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Contribution to the search for binaries among Am stars - VIII. New spectroscopic orbits of eight systems and statistical study of a sample of 91 Am stars
This paper is the last of a series devoted to the study of Am stars,with the monitoring of radial velocities of a sample of 91 objectsduring more than 20 yr. The purpose was to determine which stars weremembers of spectroscopic binaries (SBs) and study in detail thosesystems in order to obtain observational constraints on the origin ofthe Am phenomenon.In the first part, we present the results of a detailed study of eightAm stars (HD 32893, 60489, 109762, 111057, 113697, 204918, 219675 andBD+44° 4512) observed at the Haute-Provence and Cambridgeobservatories with CORAVEL instruments. We find that these objects aresingle-lined SBs whose orbital elements are determined for the firsttime. HD 32893 is found to be a triple spectroscopic system whose thirdbody might be detected by speckle interferometry. Physical parametersare inferred for the primaries of those SBs. We then investigate theinfluence of tidal interaction and find that it has already led to thesynchronism of the primaries and to the circularization of the orbits offour of those systems.In the second part of this paper, we present the main results of ourwhole programme and derive some statistical properties of Am stars. Wegive the recapitulating table of the orbital parameters found for theSBs of our whole sample and the list of those for which no evidence forradial velocity variations could be found during our monitoring. Ourstudy shows that at least 64 per cent of Am stars are members of SBs.This rate is significantly greater than that of normal stars. Althoughsome SBs may have been not detected, this study shows that a substantialfraction of Am stars do not belong to SBs: they are either isolatedstars or members of wide binary systems.We then present some statistical properties of the orbital parameters ofthe SBs whose primary is an Am star, on an extended sample obtained byadding 29 Am SB orbits published by other authors. The corresponding eversus logP diagram shows a cut-off between the circular and theeccentric systems at P ~ 5.6 +/- 0.5 d, which indicates a typical age of0.5 - 1 × 109 yr for the Am stars, which is inagreement with the values found in our previous detailed studies. AMonte Carlo analysis shows that the distribution of the mass functionvalues f(m) is compatible with a power-law distribution N(m) ~m-α of the masses m of the companions with α =0.3 +/- 0.2 or with a Gaussian distribution centred on 0.8 +/-0.5Msolar, which indicates that the companions of Am SBs aremostly dwarf stars of type G-K-M.
| Effective temperature scale and bolometric corrections from 2MASS photometry
We present a method to determine effective temperatures, angularsemi-diameters and bolometric corrections for population I and II FGKtype stars based on V and 2MASS IR photometry. Accurate calibration isaccomplished by using a sample of solar analogues, whose averagetemperature is assumed to be equal to the solar effective temperature of5777 K. By taking into account all possible sources of error we estimateassociated uncertainties to better than 1% in effective temperature andin the range 1.0-2.5% in angular semi-diameter for unreddened stars.Comparison of our new temperatures with other determinations extractedfrom the literature indicates, in general, remarkably good agreement.These results suggest that the effective temperaure scale of FGK starsis currently established with an accuracy better than 0.5%-1%. Theapplication of the method to a sample of 10 999 dwarfs in the Hipparcoscatalogue allows us to define temperature and bolometric correction (Kband) calibrations as a function of (V-K), [m/H] and log g. Bolometriccorrections in the V and K bands as a function of T_eff, [m/H] and log gare also given. We provide effective temperatures, angularsemi-diameters, radii and bolometric corrections in the V and K bandsfor the 10 999 FGK stars in our sample with the correspondinguncertainties.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| Calibration of the Infrared Telescope Facility National Science Foundation Camera Jupiter Galileo Data Set
The NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii, setaside some time on about 500 nights from 1995 to 2002, when the NSFCAMfacility infrared camera was mounted and Jupiter was visible, for astandardized set of observations of Jupiter in support of the Galileomission. The program included observations of Jupiter, nearby referencestars, and dome flats in five filters: narrowband filters centered at1.58, 2.28, and 3.53 μm, and broader L' and M' bands that probe theatmosphere from the stratosphere to below the main cloud layer. Thereference stars were not cross-calibrated against standards. Weperformed follow-up observations to calibrate these stars and Jupiter in2003 and 2004. We present a summary of the calibration of the Galileosupport monitoring program data set. We present calibrated magnitudes ofthe six most frequently observed stars, calibrated reflectivities, andbrightness temperatures of Jupiter from 1995 to 2004, and a simplemethod of normalizing the Jovian brightness to the 2004 results. Ourstudy indicates that the NSFCAM's zero-point magnitudes were not stablefrom 1995 to early 1997, and that the best Jovian calibration possiblewith this data set is limited to about +/-10%. The raw images andcalibration data have been deposited in the Planetary Data System.
