New clues to jet launching: The inner disks in radio loud quasars may be more stable
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摘要
Jet launching in radio loud(RL) quasars is one of the fundamental problems in astrophysics. Exploring the differences in the inner accretion disk properties between RL and radio quiet(RQ) quasars might yield helpful clues to this puzzle. We previously discovered that the shorter term UV/optical variations of quasars are bluer than the longer term ones, i.e., the so-called timescaledependent color variation. This is consistent with the scheme that the faster variations come from the inner and hotter disk regions,thus providing a useful tool to map the accretion disk which is otherwise unresolvable. In this work we compare the UV/optical variations of RL quasars in SDSS Stripe 82 to those of several RQ samples, including those matched in redshift-luminosity-black hole mass and/or color-magnitude. We find that while both RL and RQ populations appear bluer when they brighten, RL quasars potentially show a weaker/flatter dependence on timescale in their color variation. We further find that while both RL and RQ populations on average show similar variation amplitudes at long timescales, fast variations of RL sources appear weaker/smaller(at timescales of ～25-300 d in the observer's frame), and the difference is more prominent in the g-band than in the r-band.Inhomogeneous disk simulations can qualitatively reproduce these observed differences if the inner accretion disk of RL quasars fluctuates less based on simple toy models. Though the implications are likely model dependent, the discovery points to an interesting diagram that magnetic fields in RL quasars may be prospectively stronger and play a key role in both jet launching and the stabilization of the inner accretion disk.
Jet launching in radio loud(RL) quasars is one of the fundamental problems in astrophysics. Exploring the differences in the inner accretion disk properties between RL and radio quiet(RQ) quasars might yield helpful clues to this puzzle. We previously discovered that the shorter term UV/optical variations of quasars are bluer than the longer term ones, i.e., the so-called timescaledependent color variation. This is consistent with the scheme that the faster variations come from the inner and hotter disk regions,thus providing a useful tool to map the accretion disk which is otherwise unresolvable. In this work we compare the UV/optical variations of RL quasars in SDSS Stripe 82 to those of several RQ samples, including those matched in redshift-luminosity-black hole mass and/or color-magnitude. We find that while both RL and RQ populations appear bluer when they brighten, RL quasars potentially show a weaker/flatter dependence on timescale in their color variation. We further find that while both RL and RQ populations on average show similar variation amplitudes at long timescales, fast variations of RL sources appear weaker/smaller(at timescales of ～25-300 d in the observer's frame), and the difference is more prominent in the g-band than in the r-band.Inhomogeneous disk simulations can qualitatively reproduce these observed differences if the inner accretion disk of RL quasars fluctuates less based on simple toy models. Though the implications are likely model dependent, the discovery points to an interesting diagram that magnetic fields in RL quasars may be prospectively stronger and play a key role in both jet launching and the stabilization of the inner accretion disk.
Jet launching in radio loud(RL) quasars is one of the fundamental problems in astrophysics. Exploring the differences in the inner accretion disk properties between RL and radio quiet(RQ) quasars might yield helpful clues to this puzzle. We previously discovered that the shorter term UV/optical variations of quasars are bluer than the longer term ones, i.e., the so-called timescaledependent color variation. This is consistent with the scheme that the faster variations come from the inner and hotter disk regions,thus providing a useful tool to map the accretion disk which is otherwise unresolvable. In this work we compare the UV/optical variations of RL quasars in SDSS Stripe 82 to those of several RQ samples, including those matched in redshift-luminosity-black hole mass and/or color-magnitude. We find that while both RL and RQ populations appear bluer when they brighten, RL quasars potentially show a weaker/flatter dependence on timescale in their color variation. We further find that while both RL and RQ populations on average show similar variation amplitudes at long timescales, fast variations of RL sources appear weaker/smaller(at timescales of ～25-300 d in the observer's frame), and the difference is more prominent in the g-band than in the r-band.Inhomogeneous disk simulations can qualitatively reproduce these observed differences if the inner accretion disk of RL quasars fluctuates less based on simple toy models. Though the implications are likely model dependent, the discovery points to an interesting diagram that magnetic fields in RL quasars may be prospectively stronger and play a key role in both jet launching and the stabilization of the inner accretion disk.
引文
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1)http://faculty.washington.edu/ivezic/macleod/qso dr7/DB QSO S82.dat.gz
2)https://users.obs.carnegiescience.edu/yshen/BH mass/data/catalogs/dr7 bh Nov19 2013.fits.gz
3 )According to this nomenclature, one may expect a definition like?C(τ)≡[mg(t2)-mr(t2)]-[mg(t1)-mr(t1)]=?mg(τ)-?mr(τ)withτ=t2-t1.This is of course similar to our definition, but?C <(>)0 only indicates an object becomes bluer(redder)without any further information on the change of magnitude. Instead, by adopting the ratio of magnitude difference to define the color variation as what we have done, one can easily get an object becomes bluer when it brightens if 0 4)Note analyzing in the observer’s frame ensures that data in each timescale bin equally come from the same sources for our sample. Contrarily using rest-frame timescale bin would be biased:with the data point at longest rest timescale bin dominated by low-z sources, and vice versa. Note that there are gaps in the observed timescale coverage, the bias would be even more complicated.
5)The stronger variation is due to the fact that in model A and model B, there are less disk zones which contribute to observed emission in the g-and r-bands. More disk zones fluctuating independently would naturally reduce the variation amplitude of the integrated emission[28].
6)Stronger fluctuations would yield bluer mean SEDs as each disk zone is more likely to have higher temperature, while the total emission from the disk averaged over a long time interval remains unchanged[28].
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1)http://faculty.washington.edu/ivezic/macleod/qso dr7/DB QSO S82.dat.gz
2)https://users.obs.carnegiescience.edu/yshen/BH mass/data/catalogs/dr7 bh Nov19 2013.fits.gz
3 )According to this nomenclature, one may expect a definition like?C(τ)≡[mg(t2)-mr(t2)]-[mg(t1)-mr(t1)]=?mg(τ)-?mr(τ)withτ=t2-t1.This is of course similar to our definition, but?C <(>)0 only indicates an object becomes bluer(redder)without any further information on the change of magnitude. Instead, by adopting the ratio of magnitude difference to define the color variation as what we have done, one can easily get an object becomes bluer when it brightens if 0 4)Note analyzing in the observer’s frame ensures that data in each timescale bin equally come from the same sources for our sample. Contrarily using rest-frame timescale bin would be biased:with the data point at longest rest timescale bin dominated by low-z sources, and vice versa. Note that there are gaps in the observed timescale coverage, the bias would be even more complicated.
5)The stronger variation is due to the fact that in model A and model B, there are less disk zones which contribute to observed emission in the g-and r-bands. More disk zones fluctuating independently would naturally reduce the variation amplitude of the integrated emission[28].
6)Stronger fluctuations would yield bluer mean SEDs as each disk zone is more likely to have higher temperature, while the total emission from the disk averaged over a long time interval remains unchanged[28].