Region Of M82 Research Articles

Far-infrared observations of H II regions in M33

Three H II regions in M33, namely, IC 133, NGC 595, and NGC 604, have been observed at far-infrared wavelengths. Only NGC 604, the strongest radio source of the three, was detected. The far-infrared radiation appears to be thermal emission from dust. The amount of dust known to be present in NGC 604 from comparison of optical and radio data is sufficient to account for the observed far-infrared emission. The total power radiated in the far-infrared is comparable to the total luminosity of the exciting stars of the H II region.

ISAs and the dwarf content of the inner nuclear regions of M31

We have augmented and reanalyzed the Spinrad-Taylor scanner data for M31 in order to see whether any stellar mix can reproduce both these data and observed CO and Wing-Ford band indices. We have also tried to clarify the status of the anomalous strengths (''ISAa'') of certain spectral features which Spinrad and Taylor found; a reanalysis published by Faber had left their status uncertain. Our reanalysis yields the following conclusions:1. The Spinrad-Taylor data display large strength excesses in the b triplet and D lines, smaller strength excesses in a red CN band and some TiO bands, and marginal or definite strength deficiencies in the G band, the blue CN band, Ca I lambda4227, and Fe I lambda4384. Low microturbulence (compared to solar-neighborhood stars) may account for the strength deficiencies. Both excesses and deficiencies can inflate a model's summed squared residuals, and large excesses can bias the operation of model-building algorithms.2. There is no clearly satisfactory way to account simultaneously for the CO and Wing-Ford bands and Spinrad and Taylor's lambda8190 index. Moreover, no model quite reproduces Spinrad and Taylor's 1 ..mu..m colors. This problem also appears: but not decisively: in data published by O'Connell.3. Spinrad and Taylor's conclusions were influenced bymore » certain key assumptions which have since been improved, or which can now be shown to be incorrect.4. The combined data of Wood and McClure and van den Bergh do not require strong CN stars to reproduce them, and thus are not necessarily in conflict with Spinrad and Taylor's data.« less

Rotation of the nuclear region of M31

Rotation of the nuclear region of M31

A Warp in the HI Distribution at the Extreme NE and SW of M31

Aperture synthesis observations of the neutral hydrogen in the extreme NE and SW regions of M31 have been made using the Cambridge Half-Mile Telescope, with an angular resolution of 3′.6 × 5′.5 and a resolution in radial velocity of 16 km/s (Newton and Emerson, 1977). These observations show that a warp in the HI distribution exists in opposite directions at each end of the galaxy.

Observations of forbidden S III in NGC 604 and N/S abundance gradients

view Abstract Citations (32) References (29) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Observations of [S III] in NGC 604 and N/S abundance gradients. Hawley, S. A. ; Grandi, S. A. Abstract Line intensities have been obtained for NGC 604 - a giant H II region in M33 - in the wavelength range from 6312 to 10,049 A. Observations of the forbidden S III lines at 9069 and 9532 A yield an S(2+) abundance and an accurate total S abundance in agreement with that for the Orion Nebula. Previous investigators have seriously overestimated N/S. The use of the ratio between forbidden N II and forbidden S II emission lines as an abundance indicator is discussed, and it is concluded that, while a gradient in that ratio implies a gradient in N/S, a dependable calibration of line ratio versus abundance is unavailable. Publication: The Astrophysical Journal Pub Date: October 1977 DOI: 10.1086/155590 Bibcode: 1977ApJ...217..420H Keywords: Abundance; Nebulae; Sulfur; Astronomical Models; Astronomical Spectroscopy; H Ii Regions; Infrared Astronomy; Nitrogen; Oxygen; Astrophysics full text sources ADS | data products NED (2)

Far-infrared spectrometry of H II regions and the Galactic Center

view Abstract Citations (18) References (7) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Far-infrared spectrometry of H II regions and the galactic center. Ward, D. B. ; Gull, G. E. ; Harwit, M. Abstract The H II regions W3, M17, and W51, as well as the Galactic center regions Sgr A and Sgr B2, were observed at a spectral resolving power of roughly 15 in the range from 45 to 115 microns. At that resolution the spectra appear featureless and can be approximated by dilute blackbody curves whose temperatures range from approximately 90 K down to about 40 K. Publication: The Astrophysical Journal Pub Date: June 1977 DOI: 10.1086/182444 Bibcode: 1977ApJ...214L..63W Keywords: Far Infrared Radiation; Galactic Nuclei; H Ii Regions; Infrared Spectroscopy; Spectrum Analysis; Black Body Radiation; Brightness Temperature; Calibrating; Hydrogen Ions; Infrared Spectra; Astronomy full text sources ADS |

Color gradients in the nuclear region of M31

Spectrophotometric measurements of the nuclear region of M31 under conditions of excellent seeing with M31 near the zenith and using a 3.8-9.9-in. diameter entrance annulus for the bulge along with a 3.6-in. aperture for the nucleus, show that the nuclear region is only slightly redder and shows marginally stronger CN blends than the bulge. The data can be interpreted in terms of an increase in heavy-element abundance toward the center of M31 by a factor substantially less than two.

