Micron Continuum Research Articles

Infrared and optical imagery of the Crab Nebula

The paper presents 1.644 micron forbidden-line Fe II and 1.570 micron continuum images of the Crab Nebula which are compared with optical H-alpha, forbidden-line O III, and 5100 A continuum data. While the same prominent filaments are generally apparent in all lines, no substantial variations within the nebula in the strength and morphology of forbidden-line Fe II relative to the other lines are found. The infrared to optical continuum ratio of the synchrotron nebula shows 15 - 20 percent variations which are dominated by features which appear related to the position of the pulsar. These are interpreted as variations of 0.15 in the spectral index and it is suggested that they are related to the radiative decay of energetic particles and the paths over which these particles travel from the pulsar throughout the nebula.

Velocity-resolved images of molecular hydrogen in the colliding galaxy NGC 6240 - Evidence of a global shock

view Abstract Citations (40) References (21) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Velocity-Resolved Images of Molecular Hydrogen in the Colliding Galaxy NGC 6240: Evidence of a Global Shock Herbst, T. M. ; Graham, J. R. ; Beckwith, S. ; Tsutsui, K. ; Soifer, B. T. ; Matthews, K. Abstract Images of the nuclear region of NGC 6240 taken in the 2.122 micron, ν= 1-0 S(1) quadrupole line of molecular hydrogen demonstrate that the line emission is extended and distinct from the two nuclei producing most of the continuum emission. A region ~ 2" southwest of the southern nucleus produces almost 20% of the total line radiation, yet has no detectable 2 micron continuum. The H_2_ lines are asymmetric, with very little emission on the short-wavelength side of the line peaks. These results indicate that a global phenomenon, such as the dissipative collision of two disks of molecular material, is taking place. The presence of shock-excited material at the same velocity throughout the central kpc of the galaxy and the asymmetry in the S(1) line profile support this conclusion. Global shocks may power the far-infrared luminosity of NGC 6240 as well; if so, the strong H_2_ and infrared emission can persist for no more than ~ 10^6^ yr. Publication: The Astronomical Journal Pub Date: June 1990 DOI: 10.1086/115455 Bibcode: 1990AJ.....99.1773H Keywords: Galactic Nuclei; Hydrogen; Interacting Galaxies; Interstellar Gas; Emission Spectra; Far Infrared Radiation; Resonance Fluorescence; Shock Waves; Starburst Galaxies; Astrophysics; GALAXIES: INTERACTIONS; GALAXIES: INDIVIDUAL full text sources ADS | data products SIMBAD (5) NED (1)

Dense molecular gas, star formation, and the CO to H2 conversion factor in nearby galaxies

view Abstract Citations (51) References (21) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Dense molecular gas, star formation and the CO to H2 conversion factor in nearby galaxies. Sage, Leslie J. ; Shore, Steven N. ; Solomon, P. M. Abstract A search for CS J = 2 → 1 emission from 14 nearby galaxies yielded six detections and five marginal detections. The detection of CS emission confirms the presence of large quantities of dense gas near the centers of nearby galaxies. The CS and CO 1 → 0 fluxes from the centers of galaxies are linearly correlated. The ratio of CS to CO flux is independent of galaxian parameters and can be understood as a consequence of a beam average of two populations of molecular clouds, one similar to Galactic disk clouds, the other similar to Galactic center clouds. Both CS and CO emission are correlated with central C II (λ158 μm) line emission and 100 microns continuum emission, indicating that both molecules trace active star formation. We conclude that the mass of dense gas traced by CS is approximately proportional to the total molecular mass and that a standard CO-H2conversion factor produces a reasonable estimate of the H2mass in most galaxies. Publication: The Astrophysical Journal Pub Date: March 1990 DOI: 10.1086/168478 Bibcode: 1990ApJ...351..422S Keywords: Galactic Mass; Interstellar Gas; Molecular Clouds; Star Formation; Carbon Monoxide; Hydrogen; galaxies: interstellar matter; molecule processes; stars: formation; Astrophysics full text sources ADS | data products SIMBAD (14) NED (14)

