old (evolved) stellar populations
new massive star formation
dust emission from ISM
SAGE SMC team
Gordon et al. 2011
7 March 2013
Hubble Science Briefing – Margaret Meixner 21

22. SMC: Herschel HERITAGE
SPIRE 250 m
PACS 160 m
PACS 100 m
And with Herschel HERITAGE mapping the LMC in 5 bands, with PACS and SPIRE combined.
This three color image of the LMC Herschel data highlights these differences:
white is hot dust
green-yellow is intermediate
red is the cooler dust emission, closest to the edge
HERITAGE
Team;
Meixner et al.
submitted
7 March 2013
Hubble Science Briefing – Margaret Meixner 22

23. Why is studying dust important?
Goal of Spitzer and Herschel surveys:
to study lifecycle of baryonic matter using infrared and submillimeter emission from dust.
Why is studying dust important?
Dust is present at the key transition points of this life cycle
It is present in the ISM (which is the origin of the cycle)
Dust enshrouds the young stellar objects as they form
Dust is produced in the stellar winds of dying stars and in the explosive supernovae
7 March 2013
Hubble Science Briefing – Margaret Meixner 23

24. Tracing the Lifecycle of Baryonic Matter:
Intermediate mass stars
High mass stars
The overriding goals of these surveys is to study the lifecycle of baryonic matter using the infrared and submillimeter emission from dust. This works because dust is present at the key transition points of this life cycle. It is present in the ISM which is the origin of the cycle. Dust enshrouds the young stellar objects as they form. Dust is produced in the stellar winds of dying stars and in the explosive supernovae.
The interstellar medium (ISM) plays a central role in the evolution of galaxies as the birthsite of new stars and the repository of old stellar ejecta. The formation of new stars slowly consumes the ISM, locking it up for millions to billions of years. As these stars age, the winds from low mass, asymptotic giant branch (AGB) stars and high mass, red supergiants (RSGs), and supernova explosions inject nucleosynthetic products of stellar interiors into the ISM, slowly increasing its metallicity. This constant recycling and associated enrichment drives the evolution of a galaxy’s baryonic matter and changes its emission characteristics. Dust is present at these key transition phases of the ISM, star formation and stellar death. Spitzer and Herschel measure the emission from this dust and thereby quantifies the mass of the ISM, the rate of star formation and the mass-loss return from the dusty winds of evolved stars.
credit:
7 March 2013
Hubble Science Briefing – Margaret Meixner 24

25. Tracing the Lifecycle of Baryonic Matter:
Intermediate mass stars
High mass stars
YSOs
The overriding goals of these surveys is to study the lifecycle of baryonic matter using the infrared and submillimeter emission from dust. This works because dust is present at the key transition points of this life cycle. It is present in the ISM which is the origin of the cycle. Dust enshrouds the young stellar objects as they form. Dust is produced in the stellar winds of dying stars and in the explosive supernovae.
The interstellar medium (ISM) plays a central role in the evolution of galaxies as the birthsite of new stars and the repository of old stellar ejecta. The formation of new stars slowly consumes the ISM, locking it up for millions to billions of years. As these stars age, the winds from low mass, asymptotic giant branch (AGB) stars and high mass, red supergiants (RSGs), and supernova explosions inject nucleosynthetic products of stellar interiors into the ISM, slowly increasing its metallicity. This constant recycling and associated enrichment drives the evolution of a galaxy’s baryonic matter and changes its emission characteristics. Dust is present at these key transition phases of the ISM, star formation and stellar death. Spitzer and Herschel measure the emission from this dust and thereby quantifies the mass of the ISM, the rate of star formation and the mass-loss return from the dusty winds of evolved stars.
credit:
7 March 2013
Hubble Science Briefing – Margaret Meixner 25

26. Young Stellar Object Evolutionary Stages
Young Protostar:
Main Accretion Phase
Herschel
Spitzer
Evolved Accreting Protostar
Thick disk, accreting,
Herbig Ae/Be
Hubble & JWST
I now want to turn our attention to the discovery of Young Stellar Objects (YSOs) in the LMC and SMC… By YSOs, I mean forming stars embedded in varying degrees of dust.
At the top we have the young protostar with its main accretion phase that is most easily detected by the Herschel Space Mission.
Next the star has an accretion disk and is still accreting from the envelope and is most easily detected with Spitzer.
In the last two stages the envelope disappears, and the disk remains but is forming planets and also disappears; these stages are best studied with HST and JWST.
Hubble & JWST
Thin disk, T-Tauri
time
7 March 2013
Hubble Science Briefing – Margaret Meixner 26

