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A multiwavelength study of the massive star-forming region IRAS 06055+2039 (RAFGL 5179)
Aims.We present a multiwavelength study of the massive star-formingregion associated with IRAS 06055+2039. Methods: .Narrow-bandnear-infrared (NIR) observations were carried out with UKIRT-UFTI inmolecular hydrogen and Brγ lines to trace the shocked and ionizedgases, respectively. We have used 2MASS {J H K}s data tostudy the nature of the embedded cluster associated with IRAS06055+2039. The radio emission from the ionized gas was mapped at 610and 1280 MHz using the Giant Metrewave Radio Telescope (GMRT), India.Emission from warm dust and the unidentified infrared bands (UIBs) wasestimated using the mid-infrared (8-21 μm) data from the MSX survey.Submillimetre emission from the cold dust at 450 and 850 μm wasstudied using JCMT-SCUBA. Results: .For the infrared clusterassociated with IRAS 06055+2039, we obtain a power-law slope of0.43±0.09 for the K_s-band luminosity function (KLF), which is ingood agreement with other young embedded clusters. We estimate an age of2-3 Myr for this cluster. Apart from the diffuse emission, thehigh-resolution 1280 MHz map also shows the presence of several discretesources that possibly represent high-density clumps. The morphology ofshocked molecular hydrogen forms an arc towards the N-E of the centralIRAS point source and envelopes the radio emission. Submillimetreemission shows the presence of a dense cloud core that is probably at anearlier evolutionary stage compared to the ionized region with shockedmolecular gas lying between the two. The total mass of the cloud isestimated to be 7000-9000 Mȯ from the submillimetreemission at 450 and 850 μm. Conclusions: .The multiwavelengthstudy of this star-forming complex reveals an interesting scenario whereregions are at different stages in the evolution of star formation.
| Near infrared imaging of NGC 2316
In the present paper we present JHK photometric results of the youngembedded cluster NGC 2316. We construct the cluster radial profile fromwhich we determine a radius of 0.63 pc. We find 189 ± 29 clustermembers in an extinction limited sub-sample of the survey, 22± 19of which are possibly substellar. An average extinction of 4.5 visualmagnitudes is derived using (H - K) colours of control fields. Thisextinction is due to the presence of residual parental molecular cloud.NGC 2316 presents 16% source fraction of excess emission which isconsistent with other results from clusters with an age of 2-3 Myr. Thisage is consistent with the distribution of sources in thecolour-magnitude diagram when compared to theoretical isochrones, andthe overall shape of the cluster KLF. The substellar population of thecluster is similar or smaller than that observed for other embeddedclusters and the stellar objects dominate the cluster membership.Based on observations carried out at ESO, La Silla, Chile.
| Merged catalogue of reflection nebulae
Several catalogues of reflection nebulae are merged to create a uniformcatalogue of 913 objects. It contains revised coordinates,cross-identifications of nebulae and stars, as well as identificationswith IRAS point sources.The catalogue is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/399/141
| Testing Models of Low-Excitation Photodissociation Regions with Far-Infrared Observations of Reflection Nebulae
This paper presents Kuiper Airborne Observatory observations of thephotodissociation regions (PDRs) in nine reflection nebulae. Theseobservations include the far-infrared atomic fine-structure lines of [OI] 63 and 145 μm, [C II] 158 μm, and [Si II] 35 μm and theadjacent far-infrared continuum to these lines. Our analysis of thesefar-infrared observations provides estimates of the physical conditionsin each reflection nebula. In our sample of reflection nebulae, thestellar effective temperatures are 10,000-30,000 K, the gas densitiesare 4×102-2×104 cm-3, thegas temperatures are 200-690 K, and the incident far-ultravioletintensities are 300-8100 times the ambient interstellar radiation fieldstrength (1.2×10-4 ergs cm-2 s-1sr-1). Our observations are compared with current theory forlow-excitation PDRs. The [C II] 158 μm to [O I] 63 μm line ratiodecreases with increasing incident far-ultraviolet intensity. This trendis due in part to a positive correlation of gas density with incidentfar-ultraviolet intensity. We show that this correlation arises from abalance of pressure between the H II region and the surrounding PDR. The[O I] 145 to 63 μm line ratio is higher (greater than 0.1) thanpredicted and is insensitive to variations in incident far-ultravioletintensity and gas density. The stellar temperature has little effect onthe heating efficiency that primarily had the value3×10-3, within a factor of 2. This result agrees with amodel that modifies the photoelectric heating theory to account forcolor temperature effects and predicts that the heating efficiencieswould vary by less than a factor of 3 with the color temperature of theilluminating field. In addition to the single-pointing observations, an[O I] 63 μm scan was done across the molecular ridge of one of oursample reflection nebulae, NGC 1977. The result appears to supportprevious suggestions that the ionization front of this well-studied PDRis not purely edge-on.
