PMN J2004–1349: A new gravitationally lensed quasar 1 (original) (raw)

PMN J2004-1349: A new gravitationally lensed quasar

2000

We report the discovery of a new double-image quasar resulting from our search for gravitational lenses in the southern sky. Radio source PMN J2004-1349 is composed of two flat-spectrum components of approximately equal brightness separated by 1. ′′ 13 in VLA, MERLIN and VLBA images. The I-band optical counterpart is also double, with roughly the same separation, position angle, and flux ratio as the radio double. Upon subtraction of the quasars from the I-band image, we identify a dim pattern of residuals as the lens galaxy. While the present observations are sufficient to establish that PMN J2004-1349 is a gravitational lens, additional information (such as the redshifts of the quasar and lens galaxy) will be needed before many interesting astrophysical quantities (such as the mass of the galaxy, or the predicted time delay between lensed images) can be inferred.

PMN J1838−3427: A New Gravitationally Lensed Quasar

The Astronomical Journal, 2000

We report the discovery of a new double-image quasar that was found during a search for gravitational lenses in the southern sky. Radio source PMN J1838[3427 is composed of two Ñat-spectrum components with separation Ñux density ratio 14: 1, and matching spectral indices in VLA and 1A .0, VLBA images. Ground-based BRI images show the optical counterpart (total I \ 18.6) is also double, with the same separation and position angle as the radio components. An HST /WFPC2 image reveals the lens galaxy. The optical Ñux ratio (27: 1) is higher than the radio value, probably because of di †erential extinction of the components by the lens galaxy. An optical spectrum of the bright component contains quasar emission lines at z \ 2.78 and several absorption features, including prominent Lya absorption. The lens galaxy redshift could not be measured, but it is estimated to be z \ 0.36^0.08. The image conÐguration is consistent with the simplest plausible models for the lens potential. The Ñat radio spectrum and observed variability of PMN J1838[3427 suggest that the time delay between Ñux variations of the components is measurable and could thus provide an independent measurement of H 0 .

PMN J1632−0033: A New Gravitationally Lensed Quasar

The Astronomical Journal, 2002

We report the discovery of a gravitationally lensed quasar resulting from our survey for lenses in the southern sky. Radio images of J1632-0033 with the VLA and ATCA exhibit two compact, flat-spectrum components with separation 1. ′′ 47 and flux density ratio 13.2. Images with the HST reveal the optical counterparts to the radio components and also the lens galaxy. An optical spectrum of the bright component, obtained with the first Magellan telescope, reveals quasar emission lines at redshift 3.42. Deeper radio images with MERLIN and the VLBA reveal a faint third radio component located near the center of the lens galaxy, which is either a third image of the background quasar or faint emission from the lens galaxy.

0 O ct 2 00 1 PMN J 1632 – 0033 : A new gravitationally lensed quasar

2008

We report the discovery of a gravitationally lensed quasar resulting from our survey for lenses in the southern sky. Radio images of J1632–0033 with the VLA and ATCA exhibit two compact, flat-spectrum components with separation 1. ′′47 and flux density ratio 13.2. Images with the HST reveal the optical counterparts to the radio components and also the lens galaxy. An optical spectrum of the bright component, obtained with the first Magellan telescope, reveals quasar emission lines at redshift 3.42. Deeper radio images with MERLIN and the VLBA reveal a faint third radio component located near the center of the lens galaxy, which is either a third image of the background quasar or faint emission from the lens galaxy. Subject headings: gravitational lensing, quasars: individual (J1632–0033)

PMN J1838(3427: A NEW GRAVITATIONALLY LENSED QUASAR1

2000

We report the discovery of a new double-image quasar that was found during a search for gravita- tional lenses in the southern sky. Radio source PMN J1838(3427 is composed of two —at-spectrum components with separation —ux density ratio 14:1, and matching spectral indices in VLA and 1A.0, VLBA images. Ground-based BRI images show the optical counterpart (total I \ 18.6)

SDSS J0246-0825: A New Gravitationally Lensed Quasar from the Sloan Digital Sky Survey