27. Spitzer Discovers One Thousand Young Stellar Objects in the SMC
~1100 YSO candidates; ~900 new
N 66
8.0 mm
NGC 346
NGC 602
One of the most remarkable finds based on these surveys is the discovery of thousands of young stellar object candidates.
Top left plot: Before the launch of Spitzer there was only one known YSO in the SMC. In our recently submitted paper by Sewilo et al., we report ~1100 YSO candidates in the SMC, ~900 of which are new, tripling the number.
It is important to note that all YSO lists published based on Spitzer photometry are merely candidates, and that additional information such as spectroscopy are needed to confirm their status as YSOs.
Image notes:
Contamination: – 18 evolved stars
– 10 massive stars
– 34 Pne
– all confirmed YSOs (35)
– 99% of previously known YSO candidates that fulfill our criteria
Sewilo et al. submitted
7 March 2013
JWST briefing - Margaret Meixner
7 March 2013
Hubble Science Briefing – Margaret Meixner 27

28. Spitzer Discovers Two Thousand Young Stellar Objects in the LMC
SAGE IRAC 8 mm
Pre-Spitzer:
~20 protostars known
Spitzer:
~1000 YSO candidates
Whitney, Sewilo et al. (2008)
~1200 YSO candidates
Gruendl & Chu (2009)
We have had similar success on YSO searches in the LMC, finding about 1800 YSO candidates from two independent group efforts. These galaxy-wide searches increased the known YSO candidate lists in the LMC significantly over the ~20 that were known prior to Spitzer. These YSO candidate lists enable us to directly investigate the processes of star formation at lower metallicities similar to the metallicity during the epoch of peak star formation in the Universe.
Using JWST, we will be able to study the star formation process using similar techniques that have been used to study star formation in our galaxy. By comparing those results directly with the galactic results, we can learn how metallicity affects the star formation process.
The work on the LMC YSOs galaxy-wide search is published. It is a similar story, with very few (~20) known before Spitzer, and with ~1800 candidates now known. The results from both galaxy-wide searches are shown here, overlaid on the IRAC 8 micron image.
~1800 unique sources
Star Formation Rate: ~0.1 M/yr
7 March 2013
Hubble Science Briefing – Margaret Meixner 28

29. Spitzer Discovers Two Thousand Young Stellar Objects in the LMC
SAGE IRAC 8 mm
Pre-Spitzer:
~20 protostars known
Spitzer:
~1000 YSO candidates
Whitney, Sewilo et al. (2008)
~1200 YSO candidates
Gruendl & Chu (2009)
JWST will not be suited to redo the large scale surveys of the LMC and SMC, but it will provide amazing insights into these new YSO candidates discovered in the Spitzer surveys. Let’s focus in on this region of the box, which centers on N113.
~1800 unique sources
Star Formation Rate: ~0.1 M/yr
7 March 2013
Hubble Science Briefing – Margaret Meixner 29

30. Detailed study by Spitzer finds low-mass YSOs (circles)
This more detailed Spitzer study by Carlson et al. of the N113 region extended our census of the YSOs in this region to lower masses as low as 1.5 solar masses from ~4 solar masses based on the galaxy-wide massive YSO searches. These new candidates are shown as circles, whereas the massive YSO candidates found earlier are shown as + signs.
This work in this region and in 8 others in the LMC have doubled our candidate lists for YSOs in the LMC.
Carlson et al. 2012 30

31. Detailed study by Herschel finds YSO candidates (red squares)
JWST simulation region (next slide)
Facilities such as HST can find more evolved candidate YSOs (Stage III) through their H-alpha emission, but to understand how the dust emission evolves, we will need JWST.
Carlson et al. 2012 31

32. JWST imaging tiles on N113 star formation region
JWST will detect solar-like stars with planet forming disks in the LMC!
So one idea is to image these star formation regions using NIRCam and MIRI to investigate the dust content of the lower-mass and more-evolved young stellar objects. The dust remaining in the disks of these more-evolved YSOs is the birth place of planets. It will be interesting to see if these disks have comparable amounts of dust to galactic sources, and hence have the same potential to create planets at low metallicity.
This image shows a potential tiling of the NIRCam fields of view (2.2x2.2 arcminutes) over the N113 region; the MIRI fields of view are slightly smaller (1.9x1.3) and would require a bit more tiling. We have estimated the time it would take to deeply image these fields so that we are sensitive to the dust disk emission from a classical T-Tauri star of 2 solar masses in these images of N113.
The total time for this potential project is 10.3 hours to obtain 6 filters of imaging with NIRCam and MIRI (which includes 1.8 hours for overheads, including 0.5 hrs each for separate slew for MIRI and NIRcam observations). The time for NIRcam is quite quick: only 2 hours; but for MIRI it is 8.3 hours, with 6 of those hours used for the 21 micron filter, which is important for the dust characterization, but the most expensive element.
6 filters: 0.7, 1.77, 1.5, 3.56, 5.6 & 21 microns Limit: 2 solar mass classical, 30 Myr T-Tauri star.
Seale & Meixner
JWST imaging tiles on N113 star formation region
7 March 2013
Hubble Science Briefing – Margaret Meixner 32

