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SCOWL - taking OWL into the sub-mm

SCOWL - taking OWL into the sub-mm. W.Dent, E.Atad, D.Gostick, M.Ellis, I.Egan, W.Holland UKATC R.Siebenmorgen ESO. What is SCOWL? Submm science – the birth of planets, stars and galaxies SCOWL capabilities. SCOWL. A widefield Submm Camera for OWL

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SCOWL - taking OWL into the sub-mm

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  1. SCOWL- taking OWL into the sub-mm W.Dent, E.Atad, D.Gostick, M.Ellis, I.Egan, W.Holland UKATC R.Siebenmorgen ESO What is SCOWL? Submm science – the birth of planets, stars and galaxies SCOWL capabilities

  2. SCOWL • A widefield Submm Camera for OWL • takes advantage of excellent site, large collecting area, exquisite surface • 20x more sensitive • 107x faster at wide-field mapping • complementary to ALMA → opens up new areas of astronomy → maximise science return for OWL

  3. Submm “windows” 850μm 450μm 350μm good site (0.5mm pwv) ‘poor’ site (1mm pwv)

  4. Science in the submm • Submm emission is from cool dust & gas (20-100K) • Formation processes (planets, stars, galaxies) are hidden in clouds with >>100 magnitudes of optical extinction - we can’t see it • But dust clouds become transparent at longer wavelengths - nothing is hidden in the submm!

  5. Key astronomy with SCOWL Solar system: • distant KBOs Galactic: • extreme-mass protostars: the lowest and highest masses • what makes a cloud form into stars? “pre-protostars” • planet-forming discs: how do planets form? • debris discs Extragalactic: • cold dark matter in galaxies • galaxy formation in the early Universe • galaxy cluster formation • resolving the submm background

  6. Key Science (1): Kuiper Belt Objects • What is the distant KBO population? Size distribution? • How many “Sednas” are there beyond 30au? • how far does the Solar System extend? • how did distant KBOs form? requirements: max mass sensitivity for black-body emission multiple wavelengths min confusion limit otherwise spatial resolution not critical

  7. Key Science (2): debris discs photosphere Fomalhaut reprocessed starlight 1000 100 10 1um

  8. Debris discs Debris dust caused by asteroid collisions Clumps in discs are resonances with unseen planets: only seen in submm Disc sizes ~100au, imply distant planets, asteroids dust mass Solar system

  9. Debris discs • does the mass depend on age, spectral type, location? • is there a continuous distribution down to the Solar system mass? • is our Solar System unique in having low dust mass? (interval between catastrophic collisions) • how is debris (and hence asteroids) related to the presence of planets? • A complete inventory of the constituents of exo-planetary systems requirements: dust mass sensitivity >100x better than existing 2x2 arcmin fov resolution ~1 arcsec “sidelobe” level <1%

  10. Microwave Background Photospheric light from stars Key Science (3): early galaxy formation Photospheric light reprocessed by dust in Galaxies

  11. Early galaxy & star formation submm samples the star formation rate Peak of SED: z=0.7 170 micron z=1.5 250 micron z=2.5 350 micron z=4 500 micron star formation rate vs. redshift SCOWL

  12. Galaxy & early star formation • Galaxy formation: hierarchical? • Star formation history: burst or gradual? SFR to z=20 • how does CMB structure and galaxy formation relate? • how does IMF change with z? requirements: >few deg2 mapping resolution ~1 arcsec high s:n detection of 0.1mJy @850um at least 2 photometric bands (850,450um)

  13. SCOWL specificationsand observatory requirements • beam size ~1” (100m) • 3 wavebands simultaneously (850, 450 & 350μm) • 450μm operation required (good submm site) • field of view at least 2x2 arcmin • Nyquist sampled pixels: >20,000 per band • must be background limited => coverage by warm emitters <5% • sidelobes <1% • available at least ~5% of time, or hitchhiker

  14. SCOWL design Based on SCUBA-2: 70, 4, 1 & 0.1K stages; ~4 tonnes

  15. SCOWL design cryostat TES detector array unit (x4 for SCOWL)

  16. SCOWL design Detector options:

  17. The capabilities of SCOWL (1) 20x more sensitive to a given mass of dust

  18. The capabilities of SCOWL (2) λ(μm) 850 450 350 850 450 350 ALMA (compact) SCOWL >107x faster than ALMA at large-scale mapping

  19. SCOWL and ALMA complement each other

  20. SCOWL - taking OWL into the submm • submm is critical for understanding formation of Planets, Stars, Galaxies • key science required to meet the aims of OWL SCOWL • large-format submm camera • 20x more sensitive than any other facility • makes large-scale mapping projects feasible • enables new science, extends scientific return on OWL investment but : • OWL site should be very dry • OWL should be 100m

  21. tip-tilt in the submm • submm seeing dominated by water vapour variations • seeing limit ~1 arcsec (can be worse) • diffraction limit 2”(850) to 0.9”(350) differential water vapour meter > tip-tilt correction

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