| H2 Line Ratios to Discriminate Dense Photodissociation Regions from Shocks: Application to NGC 2023 and NGC 7023
We measured the distribution of H2 line ratios, 2-1 S(1)/1-0S(1) and 4-2 S(1)/3-1 S(1), in typical dense photodissociation regions(PDRs) associated with the reflection nebulae, NGC 2023 and NGC 7023.The line images were obtained with a recently developed wide-field(3.9′x3.9′) Fabry-Perot imager, MUSE. In both objects, the2-1 S(1)/1-0 S(1) ratio varies spatially between 0.2 and 0.6 as a resultof the variation of gas density (n~105-106cm-3) and UV intensity(G0~103-104) in PDRs. On the otherhand, the 4-2 S(1)/3-1 S(1) ratio is nearly constant (~1) in bothobjects. This constancy of the 4-2 S(1)/3-1 S(1) ratio agrees with modelpredictions. Since the observed 4-2 S(1)/3-1 S(1) ratio is significantlylarger than the expected ratio for shock excitation, the 4-2 S(1)/3-1S(1) ratio is expected to discriminate both dense and diffuse PDRs fromshocks.
| Near-Infrared Spectroscopy of Molecular Hydrogen Emission in Four Reflection Nebulae: NGC 1333, NGC 2023, NGC 2068, and NGC 7023
This paper presents near-infrared spectroscopy of fluorescent molecularhydrogen (H2) emission from NGC 1333, NGC 2023, NGC 2068, andNGC 7023 and derives the physical properties of the molecular materialin these reflection nebulae. These observations of NGC 2023 and NGC 7023and the physical parameters derived for these nebulae are in goodagreement with previous studies. Both NGC 1333 and NGC 2068 have nopreviously published analysis of near-infrared spectra. This studyreveals that the rotational-vibrational states of molecular hydrogen inNGC 1333 are populated quite differently from NGC 2023 and NGC 7023. Wedetermine that the relatively weak UV field illuminating NGC 1333 is theprimary cause of the difference. Further, the density of the emittingmaterial in NGC 1333 is of much lower density, withn~102-104 cm-3. NGC 2068 has molecularhydrogen line ratios more similar to those of NGC 7023 and NGC 2023.Model fits to this nebula show that the bright, H2-emittingmaterial may have a density as high as n~105 cm-3,similar to NGC 2023 and NGC 7023. Our spectra of NGC 2023 and NGC 7023show significant changes in both the near-infrared continuum andH2 intensity along the slit and offsets between the peaks ofthe H2 and continuum emission. These brightness changes maycorrespond to real changes in the density and temperatures of theemitting region, although uncertainties in the total column of emittingmaterial along a given line of sight complicates the interpretation. Thespatial difference in the peak of the H2 and near-infraredcontinuum peaks in NGC 2023 and NGC 7023 shows that the near-infraredcontinuum is due to a material which can survive closer to the star thanH2 can.
| UNSWIRF: A tunable imaging spectrometer for the near-infrared
We describe the specifications, characteristics, calibration, andanalysis of data from the University of New South Wales InfraredFabry-Perot (UNSWIRF) etalon. UNSWIRF is a near-infrared tunable imagingspectrometer, used primarily in conjunction with IRIS on the AAT, butsuitable for use as a visitor instrument at other telescopes. The etalondelivers a resolving power in excess of 4000 (corresponding to avelocity resolution of about 75 km per sec), and allows imaging offields up to 100 microns in diameter on the AAT at any wavelengthbetween 1.5 and 2.4 microns for which suitable blocking filters areavailable.
