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Title: Irradiated interfaces in the Ara OB1, Carina, Eagle Nebula, and Cyg OB2 massive star formation regions

Regions of massive star formation offer some of the best and most easily-observed examples of radiation hydrodynamics. Boundaries where fully-ionized H II regions transition to neutral/molecular photodissociation regions (PDRs) are of particular interest because marked temperature and density contrasts across the boundaries lead to evaporative flows and fluid dynamical instabilities that can evolve into spectacular pillar-like structures. Furthermore, when detached from their parent clouds, pillars become ionized globules that often harbor one or more young stars. H2 molecules at the interface between a PDR and an H II region absorb ultraviolet light from massive stars, and the resulting fluoresced infrared emission lines are an ideal way to trace this boundary independent of obscuring dust. This paper presents H2 images of four regions of massive star formation that illustrate different types of PDR boundaries. The Ara OB1 star formation region contains a striking long wall that has several wavy structures which are present in H2, but the emission is not particularly bright because the ambient UV fluxes are relatively low. In contrast, the Carina star formation region shows strong H2 fluorescence both along curved walls and at the edges of spectacular pillars that in some cases have become detached from theirmore » parent clouds. The less-spectacular but more well-known Eagle Nebula has two regions that have strong fluorescence in addition to its pillars. And while somewhat older than the other regions, Cyg OB2 has the highest number of massive stars of the regions surveyed and contains many isolated, fluoresced globules that have head–tail morphologies which point towards the sources of ionizing radiation. Our images provide a collection of potential astrophysical analogs that may relate to ablated interfaces observed in laser experiments of radiation hydrodynamics.« less
Authors:
 [1] ;  [1] ;  [2]
  1. Rice Univ., Houston, TX (United States). Physics and Astronomy Dept.; NOAO Observatories, Tucson, AZ (United States)
  2. Univ. of Michigan, Ann Arbor, MI (United States). Astronomy Dept.
Publication Date:
Grant/Contract Number:
NA0000904
Type:
Published Article
Journal Name:
High Energy Density Physics
Additional Journal Information:
Journal Volume: 8; Journal Issue: 4; Journal ID: ISSN 1574-1818
Publisher:
Elsevier
Research Org:
Rice Univ., Houston, TX (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; radiation hydrodynamics; laboratory astrophysics; astronomical images; photodissociation regions
OSTI Identifier:
1209600
Alternate Identifier(s):
OSTI ID: 1334723