Faint Regions Research Articles

Kinematics of Herbig-Haro Objects and Jets in the Orion Nebula

We have surveyed the inner 5' of the Orion Nebula by means of Hα and [N II] Fabry-Perot imaging spectroscopy to present a kinematical study of the Herbig-Haro objects in the nebula. The objects studied in this work are HH 202, 203, 204, 529, 269, and other associated features. For HH 202 we find new features that, because of their high velocities (up to 100 km s-1), indicate the presence of an outflow that probably is an HH flow not cataloged previously. HH 202 could be only a part of this larger outflow. Large internal motions are found in the fainter regions of HH 203-204, as well as evidence of transverse density gradients that could account for the asymmetry in the brightness distribution of HH 204. We report for the first time a high blueshifted velocity (-118 km s-1) associated with HH 204 and show that the apex of HH 204 is indeed the zone of maximum velocity, in agreement with bow shock models. We also studied the radial velocity field of HH 269, finding features associated with the HH object. From our studies, we find kinematic evidence that suggests HH 203-204 and HH 202 are part of a big (~0.55 pc) bipolar HH outflow.

On‐the‐Disk Development of the Halo Coronal Mass Ejection on 1998 May 2

A halo coronal mass ejection (CME) was observed at 15:03 UT on 1998 May 2 by the Solar and Heliospheric Observatory Large-Angle Spectrometric Coronagraph. The observation of the CME was preceded by a major soft X-ray flare in NOAA Active Region 8210, characterized by a delta spot magnetic configuration and some activity in region 8214. A large transequatorial interconnecting loop (TIL) seen in the soft X-rays connected AR 8210 to a faint magnetic field region in the periphery of region 8214. Smaller loop systems were also connecting AR 8210 to other fainter bipolar magnetic structures, the interconnecting loop (IL) east of AR 8210 being one of the most visible. We present here a multiwavelength analysis of the large- and small-scale coronal structures associated with the development of the flare and of the CME, with emphasis placed on radio-imaging data. In the early phases of the flare, the radio emission sources traced the propagation paths of electrons along the TIL and the IL, which are accelerated in the vicinity of AR 8210. Furthermore, jetlike flows were observed in soft X-rays and in Hα in these directions. Significantly, the TIL and IL loop systems disappeared at least partially after the CME. An EUV Imaging Telescope (EIT) dimming region of similar size and shape to the soft X-ray TIL, but noticeably offset from it, was also observed. During the flash phase of the flare, new radio sources appeared, presenting signatures of destabilization and reconnection at discrete locations of the connecting loops. We interpret these as possible signatures of the CME liftoff on the disk. An Hα Moreton wave (blast wave) and an EIT wave were also observed, originating from the flaring AR 8210. The signatures in radio, after the wave propagated high into the corona, include type II-like emissions in the spectra. The radio images link these emissions to fast-moving sources, presumably formed at locations where the blast wave encounters magnetic structures. The opening of the CME magnetic field is revealed by the radio observations, which show large and expanding moving sources overlying the later-seen EIT dimming region.

Detection and Mapping of Decoupled Stellar and Ionized Gas Structures in the Ultraluminous Infrared Galaxy IRAS 12112+0305.

Integral field optical spectroscopy with the INTEGRAL fiber-fed system and Hubble Space Telescope optical imaging are used to map the complex stellar and warm ionized gas structure in the ultraluminous infrared galaxy IRAS 12112+0305. Images reconstructed from wavelength-delimited extractions of the integral field spectra reveal that the observed ionized gas distribution is decoupled from the stellar main body of the galaxy, with the dominant continuum and emission-line regions separated by projected distances of up to 7.5 kpc. The two optical nuclei are detected as apparently faint emission-line regions, and their optical properties are consistent with being dust-enshrouded weak [O i] LINERs. The brightest emission-line region is associated with a faint (mI=20.4), giant H ii region of 600 pc diameter, in which a young ( approximately 5 Myr) massive cluster of about 2x107 M middle dot in circle dominates the ionization. Internal reddening toward the line-emitting regions and the optical nuclei ranges from 1 to 8 mag in the visual. Taking the reddening into account, the overall star formation in IRAS 12112+0305 is dominated by starbursts associated with the two nuclei and corresponds to a star formation rate of 80 M middle dot in circle yr-1.