| Molecular hydrogen line emission from the reflection nebula Parsamyan 18
The newly commissioned University of New South Wales InfraredFabry-Perot (UNSWIRF) has been used to image molecular hydrogen emissionat 2.12 and 2.25 microns in the reflection nebula Parsamyan 18. P 18 isknown to exhibit low values of the (1-0)/(2-1) S(1) ratio, suggestive ofUV-pumped fluorescence rather than thermal excitation by shocks. Ourline ratio mapping reveals the full extent of this fluorescent emissionfrom extended arclike features, as well as a more concentrated thermalcomponent in regions closer to the central exciting star. We show thatthe emission morphology, line fluxes, and gas density are consistentwith the predictions of photodissociation region (PDR) theory. Theregions with the highest intrinsic 1-0 S(1) intensities also tend toshow the highest (1-0)/(2-1) S(1) line ratios. Variations in the lineratio can be attributed to intrinsic fluctuations in the incidentradiation field and/or the gas density, through the self-shieldingaction of H2. An isolated knot of emission, discovered just outside P 18and having both an unusually high (1-0)/(2-1) S(1) ratio and relativevelocity, provides additional evidence for an outflow source associatedwith P 18.
| Near-Infrared Spectra of IC 59/63 and NGC 1535: Comparing Infrared and Ultraviolet Observations of H 2
We present observations of near-infrared H2 line emission toward thereflection/emission nebulae, IC 59 and IC 63, and the planetary nebula,NGC 1535. Each source has been observed previously in the ultraviolet,where H2 was detected in emission toward IC 63 and in absorption towardNGC 1535. In IC 63, we have detected the 1.601 mu m v = 6--4 Q(1), 2.121mu m v = 1--0 S(1), and 2.247 mu m v = 2--1 S(1) lines of H2 arisingfrom a near-infrared fluorescent cascade following ultraviolet continuumpumping. The detection marks the first time that both infrared andultraviolet portions of the H2 fluorescent cascade have been measured ina region exposed to far-ultraviolet continuum photons. Furthermore, wealso report 1--0 S(1) and 2--1 S(1) fluorescent emission toward IC 59, asource previously thought to display no H2 fluorescence and considereddevoid of molecules based on ultraviolet and CO observations. Toward NGC1535, we find no H2 emission in the near-infrared, in spite of thereported ultraviolet H2 absorption.
| A Survey of Near-Infrared Emission in Visual Reflection Nebulae
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJS..102..369S&db_key=AST
| Dusty Plasmas in Interstellar Clouds and Star Forming Regions
Not Available
| Time-dependent fluorescent H2 emission
We present computations of the time-dependent infrared fluorescentemission-line response of molecular hydrogen (H2) gas in interstellarclouds exposed to far-ultraviolet radiation fields. In clouds exposed tointense fields the H2 line intensities may be much larger at early timesimmediately following the onset of irradiation than under conditions ofstatic equilibrium. Time-dependent effects in evolving photon-dominatedregions may be important in the fluorescent H2 emitting regions inplanetary and reflection nebulae and possibly in starburst galaxies andactive galactic nuclei.
| A model of the 2-35 micron Point Source Infrared Sky
The Point Source Infrared Sky Model of Wainscoat et al. (1992) isextended to make predictions for any filter lying wholly within therange 2.0 to 35.0 micron. The development of a library of complete 2-35micron low-resolution spectra that represent the 87 categories ofGalactic object and four types of extragalactic source implicit in theModel supports this extension. This library is based upon the 'spectraltemplate' technique whereby existing spectral fragments for individualsources (from ground-based, airborne, and satellite-borne instruments)are combined into complete spectra. Templates provide a natural way torepresent the complete spectral energy distributions of celestialsources for which only infrared photometry and/or partial spectroscopyare available. Consequently, templates bear upon the important generalproblem of establishing midinfrared calibration sources. The new modelis validated by comparison with broadband K source counts.
| A quantitative study of the 7.7 and 11.3 micron emission bands based on IRAS/LRS spectra
A quantitative analysis of the emission bands at 7.7 and 11.3 microns inthe mid-IR spectra of HII regions, reflection nebulae, planetarynebulae, and galaxies is presented. The investigation is based on asample of 113 sources whose spectra have been extracted from theIRAS/LRS data base. Relations of the intensity of the emission bandswith physical conditions such as the excitation, and the relativecontributions of emission bands and continuum around 10 microns to themid-IR and FIR fluxes are presented and analyzed. A strong linearcorrelation is found between 7.7 and 11.3 micron band luminosities. Thegood correlation and the small dispersion (30 percent, compatible withthe measurement errors) confirm, on a sample of sources, that thecarriers of the 7.7 and 11.3 micron emission features belong to the samefamily, most likely aromatic molecular species such as PAH molecules.