| The Pul-3 catalogue of 58483 stars in the Tycho-2 system
A catalogue of positions and proper motions of 58483 stars (Pul-3) hasbeen constructed at the Pulkovo observatory. The Pul-3 is based on theresults of measurements of photographic plates with galaxies (Deutsch'splan). All plates were taken using the Pulkovo Normal Astrograph (thefirst epoch is in the 1950s and the second epoch is in the 1970s).The Pul-3 catalogue contains stars of mainly 12 to 16.5 mag in 146fields with galaxies in the declination zone from -5o to+85o. The Tycho-2 has been used as a reference catalogue.The mean epoch of the Pul-3 is 1963.25. The internal positional accuracyof the Pul-3 catalogue at the mean epoch of observations is ±80mas. The accuracy of the proper motions is mostly within ±3mas/yr to ±12 mas/yr. Comparisons of the Pul-3 with Tycho-2 andARIHIP have been done at the mean epoch of the Pul-3. The Pul-3 externalpositional accuracy relative to Tycho-2 is ±150 mas.The catalogue is 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/418/357
| Empirically Constrained Color-Temperature Relations. II. uvby
A new grid of theoretical color indices for the Strömgren uvbyphotometric system has been derived from MARCS model atmospheres and SSGsynthetic spectra for cool dwarf and giant stars having-3.0<=[Fe/H]<=+0.5 and 3000<=Teff<=8000 K. Atwarmer temperatures (i.e., 8000-2.0. To overcome thisproblem, the theoretical indices at intermediate and high metallicitieshave been corrected using a set of color calibrations based on fieldstars having well-determined distances from Hipparcos, accurateTeff estimates from the infrared flux method, andspectroscopic [Fe/H] values. In contrast with Paper I, star clustersplayed only a minor role in this analysis in that they provided asupplementary constraint on the color corrections for cool dwarf starswith Teff<=5500 K. They were mainly used to test thecolor-Teff relations and, encouragingly, isochrones thatemploy the transformations derived in this study are able to reproducethe observed CMDs (involving u-v, v-b, and b-y colors) for a number ofopen and globular clusters (including M67, the Hyades, and 47 Tuc)rather well. Moreover, our interpretations of such data are verysimilar, if not identical, with those given in Paper I from aconsideration of BV(RI)C observations for the sameclusters-which provides a compelling argument in support of thecolor-Teff relations that are reported in both studies. Inthe present investigation, we have also analyzed the observedStrömgren photometry for the classic Population II subdwarfs,compared our ``final'' (b-y)-Teff relationship with thosederived empirically in a number of recent studies and examined in somedetail the dependence of the m1 index on [Fe/H].Based, in part, on observations made with the Nordic Optical Telescope,operated jointly on the island of La Palma by Denmark, Finland, Iceland,Norway, and Sweden, in the Spanish Observatorio del Roque de losMuchachos of the Instituto de Astrofisica de Canarias.Based, in part, on observations obtained with the Danish 1.54 mtelescope at the European Southern Observatory, La Silla, Chile.
| L' and M' standard stars for the Mauna Kea Observatories Near-Infrared system
We present L' and M' photometry, obtained at the United Kingdom InfraredTelescope (UKIRT) using the Mauna Kea Observatories Near-Infrared(MKO-NIR) filter set, for 46 and 31 standard stars, respectively. The L'standards include 25 from the in-house `UKIRT Bright Standards' withmagnitudes deriving from Elias et al. and observations at the InfraredTelescope Facility in the early 1980s, and 21 fainter stars. The M'magnitudes derive from the results of Sinton and Tittemore. We estimatethe average external error to be 0.015 mag for the bright L' standardsand 0.025 mag for the fainter L' standards, and 0.026 mag for the M'standards. The new results provide a network of homogeneously observedstandards, and establish reference stars for the MKO system, in thesebands. They also extend the available standards to magnitudes whichshould be faint enough to be accessible for observations with moderndetectors on large and very large telescopes.
