The electron temperature distributions and internal kinematics of seven diffuse nebulae

A Fabry-Pérot spectrophotometer is used to derive values of the intensity ratio H/[Nii] at 98 points in the seven bright diffuse nebulae M8, M20, M16, M17, NGC7000, M42, IC434. The fraction of nitrogen in the singly ionized state is estimated in the different objects, and is found to be sufficiently constant within any one nebula so that the above intensity ratio may be used to derive accurate electron temperature distributions. The position of the peak of the nebular line, its excess non-thermal width, its shape and relative intensity are used to derive kinematical models of these objects.It is found that values of H/[Nii]1 are representative of the bright central cores of these nebulae. Temperatures between 7000K and 12000K were derived in the different objects. Although some of this apparent variation is due to the different conditions of excitation in the various nebulae, it is shown that a convincing progression of temperature in M8, M16, M17 is supported by radio recombination line results. The temperature variation within any one object was generally significantly less than 1500K.No evidence was found for velocities of mass motion at more than twice the speed of sound. Relative radial velocities of generally less than 15 km sec^–1 characterized the velocity fields of M8, M20, M16, M42. The velocities in M17 were measured as about 20 km sec^–1. Motions in NGC 7000 and IC 434 were much lower (5 km sec^–1) although here the number of points taken was too small to construct meaningful kinematical models.It is concluded that the internal motions of radiatively ionizedHii regions of Pop. I will not significantly affect the results of existing surveys for determining the rotation of the galaxy with radial velocities deduced from nebular emission lines.     

Pseudo-resonance absorption lines in planetary nebulae: Discovery?

The possibility of the formation of pseudo-resonance absorption lines in planetary nebulae is predicted only theoretically. However, this has not been confirmed by direct observations. In the present article an attempt has been made to show, as a result of careful analysis of IUE spectral recordings for a group of planetary nebulae, that the existence of one pseudo-resonance line 1300 SiIII is without doubt at least in spectra of three planetary nebulae: NGC 2610, NGC 3587, and NGC 6891. The presence of this line in the spectra of the other three planetary nebulae, NGC 6210, IC 3568, and IC 4776, seems to be probable. The role of the interstellar selective absorption, the blending effect by the resonance lines of SiII,Oi, andSi in the formation of the pseudo-resonance line 1300 SiIII as well as the possibility of formation of this line in the photosphere of central star of nebula were analysed.     

Properties of the solar chromosphere Hα spicules as observed spectrally

Time succession of 25 H spicules has been studied. The spectra are obtained at a height of 6 arc sec during 21 min (38 pictures) with the 53 cm Lyot coronagraph. Total intensities W, widths and radial velocities V _r are determined (about 650 H line profiles). For 14 spicules the sign of V _r varies, for the rest the sign variation is absent or it is doubtful. Characterized period of V _r variation is 3–7 min with a mean amplitude of ± 4km s^–1. W and also vary with a similar period and mean amplitudes equal to 50% and 30% respectively. dependence of W (Figure 1) points to the existence of two spicules groups: group I (70%) characterized by relatively small W and (mean values are 0.08 Å and 1.3 Å respectively); group II comprising brighter (W 0.13 Å) spicules with wider profiles ( 1.6 Å). Group II may consist of the unresolved, superimposed group I spicules. We believe, that H spicules involve formations consisting of separate elements having the temperature of 6000 K and non-thermal velocities of 25 km s^–1.     

Self-consistent photoionization models of planetary nebulae luminescence: stellar ionizing continuum,nebular abundances,and evolution of the envelopes

