|
We present high angular resolution (beam of 0.4") interferometric observations
of several vibrationally excited transitions of HC3N (Eu=160 to 900 K) and
high excitation lines of SO2 (Eu=70 to 660 K) toward the massive star
forming region in Cepheus A HW2. In contrast with the idea that the
powering source of the HW2 radio jet is the most massive object in the
HW2 star cluster, our images of the vibrationally excited emission of HC3N
show that the recently reported hot core in the vicinity of HW2
(located 0.4" east the radio jet), is the main heating source in the region.
The derived HC3N rotational temperature is of 340 K and the radius of the
core, resolved in the HC3N v7=1 maps, is of 0.3". Assuming that the gas and
dust are thermally coupled, the estimated luminosity for this
source is of 2E4 Lo, consistent with the total luminosity measured toward HW2.
The high spectral resolution maps of the high excitation SO2 emission
also support this idea. The circumstellar disk around the radio jet
seems to rotate following a Keplerian law and has a velocity gradient
roughly of 5km/s, which implies a mass of 9 Mo and a luminosity of only
5E3 Lo for the HW2 powering source. This makes the hot and compact core
at 0.4" east HW2 the most luminous and massive object within the HW2 star
cluster. All this suggests a sequential scenario for which the most massive
and young objects within star clusters like that in Cepheus A HW2, are
formed as a consequence of previous episodes of formation of lower mass
stars within the same cluster.
|