A Deep Long‐Slit Spectroscopic Study of the Two Bipolar Outflows from the T Tauri Binary System

We present results of a new deep, high-resolution, long-slit spectroscopic study of the extended nebular line emission around the young binary T Tauri. The deduced position-velocity diagrams of the [O I], [N II], and [S II] lines have been used to investigate in great detail the complex geometric and kinematic structure of the mass outflows from the stellar binary components T Tau N and T Tau S. A large number of distinct extended outflow components, each of them characterized by its specific spatio-kinematic properties, has been identified. In addition to the brighter components (A, B, C, D, E, and F) already described in detail by Bohm & Solf, we have detected several much fainter components (G, H, I, J, K, and L), some of them extending up to ~40'' from the central binary. The new data confirm the existence of two separate bipolar outflow systems associated with the binary: one of them oriented near the east-west direction and probably originating from the visible binary component T Tau N, the other one oriented near the north-south direction and probably originating from the infrared binary component T Tau S. In the east-west outflow, so far considered to be represented only by blueshifted components (B, F, and H) west of T Tau N, we have detected for the first time an indication for a redshifted faint counterjet (G) east of T Tau, corresponding to the known HH 155 jet (H). In the north-south outflow, so far considered to be represented only by two components (C and D) near the central source (≤3''), two additional, rather faint components (I and J) have been detected, which are located farther out (8''-15'') on opposite sides of the source. Both faint components present rather low velocities of opposite sign but rather large velocity dispersions of about 75-100 km s-1 (FWHM). Using a biconical model for the outflow geometry, we have derived an inclination angle of 79° with respect to the line of sight for the bipolar axis and deduced typical velocities of ~91 and ~280 km s-1 in the faint outer regions (I and J) and the bright inner regions (C and D) of the north-south outflow, respectively. We have compared the kinematic state (mean radial velocity and velocity dispersion) of the hot (partially) ionized gas of the outflows from the binary T Tau deduced from our forbidden line observations with that of the warm molecular gas determined from the v = 1-0 S(1) line of H2 observations by T. M. Herbst and coworkers. In principal, the [S II] and H2 emission regions refer to very different spatial regions of the outflows, and hence the kinematic states of the two regions do not have to be coupled to each other. In particular, it is expected that the velocity dispersion derived from the [S II] lines is much larger than that from the H2 lines. These expectations are generally fulfilled by the observations, except for the core region of Burnham's nebula (component E) where the velocity dispersions of both the forbidden and H2 lines are approximately the same. These findings as well as other enigmatic properties of Burnham's nebula reported earlier are not yet understood.

Evidence for polar cytoplasm/nuage in rat oocytes

In many organisms oocytes contain dark-staining material, termed nuage, that is concentrated at one pole of the oocyte cytoplasm and that influences the further development of the oocyte after fertilization. In mammalian oocytes, ultrastructural studies have detected small patches of nuage-like material, but thus far no nuage-rich zone of polar cytoplasm has been reported. Here, we report that when large sections of rat ovary embedded in methacrylate resin are stained with toluidine blue and surveyed, many oocytes contain a narrow, sharply defined, basophilic zone of polar cytoplasm that appears analogous to the polar cytoplasm of Xenopus and other non-mammalian species. This basophilic polar cytoplasm was common in multilaminar follicles and was not visible in smaller, primordial follicles. In one out of five oocytes stimulated with hCG to complete the first meiotic division, a relatively faint region of cortical basophilia was detectable. Further studies will be needed to ascertain if this nuage-like material has an influence upon the development of oocytes similar to that seen in non-mammalian species.

The Medicina survey of methanol masers at 6.7 GHz

A survey of Class II methanol masers at 6.7 GHz was made in the Northern hemisphere with the 32-m Medicina radio telescope. 42 objects were detected, 20 of them are new detections at 6.7 GHz. Our results show that the detection rate of 6.7 GHz masers toward the inner part of the Galaxy is higher than in other directions. It is conrmed that most of the methanol masers are as- sociated with faint compact HII regions. The 6.7 GHz me- thanol masers show large velocity dispersion and large ve- locity oset from the velocity of parent molecular clouds.

The Manchester occulting mask imager (MOMI): first results on the environment of P Cygni

The design and first use of the Manchester occulting mask imager (MOMI) is described. This device, when combined with the Cassegrain or Ritchey-Chretien foci of large telescopes, is dedicated to the imagery of faint line emission regions around bright central sources. Initial observations, with MOMI on the Nordic Optical telescope (NOT), of the V=4.8 mag P~Cygni environment, have revealed a $\geq$~5~arcmin long [NII] 6584A emitting filament projecting from the outer nebular shell of this luminous blue variable (LBV) star. The presence of a mono-polar lobe older than both the inner (22 arcsec diameter) and outer (1.6 arcmin diameter) shells is suggested.