The modern self-consistent photoionization model of planetary nebula luminescence is described. All of the processes which play an important role in the ionization and thermal equilibrium of the nebular gas are taken into consideration. The diffuse ionizing radiation is taken into account completely. The construction of the model is carried out for the radial distribution of gas density in the nebular envelope which is consistent with isophotal map of the nebula. The application of the model is illustrated on the example of the planetary nebulae BD+30°3639 and NGC 7293. It is shown that the continuum of the central star at 912 Å does not correspond to the blackbody spectrum but agrees with the spectrum of corresponding non-LTE model atmosphere. The radial distributions of electron density, electron temperature, and other parameters in the nebular envelopes are found.The evolution of the radial distribution of gas density in the planetary nebulae envelopes is investigated. Approximative analytical expression which describe both such distribution and its change with time is adjusted. It is shown that the nebular envelope is formed as a result of quiet evolution of the slow stellar wind of star-precursor, and the formation of the envelope begins from the decrease of star-precursor's mass loss rate. Obtained radial distributions of gas density in the envelopes of young nebulae rule out the idea that the planetary nebula is formed as a result of a rapid ejection of clear-cut envelope. So, there is no necessity for the superwind which is used for this purpose in theoretical calculations.A new method of the determination of planetary nebulae abundances is proposed. Unobserved ionization stages are taken into account with aid of the correlations between relative abundances of various ions which had been obtained from the grid of the photoionization models of planetary nebulae luminescence. Simple approximative expressions for the determination of He/H, C/H, N/H, O/H, Ne/H, Mg/H, Si/H, S/H, and Ar/H are found. The chemical composition of 130 Galactic planetary nebulae is revised. A comparative analysis of the abundances in the Galactic disk, bulge, and halo nebulae is carried out.     

Expanding shells within the Helix nebula (NGC 7293)?

Filter photographs and Fabry-Pérot interferograms of the Helix nebula reveal evidence of approximately spherical expansion. Heliocentric radial velocities from +44 to –51 km s^–1 have been detected over the centre of the nebula. A dumb-bell configuration, viewed at a small angle to the longest axis, is proposed to explain many of these observations.     

Infrared photometry of eight planetary nebulae

We discuss the infrared (IR) (1.25–5 µm) photometry of eight planetary nebulae performed in 1999–2006. For all of the nebulae under study, we have firmly established IR brightness and color variations on time scales shorter than one year and up to 6–8 years. The greatest IR brightness variations were observed in IC 2149, IC 4997, and NGC 7662. Their J magnitudes varied within 0 _. ^m 2–0 _. ^m 25. In the remaining objects, the J magnitude variations did not exceed 0 _. ^m 15. All of the planetary nebulae under study exhibited IR color variations. Based on the IR photometry, we have classified the central regions of the planetary nebula NGC 1514 and of the northern part of NGC 7635 seen through a 12″ aperture as a B(3–7) main-sequence star (NGC 1514) and a ～O9.5 upper-main-sequence star (NGC 7635). The nebulae IC 4997 and NGC 7027 exhibited an excess emission (with respect to the emission from a hot source) at λ > 2.5 µm.     

The Hα observations of the California Nebula (NGC 1499) with DEFPOS

A dual étalon Fabry‐Pérot spectrometer called DEFPOS has been used for observing physical properties of HII regions and planetary nebulae since May 2007 (Aksaker et al. 2009, 2011; Şahan et al. 2009; Şahan 2011). In this study, the Hα measurements of the HII region NGC 1499 (California Nebula) have been investigated with a 4′ circular field of view over a 200 km s^–1 (4.4 Å) spectral window. These measurements provide information about the densities, line widths, and radial velocities of the surrounding NGC 1499 nebula. The intensities, the radial velocities and the line widths of the Hα emission line vary from 397.75 R to 1044.14 R, –4.88 km s^–1 to –1.02 km s^–1, and 36.72 km s^–1 to 42.81 km s^–1, respectively (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Observations des bords brillants dans NGC 281, IC 434 et M 16

Sommaire Les photographies monochromatiques en H, [Nii] 6584 et [Oiii] 5007 ont été obtenues sur NGC 281, IC 434 et M 16 eu vue de la détection et de l'étude des bords brillants. A partir de ces photos, on accède à la carte d'égal rapport [Nii]/H grâce à la méthode décrite par Louise et Sapin (1972). A l'exclusion des bords brillants, ce rapport varie très peu à l'intérieur d'une même nébuleuse. Par contre à l'approche des fronts d'ionisation, il augmente de façon spectaculaire et systématique.Le renforcement de la raie [Oiii] vers les bords brillants suggère la présence des inhomogénéités (globules ou/et filaments) et le rôle possible que jouent les mécanismes d'échange de charges étudiés par Aller et Keyes (1980).

