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— Joint probability density for the ratio of the accretion disk sizes in observed-frame r-band and g-band (rs,r/rs,g) for SBS 0909. The vertical line highlights the location of rs,r/rs,g = 1. The distribution is very wide, reflecting the poor constraints we are able to place on the observed-frame g-band accretion disk size. The median and 1σ values for the size ratio distribution are log rs,r/rs,g = 0.5 +0.9 −1.0 , which are larger but not statistically inconsistent with the r/g-band size ratio expected for a thin accretion disk.
Source publication
We present three complete seasons and two half-seasons of SDSS r-band
photometry of the gravitationally lensed quasar SBS 0909+532 from the U.S.
Naval Observatory, as well as two seasons each of SDSS g-band and r-band
monitoring from the Liverpool Robotic Telescope. Using Monte Carlo simulations
to simultaneously measure the system's time delay and...
Context in source publication
Context 1
... our r-band disk size, our g-band result is notably smaller than the scaled result from M11, al- though the significance of the discrepancy is low due to the large uncertainties. We also calculate the probabil- ity density for the ratio of the r-and g-band disk sizes, which we show in Figure 7. The distribution is very broad, with a median value and 1σ confidence level of log r s,r /r s,g = 0.5 +0.9 −1.0 . ...
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Citations
... The (unknown) average mass of a lens galaxy star must be assumed, and the singleepoch technique is only appropriate for short time-delay systems because in systems with longer time delays, differentiating between the variability intrinsic to the quasar source itself and variability from extrinsic effects such as microlensing is not possible. The multiepoch technique requires the collection and analysis of many-season lightcurves, modeling the observed extrinsic variability resulting from the complicated magnification network produced by the lens galaxy stars' combined gravitational potential (see, e.g., Kochanek et al. 2006;Dai et al. 2010;Hainline et al. 2012Hainline et al. , 2013, who utilize the methods of Kochanek 2004). This technique necessitates cosmological modeling of the effective transverse velocity as well as larger amounts of observing time; however, it does not necessitate the assumption of the mean mass of a lens galaxy star. ...
We analyze variability in 15-season optical lightcurves from the doubly imaged lensed quasar SDSS J165043.44+425149.3 (SDSS1650), comprising five seasons of monitoring data from the Maidanak Observatory (277 nights in total, including the two seasons of data previously presented in Vuissoz et al.), five seasons of overlapping data from the Mercator telescope (269 nights), and 12 seasons of monitoring data from the US Naval Observatory, Flagstaff Station at lower cadence (80 nights). We update the 2007 time-delay measurement for SDSS1650 with these new data, finding a time delay of Δ t AB = − 55.1 − 3.7 + 4.0 days, with image A leading image B. We analyze the microlensing variability in these lightcurves using a Bayesian Monte Carlo technique to yield measurements of the size of the accretion disk at λ rest = 2420 Å, finding a half-light radius of log( r 1/2 /cm) = 16.19 − 0.58 + 0.38 assuming a 60° inclination angle. This result is unchanged if we model 30% flux contamination from the broad-line region. We use the width of the Mg ii line in the existing Sloan Digital Sky Survey spectra to estimate the mass of this system’s supermassive black hole, finding M BH = 2.47 × 10 ⁹ M ⊙ . We confirm that the accretion disk size in this system, whose black hole mass is on the very high end of the M BH scale, is fully consistent with the existing quasar accretion disk size–black hole mass relation.
... The single-epoch technique requires an assumption of a prior for the mean mass for the lens galaxy stars, and it can only be used in systems with short time delays, since it is not possible to differentiate between intrinsic and extrinsic flux ratio anomalies in systems with longer delays. In the second method, multi-epoch light curves are collected to analyze changes in the magnification of the quasar images as they move across the complex network of magnification from the aggregated gravitational potential of the lens galaxy stars (see e.g., Kochanek et al. 2006;Dai et al. 2010;Hainline et al. 2012Hainline et al. , 2013Cornachione et al. 2020b, who employ the technique of Kochanek 2004). This method requires more observing time and cosmological modeling of the effective transverse velocity, but it does not require an assumption of the median mass of the stars in the lens galaxy. ...
