1. SOFIA and the ISM of Galaxies Xander Tielens & Jessie Dotson Presented by Eric Becklin

2. Process Ideas on key/killer science from small science team well embedded in Spitzer and Herschel science and cognizant of SOFIA A local SOFIA team will translate these science ideas into actual program and address issues such as feasibility Text will be written by Xander with support from the local SOFIA team and iterated upon by the science team

3. Input Xander Tielens  –see JWST review Magaret Meixner: Lifecycle of the ISM  –presented her views to the SOFIA science vision team on June 18, 2008 –See presentation –SOFIA team is working out some numbers on this Bruce Draine: interstellar dust and PAHs  – has provided written science input Lou Allamandola: Molecular complexity  –Has provided written input Mark Wolfire: The energetics of the ISM  –Has provided input through one-on-one discussions –See 2020 presentation –Still to be worked out Tom Roellig: Supernovae and the ISM –Has provided input through one-on-one discussion –Will provide short write up Jessie Dotson: Interstellar magnetic fields –Will provide input Dan Jaffe & Angela Speck and the “white” team:  –science input through their white paper –To be updated

4. SOFIA’s Spectroscopic Niche Instruments characteristics: –Wide wavelength coverage: ~2  m — 0.5 mm –Wide range of spectral resolution: ~10 2 — 10 6 –Large Field of View: upto square arcminutes Dust and PAHs & ionic, atomic, and molecular lines –Composition/molecular inventory –Physical conditions –Kinematics “large scale” spectroscopic mapping of regions of high surface brightness

5. Draft Outline The dusty Universe –Tracing the Universe with dust (Characteristics of dust in different environments) –Tracing the Universe with PAHs (Characteristics of PAHs in different environments) –Searching for the ‘grandPAH’ The warm and dense Universe –Tracing the radiative interaction of massive stars with their environment (Photodissociation regions and the heating of interstellar gas) –Tracing the mechanical interaction of massive stars with the dense ISM (SNR and molecular clouds; TBC) The structure of the ISM –SNe and the elemental enrichment of the ISM (TBC) –CII and the cooling of the ISM –The large scale structure of the galactic magnetic fields (TBC)

6. Tracing the Universe with Dust What are the spectroscopic and physical differences between ‘high- mass’ and ‘low-mass’ stardust ? How important are high mass stars in the dust budget of galaxies ? How does this depend on the characteristics of the environment ? A coherent program that addresses these issues will allow us to develop the spectroscopic signatures of dust into diagnostic tools for the origin of dust and the lifecycle of the interstellar medium of galaxies. While Spitzer will provide an inventory of the low metallicity environments of the LMC/SMC and JWST can probe galaxies in the local group, only SOFIA can study the dust budget of the Milky Way Measure the mid-IR spectra of a broad sample of stellar sources and transform these to mass loss rates using GAIA distances

7. Tracing the Universe with PAHs Variations in the PAH spectra provide handle on the star formation rate and on the physical conditions in these extreme environments SOFIA will determine the characteristics of the PAH spectrum in a sample of well-studied galactic sources specifically designed to address the dependence on density, radiation field characteristics, metallicity, & dust characteristics Only SOFIA has the wavelength coverage to measure the mid-IR PAH spectrum and the far-IR gas diagnostics to determine the physical conditions of the region Measure the PAH emission and CII/OI/high-J CO spectra of broad sample of photodissociation regions and ‘calibrate’ the PAH characteristics to the star formation rate and the physical conditions M82

8. Searching for the ‘grandPAH’ The incredibly rich far-IR spectrum of PAHs Low frequency modes are highly molecule specific and provide unique signatures for identification purposes Detailed spectrum depends on: –Interstellar PAH family (here 40 small PAHs are added together) –Rotational constants Lowest frequency modes will decouple and show PQR structure (key aid for identification, if resolved) SOFIA HerschelSpitzer JWST

9. Searching for the ‘grandPAH’ The incredibly rich far-IR spectrum of PAHs SOFIA can probe full IR spectral range with a new far-IR spectrometer at a spectral resolution of ~300 Sources are bright but line-to-continuum will be challenging (continuum = dashed line) Other observatories either do not cover full wavelength region or do not have a suitable spectrometer to cover a wide wavelength region at moderate resolution SOFIA HerschelSpitzer JWST

10. Tracing the radiative interaction of massive stars with their environment The CII line intensity decreases with the characteristics of the galaxy Malhotra et al, 2001, ApJ, 561, 766 SOFIA will determine the spectral characteristics of PDRs in a sample of well- studied galactic sources specifically designed to address the dependence on density, radiation field characteristics, metallicity, & dust characteristics SOFIA has a distinct advantage in mapping nearby bright PDRs in the far-IR gas diagnostics to determine the physical conditions of the region

11. Timeline Updated timeline from early June Input from science team by end of June –Much has been received but still needs further analysis Analysis by SOFIA team by end of July –FIFI-LS on SOFIA beats Herschel in mapping extended regions of high surface brightness –TBC: feasibility of spectral imaging in PAH features –TBC: far-IR polarimetry of spiral structure in galaxies Text by end of September Started writing draft Iteration by end of October Translation into powerpoint presentation by end of November

12. Summary SOFIA is uniquely suited to study the ISM of galaxies ! JWST & ALMA have been specifically designed to address key questions on the origin and evolution of the far Universe. However, SOFIA will be essential to understand the ‘answers’ observed !