X-rays from the Local Bubble With Chandra: Observations of MBM 12

Richard J. Edgar, Randall Smith, Paul Plucinsky, Beth Biller (Smithsonian Astrophysical Observatory),


We present the results of a 100 ksec Chandra observation of MBM 12, a nearby ( $d~{}^{>}_{\sim}~90$ pc) molecular cloud. Snowden, McCammon & Verter (1993) used deep ROSAT PSPC observations of this cloud to measure the foreground 1/4 keV band emission from the Local Bubble. They also put strong upper limits on the foreground 0.5-1.0 keV (M-band) emission. Most, if not all, models for the Local Bubble predict that the emission in this bandpass is primarily due to O VII and O VIII lines. Chandra's ACIS detector has sufficient effective area to see this emission and enough resolving power to separate these two lines. These lines are diagnostics for the emission measure and age (ionization state) of the Local Bubble. Many statistical and systematic effects are considered, including: low energy ACIS quantum efficiency and redistribution functions; charged particle backgrounds; statistical biases.



Himel Ghosh