Is the Optically Unidentified Radio Source, FIRST J121839.7+295325, a Dark Lens?

Abstract

We present evidence that the optically unidentified radio source, FIRST J121839.7+295325, may be strongly lensing a background galaxy. We estimate the redshift of the assumed gravitational arc, discovered in parallel imaging with HST, from MMT-Blue Channel spectroscopy to be z_{arc}=2.48_-0.05^+0.14. We present lens models with an Einstein radius of R_E=1.3" which contains a mass of M_{dyn}=10^{12 +- 0.5} M_{sol}, where the uncertainty reflects the range of possible lens redshifts. The putative lens is not detected to J_{lim}=22.0 mag and H_{lim}=20.7 mag in our MMT-SWIRC imaging. Using the flux limits from WFPC2 and SWIRC, we estimate that the dynamical mass-to-light ratio of J121839.7+295325 is M_{dyn}/L_B >~ 10 M_sol/L_sol for A_V=1 mag, and this lower limit could be as high as 30 M_sol/L_sol for A_V=0 mag. Since the radio source is optically unidentified (V_{lim}=25.5 mag) and has a radio flux of S_{1.4 GHz}=33 mJy, it is likely a massive early-type galaxy which hosts a radio-loud AGN at 0.8<z<1.5. However, the present data cannot uniquely determine the mass-to-light ratio of the lensing galaxy, and hence the possibility that this system may be a reasonably dark lens is not ruled out.

arXiv comment5 pages, 3 figures (1 color), accepted to ApJ. Made minor changes and fixed typos

References in corpus (39)

• Stellar population synthesis at the resolution of 2003
• Wilkinson Microwave Anisotropy Probe (WMAP) Three Year Results: Implications for Cosmology
• The Luminosity Function of Galaxies in SDSS Commissioning Data
• The Stellar Populations and Evolution of Lyman Break Galaxies
• The Sloan Lens ACS Survey. III - The Structure and Formation of Early-type Galaxies and their Evolution since z~1
• The Sloan Lens ACS Survey. I. A Large Spectroscopically Selected Sample of Massive Early-Type Lens Galaxies
• The Stellar, Gas and Dynamical Masses of Star-Forming Galaxies at z~2
• A Significant Population of Red, Near-IR Selected High Redshift Galaxies
• Probing the Coevolution of Supermassive Black Holes and Galaxies Using Gravitationally Lensed Quasar Hosts
• The Sloan-Lens ACS Survey II: stellar populations and internal structure of early-type lens galaxies
• The Optical Properties of Gravitational Lens Galaxies as a Probe of Galaxy Structure and Evolution
• HST Observations of 10 Two-Image Gravitational Lenses
• Stellar and Dynamical Masses of Ellipticals in the Sloan Digital Sky Survey
• A Substantial Population of Red Galaxies at z > 2: Modeling of the Spectral Energy Distributions of an Extended Sample
• Optical and Near-IR Imaging of Ultra Steep Spectrum Radio Sources - The K-z diagram of radio and optically selected galaxies
• The Evolution and Structure of Early-type Field Galaxies: A Combined Statistical Analysis of Gravitational Lenses
• The Importance of Einstein Rings
• The evolution of early-type galaxies at z~1 from the K20 survey
• Spectroscopy of Ultra Steep Spectrum Radio Sources
• The LBDS Hercules sample of mJy radio sources at 1.4 GHz - II. Redshift distribution, radio luminosity function, and the high-redshift cut-off
• A K-band Selected Photometric Redshift Catalog in the HDF-S: Sampling the Rest-Frame V-Band to z=3
• Binary quasars
• Deep near-IR observations of the Chandra Deep Field and of the HDF-South - Color and Number Counts
• Quantitative Morphology of Galaxies in the Core of the Coma Cluster
• The Top Ten List of Gravitational Lens Candidates from the HST Medium Deep Survey
• The Faint and Extremely Red K-band Selected Galaxy Population in the DEEP2/Palomar Fields
• Dynamical Models of Elliptical Galaxies in z=0.5 Clusters: II. Mass-to-Light Ratio Evolution without Fundamental Plane Assumptions
• A Deep, High-Resolution Survey at 74 MHz
• The Galaxy Luminosity Function at z~1 in the HUDF: Probing the Dwarf Population
• A conspicuous tangential alignment of galaxies in a STIS Parallel Shear Survey field: A new dark-lens candidate ?
• Probing a massive radio galaxy with gravitational lensing
• The Quasar Pair Q 1634+267 A, B and the Binary QSO vs. Dark Lens Hypotheses
• The Expected Properties of Dark Lenses
• Chandra Observations of the QSO Pair Q2345+007: Binary Quasar or Massive Dark Lens?
• MGC2214+3550: A New Binary Quasar
• A weak lensing analysis of a STIS dark-lens candidate
• Cosmic shear from STIS Pure Parallels: I Data
• CTQ 839: Candidate for the Smallest Projected Separation Binary Quasar
• The Double Quasar Q2138-431: Lensing by a Dark Galaxy?

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