| Fe II/Mg II Emission-Line Ratio in High-Redshift Quasars
We present results of the analysis of near-infrared spectroscopicobservations of six high-redshift quasars (z>~4), emphasizing themeasurement of the ultraviolet Fe II/Mg II emission-line strength toestimate the beginning of intense star formation in the early universe.To investigate the evolution of the Fe II/Mg II ratio over a wider rangein cosmic time, we measured this ratio for composite quasar spectra thatcover a redshift range 0<~z<~5 with nearly constant luminosity, aswell as for those that span ~6 orders of magnitude in luminosity. Adetailed comparison of the high-redshift quasar spectra with those oflow-redshift quasars with comparable luminosity shows essentially thesame Fe II/Mg II emission ratios and very similar continuum and linespectral properties, i.e., a lack of evolution of the relativeiron-to-magnesium abundance of the gas in bright quasars since z~=5.Current nucleosynthesis and stellar evolution models predict thatα-elements such as magnesium are produced in massive stars endingin Type II supernovae, while iron is formed predominantly in Type Iasupernovae with intermediate-mass progenitors. This results in an ironenrichment delay of ~0.2-0.6 Gyr. We conclude that intense starformation activity in the host galaxies of z>~4 quasars must havestarted already at an epoch corresponding to zf~=6-9, whenthe age of the universe was ~0.5 Gyr (H0=72 km s-1Mpc-1, ΩM=0.3,ΩΛ=0.7). This epoch corresponds well to thereionization era of the universe.Based on observations collected at the Cerro Tololo Inter-AmericanObservatory, Chile, at the European Southern Observatory, Paranal,Chile, and the W. M. Keck Observatory, Hawaii.
| High-Precision Near-Infrared Photometry of a Large Sample of Bright Stars Visible from the Northern Hemisphere
We present the results of 8 yr of infrared photometric monitoring of alarge sample of stars visible from Teide Observatory (Tenerife, CanaryIslands). The final archive is made up of 10,949 photometric measuresthrough a standard InSb single-channel photometer system, principally inJHK, although some stars have measures in L'. The core of this list ofstars is the standard-star list developed for the Carlos SánchezTelescope. A total of 298 stars have been observed on at least twooccasions on a system carefully linked to the zero point defined byVega. We present high-precision photometry for these stars. The medianuncertainty in magnitude for stars with a minimum of four observationsand thus reliable statistics ranges from 0.0038 mag in J to 0.0033 magin K. Many of these stars are faint enough to be observable with arraydetectors (42 are K>8) and thus to permit a linkage of the bright andfaint infrared photometric systems. We also present photometry of anadditional 25 stars for which the original measures are no longeravailable, plus photometry in L' and/or M of 36 stars from the mainlist. We calculate the mean infrared colors of main-sequence stars fromA0 V to K5 V and show that the locus of the H-K color is linearlycorrelated with J-H. The rms dispersion in the correlation between J-Hand H-K is 0.0073 mag. We use the relationship to interpolate colors forall subclasses from A0 V to K5 V. We find that K and M main-sequence andgiant stars can be separated on the color-color diagram withhigh-precision near-infrared photometry and thus that photometry canallow us to identify potential mistakes in luminosity classclassification.
| The origin of [FeII] emission in NGC4151
The centre of NGC4151 has been observed in the J band with the SMIRFSintegral field unit (IFU) on the UK Infrared Telescope. A map of [FeII]emission is derived, and compared with the distributions of the opticalnarrow-line region and radio jet. We conclude that, because the [FeII]emission is associated more closely with the visible narrow-line regionthan with the radio jet, it arises mainly through photoionization of gasby collimated X-rays from the Seyfert nucleus. The velocity field andstrength with respect to Paβ are found to be consistent with thisargument. The performance of the IFU is considered briefly, andtechniques for observation and data analysis are discussed.
| A Multi-Band Photometric Study of Tidal Debris in a Compact Group of Galaxies: Seyfert's Sextet
In order to investigate the properties of the prominent tidal debrisfeature extending to the northeast of a compact group of galaxies,Seyfert's Sextet, we analyzed multi-band (U, B, V, VR, R, I, J, H, andK') photometric imaging data and obtained the following results: 1) Theradial surface brightness distribution of this tidal debris in Seyfert'sSextet (TDSS) in each band appears to be well approximated by anexponential profile. 2) The observed B-V color of TDSS is similar tothose of dwarf elliptical galaxies in nearby clusters. 3) Comparing thespectral energy distribution (SED) of TDSS with theoretical photometricevolution models and with the SED of the stars in the outer part of HCG79b, we find that its SED is comparable to that of a ~10Gyr-old stellarpopulation with solar metallicity, similar to the stellar population inthe outer part of HCG 79b. This suggests that TDSS consists of starsthat may have been liberated from HCG 79b by strong ga laxyinteractions, not a pre-existing dwarf galaxy as previously thought.
