Jose A. Munoz

Ubvri light curves of 44 type ia supernovae

We present UBVRI photometry of 44 Type Ia supernovae (SNe Ia) observed from 1997 to 2001 as part of a continuing monitoring campaign at the Fred Lawrence Whipple Observatory of the Harvard-Smithsonian Center for Astrophysics. The data set comprises 2190 observations and is the largest homogeneously observed and reduced sample of SNe Ia to date, nearly doubling the number of well-observed, nearby SNe Ia with published multicolor CCD light curves. The large sample of U-band photometry is a unique addition, with important connections to SNe Ia observed at high redshift. The decline rate of SN Ia U-band light curves correlates well with the decline rate in other bands, as does the U - B color at maximum light. However, the U-band peak magnitudes show an increased dispersion relative to other bands even after accounting for extinction and decline rate, amounting to an additional ~40% intrinsic scatter compared to the B band.

The castles project

We describe the goals of the CASTLES (CfA-Arizona-Space-Telescope-LEns-Survey) project including a sample of NICMOS images of gravitational lenses and a brief list of the preliminary findings.

MGC 2214+3550: A New Binary Quasar

We report the discovery of a binary quasar, MGC 2214+3550A,B, whose components have similar optical spectra at a redshift of z=0.88. The quasars are separated on the sky by 30 and have a magnitude difference of ΔmI=0.5 mag. The VLA radio map at 3.6 cm shows a single 47 mJy radio source with a core-jet morphology that is coincident with the brighter optical quasar A. Gravitational lensing is ruled out by the lack of radio emission from quasar B and the lack of any visible galaxies to act as the lens. We conclude that MGC 2214+3550A and B are physically associated. With a projected separation of 12.7 h−1 kpc (Ω0=1), MGC 2214+3550A,B is one of the smallest z>0.5 binary quasars.

The Detection of the λ2175 Feature and Further Analysis of the Broad Absorption Line Profile Structure in the Gravitational Lens Candidate UM 425

We obtained Multiple Mirror Telescope spectra of the gravitational lens candidate UM 425 to compare the redshifts and line profile structures of lens components A and B, which are separated by approximately 65. The C IV λ1550 emission in both A and B exhibits broad absorption line (BAL) structure, consistent with the earlier detection of BAL structure in O VI λ1033 and N V λ1240 that was found with the International Ultraviolet Explorer in component A. Cross-correlation of the spectra of A and B using emission lines of C IV λ1550, He II λ1640, N III λ1750, C III] λ1909, and Mg II λ2800 reveals a difference in the redshifts of A and B. However, the detailed BAL profile structure found in the spectra of A and B are strikingly similar to one another, which suggests the system is lensed. The spectra of A and B also indicate significant dust extinction, which we base on the presence of the λ2175 absorption feature in the rest frame of the QSO (zQSO=1.47). This feature is commonly seen in galactic sources but is not generally observed in QSO spectra. Our spectra show the presence of the λ2175 absorption feature in spectra of both images associated with the gravitational lens UM 425. Based upon the strong similarity of BAL profile structure exhibited by UM 425A and UM 425B, particularly the presence of the λ2175 dust absorption feature in spectra of both images, we conclude that UM 425 is a gravitational lens.

Gravitationally Lensed Quasar Host Galaxies

Gravitational lensing improves the contrast of a quasar host galaxy because the extended emission is stretched away from the nucleus at constant surface brightness. As a result, the lensing technique is sensitive to low luminosity hosts at high redshift, using samples that are unlikely to be biased by host galaxy properties. In data from the CASTLES project, lensed host light is detected in roughly 2/3 of the cases. Hosts of radio-quiet quasars have modest luminosity (L < L*) at z ~ 2, and they are 2-5 times fainter than hosts of radio-loud quasars at the same epoch. The comparison with low redshift, radio-quiet hosts suggests rapid early growth of quasar black holes.