TY - JOUR
T1 - Spectral evolution in high redshift quasars from the final Baryon Oscillation Spectroscopic Survey sample
AU - Jensen, Trey W.
AU - Vivek, M.
AU - Dawson, Kyle S.
AU - Anderson, Scott F.
AU - Bautista, Julian
AU - Bizyaev, Dmitry
AU - Brandt, William N.
AU - Brownstein, Joel R.
AU - Green, Paul
AU - Harris, David W.
AU - Kamble, Vikrant
AU - McGreer, Ian D.
AU - Merloni, Andrea
AU - Myers, Adam
AU - Oravetz, Daniel
AU - Pan, Kaike
AU - Pâris, Isabelle
AU - Schneider, Donald P.
AU - Simmons, Audrey
AU - Suzuki, Nao
PY - 2016/12/19
Y1 - 2016/12/19
N2 - We report on the diversity in quasar spectra from the Baryon Oscillation Spectroscopic Survey. After filtering the spectra to mitigate selection effects and Malmquist bias associated with a nearly flux-limited sample, we create high signal-to-noise ratio composite spectra from 58,656 quasars (2.1 ≤ z ≤ 3.5), binned by luminosity, spectral index, and redshift. With these composite spectra, we confirm the traditional Baldwin effect (BE, i.e., the anticorrelation of C IV equivalent width (EW) and luminosity) that follows the relation Wλ ∝ Lβw with slope βw = -0.35 ± 0.004, -0.35 ± 0.005, and -0.41 ± 0.005 for z = 2.25, 2.46, and 2.84, respectively. In addition to the redshift evolution in the slope of the BE, we find redshift evolution in average quasar spectral features at fixed luminosity. The spectroscopic signature of the redshift evolution is correlated at 98% with the signature of varying luminosity, indicating that they arise from the same physical mechanism. At a fixed luminosity, the average C IV FWHM decreases with increasing redshift and is anti-correlated with C IV EW. The spectroscopic signature associated with C IV FWHM suggests that the trends in luminosity and redshift are likely caused by a superposition of effects that are related to black hole mass and Eddington ratio. The redshift evolution is the consequence of a changing balance between these two quantities as quasars evolve toward a population with lower typical accretion rates at a given black hole mass.
AB - We report on the diversity in quasar spectra from the Baryon Oscillation Spectroscopic Survey. After filtering the spectra to mitigate selection effects and Malmquist bias associated with a nearly flux-limited sample, we create high signal-to-noise ratio composite spectra from 58,656 quasars (2.1 ≤ z ≤ 3.5), binned by luminosity, spectral index, and redshift. With these composite spectra, we confirm the traditional Baldwin effect (BE, i.e., the anticorrelation of C IV equivalent width (EW) and luminosity) that follows the relation Wλ ∝ Lβw with slope βw = -0.35 ± 0.004, -0.35 ± 0.005, and -0.41 ± 0.005 for z = 2.25, 2.46, and 2.84, respectively. In addition to the redshift evolution in the slope of the BE, we find redshift evolution in average quasar spectral features at fixed luminosity. The spectroscopic signature of the redshift evolution is correlated at 98% with the signature of varying luminosity, indicating that they arise from the same physical mechanism. At a fixed luminosity, the average C IV FWHM decreases with increasing redshift and is anti-correlated with C IV EW. The spectroscopic signature associated with C IV FWHM suggests that the trends in luminosity and redshift are likely caused by a superposition of effects that are related to black hole mass and Eddington ratio. The redshift evolution is the consequence of a changing balance between these two quantities as quasars evolve toward a population with lower typical accretion rates at a given black hole mass.
KW - black hole physics
KW - galaxies: active
KW - quasars: emission lines
KW - quasars: general
KW - surveys
UR - http://www.scopus.com/inward/record.url?scp=85007565809&partnerID=8YFLogxK
U2 - 10.3847/1538-4357/833/2/199
DO - 10.3847/1538-4357/833/2/199
M3 - Article
AN - SCOPUS:85007565809
SN - 0004-637X
VL - 833
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
M1 - 199
ER -