| 5 Micron Photometry of Late-Type Dwarfs
We present narrowband M photometry of nine low-mass dwarfs with spectraltypes ranging from M2.5 to L0.5. Combining the (L'-M') colors derivedfrom our observations with data from the literature, we find colorsconsistent with a Rayleigh-Jeans flux distribution for spectral typesearlier than M5, but enhanced F3.8/F4.7 fluxratios (negative [L'-M'] colors) at later spectral types. This probablyreflects increased absorption at M' due to the CO fundamental band. Wecompare our results against recent model predictions and briefly discussthe implications.
| Optical and infrared spectroscopy of the type IIn SN 1998S: days 3-127
We present contemporary optical and infrared spectroscopic observationsof the type IIn SN 1998S covering the period between 3 and 127 daysafter discovery. During the first week the spectra are characterized byprominent broad H, He and Ciii/Niii emission lines with narrow peaks,superimposed on a very blue continuum (T~24000K). In the following twoweeks the Ciii/Niii emission vanished, together with the broad emissioncomponents of the H and He lines. Broad, blueshifted absorptioncomponents appeared in the spectra. The temperature of the continuumalso dropped to ~14000K. By the end of the first month the spectrumcomprised broad, blueshifted absorptions in H, He, Siii, Feii and Scii.By day 44, broad emission components in H and He reappeared in thespectra. These persisted to as late as days ~100-130, becomingincreasingly asymmetric. We agree with Leonard et al. that the broademission lines indicate interaction between the ejecta and circumstellarmaterial (CSM) emitted by the progenitor. We also agree that theprogenitor of SN 1998S appears to have gone through at least two phasesof mass-loss, giving rise to two CSM zones. Examination of the spectraindicates that the inner zone extended to <=90au, while the outer CSMextended from 185au to over 1800au. We also present high-resolutionspectra obtained at days 17 and 36. These spectra exhibit narrow P CygniHi and Hei lines superimposed on shallower, broader absorptioncomponents. Narrow lines of [Nii], [Oiii], [Neiii] and [Feiii] are alsoseen. We attribute the narrow lines to recombination and heatingfollowing ionization of the outer CSM shell by the UV/X-ray flash atshock breakout. Using these lines, we show that the outer CSM had avelocity of 40-50kms-1. Assuming a constant velocity, we caninfer that the outer CSM wind commenced more than 170 years ago, andceased about 20 years ago, while the inner CSM wind may have commencedless than 9 years ago. During the era of the outer CSM wind the outflowfrom the progenitor was high - at least~2×10-5Msolaryr-1. Thiscorresponds to a mass-loss of at least ~0.003Msolar,suggesting a massive progenitor. The shallower, broader absorption is ofwidth ~350kms-1, and may have arisen from a component of theouter CSM shell produced when the progenitor was going through a laterblue supergiant phase. Alternatively, it may have been produced by theacceleration of the outer CSM by the radiation pressure of the UVprecursor. We also describe and model first-overtone emission in carbonmonoxide observed in SN 1998S. We deduce a CO mass of~10-3Msolar moving at ~2200kms-1, andinfer a mixed metal/He core of about 4Msolar, againindicating a massive progenitor. Only three core-collapse supernovaehave been observed in the K band at post-100 days, and all three haveexhibited emission from CO.
| Infrared L-Band Observations of the Trapezium Cluster: A Census of Circumstellar Disks and Candidate Protostars
We report the results of a sensitive near-infrared JHKL imaging surveyof the Trapezium cluster in Orion. We use the JHKL colors to obtain acensus of infrared excess stars in the cluster. Of (391) stars brighterthan 12th magnitude in the K and L bands, 80%+/-7% are found to exhibitdetectable infrared excess on the J-H, K-L color-color diagram.Examination of a subsample of 285 of these stars with published spectraltypes yields a slightly higher infrared excess fraction of 85%. We findthat 97% of the optical proplyds in the cluster exhibit excess in theJHKL color-color diagram indicating that the most likely origin of theobserved infrared excesses is from circumstellar disks. We interpretthese results to indicate that the fraction of stars in the cluster withcircumstellar disks is between 80%-85%, confirming earlier publishedsuggestions of a high disk fraction for this young cluster. Moreover, wefind that the probability of finding an infrared excess around a star isindependent of stellar mass over essentially the entire range of thestellar mass function down to the hydrogen burning limit. Consequently,the vast majority of stars in the Trapezium cluster appear to have beenborn with circumstellar disks and the potential to subsequently formplanetary systems, despite formation within the environment of a richand dense stellar cluster. We identify 78 stars in our samplecharacterized by K-L colors suggestive of deeply embedded objects. Thespatial distribution of these objects differs from that of the rest ofthe cluster members and is similar to that of the dense molecular cloudridge behind the cluster. About half of these objects are detected inthe short wavelength (J and H) bands, and these are found to becharacterized by extreme infrared excess. This suggests that many ofthese sources could be protostellar in nature. If even a modest fraction(i.e., ~50%) of these objects are protostars, then star formation couldbe continuing in the molecular ridge at a rate comparable to that whichproduced the foreground Trapezium cluster.
