Ic Field Research Articles

The Structure and Dynamics of the Early-Type Resonance Ring Galaxy IC 4214. II. Models

The first paper in this series presented optical (UBVI) and near-infrared (H) surface photometry and Hα Fabry-Perot interferometry of IC 4214, an excellent example of a multiringed galaxy with a weak bar. In the present paper, we analyze the nonaxisymmetric gravitational potential of IC 4214, as defined by the near-infrared data. The gas behavior is modeled with two-dimensional sticky particle simulations that employ a rigidly rotating nonaxisymmetric potential. Our goals are to interpret the morphology and velocity field of IC 4214 and to obtain a model from which the bar pattern speed, halo contribution, and relative bulge and disk masses can be deduced. We also study the orbital families in the derived IC 4214 model. A fairly good match, in both morphology and kinematics, is obtained for Ωbar ≈ 40 ± 5 km s-1 kpc-1, placing the bar corotation slightly beyond the end of the bar (rbar/rcr ≈ 0.72 ± 0.05). The deduced bar amplitude implies that the visible mass of the disk dominates over the unseen halo (Mdisk/Mhalo > 3–4). Moreover, our model accounts quantitatively for the large difference in the orientation of IC 4214 as derived in our first paper with photometric and kinematic methods.

Anomalous dependence of the critical current of 45° grain boundaries in YBa2Cu3O7−x on an applied magnetic field

Grain boundaries grown by the biepitaxial technique do not show Fraunhofer-type critical current Ic vs. magnetic field Ha dependences, which are a hallmark of standard Josephson junctions. To clarify the reason for this unusual behavior, we have fabricated asymmetric 45° grain boundaries using the bicrystal technique and analyzed their Ic (Ha) characteristics. These characteristics crisply show a number of remarkable features, which suggest that due to the particular orientation of these junctions, their Ic (Ha) dependence is intrinsically non-Fraunhofer. Conventional models, relying on standard tunneling and a superconducting order parameter with s-wave symmetry, do not account for the Ic (Ha) characteristics observed.

Physical parameters of the intermediate age open cluster IC 1311: Clues for the theory of stellar evolution

The results of a UBVR photometric study in the field of the open cluster IC 1311 are presented. A comparison with previously published results on NGC 7044, based on measurements secured during the same observing run, leads to a self-consistent constraints to the parameters of the cluster. The location of selected samples of giant and unevolved dwarf members in the U-B vs B-V diagram is used to simultaneously compute the color excess E(B-V) and the metallicity (Fe/H). Distance modulus and age are estimated by the Zero Age Main Sequence (ZAMS) fitting method, and by the use of theoretical isochrones, based on models computed with and without the consideration of convective overshooting during the phases of core nuclear burning. The adopted set of values is: E(B-V) = 0.28, (Fe/H) = 0.0, DM = 13.9, Age = 1.6 x 10<SUP>9</SUP> yr. The mass function for the cluster main sequence has been estimated, with a slope x = -2.58, significantly steeper than the Salpeter initial mass function (IMF) (-1.35). The uncertainties in the adopted values for the cluster parameters, due to interstellar reddening, and to the calibrations of theoretical luminosity and effective temperature in terms of observational quantities, are also addressed. The discrepancies between the observational color-magnitude (CM) and the model isochrones, in particular the difference between observed and predicted luminosity of the red giant clump (RGC), are sensibly reduced for the models with convective core overshooting. The results indeed suggest the need of increasing the overshooting effectiveness beyond the values considered up to now in evolutionary computations.

Discovery of Cepheids in IC 4182: Absolute peak brightness of SN IA 1937C and the value of H[SUB]0[/SUB

