Focusing Cosmic Telescopes: Quantifying the Systematics of Strong Lensing Mass Models in the Era of Precision Lensing

Massive galaxy clusters are capable of magnifying background sources and thus act as natural telescopes to the distant Universe. My dissertation focuses on modeling the mass distributions of these clusters in order to determine to what degree intrinsic properties of background sources such as luminosity, star formation rate, and size have been magnified. With accurate and precise lens models, we can compute the luminosity functions of the most distant galaxies at z > 8, pushing beyond the limits of HST deep fields, which will help to understand the formation of galaxies during the epoch of re-ionization. We can also use cluster lensing to zoom into galaxies at z ~ 2 to study their star formation morphologies on scales smaller than a kiloparsec, science that will not be feasible for field galaxies until JWST comes online. In addition to creating lens models, my dissertation also looks at the systematic errors associated with lens modeling techniques. As I will show, lens model accuracy can depend on the number of constraints as well as the availability of spectroscopic redshifts used in the modeling process. Understanding the systematic errors of lens models will be necessary in the next decade, when several wide-field surveys will reveal thousands of new strong lensing systems, for which higher resolution imaging and spectroscopic data may not be obtained for all systems.PHDAstronomy and AstrophysicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/144156/1/tljohn_1.pd

The Impact of Future Orientation on the Avoidance of Teen Pregnancy

This study explores the relationship between future orientation and teens’ attitudes about pregnancy and avoidance behaviors. Participants were 91 adolescents, ages 15-19, surveyed using measures developed for this study that examined future orientation, attitudes to avoiding pregnancy, child-rearing responsibility, and perceptions about teen parenting. The results suggested that finishing high school was important in predicting a desire to avoid pregnancy. The perception that a teen pregnancy would make it difficult to achieve post-high school educational goals, specifically a college education, was also found to be important. Implications for school counselors and mental health professionals are discussed. Issues specific to non college-bound students are addressed

The Mass Distribution of the Strong Lensing Cluster SDSS J1531+3414

We present the mass distribution at the core of SDSS J1531+3414, a strong-lensing cluster at z=0.335. We find that the mass distribution is well described by two cluster-scale halos with a contribution from cluster-member galaxies. New HST observations of SDSS J1531+3414 reveal a signature of ongoing star formation associated with the two central galaxies at the core of the cluster, in the form of a chain of star forming regions at the center of the cluster. Using the lens model presented here, we place upper limits on the contribution of a possible lensed image to the flux at the center region, and rule out that this emission is coming from a background source.Comment: 8 pages, 5 figures; Submitted to Ap