We present 10 seasons of Sloan Digital Sky Survey r -band monitoring observations and five seasons of H -band observations of the two-image system FBQ J0951+2635 from the Kaj Strand Astrometric Reflector at the United States Naval Observatory, Flagstaff Station. We supplement our light curves with six seasons of monitoring data from the literature to yield a 10 + 6 season combined data set, which we analyzed with our Monte Carlo microlensing analysis routine to generate constraints on the structure of this system’s continuum emission source and the properties of the lens galaxy. Complementing our optical light curves with the five-season near-infrared light curves, we ran a joint Monte Carlo analysis to measure the size of the continuum emission region at both wavelengths, yielding log( r 1/2 cm ⁻¹ ) = 16.24 − 0.36 + 0.33 in the r band and 17.04 − 0.30 + 0.26 in the H band at rest wavelengths of 2744 and 7254 Å, respectively, correcting for an assumed inclination angle of 60°. Modeling the accretion disk temperature profile as a power law T ( r ) ∝ r − β , we successfully constrain the slope for FBQ J0951+2635 to β = 0.50 − 0.18 + 0.50 , shallower than, but nominally consistent with, the predictions of standard thin-disk theory, β = 0.75.
... This microlensing magnification varies, on time scales of years to decades, as the quasar moves relative to the lensing stars along our line of sight. From a careful analysis of multi-season light curves we can place constraints on the compact quasar continuum emission region size (Kochanek 2004;Kochanek et al. 2006;Pooley et al. 2007;Eigenbrod et al. 2008;Poindexter et al. 2008;Morgan et al. 2010;Hainline et al. 2012Hainline et al. , 2013MacLeod et al. 2015;Morgan et al. 2018;. Microlensing measurements agree well with continuum emission region sizes measured through reverberation mapping (Peterson et al. 2004;Bentz et al. 2010;McHardy et al. 2014; arXiv:2012.05856v1 ...
... Poindexter et al. (2008) analyzed HE1104-1805 in multiple bands, measuring β = 0.61 +0.21 −0.17 , also consistent with the thin disk. Two band measurements in SBS 0909+532 and SDSS J0924+0219 yielded a shallower slope of β ≈ 0.5 but the error bars were too broad to exclude other models (Hainline et al. 2013;MacLeod et al. 2015). An alternate method of estimating β from aggregated multi-epoch size measurements at λ ≈ 2500 Å strongly supported a shallower slope of β < 0.56, but these findings were model dependent . ...
... Q0957 has a particularly long history, starting with its discovery (Walsh et al. 1979) and early microlensing constraints published two decades ago (Refsdal et al. 2000). Both systems are doubly imaged quasars with previous size measurements in the r-band with multi-epoch microlensing (Hainline et al. 2012(Hainline et al. , 2013. SBS0909 also has a g-band size measurement (Hainline et al. 2013), though the uncertainties were broad. ...
We present a microlensing analysis of updated light curves in three filters, $g$--band, $r$--band, and $H$--band, for the gravitationally lensed quasars Q0957+561 and SBS0909+532. Both systems display prominent microlensing features which we analyze using our Bayesian Monte Carlo technique to constrain the quasar continuum emission region sizes in each band. We report sizes as half-light radii scaled to a 60 degree inclination angle. For Q0957+561 we measure $\log{(r_{1/2}/\text{cm})} = 16.54^{+0.33}_{-0.33}$, $16.66^{+0.37}_{-0.62}$, and $17.37^{+0.49}_{-0.40}$ in $g$--, $r$--, and $H$--band respectively. For SBS0909+532 we measure $\log{(r_{1/2}/\text{cm})} = 15.83^{+0.33}_{-0.33}$, $16.21^{+0.37}_{-0.62}$, and $17.90^{+0.61}_{-0.63}$ in $g$--, $r$--, and $H$--band respectively. With size measurements in three bands spanning the quasar rest frame ultraviolet to optical, we can place constraints on the scaling of accretion disk size with wavelength, $r\propto\lambda^{1/\beta}$. In a joint analysis of both systems we find a slope shallower than that predicted by thin disk theory, $\beta = 0.35^{+0.16}_{-0.08}$, consistent with other constraints from multi-epoch microlensing studies.
