Project Title: Spewing Black Holes: Outflows from the Biggest Black Holes in the Universe

Faculty Sponsor: Rajib Ganguly

Department: CSEP



Project Description: Quasars are point-like objects that emit ~10^{37-41} Watts of energy, and are considered the most luminous sustained phenomena in the universe. They have roughly uniform energy output per decade of wavelength to within factors of ten from the radio to X-rays. The best explanation for the compact morphology and massive energy output is that of an accreting supermassive (10^{7-10}) Msun black hole.

The gross similarities in spectral features implies that all quasars have the same basic physical structure. However, the variety in the details brings up the question: What governs that structure and how? The current working paradigm holds that the accreting gas takes the form of a disk. This disk extends from a few times the black hole gravitational radius (Rg=2GM/c^2), out to 10^{4-5 Rg. For reference, a 10^8 Msun black hole has Rg ~ 2 AU.

A mass outflow is thought to originate from the central regions of the accretion disk. It is important to understand these outflows as they potentially offer a means for the gas in the black-hole accretion disk to shed angular momentum allowing accretion to occur. Outflows may actually regulate the accretion process. These outflows are ionized and can be seen under certain viewing angles in ultraviolet resonant absorption (e.g., C IV, N V, O VI). Generally, this happens in about 60% of quasars over several decades of luminosity, though the form of the absorption does change. The absorption profiles produced by outflows can take a variety of forms: broad absorption lines (BALs) with widths of a few thousand to several tens-of-thousands km/s; narrow absorption lines (NALs) with widths of <500 km/s; and mini-BALs with velocity widths between those of BALs and NALs. The distribution of ejection velocities and velocity widths is continuous. The profiles can be smooth or discrete/clumpy and can appear at either high or low velocity with respect to the quasar redshift.

Several crucial questions need to be addressed in understanding the physics behind outflows. How efficiently do the black holes have to accrete in order to see outflows? Do we see them at all efficiencies, or are they at one end of the distribution? How do outflow affect the observed properties of these systems? Are they common, with structure governing whether they are observed, or are they a phase in a dynamically changing structure? How does that answer change with the properties of the black hole (mass, spin, accretion efficiency, etc)? How do different observed forms of outflows (BALs, NALs, etc) relate to each other? How do they change with black hole properties? Using the large database of a objects from the Sloan Digital Sky Survey, we are tackling these questions (and more!) with a deliberate, systematic, and (hopefully) automated search for outflows amongst accreting black holes. Using measurements of the outflow properties, we will search for clues through statistical analyses of how common these are as a function of quasar physical property.

Student Tasks & Responsibilities:  As part of the project, the student will learn how to search for outflows in a sample of ~11000 objects. In addition, the student will make measurements of outflow properties, assist in the development of computer code for automated detection and measurement making, with visual inspection for sanity-checking. The student will also compile this information along with quasar physical properties, and apply various statistical test to explore potential correlations, or hierarchical grouping of objects. The student will also provide weekly updates on progress to the research group, and also present results at both the UM-Flint Student Research Conference and Meeting of Minds.

Minimum Student Qualifications:  The student must be proficient in the UNIX/linux computer environment, as all the data is digital in nature, and software to be used is installed in the lab computers which use CentOS. In addition, the ability to write scripts (perl preferred, but other languages are reasonable) to handle large amounts of data is a plus.

Proposed Starting Date: 01/24/2014

Proposed Ending Date: 04/21/2014