| Optical and infrared photometry of the Type IIn SN 1998S: days 11-146
We present contemporaneous optical and infrared (IR) photometricobservations of the Type IIn SN 1998S covering the period between 11 and146d after discovery. The IR data constitute the first ever IR lightcurves of a Type IIn supernova. We use blackbody and spline fits to thephotometry to examine the luminosity evolution. During the first 2-3months, the luminosity is dominated by the release of shock-depositedenergy in the ejecta. After ~100d the luminosity is powered mostly bythe deposition of radioactive decay energy from0.15+/-0.05Msolar of 56Ni which was produced inthe explosion. We also report the discovery of an astonishingly high IRexcess, K-L'=2.5, that was present at day 130. We interpret this asbeing due to thermal emission from dust grains in the vicinity of thesupernova. We argue that to produce such a high IR luminosity so soonafter the explosion, the dust must be pre-existing and so is located inthe circumstellar medium of the progenitor. The dust could be heatedeither by the UV/optical flash (IR echo) or by the X-rays from theinteraction of the ejecta with the circumstellar material.
| The Visual Orbit and Evolutionary State of 12 Bootis
We report on the determination of the visual orbit of the double-linedspectroscopic binary system 12 Bootis with data obtained by the PalomarTestbed Interferometer in 1998 and 1999. 12 Boo is a nearly equal-massdouble-lined binary system whose spectroscopic orbit is well known. Wehave estimated the visual orbit of 12 Boo from our interferometricvisibility data fitted both separately and in conjunction with archivaland CORAVEL radial velocity data. Our 12 Boo orbit is in good agreementwith the spectroscopic results, and the physical parameters implied by acombined fit to our visibility data and radial velocity data result inprecise component masses. In particular, the orbital parallax of thesystem is determined to be 27.09+/-0.41 mas, and masses of the twocomponents are determined to be 1.435+/-0.023 Msolar and1.409+/-0.020 Msolar, respectively. Somewhat remarkably, eventhough the two components are nearly equal mass, the system exhibits asignificant brightness difference between the components in thenear-infrared and visible. We attribute this brightness difference toevolutionary differences between the two components in their transitionbetween main-sequence and giant evolutionary phases, and based ontheoretical isochrones we can estimate a system age. Further, becausethe atmospheres of the two components are becoming more convective, wesuggest the system components are currently at or near synchronousrotation, and the system orbit is in the process of circularizing.
| Shock Excitation in Interacting Galaxies: Markarian 266
We present near-infrared data on the luminous interacting system Mrk 266(NGC 5256), comprising 2 μm continuum, and Brγ and 1-0 S(1)emission-line images, together with K-band spectra. We have fittedstellar templates to the continuum, allowing us to account for all thestellar features and hence detect even faint gas excitation emissionlines, including eight and 11 H2 lines in the southwest andnortheast nuclei, respectively. Population diagrams for the excitedH2 molecules indicate that most of the 1-0 S(1) in each ofthe nuclei has a thermal origin. We discuss this with reference to theobserved morphologies, especially that of the 1-0 S(1) line. Inparticular, the core of 1-0 S(1) in the northeast nucleus is morecompact than the 2 μm continuum, while in the southwest nucleus the1-0 S(1) is significantly offset by 500 pc from the continuum (andother) emission. Last, we address the issue of the region midway betweenthe two nuclei, where previously a strong source of radio continuum hasbeen observed. These results are set in the context of interactinggalaxies where shock-excited emission might be expected to occur as adirect consequence of the interaction.