... This microlensing magnification varies, on time scales of years to decades, as the quasar moves relative to the lensing stars along our line of sight. From a careful analysis of multi-season light curves we can place constraints on the compact quasar continuum emission region size (Kochanek 2004;Kochanek et al. 2006;Pooley et al. 2007;Eigenbrod et al. 2008;Poindexter et al. 2008;Morgan et al. 2010;Hainline et al. 2012Hainline et al. , 2013MacLeod et al. 2015;Morgan et al. 2018;. Microlensing measurements agree well with continuum emission region sizes measured through reverberation mapping (Peterson et al. 2004;Bentz et al. 2010;McHardy et al. 2014; arXiv:2012.05856v1 ...
... Poindexter et al. (2008) analyzed HE1104-1805 in multiple bands, measuring β = 0.61 +0.21 −0.17 , also consistent with the thin disk. Two band measurements in SBS 0909+532 and SDSS J0924+0219 yielded a shallower slope of β ≈ 0.5 but the error bars were too broad to exclude other models (Hainline et al. 2013;MacLeod et al. 2015). An alternate method of estimating β from aggregated multi-epoch size measurements at λ ≈ 2500 Å strongly supported a shallower slope of β < 0.56, but these findings were model dependent . ...
... Q0957 has a particularly long history, starting with its discovery (Walsh et al. 1979) and early microlensing constraints published two decades ago (Refsdal et al. 2000). Both systems are doubly imaged quasars with previous size measurements in the r-band with multi-epoch microlensing (Hainline et al. 2012(Hainline et al. , 2013. SBS0909 also has a g-band size measurement (Hainline et al. 2013), though the uncertainties were broad. ...
We present a microlensing analysis of updated light curves in three filters, the g-band, r-band, and H-band, for the gravitationally lensed quasars Q0957+561 and SBS0909+532. Both systems display prominent microlensing features which we analyze using our Bayesian Monte Carlo technique to constrain the quasar continuum emission region sizes in each band. We report sizes as half-light radii scaled to a 60° inclination angle. For Q0957+561 we measure log(r1/2/cm)=16.54+0.33−0.33 , 16.66+0.37−0.62 , and 17.37+0.49−0.40 in g-, r-, and H-band, respectively. For SBS0909+532 we measure log(r1/2/cm)=15.83+0.33−0.33 , 16.21+0.37−0.62 , and 17.90+0.61−0.63 in the g-, r-, and H-band respectively. With size measurements in three bands spanning the quasar rest frame ultraviolet to optical, we can place constraints on the scaling of accretion disk size with wavelength, r∝λ1/β . In a joint analysis of both systems we find a slope shallower than that predicted by thin disk theory, β=0.35+0.16−0.08 , consistent with other constraints from multi-epoch microlensing studies.
... Quasar Accretion Disk Size-Black Hole Mass Relation. The accretion disk sizes are scaled to λrest = 2500Å(Kochanek 2004;Morgan et al. 2008;Dai et al. 2010;Morgan et al. 2010;Hainline et al. 2012;Morgan et al. 2012;Hainline et al. 2013;MacLeod et al. 2015;Morgan et al. 2018;Cornachione et al. 2020). Microlensing sizes are shown as black dots with error bars and luminosity size estimates are shown as crosses (errors omitted). ...
