3c 220.3: A Radio Galaxy Lensing a Submillimeter Galaxy

Abstract

Herschel Space Observatory photometry and extensive multiwavelength follow-up have revealed that the powerful radio galaxy (PRG) 3C 220.3 at z = 0.685 acts as a gravitational lens for a background submillimeter galaxy (SMG) at z = 2.221. At an observed wavelength of 1 mm, the SMG is lensed into three distinct images. In the observed near infrared, these images are connected by an arc of ∼1 .8 radius forming an Einstein half-ring centered near the radio galaxy. In visible light, only the arc is apparent. 3C 220.3 is the only known instance of strong galaxy-scale lensing by a PRG not located in a galaxy cluster and therefore it offers the potential to probe the dark matter content of the radio galaxy host. Lens modeling rejects a single lens, but two lenses centered on the radio galaxy host A and a companion B, separated by 1 .5, provide a fit consistent with all data and reveal faint candidates for the predicted fourth and fifth images. The model does not require an extended common dark matter halo, consistent with the absence of extended bright X-ray emission on our Chandra image. The projected dark matter fractions within the Einstein radii of A (1 .02) and B (0 .61) are about 0.4 ± 0.3 and 0.55 ± 0.3. The mass to i-band light ratios of A and B, M/L i ∼ 8 ± 4 M L −1 , appear comparable to those of radio-quiet lensing galaxies at the same redshift in the CfA-Arizona Space Telescope LEns Survey, Lenses Structure and Dynamics, and Strong Lenses in the Legacy Survey samples. The lensed SMG is extremely bright with observed f (250 μm) = 440 mJy owing to a magnification factor μ ∼ 10. The SMG spectrum shows luminous, narrow C iv λ1549 Å emission, revealing that the SMG houses a hidden quasar in addition to a violent starburst. Multicolor image reconstruction of the SMG indicates a bipolar morphology of the emitted ultraviolet (UV) light suggestive of cones through which UV light escapes a dust-enshrouded nucleus.

THE CHANDRA SURVEY OF EXTRAGALACTIC SOURCES IN THE 3CR CATALOG: X-RAY EMISSION FROM NUCLEI, JETS, AND HOTSPOTS IN THE CHANDRA ARCHIVAL OBSERVATIONS

“…4. This is a radio galaxy lying at z=0.685 which is lensing a submillimeter galaxy at z=2.221 (Haas et al 2014).…”

Red, redder, reddest: SCUBA-2 imaging of colour-selected Herschel sources

“…All 17 sources with radio fluxes in excess of 1 mJy are removed using the the 21-cm radio catalogues from the NRAO VLA Sky Survey (NVSS, Becker et al 1995) and the Radio Sky at Twenty-cm (FIRST) survey (Condon et al 1998) to avoid contamination by flat spectrum quasars at z < 1. The rejection of NVSS/FIRST sources means that we potentially miss some genuine red sources that are lensed by radio-loud galaxies (Haas et al 2014;Leung & Riechers 2016). The final Asboth et al (2016) catalogue contains a total of 477 sources.…”

STAR FORMATION IN 3CR RADIO GALAXIES AND QUASARS AT z < 1*

“…Two HERGs, 3C 175.1 and 3C 220.3, have been removed from the analysis. The former has insufficient ancillary data in the literature, and the latter acts as gravitational lens for a submillimetre galaxy at z = 2.2 (Haas et al 2014).…”

“…We checked the positions given by Laing et al (1983) and inspected WISE images. Positions from high resolution radio maps (Mullin et al 2006;Haas et al 2014) or positions seen with Chandra at 2-8keV were taken whenever available. For the low-redshift sample the coordinates were revised to match Willot's positions 2 .…”

“…7.-Spectral energy distributions of two HERGs at 0.5 < z < 1, which have been excluded from the analysis. 3C 175.1 has too few data points and 3C 220.3 shows excess FIR-submm emission due to a gravitationally lensed submillimetre galaxy at z=2.2(Haas et al 2014). Notation as inFig.1.Fig.…”