| Sixth Catalogue of Fundamental Stars (FK6). Part III. Additional fundamental stars with direct solutions
The FK6 is a suitable combination of the results of the HIPPARCOSastrometry satellite with ground-based data, measured over a longinterval of time and summarized mainly in the FK5. Part III of the FK6(abbreviated FK6(III)) contains additional fundamental stars with directsolutions. Such direct solutions are appropriate for single stars or forobjects which can be treated like single stars. Part III of the FK6contains in total 3272 stars. Their ground-based data stem from thebright extension of the FK5 (735 stars), from the catalogue of remainingSup stars (RSup, 732 stars), and from the faint extension of the FK5(1805 stars). From the 3272 stars in Part III, we have selected 1928objects as "astrometrically excellent stars", since their instantaneousproper motions and their mean (time-averaged) ones do not differsignificantly. Hence most of the astrometrically excellent stars arewell-behaving "single-star candidates" with good astrometric data. Thesestars are most suited for high-precision astrometry. On the other hand,354 of the stars in Part III are Δμ binaries in the sense ofWielen et al. (1999). Many of them are newly discovered probablebinaries with no other hitherto known indication of binarity. The FK6gives, besides the classical "single-star mode" solutions (SI mode),other solutions which take into account the fact that hidden astrometricbinaries among "apparently single-stars" introduce sizable "cosmicerrors" into the quasi-instantaneously measured HIPPARCOS proper motionsand positions. The FK6 gives, in addition to the SI mode, the "long-termprediction (LTP) mode" and the "short-term prediction (STP) mode". TheseLTP and STP modes are on average the most precise solutions forapparently single stars, depending on the epoch difference with respectto the HIPPARCOS epoch of about 1991. The typical mean error of anFK6(III) proper motion in the single-star mode is 0.59 mas/year. This isa factor of 1.34 better than the typical HIPPARCOS errors for thesestars of 0.79 mas/year. In the long-term prediction mode, in whichcosmic errors are taken into account, the FK6(III) proper motions have atypical mean error of 0.93 mas/year, which is by a factor of about 2better than the corresponding error for the HIPPARCOS values of 1.83mas/year (cosmic errors included).
| Do galaxy mergers form elliptical galaxies? A comparison of kinematic and photometric properties
We present near-infrared K-band imaging and spectroscopy of a sample ofgalaxy mergers, which we use to derive light profile indices, absolutemagnitudes and central velocity dispersions. We find that the lightdistributions of mergers more nearly resemble those of ellipticals thanthose of bulges, but that the mergers lie well away from the FundamentalPlane defined by the ellipticals. We interpret this as being due toenhancement of the K-band surface brightness of the mergers by asignificant population of supergiant stars, and independent evidence forsuch a population is inferred from measurements of the depth of the2.3-μm CO absorption feature.
| Possible Young Stellar Objects without Detectable CO Emission
Young stellar objects (YSOs) usually appear in molecular clouds asinfrared objects associated with a molecular envelope. Wouterloot andBrand (1989, AAA 50.133.012) searched 1302 IRAS point sources withreliable fluxes at 25, 60, and 100 mu m near to the galactic plane for12CO (J=1-0) emission; 1077 sources were detected. Amongtheir far-infrared sources without detectable CO emission, we found thatat least 18 objects are invisible at optical and near-infraredwavelengths. The infrared spectral indices between 2.2 mu m and 25 mu mcorrespond to those of class I YSOs, and the IRAS colors are similar tothose of the usual YSOs. These peculiar far-infrared objects are highlyconcentrated around the galactic plane and the distances are estimatedto be ~ 1 kpc. Although their distribution is away from molecularclouds, some of them seem to be associated with large dark clouds orweak radio sources. These objects are possible YSOs with low COabundance in the envelopes.
| Excited molecular hydrogen around the Seyfert nuclei of NGC 3227 and 4151
High-resolution images of the nuclear regions of the Seyfert galaxiesNGC 3227 and 4151 have been obtained in the H_2 1-0 S(1) emission line(rest lambda = 2.1218 mu m) with the IRCAM3 camera on the 3.8-m UKIRTtelescope. A 2" elongation of the photoexcited H_2 is observed in NGC3227 that is coincident with the optical nucleus. Combined with otherobservations, this indicates the presence of a molecular discsurrounding the active nucleus with the interior being photoexcited. A 2x 2.5 arcsec^2 ring of excited H_2 centred on the nucleus is partiallyobserved in NGC 4151. This is believed to be part of a circumnucleartorus that contains ionized, atomic and molecular gas in an onion-skinstructure.