... dian and 16 th to 84 th percentile range of the the reported posterior microlensing size distributions. These 15 systems are shown inFigure 1with both microlensing and luminosity sizes as a function of black hole mass, where the size offset is readily apparent(Kochanek 2004;Morgan et al. 2008;Dai et al. 2010;Morgan et al. 2010;Hainline et al. 2012;Morgan et al. 2012;Hainline et al. 2013;MacLeod et al. 2015;Morgan et al. 2018;Cornachione et al. 2020). ...
We compare the microlensing-based continuum emission region size measurements in a sample of 15 gravitationally lensed quasars with estimates of luminosity-based thin disk sizes to constrain the temperature profile of the quasar continuum accretion region. If we adopt the standard thin disk model, we find a significant discrepancy between sizes estimated using the luminosity and those measured by microlensing of $\log(r_{L}/r_{\mu})=-0.57\pm0.08\,\text{dex}$. If quasar continuum sources are simple, optically thick accretion disks with a generalized temperature profile $T(r) \propto r^{-\beta}$, the discrepancy between the microlensing measurements and the luminosity-based size estimates can be resolved by a temperature profile slope $0.37 < \beta < 0.56$ at $1\,\sigma$ confidence. This is shallower than the standard thin disk model ($\beta=0.75$) at $3\,\sigma$ significance. We consider alternate accretion disk models that could produce such a temperature profile and reproduce the empirical continuum size scaling with black hole mass, including disk winds or disks with non-blackbody atmospheres.
... With this technique, we have made measurements of accretion disk scale sizes in 15 quasars Morgan et al. 2006Morgan et al. , 2008Morgan et al. , 2010Morgan et al. , 2012Morgan et al. , 2018Poindexter et al. 2007;Hainline et al. 2012Hainline et al. , 2013Mosquera et al. 2013;Blackburne et al. 2014;MacLeod et al. 2015). This method requires cosmological modeling of the effective transverse velocity, but is insensitive to uncertainty in the median mass of stars in the lens galaxy. ...
... Quasar accretion disk sizes scaled to λ rest =2500 Å plotted as a function of the central black hole masses. WFI2026 is highlighted in blue, while the other available microlensing size measurements are shown as black dots(Kochanek 2004;Morgan et al. 2008Morgan et al. , 2010Morgan et al. , 2018Morgan et al. , 2012Dai et al. 2010;Hainline et al. 2012Hainline et al. , 2013MacLeod et al. 2015). The best-fit line fromMorgan et al. (2018) is shown in purple with 1σ error bars encompassed by the purple band. ...
We use 13 seasons of R -band photometry from the 1.2 m Leonard Euler Swiss Telescope at La Silla to examine microlensing variability in the quadruply imaged lensed quasar WFI 2026–4536. The lightcurves exhibit ∼0.2 mag of uncorrelated variability across all epochs and a prominent single feature of ∼0.1 mag within a single season. We analyze this variability to constrain the size of the quasar’s accretion disk. Adopting a nominal inclination of 60°, we find an accretion disk scale radius of at a rest-frame wavelength of 2043 Å, and we estimate a black hole mass of , based on the C iv line in VLT spectra. This size measurement is fully consistent with the quasar accretion disk size—black hole mass relation, providing another system in which the accretion disk is larger than predicted by thin-disk theory.
... These values and uncertainties are found from the median and 16th to 84th percentile range of the reported posterior microlensing size distributions. These 15 systems are shown in Figure 1 with both microlensing and luminosity sizes as a function of black hole mass, where the size offset is readily apparent (Kochanek 2004;Morgan et al. 2008Morgan et al. , 2010Morgan et al. , 2012Morgan et al. , 2018Dai et al. 2010;Hainline et al. 2012Hainline et al. , 2013MacLeod et al. 2015;Cornachione et al. 2020). ...
... Quasar accretion disk size-black hole mass relation. The accretion disk sizes are scaled to λ rest =2500 Å(Kochanek 2004;Morgan et al. 2008Morgan et al. , 2010Morgan et al. , 2012Morgan et al. , 2018Dai et al. 2010;Hainline et al. 2012Hainline et al. , 2013MacLeod et al. 2015;Cornachione et al. 2020). Microlensing sizes are shown as black dots with error bars and luminosity size estimates are shown as crosses (errors omitted). ...
