Objectives & Methodology:

We aim to identify formerly unknown quasars from select databases, using

previously known techniques that have been slightly modified. Similar work has been done using color-color diagrams. A color-color diagram is an x-y plot of one

color versus another of a set of sky objects. These diagrams are useful

because they separate out these sky objects based on the different

characteristics they possess, thus they enable us to sift out the quasars from the stars. Below is an example of a color-color

diagram, with known and speculated quasars:

Previous work done in the optical range suffered from low optical efficiency of

objects with redshifts 2-3. Such surveys are more efficient when done in the

infrared.

After selecting quasar candidates, we must then verify if they are indeed

quasars using spectroscopic analysis. We then discard any objects which are not

quasars.

Introduction:Quasi-stellar objects also known as

quasars are extremely distant and bright active nuclei of young galaxies. They are

powered by accretion of matter into massive black holes. Quasars were first

discovered in the middle of the last century and provide interesting insights into the nature of the cosmos and the

history of our universe.

Background:

What are the bases for classification of objects in the sky?

Morphology: This refers to the shape, size, and general physical

characteristics of cosmological objects.

Magnitude: Magnitude is a measure of the amount of flux in a particular wavelength range which is received

from the object.

Color: Color refers to the ratio of the magnitudes of flux received from one

bandwidth to another.

Spectroscopy: Spectroscopy in astronomy involves looking at the light emitted from an object and separating

this light into its constituents in the electromagnetic spectrum. Studying spectra of objects is often the most

decisive way to classify an object. An object’s spectra can provide

information about its constituents (gases it contains), its temperature, its

speed of recession (red shift), and it can even give insights into the

material contained in the spaces between the object and us.

Acknowledgements:

I would like to thank my mentor, Dr. Julia Kennefick, for her patience in helping me understand the project

material; my project partner, Ashley Stewart, whose reassuring words kept me sane when huge

piles of data nearly drove me to the edge, and lastly; 2-MASS & SDSS, for providing the data used in this

work.

Future Work:

We have been granted some observatory time in the fall at the Kitt peak observatory at Tucson, Arizona. At the observatory, we

will take the spectra of each of our candidates, and from the spectra

we will determine if they are indeed quasars, stars, or some

other object. Below are samples of the spectra of typical quasars and

stars, which show some of the distinct features of each of these

objects’ spectra, and their differences:

Improving Quasar Selection Methods. By: Kenechukwu C. Obi, Grinnell College, Iowa Mentor: Dr. Julia Kennefick.

University of Arkansas, Fayetteville

Star Spectrum

Quasar Spectrum