| The H2 line profiles in the Cygnus Loop - Evidence for J-shocks with magnetic precursors
Infrared Fabry-Perot spectra at 25 km/s resolution have been obtainedfor the H2 line emission associated with the fast shocks to the NE ofthe Cygnus Loop supernova remnant. Profiles of the 1-0 S(1) H2 emissionassociated with both the optically bright radiative shocks and the faintnonradiative shocks have been observed. The profiles are resolved andhave deconvolved widths of 20 km/s. This result favors excitation of theH2 emission in a magnetic precursor over excitation by a radiativeprecursor. Shocks with precursors may play an important role inHerbig-Haro objects, and in star-forming cloud cores.
| H2 excitation by magnetic shock precursors in the Cygnus Loop supernova remnant
Emission from vibrationally excited H2 has been discovered which isassociated with the bright optical shock-excited filaments to thenortheast of the Cygnus Loop supernova remnant. Infrared spectroscopyand infrared and optical narrow-band images of the shock-excited gashave been obtained in an effort to understand the mechanism of H2excitation. A shock model with a magnetic precursor is proposed whichexplains quantitatively the observed H2 surface brightness, levelpopulation, and relation to optical emission. A shock with a magneticprecursor can also account for some of the anomalous properties ofnonradiative shocks.
| The excitation of 12 micron emission from very small particles
The results of IRAS observations of visual reflection nebulaeilluminated by stars with effective temperatures between 3000 and 33,000K are presented. The ratio of the energy radiated in the IRAS 12-micronsband to the total energy radiated at far-infrared wavelengths (60 and100 microns) is about 0.2, with little or no dependence on thetemperature of the illuminating star for stellar temperatures betweenabout 5000 and 33,000 K. This is interpreted as requiring that visualphotons as well as ultraviolet photons are capable of exciting12-microns emission from very small particles.
| High spectral resolution observations of fluorescent molecular hydrogen in molecular clouds
The 1-0 S(1) line of molecular hydrogen has been observed at highspectral resolution in several sources where the emission was suspectedof being fluorescent. In NGC 2023, the Orion Bar, and Parsamyan 18, theS(1) line is unresolved, and the line center close to the rest velocityof the ambient molecular cloud. Such behavior is expected for UV-excitedline emission. The H2 line widths in molecular clouds thus can serve asdiagnostic for shocked and UV-excitation mechanisms. If the lines arebroader than several km/s or velocity shifts are observed across asource it is likely that shocks are responsible for the excitation ofthe gas.
| Interstellar Molecular Hydrogen
Not Available
| Ultraviolet fluorescent molecular hydrogen emission
Computations are presented of the ultraviolet (UV) molecular hydrogenfluorescent emission-line spectra that are produced in cold, isothermal,low-density, static photodissociation regions. An approximte scalingequation is provided which relates the UV line intensities to the gasdensity, the intensity of the incident UV continuum radiation, themolecular formation rate coefficient, and the effective grain UVcontinuum absorption cross section. The UV emission-line intensities fora wide range of cloud conditions may be estimated using the scalingequation, an UV continuum-to-line conversion efficiency function, and asingle computed reference spectrum. The relationship between ultravioletand infrared fluorescent emissivities is discussed. The observations ofUV fluorescent emission from the reflection nebula IC 63 are analyzed,and the intensity of detectable infrared fluorescent emission from thisobject is predicted. The intensities of UV fluorescent emission from thereflection nebulae Parsamyan 18 and NGC 2023 are also predicted.
| Multifrequency observations of the cometary nebula P18 (NGC 2316).
Abstract image available at:http://adsabs.harvard.edu/abs/1988RMxAA..16...99L
| A search for molecular outflows toward the pre-main-sequence objects
A search for molecular outflows has been conducted toward a sample of 71young stellar objects dominated by optically selected pre-main-sequencestars. Molecular outflows ranging in size from 0.07 to about 5 pc, withexpansion velocities from 6 to 60 km/s, have been detected toward 20 ofthese objects and in an additional six infrared objects not included inthe original survey. The apparent ages of the outflows are from 1000 to500,000 yr; about half of the observed outflows are bipolar, with therest showing a wide variety of morphologies. It is found that outflowsdriven by low-luminosity objects tend to be more bipolar than thosedriven by high-luminosity objects. The implications of the results ofthe study are discussed.
