Unveiling the monsters: characterization of ultra-massive galaxies in the early universe with irac mapping of the nmbsii/cfhtls fields observations of massive galaxies and their evolution with…

This federal contract award, valued at $340,020.33, was granted by the National Aeronautics and Space Administration (NASA) to Trustees of Tufts College, doing business as Tufts University, a private research university located in Medford, Massachusetts. The award, titled "UNVEILING THE MONSTERS: CHARACTERIZATION OF ULTRA-MASSIVE GALAXIES IN THE EARLY UNIVERSE WITH IRAC MAPPING OF THE NMBSII/CFHTLS FIELDS," is for a research program focused on studying the properties and evolution of ultra-massive galaxies in the early universe. The program involves the analysis of newly acquired Spitzer Space Telescope Infrared Array Camera (IRAC) data, which will be integrated with existing data from the NMBS-II survey. This research aims to provide crucial insights into the formation and characteristics of the most massive galaxies in the cosmos. The award does not have a set-aside designation and is expected to be completed by October 20, 2020.

Unveiling the monsters: characterization of ultra-massive galaxies in the early universe with irac mapping of the nmbsii/cfhtls fields observations of massive galaxies and their evolution with cosmic time place strong constraints on the physical processes of galaxy formation. Although substantial data have been collected on galaxies with masses log(mstar/msun)~11.2 out to z~4-5 from the recent myriad of ground-based near-infrared (NIR) surveys, very little is known about the evolution of the most massive (log(mstar/ msun)>11.4) galaxies in the universe. At the tip of the schechter function, their space density is estimated to be 30X lower than log(mstar/msun)=11 galaxies and hence only a few have been found, even in the widest-field surveys. We recently undertook the nmbs-II survey, a wide-field NIR medium-band survey designed to accurately characterize the stellar mass function, number density, stellar population and clustering properties of the most massive galaxies out to z=3. The nmbs-II uses a set of five medium-bandwidth NIR filters to provide precise photometric redshifts and well-sampled spectral energy distributions (seds) of galaxies at z>1.5. The primary survey fields of the nmbs-II are the cfhtls-deep fields; however, presently only 60% of these fields have irac coverage. The irac data are essential for accurately measuring photometric redshifts and stellar masses of the highredshift population. Irac data are also critical for separating the red quiescent from the red, dusty star-forming galaxies at z>0.8. In cycle 10 (12/2013-10/2014), the PI marchesini was awarded 22 hours of spitzer time to complete the irac coverage of the nmbs-II fields, for a total area of 5.4 SQ. DEG. Over 7 independent lines of sight. This proposal describes a program consisting of three main components. First, the newly acquired irac data at 3.6 and 4.5 micron awarded to the PI to complete the irac coverage of the nmbs-II fields will be reduced. Second, the addition of the spitzer-irac and mips photometry to the nmbs-II k-selected catalogs will be completed. Third, a unique sample of ~300 ultra-massive galaxies (umgs; i.e., log(mstar/msun)>11.4, of which ~50 with log(mstar/msun)>11.6) with accurate photometric redshifts at 1.51.5, a population arguably representing the biggest problem in our understanding of galaxy formation. Specifically, the following outstanding questions will be answered: 1) what is the number density of umgs in the early universe? 2) are these "monster" galaxies still forming STARS and what is their quiescent fraction? 3) what are their stellar population properties? 4) what are their clustering and dark matter halo properties? 5) do they host agns? This research will provide crucial information that future theoretical models will have to reproduce. The findings will be compared to predictions from hierarchical galaxy formation models, providing critical feedback to improve and constrain currently implemented prescriptions for the baryonic physics. The synergistic collaboration with theorists will results in improved strategies for future observations optimized to better test the models and the implemented prescriptions. The reduced and mosaiced cycle 10 irac data will be publicly released 9 months from the start of the proposed program. The nmbsii multi-wavelength (UV-to-24 micron) photometric catalogs, and catalogs of photometric redshifts, stellar population parameters, restframe magnitudes and colors, and ultra-violet and infrared luminosities will be publicly released within 24 months after the beginning of the proposed program, providing the astronomy community with a very valuable dataset of ~210,000 galaxies down