Download High Resolution Spectroscopy of Stars with GMTNIRS

GMT2010: High-resolution Spectroscopy of
Stars with GMTNIRS
David L. Lambert
McDonald Observatory
The University of Texas at Austin
GMT2010
Seoul, Korea
William Herschel (1738-1822)

Discovered the infra-red in 1800
“By placing one thermometer within the
[solar] red rays, separated by a prism, and
another beyond them, he found the
temperature of the outside thermometer
raised by more than that of the inside.”
Humphrey Davy to Davies Giddy
3 July 1800
Introduction
Certain exciting problems in stellar astrophysics demand
high-resolution IR spectra for their solution.
IR advantages include:

Cool stars
- bright in IR
- IR spectra “simpler” than optical
- key signatures in IR: molecules for elemental
and isotopic abundances
- H- opacity minimum at 1.6 µm
- higher dust transparency

Cool gas and dust
- circumstellar envelopes
- prestellar disks
GMTNIRS: J, H, K, L, M (1.15-5.0m) in a single exposure
Introduction
Spectra must be paired with model
atmospheres and atomic/molecular
data


Atomic spectroscopy: generally high-excitation
neutral atomic lines
- Quantitative lab spectroscopy limited
(gf-values for LTE)
- Expect theoretical gf-values to be fairly
reliable
- Astrophysical data (e.g., gf ’s from Sun,
Arcturus, etc.)
Few resonance and low excitation lines.
Therefore - clean spectrum at low metallicity
Introduction
Molecular spectroscopy

Mix of electronic and vibration-rotation transitions

Molecular data generally good but incomplete, but there are few active centers
for lab/theoretical work on astrophysical molecules

Incomplete: stellar column densities » laboratory possibilities (beware of
extrapolation)
: dissociation energies?
: gf-values?
: new molecules (ZrS, TiS)

Can usually predict isotopic wavelength shifts

C, N, O and F including isotopes accessible (in principle)
chemical evolution of stellar systems
stellar evolution, esp. dredge-ups
GMTNIRS performance:

Single exposure: J, H, K, L and M (1.15-5.0m)
at R = λ/∆ λ = 50,000 (JHK) or 100,000 (LM)

Slit
0.085 x 1.3 arc sec with pixel scale of 20 mas

Limiting magnitude
Special (unique) factors: All in one exposure

CNO as tracers of dredge-ups in stars
CO  = 1 in M,  = 2 in K,  = 3 in H
CN Red system in JHK
OH  = 1 in L,  = 2 in H
NH  = 1 in L
C2
Ballik-Ramsay and Phillips in HK
(also HF in K and HCl in L)

Obtain CNO elemental and isotopic abundances

Probe atmospheric dynamics and structure (MOLSPHERE)
Special (unique) factors: All in one exposure

HR4049, a very metal-poor 7500K giant
in a binary with a circumbinary disk:
[Fe/H] = -4.7, but [C, N, O / H]  0.0

Cold CO in absorption at 2.3µm
Lambert, Hinkle & Luck (1988)
Special (unique) factors: All in one exposure
(HR 4049 – continued)

Look for CO at 4.6µm to obtain 12C/13C and 16O/17O ratios
C18O
18CO
CO
C17O
H2O
Hinkle, Brittain & Lambert (2007)
Special (unique) features: Angular resolution
(aperture, AO, pixel scale)

Mass loss by red giant (or all) stars is very poorly understood theoretically
and observationally.

Map circumstellar structure in CO 4.6µm lines
Smith et al. (2009)
Special (unique) features: Angular resolution
(aperture, AO, pixel scale)
HST/WFPC 2
Phoenix slit positions
Smith et al. (2009, AJ, 137, 3558)
Special (unique) features: Angular resolution
(aperture, AO, pixel scale)
Smith et al. (2009)
Special (unique) features: Angular resolution
(aperture, AO, pixel scale)
Velocity-position maps
Betelgeuse
KI 7699 Å
VY CMa
CO 1 – 0 R2 4.64μm
Smith et al. (2009)
Slit 4'' from star
x: 1 pixel = 1.3 km/s
y: 1 pixel = 0''.27
Slit 33'' from star
Plez & Lambert (2002)
Special (unique) features: Angular resolution
(aperture, AO, pixel scale)

Betelgeuse and VY CMa are SN II progenitors

Maps of circumstellar envelopes
clues to mass loss understanding
environment in which SN II explodes

CO has advantages over KI or NaI

GMTNIRS with JHKLM coverage will reveal complete
circumstellar coverage (despite short slit)
- will provide look at innermost regions
- larger number of giants in its grasp
Special (unique) features: Limiting magnitude

LMC, SMC, and just a little further

Dredge-up in red giants
Special (unique) features: Limiting magnitude
Origins of Fluorine
FCNO and internal mixing
Smith et al. (2005)
Smith et al. (2002)
Special (unique) features: Limiting magnitude
K
- 12.5
- 15.5
- 15.5
Smith et al. (2002)
Special (unique) features: Limiting magnitude

Dwarf galaxies beyond the LMC at distance modulus of 18.5
Sculptor 19.5
Sextans
19.7
Carina
20.0
Fornax
20.7

Large surveys of “nearby” systems and stars
- Our globular clusters
- Field stars after GAIA

CNOF
chemical evolution and internal mixing
DO NOT FORGET!

Glorious puzzles remain in stellar astrophysics in this age of cosmology

The GMT and GMTNIRS will help solve many puzzles
“Nature shows us of the lion only the
tail. But there is no doubt in my mind
that the lion belongs with it, even if he
cannot reveal himself to the eye all at
once because of his huge dimensions.”
A. Einstein
Even Einstein observed!
The GMT will reveal the lions!