143 research outputs found
Discovery of a Probable Physical Triple Quasar
We report the discovery of the first known probable case of a physical triple
quasar (not a gravitational lens). A previously known double system, QQ
1429-008 at z = 2.076, is shown to contain a third, fainter QSO component at
the same redshift within the measurement errors. Deep optical and IR imaging at
the Keck and VLT telescopes has failed to reveal a plausible lensing galaxy
group or a cluster, and moreover, we are unable to construct any viable lensing
model which could lead to the observed distribution of source positions and
relative intensities of the three QSO image components. Furthermore, there are
hints of differences in broad-band spectral energy distributions of different
components, which are more naturally understood if they are physically distinct
AGN. Therefore, we conclude that this system is most likely a physical triple
quasar, the first such close QSO grouping known at any redshift. The projected
component separations in the restframe are ~ 30 - 50 kpc for the standard
concordance cosmology, typical of interacting galaxy systems. The existence of
this highly unusual system supports the standard picture in which galaxy
interactions lead to the onset of QSO activity.Comment: Submitted to ApJL, LaTeX, 13 pages, 4 eps figures, all include
COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses XIII: Time delays and 9-yr optical monitoring of the lensed quasar RX J1131-1231
We present the results from nine years of optically monitoring the
gravitationally lensed z=0.658 quasar RX J1131-1231. The R-band light curves of
the four individual images of the quasar were obtained using deconvolution
photometry for a total of 707 epochs. Several sharp quasar variability features
strongly constrain the time delays between the quasar images. Using three
different numerical techniques, we measure these delays for all possible pairs
of quasar images while always processing the four light curves simultaneously.
For all three methods, the delays between the three close images A, B, and C
are compatible with being 0, while we measure the delay of image D to be 91
days, with a fractional uncertainty of 1.5% (1 sigma), including systematic
errors. Our analysis of random and systematic errors accounts in a realistic
way for the observed quasar variability, fluctuating microlensing magnification
over a broad range of temporal scales, noise properties, and seasonal gaps.
Finally, we find that our time-delay measurement methods yield compatible
results when applied to subsets of the data.Comment: 11 pages, 9 figures, minor additions to the text only, techniques and
results remain unchanged, A&A in pres
Zooming into the broad line region of the gravitationally lensed quasar Q2237+0305 = the Einstein Cross: III. Determination of the size and structure of the CIV and CIII] emitting regions using microlensing
Aims: We aim to use microlensing taking place in the lensed quasar Q2237+0305 to study the structure of the broad line region and measure the size of the region emitting the CIV and CIII] lines. Methods: Based on 39 spectrophotometric monitoring data points obtained between Oct. 2004 and Dec. 2007, we derive lightcurves for the CIV and CIII] emission lines. We use three different techniques to analyse the microlensing signal. Different components of the lines (narrow, broad and very broad) are identified and studied. We build a library of simulated microlensing lightcurves which reproduce the signal observed in the continuum and in the lines provided only the source size is changed. A Bayesian analysis scheme is then developed to derive the size of the various components of the BLR. Results: 1. The half-light radius of the region emitting the CIV line is found to be R_CIV ~ 66^{+110}_{-46} lt-days = 0.06^{+0.09}_{-0.04} pc = 1.7^{+2.8}_{-1.1} 10^17 cm (at 68.3% CI). Similar values are obtained for CIII]. Relative sizes of the V-band continuum and of the carbon line emitting regions are also derived with median values of R(line)/R(cont) in the range [4,29], depending of the FWHM of the line component. 2. The size of the CIV emitting region agrees with the Radius-Luminosity relationship derived from reverberation mapping. Using the virial theorem we derive the mass of the black hole in Q2237+0305 to be M_BH ~ 10^{8.3+/-0.3} M_sun. 3. We find that the CIV and CIII] lines are produced in at least 2 spatially distinct regions, the most compact one giving rise to the broadest component of the line. The broad and narrow line profiles are slightly different for CIV and CIII]. 4. Our analysis suggests a different structure of the CIV and FeII+III emitting regions, with the latter being produced in the inner part of the BLR or in a less extended emitting region than CIV.Peer reviewe
Three-body equations of motion in successive post-Newtonian approximations
There are periodic solutions to the equal-mass three-body (and N-body)
problem in Newtonian gravity. The figure-eight solution is one of them. In this
paper, we discuss its solution in the first and second post-Newtonian
approximations to General Relativity. To do so we derive the canonical
equations of motion in the ADM gauge from the three-body Hamiltonian. We then
integrate those equations numerically, showing that quantities such as the
energy, linear and angular momenta are conserved down to numerical error. We
also study the scaling of the initial parameters with the physical size of the
triple system. In this way we can assess when general relativistic results are
important and we determine that this occur for distances of the order of 100M,
with M the total mass of the system. For distances much closer than those,
presumably the system would completely collapse due to gravitational radiation.