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Observations of bright rims in NGC 281, IC 434 and M 16

Monochromatic plates are obtained in H, [Nii] 6584 and [Oiii] 5007 lines for three Hii regions: NGC 281, IC 434 and M 16. They allow both detection and physical studies of bright rims. Indeed, it is shown that bright rims appear most contrasted on [Nii] and [Oiii] plates. Furthermore, maps of ratio [Nii]/H are derived from the method described by Louise and Sapin (1972). This ratio remains practically constant within the nebula, except for bright rims where it increases. This may be understood by means of both increasing abundanceN(N⁺/N(H⁺) and temperature following to the model of Mallik (1975).The [Oiii] enhancement towards bright rims in M 16 suggests the presence of inhomogeneities (globules or/and filaments) and the possible role played by charge exchange mechanisms as pointed out by Aller and Keyes (1980).

     

On actual presence of discordant-redshift galaxies in compact groups

Hickson's compact galaxy groups were classified using the statistical criterion which includes the radial velocities of galaxies as well as their relative positions. These groups on the whole and their components are identified as the confident and probable non-chance ones as well as probable and confident chance ones. All confident chance objects have the discordant radial velocities (the differences of radial velocitiesDV [1000; 20000] km s^–1). The special class of objects bright discordants is selected. These galaxies have the discordant radial velocities withDV [825; 8440] km s^–1 and have a strong tendency to be the brightest components of their groups. The lowest difference of radial velocities for the last class of objects DV = (1.0±0.2) × 10³ km s^–1 and we accept this value of DV as the lowest value of discordant radial velocities. It is found that the biggest part of Hickson's compact groups consist of non-chance aggregations of galaxies and some of the cases of discordant-redshifts require a special study in order to explain their origin from a dynamic or some other point of view.Present address.     

On the chromospheric velocity field in sunspot regions

The wavelength shifts of approximately 8000 absorption elements in the H-line from spectra of 66 different sunspot regions have been measured.The average velocity field in the chromosphere close to sunspots is determined. Inside 15000 km from the spot's penumbral rim the average velocity vector is directed towards the spot and downwards in the chromosphere; the angle with the horizontal direction is on the average equal to 20°. The magnitude of the average velocity vector shows a maximum of 6.8 ± 1.2 km/sec just outside the penumbral rim and decreases quickly with increasing distance from the spot. Outside 15000 km from the penumbral rim the average velocity vector is small (-0.7 km/sec) and directed nearly vertically outwards from the sun. No significant tangential component of the average velocity field is found.The deviations of the individual elements from the average velocity field are on the average larger than the value of the average velocity. The total rms deviation in the line of sight velocity is equal to 6.8 km/sec. Thus, a large number of elements, as used in this investigation, is required to give significant values of the average velocity vector.We have also observed velocities in the penumbra. The average velocity vector is here probably small and its direction uncertain. The rms deviation in the line of sight velocities observed in the penumbra is equal to 7.5 km/sec.     

A kinematic study of orion nebula in the emission line [S II] 6731 Å

Fabry-Perot Interferometric observations were made on Orion Nebula in the forbidden emission line [S II] 6731 Å line. The observed field is about 6 × 6 on the face of the nebula and it covers the Orion Trapezium stars and the nearby regions. The relative line of sight velocities which denote the average deviations from the systematic velocities were derived at a large number of points in the nebula. Velocities were found to show a gradient towards the north of Trapezium stars. Large blue shifted velocities were found at the nebular boundaries, probably associated with the ionization fronts. The observed velocities, in general, show agreement with the flow model of Balick, Gull and Smith (1980).     

