High Resolution 4'7 m KeckNIRSPEC Spectra of Protostars

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High Resolution 4.7 ?m Keck/NIRSPEC Spectra of
Protostars
Adwin Boogert Geoff Blake
Caltech/OVRO Caltech/OVRO
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NIRSPEC at Keck II

• R25,000 in 0.43 wide slit ?v12 km/s at 4.7 ?m
• M band sensitivity S/N50 at M5.6 magn in 900
  seconds on source
• 3 partial orders on 10242 array.
• Instantaneous coverage 0.07 ?m per order.
• 4 settings needed to cover best part of
  atmospheric M band
• NIRSPEC is powerful instrument for M band
  observations, although it is not optimized for M
  band

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The Atmosphere at 4.7 ?m at R25,000

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The Atmosphere at 4.7 ?m at R25,000

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Source Sample

• Program start-up involved well known Herbig AeBe,
  T Tauri and Class I protostars in multiple
  settings.
• Efficiency and success rate increase
  significantly with larger sample of sources in
  only one setting, initially. Follow-up in other
  settings on most interesting sources.
• In second stage of program a flux limited sample
  drawn from the SIRTF/IRS c2d source list Mlt7
  magn, Dec gt -30 degrees.
• Differences with VLT/ISAAC
• NIRSPEC only Dec gt -30, so no R CrA, Cham, Lupus
  (
• NIRSPEC has higher spectral resolution (25000 vs.
  10000)
• Keck/NIRSPEC cannot observe sources without
  optical guide star closeby (4 arcmin), i.e.
  cannot do most embedded 'icy' sources. Bias
  toward more evolved sources with emission lines.

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R25,000 4.7 ?m Spectra Trace Wide Variety of
Phenomena
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R25,000 4.7 ?m Spectra c2d/IRS YSOs

• Status
• 2.5 good nights in spring/summer 2002 in which
  about 25 sources done.
• Another run next week.

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L1489 IRS with Keck/NIRSPEC

• Inventory
• deep 12CO gas absorption lines with red shifted
  wings
• gas phase 13CO
• gas phase C18O
• complex CO ice band
• no strong XCN
• no strong H I Pf ?
• no CO emission

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The Shrinking Disk of L1489 IRS
HCO 3-2 OVRO/BIMA

• Class I SED
• L3.7 Lsun
• Mdisk0.02 Msun
• Large flattened structure in millimeter
  continuumline emission.
• Continuum and lines cannot be fitted with same
  inside-out collapse model
• Instead, velocity structure indicates large 2000
  AU radius close to edge-on disk, in almost
  Keplerian rotation with infall component.

Hogerheijde, ApJ 553, 618 (2001)
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The Shrinking Disk of L1489 IRS
HCO 3-2 OVRO/BIMA

• L1489 IRS disk characterized by power law
  flared disk model
• Fits lines, continuum and velocity structure.
• T 34(R/1000AU)-0.4 K
• n n0(R/1000AU)-1.5.exp(-z2/h2) kg/cm3
• h R/2 flaring
• Vin 1.3(R/100AU)-0.5 km/s
  in addition to Keplerian rotation around
  0.65 Msun central star
• L1489 IRS represents short lived (lt20,000 yr)
  transition phase in which disk shrinks to few 100
  AU TTauri disk?

Hogerheijde, ApJ 553, 618 (2001)
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The Shrinking Disk of L1489 IRS!
CO Keck/NIRSPEC

• To first order, 4.7 ?m CO spectra confirm
  infalling motion of disk.
• CO lines confine T and n structure of disk.
• Introduce power law for density along pencil
  absorption beam
• n(l) n0(l/1000 AU)-p

Boogert et al., ApJ 568,761 (2002)
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The Shrinking Disk of L1489 IRS!
CO Keck/NIRSPEC

• To first order, 4.7 ?m CO spectra confirm
  infalling motion of disk.
• CO lines confine T and n structure of disk.
• Introduce power law for density along pencil
  absorption beam
• n(l) n0(l/1000 AU)-p
• we find p0.55
• scale height increases more than linear, very
  flared disk
• Too much warm gas at high velocity

Boogert et al., ApJ 568,761 (2002)
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The Shrinking Disk of L1489 IRS!
CO Keck/NIRSPEC

• Modelled depth in better agreement if 50 of
  observed continuum from scattered light, not
  absorbed by CO.
• Still too much warm gas at high velocity.
• Only partial collapse of disk, e.g. a surface
  layer and outer parts?
• Supported by low luminosity and weakness of H I
  emission lines (weak accretion shock)
• 0.02 Msun disk collapse in 20000 yr gives
  Macc10-6 Msun/yr or Lacc7 Lsun, while L3.7
  Lsun.

Boogert et al., ApJ 568,761 (2002)