0 Assigned ID: 921 ----- Attempting Submission 1 (Fri Apr 05 23:12:02 GMT 2019) ----- We propose a project to identify stellar counterparts for ~60 hyperluminous X-ray sources (HLXs) using archival HST imaging. HLXs are luminous, off-nuclear X-ray sources and represent candidate intermediate-mass black holes (IMBHs) in the nuclei of dwarf galaxies that have merged with a larger galaxy. They provide a unique avenue for studying the role of mergers for growing primordial black hole seeds and constraining seed formation mechanisms. HST is the only observational resource with the imaging resolution and sensitivity to detect the faint stellar counterparts associated with most HLXs. This project will yield the currently largest sample of HLXs with stellar counterpart detections, and we will use it to address the following primary science goals: constraining the fraction of contaminating (background or foreground) X-ray sources, measuring stellar counterpart masses and putting constraints on BH masses, and examining how mergers affect IMBH growth. The archival approach of this project will eliminate the burden on HST time while maximizing its contribution to the science of HLXs and IMBH candidates. Based on our preliminary results, the science yielded by this project will include stellar masses of ~60 HLX candidates, ~40 strong IMBH candidates, and unprecedented studies of merger-driven BH growth, including in mergers with large mass ratios that are difficult to otherwise identify. PI Barrows: Dr. Scott Barrows has significant experience working with multi-wavelength data of hyperluminous X-ray sources (HLXs), including NIR, optical, and X-ray imaging, all of which will be analyzed in this project. PI Barrows also has extensive experience modeling and analyzing the morphologies of galaxies imaged by HST, which will be the primary component of this project. PI Barrows will be responsible for the overall direction and success of the project. PI Barrows will be responsible for completing all analysis steps. This consists of assembling the dataset of HST imaging, the image modeling, and the overall scientific analysis. Co-I Comerford: Prof. Julia Comerford is an expert on studies of AGN, especially in the context of galaxy mergers. Co-I Comerford will assist in the overall direction of the project, and in the analysis and interpretation of the results. Co-I Mezcua: Dr. Mar Mezcua is an expert on observational properties and analysis of HLXs and intermediate-mass black holes. Co-I Mezcua will assist in the overall direction of the project, and in the analysis and interpretation of the results. Co-I Heida: Dr. Marianne Heida is an expert on observational properties and analysis of ultra-luminous X-ray sources, which observationally are very similar to those of HLXs. Co-I Heida will assist in the overall direction of the project, and in the analysis and interpretation of the results. Co-I Stern: Dr. Daniel Stern is an expert on multi-wavelength properties of active galactic nuclei, including the HST imaging and X-ray properties that will be analyzed in this project. Co-I Stern will assist in the overall direction of the project, and in the analysis and interpretation of the results. PI Barrows and Co-I Comerford have institutional access (through CU Boulder) to the Apache Point Observatory 3.5m telescope. This will be the facility used to obtain the spectroscopic redshifts of the sample created through this project. Massive Black Holes And Their Host Galaxies 0 Regular false false false false false SUPPORTED