view Abstract Citations (156) References (41) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Discovery of Cepheids in IC 4182: Absolute Peak Brightness of SN IA 1937C and the Value of H 0 Saha, A. ; Labhardt, Lukas ; Schwengeler, Hans ; Macchetto, F. D. ; Panagia, N. ; Sandage, Allan ; Tammann, G. A. Abstract Repeated imaging of a field in the Sdm galaxy IC 4182 with the Wide Field Camera of the Hubble Space Telescope has led to the discovery of 28 Cepheid variables. The distance modulus to this galaxy, derived from the Cepheids, is (m - M) = 28.36 +/- 0.09, and the absolute magnitude at peak brightness of the Type Ia supernova SN 1937C which appeared in IC 4182 is M_V_(max) = - 19.72 +/- 0.13. The Hubble diagram using peak V magnitudes of distant (Virgo cluster and beyond) Type Ia supernovae (selected a priori on the basis of light curve and spectral conformity with the prototype) shows an observational random scatter of 0.36 mag, with evidence that the intrinsic scatter is even smaller. Using the observed scatter to estimate the uncertainty of calibrating the Hubble diagram using only the single calibrating supernova SN 1937C, it is shown that H_0_ = 52 +/- 9km s^-1^ Mpc^-1^. Publication: The Astrophysical Journal Pub Date: April 1994 DOI: 10.1086/173957 Bibcode: 1994ApJ...425...14S Keywords: Brightness; Cepheid Variables; Computational Astrophysics; Cosmology; Galaxies; Interstellar Extinction; Spaceborne Astronomy; Supernovae; Astronomical Photometry; Color-Magnitude Diagram; Hubble Diagram; Hubble Space Telescope; Light Curve; Astrophysics; STARS: VARIABLES: CEPHEIDS; COSMOLOGY: OBSERVATIONS; COSMOLOGY: DISTANCE SCALE; GALAXIES: INDIVIDUAL ALPHANUMERIC: IC 4182; STARS: INDIVIDUAL ALPHANUMERIC: SN 1937C full text sources ADS | data products SIMBAD (13) NED (2) MAST (1) ESA (1)

High Resolution Observations of the Magnetic Field in IC 342

The face-on spiral galaxy IC 342 is known to possess an axisymmetric spiral magnetic field (ASS) with magnetic field lines being orientated inwards everywhere at least in the analyzed radial range between 5 and 13 kpc1 (Krause et al., 1989a; Sokoloff et al., 1992). The ASS field configuration seems to be even with respect to the galactic plane.

RR Lyrae stars in Local Group galaxies. IV - IC 1613

Deep charge-coupled device images of a field in IC 1613 away from the star forming central regions were taken with the '4-shooter' on the Hale 5 m telescope, and processed to find photometrically measure variable stars. Fifteen RR Lyrae stars were found, and periods, light curves, and finding charts for them are presented. The mean magnitude of RR Lyrae stars in this galaxy is deduced to be 24.90 mag. Assuming the absolute g magnitude for RR Lyraes to be Mg = 0.73 mag, and using extinction Ag = 0.07 mag, a distance modulus of 24.10 +/- 0.27 mag is derived. The finding of RR Lyrae stars indicates the unambiguous presence of an old population. The distance modulus derived from them is smaller than that derived from the Cepheids by an amount which is dependent upon the RR Lyrae zero-point calibration adopted, and may be as large as 0.3 mag. The difference has the same sense and magnitude as the discrepancy in the LMC. The probable sources of the problem are discussed.

A numerical method of solving a heat - mass transfer problem in porous media with moving boundary

In the framework of the methods, of multiphase media mechanics the thermo it hydrodynamic process induce by interaction between high-frequency electromagnet ic field and porous medium (first component) containing the second component, which can melt at the temperature Tm and the fluid phase of the latter can move to pressure gradient, is considered. This problem is solved by the combination of native method with sweep method. The effectiveness of iterative coefficient is ermined.

Radial velocities in the open cluster IC 2391

We have determined radial velocities for 31 stars in the field of the open cluster IC 2391, and derived the percentage of probable radial-velocity variables. We improved the orbit of one previously known spectroscopic binary, and confirmed the existence of two double-line binaries. We discussed with such data the membership to the cluster, the average cluster radial velocity and compared the incidence of short-period binaries among the Main-Sequence members of IC 2391 with the incidence for other clusters with similar average axial rotation of its members.

Selective Epitaxial Growth Followed by in Situ Deposition of a- or Poly-Si for Seeded Soi.

AbstractSelective Epitaxial Growth (SEG) techniques find a growing number of applications in the field of Si IC's, such as, lateral isolation, vertical interconnects, seeded recrystallisation etc. In the present work, the use of Si SEG by CVD combined with in-situ deposition of a- or poly-Si for the improvement of SOI obtained by Zone Melting Recrystallisation (ZMR) or by Lateral Solid Phase Epitaxy (SPE) is described. The principle application for which the present work is intended is Three Dimentional (3D) Integration. One of the main constraints imposed on process is thermal compatibility with previously executed process steps. Hence the need to reduce the thermal budget for the Selective Epitaxial Growth as much as possible.