The dynamics of double-envelope planetary nebulae

A number of criteria are elaborated based on the careful analysis of nebulae images which confirm the version of the origin of double-envelope planetary nebulae by means of dynamical separation but not by multiple ejection. The importance of stellar winds in the origin of the gigantic halos around double envelope nebulae is outlined. The problem concerning the existence of two types of filamentary planetary nebulae (Figure 8) is raised: type A, filaments are the fragmentations of the Rayleigh-Taylor instability, the result of dynamical interaction of the envelope with the outer interstellar matter (NGC 6543), and type B, the origin of filaments is connected with the Magnetic field fluctuations (A 43, A 72).The possibility of the origin of three-envelope nebulae in the framework of the dynamic separation version is discussed (NGC 7293). Attention is paid to the impossibility of outbursts with low velocities (20–30 km s^–1) from hot stars, i.e., the nuclei of nebulae.     

A study of the far infrared counterparts of new candidates for planetary nebulae

A search (using the Infrared Astronomical Satellite IRAS point source catalogue) for infrared counterparts of the fourteen new candidates for planetary nebulae of low surface brightness detected by Hartl and Tritton (1985), resulted in only five identifications. The infrared sources of four of these candidate nebulae are found within 5 are sec of their optical position and the fifth one within 1 are min. Two of the five nebulae identified with infrared sources are classified as true, one as probable and two as possible by Hartl and Tritton (1985). All the five nebulae are found in regions of high cirrus flux at 100 m. These nebulae are all found to have both point sources as well as small size extended sources (in the IRAS scan windows centred on the sources), with numbers varying from field to field. The infrared emission from these nebulae have dust temperatures 100K (characteristic of planetary nebulae). Four of the nebulae appear to be faint in the infrared (just as in the optical band) with total infrared flux of 2×10^–13 W m^–2. Only the PN candidate No. 12 appears to be very bright in the infrared. It is likely that part of the emission is from extraneous sources in the line-of-sight to the nebula.     

Observations of the planetary nebula NGC 6853 at [Nii] 6584 Å

New Observations of the [Nii]6584 Å line have been made over the surface of the Dumbell nebula (NGC 6853). The observed lines at the centre of the nebula disc exhibited line splitting of 54.3 km s^–1. The lines appeared double at the centre of the nebula and became single at the boundary. These observations are discussed and compared with those obtained by previous workers.     

The temperature and internal kinematics of M8

A photoelectric Fabry-Pérot spectrometer is used to record the line profiles of H and [Nii] at 22 points in the nebula. The ratio of intensity H/[Nii] is used to derive an electron temperature distribution with values between 5700° and 9100° showing a peak at the centre of density. These temperatures are compared with the H Doppler temperatures to estimate excess velocities of mass motion. Together with the shifts of the H line centres, these lead to an evaluation of the velocity field in the nebula.It is suggested that the nebula consists of a core expanding at about ±10 km/sec^–1 surrounded by a thick peripheral shell in which large scale mass motions are small. Non-thermal broadening suggesting turbulent velocities at about the speed of sound is observed in this shell and is attributed to small scale dynamic effects in a non-smooth density distribution. The effect of such expanding cores on heliocentric velocities of galacticHii regions is discussed.     

Hα line measurements from ten diffuse galactic sources using the DEFPOS facility

The hydrogen Balmer‐α emission line spectrum of ten diffuse ionization sources in the Milk Way – NGC 40 (WC8), NGC 2022, NGC 6210, NGC 6618 (M17, Sh2‐45), NGC 6720 (M57), NGC 6781, NGC 6888 (Sh2‐105), NGC 6992 (Sh2‐103), NGC 7635 (Sh2‐162,) and IC 1848 (Sh2‐199) – has been investigated using a dual etalon Fabry‐Pérot optical spectrometer (DEFPOS) aatached to the 150 cm RTT150 telescope at TUBITAK National Observatory (TUG, Antalya, Turkey: 36° 51′ N; 30° 20′ E; elevation: 2547 m). All of our galactic Hα observations discussed in this paper were carried out during the nights of 2013 June 21–24 with exposure time of 3600 s. As main results the intensity, the full width at half maximum, and the radial velocity with respect to the LSR have been determined for each data set. The intensities, the radial velocities, and the line widths of the Hα emission line vary from 59.15 to 8923.44 R, –46.72 to +54.07 km s^–1, and 31.4 to 48.01 km s^–1, respectively. The radial velocities and the half‐widths of the Hii regions and planetary nebulae determined from our measurements are found tobe consistent with values given in literature, especially with those in Schneider et al. (1983) and Fich et al. (1990). (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The structure of a typical double-ring planetary nebula NGC 2392

