Katharina Immer

 

An average star formation rate for the Central Molecular Zone

Schuller, Frederic; Omont, Alain; Menten, Karl M.

 

We present a study of young objects (YSOs and HII regions) in the Central Molecular Zone (CMZ), selected from the ISOGAL and MSX source catalogues. Selection criteria based on the ISOGAL [7]-[15] color and a spatial extent parameter can reliably distinguish between young and late-type evolved objects. These criteria were tested and refined on a sample of 68 ISOGAL sources, for which we obtained Spitzer/IRS spectra. Based on the observed spectral features, we classified them as young objects or late-type evolved objects. We applied the refined criteria to all ISOGAL sources within 3 deg2 of the Galactic Center, selecting 485 sources. 656 MSX sources with flux density ratios FE/FD ≥ 2 in the E and D bands were added to the young source candidate list. We estimated the masses of our sources from the extinction corrected flux densities at 15 μm. The mass distribution roughly follows a Salpeter initial mass function. We computed an average star formation rate of 0.08 Myr−1 over the last 1 Myr for the CMZ.