Spitzer Space Telescope - Guaranteed Time Observer Proposal #50244


IRAC imaging of Protocluster AFGL 5157 (NH3)

Principal Investigator: Giovanni Fazio
           Institution: Harvard-Smithsonian Astrophysical Observatory

     Technical Contact: Jiasheng Huang, CfA

Co-Investigators: 
Ji Yang, Purple Mountain Obs.                                         
Yiping Ao, Purple Mountain Obs.                                       
Yafeng Chen, Purple Moutain Obs.                                      
Ruiqing Mao, Purple Moutain Obs.                                      

Science Category: young stellar objects 
 Observing Modes: IracMap 
  Hours Approved: 2.4 

Abstract:
Formation of star in groups and/or clusters is one of the most important but
unanswered questions in the study of galactic star formation. AFGL 5157 (NH3) is
a unique case undergoing present cluster formation, as proved by the following
key facts: (1), There is no detectable NIR point source within the loci of dense
NH3 core, known from recent ground-base NIR imaging but a radio continuum source
and some H2O masers were found within the core. (2) Within the NH3 core,
multiple H2 jets have been found and about 10 protostellar objects are
responsible for the jets; (3), NMA and SMA detected 14 dust continuum point
sources at 3sigma level of 2 mJy/beam. (4) High-resolution CO imaging at NMA
found a collimated CO jet well matching one of the major NIR H2 jet. In this
study, we propose to observe AFGL 5157 (NH3) by IRAC deep Imaging, Our major
purposes are as following: (1), To detect the cluster by IRAC and to conduct
photometry and to establish the SED of Class 0/1 objects. (2) To build the
luminosity function of the cluster, which, combined with the ground-base
observations on the distribution of protostellar members, should be able to
provide, the first of its kind, luminosity function of a cluster under
formation. (3), To make deep imaging for the jets and outflows within the
region. The results will provide crucial information to locate the evolutionary
status of each cluster member.