| Molecular outflows and mass loss in the pre-main-sequence stars
Molecular outflows are used here to probe mass loss in premain sequence(PMS) stars. Mass-loss rates are determined for 26 objects ranging inluminosity from four to about 100,000 solar, in mass from 0.5 to 30solar, and in age from about 10,000 to about a million years. Thederived mass-loss rates range from 9 x 10 to the -9th to 9 x 10 to the-4th solar mass/yr, with a typical value of 3 x 10 to the -7th solarmass/yr. PMS objects showing mass loss fall in a clearly demarcatedregion of the H-R diagram. The mass loss is proportional to bolometricluminosity to the 0.6 power and to stellar mass to the 1.8 power. Theimplications of these findings for the nature of the PMS mass-lossmechanism, for self-regulated low-mass star formation, and for planetaryformation are discussed.
| Catalog of emission line stars of the orion population : 3 : 1988
Not Available
| Ultraviolet-pumped infrared fluorescent molecular hydrogen emission in reflection nebulae
Strong molecular hydrogen emission at 2.41 microns has been observed inthree out of six reflection nebulae surveyed. A spectrum of one nebula,Parsamyan 18, shows several H2 lines whose intensity ratios have valuesagreeing with those predicted if the excitation is due to UV-pumpedfluoresence and disagreeing with those predicted for shock and X-rayexcitations.
| The large system of molecular clouds in Orion and Monoceros
Emission is noted over about one-eighth of an 850-sq deg region centeredon Orion and Monoceros that has been surveyed in the J = 1 to 0 line ofCO; most of the emission arises from giant molecular clouds associatedwith Orion A and B, and Mon R2. A much smaller area was surveyed forC-13O emission. A comparison of cloud masses obtained by threeindependent methods indicates that CO luminosity is as accurate ameasure of cloud mass as other indicators. The possible relationshipsamong clouds in the survey are discussed, including the conjecture thatthe overall Orion complex of clouds is a much larger system thanpreviously considered, incorporating most of the clouds in the presentsurvey.
| The infrared emission bands. I - Correlation studies and the dependence on C/O ratio
Airborne measurements obtained for the unidentified IR (UIR) 5-8 micronemission bands of eight planetaries, eight locations in five reflectionnebulae, and seven locations in four H II regions (including the OrionBar), are presently compared with existing and new ground-basedobservations of the 3.3, 8.7, and 11.3 micron bands. The goodcorrelations found between the strengths of all pairs of bands lead tothe conclusion that all seven UIR features form a 'generic spectrum',although there are significant variations in the relative strengths ofthe features among the sources. The fraction of total far-IR luminosityradiated by a planetary in the strongest UIR feature at 7.7 microns isstrongly correlated with the nebular C/O ratio, strongly suggesting thathydrocarbons are the carriers of these features.
| Far-infrared photometry of low-mass pre-main-sequence stars with broad CO wings
A sample of 14 low-mass premain-sequence stars were studied in thefar-infrared. There is evidence for outflowing material around twelve ofthese stars; in most cases the evidence includes broad wings on theprofiles of the CO J = 2 to 1 line. Ten of the objects were detected (5sigma) at 100 micros, and seven were mapped at 50 and 100 micros. Thefar-infrared emission makes a significant contribution to the totalluminosity of the objects. It is found that the force available fromradiation pressure is not sufficient to drive the outflows. Any processwhich taps the same energy source as does the present stellar luminositymust have high efficiency.
| Reflection Nebulae: Celestial Veils
Not Available
| The high-velocity molecular flows near young stellar objects
Lada and Harvey (1981) have found that energetic, large-scale flows ofmolecular gas near young stellar objects represent a hithertounrecognized, but extremely important, phase of early stellar evolutioncommon to stars of a wide range of spectral type. The presentinvestigation is concerned with results of the first systematic searchfor high-velocity CO emission from the vicinity of young stellarobjects. Attention is given to both newly obtained data and recentlypublished results, and a detailed examination is conducted of thestatistical properties of this new class of energetic astrophysicalactivity. Seventeen sources are identified with (C-12)O emission linewidths in excess of 30 km/s. Nineteen sources with line widths between10 and 30 km/s are also identified. All the sources appear to belocalized sites of energetic activity within larger molecular complexes.
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