2005

We report the discovery of a new two-image gravitationally lensed quasar, SDSS J024634.11-082536.2 (SDSS J0246-0825). This object was selected as a lensed quasar candidate from the Sloan Digital Sky Survey (SDSS) by the same algorithm that was used to discover other SDSS lensed quasars (e.g., SDSS J0924+0219). Multicolor imaging with the Magellan Consortium's Walter Baade 6.5-m telescope and the spectroscopic observations using the W. M. Keck Observatory's Keck II telescope confirm that SDSS J0246-0825 consists of two lensed images ($\Delta{\theta}=$1\farcs04) of a source quasar at z=1.68. Imaging observations with the Keck telescope and the Hubble Space Telescope reveal an extended object between the two quasar components, which is likely to be a lensing galaxy of this system. From the absorption lines in the spectra of quasar components and the apparent magnitude of the galaxy, combined with the expected absolute magnitude from the Faber-Jackson relation, we estimate the redshift of the lensing galaxy to be z=0.724. A highly distorted ring is visible in the Hubble Space Telescope images, which is likely to be the lensed host galaxy of the source quasar. Simple mass modeling predicts the possibility that there is a small (faint) lensing object near the primary lensing galaxy.

Discovery of Two Gravitationally Lensed Quasars with Image Separations of 3″ from the Sloan Digital Sky Survey

The Astrophysical Journal, 2005

We report the discovery of two doubly-imaged quasars, SDSS J100128.61+502756.9 and SDSS J120629.65+433217.6, at redshifts of 1.838 and 1.789 and with image separations of 2. ′′ 86 and 2. ′′ 90, respectively. The objects were selected as lens candidates from the Sloan Digital Sky Survey (SDSS). Based on the identical nature of the spectra of the two quasars in each pair and the identification of the lens galaxies, we conclude -2that the objects are gravitational lenses. The lenses are complicated; in both systems there are several galaxies in the fields very close to the quasars, in addition to the lens galaxies themselves. The lens modeling implies that these nearby galaxies contribute significantly to the lens potentials. On larger scales, we have detected an enhancement in the galaxy density near SDSS J100128.61+502756.9. The number of lenses with image separation of ∼ 3 ′′ in the SDSS already exceeds the prediction of simple theoretical models based on the standard Lambda-dominated cosmology and observed velocity function of galaxies.

PMN J0134−0931: A Gravitationally Lensed Quasar with Unusual Radio Morphology

The Astrophysical Journal, 2002

The radio-loud quasar J0134-0931 was discovered to have an unusual morphology during our search for gravitational lenses. In VLA and MERLIN images, there are 5 compact components with maximum separation 681 mas. All of these components have the same spectral index from 5 GHz to 43 GHz. In a VLBA image at 1.7 GHz, a curved arc of extended emission joins two of the components in a manner suggestive of gravitational lensing. At least two of the radio components have near-infrared counterparts. We argue that this evidence implies that J0134-0931 is a gravitational lens, although we have not been able to devise a plausible model for the foreground gravitational potential. Like several other radio-loud lenses, the background source has an extraordinarily red optical counterpart.

SDSS J092455.87+021924.9: An Interesting Gravitationally Lensed Quasar from the Sloan Digital Sky Survey

The Astronomical Journal, 2003

We report the discovery of a new gravitationally lensed quasar from the Sloan Digital Sky Survey, SDSS J092455.87+021924.9 (SDSS J0924+0219). This object was selected from among known SDSS quasars by an algorithm that was designed to select another known SDSS lensed quasar (SDSS 1226−0006A,B). Five separate components, three of which are unresolved, are identified in photometric follow-up observations obtained with the Magellan Consortium's 6.5m Walter Baade telescope at Las Campanas Observatory. Two of the unresolved components (designated A and B) are confirmed to be quasars with z = 1.524; the velocity difference is less than 100 km sec −1 according to spectra taken with the W. M. Keck Observatory's Keck II telescope on Mauna Kea. A third stellar component, designated C, has the colors of a quasar with redshift similar to components A and B. The maximum separation of the point sources is 1. ′′ 78. The other two sources, designated G and D, are resolved. Component G appears to be the best candidate for the lensing galaxy. Although component D is near the expected position of the fourth lensed component in a four image lens system, its properties are not consistent with being the image of a quasar at z ∼ 1.5. Nevertheless, the identical redshifts of components A and B and the presence of component C strongly suggest that this object is a gravitational lens. Our observations support the idea that a foreground object reddens the fourth lensed component and that another unmodeled effect (such as micro-or milli-lensing) demagnificates it, but we cannot rule out the possibility that SDSS0924+0219 is an example of the relatively rare class of "three component" lens systems.