1. LINE PROFILES & WAVELENGTHS ACROSS STELLAR SURFACES
Towards the science case for E-ELT HIRES, Cambridge UK, September 2012
KVA
LINE PROFILES & WAVELENGTHS ACROSS STELLAR SURFACES
Dainis Dravins – Lund Observatory, Sweden

2. … where starlight and stellar spectra originate
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)

3. 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)

4. (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)

5. (2) Selecting portions of stellar disk during exoplanet transits
Requires very high S/N in high-resolution spectrometers  
Figure by Hiva Pazira (Lund Observatory)

6. WAVELENGTH SHIFTS OF INTERGALACTIC ABSORPTION LINES
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

7. 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)

8. (Even if timescales might be 100 Myr, rather than solar 10 minutes)
WHENEVER SPECTRAL LINES DO NOT ORIGINATE IN ISOTROPIC TURBULENCE, WAVELENGTH SHIFTS RESULT
… AND THE SAME MUST APPLY TO ALSO INTERGALACTIC CONVECTION, DRIVEN BY HEATING BY AGNs NEAR CLUSTER CENTERS
(Even if timescales might be 100 Myr, rather than solar 10 minutes)
Perseus cluster core in X-rays (Chandra), overlaid with Hα (WYIN). Arc-shaped Hα filaments suggest vortex-like flows.
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)

9. 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 ???