CO isotope studies and mass of the Sagittarius B2 molecular cloud

view Abstract Citations (99) References (23) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS CO Isotope Studies of the Sagittarius B2 Molecular Cloud Lis, Dariusz C. ; Goldsmith, Paul F. Abstract (C-13)O and (C-18)O observations of the central region of Sagittarius B2 are presented. A (C-13)O to (C-18)O abundance ratio of 9.0 + or - 1.9, consistent with the average ratio in the disk and other Galactic center sources, is obtained. Comparison of the (C-13)O column density based on the present data with H2 column density based on 1300 micron continuum data gives an upper limit of 10 to the -6th for the (C-13)O fractional abundance, a factor of two lower than the local value. The (C-12)O/H2 abundance ratio is a factor of six lower than the local value due to the lower (C-12)O to (C-13)O ratio. It is concluded that abundances of many molecular species in addition to the CO isotopes may be lower than in local clouds. The observations suggest a two-component structure for the cloud, with a constant density component and a component with density having a power-law dependence on the distance from cloud center. Values for the outer radius, total mass, and virial mass of the cloud are derived. Publication: The Astrophysical Journal Pub Date: February 1989 DOI: 10.1086/167141 Bibcode: 1989ApJ...337..704L Keywords: Astronomical Spectroscopy; Carbon Monoxide; H Ii Regions; Molecular Clouds; Abundance; Density Distribution; Mass Distribution; Sagittarius Constellation; Signal To Noise Ratios; Spectral Line Width; Astrophysics; INTERSTELLAR: ABUNDANCES; INTERSTELLAR: MOLECULES; NEBULAE: INDIVIDUAL NAME: SAGITTARIUS B2 full text sources ADS | data products SIMBAD (1)

1300 micron continuum and C18O line mapping of the giant molecular cloud cores in Orion, W49, and W51.

We present observations of the 1300 micron continuum emission and the C18O spectral-line emission from three well-studied giant molecular cloud cores: Orion, W49, and W51. The observations were obtained at the Five College Radio Astronomy Observatory, and they provide a means to examine the consistency of these two methods to trace the column density structure of molecular clouds. We find a good general correlation between the 1300 micron continuum, which traces the column density of dust, and the C18O J = 2 --> 1 line emission, which traces the column density of molecular gas, when the effects of source temperature are taken into consideration. Moreover, nominal values for the gas and dust abundances and the dust properties reproduce the observed continuum-to-line ratios. Thus, no strong C18O abundance gradients within sources has been found, and it appears that either the C18O emission lines or the submillimeter dust emission may be used to derive the mass column density within molecular clouds accurately.

Molecules in galaxies. IV - Molecular and atomic hydrogen in Virgo cluster galaxies

If gas and dust are well mixed in a galaxy, the dust mass should be proportional to the sum of the masses of atomic and molecular gas. This assumption has been used to estimate the mean conversion ratio between the flux in the CO J = 1-0 line and the molecular gas mass of a galaxy using a set of observations of the 100 microns continuum flux density, the H I 21 cm line flux and the CO line flux for a sample of spiral galaxies in the Virgo cluster; these galaxies have a wide variation in the ratio of CO to H I line flux. The result, N(H2) = 6.3 + or - 3.5 x 10 to the 20th mol/sq cm/(K x km/s), is in agreement with values inferred from observations of the molecular interstellar medium in the Galaxy.

IRAS large-beam and ground-based small-beam measurements of the unidentified 11.3 and forbidden NE II 12.8 micron line fluxes in the starburst galaxy M82

view Abstract Citations (8) References (15) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS IRAS Large-Beam and Ground-Based Small-Beam Measurements of the Unidentified 11.3 and [Ne ii] 12.8 Micron Line Fluxes in the Starburst Galaxy M82 Levan, P. D. ; Price, S. D. Abstract The low resolution spectrometer data obtained by IRAS on M82, when compared with smaller ground-based beam 8-14 micron spectra, provide interesting beam-dependent ratios of the fluxes for the 'unidentified' 11.3 micron emission feature, the forbidden Ne II 12.8 micron fine structure line, and the 10 micron continuum. Specifically, the relative strengths of the 11.3 micron feature and the 10 continuum are constant for the small and large beam diameters, concordant with published interpretations of both as being associated with dusty regions of thermal radiation. By contrast, the relative strength of either the 11.3 micron feature or 10 micron continuum fluxes to the forbidden Ne II 12.8 micron line flux increases modestly from the smaller to the larger IRAS beam diameter. This is taken as evidence for significant amounts of warm dust above that associated with the H II regions in the nucleus of M82. Publication: The Astrophysical Journal Pub Date: January 1987 DOI: 10.1086/164904 Bibcode: 1987ApJ...312..592L Keywords: Astronomical Spectroscopy; Galactic Structure; Infrared Spectra; Line Spectra; Radiant Flux Density; Star Formation; Starburst Galaxies; Cosmic Dust; Galactic Nuclei; H Ii Regions; Infrared Astronomy Satellite; Neon; Astrophysics; GALAXIES: INDIVIDUAL MESSIER NUMBER: M82; GALAXIES: NUCLEI; INFRARED: SOURCES; INFRARED: SPECTRA; STARS: FORMATION full text sources ADS | data products SIMBAD (1) NED (1)

