Project Title: The masses, accretion efficiencies, and outflow properties of the biggest black holes in the universe

Faculty Sponsor: Rajib Ganguly

Department: CSEP

Telephone: 

E-Mail: ganguly@umflint.edu

Project Description: Quasars are point-like objects that emit ~10^44-10^48 erg/s 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 10^7-10^10 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 10^4-10^5 Rg. For reference, a 10^8 Msun black hole has Rg~1 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., CIV, NV, OVI). 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 10^3 to several 10^4 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? Do we see outflows only in highly-ionized species where we can only detect them in X-ray through optical wavelengths, or do the outflows also occur in molecular species where we could see them in the infrared? Invariably, these would have to occur in very different locations (ions closer to the black hole where light *can* create ions; molecule farther away where they could survive without being dissociated). How do these regimes relate to each other? Are they related to the mass of the black hole, or how quickly they accrete (as opposed to how efficiently)?

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., CIV, NV, OVI). 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 10^3 to several 10^4 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? Do we see outflows only in highly-ionized species where we can only detect them in X-ray through optical wavelengths, or do the outflows also occur in molecular species where we could see them in the infrared? Invariably, these would have to occur in very different locations (ions closer to the black hole where light *can* create ions; molecule farther away where they could survive without being dissociated). How do these regimes relate to each other? Are they related to the mass of the black hole, or how quickly they accrete (as opposed to how efficiently)?

Student Tasks & Responsibilities:  Starting with a sample of 11,000 quasars, the student will (1) identify which quasars have archival data at infrared, and ultraviolet wavelength, (2) download the appropriate data sets, (3) make measurements of how bright the objects are in all relevant bands, (4) construct composite spectra of subsamples of objects based on outflow properties, (5) measure the physical properties (black hole masses, accretion rate, and efficiencies) from those composites, and (6) identify empirical relationship between those measured and inferred properties.

Minimum Student Qualifications:  At minimum, the student must have a working knowledge of the UNIX or Linux operating system, and familiarity with the Perl scripting language. Additional knowledge of the Interactive Data Language (IDL) is preferred.

Proposed Starting Date: 02/25/2013

Proposed Ending Date: 04/30/2013