We present and use new spectra and narrow-band images , along with previously published broad-band images , of stars in the Arches cluster to extract photometry , astrometry , equivalent width , and velocity information .
The data are interpreted with a wind/atmosphere code to determine stellar temperatures , luminosities , mass-loss rates , and abundances .
We have doubled the number of known emission-line stars , and we have also made the first spectroscopic identification of the main sequence for any population in the Galactic Center .
We conclude that the most massive stars are bona-fide Wolf-Rayet ( WR ) stars and are some of the most massive stars known , having M _ { initial } > 100 M _ { \odot } , and prodigious winds , \dot { M } > 10 ^ { -5 } M _ { \odot } yr ^ { -1 } , that are enriched with helium and nitrogen ; with these identifications , the Arches cluster contains about 5 % of all known WR stars in the Galaxy .
We find an upper limit to the velocity dispersion of 22 km s ^ { -1 } , implying an upper limit to the cluster mass of 7 ( 10 ^ { 4 } ) M _ { \odot } within a radius of 0.23 pc ; we also estimate the bulk heliocentric velocity of the cluster to be v _ { cluster, \odot } \approx + 95 km s ^ { -1 } .
Taken together , these results suggest that the Arches cluster was formed in a short , but massive , burst of star formation about 2.5 \pm 0.5 Myr ago , from a molecular cloud which is no longer present .
The cluster happens to be approaching and ionizing the surface of a background molecular cloud , thus producing the Thermal Arched Filaments .
We estimate that the cluster produces 4 ( 10 ^ { 51 } ) ionizing photons s ^ { -1 } , more than enough to account for the observed thermal radio flux from the nearby cloud , 3 ( 10 ^ { 49 } ) ionizing photons s ^ { -1 } .
Commensurately , it produces 10 ^ { 7.8 } L _ { \odot } in total luminosity , providing the heating source for the nearby molecular cloud , L _ { cloud } \approx 10 ^ { 7 } L _ { \odot } .
These interactions between a cluster of hot stars and a wayward molecular cloud are similar to those seen in the “ Quintuplet/Sickle ” region .
The small spread of formation times for the known young clusters in the Galactic Center , and the relative lack of intermediate-age stars ( \tau _ { age } =10 ^ { 7.0 } to 10 ^ { 7.3 } yrs ) , suggest that the Galactic Center has recently been host to a burst of star formation .
Finally , we have made new identifications of near-infrared sources that are counterparts to recently identified x-ray and radio sources .