Interstellar Magnetic Fields

Methods of investigating interstellar magnetic fields in spiral galaxies are reviewed. Linearly polarized radio continuum emission yields information about strength and structure of the field. Data are available for our Galaxy and several nearby galaxies. The field strengths vary between 3 and 13 , μG; a correlation with the average surface mass density of the galaxies is indicated. The field of M31 is probably concentrated in a ring-like torus, as predicted by the dynamo theory. The field structure of M33, however, appears to be bisymmetric as expected in the primordial theory of field origin. Other candidates for a bisymmetric field structure are M51, M81, M83, NGC 2903, and NGC 6946, but the observations are not yet conclusive. The magnetic field in IC 342 is too complicated to be described in terms of a simple model. The interaction processes between the field and the various components of interstellar gas should be investigated in more detail.

A Digital Color Video Camera Using A Single-Chip Solid-STate Image Sensor

Recent progress in the field of digital ICs and LSIs has brought digital television/video circuitry almost a reality consumer applica-tions, but not quite. Although there have been several papers describing digital signal processing for consumer video cameras,1)2) there remains a number of problems to be soloved before making these cameras viable. Higher speed, higher accuracy and lower power consumption, for instance, are required for an ADC. The yield rate of image sensors are to be improved substantially.

DDO PHOTOMETRY OF THE OPEN CLUSTER IC 4756.

ABSTRACT DDO photometry is presented for 13 red stars in the field of IC 4756, ten of which are classified as proper-motion cluster giants. Of these ten, one is found to be a dwarf, in agreement with the uvby photometry of Schmidt (1978). The strength of the delta CN cyanogen excess parameter for five of the giants indicates that the cluster has essentially solar abundance.

Torsion contributions to the magnetic field of a spinning charge

In fact , even if torsion does no t di rect ly in terac t wi th the e lect romagnet ic field, there is a coupl ing between torsion and the v i r tua l pairs of fermions, produced according to the v a c u u m polar izat ion effect, which gives rise to the photontorsion in terac t ion (1) displayed in (1) (notice tha t we have assumed a flat metr ic tensor, since we wan t to eva lua te the specific torsion contr ibut ions , apar t f rom the usual R ieman iann terms (2)). We like to stress, in this paper , t ha t an electric charge, in te rac t ing wi th a cons tan t torsionic background, can produce a s tat ic magnet ic field even in its rest system. Consider in fact a poin t l ike charge distr ibut ion, ~ ( x ) ~ e~(x), placed in an ex te rna l torsionic background which we assume generated, according to the Einste inCaf tan theory, by a cons tant semi-classical spin d is t r ibut ion (a) at rest wi th the charge density. We have then Qkuk~0, where u k is the 4-veloci ty vector of the charged part icle.

CCD Star Sensor for Fine Pointing Control of Spaceborne Telescopes

A star sensor for measuring small pointing errors in astronomical telescopes is described. By using solid-state imaging arrays (CCD's) to track guide-star images, this design realizes a number of performance advantages relative to more conventional approaches. Specific topics include star image position measurement, CCD sensitivity including color effects, and performance simulation results. Experimental results for CCD's operating at temperatures below 100 K are also summarized. Two telescope configurations are considered to illustrate the range of possible applications of this technology: 1) a large orbiting telescope for general astronomy requiring a multi-CCD sensor, and 2) a Space^Shuttle-based infrared observatory operating at 20 K. Although the requirements and configurations of these applications are widely different, the CCD approach offers substantial advantages to both systems. INE pointing control of large astronomical telescopes in space requires star trackers of extreme accuracy and stability. Pointing errors as small as a few percent of a star image diameter must be measured and corrected to prevent the resulting image motion from significantly degrading image quality. In this paper, we describe a general fine pointing sensor (FPS) design approach which uses charge coupled device (CCD) imaging arrays to track focal plane star images. Since CCD's provide accurate positional information regardless of where the image falls within the field-of-view, the proposed sensor design can accommodate wide variations in guide-star geometry without moving parts. This advantage, coupled with the fact that several stars can be tracked simultaneously (using one or several CCD's), makes the CCD approach a strong candidate for application to a variety of future space-based astronomical telescopes now being planned by NASA. CCD imaging arrays have several qualities which make them attractive for star tracking. A natural coordinate system is defined by the array of photosensitiv e elements which are not dependent on electromagnet ic deflection fields (as in the case for vidicons and image dissectors). Other advantages include high sensitivity, low operating voltage and the ability to survive exposure to strong light. The quantum efficiency of these detectors, combined with their efficient use of signal integration time (all elements integrate simultaneously), makes the noise performance of CCD trackers generally competitive with other approaches limited only by quantum noise (photon counting). In many cases, further noise reductions may be achieved by tracking several stars, simultaneously, on a single CCD.! One potential limitation of using CCD's for star tracking is the limited number of sensing elements (pixels) available with present arrays. Currently, the maximum array size is in the