Spectrophotometry of the planetary nebula KjPn 8

Flux-calibrated low-resolution spectra covering the optical wavelength range from 3400 to 7500 A have been obtained over the central region and the surroundings of the extraordinary planetary nebula (PN) KjPn 8 (PNG 112.5-00.1). The spectrum from the core is of low excitation with Te(N II) = 8000 K and ne(S II) = 550 cm−3. KjPn 8 is found to be a Type I PN according to the original classification scheme of Peimbert & Torres-Peimbert, with enriched He/H and N/O ratios with respect to mean values for PN. Increased O/H, Ne/H and Ar/H ratios over those of average PN reflect the possible metal-rich environment from which the progenitor star formed, and also are similar to those found in the extreme Type I PN He 2-111. The N/H ratio is found to be only moderately high compared to the average PN and consequently, the large O abundance pulls the N/O ratio towards the lower limit of the criterion for Type I planetary nebulae (PNe) in this case. In addition, the spectra of some knots and faint regions in the KjPn 8 surroundings are presented, which show only a few spectral lines. Low electron densities ranging from 100 to 300 cm−3 have been derived in these outer regions.

Star Formation in Disk Galaxies

AbstractWe present results, some preliminary, from a major new study of the star formation properties of a sample of nearby disk galaxies (Ferguson 1997). Our emphasis is on the faint outer regions of disks. Hα images, combined with broad-band images and spectroscopy of HII regions, constrain the present and past star formation rates and chemical enrichment. These data also allow study of faint diffuse ionised gas, which traces the influence of massive stars on their environment, and the structure of the interstellar medium.

Bright Prospects: Comparing the Hα Survey with Large-scale Radio Continuum Emission

AbstractProspects for comparisons between the AAO/UKST Hα survey and large-scale radio continuum emission are considered, with particular reference to the recently completed Parkes 2·4 GHz survey of the southern Galactic Plane. Both these surveys have a high sensitivity to thermal emission, and comparisons between the Parkes work and previous Hα surveys show many objects in common. Possibilities for new detections include: a number of new supernova remnants; the faint extensions and envelopes surrounding ‘classical’ HII complexes, and other faint regions of thermal emission; several active HII complexes, including an outflow of ionised gas from IC 4628 and a number of bi-polar ‘plumes’ of low-density, thermal material apparently associated with HII complexes on the Carina spiral arm.

The Shell of the Recurrent Nova T Pyxidis: A Model Based on Shocks

A model for the shell of the recurrent nova T Pyxidis is presented, consistent with the bulk of observational data on this object. Evolutionary calculations of thermonuclear runaways on the surface of an accreting white dwarf that simulate the observed outburst characteristics of this nova—recurrence time, rise time, time of decline, luminosity—provide the mass of the ejected shell, its composition, and the effective temperature and luminosity of the nova in quiescence (for a white dwarf mass of 1.25 M☉, a core temperature of 107 K, and an accretion rate of 10-7 M☉ yr-1). These results are used as input parameters for the SUMA code, which simulates the physical conditions of an emitting gaseous cloud under the combined effects of photoionization and shocks. The shell model involves two emitting regions besides the central star (which is the main UV radiation source), both resulting from compressed gas behind a shock front. The shocks are assumed to be produced by the collision between two extended shells ejected at consecutive outbursts. As a result of the collision, a secondary blast wave propagates outward into the older ejecta, while a reflected (reverse) shock wave propagates back through the new ejecta. Applying the SUMA code to each zone, we find that different lines are emitted in the two zones, and combined, they account for the entire observed line spectrum. The absolute fluxes in different spectral ranges agree with those derived from observations, assuming a distance of ~2 kpc. The derived abundances imply that mixing has taken place between the nova ejecta and interstellar material. Nevertheless, helium is overabundant and N/O is high. The model accounts for the observed structure of the nebula surrounding T Pyx, including the inner shell, the stagnant outer shell, and the extended faint region beyond it.

