Spitzer Space Telescope - General Observer Proposal #50598


IRS Spectral Maps of Photoevaporative Columns in M16, Carina, and the Galactic
Center

Principal Investigator: Angela  Cotera
           Institution: SETI

     Technical Contact: Angela  Cotera, SETI

Co-Investigators: 
Susan Stolovy, Spitzer Science Center                                 
Janet Simpson, NASA Ames Research Center                              
Kris Sellgren, University of Ohio                                     
Jeff Hester, Arizona State University                                 
Kevin Healy, Arizona State University                                 

Science Category: HII regions 
 Observing Modes: IrsMap 
  Hours Approved: 22.8 

Abstract:
Photoevaporated columns of dust and gas - also called elephant trunks, pillars
or fingers - are found in the periphery of H II regions, and have been observed
within the Galaxy, the SMC and the LMC. These features are sites of current star
formation, but the question remains whether the columns persist because stars
formed in the denser regions prior to interactions with the UV radiation and
stellar winds of nearby massive stars, or because of core collapse resulting
from these interactions. Mapping the distribution of the physical states of the
dust and gas in these columns is a necessary step towards understanding the
possible star formation mechanisms within these dynamic objects. We propose to
obtain IRS spectral maps of columns within M 16, the Carina nebula, and the
Galactic center (GC) to understand the effects on these pillars from different
stellar populations and initial conditions, and to better understand star
formation in the GC. Within the spectral range of the high resolution IRS modes
(9.9-37.2 micron) there are a wealth of molecular, atomic and PAH emission lines
that will enable us to determine the excitation state, dust and gas
temperatures, and probe the shock characteristics within the columns. Using the
IRS spectral mapping mode, in conjunction with the CUBISM tool and the CLOUDY H
II region model code, we will be able to construct detailed maps of the
accessible emission lines and derived parameters for each column. IRS mapping of
elephant trunks has not been done to date, yet provides a wealth of information
unobtainable for the foreseeable future once Cycle 5 is completed.