EAYAM
November 17, 2017

Subaru Telescope adaptive optics
observations of gravitationally lensedquasars
Cristian Eduard Rusu
Subaru Fellow

Contents• Brief description of the adaptive optics imaging campaign• Selected result: J1405: and the “natural coronagraph” lens

Gravitationally lensed quasars (GLQs)• First discovery Walsh et al. 1979;~ 150 lensed quasars known• Typical configurations:
CfA-Arizona Space
Telescope LEns Survey(CASTLES)
Hubble Space Telescope(HST)• enable the study of the lens galaxy mass profile, quasar host galaxy, AGNstructure, cosmological parameters

The need for high resolution imaging• Typical GLQ image separation 1”− 2” ~ atmospherical seeing size
• The advent of AO: high resolution imaging possible from ground
IRCS+AO K’ band

• Conducted the first dedicated AO campaign of GLQs (2011-2014; Rusu etal. 2016)• Targets selected from SQLS: campaign to discover new lensed quasars
from SDSS (Oguri et al. 2006) ~ 60 new discoveries
Main goals:• obtain accurate relative astrometry/photometry/lens galaxy shape• detect previously unseen features such as the host galaxyAdaptive optics• Beacon to monitor wavefronts (NGS, LGS
R<18 mag)• Deformable mirror to correct distorsions• Beacon monitoring, correction computing,mirror correction cycle ~ 500 Hz

Subaru Telescope AO imaging campaign• ~1h/target imaging in K’ (with overhead) with IRCS+AO• observed 25 systems

K’ band:• better AO correction• less microlensing, intrinsic
variability, reddening• host galaxy more prominent• Data modeling is non-trivial: how to characterize the PSF?
• field too small to contain stars• AO PSF is time varying• Unique feature of lensed quasars: two/four point-like sources surrounding
the lens galaxy• PSF: 2 Moffat components• lens light: Sersic• lens mass: singular isothermal ellipsoid• Extended source: lensed Sersic•

More details (fitting technique, simulations)in Rusu et al. 2016

SDSS J1405+0959• zlens=0.66 zQSO=1.98• new components: GX, GY• GX: morphology unclear• J,H, K’ imaging for photo-z= 7 kpc

Photo-z estimates
G1, G2 ellipticals consistent with same
redshiftGX (assuming galaxy): larger, broad
redshift
GY (aperture photometry) consistent withquasar redshift

G2G1GXGYNature of GX
SIS+SIS+γ (no flux)
1) galaxy at high-z: unlikely, multiply imaged by G2
2) star: NO, different colors from any stars in near-IR3) 3rd quasar image: lensing models with GX as the 3rdquasar image produce a good fit

Assuming color difference due to extinction, can GX be
a 3rd quasar image?

RV = 3.1 ! E(BV ) ⇠ 0.8

Such extinction has been found in other lensed quasars

Nature of GY

source: sersic profile * PSF

Position, elongation and orientation of GY consistent with the host galaxy• SDSS J1405+0959 has an observed host galaxy arc without acentral quasar image → “natural coronagraph”• only three other natural coronagraphs are known
QSO
imageslensinggalaxyhost galaxy arc

J1206

J1405

MG 2016

• Observed all three with spectroscopy and AO imaging
Stay tuned for results...

QSO
imageslensinggalaxyhost galaxy arc

J1206

J1405

MG 2016

Conclusions and future prospects• Conducted the first ever AO imaging campaign of a large number of lensed
quasars (25 systems with Subaru Telescope)• Obtained astrometry, morphology and mass models competitive with HSTbased data → vast improvement over results from low-resolution data

• Discovered a “natural coronagraph” lens, a class of objects currently underinvestigation;• Other results in Rusu et al. 2016:-showed that it is possible to study the SMBH-host coevolution with AO data,
without an a-priori known PSF- for systems with large ellipticity, the mass is less elliptical than the light• Plans to continue the campaign as new lensed quasars are discovered fromHSC Survey