| IRAS F10214+4724: the inner 100pc
We use new high-resolution near-infrared spectroscopy and our previouslypublished optical spectroscopy of the gravitationally lensed Seyfert 2galaxy F10214+4724 to study both the links between the starburst and AGNin this object and the properties of the line-emitting clouds in theinner narrow-line region. Close inspection of the rest frame UV spectrumreveals interstellar or stellar absorption features consistent with acompact, moderately reddened starburst providing about half the UVlight, and explaining the dilution of the UV continuum polarizationrelative to the broad emission lines. Spectroscopy of the Hα/[Nii]line blend has enabled us to assess the relative contributions of theemission from the narrow-line region of the Seyfert 2, and a moderatelyreddened emission-line region which we argue is associated with thestarburst activity. Estimates of the star formation rate from theunpolarized UV continuum flux and the Hα flux are consistent towithin their associated uncertainties. We find we can plausibly explainthe unusual emission-line properties of F10214+4724 in terms ofconventional models for nearby Seyfert 2 galaxies if lensing ispreferentially magnifying the side of the inner narrow-line regionbetween the AGN and the observer, and the other side is both lessmagnified and partially obscured by the torus. The hydrogen densities ofclouds in this region are high enough to make the Balmer lines opticallythick and to suppress forbidden emission lines with low criticaldensities. From the emission-line spectrum we have deduced the columndensity of both ionized and neutral gas in the narrow-line clouds, andthe density of the ionized gas. Using these we have been able toestimate the mass of the inner narrow-line clouds to be ~1M, and showthat the gas:dust ratio N_H/E(B-V) in these clouds must be~1.3x10^27m^-2mag^-1, significantly higher than the average value in theMilky Way, ~4.5x10^25m^-2mag^-1. The column density and low dust contentof a typical cloud are consistent with the properties of the warmabsorbers seen in the X-ray spectra of Seyfert 1 galaxies. Our resultsthus favour models in which the narrow-line clouds start life close tothe nucleus and flow out. An emission line from the lensing system hasallowed us to confirm its redshift as z~0.9.
| Characteristics of the 2MASS Prototype Survey
The 2 Micron All Sky Survey (2MASS) will catalog over 100,000,000individual objects, the vast majority of which will be stars of spectraltype K and later. For many projects it will be important to developtechniques to identify interesting objects within this data set. Thecombination of near-IR and visible light observations will be a powerfultool for finding objects from brown dwarfs to dust-enshrouded quasars.This paper describes prototype hardware and software systems used aspart of the preparation for the 2MASS survey. Three years ofobservations with prototype systems have produced a database of morethan 1 million objects. A companion paper describes the comparison ofthese data with optical plate material and visible spectroscopicobservations resulting in the discovery of a quasar with a redshift of0.147.
| A disc of shocked molecular hydrogen around the active nucleus of NGC 3079
A high-resolution image of the nuclear regions of the active galaxy NGC3079 has been obtained in the H_2 1-0 S(1) emission line (rest lambda =2.1218 μm) with the IRCAM3 camera on the 3.8-m UKIRT telescope. An ~35 pc diameter elongated core within a more diffuse, 300 pc long, regionof most likely shock-excited H_2 is shown to surround the active nucleusand be embedded within what could be an extended region of enhanced starformation. A disc of molecular gas could be present that shapes theemission of relativistic gas away from the plane of the galaxy. Thisnuclear H_2 1-0 S(1) emitting gas (of total mass ~ 10^3 M_solar) iswithin a central dip in the distribution of cool, CO emitting, moleculargas (of total mass ~ 10^10 M_solar) which extends much further from thenucleus. The distributions of both the hot and the cool molecular gasesare likely to be clumpy.
| Delta a and Stroemgren photometry of stars in the Renson-catalogue of AP and AM stars
We have observed 131 stars of \cite[Renson's (1991)]{re91} catalogue ofAp and Am stars both in the Stroemgren & Maitzen's (1976) Delta asystem as a contribution to the photometric studies of the lambda 5200broad band flux depression feature in chemically peculiar stars. Withfew exceptions the probability grouping of Renson for membership in theCP2 group of peculiar stars is nicely reflected by peculiar values ofDelta a. Comparison with already available Delta a values yieldsslightly larger values due to a minor shift in the filter g_1 samplingthe depression. As found by \cite[Maitzen & Vogt (1983)]{ma83} theGeneva system peculiarity parameters correlate well with Delta a. Thisstudy demonstrates the advantageous performance of a photoelectricphotometer with a rapidly rotating filter wheel moving in a stop and gomode. Tables 3 and 4 are also available in electronic form at the CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| The near-infrared extinction law and limits on the pre-main-sequence population of the Rho Ophiuchi dark cloud
We describe new techniques to measure the NIR extinction law and toplace limits on the premain-sequence stellar population of a dark cloud.We analyze JHK imaging data for the central 1 sq deg of the Rho Ophiuchicloud core and show that nearly all stars projected onto regions of lowCS intensity, ICS 10 K km/s, are background stars. Most sources atlarger CS intensities lie within cloud material. We use the backgroundstars to derive the slope of the NIR extinction law, E(J-H)/E(H-K) =1.57 +/- 0.03. This result is consistent with previous extinction lawsbut has a factor of two to three smaller uncertainty. The new Rho Ophextinction law yields strong constraints on the number of previouslyundiscovered premain-sequence stars in the cloud, 46 +/- 11, and thenumber of previously undiscovered young stars with near-IR excesses, 15+/- 4. Neither limit exceeds the number of known premain-sequence starsin the cloud about 100. Thus, current samples of premain-sequence starsare reasonably complete for K = 14 or less.
