Annual Report 2011 Max Planck Institute for Astronomy

30 II. Highlights
II.3 In what Galaxies do Black Holes live in the Early Universe?
Using state-of-the-art technology and sophisticated
data analysis tools, a team from MPIA has developed a
new and powerful technique to directly determine the
mass of a galaxy hosting an active supermassive central
black hole at a distance of nearly 9 billion light-years
from Earth. This pioneering method promises a new
approach for studying the co-evolution of galaxies and
their central black holes, which typically relies on mass
determinations.
One of the most intriguing developments in astronomy
over the last few decades is the realization that not only
do most galaxies contain central black holes of gigantic
size, but also that the mass of these central black holes
are directly related to the mass of their host galaxies.
These scaling relations with the black hole mass have
been found to exist with the galaxy’s stellar or dynamical
bulge mass, total luminosity and stellar velocity dispersion.
It has recently been realized that these correlations
are expected as a consequence of the current standard
model of galaxy evolution, the so-called hierarchical
model, as astronomers from MPIA have shown (Jahnke
& Macciò 2011, ApJ, 734, 92). In this standard model of
galaxy formation galaxies evolve and grow by ingesting
smaller galaxies, or through mergers with galaxies of
comparable size. As a a consequence of this hierarchical
formation, the individual relations between bulge and
black hole mass are averaged out, creating a nearly universal
ratio between the two properties in every galaxy.
One of the most robust methods to study how galaxies
and black holes evolve relative to each other is to trace
these scaling relations through cosmic time. This can
pixel
60
50
40
30
20
10
a
–21.4
log (F(Ha) / (W/m
–21
2 ))
–20.6
0.5
10
E
20 30 40 50 60
pixel
N
b
0.5
10
L(Ha) [10 42 ]
0.4
0.3
0.2
0.1
0
–0.1
620
640 660 680 700 720
Wavelength [nm]
Fig. II.3.1: Spectrum around Hα for the quasar SDSS
J090543.56+043347.3, centered on the active nucleus. From
the combination of width (red arrow) and luminosity (integral
above the zero level between the blue lines) of the Hα line
the black hole mass can be inferred (Greene & Ho 2005,
ApJ, 630, 122). The use of Hα for this purpose reduces the
systematic uncertainties present in the prior estimates using
the MgII line.
Fig. II.3.2: SDSS J090543.56+043347.3: (a) Extracted emission
line flux distribution, (b) Hα line width and (c) resulting
velocity field, in all cases after removal of the bright nucleus,
overlaid in contours.
50
Ha line width [km/s]
110 170
E
20 30 40 50 60
pixel
N
c
V [km/s]
–150 50
0.5
10
E
250
20 30 40 50 60
pixel
N
Credit: Katherine J. Inskip
Credit: Katherine J. Inskip