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The Near-Infrared Broad Emission Line Region of Active Galactic Nuclei. I. The Observations
We present high-quality (high signal-to-noise ratio and moderatespectral resolution) near-infrared (near-IR) spectroscopic observationsof 23 well-known broad emission line active galactic nuclei (AGNs). Inaddition, we obtained simultaneous (within 2 months) opticalspectroscopy of similar quality. The near-IR broad emission linespectrum of AGNs is dominated by permitted transitions of hydrogen,helium, oxygen, and calcium, and by the rich spectrum of singly ionizediron. In this paper we present the spectra, line identifications, andmeasurements, and we address briefly some of the important issuesregarding the physics of AGN broad emission line regions. In particular,we investigate the excitation mechanism of neutral oxygen and confrontfor the first time theoretical predictions of the near-IR iron emissionspectrum with observations.
| 3D mapping of the dense interstellar gas around the Local Bubble
We present intermediate results from a long-term program of mapping theneutral absorption characteristics of the local interstellar medium,motivated by the availability of accurate and consistent parallaxes fromthe Hipparcos satellite. Equivalent widths of the interstellar NaID-line doublet at 5890 Å are presented for the lines-of-sighttowards some 311 new target stars lying within ~ 350 pc of the Sun.Using these data, together with NaI absorption measurements towards afurther ~ 240 nearby targets published in the literature (for many ofthem, in the directions of molecular clouds), and the ~ 450lines-of-sight already presented by (Sfeir et al. \cite{sfeir99}), weshow 3D absorption maps of the local distribution of neutral gas towards1005 sight-lines with Hipparcos distances as viewed from a variety ofdifferent galactic projections.The data are synthesized by means of two complementary methods, (i) bymapping of iso-equivalent width contours, and (ii) by densitydistribution calculation from the inversion of column-densities, amethod devised by Vergely et al. (\cite{vergely01}). Our present dataconfirms the view that the local cavity is deficient in cold and neutralinterstellar gas. The closest dense and cold gas ``wall'', in the firstquadrant, is at ~ 55-60 pc. There are a few isolated clouds at closerdistance, if the detected absorption is not produced by circumstellarmaterial.The maps reveal narrow or wide ``interstellar tunnels'' which connectthe Local Bubble to surrounding cavities, as predicted by the model ofCox & Smith (1974). In particular, one of these tunnels, defined bystars at 300 to 600 pc from the Sun showing negligible sodiumabsorption, connects the well known CMa void (Gry et al. \cite{gry85}),which is part of the Local Bubble, with the supershell GSH 238+00+09(Heiles \cite{heiles98}). High latitude lines-of-sight with the smallestabsorption are found in two ``chimneys'', whose directions areperpendicular to the Gould belt plane. The maps show that the LocalBubble is ``squeezed'' by surrounding shells in a complicated patternand suggest that its pressure is smaller than in those expandingregions.We discuss the locations of several HI and molecular clouds. Usingcomparisons between NaI and HI or CO velocities, in some cases we areable to improve the constraints on their distances. According to thevelocity criteria, MBM 33-37, MBM 16-18, UT 3-7, and MBM 54-55 arecloser than ~ 100 pc, and MBM 40 is closer than 80 pc. Dense HI cloudsare seen at less than 90 pc and 85 pc in the directions of the MBM 12and MBM 41-43 clouds respectively, but the molecular clouds themselvesmay be far beyond. The above closest molecular clouds are located at theneutral boundary of the Bubble. Only one translucent cloud, G192-67, isclearly embedded within the LB and well isolated.These maps of the distribution of local neutral interstellar NaI gas arealso briefly compared with the distribution of both interstellar dustand neutral HI gas within 300 pc.Tables 1 and 2 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp:cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/411/447
| High-resolution observations of interstellar NaI and CaII towards the southern opening of the `Local Interstellar Chimney': probing the disc-halo connection
We present high-resolution (R= 400 000) observations of interstellarCaII and NaI absorption lines towards seven stars in the direction ofthe southern opening of the recently identified Local InterstellarChimney. These lines of sight probe the lower Galactic halo (0.3<~|z|<~ 2.5 kpc), without the complication of sampling denseforeground interstellar material. In addition to components withvelocities expected from Galactic rotation, these stars also exhibitcomponents with negative local standard of rest velocities, which arecontrary to the sense of Galactic rotation for the sightlines observed.After a discussion of possible origins for these peculiar velocities, weconclude that at least some of them result from gas falling towards theGalactic plane from distances of |z|>~ 300 pc. The narrow linewidthsare generally inconsistent with temperatures as high as the ~6000 Kgenerally assumed for the so-called Lockman layer. Rather, the picturethat emerges is one of a scattered, generally infalling, population ofhigh-|z| diffuse clouds, seemingly not very different from thoseencountered in the local interstellar medium. Overall, we argue that ourresults are most consistent with a `Galactic fountain' model.