Narrow band CCD imaging of four PNe

We present first results of a project to construct and study spatio-kinematical models of selected Planetary Nebulae (PNe). Deep monochromatic CCD images of A8, A4, M2-55, and J-320 were made with the Calar Alto 2.2m telescope and the two interference filters 5005/90 and 6574/104 for the [O III] and Hα+[N II] emission lines. The images were corrected for bias and dark, and flatfielded using MIDAS software, and also corrected for atmospheric extinction to derive the total flux in each emission line. The observed parameters are summarized in Table 1. – A8 (PNG167.0–00.9) has a very symmetric, round appearance with large diameter. The Hα+[N II] image clearly shows a round, limb-brightened ring which is less apparent in the [O III] image. Due to its appearance we can classify it as a late round type according to Balick (1987). −M2-55 (PN G116.2+08.5) has a box-like, quadratic and highly structured inner part (slightly more roundish in [O III]), with four maxima at the corners. The faint outer parts seem to consist of two ovals that are perpendicular to each other. Together, they again resemble a square tilted 45° against the inner one. The Hα+[N II] image is larger than [O III]: The square (distance of maxima) by some 20 percent, the faint ovals by about 10 percent. We can classify this PN as a middle elliptical type. – A4 (PNG144.3–15.5) is a spherical shell, with some definite structure in the brightest parts. This structure forms roughly a ring halfway between the center and the rim. A4 can be classified as an early round type. Both images are quite similar, the Hα+ [N II] maximum lying slightly, about 20 percent, farther from the center. In the very faint outer regions, the [O III]/(Hα+[N II]) ratio seems to increase by a factor of about 5 above the average which is otherwise constant within 10 percent over the whole image. -J-320 (PNG190.3–17.7) is elongated, with one maximum on the main axis, slightly off-center. The Hα+[N II] image has an interesting structure which is not present in [O III]: Two stripes of decreased intensity that are roughly parallel to and on both sides of the main axis. At present, we have no explanation for this feature. J-320 has ansae (small knots found in pairs on opposite sides and at equal distance from the nucleus) usually seen best in the light of low-ionization emission lines. Balick (1987) classified this PN as early type butterfly.

A ROSAT observation of the supernova remnant Kes 79

Kes 79 was observed with the ROSAT Position Sensitive Proportional Counter (PSPC) and High Resolution Imager (HRI). Some X-ray emission comes from a faint outer region, well correlated with the outer shell. Most emission is from a bright diffuse inner region where there are also bright radio filaments. The X-ray spectrum is fitted with a thermal model with temperature 1.3 keV. Variations in spectra from different regions arew small. There is no X-ray evidence for an internal neutron star. Remnant characteristics are derived using a simple blast-wave model. The observed X-ray absorption is less than expected. It is possible that the remnant is closer than the published distance of 10 kpc.

CCD photometry of the globular cluster NGC 5897 - Morphology of the color-magnitude diagram

The paper presents CCD photometry in the B and V bands of the Galactic globular cluster NGC 5897. The color-magnitude diagram (CMD) obtained for this cluster is used to examine the properties of the cluster and to compare the NGC 5897 to the well-known globular cluster M3. It was found that the metallicity of the NGC 5897 is in the range of the metallicity of M3 and that the age of NGC 5897 is about 2 Gyr greater than that of M3. The CMD for NGC 5897 also reveals a significant population of blue straggler stars (BSS) more massive than the cluster subgiant branch stars. A pseudomain sequence is constructed for NGC 5897 and the previously studied (Sarajedini and Da Costa, 1991) global cluster 6101, which includes the BSS and extends to the faintest regions of the unevolved main sequence.

Faint HII regions in the Magellanic Clouds

We present CCD observations of several faint regions of active star formation in the Magellanic Clouds. For the five regions for which we were able to obtain photometric data we have extended the luminosity function (LF) two orders of magnitude below the previous faint limit of 1037 erg s−1 (1). Our preliminary results indicate that the LF turns over at 1036 erg s−1 for the LMC and 1036.5 erg s−1 for the SMC. It is also apparent that much of the Ha emission fainter than 1036 erg s−1 is diffuse or filamentary in nature.

The surface photometry of NGC 3379

Surface photometry is carried out for the photometric standard galaxy NGC 3379 on the basis of two plates in the blue band taken with the Bejing Schmidt telescope. The results, including luminosity profiles, photometric parameters, integrated luminosity distribution, ellipticity and position angle variation, are presented in various forms of figures and tables. Especially our geometric profiles, i.e., ellipticity and position angle variations reach up to ≈5′, much fainter region than that any previous study did. The accuracy of the present data is checked by comparing them with the surface photometry in the literature. We find the zero-point ≈0.12 mag brighter than the calibration of de Vaucouleurs and Capaccioli (1979), which agrees with the values 0.10–0.15 mag difference claimed by recent observations. The systematic differences is found to be less than ≈0.1 mag.

