The Photodissociation and Ionization Fronts in M17-SW Localized with FIFI-LS on Board SOFIA

To understand star formation rates, studying feedback mechanisms that regulate star formation is necessary. The radiation emitted by nascent massive stars play a significant role in feedback by photodissociating and ionizing their parental molecular clouds. To gain a detailed picture of the physical processes, we mapped the photodissociation region (PDR) M17-SW in several fine-structure and high-J CO lines with FIFI-LS, the far-infrared imaging spectrometer aboard SOFIA. An analysis of the CO and [O i]146 μm line intensities, combined with the far-infrared intensity, allows us to create a density and UV intensity map using a one-dimensional model. The density map reveals a sudden change in the gas density crossing the PDR. The strengths and limits of the model and the locations of the ionization and photodissociation front of the edge-on PDR are discussed.

[1]  W. Vacca,et al.  Probing the Atmospheric Precipitable Water Vapor with SOFIA. II. Atmospheric Models from ECMWF , 2021, Publications of the Astronomical Society of the Pacific.

[2]  H Germany,et al.  Probing the Atmospheric Precipitable Water Vapor with SOFIA, Part I, Measurements of the Water Vapor Overburden with FIFI-LS , 2021, Publications of the Astronomical Society of the Pacific.

[3]  Randolf Klein,et al.  Uncertainty Propagation in (Gaussian) Convolution , 2021 .

[4]  W. Vacca,et al.  FIFI-LS Observations of the Circumnuclear Ring— Probing the High-density Phase of the PDR , 2019, The Astrophysical Journal.

[5]  W. Lim,et al.  Surveying the Giant H ii Regions of the Milky Way with SOFIA. I. W51A , 2019, The Astrophysical Journal.

[6]  E. Feigelson,et al.  Kinematics in Young Star Clusters and Associations with Gaia DR2 , 2018, The Astrophysical Journal.

[7]  Felix Rebell,et al.  Observing with FIFI-LS on SOFIA: time estimates and strategies to use a field imaging spectrometer on an airborne observatory , 2016, Astronomical Telescopes + Instrumentation.

[8]  K. Menten,et al.  Disentangling the excitation conditions of the dense gas in M17 SW , 2015, 1508.06699.

[9]  Bonn,et al.  Detection of a large fraction of atomic gas not associated with star-forming material in M17 SW , 2015, 1501.02735.

[10]  R. Chini,et al.  The Stellar Population of M17 , 2008 .

[11]  D. Hollenbach,et al.  [Si II], [Fe II], [C II], and H2 Emission from Massive Star-forming Regions , 2006 .

[12]  W. Goss,et al.  Broad Radio Recombination Lines from Hypercompact H II Regions , 2004 .

[13]  E. Feigelson,et al.  10 MK Gas in M17 and the Rosette Nebula: X-Ray Flows in Galactic H II Regions , 2003, astro-ph/0305133.

[14]  M. Burton,et al.  Formation pumping of molecular hydrogen in the messier 17 photodissociation region , 2001, astro-ph/0112174.

[15]  F. Bonnarel,et al.  The SIMBAD astronomical database. The CDS reference database for astronomical objects , 2000, astro-ph/0002110.

[16]  I. Howarth,et al.  The Young Massive Stellar Objects of M17 , 1997 .

[17]  Alexander G. G. M. Tielens,et al.  Dense Photodissociation Regions (PDRs) , 1997 .

[18]  S. Lord.  A new software tool for computing Earth's atmospheric transmission of near- and far-infrared radiation , 1992 .

[19]  A. Tielens,et al.  Far-infrared observations of M17SW - The clumpy structure of the photodissociation region , 1992 .

[20]  K. M. Merrill,et al.  Infrared Images of M17 , 1991 .

[21]  J. Stutzki,et al.  High spatial resolution isotopic CO and CS observations of M17 SW - The clumpy structure of the molecular cloud core , 1989 .

[22]  Gordon J. Stacey,et al.  Submillimeter and far-infrared line observations of M17 SW - A clumpy molecular cloud penetrated by ultraviolet radiation , 1988 .

[23]  V. Ossenkopf,et al.  GREAT : early science results Special feature L etter to the E ditor The ionized and hot gas in M 17 SW SOFIA / GREAT THz observations of [ C II ] and 12 CO J = 13 – 12 , 2012 .