Evolution operator for bloch electrons in external electric field

The s tudy of mot ion of Bloeh electrons ira the presence of au externa l e lectr ic field cons t i tu tes an impor t an t area in sol id-s ta te physics. The m~iden work in the a rena is t ha t of Zener(~), concerning wi th wha t is t e rmed as ~ Zencr tunncling~). A large number of theore t ica l papers came up dur ing m a n y past years regard ing var ious aspects of the motion of Bloch electrons in the presence of an ex te rna l electr ic field. Bulk of these works (~..4) have widely deal t wi th Zener tunne l ing as well as t he exci t ing phenomenon , named as, (, %~annier Stark L~ddcrs ~; in such inves t iga t ions , one is requi red to use a wave fune{ion, which describes the behav iour of t im electron under the combined a(.t ion of the periodic crys ta l po ten t i a l and the externa l e lectr ic field. IIousTO~(~) was the first worker to propose a w~ve funct ion for th is purpose, mak ing use of the fa.ct t ha t the wave vec tor var ies l inear ly wi th t ime in presence of the externa l e lectr ic field. Houston ' s wave funct iou has since been widely used in s tudying phenomen~ like Zoner tunneling, s tark laddel 's etc. (.z.~.6.~). ]n recent years, the ide~ of evolu t ion opera tor has been explo i ted by many workers in s tudying the behav iour of Bloch electrons in electr ic fields. The cases inves t iga ted nre, however , ve ry m u c h res t r ic ted (7.10) and a general form of such an evolu t ion operator , does not seem to h~ve been yet formlf la ted undeba tab ly (10). In the present art icle, we repor t the der iva t ion of a general form of the a fore-ment ioned evolu t ion operator. W e also show tha t the evolu t ion opera tor der ivcd by us, when ~pprox ima ted to first order in ex terna l field, yields Hous ton ' s wave funct ion. Fur the r , we show t h a t the equa l i ty of the ex te rna l field to the first-order t ime de r iva t ive of the k-vector , follows from qui te general considerat ions, ~ 'hen one makes use of the evolu t ion opera tor der ived in this art icle.

Electronic and Mössbauer spectroscopy studies of iron(II) complexes with tridentate unsaturated nitrogen containing ligands

The effect of the fusion of a further N-donor coordination site to a diimine giving tridentate unsaturat- ed chelate ligands in iron(II) complexes was investigated by using electronic and 57Fe Mössbauer spectroscopy. The electronic spectra, measured at 77 °K, showed that the tridentate ligands produce with iron(II) complexes, [Fe(ligand) 2] ++, having characteristic spectral features connected with the structure of the complex ion. The Mössbauer spectra taken at 295 and 4.2 °K, showed a variation of the isomer shift and quadrupole splitting In the series of complexes. The spectra taken with a external magnet- ic field showed for all complexes a negative sign for the principal component of the EFG tensor (V zz). The results are discussed the basis of a strong σ-bonding along a unique axis, considering the D 2d point group symmetry.

Effect of electric field strength on the rate of deposition and composition of electrophoretic chromium carbide alloy coatings

Elec t rophore t ic deposition is used as a means of applying wear res i s t an t coatings of hard alloys based on chromium carbide to steel par t s [1]. Now the rate of e lect rophoret ic deposition is known to depend strongly on the electrode voltage. However, in the coating of par ts of different s izes and geometr ic shapes it is also nec e s s a r y to allow for change in e lec t r ic field s t rength caused by t ransi t ion f rom one sys tem of electrodes to another.

