Subaru Mid-Infrared Imaging of the Quadruple Lenses PG 1115+080 and B1422+231: Limits on Substructure Lensing

We present mid-infrared imaging at 11.7 μm for the quadruple lens systems PG 1115+080 and B1422+231 using the cooled mid-infrared camera and spectrometer (COMICS) attached on the Subaru Telescope. These lensed QSOs are characterized by their anomalous optical and radio flux ratios, as obtained for A1 and A2 images of PG 1115+080 and A, B, and C images of B1422+231, respectively, i.e., such flux ratios are hardly able to be reproduced by lens models with a smooth mass distribution. Our mid-infrared observations for these images have revealed that the mid-infrared flux ratio A2/A1 of PG 1115+080 is virtually consistent with smooth lens models (but inconsistent with the optical flux ratio), whereas for B1422+231, the mid-infrared flux ratios among the A, B, and C images are in good agreement with the radio flux ratios. We also identify a clear infrared bump in the spectral energy distributions of these QSOs, thereby indicating that the observed mid-infrared fluxes originate from a hot dust torus around a QSO nucleus. Based on the size estimate of the dust torus, we place limits on the mass of a substructure in these lens systems causing the anomalous optical or radio flux ratios. For PG 1115+080, the mass of a substructure inside an Einstein radius ME is ≲16 M☉, corresponding to either a star or a low-mass CDM subhalo having a mass of M ≲ 2.2 × 104 M☉ inside a radius of 100 pc if modeled as a singular isothermal sphere (SIS). For B1422+231, we obtain ME ≳ 209 M☉, indicating that a CDM subhalo is more likely, having a mass of M ≳ 7.4 × 104 M☉.

[1]  M. Imanishi,et al.  Comparison of Nuclear Starburst Luminosities between Seyfert 1 and 2 Galaxies Based on Near-Infrared Spectroscopy , 2004, astro-ph/0408422.

[2]  M. Oguri.  Large-Separation Lensed Quasars in the SDSS , 2004, Proceedings of the International Astronomical Union.

[3]  K. Jahnke,et al.  Quasar host galaxy star formation activity from multicolour data , 2003, astro-ph/0311123.

[4]  W. Percival,et al.  The host galaxies of luminous quasars , 2003, astro-ph/0308436.

[5]  B. Peterson,et al.  Inner Size of a Dust Torus in the Seyfert 1 Galaxy NGC 4151 , 2003, astro-ph/0311338.

[6]  L. Moustakas,et al.  Spectroscopic Gravitational Lensing and Limits on the Dark Matter Substructure in Q2237+0305 , 2003, astro-ph/0309738.

[7]  V. Springel,et al.  Early Structure Formation and Reionization in a Warm Dark Matter Cosmology , 2003, astro-ph/0303622.

[8]  Edward J. Wollack,et al.  First-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Determination of Cosmological Parameters , 2003, astro-ph/0302209.

[9]  Institute for Advanced Study,et al.  Tests for Substructure in Gravitational Lenses , 2003, astro-ph/0302036.

[10]  C. Keeton,et al.  Analytic Cross Sections for Substructure Lensing , 2002, astro-ph/0209040.

[11]  T. Treu,et al.  The internal structure of the lens PG1115+080: breaking degeneracies in the value of the Hubble constant , 2002, astro-ph/0210002.

[12]  G. Helou,et al.  Hot dust in normal star-forming galaxies: J H K L^' photometry of the ISO Key Project sample , 2002, astro-ph/0209471.

[13]  L. Moustakas,et al.  Detecting dark matter substructure spectroscopically in strong gravitational lenses , 2002, astro-ph/0206176.

[14]  P. Schechter,et al.  Quasar Microlensing at High Magnification and the Role of Dark Matter: Enhanced Fluctuations and Suppressed Saddle Points , 2002, astro-ph/0204425.

[15]  R. Ivison,et al.  Accepted for publication in the Astrophysical Journal Preprint typeset using L ATEX style emulateapj v. 19/02/01 A SUBMILLIMETER SURVEY OF GRAVITATIONALLY LENSED QUASARS , 2002 .

[16]  R. Benton Metcalf,et al.  Flux Ratios as a Probe of Dark Substructures in Quadruple-Image Gravitational Lenses , 2001, astro-ph/0111427.

[17]  M. Chiba.  Probing Dark Matter Substructure in Lens Galaxies , 2001, astro-ph/0109499.

[18]  E. Agol,et al.  The size of the mid-IR emission region of a quasar inferred from microlensed images of Q2237 0305 , 2001, astro-ph/0112281.

[19]  C. Kochanek,et al.  Direct Detection of Cold Dark Matter Substructure , 2001, astro-ph/0111456.

[20]  P. Madau,et al.  Compound Gravitational Lensing as a Probe of Dark Matter Substructure within Galaxy Halos , 2001, astro-ph/0108224.

[21]  R. G. McMahon,et al.  A 1.2 mm MAMBO/IRAM-30 m survey of dust emission from the highest redshift PSS quasars , 2001, astro-ph/0107005.

[22]  A. Patnaik,et al.  Determination of time delay from the gravitational lens B1422+231 , 2001, astro-ph/0106104.