We compare the microlensing-based continuum emission region size measurements in a sample of 15 gravitationally lensed quasars with estimates of luminosity-based thin disk sizes to constrain the temperature profile of the quasar continuum accretion region. If we adopt the standard thin disk model, we find a significant discrepancy between sizes estimated using the luminosity and those measured by microlensing of log( r L / r μ ) = −0.57 ± 0.08 dex. If quasar continuum sources are simple, optically thick accretion disks with a generalized temperature profile T ( r ) ∝ r − β , the discrepancy between the microlensing measurements and the luminosity-based size estimates can be resolved by a temperature profile slope 0.37 < β < 0.56 at 1 σ confidence. This is shallower than the standard thin disk model ( β = 0.75) at 3 σ significance. We consider alternate accretion disk models that could produce such a temperature profile and reproduce the empirical continuum size scaling with black hole mass, including disk winds or disks with nonblackbody atmospheres.
... Goicoechea & Shalyapin 2010;Koptelova et al. 2010), fitting multiple PSFs and parametric galaxy components (e.g. Kochanek et al. 2006b;Hainline et al. 2013;Shalyapin & Goicoechea 2017), difference imaging (e.g. Fohlmeister et al. 2013;Giannini et al. 2017), aperture photometry for wide-separation systems (e.g. ...
We report the results of the STRong lensing Insights into the Dark Energy Survey (STRIDES) follow-up campaign of the late 2017/early 2018 season. We obtained spectra of 65 lensed quasar candidates with ESO Faint Object Spectrograph and Camera 2 on the NTT and Echellette Spectrograph and Imager on Keck, confirming 10 new lensed quasars and 10 quasar pairs. Eight lensed quasars are doubly imaged with source redshifts between 0.99 and 2.90, one is triply imaged (DESJ0345−2545, z = 1.68), and one is quadruply imaged (quad: DESJ0053−2012, z = 3.8). Singular isothermal ellipsoid models for the doubles, based on high-resolution imaging from SAMI on Southern Astrophysical Research Telescope or Near InfraRed Camera 2 on Keck, give total magnifications between 3.2 and 5.6, and Einstein radii between 0.49 and 1.97 arcsec. After spectroscopic follow-up, we extract multi-epoch grizY photometry of confirmed lensed quasars and contaminant quasar + star pairs from DES data using parametric multiband modelling, and compare variability in each system’s components. By measuring the reduced χ2 associated with fitting all epochs to the same magnitude, we find a simple cut on the less variable component that retains all confirmed lensed quasars, while removing 94 per cent of contaminant systems. Based on our spectroscopic follow-up, this variability information improves selection of lensed quasars and quasar pairs from 34-45 per cent to 51–70 per cent, with most remaining contaminants being star-forming galaxies. Using mock lensed quasar light curves we demonstrate that selection based only on variability will over-represent the quad fraction by 10 per cent over a complete DES magnitude-limited sample, explained by the magnification bias and hence lower luminosity/more variable sources in quads.
... This problem has been well-explored by teams dedicated to lensed quasar monitoring for extraction of lightcurves and hence time delays. In particular, photometry has been extracted through fitting multiple PSFs (e.g., Goicoechea & Shalyapin 2010;Koptelova et al. 2010), fitting multiple PSFs and parametric galaxy components (e.g., Kochanek et al. 2006b;Shalyapin & Goicoechea 2017;Hainline et al. 2013), difference imaging (e.g., Fohlmeister et al. 2013;Giannini et al. 2017), aperture photometry for wideseparation systems (e.g., Ovaldsen et al. 2003;Dahle et al. 2015), and non-parametric deconvolutional techniques (e.g., Burud et al. 2002;Vuissoz et al. 2007;Bonvin et al. 2018). ...
