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Towards the science case for E-ELT HIRES, Cambridge UK, September 2012
KVA
LINE PROFILES & WAVELENGTHS
ACROSS STELLAR SURFACES
Dainis Dravins – Lund Observatory, Sweden
www.astro.lu.se/~dainis
STELLAR SURFACES
… where starlight and stellar spectra originate
Simulations feasible for widely different stars
But … any precise physical conclusion
depends on the reliability of modeling
(metallicity, magnetic activity, gravitational
redshift, center-to-limb wavelength changes).
How does one verify/falsify 3-D simulations
(except for the spatially resolved Sun) ?
High-resolution spectroscopy across
spatially resolved stellar disks !
Granulation on a 12,000 K white dwarf (top) and a 3,800 K red
giant. Areas differ by enormous factors: 7x7 km2 for the white
dwarf, and 23x23 RSun2 for the giant. (H.-G. Ludwig, Heidelberg)
LINE PROFILES FROM 3-D HYDRODYNAMIC SIMULATIONS
Model predictions insensitive to modest spatial smearing
Spatially averaged
line profiles from
20 timesteps, and
temporal averages.
 = 620 nm
 = 3 eV
5 line strengths
GIANT STAR
Teff= 5000 K
log g [cgs] = 2.5
(approx. K0 III)
Stellar disk center;
µ = cos  = 1.0
(Models by Hans-Günter Ludwig, Landessternwarte Heidelberg)
(1) Spatially resolved spectroscopy with E-ELT
Requires adaptive optics with integral-field unit
Left: Hydrodynamic simulation of the supergiant Betelgeuse (B.Freytag)
Right: Betelgeuse imaged with ESO’s 8.2 m VLT (Kervella et al., A&A, 504, 115)
Top right: 40-m E-ELT diffraction limits at 550 nm & 1.04 μm.
Figure by Hiva Pazira (Lund Observatory)
(2) Selecting portions of stellar disk during
exoplanet transits
Requires very high S/N in high-resolution spectrometers

Figure by Hiva Pazira (Lund Observatory)

Towards the science case for E-ELT HIRES, Cambridge UK, September 2012
KVA
HIRES quasar spectrum (A.S.Cowie, Univ.of Hawaii)
WAVELENGTH SHIFTS OF
INTERGALACTIC ABSORPTION LINES
Dainis Dravins – Lund Observatory, Sweden
www.astro.lu.se/~dainis
WHENEVER SPECTRAL LINES
DO NOT ORIGINATE IN
ISOTROPIC TURBULENCE,
WAVELENGTH SHIFTS RESULT
Observed solar granulation
(Swedish Solar Telescope on La Palma; G.Scharmer & M.G.Löfdahl)
SOLAR MODEL
Synthetic line profiles showing convective
wavelength shifts originating in granulation
 = 620 nm;  = 1, 3, 5 eV; 5 line strengths
Teff= 5700 K; log g [cgs] = 4.4; G2 V
Solar disk center; µ = cos  = 1.0
(Models by Hans-Günter Ludwig, Landessternwarte Heidelberg)
WHENEVER SPECTRAL LINES
DO NOT ORIGINATE IN
ISOTROPIC TURBULENCE,
WAVELENGTH SHIFTS RESULT
… AND THE SAME MUST APPLY
TO ALSO INTERGALACTIC
Perseus cluster core in X-rays (Chandra), overlaid with Hα
(WYIN). Arc-shaped Hα filaments suggest vortex-like flows.
CONVECTION, DRIVEN BY
HEATING BY AGNs NEAR
CLUSTER CENTERS
Density slices at three times. Viscosity stabilizes the bubble,
allowing a flattened buoyant “cap” to form. X-ray brightness
and inferred velocity field in Per-A can be reproduced.
(Reynolds et al.: Buoyant radio-lobes in a viscous intracluster
medium, MNRAS 357, 242, 2005)
(Even if timescales might be 100
Myr, rather than solar 10 minutes)
INTERGALACTIC LINE ASYMMETRIES AND SHIFTS:
ANALOGIES AND DIFFERENCES TO STELLAR CONVECTION:
• Plausible amount: 1 % of “general” line broadening = 0.5 – 1 km/s ?
• Mapping 3-D structure from different shifts in different lines !
• Need line synthesis from 3-D hydrodynamic models !
• Lines closer to cluster centers gravitationally more redshifted
• Mapping depth structure from multiple line components ?
• Probably useful to have resolving power approaching 1,000,000 ??
• Resolving lateral structure from secular time changes ???