Dr. Feldmeier will search for diffuse light between the galaxies within several galaxy groups. This light is probably that of stars torn from the galaxies as their orbits within the group bring them close to one another. Very deep images will be obtained with the Burrell Schmidt, a 0.6-meter telescope that has been specially adapted for deep exposures covering 1.5 degrees across on the sky, or 3 times the diameter of the full moon. Images in a narrow bandpass that picks out the green light of the OIII line will be used to find planetary nebulae. These objects represent the final stage in the life of a sunlike star, as it blows off its outer layers; the ejected gas is ionized by the star's hot core, and shines brightly in the OIII line. The team will then take spectra with larger telescopes to confirm that objects that appear bright at the wavelength of the survey bandpass really are planetary nebulae, to find their radial velocities, and to explore the other chemical elements present in the gas. In preparation for surveys with new large imagers such as the One-Degree Imager (ODI) that is now being built for the 3.5-meter WIYN telescope, Dr Feldmeier will use smaller telescopes to calibrate dense fields of standard stars in one-degree patches in different areas of the sky. With these it will be possible to calibrate ODI 'in one shot' rather than taking many images to place a single standard star successively on the 64 independent elements of the imager.
Dr. Feldmeier's institution, Youngstown State University, is an undergraduate institution; he will involve undergraduate students in both astronomical and technical aspects of the research. The standard-star data for the one-degree calibration fields will be released to the community, to be used in other large-field imaging projects. Youngstown State University has a 145-seater planetarium, with software allowing users to design and render their own shows. The PI will produce all-dome videos to illustrate diffuse light between the galaxies in galaxy groups and clusters, and will release those to other planetaria.
This project focused on the study of intragroup stars, stars that lie between galaxies in galaxy groups. These stars come from galaxy interactions, where the force of gravity pulls these stars out of their home galaxies to drift in the space between the galaxies. These stars have been predicted to occur in models of galaxy formation, but are very hard to observe. Over the grant period, several galaxy groups and a galaxy cluster were observed using three different telescopes. We have searched the M101 and M96 groups of galaxies, and found very little (less than 3%) stars in an intragroup component. This result is in conflict with some theories of intragroup stars, and will require further study. Using the same observing techniques, the astronomers of this grant also studied a very distant type of galaxy, called a Lyman-alpha galaxy. These galaxies are believed to be the progenitor of our own Milky Way galaxy, but little is still known about them. This project searched for gas around these galaxies in a halo that surrounds the stars of these objects. This is very difficult, because these halos are very faint, and there are instrumental complications that make them hard to search for. In one sample, we found evidence of gas around Lyman-alpha galaxies, and in two other samples we did not. In addition to our science results, we also created a digital planetarium show for the general public and K-12 classrooms about these stars outside galaxies. This planetarium show, called Cosmic Castaways, is now available for free in 75 institutions in 27 US states, and in 17 countries, and can be viewed for free on YouTube. The planetarium show is also available in Spanish and a teacher's guide has been created for educators to use.