We report the results of the STRong lensing Insights from the Dark Energy Survey (STRIDES) follow-up campaign of the late 2017/early 2018 season. We obtained spectra of 65 lensed quasar candidates either with EFOSC2 on the NTT or ESI on Keck, which confirm 10 new gravitationally lensed quasars and 10 quasar pairs with similar spectra, but which do not show a lensing galaxy in DES images. Eight lensed quasars are doubly imaged with source redshifts between 0.99 and 2.90, one is triply imaged by a group (DESJ0345-2545, $z=1.68$), and one is quadruply imaged (quad: DESJ0053-2012, $z=3.8$). Singular isothermal ellipsoid models for the doubles, based on high-resolution imaging from SAMI on SOAR or NIRC2 on Keck, give total magnifications between 3.2 and 5.6, and Einstein radii between 0.49 and 1.97 arcseconds. After spectroscopic follow-up, we extract multi-epoch $grizY$ photometry of confirmed lensed quasars and contaminant quasar+star pairs from the first 4 years of DES data using parametric multi-band modelling, and compare variability in each system's components. By measuring the reduced ${\chi}^2$ associated with fitting all epochs to the same magnitude, we find a simple cut on the less variable component that retains all confirmed lensed quasars, while removing 94 per cent of contaminant systems with stellar components. Based on our spectroscopic follow-up, this variability information can improve selection of lensed quasars and quasar pairs from 34-45 per cent to 51-70 per cent, with the majority of remaining contaminants being compact star-forming galaxies. Using mock lensed quasar lightcurves we demonstrate that selection based only on variability will over-represent the quad fraction by 10 per cent over a complete DES magnitude-limited sample (excluding microlensing differences), explained by the magnification bias and hence lower luminosity (more variable) sources in quads.
... Though quasars, in general, are known by their extremely high luminosities, gravitationally lensed quasars (hereinafter GLQs) are brighter than their unlensed counterparts and produce different image components (Lehár et al. 2000;Agnello et al. 2015). Study of GLQs provides significant information, mainly about background source quasar variability mechanisms and accretion disc structure (Pooley et al. 2007;Hainline et al. 2013;Jiménez-Vicente et al. 2015), the mass distribution in lensing galaxies (Oscoz et al. 1997;Lubin et al. 2000;Ullán et al. 2006;Bate et al. 2008) and, in general, information to constrain physical properties of the universe (Kochanek et al. 1997;Gil-Merino et al. 2018;Kostrzewa-Rutkowska et al. 2018). It has been understood that the time delay caused by gravitational lensing is directly related to the current expansion rate of the universe (the Hubble constant) and the mean surface mass density of the lensing galaxy (e.g. ...
Knowledge about how the non-linear behaviour of the intrinsic signal from lensed background sources changes on its path to the observer provides much information, particularly about the matter distribution in lensing galaxies and the physical properties of the current universe, in general. Here, we analyse the multifractal behaviour of the optical observations of A and B images of Q0957+561 in the r and g bands. Aims: To verify the presence, or absence, of extrinsic variations in the observed signals of the quasar images and whether extrinsic variations affect the multifractal behaviour of their intrinsic signals. Method: We apply a wavelet transform modulus maxima-based multifractality analysis approach. Results: We detect strong multifractal signatures in the light curves of the quasar images. The degree of multifractality for both images in the r band changes over time in a non-monotonic way, indicating the presence of extrinsic variabilities in the light curves of the images. Additionally, in the r band, in periods of quiescent microlensing activity, we find that the degree of multifractality of image A is stronger than that of B, while B has a larger multifractal strength in recent epochs when it appears to be affected by microlensing. Finally, comparing the optical bands in a period of quiescent microlensing activity, we find that the degree of multifractality is stronger in the r band for both quasar images. In the absence of microlensing, the observed excesses of non-linearity are most likely generated when the broad-line region reprocesses the radiation from the compact sources.