This sets up a natural cut-off to Newtonian N-body simulations. The method can
also be used to dynamically provide initial parameters for subsequent full
nonlinear numerical simulations.Comment: 8 pages, 9 figure
Microlensing variability in the gravitationally lensed quasar Q2237+0305 = the Einstein Cross, I. Spectrophotometric monitoring with the VLT
We present the results of the first long-term (2.2 years) spectroscopic
monitoring of a gravitationally lensed quasar, namely the Einstein Cross
Q2237+0305. The goal of this paper is to present the observational facts to be
compared in follow-up papers with theoretical models to constrain the inner
structure of the source quasar. We spatially deconvolve deep VLT/FORS1 spectra
to accurately separate the spectrum of the lensing galaxy from the spectra of
the quasar images. Accurate cross-calibration of the 58 observations at
31-epoch from October 2004 to December 2006 is carried out with non-variable
foreground stars observed simultaneously with the quasar. The quasar spectra
are further decomposed into a continuum component and several broad emission
lines to infer the variations of these spectral components. We find prominent
microlensing events in the quasar images A and B, while images C and D are
almost quiescent on a timescale of a few months. The strongest variations are
observed in the continuum of image A. Their amplitude is larger in the blue
(0.7 mag) than in the red (0.5 mag), consistent with microlensing of an
accretion disk. Variations in the intensity and profile of the broad emission
lines are also reported, most prominently in the wings of the CIII] and center
of the CIV emission lines. During a strong microlensing episode observed in
June 2006 in quasar image A, the broad component of the CIII] is more highly
magnified than the narrow component. In addition, the emission lines with
higher ionization potentials are more magnified than the lines with lower
ionization potentials, consistent with the results obtained with reverberation
mapping. Finally, we find that the V-band differential extinction by the lens,
between the quasar images, is in the range 0.1-0.3 mag.Comment: 16 pages, 16 figures, A&A accepted, corrected Fig. 1
H0LiCOW XII. Lens mass model of WFI2033-4723 and blind measurement of its time-delay distance and
We present the lens mass model of the quadruply-imaged gravitationally lensed
quasar WFI2033-4723, and perform a blind cosmographical analysis based on this
system. Our analysis combines (1) time-delay measurements from 14 years of data
obtained by the COSmological MOnitoring of GRAvItational Lenses (COSMOGRAIL)
collaboration, (2) high-resolution imaging,
(3) a measurement of the velocity dispersion of the lens galaxy based on
ESO-MUSE data, and (4) multi-band, wide-field imaging and spectroscopy
characterizing the lens environment. We account for all known sources of
systematics, including the influence of nearby perturbers and complex
line-of-sight structure, as well as the parametrization of the light and mass
profiles of the lensing galaxy. After unblinding, we determine the effective
time-delay distance to be , an average
precision of . This translates to a Hubble constant , assuming a flat CDM
cosmology with a uniform prior on in the range [0.05, 0.5].
This work is part of the Lenses in COSMOGRAIL's Wellspring (H0LiCOW)
collaboration, and the full time-delay cosmography results from a total of six
strongly lensed systems are presented in a companion paper (H0LiCOW XIII).Comment: Version accepted by MNRAS. 29 pages including appendix, 17 figures, 6
tables. arXiv admin note: text overlap with arXiv:1607.0140
Constraining quasar structure using high-frequency microlensing variations and continuum reverberation
peer reviewedGravitational microlensing is a powerful tool for probing the inner structure of strongly lensed quasars and for constraining parameters of the stellar mass function of lens galaxies. This is achieved by analysing microlensing light curves between the multiple images of strongly lensed quasars and accounting for the effects of three main variable components: (1) the continuum flux of the source, (2) microlensing by stars in the lens galaxy, and (3) reverberation of the continuum by the broad line region (BLR). The latter, ignored by state-of-the-art microlensing techniques, can introduce high-frequency variations which we show carry information on the BLR size. We present a new method that includes all these components simultaneously and fits the power spectrum of the data in the Fourier space rather than the observed light curve itself. In this new framework, we analyse COSMOGRAIL light curves of the two-image system QJ 0158-4325 known to display high-frequency variations. Using exclusively the low-frequency part of the power spectrum, our constraint on the accretion disk radius agrees with the thin-disk model estimate and the results of previous work where the microlensing light curves were fit in real space. However, if we also take into account the high-frequency variations, the data favour significantly smaller disk sizes than previous microlensing measurements. In this case, our results are only in agreement with the thin-disk model prediction only if we assume very low mean masses for the microlens population, i.e
COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses VII. Time delays and the Hubble constant from WFI J2033-4723
Gravitationally lensed quasars can be used to map the mass distribution in
lensing galaxies and to estimate the Hubble constant H0 by measuring the time
delays between the quasar images. Here we report the measurement of two
independent time delays in the quadruply imaged quasar WFI J2033-4723 (z =
1.66). Our data consist of R-band images obtained with the Swiss 1.2 m EULER
telescope located at La Silla and with the 1.3 m SMARTS telescope located at
Cerro Tololo. The light curves have 218 independent epochs spanning 3 full
years of monitoring between March 2004 and May 2007, with a mean temporal
sampling of one observation every 4th day. We measure the time delays using
three different techniques, and we obtain Dt(B-A) = 35.5 +- 1.4 days (3.8%) and
Dt(B-C) = 62.6 +4.1/-2.3 days (+6.5%/-3.7%), where A is a composite of the
close, merging image pair. After correcting for the time delays, we find R-band
flux ratios of F_A/F_B = 2.88 +- 0.04, F_A/F_C = 3.38 +- 0.06, and F_A1/F_A2 =
1.37 +- 0.05 with no evidence for microlensing variability over a time scale of
three years. However, these flux ratios do not agree with those measured in the
quasar emission lines, suggesting that longer term microlensing is present. Our
estimate of H0 agrees with the concordance value: non-parametric modeling of
the lensing galaxy predicts H0 = 67 +13/-10 km s-1 Mpc-1, while the Single
Isothermal Sphere model yields H0 = 63 +7/-3 km s-1 Mpc-1 (68% confidence
level). More complex lens models using a composite de Vaucouleurs plus NFW
galaxy mass profile show twisting of the mass isocontours in the lensing
galaxy, as do the non-parametric models. As all models also require a
significant external shear, this suggests that the lens is a member of the
group of galaxies seen in field of view of WFI J2033-4723.Comment: 14 pages, 12 figures, published in A&
COSMOGRAIL XVIII: time delays of the quadruply lensed quasar WFI2033-4723
We present new measurements of the time delays of WFI2033-4723. The data sets
used in this work include 14 years of data taken at the 1.2m Leonhard Euler
Swiss telescope, 13 years of data from the SMARTS 1.3m telescope at Las
Campanas Observatory and a single year of high-cadence and high-precision
monitoring at the MPIA 2.2m telescope. The time delays measured from these
different data sets, all taken in the R-band, are in good agreement with each
other and with previous measurements from the literature. Combining all the
time-delay estimates from our data sets results in Dt_AB = 36.2-0.8+0.7 days
(2.1% precision), Dt_AC = -23.3-1.4+1.2 days (5.6%) and Dt_BC = -59.4-1.3+1.3
days (2.2%). In addition, the close image pair A1-A2 of the lensed quasars can
be resolved in the MPIA 2.2m data. We measure a time delay consistent with zero
in this pair of images. We also explore the prior distributions of microlensing
time-delay potentially affecting the cosmological time-delay measurements of
WFI2033-4723. There is however no strong indication in our measurements that
microlensing time delay is neither present nor absent. This work is part of a
H0LiCOW series focusing on measuring the Hubble constant from WFI2033-4723.Comment: Submitted to Astronomy and Astrophysic
J1721+8842: a gravitationally lensed binary quasar with a proximate damped Lyman-α absorber
High-redshift binary quasars provide key insights into mergers and quasar activity, and are useful tools for probing the spatial kinematics and chemistry of galaxies along the line of sight. However, only three sub-10-kpc binaries have been confirmed above z = 1. Gravitational lensing would provide a way to easily resolve such binaries, study them in higher resolution, and provide more sightlines, though the required alignment with a massive foreground galaxy is rare. Through image deconvolution of StanCam Nordic Optical Telescope (NOT) monitoring data, we reveal two further point sources in the known, z ≈ 2.38, quadruply lensed quasar (quad) J1721+8842. An ALFOSC/NOT long-slit spectrum shows that the brighter of these two sources is a quasar with z = 2.369 ± 0.007 based on the C III] line, while the C III] redshift of the quad is z = 2.364 ± 0.003. Lens modelling using point-source positions rules out a single source model, favouring an isothermal lens mass profile with two quasar sources separated by ∼6.0 kpc (0.73″) in projection. Given the resolving ability from lensing and current lensed quasar statistics, this discovery suggests a large population of undiscovered, unlensed sub-10-kpc binaries. We also analyse spectra of two images of the quad, showing narrow Lyα emission within the trough of a proximate damped Lyman-α absorber (PDLA). An apparent mismatch between the continuum and narrow line flux ratios provides a new potential tool for simultaneously studying microlensing and the quasar host galaxy. Signs of the PDLA are also seen in the second source, but a deeper spectrum is still required to confirm this. Thanks to the multiple lines of sight from lensing and two quasar sources, this system offers simultaneous subparsec- and kiloparsec-scale probes of a PDLA. The reduced 2D spectra are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/657/A113</A
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