High Resolution 4'7 m KeckNIRSPEC Spectra of Protostars

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High Resolution 4'7 m KeckNIRSPEC Spectra of Protostars

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High Resolution 4.7 m Keck/NIRSPEC Spectra of Protostars. R=25,000 in 0.43' wide ... cannot observe sources without optical guide star closeby (4 arcmin), i.e. ... – PowerPoint PPT presentation

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Title: High Resolution 4'7 m KeckNIRSPEC Spectra of Protostars

1
High Resolution 4.7 ?m Keck/NIRSPEC Spectra of
Protostars
Adwin Boogert Geoff Blake
Caltech/OVRO Caltech/OVRO
2
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

3
The Atmosphere at 4.7 ?m at R25,000

4
The Atmosphere at 4.7 ?m at R25,000

5
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.

6
R25,000 4.7 ?m Spectra Trace Wide Variety of
Phenomena
7
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.

8
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

9
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)
10
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)
11
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)
12
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)
13
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)

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