Influence of the electric field on the combustion rate of a heterogeneous condensed system

At the p re sen t t ime t h e r e is cons iderab le in te res t in learn ing how to effect ively control the combust ion r a t e of a he terogeneous condensed s y s t e m (HCS). A method for regula t ing the combust ion r a t e of an HCS which has a quick r e s p o n s e t ime and is sufficiently s imple to implement ut i l izes the e lec t r ic field [1, 2]. However , any p rac t i ca l applicat ion of this method suf fe r s f r o m a lack of r e l i ab le informat ion concerning the na ture of the e lec t r i c field action on the combust ion p r o c e s s , the types of HCS bes t sui ted for this method, etc. These considera t ions lend g rea t impor tance to an exper imen ta l investigation of the influence of the e lec t r ic f ield on the combust ion r a t e of a condensed sys t em.

Magneto-electrophoretic separation of some inorganic ions

The term magneto-electrophoresis is used when the electrophoresis is carried out in a magnetic field. There are only few works published dealing mainly with organic substances. The present work is, however, on the separat ion o f inorganic ions by this technique. In this method, the usual electrophoretic mobili ty o f an ion is influenced by an external magnet ic field and separat ion o f the ions is sometimes made easier. In this paper, the change of electrophoretic migrat ion rates on paper o f a few inorganic ions as Fe 3 +, Cu 2 +, Fe(CN)~etc. are applied to improve the separation o f some binary mixtures a s Cu 2 + Fe 3 +, Fe 3 + Ni z +, Fe 3 + _ Co 2 +, Cu / + _ Cd z +, Co(NH3)63 + _ Ni(NH3) 2 + and Fe(CN) 4F e ( C N ) 3. It has been observed that the electrophoretic mobil i ty is retarded more when the ion is more paramagnet ic or the external magnetic field is made more intense.

Turbulence structure for a viscous conducting fluid in the presence of magnetic field

The most in te res t ing and p robab ly the least unde r s tood flow prob lem is the tu rbu len t flow. The essential cha rac te r i s t i c of t u rbu len t flow is t ha t the tu rbu len t f luc tuat ions are r a n d o m in nature , hence the final and logical so lu t ion of tu rbu lence p rob lem requires t he app l ica t ion of the m e t h o d of s ta t i s t ica l mechanics . At the present t i m e mos t of the resul ts f rom the s ta t i s t i ca l t heo ry of tu rbu lence are concerned wi th i so t ropic turbulence, which was first inves t iga ted by TAYLOR (1) and which was fu r the r developed by KiRM~N (2), KOLMOGOROFF (a), HEISENBERG (4) and others. In magne to -hydrodynamics the p rob lem is m u c h more compl ica ted because we have to consider b o t h the t u r b u l e n t f luctuat ions in t he magne t i c field as well as those in the ve loc i ty field and the i r i n t e rac t ion . I t was CHANDRASnKHAR (5) who ex tended the o rd inary s ta t i s t ica l t h e o r y of i so t rop ie tu rbu lence to the case of magne to -hydrodynamics . The in te rac t ion be tween a magne t i c field and t u r b u l e n t mot ion has f r equen t ly been s tudied in connec t ion wi th the possible existence of an in te rs te l la r magnet ic field. In a med ium of h igh e lect r ica l conduc t iv i ty , tu rbu lence wil l be accompanied by a spontaneous genera t ion and subsequent ampli f icat ion of a magne t i c field. BATCHELOR (6) discussed in deta i l the behaviour of a spontaneous magne t i c field in tu rbu len t flow wi thou t an ex te rna l magne t i c field. T~ODO~SON (7) had shown t h a t the equa t ion of fluid mot ion for a viscous and incompressible fluid can be wr i t t en in short and exac t fo rm w i t h the var iable to, t he v o r t i c i t y ; t he ra te of change of to 2 is shown to be composed of two parts , one pos i t ive and the o the r negat ive. He found the s t ruc tu re of t u rbu l ence to be horse-shoe. In the p resen t paper the au thor discuss the effect of t he magne t i c field over the s t ruc tu re of turbulence .