Observations of 3.2-3.6 micron emission features in comet Halley

view Abstract Citations (66) References (18) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Observations of 3.2--3.6 Micron Emission Features in Comet Halley Knacke, R. F. ; Brooke, T. Y. ; Joyce, R. R. Abstract Ground-based spectroscopic observations of the emission feature near 3.3 microns discovered in comet Halley by the Vega 1 spacecraft are reported. At a resolution of Delta gamma/gamma = 0.012 the emission consists of several components between 3.2 and 3.6 microns, and appears to be a superposition of C-H group bands. The feature is observed out to several thousand kilometers from the nucleus and does not appear to be thermal radiation from the grains responsible for the 4-20 micron continuum. Molecular scattering or emission by a component of cool (less than 400 K) grains would require near cosmic abundance of carbon. Hotter grains would radiate strongly enough to reduce the abundance requirement. The band shape is similar, but not identical, to interstellar absorption at 3.4 microns, to spectra of organic extracts from carbonaceous chondrites, and to spectra of some synthesized materials, such as 'QCCs' (as discussed by Sakata and colleagues in 1984). A newly found emission at 3.52 + or 0.02 microns is evidence for oxygen containing organic molecules, possibly formaldehyde or methanol. Publication: The Astrophysical Journal Pub Date: November 1986 DOI: 10.1086/184780 Bibcode: 1986ApJ...310L..49K Keywords: Halley'S Comet; Infrared Spectra; Interstellar Matter; Abundance; Cosmic Dust; Formaldehyde; Methyl Alcohol; Astrophysics; COMETS; INFRARED: SPECTRA; INTERSTELLAR: MATTER full text sources ADS |

Infrared spectroscopy of star formation in interacting galaxies

Brackett-alpha and Brackett-gamma lines are used to study star formation in the external, interacting galaxies NGC 5195, IC 4553, and the NGC 3690 + IC 694 system. The 10 micron continuum flux in IC 694 appears to be higher than that expected from Galactic type H II regions. Upper limits to the Brackett line emission in NGC 5195 and IC 4553 indicate that in these sources, the infrared continua are poorly correlated with the amount of observed ionized gas. In NGC 5195, the 10 micron excess is probably due to abnormally hot dust. In IC 4553, the intense far-infrared continuum suggests that either there is unusually high obscuration of the star forming regions, or that the young OB stars may produce only a small portion of the infrared luminosity. 27 references.

Rapid variation in the circumstellar 10 micron emission of Alpha Orionis

The spatial distribution of 10 micron continuum flux around the supergiant star Alpha Orionis was measured on two occasions separated by an interval of 1 yr. A significant change in the infrared radiation pattern on the subarcsecond scale was observed. This change cannot be explained plausibly by macroscopic motion but may be due to a change in the physical properties of the circumstellar dust.

Observations of the brightness profile of the sun in the 30-200 micron continuum

The brightness profile of the quiet sun in broad continuum passbands centered at 30, 50, 100, and 200 microns was observed with a resolution of 2 arcmin. Weak radial darkening was seen at all four wavelengths near disk center. This reverses to brightening toward the limb in the 100 and 200 micron continuum. Radial darkening at 100 and 200 microns is not expected from smooth model chromospheres consistent with absolute brightness measurements. These results do not support a homogeneous model of the low chromosphere, where the temperature reversal occurs.

Submillimeter observations of W3

A 35 arcsec resolution, 400 micron continuum map of the core of the W3 molecular cloud complex is presented. The map shows prominent peaks centered approximately at the positions of the infrared sources IRS 4 and IRS 5 with stronger-emission at the western (IRS 4) peak. The visual extinction (inferred from the submillimeter measurements) through the center of both peaks is large (A sub v = 200). A total mass for the core of 900 solar masses is estimated, consistent with dynamical estimates if the observed velocity gradient is a result of rotation. The peak H2 density is approximately 2.8 x 10 to the 5th/cu cm. The observations exclude the possibility that the shell H II regions, W3A-C, could be in pressure equilibrium with the surrounding cloud. The observations establish that the core of W3 contains several massive condensations surrounding the youngest stars in the region.

