Misc,
Rest-frame Optical Properties of Luminous 1.5<z<3.5 Quasars: the Hbeta-OIII Region
(2015)cite arxiv:1512.00005Comment: 10 pages; ApJ in press.
Abstract
We study the rest-frame optical properties of 74 luminous (L_bol=10^46.2-48.2
erg/s), 1.5<z<3.5 broad-line quasars with near-IR (JHK) slit spectroscopy.
Systemic redshifts based on the peak of the OIII5007 line reveal that
redshift estimates from the rest-frame UV broad emission lines (mostly MgII)
are intrinsically uncertain by ~ 200 km/s (measurement errors accounted for).
The overall full-width-at-half-maximum of the narrow OIII line is ~ 1000 km/s
on average. A significant fraction of the total OIII flux (~ 40%) is in a
blueshifted wing component with a median velocity offset of ~ 700 km/s,
indicative of ionized outflows within a few kpc from the nucleus; we do not
find evidence of significant OIII flux beyond ~ 10 kpc in our slit
spectroscopy. The OIII line is noticeably more asymmetric and weaker than
that in typical less luminous low-z quasars. However, when matched in quasar
continuum luminosity, low-z quasars have similar OIII profiles and strengths
as these high-z systems. Therefore the exceptionally large width and
blueshifted wing, and the relatively weak strength of OIII in high-z luminous
quasars are mostly a luminosity effect rather than redshift evolution. The
Hbeta-OIII region of these high-z quasars displays a similar spectral
diversity and Eigenvector 1 correlations with anti-correlated OIII and
optical FeII strengths, as seen in low-z quasars; but the average broad Hbeta
width is larger by 25% than typical low-z quasars, indicating more massive
black holes in these high-z systems. These results highlight the importance of
understanding OIII emission in the general context of quasar parameter space
in order to understand quasar feedback in the form of OIII outflows. The
calibrated one-dimensional near-IR spectra are made publicly available, along
with a composite spectrum.
