Young Stellar Objects in the Massive Star Forming Region W49
  We present the initial results of our investigation of the star-forming
complex W49, one of the youngest and most luminous massive star forming regions
in our Galaxy. We used Spitzer/Infrared Array Camera (IRAC) data to investigate
massive star formation with the primary objective to locate a representative
set of protostars and the clusters of young stars that are forming around them.
We present our source catalog with the mosaics from the IRAC data. In this
study we used a combination of IRAC, MIPS, Two Micron All Sky Survey (2MASS)
and UKIRT Deep Infrared Sky Survey (UKIDSS) data to identify and classify the
Young Stellar Objects (YSOs). We identified 232 Class 0/I YSOs, 907 Class II
YSOs, and 74 transition disk candidate objects using color-color and
color-magnitude diagrams. In addition, to understand the evolution of star
formation in W49 we analysed the distribution of YSOs in the region to identify
clusters using a minimal spanning tree method. The fraction of YSOs that belong
to clusters with >7 members is found to be 52% for a cut-off distance of 96"
and the ratio of Class II/I objects is 2.1. We compared the W49 region to the
G305 and G333 star forming regions and concluded that the W49 has the richest
population with 7 subclusters of YSOs.