Far-infrared spectral observations of M42 and M17

Results are reported for coarse-resolution far-IR spectral observations of the H II regions M17 and M41 in the wavelength range from 42 to 115 microns. The observations were made at an altitude of 13.7 km with the 30-cm telescope of the NASA Lear jet. The spectrum of M42 is shown to be quite smooth and to fit a diluted 100-K blackbody very well. It is found that the emission from M17 falls steeply from 40 to 63 microns, then rises again to 80 microns before falling off once more toward longer wavelengths. The best fit of this spectrum for an inverse-square-wavelength emissivity law is found to require a two-temperature model with temperatures below 30 K for the cold dust component. It is concluded that the spectrum of M17 seems to require the presence of a material with a better far-IR emissivity than those for which detailed laboratory measurements have been made.

Spectrophotometric observations of ionized hydrogen regions in nearby spiral and irregular galaxies

A program of direct photography and spectrophotometry has been carried out on H ii regions in a selection of nearby spiral and irregular galaxies. Abundance analyses for H ii regions in M101 and M33 show a strong radial gradient in the O/H ratio, decreasing by approximately a factor of 10 across the galaxy disks. The Ne/O and S/O abundances ratios are constant. The derived nitrogen abundances, coupled with the line ratios for other H ii regions, indicate a weak gradient in the ratio of N/O, decreasing by about a factor of 4 from the nuclear regions outward. No large helium abundance differences are observed, although the most oxgyen-poor regions may show marginally significant helium deficiencies. Excitation differences among the H ii regions of Sbc-Scd-Irr galaxies can best be understood in terms of an abundance sequence which progresses from higher to lower heavy-element enrichment as one progresses from the earlier to later type galaxies.

Radio structure of the M87 jet

THE central region of M87 has a complex radio structure. There are at least three components1,2, with diameters ≈0″.0013, ≈0″.01 and ≈0″.3, coincident with the optical nucleus of the galaxy and on either side there are two elongated components, ≈25″ in extent, the radio counterparts of the jet and counterjet3,4. When observed with a resolution of ≈5″, the structure of these outer components is similar and depends little on observing frequency, but at higher resolutions the jet component is seen to possess fine structure which the other lacks5,6. Here I report results of interferometer observations at 408 and 1,666 MHz, with resolving powers ≈0.5″ along the jet, which reveal the position and extent of this fine structure in more detail.

Radio Observations of Hii Regions in M33

The Westerbork Synthesis Radio Telescope was used to map the continuum radiation of M33 at 1415 MHz. Of 67 radio sources with fluxes S> 1.8 mJy (3σ), 60% coincide with Hα sources. These are all intrinsically stronger than 4 × the Orion nebula, i.e., they are giant Hiiregions. The two strongest sources, NGC 604 (58 mJy) and NGC 595 (20 mJy), are similar to W51.

Diameters of H II Regions in M31 and Comparison with the Largest Regions in M33

In order to obtain diameters of H ii regions which are comparable to those that are measured in more distant Sb spirals, small-scale plates in Ha wavelengths have been obtained for M31. It is found that H ii regions with low and medium surface brightness mostly range from less than 7 to about 40 arc sec in diameter at the distance of M31. High-surface-brightness H ii regions show a wider distribution of sizes, ranging from less than 7 to about 70 arc sec in apparent diameter. Two features in M3 1 appear to be an agglomeration of smaller H ij regions into single large emission regions of 150 and 180 arc sec, respectively. Observations carried out with exactly the same plate-filter and exposure combinations on M33 show differences in the stiucture of the average H ii region in M31 and M33. The M33 emission regions tend to be single large loops and rings. The M31 emission regions tend to be more stellar and occur in associated groups. If the larger H ii complexes in M31 are classed as single regions, then there is a contradiction to the generally quoted result that H ii regions are larger in Sc than in Sb galaxies. Because of the gradual way in which the intrinsic diameter-number plot falls off toward large diameters, the apparent size of H ii regions is not a very precise indicator of extragalactic distances. The results reported here on M31 and M33 support, however, the idea that the intrinsic sizes of H ii regions are reliable as gross indicators of distance, accurate within approximately a factor of 2. Subject headings: galaxies nebulae

Gas in the Nucleus and Disk of M31

Image tube spectra of emission regions in M31 have been studied to determine relative line strengths and abundances. Lines of H, He, [NII], [SII], [Oi], [Oii], [Oiii] are observed. The analysis indicates: (1) that there are ions whose line strengths, relative to Hα, are a function of the position of the emission region in M31; (2) abundance differences or different excitation mechanisms exist in regions separated by only a few hundred parsecs.

Color Changes and Absorption-Line Variations Over the Inner Disk of M31 and the Central Regions of M32 and NGC 4472

Color changes and absorption line variations in M31, M32 and NGC 4472, attempting synthesis of M31 disk population

Das geschwindigkeitsellipsoid derHII-regionen in M33

The peculiar radial velocities ofHii regions in M33 varies with position angle in a manner that can be explained by an ellipsoidal distribution with minor axis in the direction of rotation. The amplitude of the variations, however, is too great as compared with theory or experience in the galaxy.

The Proper Motions of Stars in the Region of M31

The Proper Motions of Stars in the Region of M31