J. A. Munoz

The Evolution of a Mass-selected Sample of Early-Type Field Galaxies

We investigate the evolution of mass-selected early-type field galaxies using a sample of 28 gravitational lenses spanning the redshift range 0 z 1. Based on the redshift-dependent intercept of the fundamental plane in the rest-frame B band, we measure an evolution rate of d log(M/L)B/dz = -0.56 ± 0.04 (all errors are 1 σ unless noted) if we directly compare to the local intercept measured from the Coma Cluster. Refitting the local intercept helps minimize potential systematic errors and yields an evolution rate of d log(M/L)B/dz = -0.54 ± 0.09. An evolution analysis of properly corrected aperture mass-to-light ratios (defined by the lensed image separations) is closely related to the Faber-Jackson relation. In the rest-frame B band, we find an evolution rate of d log(M/L)B/dz = -0.41 ± 0.21, a present-day characteristic magnitude of M*0 = -19.70 + 5 log h ± 0.29 (assuming a characteristic velocity dispersion of σDM* = 225 km s-1), and a Faber-Jackson slope of γFJ = 3.29 ± 0.58. The measured evolution rates favor old stellar populations (mean formation redshift zf > 1.8 at 2 σ confidence for a Salpeter initial mass function and a flat Ωm = 0.3 cosmology) among early-type field galaxies and argue against significant episodes of star formation at z < 1.

The Influence of Gravitational Microlensing on the Broad Emission Lines of Quasars

We discuss the effects of microlensing on the broad emission lines (BELs) of QSOs in the light of recent determinations of the size of the broad-line region (BLR) and its scaling with QSO luminosity. Microlensing by star-sized objects can produce significant amplifications in the BEL of some multiple-imaged QSOs, and could be very relevant for high-ionization lines. We have identified a group of 10 gravitational lens systems (~30% of the selected sample) in which microlensing could be observed. Using standard kinematic models for active galactic nuclei, we have studied the changes induced in the line profile by a microlens located at different positions with respect to the center of the BLR. We found that microlensing could produce important effects such as the relative enhancement of different parts of the line profile or the displacement of the peak of the line. The study of BEL profiles of different ionization in a microlensed QSO image could be an alternative method for probing the BLR structure and size.

Detection of the 2175 Å Extinction Feature at z = 0.83

We determine the extinction curve in the z_l=0.83 lens galaxy of the gravitational lens SBS0909+532 from the wavelength dependence of the flux ratio between the lensed quasar images (z_s=1.38) from 3400 to 9200AA. It is the first measurement of an extinction curve at a cosmological distance of comparable quality to those obtained within the Galaxy. The extinction curve has a strong 2175AA feature, a noteworthy fact because it has been weak or non-existent in most estimates of extinction curves outside the Galaxy. The extinction curve is fitted well by a standard

Cusped Mass Models of Gravitational Lenses

R_V=2.1pm0.9

The Nature and Size of the Optical Continuum Source in QSO 2237+0305

Galactic extinction curve. If we assume standard Galactic extinction laws, the estimated dust redshift of

B1359+154: A Six-Image Lens Produced by a z 1 Compact Group of Galaxies

z=0.88pm0.02

QSO 2237+0305 VR Light Curves from Gravitational LensES International Time Project Optical Monitoring

is in good agreement with the spectroscopic redshift of the lens galaxy. The widespread assumption that SMC extinction curves are more appropriate models for cosmological dust may be incorrect.

Time Delay in QSO 0957+561 From 1984-1999 Optical Data

Recent observations of galaxy luminosity profiles and dark matter simulations find luminosity and mass distributions characterized by central cusps rather than finite core radii. We introduce and implement a set of cusped ellipsoidal lens models that include limits similar to the Jaffe, Hernquist, η and NFW models and apply them to the gravitational lenses APM 08279+5255 and B1933+503. A successful model of APM 08279+5255 with its central, odd image requires a very shallow cusp, γ 0.4, where ρ ∝ r-γ as r → 0, which is similar to a core rather than the favored 1 γ 2 cusps. B1933+503, by contrast, is well modeled with a steep density cusp, 1.6 γ 2.0.

PMN J1838−3427: A New Gravitationally Lensed Quasar*

From the peak of a gravitational microlensing high-magnification event in the A component of QSO 2237+0305, which was accurately monitored by the Gravitational Lenses International Time Project collaboration, we derived new information on the nature and size of the optical V-band and R-band sources in the distant quasar. If the microlensing peak is caused by a microcaustic crossing, we first obtain that the standard accretion disk is a scenario more reliable/feasible than other typical axially symmetric models. Moreover, the standard scenario fits both the V-band and R-band observations with reduced χ2 values very close to 1. Taking into account all these results, a standard accretion disk around a supermassive black hole is a good candidate for the optical continuum main source in QSO 2237+0305. Second, using the standard source model and a robust upper limit on the transverse galactic velocity, we infer that 90% of the V-band and R-band luminosities are emitted from a region with a radial size less than 1.2 × 10-2 pc (=3.7 × 1016 cm, at a 2 σ confidence level).

The influence of microlensing on the shape of the AGN Fe Kα line

Hubble Space Telescope (HST) V- and I-band observations show that the gravitational lens B1359+154 consists of six images of a single zs = 3.235 radio source and its star-forming host galaxy, produced by a compact group of galaxies at zl 1. Very Long Baseline Array (VLBA) observations at 1.7 GHz strongly support this conclusion, showing six compact cores with similar low-frequency radio spectra. B1359+154 is the first example of galaxy-scale gravitational lensing in which more than four images are observed of the same background source. The configuration is due to the unique lensing mass distribution: three primary lens galaxies lying on the vertices of a triangle separated by 07 4 h-1 kpc, inside the 17 diameter Einstein ring defined by the radio images. The gravitational potential has additional extrema within this triangle, creating a pair of central images that supplement the standard four-image geometry of the outer components. Simple mass models, consisting of three lens galaxies constrained by HST and VLBA astrometry, naturally reproduce the observed image positions but must be finely tuned to fit the flux densities.