http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
BROAD H<i>β</i>EMISSION-LINE VARIABILITY IN A SAMPLE OF 102 LOCAL ACTIVE GALAXIES
Runco, Jordan N.,Cosens, Maren,Bennert, Vardha N.,Scott, Bryan,Komossa, S.,Malkan, Matthew A.,Lazarova, Mariana S.,Auger, Matthew W.,Treu, Tommaso,Park, Daeseong American Astronomical Society 2016 The Astrophysical journal Vol.821 No.1
<P>A sample of 102 local (0.02 <= z <= 0.1) Seyfert galaxies with black hole masses M-BH > 10(7)M(circle dot) was selected from the Sloan Digital Sky Survey (SDSS) and observed using the Keck 10 m telescope to study the scaling relations between M-BH and host galaxy properties. We study profile changes of the broad H beta emission line within the three to nine year time frame between the two sets of spectra. The variability of the broad H beta emission line is of particular interest, not only because it is used to estimate M-BH, but also because its strength and width are used to classify Seyfert galaxies into different types. At least some form of broad-line variability (in either width or flux) is observed in the majority (similar to 66%) of the objects, resulting in a Seyfert-type change for similar to 38% of the objects, likely driven by variable accretion and/or obscuration. The broad H beta line virtually disappears in 3/102 (similar to 3%) extreme cases. We discuss potential causes for these changing look active galactic nuclei. While similar dramatic transitions have previously been reported in the literature, either on a case-by-case basis or in larger samples focusing on quasars at higher redshifts, our study provides statistical information on the frequency of H beta line variability in a sample of low-redshift Seyfert galaxies.</P>
Bennert, Vardha N.,Treu, Tommaso,Auger, Matthew W.,Cosens, Maren,Park, Daeseong,Rosen, Rebecca,Harris, Chelsea E.,Malkan, Matthew A.,Woo, Jong-Hak IOP Publishing 2015 The Astrophysical journal Vol.809 No.1
<P>We create a baseline of the black hole (BH) mass (M-BH)-stellar-velocity dispersion (sigma) relation for active galaxies, using a sample of 66 local (0.02 < z < 0.09) Seyfert-1 galaxies, selected from the Sloan Digital Sky Survey (SDSS). Analysis of SDSS images yields AGN luminosities free of host-galaxy contamination, and morphological classification. 51/66 galaxies have spiral morphology. Out of these, 28 bulges have Sersic index n < 2 and are considered candidate pseudo-bulges, with eight being definite pseudo-bulges based on multiple classification criteria met. Only 4/66 galaxies show signs of interaction/merging. High signal-to-noise ratio Keck spectra provide the width of the broad H beta emission line free of Fe II emission and stellar absorption. AGN luminosity and H beta line widths are used to estimate M-BH. The Keck-based spatially resolved kinematics is used to determine stellar-velocity dispersion within the spheroid effective radius (sigma(spat,reff)). We find that sigma can vary on average by up to 40% across definitions commonly used in the literature, emphasizing the importance of using self-consistent definitions in comparisons and evolutionary studies. The M-BH-sigma relation for our Seyfert-1 galaxy sample has the same intercept and scatter as that of reverberation-mapped AGNs as well as that of quiescent galaxies, consistent with the hypothesis that our single epoch M-BH estimator and sample selection function do not introduce significant biases. Barred galaxies, merging galaxies, and those hosting pseudo-bulges do not represent outliers in the M-BH-sigma relation. This is in contrast with previous work, although no firm conclusion can be drawn on this matter due to the small sample size and limited resolution of the SDSS images.</P>