[seminar] Astro Journal Club on 18 March

[Oskari Miettinen]

Dear all,

The Astro Journal Club will be held on Wednesday at 10:15 in the seminar
room F-201 of the Physics Department. This time we will discuss about the
spectral energy distribution of the highest-redshift quasar known to date.

Presenter: Oskari Miettinen
Paper title: The spectral energy distribution of the redshift 7.1 quasar
ULAS J1120+0641
Authors: Barnett, R., Warren, S. J., Banerji, M., et al.

Abstract:
We present new observations of the highest-redshift quasar known, ULAS
J1120+0641, redshift
z= 7.084, obtained in the optical, at near-, mid-, and far-infrared
wavelengths, and in the sub-mm. We combine these results with published
X-ray and radio observations to create the multiwavelength spectral energy
distribution (SED), with the goals of measuring the bolometric luminosity
Lbol, and quantifying the respective contributions from the AGN and star
formation. We find three components are needed to fit the data over the
wavelength range 0.12-1000 micron: the unobscured quasar accretion disk
and broad-line region, a dusty clumpy AGN torus, and a cool 47K modified
black body to characterise star formation. Despite the low signal-to-noise
ratio of the new long-wavelength data, the normalisation of any dusty
torus model is constrained within +/-40%. We measure a bolometric
luminosity Lbol = 2.6 +/- 0.6 x 1e47 erg s-1 = 6.7 +/- 1.6 x 1e13 Lsun, to
which the three components contribute 31%, 32%, 3%, respectively, with the
remainder provided by the extreme UV < 0.12 micron. We tabulate the
best-fit model SED. We use local scaling relations to estimate a star
formation rate (SFR) in the range 60-270 Msun/yr from the [C II] line
luminosity and the 158 micron continuum luminosity. An analysis of the
equivalent widths of the [C II] line in a sample of z> 5.7 quasars
suggests that these indicators are promising tools for estimating the SFR
in high-redshift quasars in general. At the time observed the black hole
was growing in mass more than 100 times faster than the stellar bulge,
relative to the mass ratio measured in the local universe, i.e. compared
to MBH/Mbulge = 1.4 x 1e-3, for ULAS J1120+0641 we measure
d(MBH)/dt/d(Mbulge)/dt = 0.2.

Link to the paper: http://adsabs.harvard.edu/abs/2015A%26A...575A..31B

Hope to see you all on Wednesday!

Best regards,
Oskari