33. But it would be useful to get HST data of a field first, as we have for an SMC source
NGC 602
But it would be usefulto get HST data of a field first as we have for an SMC source, highlighted here in yellow.
SAGE SMC team
Gordon et al. 2011
7 March 2013
Hubble Science Briefing – Margaret Meixner 33

34. Spitzer & HST image of NGC 602
This multi-wavelength image of NGC 602 combines 8 bands of data including Spitzer IRAC, and MIPS data and three HST bands of Vi, I and H-alpha.
The circles identify the YSO candidates. The Spitzer angular resolution is poor, giving this image a blurred appearance.
Carlson, et al. 2010
Circles= YSOs
Unclassified
Stage I
Stage I/II
Stage II
MIPS 24µm
IRAC 8.0µm
IRAC 3.6µm, 4.5µm, 5.8µm
Blue= HST Optical
7 March 2013
JWST briefing - Margaret Meixner
Hubble Science Briefing – Margaret Meixner 34 34

35. HST image of NGC 602
This is the HST-only image of NGC 602, showing the amazing clarity of HST. With this HST image, we were able to detect the young solar-mass stars that have planet forming disks, shown here as the faint blue points of light near the bright stars in the center of this star formation region. JWST will have a similar clarity as HST in the infrared bands covered by Spitzer. This greater clarity will enable us to detect the planet forming dust disks around these solar-mass stars at the distance of the LMC for the first time. We will be able to address questions such as: can planets form in lower metallicity environments?
We really need other HST images of the other star forming regions in the LMC and SMC to prepare for JWST. Last Friday (3/1/13) was the HST deadline, and I was working very hard on several proposals to gather such images.
7 March 2013
Hubble Science Briefing – Margaret Meixner 35 35

36. JWST will acquire simultaneous spectral and spatial information
One of the JWST instruments most powerful capability is spectroscopy, which helps us to understand what an object is.
JWST has sophisticated spectrographs known as integral field units, and this picture explains what an integral field unit does…
It gets simultaneous spectral and spatial information.
7 March 2013
Hubble Science Briefing – Margaret Meixner 36

37. Spectroscopy of selected YSOs
JWST NIRSpec & MIRI
Spectroscopy of selected YSOs
Example: N113, a massive young stellar object
JWST will not only find new forming stars, but also allow us to better understand the sources we have already.
Now to really understand the chemistry and dust properties of these circumstellar environments, spectroscopy is essential. JWST has two spectrographs to cover its full wavelength range: NIRSpec & MIRI. The integral field units of both instruments will provide simultaneous spectral and spatial information that is perfect for follow-up of some YSOs selected from these lists of thousands.
For example, let’s look at a potential source in N113. This box shows a 7” field of view of the MIRI IFU, which encompasses the YSO candidate and some surrounding region. This object has 14 solar masses and is embedded in a dusty circumstellar envelope.
Seale, Sewilo, Meixner
7 March 2013
Hubble Science Briefing – Margaret Meixner 37

38. LMC N113: Spitzer spectrum reveals a hot massive star
MIRI
Based on Spitzer IRS spectra of this source, Seale et al classified this YSO with a PE (photoelectron) spectrum, meaning it is dominated by PAH (Polycyclic Aromatic Hydrocarbon) emission and ionic fine-structure emission lines, which mean a high ionization source is located in the object. The spectrum indicates the massive YSO is powering a compact HII region and surrounded by a PDR (photon-dominated region). However, this source is also in a massive star forming region, and some of these emissions may arise from the environment and not the YSO.
The wiggly structure of this spectrum is noise…. And JWST MIRI will get much better spectra with less noise.
MIRI will cover the spectral region shaded in red on this Spitzer IRS spectrum.
The better spatial and spectral resolution of the MIRI IFU will better separate the YSO from its environment to determine if this YSO is really powering these lines. MIRI’s higher spectral resolution will allow to see additional lines from this source, and to get some information on the velocity of the gas surrounding this forming star. Many forming stars have strong bipolar outflows with velocities of 100 km/s.
The spatial resolution is ~0.22” at 7 microns and ~0.66 at 21 microns… imaging spectroscopy is ~0.5”
Seale et al. 2009
7 March 2013
Hubble Science Briefing – Margaret Meixner 38