| Multiwavelength Observation of a New Black Hole Candidate: EXS 1737.9-2952
We report a multiwavelength analysis of an unusual high-energytransient: EXS 1737.9-2952. Due to the features this source exhibited inthe hard X-ray domain similar to another source in the Galactic centerregion (1E1740.9 - 2952), and in order to study the molecular gas towardthis X-ray source, we performed an observation of the EXS region in 1993August, using the Swedish-ESO Submillimeter Telescope (SEST) located inLa Silla (Chilean Andes). We observed a cloud, at the ``forbidden''velocity of 135 km s^-1, using ^12CO (1-0) transitions, giving a maximumcolumn density of 8 x 10^21 cm^-2. In 1994 we conducted otherobservations to search for higher density regions inside the cloud,using HCO+ and CS lines, but they were unsuccessful: we concluded thatthe cloud could be associated with the X-ray source and its mean densityis of the order of ~10^3 cm^-3. In 1994 April, we performed a set ofobservations of the field containing EXS, at 20 cm and 6 cm, using theVLA in its A configuration, and found four possible radio candidates foran association with the EXS X-ray source, one of them (source 3) beingextended, exhibiting a head-tail morphology, and a having a thermalspectrum with a spectral index ~ -0.7. We reproduced our observation in1994 November and December, using the C configuration at 6 cm, in orderto investigate on possible variability and extension of these sourcesand found a marginal indication in the 20 cm image that source 3 mayhave a weak second component displaced about 15". Nevertheless, thisindication is too faint to associate this source definitely with EXSsince no significant variation was detected. In addition, during the1994 November-December observation, two more extended sources weredetected but their association with EXS is unlikely. We also analyzedthe Einstein/IPC image of the 5 sigma EXS error box which does notexhibit, at the time of the observation, any significant low-energyX-ray counterpart to EXS. A nearby pulsar PSR 1737-30 in the ROSATcatalog is outside this error box. Finally, IRAS maps of the EXS regiondo not show any IR contribution at the location of the radio sources. Weconclude that (1) EXS 1737.9-2952 is a high-energy transient, (2) apersistent counterpart at other wavelengths is not demonstrated, and (3)EXS, when flaring, as well as other GC gamma-ray sources, could possiblycontribute to the 511 keV bulge emission.
| Faint blue stars in the region near the South Galactic Pole.
Not Available
| Six-color photometry of stars. VIII. The colors of 409 stars of different spectral types
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1956ApJ...123..440S&db_key=AST
| Sur la détermination de la grandeur de la discontinuité de Balmer par les méthodes de la photométrie à travers des filtres
Not Available
| Untersuchungen an Farbenindizes I. Mit 3 Textabbildungen
Not Available
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Besorolás csoportokba:
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Pozíciós és asztrometriai adatok
| Csillagkép: | Sas |
| Rektaszcenzió: | 23h19m02.15s |
| Deklináció: | -12°10'13.5" |
| Vizuális fényesség: | 7.229 |
| Távolság: | 523.56 parszek |
| RA sajátmozgás: | 10.1 |
| Dec sajátmozgás: | -0.8 |
| B-T magnitude: | 7.22 |
| V-T magnitude: | 7.229 |
Katalógusok és elnevezések:
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