H2 Pure Rotational Lines in the Orion Bar

  title={H2 Pure Rotational Lines in the Orion Bar},
  author={Katelyn Allers and Daniel T. Jaffe and John H. Lacy and Bruce T. Draine and Matthew J. Richter},
  journal={The Astrophysical Journal},
Photodissociation regions (PDRs), where UV radiation dominates the energetics and chemistry of the neutral gas, contain most of the mass in the dense interstellar medium of our Galaxy. Observations of H2 rotational and rovibrational lines reveal that PDRs contain unexpectedly large amounts of very warm (400-700 K) molecular gas. Theoretical models have difficulty explaining the existence of so much warm gas. Possible problems include errors in the heating and cooling functions or in the… Expand
The Orion Bar is one of the nearest and best-studied photodissociation or photon-dominated regions (PDRs). Observations reveal the presence of H2 lines from vibrationally or rotationally excitedExpand
SPIRE spectroscopy of the prototypical Orion Bar photodissociation region
Aims: We present observations of the Orion Bar photodissociation region (PDR) obtained with the SPIRE instrument on-board Herschel. Methods: We obtained SPIRE Fourier-transform spectrometer (FTS)Expand
We present H I 21 cm observations of the Orion Nebula, obtained with the Karl G. Jansky Very Large Array, at an angular resolution of 7.''2 Multiplication-Sign 5.''7 and a velocity resolution of 0.77Expand
ISO observation of molecular hydrogen and fine-structure lines in the photodissociation region IC 63
We wish to constrain the main physical properties of the photodissociation region (PDR) IC 63. We present the results of a survey for the lowest pure-rotational lines of H_2 with the Short WavelengthExpand
Structure of photodissociation fronts in star-forming regions revealed by observations of high-J CO emission lines with Herschel.
A comprehensive view of the modeling of the CO rotational ladder in PDRs, including the high-J lines that trace warm molecular gas at PDR interfaces, finds that the gas thermal pressure increases with the intensity of the UV radiation field given by G0, following a trend in line with recent simulations of the photoevaporation of illuminated edges of molecular clouds. Expand
OH emission from warm and dense gas in the Orion Bar PDR
As part of a far-infrared (FIR) spectral scan with Herschel/PACS, we present the first detection of the hydroxyl radical (OH) towards the Orion Bar photodissociation region (PDR). Five OH (X 2 Π; ν =Expand
TEXES Observations of Pure Rotational H2 Emission From AB Aurigae
We present observations of pure rotational molecular hydrogen emission from the Herbig Ae star, AB Aur. Our observations were made using the Texas Echelon Cross Echelle Spectrograph (TEXES) at theExpand
Excitation of Molecular Hydrogen in the Orion Bar PhotodissociationRegion from a Deep Near-infrared IGRINS Spectrum
We present a deep near-infrared spectrum of the Orion Bar Photodissociation Region (PDR) taken with the Immersion Grating INfrared Spectrometer (IGRINS) on the 2.7 m telescope at the McDonaldExpand
Herschel Search for O2 toward the Orion Bar
We report the results of a search for molecular oxygen (O-2) toward the Orion Bar, a prominent photodissociation region at the southern edge of the HII region created by the luminous Trapezium stars.Expand
A Low-Mass H2 Component to the AU Microscopii Circumstellar Disk
We present a determination of the molecular gas mass in the AU Microscopii circumstellar disk. Direct detection of a gas component to the AU Mic disk has proven elusive, with upper limits derivedExpand


HCN and HCO+ images of the Orion Bar photodissociation region
The Orion Bar is an ideal astrophysical laboratory for studying photodissociation regions because of its nearly edge-on orientation in the observer's line of sight. High angular resolution (~9'')Expand
Detection of low-J pure-rotational emission from H2 in the Orion Bar region - Evidence for small-scale clumpiness
The paper presents the results of a mapping of a 10 x 16 arcsec area in the vicinity of the Orion Bar ionization front, in the v = 0 J = 3{minus}1 and J = 4{minus}2 emission lines of molecularExpand
Kinetic temperatures in the Orion Bar
We report the detection of the (J,K) = (1, 1), (2, 2) and (4, 4) inversion lines of ammonia towards the Photo Dissociation Region (PDR) of the Orion Bar. The NH3 emission is found in the sameExpand
Anatomy of the Photodissociation Region in the Orion Bar
The results strongly support the theoretical models and show conclusively that the incident far-ultraviolet radiation field, not shocks as has sometimes been proposed, is responsible for the emission in the Orion Bar. Expand
Dense Molecular Clumps in the Orion Bar Photon-dominated Region
We present high angular resolution observations of the Orion Bar photon-dominated region (PDR) in optically thin H13CN and H13CO+ (1-0) lines, obtained using the IRAM Plateau de Bure interferometer.Expand
Line emission from clumpy photodissociation regions
A theoretical parameter study of dense photodissociation regions is presented. It is found that when the gas density is sufficiently high relative to the FUV flux, self-shielding of the molecules canExpand
Carbon Radio Recombination Lines in the Orion Bar
We have carried out VLA D-array observations of the C91α carbon recombination line as well as Effelsberg 100 m telescope observations of the C65α line in a 5' square region centered between the OrionExpand
Anatomy of a Photodissociation Region: High angular resolution images of molecular emission in the Orion Bar
We present observations of the molecular component of the Orion Bar, a prototypical Photodissociation Region (PDR) illuminated by the Trapezium cluster. The high angular resolution (6 sec-10 sec)Expand
Excitation of H_2 and HD in shocks and PDRs
Photodissociation regions (PDRs) and shocks give rise to conspicuous emission from rotationally and vibrationally excited molecular hydrogen. This line emission has now been studied with ISO and fromExpand
Some empirical estimates of the H 2 formation rate in photon-dominated regions
We combine recent ISO observations of the vibrational ground state lines of H 2 towards Photon-Dominated Regions (PDRs) with observations of vibrationally excited states made with ground–basedExpand