39. JWST: NIRSpec & MIRI IFU spectroscopy reveals the environmental composition of forming stars
The spectral resolution of MIRI and NIRSpec will be closer to that of the ISO SWS spectrograph, which obtained many interesting spectra of Galactic targets such as this embedded YSO, NGC IRS 9. This ISO SWS spectrum by Whittet et al. revealed many ice features as well as silicate in absorption and shows the type of information we expect to derive for the embedded YSO targets in the Magellanic Clouds. [Silicate is a form of dust.]
Better spectral resolution will allow us to better constrain the chemistry of the ice, which is dominated by water ice, as well as CO and CO2, but also complex organic compounds like methanol and methane.
The shape of the absorption profile changes depending on the precise composition/mixture of ices on dust grains, and a high resolution is required to define this shape. Jets should produce ionized jets of gas at velocities >100 km/s, which may be resolved at this spectral resolution, allowing us to constrain outflow velocities.
For a total time of 3.8 hours, we could obtain full spectral coverage of a single YSO in the Magellanic clouds using both NIRSpec and MIRI.
NIRSpec will be able to complete the shorter wavelengths ranges up to 5 microns.
MIRI will cover the remaining part of the spectrum up to ~28 microns. Combined they will provide a complete census of the ices in these objects.
Will we find the same inventory of ices like NGC 7538 or will they differ in the low metallicity environment?
If you want to do 10 sources, you are talking 38 hours - more than half my time allocation.
ISO SWS spectrum
Whittet et al. 1996
7 March 2013
Hubble Science Briefing – Margaret Meixner 39

40. JWST can measure a spectrum of any source detected with Spitzer
In the LMC, we detected 6 million sources
With Spitzer we measured spectra of only
The faintest sources were unreachable with Spitzer
In the time of 10 seconds to 2 hours, we can measure a spectrum of any source.
7 March 2013
Hubble Science Briefing – Margaret Meixner 40

41. Pursuing SAGE-like studies in nearby Galaxies
With Spitzer, we imaged the Magellanic Clouds with one minute per pointing.
With JWST MIRI, we can detect the same types of forming stars in galaxies as far away as 1 Mpc in one minute per pointing.
The best galaxies should be well studied by Herschel and Spitzer.
the ISM should be mapped in atomic and molecular gas
the stars should be measured and their past well understood
And now I would like to touch briefly on something completely different… Pursuing SAGE like studies in nearby galaxies
7 March 2013
Hubble Science Briefing – Margaret Meixner 41

42. M31: angular size of galaxy: 190’x60’
M31, also known as Andromeda, is just such a galaxy.
M31 is located at a distance of Mpc; the MIRI 7.7 micron MIRI wavelength will have a physical resolution of 1 pc. It’s a BIG galaxy.
Imaging this entire galaxy with JWST, like we did with Spitzer on the LMC and SMC, will not be feasible in a reasonable amount of time.
7 March 2013
Hubble Science Briefing – Margaret Meixner 42

43. M31: 190’ x 2’ strip: total time is ~80 hrs
So let us just state what amount of time it will take to do one row across the center of the galaxy… with the idea that you could sample the different types of regions in M31 with both NIRCam and MIRI.
MIRI imaging in two filters: and 21 microns will take about 60 hours and NIRCam, for four filters will be about 20 hours, for a total of 80 hours.
6 filters: 0.7, 1.77, 1.5, 3.56, 7.7 & 21 microns strip size: 190’x2’
7 March 2013
Hubble Science Briefing – Margaret Meixner 43

44. M33: Mpc, 71’x42’
Or with a similar amount of time, 80 hours, I could map a larger swath of a slightly smaller galaxy, M33 which has many similarities to the LMC, but
No bar and no interacting SMC… 44
7 March 2013
Hubble Science Briefing – Margaret Meixner

45. NGC 6822: Mpc, 16’x14’
For this galaxy, we can map the whole thing with MIRI and NIRCam in 60 hours or less, or 3 days. I could spend my whole guaranteed time on it.
7 March 2013
Hubble Science Briefing – Margaret Meixner 45

46. Summary of Talk
Preparing appropriate target lists for JWST, to launch in 2018
Spitzer and Herschel space observatories discovered thousands of forming stars in the Magellanic Clouds
Hubble has surveyed some fields; need more to prepare for JWST
With JWST I will learn about the nature of the material in forming stars in the Magellanic Clouds:
Do they contain a similar amount of water and organic materials?
Do the solar mass stars have enough circumstellar dust to form planets?
With JWST, I will discover more forming stars in nearby, but more distant galaxies, like M31, M33 and NGC 6822
I am working actively now to prepare appropriate target lists for the JWST observatory which will launch in 2018.
I hope I conveyed my enthusiasm, thoughts and approach of how I will use my guaranteed time on JWST.
Although I am still thinking hard on the exact target lists, I will be basing my observations on prior observations made with Spitzer, Herschel
and HST on the Magellanic Clouds and other nearby galaxies.
7 March 2013
Hubble Science Briefing – Margaret Meixner 46