| GPM - compiled catalogue of absolute proper motions of stars in selected areas of sky with galaxies.
Not Available
| The empirical scale of temperatures of the low main sequence (F0V-K5V).
We have calibrated the effective temperatures of the low main sequencestars ranging spectral types from F0 to K5 versus [Fe/H] and colours(B-V), (R-I), (V-R), (V-I), (V-K), (J-H), (J-K) and ubvy-β, using alarge sample of dwarfs and subdwarfs. The effective temperatures, scaledto direct T_eff_ determinations via reliable angular diametermeasurements, were derived applying the InfraRed Flux Method with thenew grid of atmosphere models developed by Kurucz (1993). We have fittedpolynomial functions of the form θ_eff_=P(colour,[Fe/H]) usingthe least squares method. The precision of the fits ranges from 30K for(V-K) to 154K for (J-H). The new relations have been compared toprevious calibrations. We also provide the empirical intrinsic colours(U-B), (B-V), (R-I), (V-R), (V-I), (V-K), (J-H), (J-K) and β, inthe ranges: 4000K[Fe/H]>-2.5.
| Starburst Galaxies. II. Imaging and Spectroscopy of a Radio-selected Sample
We present J-, H-, and K-band images and low-resolution K-band spectraof the 20 most luminous starburst galaxies from the survey of Condon,Frayer, & Broderick. Optical rotation curves are also shown for 10of these galaxies. Near-infrared colors, optical depths, CO indices, anddynamical masses are calculated. The near-infrared colors of thestarburst nuclei are significantly redder than those observed in"normal" galaxies. Together, the Brγ and radio fluxes availablefor five of the galaxies imply that the starbursts are heavily obscured;an average extinction of A_V_~ 25 is derived. Strong CO absorptionfeatures indicate that late-type evolved stars are present in many ofthe starbursts. The average dynamical mass of the starburst region isfound to be (1.0 +/- 0.4) x 10^9^ M_sun_.
| Determination of effective temperatures for an extended sample of dwarfs and subdwarfs (F0-K5).
We have applied the InfraRed Flux Method (IRFM) to a sample of 475dwarfs and subdwarfs in order to derive their effective temperatureswith a mean accuracy of about 1.5%. We have used the new homogeneousgrid of theoretical model atmosphere flux distributions developed byKurucz (1991, 1993) for the application of the IRFM. The atmosphericparameters of the stars cover, roughly, the ranges:3500K<=T_eff_<=8000K -3.5<=[Fe/H]<=+0.53.5<=log(g)<=5. The monocromatic infrared fluxes at the continuum,and the bolometric fluxes are derived using recent results, whichsatisfy the accuracy requeriments of the work. Photometric calibrationshave been revised and applied to estimate metallicities, although directspectroscopic determinations were preferred when available. The adoptedinfrared absolute flux calibration, based on direct optical measurementsof angular stellar diameters, sets the effective temperatures determinedusing the IRFM on the same scale than those obtained by direct methods.We derive three temperatures, T_J_, T_H_ and T_K_, for each star usingthe monochromatic fluxes at different infrared wavelengths in thephotometric bands J, H, and K. They show good consistency over 4000 K,and no trend with wavelength may be appreciated. We provide a detaileddescription of the steps followed for the application of the IRFM, aswell as the sources of the errors associated to the different inputs ofthe method, and their transmission into the final temperatures. We alsoprovide comparison with previous works.
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משמש של הקבוצה הבאה
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | כלבי ציד |
| התרוממות ימנית: | 12h09m27.80s |
| סירוב: | +38°37'54.6" |
| גודל גלוי: | 7.367 |
| מרחק: | 116.822 פארסק |
| תנועה נכונה: | -32.8 |
| תנועה נכונה: | -60.9 |
| B-T magnitude: | 7.735 |
| V-T magnitude: | 7.398 |
קטלוגים וכינוים:
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