Monochromatic photographs in H, [Nii] 6584 and [Oiii] 5007 Å show many different details in the morphological structure of the Eskimo Nebula (NGC 2392). H and [Nii] images show, in a first approximation, similar structure (elliptical inner ring and broken outer ring) whereas both rings in [Oiii] are quite circular and regular in brightness. A photometric study using the method described by Louise (1974) gives various geometrical parameters of both rings which are practically the same for the observed lines. In other words, the classical stratification structure in planetary nebulae is not clearly observed in NGC 2392, in good agreement with previous observations (Wilson, 1950). This fact is probably a consequence of the peculiar structure in the geometry of the nebula. A model consisting of an inner toroid surrounded by a spherical shell is proposed to account for both photometric and spectroscopic observations.     

Measurements of radial velocities of α and: A spotted HgMn star?

Measurements of radial velocities from the SiII 6347A and 6371Alines and the HeI 6678A line based on observations of 1989–1994 are examined. The variability of the line shapes over the 96.6-day orbital period is analyzed. Evidence for a second component is found from lines in the spectrum of And which correspond to the silicon lines 6347 and 6371A. The preliminary value for the rotational velocity of the secondary component is 100–120 km/sec. Analysis of the variability of the radial velocities of the HeI 6678A line during the night has given the rotational period of the star of P_rot=I^d.012344 and indicates an inhomogeneous distribution either of the helium abundance or of the physical conditions over the surface. Thus, we have the first evidence for the existence of spots on the surface of an HgMn star.Translated fromAstrofizika, Vol. 39, No. 3, pp. 375–384, July–September, 1996.     

Interaction of low- and high-velocity systems in the galaxy NGC 1275

Published data on gas systems of different velocities in the galaxy NGC 1275 are examined. One of the systems is associated with NGC 1275 (low-velocity system — LV); the other is approaching it at a velocity of 3000 km/sec (high-velocity system — HV). Many of the collected results obtained from spectra and from direct images in the ultraviolet, optical, red, and infrared indicate interaction of these systems. The interaction is exhibited in the same shape and spatial distribution of the gas filaments in both systems, in the elongation of some of them toward the nucleus of the galaxy, and in the increase in brightness of the HV gas near some of the clusters of young stars of the LV system. Gas of the HV system is observed at a distance of O.5 (170 pc) from the nucleus of the galaxy, while intermediate-velocity gas (IV — 600–1520 km/sec relative to the velocity of NGC 1275) is detected at distances less than 7 (2.5 kpc). We presume that the rare cases of the detection of IV gas are related to the use of H_a observations primarily: at the velocities of 600–900 km/sec, the H_a line of the IV gas blends with the [NII] 6584Å line of the LV gas.Translated fromAstrofizika, Vol. 39, No. 4, pp. 567–584, November, 1996.     

Luminosity and colour distribution in the interacting system NGC 7770-71

Detailed surface photometry for the SB(s)a galaxy NGC 7771 has been carried out in the blue spectral band. Isophotes, luminosity profiles, and photometric parameters are obtained from photographs collected with the 74 inch telescope of Kottamia Observatory, Egypt. The total apparent magnitudem _T =13.08 with maximum dimensions 3.6±0.5×2.7±0.5 (at threshold µ _m = 27.38 mag s^–2). The absolute magnitude isM _T =–21.70 if the distance is =90.2 Mpc. The major axis is in position angle =69°.5±1° and the mean axis ratio of the outer regionsq=b/a=0.45 corresponds to an inclinationi=66°. The equivalent effective radiusr _e ^* =0.29 and the effective surface brightness µ _e = 22.30 mag s^–2.The equivalent luminosity distribution has been decomposed into two main components, anr ^1/4 spheroid and an exponential disk. The total apparent magnitudes of the spheroidal and disk components are 14.36 and 13.48, which correspond to contributions of 31 and 69% to the total blue luminosity, respectively.