Performance analysis of the stationary-reflector/tracking-absorber solar collector

This is an analytical study of the performance of the stationary-reflector/tracking-absorber (SRTA) solar collector with tubular absorber. The mathematical treatment and the derived formulae are generalized for any rim angle and any absorber-to-reflector diameter ratio. The effects of these two parameters on the average concentration ratio are investigated. Different multi-reflection zones of the mirror are identified. Their contributions to the total concentrated power and the local concentration ratio, at different absorber points, are assessed. The concentration profile along the absorber is determined under different conditions. The influence of mirror reflectance on the flux density at different points is evaluated. The circumferentially-distorted concentration profile at times of oblique incidence is displayed. The absorber surface is divided into bright, faint, and dim regions. A mathematical procedure is presented to contour these regions. Their occurrence and areal growth is shown to be dependent on the rim angle and diameter ratio.

A view of the galactic H-alpha background - L = 208-218 deg, B = -2 to +8 deg

view Abstract Citations (48) References (30) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A View of the Galactic H alpha Background: 208 degrees <=l <=218 degrees ; -2 degrees <=b <= +8 Reynolds, R. J. Abstract Faint, diffuse H-alpha emission from the interstellar medium has been mapped at 1-deg angular resolution and 12 km/s radial velocity resolution within an 11 x 11 deg region of the Galactic plane. The observations reveal that warm, ionized gas is widespread throughout the Galactic disk and that it has a complex morphology with faint, previously unidentified H-alpha emission regions superposed on a more diffuse H-alpha background. The H-alpha intensities indicate that, in the diffuse interstellar medium outside the discrete H II regions, the mean hydrogen ionization rate is about 3.5 x 10 to the 6th/s per sq cm column perpendicular to the Galactic disk and the mean square electron density of about 0.01 per cm to the 6th near the midplane. This warm, ionized gas appears to contain a substantial fraction (perhaps most) of the H(+) in the interstellar medium. The source of this ionization is not understood. Neither the faint emission regions nor the more diffuse emission appear to be associated with traditional H II regions immediately surrounding early-type stars. The high forbidden S II line 6716/H-alpha intensity ratios in the background clearly rule out scattered light as a primary source of the emission. Publication: The Astrophysical Journal Pub Date: December 1987 DOI: 10.1086/165811 Bibcode: 1987ApJ...323..118R Keywords: Background Radiation; H Alpha Line; Interstellar Matter; Milky Way Galaxy; Nebulae; Angular Resolution; Astronomical Maps; Early Stars; Gas Temperature; Ionized Gases; Radial Velocity; Astrophysics; GALAXIES: THE GALAXY; INTERSTELLAR: MATTER; NEBULAE: GENERAL; NEBULAE: H II REGIONS full text sources ADS | data products SIMBAD (4)

An improved photographic process for convergent beam electron diffraction applications

AbstractThe use of a surface developer, pyrocatechol, to process transmission electron microscope negatives has been shown to have significant advantages over the conventional D‐19 process. The process described here is tolerant of a large margin of error in the electron exposure and produces a negative that not only retains details both in the highlight as well as the faint regions, but also preserves local contrast. These characteristics are particularly useful in convergent beam electron diffraction applications where one encounters a wide contrast range. Improved acuteness and an enhanced signal to noise ratio due to the prolonged exposures associated with this process have also been observed.

Performance analysis of the stationary-reflector/tracking-absorber solar collector

This is an analytical study of the performance of the stationary-reflector/tracking-absorber (SRTA) solar collector with tubular absorber. The mathematical treatment and the derived formulae are generalized for any rim angle and any absorber-to-reflector diameter ratio. The effects of these two parameters on the average concentration ratio are investigated. Different multi-reflection zones of the mirror are identified. Their contributions to the total concentrated power and the local concentration ratio, at different absorber points, are assessed. The concentration profile along the absorber is determined under different conditions. The influence of mirror reflectance on the flux density at different points is evaluated. The circumferentially-distorted concentration profile at times of oblique incidence is displayed. The absorber surface is divided into bright, faint and dim regions. A mathematical procedure is presented to contour these regions. Their occurrence and area growth are shown to be dependent on the rim angle and diameter ratio.