The Use of Infrared Color-Color Plots to Identify Rare Objects in the Galactic Mid-Plane

Jessica Fuselier

Dr. Robert Benjamin, advisor

GLIMPSE Survey

Spitzer Space Telescope survey of the Galactic Midplane

4 infrared bands : 3.6m, 4.5m, 5.8 m, 8.0m

Covers 220 square degrees of the sky.

Expect to find approximately 10 million point sources.

Why the infrared?

Much less extinction (due to interstellar dust), so you can see many more stars.

Good for finding cool or dusty/embedded objects (like protostars)

Colors in Astronomy

Why color-color plots?

• Can be used to identify and/or categorize objects by their colors

• Useful for identifying strange or unusual stars or celestial bodies; for example sub-stellar objects (“brown dwarfs”)

Why not?

Objectives

• To identify red objects in the survey, and examine them in more depth.

• To identify the properties of other objects with unusual colors as well!

Approach

For each catalog section of the GLIMPSE survey, make field areas and diffuse areas

Plot the entire catalog section, diffuse areas, and field areas

Select the reddest objects in the plot at two magnitude cuts

310 Full (4 square degrees) vs. 310 with Mag< 10

Warning: data artifact?

Comparing Regions with Diffuse Emission and the Field Populations 310 Diffuse C vs. 308 Field A

Looking at Bright Stars Only310 Diffuse C (Mag <12) vs. 308 Field A (Mag<12)

Follow-up work on red sources

Make source lists and “region files” (for overlay on image)

Find the actual source in the images using SAO Image ds9 to check for reality of source

Look for any matching IRAS sources

Run the galactic coordinates through SIMBAD to search for association with known objects

So Far…

10 objects identified as IRAS sources; one was also identified as a Radio Source using SIMBAD

Diffuse areas have more red objects than field areas

Field areas show the same red objects after a magnitude cut

Results are pending for the strangely colored objects

~860,000 sources to start with10 selected areas (3 field regions, 7 diffuse areas)250 red objects selected and verified

Acknowledgements

NASA and Spitzer Space Telescope

The GLIMPSE Team

Dr. Robert Benjamin

SAO Image ds9

IRAS

SIMBAD