[23]  E. al.,et al.  Composite Quasar Spectra from the Sloan Digital Sky Survey , 2001, astro-ph/0105231.

[24]  S. Collin,et al.  Size-mass-luminosity relations in AGN and the role of the accretion disc , 2001, astro-ph/0103303.

[25]  Xiaohui Fan,et al.  A 250 GHz Survey of High-Redshift Quasars from the Sloan Digital Sky Survey , 2001, astro-ph/0103252.

[26]  Gunma Astronomical Observatory,et al.  ISO continuum observations of quasars at ${z=1{-}4}$ - I. Spectral energy distributions of quasars from the UV to far-infrared , 2000, astro-ph/0010550.

[27]  Shigeyuki Sako,et al.  COMICS: the cooled mid-infrared camera and spectrometer for the Subaru telescope , 2000, Astronomical Telescopes and Instrumentation.

[28]  M. Imanishi,et al.  Energy Diagnoses of Nine Infrared Luminous Galaxies Based on 3-4 Micron Spectra , 2000, astro-ph/0008092.

[29]  A. Moorwood,et al.  Optical and IR Telescope Instrumentation and Detectors , 2000 .

[30]  E. Agol,et al.  Keck Mid-Infrared Imaging of QSO 2237+0305 , 2000, astro-ph/0007269.

[31]  D. Weinberg,et al.  Reionization and the Abundance of Galactic Satellites , 2000, astro-ph/0002214.

[32]  M. Goto,et al.  Infrared Imaging of the Gravitational Lens PG 1115+080 with the Subaru Telescope , 2000, astro-ph/0001051.

[33]  E. Turner,et al.  A gravitational microlensing determination of continuum source size in Q2237+0305 , 1999, astro-ph/9904361.

[34]  George Lake,et al.  Dark Matter Substructure within Galactic Halos , 1999, astro-ph/9907411.

[35]  A. Kemball,et al.  Milliarcsec-scale polarization observations of the gravitational lens B1422+231 , 1999 .

[36]  Mark R. Kidger,et al.  Spectral Irradiance Calibration in the Infrared. X. A Self-Consistent Radiometric All-Sky Network of Absolutely Calibrated Stellar Spectra , 1999 .

[37]  G. Neugebauer,et al.  Variability of Quasars at 10 Microns , 1999, astro-ph/9903363.

[38]  F. Prada,et al.  Where are the missing galactic satellites? , 1999, astro-ph/9901240.

[39]  B. Peterson,et al.  A NEW DIRECT METHOD FOR MEASURING THE HUBBLE CONSTANT FROM REVERBERATING ACCRETION DISCS IN ACTIVE GALAXIES , 1998, astro-ph/9811278.

[40]  R. Hook,et al.  Drizzle: A Method for the Linear Reconstruction of Undersampled Images , 1998, astro-ph/9808087.

[41]  J. Lehár,et al.  An Infrared Einstein Ring in the Gravitational Lens PG 1115+080 , 1998, astro-ph/9803207.

[42]  J. Tonry.  Redshifts of the Gravitational Lenses B1422+231 and PG 1115+080 , 1997, astro-ph/9706199.

[43]  P. Schneider,et al.  Evidence for substructure in lens galaxies , 1997, astro-ph/9707187.

[44]  Judith G. Cohen,et al.  The external shear acting on gravitational lens B1422+231 , 1997, astro-ph/9706169.

[45]  R. Blandford,et al.  Keck Spectroscopy of the Gravitational Lens System PG 1115+080: Redshifts of the Lensing Galaxies. , 1997, astro-ph/9704109.

[46]  C. Foltz,et al.  Hubble Space Telescope Observations of the Gravitational Lens System B1422+231 , 1996 .

[47]  H. Yee,et al.  Variability in the Graviational Lens System B1422+231 , 1996 .

[48]  M. S. Oey,et al.  Atlas of quasar energy distributions , 1994 .

[49]  E. Ellingson,et al.  High resolution optical imaging of the gravitational lens system B1422+231 , 1994 .

[50]  D. Schneider,et al.  Imaging of the gravitational lens system PG 1115+080 with the Hubble Space Telescope , 1993 .

[51]  G. Kauffmann,et al.  The formation and evolution of galaxies within merging dark matter haloes , 1993 .

[52]  H. Takami,et al.  An infrared study of hot dust in quasars using prism spectrophotometry , 1993 .

[53]  Robert Antonucci,et al.  Unified models for active galactic nuclei and quasars , 1993 .

[54]  D. Walsh,et al.  B1422 + 231: a new gravitationally lensed system at z = 3.62 , 1992 .

[55]  R. Blandford,et al.  Microlensing and the structure of active galactic nucleus accretion disks , 1991 .

[56]  P. Schneider,et al.  Interpretation of the microlensing event in QSO 2237+0305 , 1990 .

[57]  G. Neugebauer,et al.  Continuum energy distribution of quasars: Shapes and origins , 1989 .

[58]  R. Barvainis,et al.  Hot Dust and the Near-Infrared Bump in the Continuum Spectra of Quasars and Active Galactic Nuclei , 1987 .

[59]  P. Waddell,et al.  Detection of the Lensing Galaxy in PG 1115+080 , 1987 .

[60]  C. Alcock.  Gravitational lenses , 1982, Nature.