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Spectroscopy: High angular resolution with selectable spectral resolution

Spectroscopy: High angular resolution with selectable spectral resolution. (or addressing the scientific problem with the optimal sampling). Motivation:. All too often spectrographs are designed for maximum throughput at one spectral resolution.

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Spectroscopy: High angular resolution with selectable spectral resolution

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  1. Spectroscopy:High angular resolution withselectable spectral resolution (or addressing the scientific problem with the optimal sampling)

  2. Motivation: All too often spectrographs are designed for maximum throughput at one spectral resolution. HST breakthrough: near-diffraction-limited imagery AND access to the UV. Desire: maximum throughput AND high angular resolution AND appropriate resolving power COS: maximum throughput (!), resolving power matched to IGM studies--one internal reflection STIS: high angular resolution (!), selectable resolving power --four internal reflections (+ two for HST aberration) (2 out of 3 ain’t bad… can’t do faster, better, cheaper at the same time either)

  3. Astronomical sources do not form in isolation: QSO’s, AGN’s, nuclear black holes--- form in host galaxies Star formation regions, globular clusters HII regions, propylyds, recently formed stars Protoplanetary disks, Planetary systems Binary stars Stars with massive winds Stars with ejecta: PNs, shells, etc. Breakthroughs come through spatially resolving these complex systems; interactions can be studied in detail

  4. An example of what we have learned that is uniquely possible with HST/STIS: Eta Carinae and the Homunculus Massive star with bipolar ejecta originating in the 19th century. N-rich, C-, O-depleted… Metals abound!

  5. IUE: 10”x20” aperture R=10,000 R=1500 R=1500

  6. HST/GHRS: 0.25” Eta Carinae Weigelt Blobs 0.25” (500AU) distance

  7. HST/STIS: echelle 0.3” (0.060”, R=40,000) June 22, 2003 July 5, 2003

  8. HST/STIS CCD 52”X0.1”, R=8000 June 22, 2003 July 5, 2003 (periastron)

  9. Spatially resolved spectra centered on [Ar III] and [Fe II] (near 7137A) R=1500 R=1500 PA=-28o [Ar III] is blueshifted from 0 to 500 km/s along disk. [Fe II] is centered on -40 km/s PA=+22o

  10. Homunculus internal structures 52x0.2F1 aperture H alphaScattered starlight Shock at edge Spatial: 18” Little Homunculus Ha absorption Sr Filament 0.55” Fiducial 52x0.2F1 Aperture Position He I 6678 A [Ni II] 6666 A Spectral Dispersion ----> External Nebulosity 6490 A 7050 A

  11. What HST/STIS Imaging Spectroscopy has discovered about Eta Carinae: • Little Homunculus-- a bipolar shell within the Homunculus, ejected in the 1890s, 50 years after the massive event. • Strontium filament-- a metal-ionized region (7-8 eV photons), not H II region, in the skirt… evidence of very peculiar abundances caused by chemistry, not nuclear processes????… Ti II emission region… Ti/Ni ~40X solar! • Homunculus shell structure of metals and molecules leading to abundance analysis of ejecta. Potential leading to understanding of how dust can form in gas depleted 50-fold of both C and O. • First identification of IS vanadium, scandium, strontium • Characterization and modeling of 760K and 6400K photoexcited gases! • Tracking of photo-excitation and ionization changes in ejecta across binary period. • Identification of the He I emission originating in the primary massive wind, yet excited by the hot, lower mass secondary • Resolution of the massive binary wind structure leading to 3-D modeling of wind-wind interaction… including clumping Combined with CHANDRA: characterization of the wind-wind interaction and binary VLT/UVES: abundances of metals and diatomic molecules VLTI/AMBER: measure of the He I wind-wind structure of binary system Models to be tested across the 2009.0 periastron passage.

  12. Future Spectroscopy: We must take full advantage of spatial resolution along with appropriate spectral resolution where possible-- (increased detail can lead to greatly expanded insights). Two basic designs: Maximize throughput at appropriate resolution at expense of spatial resolution Optimize spatial and spectral resolution requires more optical surfaces, at the expense of throughput. Can we bring both designs together? Sampling: (science tradeoffs must be addressed!) Long slit Integral Field Aperture selectors

  13. Acknowledgement: • NASA/GSFC for sponsoring the decades of UV spectroscopic development… • will options exist for future development? • STScI for support through multiple guest observer programs (approaching one paper per allocated orbit) • Eta Lunch Bunch and the extended Eta Car teams

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