Infrared spectra of WN stars. I - HD 50896

view Abstract Citations (58) References (46) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Infrared spectra of WN stars. I. HD 50896. Hillier, D. J. ; Jones, T. J. ; Hyland, A. R. Abstract In connection with the present investigation, IR spectra in the range from 1 to 4.2 microns with a resolution of approximately 700 are presented for the WN5 star HD 50896. The continuum flux is examined, and it is shown that the wind of HD 50896 is optically thick and has a constant or near-constant velocity zone as first indicated by Hartmann and Cassinelli (1977). It is also shown that with a very extended atmosphere the continuum forms over a very large volume. The emission-line strengths are strongly influenced by the local continuum optical depth. A temperature of 33,000 K is derived for the region in which the 2 micron continuum is formed. It appears, therefore, that the UV continuum must form in regions with temperatures which exceed 60,000 K. Publication: The Astrophysical Journal Pub Date: August 1983 DOI: 10.1086/161189 Bibcode: 1983ApJ...271..221H Keywords: Infrared Spectra; Stellar Spectra; Stellar Winds; Wolf-Rayet Stars; Continuous Spectra; Emission Spectra; Line Spectra; Spectral Line Width; Spectral Resolution; Stellar Spectrophotometry; Stellar Temperature; Ultraviolet Spectra; Visible Spectrum; Astrophysics full text sources ADS | data products SIMBAD (2) Related Materials (1) Part 2: 1985AJ.....90.1514H

Near-infrared spectrophotometry of NGC 4151

view Abstract Citations (13) References (30) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Near-infrared spectrophotometry of NGC 4151 McAlary, C. W. ; McLaren, R. A. Abstract Two to four micron spectrophotometry of the Seyfert 1.5 galaxy NGC 4151 has been obtained. The B-alpha and B-gamma lines of hydrogen have been detected with strengths of 4.2 + or - 0.7 and 1.9 + or - 0.2 x 10 to the -13th ergs/sq cm per sec, respectively. The B-alpha/H-gamma ratio has been used to derive an upper limit, E(B-V) not greater than 0.13 mag, for the reddening toward the line formation regions of the nucleus. The 2-4 micron continuum of NGC 4151 can be adequately fitted by two black bodies, one representing a stellar component and the other strong thermal dust emission. No more than 10% of the total emission at 2 microns can be attributed to any nonthermal spectral distribution. Publication: The Astrophysical Journal Pub Date: November 1981 DOI: 10.1086/159351 Bibcode: 1981ApJ...250...98M Keywords: Emission Spectra; Galactic Nuclei; Infrared Spectra; Near Infrared Radiation; Seyfert Galaxies; Spectrophotometry; Cosmic Dust; Hydrogen; Interstellar Extinction; Line Spectra; Red Shift; Spectrum Analysis; Stellar Spectra; Astrophysics full text sources ADS | data products NED (8)

Solar limb brightening at 350 microns

view Abstract Citations (18) References (13) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Solar limb brightening at 350 microns Lindsey, C. ; Hildebrand, R. H. ; Keene, J. ; Whitcomb, S. E. Abstract The NASA Infrared Telescope Facility at Mauna Kea was used to observe the intensity profile of the quiet solar limb in the 300-400 micron continuum. A significant resolved brightening of several percent over the outer 60 arcsec of the solar limb in this band is found. However, the magnitude of the brightening is considerably less than that indicated by earlier observations of a total solar eclipse in integrated sun-moon radiation by Beckman, Lesurf, and Ross (1975) in the 1.2 mm continuum. More recent ground-based observations indicate that the magnitude of solar limb brightening at 800 microns and at 1.3 mm is stronger than that at 350 microns. This may be regarded as an indication that the hot material which produces the brightening at the extreme limb, thought to consist in part of chromospheric spicules, is optically thin in the 350 micron continuum. Publication: The Astrophysical Journal Pub Date: September 1981 DOI: 10.1086/159207 Bibcode: 1981ApJ...248..830L Keywords: Infrared Astronomy; Limb Brightening; Solar Flux Density; Solar Limb; Submillimeter Waves; Chromosphere; Infrared Telescopes; Solar Physics full text sources ADS |

2 micron spectroscopy of the nucleus of NGC 1068

Both stellar and interstellar features are found in a 2.0-2.4 micron spectrum centered on the nucleus of NGC 1068. The strengths of first-overtone CO absorption bands suggest that late-type giant stars contribute about 25% of the 2.3 micron continuum within 200 pc of the galactic center. Subtraction of this starlight from the spectrum leaves a gray body continuum component characterized by temperatures of about 800 K. The K-band flux distribution of this nonstellar emission suggests an identification with the compact source dominant at wavelengths greater than about 3.0 microns and is consistent with extrapolation of the nu to the -1.85 power law ultraviolet source. Comparisons of IR and B gamma luminosities, total H2 line luminosity, and cloud mass in the NGC 1068 nucleus and the Orion Molecular Cloud support the hypothesis that, as in Orion, the NGC 1068 IR luminosity is determined by star formation activity but at much higher conversion efficiencies.

