We were awarded a total of 128 hours of time on the Gemini 8-meter telescope on Mauna Kea in Hawai'i, in semesters 2004A and 2005A, to search for these objects with the NIRI near-infrared imager. In 2004A, poor weather prevented us from obtaining the data, although we verified that the custom-made narrow-band filter designed by J.-D. Smith is working extremely well and that it provides a low-background window to the distant universe. In 2005A, we will image the Hubble deep field to search for Lyman alpha emission at z=8.227.
At present, I am analyzing both deep ground-based images of compact narrow emission line galaxies (CNELGs) and WFPC2 images of compact galaxies at intermediate redshift to determine the intrinsic shapes of these luminous compact objects. We are exploring the possibility that a large fraction of them are actually spiral bulges in formation.
In addition, Liese van Zee and I are using the WIYN 3.6-meter telescope on Kitt Peak and the 1.8-meter Lennon Telescope (VATT) on Mt. Graham to image over 1000 square arcminutes of sky. With deep exposures and the typically excellent seeing of the WIYN telescope (frequently sub-half-arcsecond in I), we plan to use photometric redshifts and detailed morphological information to measure the rate of in situ late-type bulge formation as a function of redshift for 0.4 < z < 1. We have an upcoming Keck run to obtain spectra of luminous compact galaxies identified in the WIYN survey.
As part of a number of new collaborations coming out of the Cosmology Group at UC Irvine, James Bullock and I, along with graduate students Joel Berrier and Heather Guenther, are beginning a comprehensive study of the merger rate and galaxy interactions using cosmological simulations and data in the nearby and distant universe. This work will build on my previous studies of galaxy pairs and galaxy interactions in the local universe.
In an ApJ article, Tidally-Triggered Star Formation in Close Pairs of Galaxies, Margaret Geller, Scott Kenyon, and I explore the match between star formation timescales and dynamical timescales in 502 galaxies in pairs. We have verified the correlations between the star-forming properties of interacting galaxies and their observable orbital parameters with an additional 200 paired galaxies; a subsequent independent study by Lambas et al. of the 2dF survey pairs reveals the same trends.
In a follow-up study, The Tully-Fisher Relation as a Measure of Luminosity Evolution: A Low-Redshift Baseline for Evolving Galaxies, we explore the ability of close galaxy-galaxy passes to trigger evolution and the effects of tidal distortion on the Tully-Fisher properties of galaxies. Sheila Kannappan and I continue the Tully-Fisher study in Tools for Identifying Spurious Luminosity Offsets in Tully-Fisher Studies: Application at Low Redshift and Implications for High Redshift
We explore the typical strengths and ages of bursts of star formation triggered by interaction with a large sample in Tidally-Triggered Star Formation in Close Pairs of Galaxies 2: Constraints on Burst Strengths and Ages. A LaTeX file with the full data table (Table 1) is available here . A second version with B-band absolute magnitudes added in a column immediately following the R-band absolute magnitudes is available here . In collaboration with S. Kannappan and R. Jansen, I also explore the relative frequency of galaxies with blue centers in the pairs survey and the Nearby Field Galaxy Survey in Forming Young Bulges within Existing Disks: Statistical Evidence for External Drivers.
My collaborators and I are currently extending these studies of the aggregate effects of interactions in the local universe in several ways, including:
We observed 4 nearby spiral galaxies with the Mosaic camera on the CTIO 4-meter telescope; we now have time on the new IMACS spectrograph at the Magellan 6.5-meter telescope to measure redshifts of faint galaxies in the environments of these spirals.