Infrared spectrophotometry of SS 433

view Abstract Citations (18) References (30) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Infrared spectrophotometry of SS433. McAlary, C. W. ; McLaren, R. A. Abstract IR spectrophotometry of the peculiar object SS 433 from 2.0 to 2.4 microns has revealed the presence of strong emission lines of the Brackett and Paschen series of hydrogen. B-gamma at its rest wavelength was detected along with redshifted components of B-gamma, B-delta, and P-alpha, whose velocities correspond closely to those predicted for the Balmer emission lines at the epoch of observation. The strengths of the B-gamma and H-alpha lines are used to estimate a value of A(V) = 7.0-7.5 mag for the reddening towards SS 433. When corrected for reddening and free-free emission, the observed 0.55-3.5 micron continuum of SS 433 can be fitted to a single 15,700 K blackbody. Publication: The Astrophysical Journal Pub Date: September 1980 DOI: 10.1086/158298 Bibcode: 1980ApJ...240..853M Keywords: Emission Spectra; H Lines; Infrared Spectra; Stellar Spectrophotometry; Line Spectra; Paschen Series; Astrophysics; Emission Lines:SS433; Extinction:SS433; Infrared Photometry:SS433; Infrared Spectra:SS433 full text sources ADS | data products SIMBAD (4)

Two-micron spectrophotometry of the galaxy NGC 253

A very strong Brackett-gamma hydrogen emission line, and the 2.3 micron CO stellar absorption feature were measured in NGC 253. The presence and strength of the CO feature indicates that late type giant stars produce most of the 2.2 micron continuum emission, while the rate of ionization implied by strength of the Brackett-gamma line indicates that much, perhaps all, of the luminosity detected at far infrared wavelengths originates from a large number of OB stars. As compared to the corresponding region of the Galaxy, the number of massive young stars in the central 200 pc of NGC 253 is thirty times greater, but the total mass of stars is roughly the same.

3 millimeter and 350 micron continuum observations of the DR-21 and SGR B2 regions

view Abstract Citations (32) References (21) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS 3 millimeter and 350 micron continuum observations of the DR-21 and Sgr B2 regions. Righini, G. ; Simon, M. ; Joyce, R. R. Abstract We have detected and mapped the 3.2 and 3.5 mm continuum radiation of DR-2l (OH). The spatial distribution and spectral dependence of the 3 mm emission imply that it is thermal radiation of the dust grains within the molecular and submillimeter source. Between 3 mm and 350 IL the frequency dependence of the dust grain opacity is T(v) v , with > 1.2 + 0.1 in DR-2l (OH) and P > 1.5 + 0.3 in DR-2l. We have also remapped Sgr B2 at 3.2 mm and 350 IL to study the relationship of the submillimeter source to the source of 3 mm excess radiation discovered by Hobbs, Modali, and Maran. These observations show that the location of the core that is responsible for the 3 mm excess is indistinguishable from the location of the submillimeter source, and that emission of the submillimeter source extrapolated to 3 mm could reasonably account for the observed excess. Subject headings: interstellar: molecules - nebulae: general - radio sources: general Publication: The Astrophysical Journal Pub Date: July 1976 DOI: 10.1086/154475 Bibcode: 1976ApJ...207..119R Keywords: Infrared Radiation; Interstellar Radiation; Millimeter Waves; Radio Sources (Astronomy); Submillimeter Waves; Astronomical Maps; Atmospheric Models; Cosmic Dust; Interstellar Matter; Nebulae; Thermal Radiation; Astrophysics full text sources ADS |

Identification of the 890 per CM carbonate signature in NGC 7027

High-resolution spectroscopic measurements of the 11 micron continuum emission from NGC 7027 indicate that MgCO3 is a constituent of the dust in the nebula. Other carbonate compounds may also be present in concentrations approximately 1 order of magnitude below that of MgCO3. Dust-grain temperatures combined with the abundance of MgCO3 require that most of the material composing the grains must be carbon or C, N, O compounds.